//===-- lib/Semantics/check-declarations.cpp ------------------------------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//

// Static declaration checking

#include "check-declarations.h"
#include "definable.h"
#include "pointer-assignment.h"
#include "flang/Evaluate/check-expression.h"
#include "flang/Evaluate/fold.h"
#include "flang/Evaluate/tools.h"
#include "flang/Parser/characters.h"
#include "flang/Semantics/scope.h"
#include "flang/Semantics/semantics.h"
#include "flang/Semantics/symbol.h"
#include "flang/Semantics/tools.h"
#include "flang/Semantics/type.h"
#include <algorithm>
#include <map>
#include <string>

namespace Fortran::semantics {

namespace characteristics = evaluate::characteristics;
using characteristics::DummyArgument;
using characteristics::DummyDataObject;
using characteristics::DummyProcedure;
using characteristics::FunctionResult;
using characteristics::Procedure;

class DistinguishabilityHelper;

class CheckHelper {
public:
  explicit CheckHelper(SemanticsContext &c) : context_{c} {}

  SemanticsContext &context() { return context_; }
  void Check() { Check(context_.globalScope()); }
  void Check(const ParamValue &, bool canBeAssumed);
  void Check(const Bound &bound) {
    CheckSpecExpr(bound.GetExplicit(), /*forElementalFunctionResult=*/false);
  }
  void Check(const ShapeSpec &spec) {
    Check(spec.lbound());
    Check(spec.ubound());
  }
  void Check(const ArraySpec &);
  void Check(const DeclTypeSpec &, bool canHaveAssumedTypeParameters);
  void Check(const Symbol &);
  void CheckCommonBlock(const Symbol &);
  void Check(const Scope &);
  const Procedure *Characterize(const Symbol &);

private:
  template <typename A>
  void CheckSpecExpr(const A &x, bool forElementalFunctionResult) {
    evaluate::CheckSpecificationExpr(
        x, DEREF(scope_), foldingContext_, forElementalFunctionResult);
  }
  void CheckValue(const Symbol &, const DerivedTypeSpec *);
  void CheckVolatile(const Symbol &, const DerivedTypeSpec *);
  void CheckContiguous(const Symbol &);
  void CheckPointer(const Symbol &);
  void CheckPassArg(
      const Symbol &proc, const Symbol *interface, const WithPassArg &);
  void CheckProcBinding(const Symbol &, const ProcBindingDetails &);
  void CheckObjectEntity(const Symbol &, const ObjectEntityDetails &);
  void CheckPointerInitialization(const Symbol &);
  void CheckArraySpec(const Symbol &, const ArraySpec &);
  void CheckProcEntity(const Symbol &, const ProcEntityDetails &);
  void CheckSubprogram(const Symbol &, const SubprogramDetails &);
  void CheckExternal(const Symbol &);
  void CheckAssumedTypeEntity(const Symbol &, const ObjectEntityDetails &);
  void CheckDerivedType(const Symbol &, const DerivedTypeDetails &);
  bool CheckFinal(
      const Symbol &subroutine, SourceName, const Symbol &derivedType);
  bool CheckDistinguishableFinals(const Symbol &f1, SourceName f1name,
      const Symbol &f2, SourceName f2name, const Symbol &derivedType);
  void CheckGeneric(const Symbol &, const GenericDetails &);
  void CheckHostAssoc(const Symbol &, const HostAssocDetails &);
  bool CheckDefinedOperator(
      SourceName, GenericKind, const Symbol &, const Procedure &);
  std::optional<parser::MessageFixedText> CheckNumberOfArgs(
      const GenericKind &, std::size_t);
  bool CheckDefinedOperatorArg(
      const SourceName &, const Symbol &, const Procedure &, std::size_t);
  bool CheckDefinedAssignment(const Symbol &, const Procedure &);
  bool CheckDefinedAssignmentArg(const Symbol &, const DummyArgument &, int);
  void CollectSpecifics(
      DistinguishabilityHelper &, const Symbol &, const GenericDetails &);
  void CheckSpecifics(const Symbol &, const GenericDetails &);
  void CheckEquivalenceSet(const EquivalenceSet &);
  void CheckEquivalenceObject(const EquivalenceObject &);
  void CheckBlockData(const Scope &);
  void CheckGenericOps(const Scope &);
  bool CheckConflicting(const Symbol &, Attr, Attr);
  void WarnMissingFinal(const Symbol &);
  void CheckSymbolType(const Symbol &); // C702
  bool InPure() const {
    return innermostSymbol_ && IsPureProcedure(*innermostSymbol_);
  }
  bool InElemental() const {
    return innermostSymbol_ && IsElementalProcedure(*innermostSymbol_);
  }
  bool InFunction() const {
    return innermostSymbol_ && IsFunction(*innermostSymbol_);
  }
  bool InInterface() const {
    const SubprogramDetails *subp{innermostSymbol_
            ? innermostSymbol_->detailsIf<SubprogramDetails>()
            : nullptr};
    return subp && subp->isInterface();
  }
  template <typename... A>
  parser::Message *SayWithDeclaration(const Symbol &symbol, A &&...x) {
    parser::Message *msg{messages_.Say(std::forward<A>(x)...)};
    if (msg && messages_.at().begin() != symbol.name().begin()) {
      evaluate::AttachDeclaration(*msg, symbol);
    }
    return msg;
  }
  bool InModuleFile() const {
    return FindModuleFileContaining(context_.FindScope(messages_.at())) !=
        nullptr;
  }
  template <typename FeatureOrUsageWarning, typename... A>
  parser::Message *Warn(FeatureOrUsageWarning warning, A &&...x) {
    return messages_.Warn(InModuleFile(), context_.languageFeatures(), warning,
        std::forward<A>(x)...);
  }
  template <typename FeatureOrUsageWarning, typename... A>
  parser::Message *Warn(
      FeatureOrUsageWarning warning, parser::CharBlock source, A &&...x) {
    return messages_.Warn(FindModuleFileContaining(context_.FindScope(source)),
        context_.languageFeatures(), warning, source, std::forward<A>(x)...);
  }
  bool IsResultOkToDiffer(const FunctionResult &);
  void CheckGlobalName(const Symbol &);
  void CheckProcedureAssemblyName(const Symbol &symbol);
  void CheckExplicitSave(const Symbol &);
  parser::Messages WhyNotInteroperableDerivedType(const Symbol &);
  parser::Messages WhyNotInteroperableObject(const Symbol &,
      bool allowNonInteroperableType = false, bool forCommonBlock = false);
  parser::Messages WhyNotInteroperableFunctionResult(const Symbol &);
  parser::Messages WhyNotInteroperableProcedure(const Symbol &, bool isError);
  void CheckBindC(const Symbol &);
  // Check functions for defined I/O procedures
  void CheckDefinedIoProc(
      const Symbol &, const GenericDetails &, common::DefinedIo);
  bool CheckDioDummyIsData(const Symbol &, const Symbol *, std::size_t);
  void CheckDioDummyIsDerived(
      const Symbol &, const Symbol &, common::DefinedIo ioKind, const Symbol &);
  void CheckDioDummyIsDefaultInteger(const Symbol &, const Symbol &);
  void CheckDioDummyIsScalar(const Symbol &, const Symbol &);
  void CheckDioDummyAttrs(const Symbol &, const Symbol &, Attr);
  void CheckDioDtvArg(const Symbol &proc, const Symbol &subp, const Symbol *arg,
      common::DefinedIo, const Symbol &generic);
  void CheckGenericVsIntrinsic(const Symbol &, const GenericDetails &);
  void CheckDefaultIntegerArg(const Symbol &, const Symbol *, Attr);
  void CheckDioAssumedLenCharacterArg(
      const Symbol &, const Symbol *, std::size_t, Attr);
  void CheckDioVlistArg(const Symbol &, const Symbol *, std::size_t);
  void CheckDioArgCount(const Symbol &, common::DefinedIo ioKind, std::size_t);
  struct TypeWithDefinedIo {
    const DerivedTypeSpec &type;
    common::DefinedIo ioKind;
    const Symbol &proc;
    const Symbol &generic;
  };
  void CheckAlreadySeenDefinedIo(const DerivedTypeSpec &, common::DefinedIo,
      const Symbol &, const Symbol &generic);
  void CheckModuleProcedureDef(const Symbol &);

  SemanticsContext &context_;
  evaluate::FoldingContext &foldingContext_{context_.foldingContext()};
  parser::ContextualMessages &messages_{foldingContext_.messages()};
  const Scope *scope_{nullptr};
  bool scopeIsUninstantiatedPDT_{false};
  // This symbol is the one attached to the innermost enclosing scope
  // that has a symbol.
  const Symbol *innermostSymbol_{nullptr};
  // Cache of calls to Procedure::Characterize(Symbol)
  std::map<SymbolRef, std::optional<Procedure>, SymbolAddressCompare>
      characterizeCache_;
  // Collection of module procedure symbols with non-BIND(C)
  // global names, qualified by their module.
  std::map<std::pair<SourceName, const Symbol *>, SymbolRef> moduleProcs_;
  // Collection of symbols with global names, BIND(C) or otherwise
  std::map<std::string, SymbolRef> globalNames_;
  // Collection of external procedures without global definitions
  std::map<std::string, SymbolRef> externalNames_;
  // Collection of target dependent assembly names of external and BIND(C)
  // procedures.
  std::map<std::string, SymbolRef> procedureAssemblyNames_;
  // Derived types that have been examined by WhyNotInteroperable_XXX
  UnorderedSymbolSet examinedByWhyNotInteroperable_;
};

class DistinguishabilityHelper {
public:
  DistinguishabilityHelper(SemanticsContext &context) : context_{context} {}
  void Add(const Symbol &, GenericKind, const Symbol &, const Procedure &);
  void Check(const Scope &);

private:
  void SayNotDistinguishable(const Scope &, const SourceName &, GenericKind,
      const Symbol &, const Symbol &, bool isHardConflict);
  void AttachDeclaration(parser::Message &, const Scope &, const Symbol &);

  SemanticsContext &context_;
  struct ProcedureInfo {
    GenericKind kind;
    const Procedure &procedure;
  };
  std::map<SourceName, std::map<const Symbol *, ProcedureInfo>>
      nameToSpecifics_;
};

void CheckHelper::Check(const ParamValue &value, bool canBeAssumed) {
  if (value.isAssumed()) {
    if (!canBeAssumed) { // C795, C721, C726
      messages_.Say(
          "An assumed (*) type parameter may be used only for a (non-statement function) dummy argument, associate name, character named constant, or external function result"_err_en_US);
    }
  } else {
    CheckSpecExpr(value.GetExplicit(), /*forElementalFunctionResult=*/false);
  }
}

void CheckHelper::Check(const ArraySpec &shape) {
  for (const auto &spec : shape) {
    Check(spec);
  }
}

void CheckHelper::Check(
    const DeclTypeSpec &type, bool canHaveAssumedTypeParameters) {
  if (type.category() == DeclTypeSpec::Character) {
    Check(type.characterTypeSpec().length(), canHaveAssumedTypeParameters);
  } else if (const DerivedTypeSpec *derived{type.AsDerived()}) {
    for (auto &parm : derived->parameters()) {
      Check(parm.second, canHaveAssumedTypeParameters);
    }
  }
}

static bool IsBlockData(const Scope &scope) {
  return scope.kind() == Scope::Kind::BlockData;
}

static bool IsBlockData(const Symbol &symbol) {
  return symbol.scope() && IsBlockData(*symbol.scope());
}

void CheckHelper::Check(const Symbol &symbol) {
  if (symbol.has<UseErrorDetails>()) {
    return;
  }
  if (symbol.name().size() > common::maxNameLen &&
      &symbol == &symbol.GetUltimate()) {
    Warn(common::LanguageFeature::LongNames, symbol.name(),
        "%s has length %d, which is greater than the maximum name length %d"_port_en_US,
        symbol.name(), symbol.name().size(), common::maxNameLen);
  }
  if (context_.HasError(symbol)) {
    return;
  }
  auto restorer{messages_.SetLocation(symbol.name())};
  context_.set_location(symbol.name());
  const DeclTypeSpec *type{symbol.GetType()};
  const DerivedTypeSpec *derived{type ? type->AsDerived() : nullptr};
  bool isDone{false};
  common::visit(
      common::visitors{
          [&](const UseDetails &x) { isDone = true; },
          [&](const HostAssocDetails &x) {
            CheckHostAssoc(symbol, x);
            isDone = true;
          },
          [&](const ProcBindingDetails &x) {
            CheckProcBinding(symbol, x);
            isDone = true;
          },
          [&](const ObjectEntityDetails &x) { CheckObjectEntity(symbol, x); },
          [&](const ProcEntityDetails &x) { CheckProcEntity(symbol, x); },
          [&](const SubprogramDetails &x) { CheckSubprogram(symbol, x); },
          [&](const DerivedTypeDetails &x) { CheckDerivedType(symbol, x); },
          [&](const GenericDetails &x) { CheckGeneric(symbol, x); },
          [](const auto &) {},
      },
      symbol.details());
  if (symbol.attrs().test(Attr::VOLATILE)) {
    CheckVolatile(symbol, derived);
  }
  if (symbol.attrs().test(Attr::BIND_C)) {
    CheckBindC(symbol);
  }
  if (symbol.attrs().test(Attr::SAVE) &&
      !symbol.implicitAttrs().test(Attr::SAVE)) {
    CheckExplicitSave(symbol);
  }
  if (symbol.attrs().test(Attr::CONTIGUOUS)) {
    CheckContiguous(symbol);
  }
  CheckGlobalName(symbol);
  CheckProcedureAssemblyName(symbol);
  if (symbol.attrs().test(Attr::ASYNCHRONOUS) &&
      !evaluate::IsVariable(symbol)) {
    messages_.Say(
        "An entity may not have the ASYNCHRONOUS attribute unless it is a variable"_err_en_US);
  }
  if (symbol.attrs().HasAny({Attr::INTENT_IN, Attr::INTENT_INOUT,
          Attr::INTENT_OUT, Attr::OPTIONAL, Attr::VALUE}) &&
      !IsDummy(symbol)) {
    if (context_.IsEnabled(
            common::LanguageFeature::IgnoreIrrelevantAttributes)) {
      Warn(common::LanguageFeature::IgnoreIrrelevantAttributes,
          "Only a dummy argument should have an INTENT, VALUE, or OPTIONAL attribute"_warn_en_US);
    } else {
      messages_.Say(
          "Only a dummy argument may have an INTENT, VALUE, or OPTIONAL attribute"_err_en_US);
    }
  } else if (symbol.attrs().test(Attr::VALUE)) {
    CheckValue(symbol, derived);
  }

  if (isDone) {
    return; // following checks do not apply
  }

  if (symbol.attrs().test(Attr::PROTECTED)) {
    if (symbol.owner().kind() != Scope::Kind::Module) { // C854
      messages_.Say(
          "A PROTECTED entity must be in the specification part of a module"_err_en_US);
    }
    if (!evaluate::IsVariable(symbol) && !IsProcedurePointer(symbol)) { // C855
      messages_.Say(
          "A PROTECTED entity must be a variable or pointer"_err_en_US);
    }
    if (FindCommonBlockContaining(symbol)) { // C856
      messages_.Say(
          "A PROTECTED entity may not be in a common block"_err_en_US);
    }
  }
  if (IsPointer(symbol)) {
    CheckPointer(symbol);
  }
  if (InPure()) {
    if (InInterface()) {
      // Declarations in interface definitions "have no effect" if they
      // are not pertinent to the characteristics of the procedure.
      // Restrictions on entities in pure procedure interfaces don't need
      // enforcement.
    } else if (symbol.has<AssocEntityDetails>() ||
        FindCommonBlockContaining(symbol)) {
      // can look like they have SAVE but are fine in PURE
    } else if (IsSaved(symbol)) {
      if (IsInitialized(symbol)) {
        messages_.Say(
            "A pure subprogram may not initialize a variable"_err_en_US);
      } else {
        messages_.Say(
            "A pure subprogram may not have a variable with the SAVE attribute"_err_en_US);
      }
    }
    if (symbol.attrs().test(Attr::VOLATILE) &&
        (IsDummy(symbol) || !InInterface())) {
      messages_.Say(
          "A pure subprogram may not have a variable with the VOLATILE attribute"_err_en_US);
    }
    if (innermostSymbol_ && innermostSymbol_->name() == "__builtin_c_funloc") {
      // The intrinsic procedure C_FUNLOC() gets a pass on this check.
    } else if (IsProcedure(symbol) && !IsPureProcedure(symbol) &&
        IsDummy(symbol)) {
      messages_.Say(
          "A dummy procedure of a pure subprogram must be pure"_err_en_US);
    }
  }
  const auto *object{symbol.detailsIf<ObjectEntityDetails>()};
  if (type) { // Section 7.2, paragraph 7; C795
    bool isChar{type->category() == DeclTypeSpec::Character};
    bool canHaveAssumedParameter{(isChar && IsNamedConstant(symbol)) ||
        (IsAssumedLengthCharacter(symbol) && // C722
            (IsExternal(symbol) ||
                ClassifyProcedure(symbol) ==
                    ProcedureDefinitionClass::Dummy)) ||
        symbol.test(Symbol::Flag::ParentComp)};
    if (!IsStmtFunctionDummy(symbol)) { // C726
      if (object) {
        canHaveAssumedParameter |= object->isDummy() ||
            (isChar && object->isFuncResult()) ||
            IsStmtFunctionResult(symbol); // Avoids multiple messages
      } else {
        canHaveAssumedParameter |= symbol.has<AssocEntityDetails>();
      }
    }
    if (IsProcedurePointer(symbol) && symbol.HasExplicitInterface()) {
      // Don't check function result types here
    } else {
      Check(*type, canHaveAssumedParameter);
    }
    if (InFunction() && IsFunctionResult(symbol)) {
      if (InPure()) {
        if (type->IsPolymorphic() && IsAllocatable(symbol)) { // C1585
          messages_.Say(
              "Result of pure function may not be both polymorphic and ALLOCATABLE"_err_en_US);
        }
        if (derived) {
          // These cases would be caught be the general validation of local
          // variables in a pure context, but these messages are more specific.
          if (HasImpureFinal(symbol)) { // C1584
            messages_.Say(
                "Result of pure function may not have an impure FINAL subroutine"_err_en_US);
          }
          if (auto bad{
                  FindPolymorphicAllocatablePotentialComponent(*derived)}) {
            SayWithDeclaration(*bad,
                "Result of pure function may not have polymorphic ALLOCATABLE potential component '%s'"_err_en_US,
                bad.BuildResultDesignatorName());
          }
        }
      }
      if (InElemental() && isChar) { // F'2023 C15121
        CheckSpecExpr(type->characterTypeSpec().length().GetExplicit(),
            /*forElementalFunctionResult=*/true);
        // TODO: check PDT LEN parameters
      }
    }
  }
  if (IsAssumedLengthCharacter(symbol) && IsFunction(symbol)) { // C723
    if (symbol.attrs().test(Attr::RECURSIVE)) {
      messages_.Say(
          "An assumed-length CHARACTER(*) function cannot be RECURSIVE"_err_en_US);
    }
    if (symbol.Rank() > 0) {
      messages_.Say(
          "An assumed-length CHARACTER(*) function cannot return an array"_err_en_US);
    }
    if (!IsStmtFunction(symbol)) {
      if (IsElementalProcedure(symbol)) {
        messages_.Say(
            "An assumed-length CHARACTER(*) function cannot be ELEMENTAL"_err_en_US);
      } else if (IsPureProcedure(symbol)) {
        messages_.Say(
            "An assumed-length CHARACTER(*) function cannot be PURE"_err_en_US);
      }
    }
    if (const Symbol *result{FindFunctionResult(symbol)}) {
      if (IsPointer(*result)) {
        messages_.Say(
            "An assumed-length CHARACTER(*) function cannot return a POINTER"_err_en_US);
      }
    }
    if (IsProcedurePointer(symbol) && IsDummy(symbol)) {
      Warn(common::UsageWarning::Portability,
          "A dummy procedure pointer should not have assumed-length CHARACTER(*) result type"_port_en_US);
      // The non-dummy case is a hard error that's caught elsewhere.
    }
  }
  if (IsDummy(symbol)) {
    if (IsNamedConstant(symbol)) {
      messages_.Say(
          "A dummy argument may not also be a named constant"_err_en_US);
    }
  } else if (IsFunctionResult(symbol)) {
    if (IsNamedConstant(symbol)) {
      messages_.Say(
          "A function result may not also be a named constant"_err_en_US);
    }
    if (!IsProcedurePointer(symbol) && IsProcedure(symbol)) {
      messages_.Say(
          "A function result may not be a procedure unless it is a procedure pointer"_err_en_US);
    }
  }
  if (IsAutomatic(symbol)) {
    if (const Symbol * common{FindCommonBlockContaining(symbol)}) {
      messages_.Say(
          "Automatic data object '%s' may not appear in COMMON block /%s/"_err_en_US,
          symbol.name(), common->name());
    } else if (symbol.owner().IsModule()) {
      messages_.Say(
          "Automatic data object '%s' may not appear in a module"_err_en_US,
          symbol.name());
    } else if (IsBlockData(symbol.owner())) {
      messages_.Say(
          "Automatic data object '%s' may not appear in a BLOCK DATA subprogram"_err_en_US,
          symbol.name());
    } else if (symbol.owner().kind() == Scope::Kind::MainProgram) {
      if (context_.IsEnabled(common::LanguageFeature::AutomaticInMainProgram)) {
        Warn(common::LanguageFeature::AutomaticInMainProgram,
            "Automatic data object '%s' should not appear in the specification part of a main program"_port_en_US,
            symbol.name());
      } else {
        messages_.Say(
            "Automatic data object '%s' may not appear in the specification part of a main program"_err_en_US,
            symbol.name());
      }
    }
  }
  if (IsProcedure(symbol)) {
    if (IsAllocatable(symbol)) {
      messages_.Say(
          "Procedure '%s' may not be ALLOCATABLE"_err_en_US, symbol.name());
    }
    if (!symbol.HasExplicitInterface() && symbol.Rank() > 0) {
      messages_.Say(
          "Procedure '%s' may not be an array without an explicit interface"_err_en_US,
          symbol.name());
    }
  }
}

void CheckHelper::CheckCommonBlock(const Symbol &symbol) {
  CheckGlobalName(symbol);
  const auto &common{symbol.get<CommonBlockDetails>()};
  SourceName location{symbol.name()};
  if (location.empty()) {
    location = common.sourceLocation();
  }
  bool isBindCCommon{symbol.attrs().test(Attr::BIND_C)};
  if (isBindCCommon) {
    CheckBindC(symbol);
  }
  for (auto ref : symbol.get<CommonBlockDetails>().objects()) {
    auto restorer{
        messages_.SetLocation(location.empty() ? ref->name() : location)};
    if (isBindCCommon && ref->has<ObjectEntityDetails>()) {
      if (auto msgs{WhyNotInteroperableObject(*ref,
              /*allowInteroperableType=*/false, /*forCommonBlock=*/true)};
          !msgs.empty()) {
        parser::Message &reason{msgs.messages().front()};
        parser::Message *msg{nullptr};
        if (reason.IsFatal()) {
          msg = messages_.Say(
              "'%s' may not be a member of BIND(C) COMMON block /%s/"_err_en_US,
              ref->name(), symbol.name());
        } else {
          msg = messages_.Say(
              "'%s' should not be a member of BIND(C) COMMON block /%s/"_warn_en_US,
              ref->name(), symbol.name());
        }
        if (msg) {
          msg = &msg->Attach(
              std::move(reason.set_severity(parser::Severity::Because)));
        }
        evaluate::AttachDeclaration(msg, *ref);
      }
    }
    if (ref->test(Symbol::Flag::CrayPointee)) {
      evaluate::AttachDeclaration(
          messages_.Say(
              "Cray pointee '%s' may not be a member of COMMON block /%s/"_err_en_US,
              ref->name(), symbol.name()),
          *ref);
    }
    if (IsAllocatable(*ref)) {
      evaluate::AttachDeclaration(
          messages_.Say(
              "ALLOCATABLE object '%s' may not appear in COMMON block /%s/"_err_en_US,
              ref->name(), symbol.name()),
          *ref);
    }
    if (ref->attrs().test(Attr::BIND_C)) {
      evaluate::AttachDeclaration(
          messages_.Say(
              "BIND(C) object '%s' may not appear in COMMON block /%s/"_err_en_US,
              ref->name(), symbol.name()),
          *ref);
    }
    if (IsNamedConstant(*ref)) {
      evaluate::AttachDeclaration(
          messages_.Say(
              "Named constant '%s' may not appear in COMMON block /%s/"_err_en_US,
              ref->name(), symbol.name()),
          *ref);
    }
    if (IsDummy(*ref)) {
      evaluate::AttachDeclaration(
          messages_.Say(
              "Dummy argument '%s' may not appear in COMMON block /%s/"_err_en_US,
              ref->name(), symbol.name()),
          *ref);
    }
    if (ref->IsFuncResult()) {
      evaluate::AttachDeclaration(
          messages_.Say(
              "Function result '%s' may not appear in COMMON block /%s/"_err_en_US,
              ref->name(), symbol.name()),
          *ref);
    }
    if (const auto *type{ref->GetType()}) {
      if (type->category() == DeclTypeSpec::ClassStar) {
        evaluate::AttachDeclaration(
            messages_.Say(
                "Unlimited polymorphic pointer '%s' may not appear in COMMON block /%s/"_err_en_US,
                ref->name(), symbol.name()),
            *ref);
      } else if (const auto *derived{type->AsDerived()}) {
        if (!IsSequenceOrBindCType(derived)) {
          evaluate::AttachDeclaration(
              evaluate::AttachDeclaration(
                  messages_.Say(
                      "Object '%s' whose derived type '%s' is neither SEQUENCE nor BIND(C) may not appear in COMMON block /%s/"_err_en_US,
                      ref->name(), derived->name(), symbol.name()),
                  derived->typeSymbol()),
              *ref);
        } else if (auto componentPath{
                       derived->ComponentWithDefaultInitialization()}) {
          evaluate::AttachDeclaration(
              evaluate::AttachDeclaration(
                  messages_.Say(
                      "COMMON block /%s/ may not have the member '%s' whose derived type '%s' has a component '%s' that is ALLOCATABLE or has default initialization"_err_en_US,
                      symbol.name(), ref->name(), derived->name(),
                      *componentPath),
                  derived->typeSymbol()),
              *ref);
        }
      }
    }
  }
}

// C859, C860
void CheckHelper::CheckExplicitSave(const Symbol &symbol) {
  const Symbol &ultimate{symbol.GetUltimate()};
  if (ultimate.test(Symbol::Flag::InDataStmt)) {
    // checked elsewhere
  } else if (symbol.has<UseDetails>()) {
    messages_.Say(
        "The USE-associated name '%s' may not have an explicit SAVE attribute"_err_en_US,
        symbol.name());
  } else if (IsDummy(ultimate)) {
    messages_.Say(
        "The dummy argument '%s' may not have an explicit SAVE attribute"_err_en_US,
        symbol.name());
  } else if (IsFunctionResult(ultimate)) {
    messages_.Say(
        "The function result variable '%s' may not have an explicit SAVE attribute"_err_en_US,
        symbol.name());
  } else if (const Symbol * common{FindCommonBlockContaining(ultimate)}) {
    messages_.Say(
        "The entity '%s' in COMMON block /%s/ may not have an explicit SAVE attribute"_err_en_US,
        symbol.name(), common->name());
  } else if (IsAutomatic(ultimate)) {
    messages_.Say(
        "The automatic object '%s' may not have an explicit SAVE attribute"_err_en_US,
        symbol.name());
  } else if (!evaluate::IsVariable(ultimate) && !IsProcedurePointer(ultimate)) {
    messages_.Say(
        "The entity '%s' with an explicit SAVE attribute must be a variable, procedure pointer, or COMMON block"_err_en_US,
        symbol.name());
  }
}

void CheckHelper::CheckValue(
    const Symbol &symbol, const DerivedTypeSpec *derived) { // C863 - C865
  if (IsProcedure(symbol)) {
    messages_.Say(
        "VALUE attribute may apply only to a dummy data object"_err_en_US);
    return; // don't pile on
  }
  if (IsAssumedSizeArray(symbol)) {
    messages_.Say(
        "VALUE attribute may not apply to an assumed-size array"_err_en_US);
  }
  if (evaluate::IsCoarray(symbol)) {
    messages_.Say("VALUE attribute may not apply to a coarray"_err_en_US);
  }
  if (IsAllocatable(symbol)) {
    messages_.Say("VALUE attribute may not apply to an ALLOCATABLE"_err_en_US);
  } else if (IsPointer(symbol)) {
    messages_.Say("VALUE attribute may not apply to a POINTER"_err_en_US);
  }
  if (IsIntentInOut(symbol)) {
    messages_.Say(
        "VALUE attribute may not apply to an INTENT(IN OUT) argument"_err_en_US);
  } else if (IsIntentOut(symbol)) {
    messages_.Say(
        "VALUE attribute may not apply to an INTENT(OUT) argument"_err_en_US);
  }
  if (symbol.attrs().test(Attr::VOLATILE)) {
    messages_.Say("VALUE attribute may not apply to a VOLATILE"_err_en_US);
  }
  if (innermostSymbol_ && IsBindCProcedure(*innermostSymbol_)) {
    if (IsOptional(symbol)) {
      messages_.Say(
          "VALUE attribute may not apply to an OPTIONAL in a BIND(C) procedure"_err_en_US);
    }
    if (symbol.Rank() > 0) {
      messages_.Say(
          "VALUE attribute may not apply to an array in a BIND(C) procedure"_err_en_US);
    }
  }
  if (derived) {
    if (FindCoarrayUltimateComponent(*derived)) {
      messages_.Say(
          "VALUE attribute may not apply to a type with a coarray ultimate component"_err_en_US);
    }
  }
  if (IsAssumedRank(symbol)) {
    messages_.Say(
        "VALUE attribute may not apply to an assumed-rank array"_err_en_US);
  }
  if (IsAssumedLengthCharacter(symbol)) {
    // F'2008 feature not widely implemented
    Warn(common::UsageWarning::Portability,
        "VALUE attribute on assumed-length CHARACTER may not be portable"_port_en_US);
  }
}

void CheckHelper::CheckAssumedTypeEntity( // C709
    const Symbol &symbol, const ObjectEntityDetails &details) {
  if (const DeclTypeSpec *type{symbol.GetType()};
      type && type->category() == DeclTypeSpec::TypeStar) {
    if (!IsDummy(symbol)) {
      messages_.Say(
          "Assumed-type entity '%s' must be a dummy argument"_err_en_US,
          symbol.name());
    } else {
      if (symbol.attrs().test(Attr::ALLOCATABLE)) {
        messages_.Say("Assumed-type argument '%s' cannot have the ALLOCATABLE"
                      " attribute"_err_en_US,
            symbol.name());
      }
      if (symbol.attrs().test(Attr::POINTER)) {
        messages_.Say("Assumed-type argument '%s' cannot have the POINTER"
                      " attribute"_err_en_US,
            symbol.name());
      }
      if (symbol.attrs().test(Attr::VALUE)) {
        messages_.Say("Assumed-type argument '%s' cannot have the VALUE"
                      " attribute"_err_en_US,
            symbol.name());
      }
      if (symbol.attrs().test(Attr::INTENT_OUT)) {
        messages_.Say(
            "Assumed-type argument '%s' cannot be INTENT(OUT)"_err_en_US,
            symbol.name());
      }
      if (evaluate::IsCoarray(symbol)) {
        messages_.Say(
            "Assumed-type argument '%s' cannot be a coarray"_err_en_US,
            symbol.name());
      }
      if (details.IsArray() && details.shape().IsExplicitShape()) {
        messages_.Say("Assumed-type array argument '%s' must be assumed shape,"
                      " assumed size, or assumed rank"_err_en_US,
            symbol.name());
      }
    }
  }
}

void CheckHelper::CheckObjectEntity(
    const Symbol &symbol, const ObjectEntityDetails &details) {
  CheckSymbolType(symbol);
  CheckArraySpec(symbol, details.shape());
  CheckConflicting(symbol, Attr::ALLOCATABLE, Attr::PARAMETER);
  CheckConflicting(symbol, Attr::ASYNCHRONOUS, Attr::PARAMETER);
  CheckConflicting(symbol, Attr::SAVE, Attr::PARAMETER);
  CheckConflicting(symbol, Attr::TARGET, Attr::PARAMETER);
  CheckConflicting(symbol, Attr::VOLATILE, Attr::PARAMETER);
  Check(details.shape());
  Check(details.coshape());
  if (details.shape().Rank() > common::maxRank) {
    messages_.Say(
        "'%s' has rank %d, which is greater than the maximum supported rank %d"_err_en_US,
        symbol.name(), details.shape().Rank(), common::maxRank);
  } else if (details.shape().Rank() + details.coshape().Rank() >
      common::maxRank) {
    messages_.Say(
        "'%s' has rank %d and corank %d, whose sum is greater than the maximum supported rank %d"_err_en_US,
        symbol.name(), details.shape().Rank(), details.coshape().Rank(),
        common::maxRank);
  }
  CheckAssumedTypeEntity(symbol, details);
  WarnMissingFinal(symbol);
  const DeclTypeSpec *type{details.type()};
  const DerivedTypeSpec *derived{type ? type->AsDerived() : nullptr};
  bool isComponent{symbol.owner().IsDerivedType()};
  const Symbol *commonBlock{FindCommonBlockContaining(symbol)};
  bool isLocalVariable{!commonBlock && !isComponent && !details.isDummy() &&
      symbol.owner().kind() != Scope::Kind::OtherConstruct};
  if (int corank{evaluate::GetCorank(symbol)}; corank > 0) { // it's a coarray
    bool isDeferredCoshape{details.coshape().CanBeDeferredShape()};
    if (IsAllocatable(symbol)) {
      if (!isDeferredCoshape) { // C827
        messages_.Say("'%s' is an ALLOCATABLE coarray and must have a deferred"
                      " coshape"_err_en_US,
            symbol.name());
      }
    } else if (isComponent) { // C746
      std::string deferredMsg{
          isDeferredCoshape ? "" : " and have a deferred coshape"};
      messages_.Say("Component '%s' is a coarray and must have the ALLOCATABLE"
                    " attribute%s"_err_en_US,
          symbol.name(), deferredMsg);
    } else {
      if (!details.coshape().CanBeAssumedSize()) { // C828
        messages_.Say(
            "'%s' is a non-ALLOCATABLE coarray and must have an explicit coshape"_err_en_US,
            symbol.name());
      }
    }
    if (IsBadCoarrayType(derived)) { // C747 & C824
      messages_.Say(
          "Coarray '%s' may not have type TEAM_TYPE, C_PTR, or C_FUNPTR"_err_en_US,
          symbol.name());
    }
    if (IsAssumedRank(symbol)) {
      messages_.Say("Coarray '%s' may not be an assumed-rank array"_err_en_US,
          symbol.name());
    }
    if (IsNamedConstant(symbol)) {
      messages_.Say(
          "Coarray '%s' may not be a named constant"_err_en_US, symbol.name());
    }
    if (IsFunctionResult(symbol)) {
      messages_.Say("Function result may not be a coarray"_err_en_US);
    } else if (commonBlock) {
      messages_.Say("Coarray '%s' may not be in COMMON block '/%s/'"_err_en_US,
          symbol.name(), commonBlock->name());
    } else if (isLocalVariable && !IsAllocatableOrPointer(symbol) &&
        !IsSaved(symbol)) {
      messages_.Say(
          "Local coarray must have the SAVE or ALLOCATABLE attribute"_err_en_US);
    }
    for (int j{0}; j < corank; ++j) {
      if (auto lcbv{evaluate::ToInt64(evaluate::Fold(
              context().foldingContext(), evaluate::GetLCOBOUND(symbol, j)))}) {
        if (auto ucbv{
                evaluate::ToInt64(evaluate::Fold(context().foldingContext(),
                    evaluate::GetUCOBOUND(symbol, j)))}) {
          if (ucbv < lcbv) {
            messages_.Say(
                "Cobounds %jd:%jd of codimension %d produce an empty coarray"_err_en_US,
                std::intmax_t{*lcbv}, std::intmax_t{*ucbv}, j + 1);
          }
        }
      }
    }
  } else { // not a coarray
    if (!isComponent && !IsPointer(symbol) && derived) {
      if (IsEventTypeOrLockType(derived)) {
        messages_.Say(
            "Variable '%s' with EVENT_TYPE or LOCK_TYPE must be a coarray"_err_en_US,
            symbol.name());
      } else if (auto component{FindEventOrLockPotentialComponent(
                     *derived, /*ignoreCoarrays=*/true)}) {
        messages_.Say(
            "Variable '%s' with EVENT_TYPE or LOCK_TYPE potential component '%s' must be a coarray"_err_en_US,
            symbol.name(), component.BuildResultDesignatorName());
      } else if (IsNotifyType(derived)) { // C1612
        messages_.Say(
            "Variable '%s' with NOTIFY_TYPE must be a coarray"_err_en_US,
            symbol.name());
      } else if (auto component{FindNotifyPotentialComponent( // C1611
                     *derived, /*ignoreCoarrays=*/true)}) {
        messages_.Say(
            "Variable '%s' with NOTIFY_TYPE potential component '%s' must be a coarray"_err_en_US,
            symbol.name(), component.BuildResultDesignatorName());
      }
    }
  }
  if (details.isDummy()) {
    if (IsIntentOut(symbol)) {
      // Some of these errors would also be caught by the general check
      // for definability of automatically deallocated local variables,
      // but these messages are more specific.
      if (FindUltimateComponent(symbol, [](const Symbol &x) {
            return evaluate::IsCoarray(x) && IsAllocatable(x);
          })) { // C846
        messages_.Say(
            "An INTENT(OUT) dummy argument may not be, or contain, an ALLOCATABLE coarray"_err_en_US);
      }
      if (IsOrContainsEventOrLockComponent(symbol)) { // C847
        messages_.Say(
            "An INTENT(OUT) dummy argument may not be, or contain, EVENT_TYPE or LOCK_TYPE"_err_en_US);
      }
      if (IsOrContainsNotifyComponent(symbol)) { // C1613
        messages_.Say(
            "An INTENT(OUT) dummy argument may not be, or contain, NOTIFY_TYPE"_err_en_US);
      }
      if (IsAssumedSizeArray(symbol)) { // C834
        if (type && type->IsPolymorphic()) {
          messages_.Say(
              "An INTENT(OUT) assumed-size dummy argument array may not be polymorphic"_err_en_US);
        }
        if (derived) {
          if (derived->HasDefaultInitialization()) {
            messages_.Say(
                "An INTENT(OUT) assumed-size dummy argument array may not have a derived type with any default component initialization"_err_en_US);
          }
          if (IsFinalizable(*derived)) {
            messages_.Say(
                "An INTENT(OUT) assumed-size dummy argument array may not be finalizable"_err_en_US);
          }
        }
      }
    }
    if (InPure() && !IsStmtFunction(DEREF(innermostSymbol_)) &&
        !IsPointer(symbol) && !IsIntentIn(symbol) &&
        !symbol.attrs().test(Attr::VALUE)) {
      const char *what{InFunction() ? "function" : "subroutine"};
      bool ok{true};
      if (IsIntentOut(symbol)) {
        if (type && type->IsPolymorphic()) { // C1588
          messages_.Say(
              "An INTENT(OUT) dummy argument of a pure %s may not be polymorphic"_err_en_US,
              what);
          ok = false;
        } else if (derived) {
          if (FindUltimateComponent(*derived, [](const Symbol &x) {
                const DeclTypeSpec *type{x.GetType()};
                return type && type->IsPolymorphic();
              })) { // C1588
            messages_.Say(
                "An INTENT(OUT) dummy argument of a pure %s may not have a polymorphic ultimate component"_err_en_US,
                what);
            ok = false;
          }
          if (HasImpureFinal(symbol)) { // C1587
            messages_.Say(
                "An INTENT(OUT) dummy argument of a pure %s may not have an impure FINAL subroutine"_err_en_US,
                what);
            ok = false;
          }
        }
      } else if (!IsIntentInOut(symbol)) { // C1586
        messages_.Say(
            "non-POINTER dummy argument of pure %s must have INTENT() or VALUE attribute"_err_en_US,
            what);
        ok = false;
      }
      if (ok && InFunction() && !InModuleFile() && !InElemental()) {
        if (context_.IsEnabled(common::LanguageFeature::RelaxedPureDummy)) {
          Warn(common::LanguageFeature::RelaxedPureDummy,
              "non-POINTER dummy argument of pure function should be INTENT(IN) or VALUE"_warn_en_US);
        } else {
          messages_.Say(
              "non-POINTER dummy argument of pure function must be INTENT(IN) or VALUE"_err_en_US);
        }
      }
    }
    if (auto ignoreTKR{GetIgnoreTKR(symbol)}; !ignoreTKR.empty()) {
      const Symbol *ownerSymbol{symbol.owner().symbol()};
      bool inModuleProc{ownerSymbol && IsModuleProcedure(*ownerSymbol)};
      bool inExplicitExternalInterface{
          InInterface() && !IsSeparateModuleProcedureInterface(ownerSymbol)};
      if (!InInterface() && !inModuleProc) {
        messages_.Say(
            "!DIR$ IGNORE_TKR may apply only in an interface or a module procedure"_err_en_US);
      }
      if (ownerSymbol && ownerSymbol->attrs().test(Attr::ELEMENTAL) &&
          details.ignoreTKR().test(common::IgnoreTKR::Rank)) {
        messages_.Say(
            "!DIR$ IGNORE_TKR(R) may not apply in an ELEMENTAL procedure"_err_en_US);
      }
      // Descriptor based dummy args passed with ignore_tkr(c) are allowed
      // to have type/kind/rank differences
      if (IsPassedViaDescriptor(symbol) &&
          !ignoreTKR.test(common::IgnoreTKR::Contiguous)) {
        if (IsAllocatableOrObjectPointer(&symbol) &&
            !ignoreTKR.test(common::IgnoreTKR::Pointer)) {
          if (inExplicitExternalInterface) {
            Warn(common::UsageWarning::IgnoreTKRUsage,
                "!DIR$ IGNORE_TKR should not apply to an allocatable or pointer"_warn_en_US);
          } else {
            messages_.Say(
                "!DIR$ IGNORE_TKR may not apply to an allocatable or pointer"_err_en_US);
          }
        } else if (ignoreTKR.test(common::IgnoreTKR::Rank)) {
          if (ignoreTKR.count() == 1 && IsAssumedRank(symbol)) {
            Warn(common::UsageWarning::IgnoreTKRUsage,
                "!DIR$ IGNORE_TKR(R) is not meaningful for an assumed-rank array"_warn_en_US);
          } else if (inExplicitExternalInterface) {
            Warn(common::UsageWarning::IgnoreTKRUsage,
                "!DIR$ IGNORE_TKR(R) should not apply to a dummy argument passed via descriptor"_warn_en_US);
          } else {
            messages_.Say(
                "!DIR$ IGNORE_TKR(R) may not apply to a dummy argument passed via descriptor"_err_en_US);
          }
        }
      }
    }
  } else if (!details.ignoreTKR().empty()) {
    messages_.Say(
        "!DIR$ IGNORE_TKR directive may apply only to a dummy data argument"_err_en_US);
  }
  if (InElemental()) {
    if (details.isDummy()) { // C15100
      if (details.shape().Rank() > 0) {
        messages_.Say(
            "A dummy argument of an ELEMENTAL procedure must be scalar"_err_en_US);
      }
      if (IsAllocatable(symbol)) {
        messages_.Say(
            "A dummy argument of an ELEMENTAL procedure may not be ALLOCATABLE"_err_en_US);
      }
      if (evaluate::IsCoarray(symbol)) {
        messages_.Say(
            "A dummy argument of an ELEMENTAL procedure may not be a coarray"_err_en_US);
      }
      if (IsPointer(symbol)) {
        messages_.Say(
            "A dummy argument of an ELEMENTAL procedure may not be a POINTER"_err_en_US);
      }
      if (!symbol.attrs().HasAny(Attrs{Attr::VALUE, Attr::INTENT_IN,
              Attr::INTENT_INOUT, Attr::INTENT_OUT})) { // F'2023 C15120
        messages_.Say(
            "A dummy argument of an ELEMENTAL procedure must have an INTENT() or VALUE attribute"_err_en_US);
      }
    } else if (IsFunctionResult(symbol)) { // C15101
      if (details.shape().Rank() > 0) {
        messages_.Say(
            "The result of an ELEMENTAL function must be scalar"_err_en_US);
      }
      if (IsAllocatable(symbol)) {
        messages_.Say(
            "The result of an ELEMENTAL function may not be ALLOCATABLE"_err_en_US);
      }
      if (IsPointer(symbol)) {
        messages_.Say(
            "The result of an ELEMENTAL function may not be a POINTER"_err_en_US);
      }
    }
  }
  if (HasDeclarationInitializer(symbol)) { // C808; ignore DATA initialization
    CheckPointerInitialization(symbol);
    if (IsAutomatic(symbol)) {
      messages_.Say(
          "An automatic variable or component must not be initialized"_err_en_US);
    } else if (IsDummy(symbol)) {
      messages_.Say("A dummy argument must not be initialized"_err_en_US);
    } else if (IsFunctionResult(symbol)) {
      messages_.Say("A function result must not be initialized"_err_en_US);
    } else if (IsInBlankCommon(symbol)) {
      Warn(common::LanguageFeature::InitBlankCommon,
          "A variable in blank COMMON should not be initialized"_port_en_US);
    }
  }
  if (symbol.owner().kind() == Scope::Kind::BlockData) {
    if (IsAllocatable(symbol)) {
      messages_.Say(
          "An ALLOCATABLE variable may not appear in a BLOCK DATA subprogram"_err_en_US);
    } else if (IsInitialized(symbol) && !FindCommonBlockContaining(symbol)) {
      messages_.Say(
          "An initialized variable in BLOCK DATA must be in a COMMON block"_err_en_US);
    }
  }
  if (derived && InPure() && !InInterface() &&
      IsAutomaticallyDestroyed(symbol) &&
      !IsIntentOut(symbol) /*has better messages*/ &&
      !IsFunctionResult(symbol) /*ditto*/) {
    // Check automatically deallocated local variables for possible
    // problems with finalization in PURE.
    if (auto whyNot{WhyNotDefinable(symbol.name(), symbol.owner(),
            {DefinabilityFlag::PotentialDeallocation}, symbol)}) {
      if (auto *msg{messages_.Say(
              "'%s' may not be a local variable in a pure subprogram"_err_en_US,
              symbol.name())}) {
        msg->Attach(std::move(whyNot->set_severity(parser::Severity::Because)));
      }
    }
  }
  if (symbol.attrs().test(Attr::EXTERNAL)) {
    SayWithDeclaration(symbol,
        "'%s' is a data object and may not be EXTERNAL"_err_en_US,
        symbol.name());
  }
  if (symbol.test(Symbol::Flag::CrayPointee)) {
    // NB, IsSaved was too smart here.
    if (details.init()) {
      messages_.Say(
          "Cray pointee '%s' may not be initialized"_err_en_US, symbol.name());
    }
    if (symbol.attrs().test(Attr::SAVE)) {
      messages_.Say(
          "Cray pointee '%s' may not have the SAVE attribute"_err_en_US,
          symbol.name());
    }
  }
  if (derived) {
    bool isUnsavedLocal{
        isLocalVariable && !IsAllocatable(symbol) && !IsSaved(symbol)};
    if (IsFunctionResult(symbol) || IsPointer(symbol) ||
        evaluate::IsCoarray(symbol) || isUnsavedLocal) {
      if (auto badPotential{FindCoarrayPotentialComponent(*derived)}) {
        if (IsFunctionResult(symbol)) { // F'2023 C825
          SayWithDeclaration(*badPotential,
              "Function result '%s' may not have a coarray potential component '%s'"_err_en_US,
              symbol.name(), badPotential.BuildResultDesignatorName());
        } else if (IsPointer(symbol)) { // F'2023 C825
          SayWithDeclaration(*badPotential,
              "Pointer '%s' may not have a coarray potential component '%s'"_err_en_US,
              symbol.name(), badPotential.BuildResultDesignatorName());
        } else if (evaluate::IsCoarray(symbol)) { // F'2023 C825
          SayWithDeclaration(*badPotential,
              "Coarray '%s' may not have a coarray potential component '%s'"_err_en_US,
              symbol.name(), badPotential.BuildResultDesignatorName());
        } else if (isUnsavedLocal) { // F'2023 C826
          SayWithDeclaration(*badPotential,
              "Local variable '%s' without the SAVE or ALLOCATABLE attribute may not have a coarray potential subobject component '%s'"_err_en_US,
              symbol.name(), badPotential.BuildResultDesignatorName());
        } else {
          DIE("caught unexpected bad coarray potential component");
        }
      }
    } else if (isComponent && (IsAllocatable(symbol) || symbol.Rank() > 0)) {
      if (auto badUltimate{FindCoarrayUltimateComponent(*derived)}) {
        // TODO: still an error in F'2023?
        SayWithDeclaration(*badUltimate,
            "Allocatable or array component '%s' may not have a coarray ultimate component '%s'"_err_en_US,
            symbol.name(), badUltimate.BuildResultDesignatorName());
      }
    }
  }

  // Check CUDA attributes and special circumstances of being in device
  // subprograms
  const Scope &progUnit{GetProgramUnitContaining(symbol)};
  const auto *subpDetails{!isComponent && progUnit.symbol()
          ? progUnit.symbol()->detailsIf<SubprogramDetails>()
          : nullptr};
  bool inDeviceSubprogram{IsCUDADeviceContext(&symbol.owner())};
  if (inDeviceSubprogram) {
    if (IsSaved(symbol)) {
      Warn(common::UsageWarning::CUDAUsage,
          "'%s' should not have the SAVE attribute or initialization in a device subprogram"_warn_en_US,
          symbol.name());
    }
    if (IsPointer(symbol)) {
      Warn(common::UsageWarning::CUDAUsage,
          "Pointer '%s' may not be associated in a device subprogram"_warn_en_US,
          symbol.name());
    }
    if (details.isDummy() &&
        details.cudaDataAttr().value_or(common::CUDADataAttr::Device) !=
            common::CUDADataAttr::Device &&
        details.cudaDataAttr().value_or(common::CUDADataAttr::Device) !=
            common::CUDADataAttr::Managed &&
        details.cudaDataAttr().value_or(common::CUDADataAttr::Device) !=
            common::CUDADataAttr::Shared) {
      Warn(common::UsageWarning::CUDAUsage,
          "Dummy argument '%s' may not have ATTRIBUTES(%s) in a device subprogram"_warn_en_US,
          symbol.name(),
          parser::ToUpperCaseLetters(
              common::EnumToString(*details.cudaDataAttr())));
    }
  }
  if (details.cudaDataAttr()) {
    if (auto dyType{evaluate::DynamicType::From(symbol)}) {
      if (dyType->category() != TypeCategory::Derived) {
        if (!IsCUDAIntrinsicType(*dyType)) {
          messages_.Say(
              "'%s' has intrinsic type '%s' that is not available on the device"_err_en_US,
              symbol.name(), dyType->AsFortran());
        }
      }
    }
    auto attr{*details.cudaDataAttr()};
    switch (attr) {
    case common::CUDADataAttr::Value:
      break; // Nothing to check for VALUE attribute
    case common::CUDADataAttr::Constant:
      if (subpDetails && !inDeviceSubprogram) {
        messages_.Say(
            "Object '%s' with ATTRIBUTES(CONSTANT) may not be declared in a host subprogram"_err_en_US,
            symbol.name());
      } else if (IsAllocatableOrPointer(symbol) ||
          symbol.attrs().test(Attr::TARGET)) {
        messages_.Say(
            "Object '%s' with ATTRIBUTES(CONSTANT) may not be allocatable, pointer, or target"_err_en_US,
            symbol.name());
      } else if (auto shape{evaluate::GetShape(foldingContext_, symbol)};
                 !shape ||
                 !evaluate::AsConstantExtents(foldingContext_, *shape)) {
        messages_.Say(
            "Object '%s' with ATTRIBUTES(CONSTANT) must have constant array bounds"_err_en_US,
            symbol.name());
      }
      break;
    case common::CUDADataAttr::Device:
      if (isComponent && !IsAllocatable(symbol) && !IsPointer(symbol)) {
        messages_.Say(
            "Component '%s' with ATTRIBUTES(DEVICE) must also be allocatable or pointer"_err_en_US,
            symbol.name());
      }
      break;
    case common::CUDADataAttr::Managed:
      if (!IsAutomatic(symbol) && !IsAllocatableOrPointer(symbol) &&
          !details.isDummy() && !evaluate::IsExplicitShape(symbol)) {
        messages_.Say(
            "Object '%s' with ATTRIBUTES(MANAGED) must also be allocatable, pointer, automatic, explicit shape, or a dummy argument"_err_en_US,
            symbol.name());
      }
      break;
    case common::CUDADataAttr::Pinned:
      if (inDeviceSubprogram) {
        Warn(common::UsageWarning::CUDAUsage,
            "Object '%s' with ATTRIBUTES(PINNED) may not be declared in a device subprogram"_warn_en_US,
            symbol.name());
      } else if (IsPointer(symbol)) {
        Warn(common::UsageWarning::CUDAUsage,
            "Object '%s' with ATTRIBUTES(PINNED) may not be a pointer"_warn_en_US,
            symbol.name());
      } else if (!IsAllocatable(symbol)) {
        Warn(common::UsageWarning::CUDAUsage,
            "Object '%s' with ATTRIBUTES(PINNED) should also be allocatable"_warn_en_US,
            symbol.name());
      }
      break;
    case common::CUDADataAttr::Shared:
      if (IsAllocatableOrPointer(symbol) || symbol.attrs().test(Attr::TARGET)) {
        messages_.Say(
            "Object '%s' with ATTRIBUTES(SHARED) may not be allocatable, pointer, or target"_err_en_US,
            symbol.name());
      } else if (!inDeviceSubprogram) {
        messages_.Say(
            "Object '%s' with ATTRIBUTES(SHARED) must be declared in a device subprogram"_err_en_US,
            symbol.name());
      }
      break;
    case common::CUDADataAttr::Unified:
      if (((!subpDetails &&
               symbol.owner().kind() != Scope::Kind::MainProgram) ||
              inDeviceSubprogram) &&
          !isComponent) {
        messages_.Say(
            "Object '%s' with ATTRIBUTES(UNIFIED) must be declared in a host subprogram"_err_en_US,
            symbol.name());
      }
      break;
    case common::CUDADataAttr::Texture:
      messages_.Say(
          "ATTRIBUTES(TEXTURE) is obsolete and no longer supported"_err_en_US);
      break;
    }
    if (attr != common::CUDADataAttr::Pinned) {
      if (details.commonBlock()) {
        messages_.Say(
            "Object '%s' with ATTRIBUTES(%s) may not be in COMMON"_err_en_US,
            symbol.name(),
            parser::ToUpperCaseLetters(common::EnumToString(attr)));
      } else if (FindEquivalenceSet(symbol)) {
        messages_.Say(
            "Object '%s' with ATTRIBUTES(%s) may not be in an equivalence group"_err_en_US,
            symbol.name(),
            parser::ToUpperCaseLetters(common::EnumToString(attr)));
      }
    }
    if (subpDetails /* not a module variable */ && IsSaved(symbol) &&
        !inDeviceSubprogram && !IsAllocatable(symbol) &&
        attr == common::CUDADataAttr::Device) {
      messages_.Say(
          "Saved object '%s' in host code may not have ATTRIBUTES(DEVICE) unless allocatable"_err_en_US,
          symbol.name(),
          parser::ToUpperCaseLetters(common::EnumToString(attr)));
    }
    if (isComponent) {
      if (attr == common::CUDADataAttr::Device) {
        const DeclTypeSpec *type{symbol.GetType()};
        if (const DerivedTypeSpec *
            derived{type ? type->AsDerived() : nullptr}) {
          DirectComponentIterator directs{*derived};
          if (auto iter{std::find_if(directs.begin(), directs.end(),
                  [](const Symbol &) { return false; })}) {
            messages_.Say(
                "Derived type component '%s' may not have ATTRIBUTES(DEVICE) as it has a direct device component '%s'"_err_en_US,
                symbol.name(), iter.BuildResultDesignatorName());
          }
        }
      } else if (attr == common::CUDADataAttr::Constant ||
          attr == common::CUDADataAttr::Shared) {
        messages_.Say(
            "Derived type component '%s' may not have ATTRIBUTES(%s)"_err_en_US,
            symbol.name(),
            parser::ToUpperCaseLetters(common::EnumToString(attr)));
      }
    } else if (!subpDetails && symbol.owner().kind() != Scope::Kind::Module &&
        symbol.owner().kind() != Scope::Kind::MainProgram &&
        symbol.owner().kind() != Scope::Kind::BlockConstruct &&
        symbol.owner().kind() != Scope::Kind::OpenACCConstruct) {
      messages_.Say(
          "ATTRIBUTES(%s) may apply only to module, host subprogram, block, or device subprogram data"_err_en_US,
          parser::ToUpperCaseLetters(common::EnumToString(attr)));
    }
  }

  if (derived && derived->IsVectorType()) {
    CHECK(type);
    std::string typeName{type->AsFortran()};
    if (IsAssumedShape(symbol)) {
      SayWithDeclaration(symbol,
          "Assumed-shape entity of %s type is not supported"_err_en_US,
          typeName);
    } else if (IsDeferredShape(symbol)) {
      SayWithDeclaration(symbol,
          "Deferred-shape entity of %s type is not supported"_err_en_US,
          typeName);
    } else if (IsAssumedRank(symbol)) {
      SayWithDeclaration(symbol,
          "Assumed rank entity of %s type is not supported"_err_en_US,
          typeName);
    }
  }
}

void CheckHelper::CheckPointerInitialization(const Symbol &symbol) {
  if (IsPointer(symbol) && !context_.HasError(symbol) &&
      !scopeIsUninstantiatedPDT_) {
    if (const auto *object{symbol.detailsIf<ObjectEntityDetails>()}) {
      if (object->init()) { // C764, C765; C808
        if (auto designator{evaluate::AsGenericExpr(symbol)}) {
          auto restorer{messages_.SetLocation(symbol.name())};
          context_.set_location(symbol.name());
          CheckInitialDataPointerTarget(
              context_, *designator, *object->init(), DEREF(scope_));
        }
      }
    } else if (const auto *proc{symbol.detailsIf<ProcEntityDetails>()}) {
      if (proc->init() && *proc->init()) {
        // C1519 - must be nonelemental external or module procedure,
        // or an unrestricted specific intrinsic function.
        const Symbol &local{DEREF(*proc->init())};
        const Symbol &ultimate{local.GetUltimate()};
        bool checkTarget{true};
        if (ultimate.attrs().test(Attr::INTRINSIC)) {
          if (auto intrinsic{context_.intrinsics().IsSpecificIntrinsicFunction(
                  ultimate.name().ToString())};
              !intrinsic || intrinsic->isRestrictedSpecific) { // C1030
            context_.Say(
                "Intrinsic procedure '%s' is not an unrestricted specific "
                "intrinsic permitted for use as the initializer for procedure "
                "pointer '%s'"_err_en_US,
                ultimate.name(), symbol.name());
            checkTarget = false;
          }
        } else if (!(ultimate.attrs().test(Attr::EXTERNAL) ||
                       ultimate.owner().kind() == Scope::Kind::Module ||
                       ultimate.owner().IsTopLevel()) ||
            IsDummy(ultimate) || IsPointer(ultimate)) {
          context_.Say(
              "Procedure pointer '%s' initializer '%s' is neither an external nor a module procedure"_err_en_US,
              symbol.name(), ultimate.name());
          checkTarget = false;
        } else if (IsElementalProcedure(ultimate)) {
          context_.Say("Procedure pointer '%s' cannot be initialized with the "
                       "elemental procedure '%s'"_err_en_US,
              symbol.name(), ultimate.name());
          checkTarget = false;
        }
        if (checkTarget) {
          SomeExpr lhs{evaluate::ProcedureDesignator{symbol}};
          SomeExpr rhs{evaluate::ProcedureDesignator{**proc->init()}};
          CheckPointerAssignment(context_, lhs, rhs,
              GetProgramUnitOrBlockConstructContaining(symbol),
              /*isBoundsRemapping=*/false, /*isAssumedRank=*/false);
        }
      }
    }
  }
}

// The six different kinds of array-specs:
//   array-spec     -> explicit-shape-list | deferred-shape-list
//                     | assumed-shape-list | implied-shape-list
//                     | assumed-size | assumed-rank
//   explicit-shape -> [ lb : ] ub
//   deferred-shape -> :
//   assumed-shape  -> [ lb ] :
//   implied-shape  -> [ lb : ] *
//   assumed-size   -> [ explicit-shape-list , ] [ lb : ] *
//   assumed-rank   -> ..
// Note:
// - deferred-shape is also an assumed-shape
// - A single "*" or "lb:*" might be assumed-size or implied-shape-list
void CheckHelper::CheckArraySpec(
    const Symbol &symbol, const ArraySpec &arraySpec) {
  if (arraySpec.Rank() == 0) {
    return;
  }
  bool isExplicit{arraySpec.IsExplicitShape()};
  bool canBeDeferred{arraySpec.CanBeDeferredShape()};
  bool canBeImplied{arraySpec.CanBeImpliedShape()};
  bool canBeAssumedShape{arraySpec.CanBeAssumedShape()};
  bool canBeAssumedSize{arraySpec.CanBeAssumedSize()};
  bool isAssumedRank{arraySpec.IsAssumedRank()};
  bool isCUDAShared{
      GetCUDADataAttr(&symbol).value_or(common::CUDADataAttr::Device) ==
      common::CUDADataAttr::Shared};
  bool isCrayPointee{symbol.test(Symbol::Flag::CrayPointee)};
  std::optional<parser::MessageFixedText> msg;
  if (isCrayPointee && !isExplicit && !canBeAssumedSize) {
    msg =
        "Cray pointee '%s' must have explicit shape or assumed size"_err_en_US;
  } else if (IsAllocatableOrPointer(symbol) && !canBeDeferred &&
      !isAssumedRank) {
    if (symbol.owner().IsDerivedType()) { // C745
      if (IsAllocatable(symbol)) {
        msg = "Allocatable array component '%s' must have"
              " deferred shape"_err_en_US;
      } else {
        msg = "Array pointer component '%s' must have deferred shape"_err_en_US;
      }
    } else {
      if (IsAllocatable(symbol)) { // C832
        msg = "Allocatable array '%s' must have deferred shape or"
              " assumed rank"_err_en_US;
      } else {
        msg = "Array pointer '%s' must have deferred shape or"
              " assumed rank"_err_en_US;
      }
    }
  } else if (IsDummy(symbol)) {
    if (canBeImplied && !canBeAssumedSize) { // C836
      msg = "Dummy array argument '%s' may not have implied shape"_err_en_US;
    }
  } else if (canBeAssumedShape && !canBeDeferred) {
    msg = "Assumed-shape array '%s' must be a dummy argument"_err_en_US;
  } else if (isAssumedRank) { // C837
    msg = "Assumed-rank array '%s' must be a dummy argument"_err_en_US;
  } else if (canBeAssumedSize && !canBeImplied && !isCUDAShared &&
      !isCrayPointee) { // C833
    msg = "Assumed-size array '%s' must be a dummy argument"_err_en_US;
  } else if (canBeImplied) {
    if (!IsNamedConstant(symbol) && !isCUDAShared &&
        !isCrayPointee) { // C835, C836
      msg = "Implied-shape array '%s' must be a named constant or a "
            "dummy argument"_err_en_US;
    }
  } else if (IsNamedConstant(symbol)) {
    if (!isExplicit && !canBeImplied) {
      msg = "Named constant '%s' array must have constant or"
            " implied shape"_err_en_US;
    }
  } else if (!isExplicit &&
      !(IsAllocatableOrPointer(symbol) || isCrayPointee)) {
    if (symbol.owner().IsDerivedType()) { // C749
      msg = "Component array '%s' without ALLOCATABLE or POINTER attribute must"
            " have explicit shape"_err_en_US;
    } else { // C816
      msg = "Array '%s' without ALLOCATABLE or POINTER attribute must have"
            " explicit shape"_err_en_US;
    }
  }
  if (msg) {
    context_.Say(std::move(*msg), symbol.name());
  }
}

void CheckHelper::CheckProcEntity(
    const Symbol &symbol, const ProcEntityDetails &details) {
  CheckSymbolType(symbol);
  const Symbol *interface{details.procInterface()};
  if (details.isDummy()) {
    if (!symbol.attrs().test(Attr::POINTER) && // C843
        symbol.attrs().HasAny(
            {Attr::INTENT_IN, Attr::INTENT_OUT, Attr::INTENT_INOUT})) {
      messages_.Say("A dummy procedure without the POINTER attribute"
                    " may not have an INTENT attribute"_err_en_US);
    }
    if (InElemental()) { // C15100
      messages_.Say(
          "An ELEMENTAL subprogram may not have a dummy procedure"_err_en_US);
    }
    if (interface && IsElementalProcedure(*interface)) {
      // There's no explicit constraint or "shall" that we can find in the
      // standard for this check, but it seems to be implied in multiple
      // sites, and ELEMENTAL non-intrinsic actual arguments *are*
      // explicitly forbidden.  But we allow "PROCEDURE(SIN)::dummy"
      // because it is explicitly legal to *pass* the specific intrinsic
      // function SIN as an actual argument.
      if (interface->attrs().test(Attr::INTRINSIC)) {
        Warn(common::UsageWarning::Portability,
            "A dummy procedure should not have an ELEMENTAL intrinsic as its interface"_port_en_US);
      } else {
        messages_.Say("A dummy procedure may not be ELEMENTAL"_err_en_US);
      }
    }
  } else if (IsPointer(symbol)) {
    CheckPointerInitialization(symbol);
    if (interface) {
      if (interface->attrs().test(Attr::INTRINSIC)) {
        auto intrinsic{context_.intrinsics().IsSpecificIntrinsicFunction(
            interface->name().ToString())};
        if (!intrinsic || intrinsic->isRestrictedSpecific) { // C1515
          messages_.Say(
              "Intrinsic procedure '%s' is not an unrestricted specific "
              "intrinsic permitted for use as the definition of the interface "
              "to procedure pointer '%s'"_err_en_US,
              interface->name(), symbol.name());
        } else if (IsElementalProcedure(*interface)) {
          Warn(common::UsageWarning::Portability,
              "Procedure pointer '%s' should not have an ELEMENTAL intrinsic as its interface"_port_en_US,
              symbol.name()); // C1517
        }
      } else if (IsElementalProcedure(*interface)) {
        messages_.Say("Procedure pointer '%s' may not be ELEMENTAL"_err_en_US,
            symbol.name()); // C1517
      }
    }
    if (symbol.owner().IsDerivedType()) {
      CheckPassArg(symbol, interface, details);
    }
  } else if (symbol.owner().IsDerivedType()) {
    const auto &name{symbol.name()};
    messages_.Say(name,
        "Procedure component '%s' must have POINTER attribute"_err_en_US, name);
  }
  CheckExternal(symbol);
}

// When a module subprogram has the MODULE prefix the following must match
// with the corresponding separate module procedure interface body:
// - C1549: characteristics and dummy argument names
// - C1550: binding label
// - C1551: NON_RECURSIVE prefix
class SubprogramMatchHelper {
public:
  explicit SubprogramMatchHelper(CheckHelper &checkHelper)
      : checkHelper{checkHelper} {}

  void Check(const Symbol &, const Symbol &);

private:
  SemanticsContext &context() { return checkHelper.context(); }
  void CheckDummyArg(const Symbol &, const Symbol &, const DummyArgument &,
      const DummyArgument &);
  void CheckDummyDataObject(const Symbol &, const Symbol &,
      const DummyDataObject &, const DummyDataObject &);
  void CheckDummyProcedure(const Symbol &, const Symbol &,
      const DummyProcedure &, const DummyProcedure &);
  bool CheckSameIntent(
      const Symbol &, const Symbol &, common::Intent, common::Intent);
  template <typename... A>
  void Say(
      const Symbol &, const Symbol &, parser::MessageFixedText &&, A &&...);
  template <typename ATTRS>
  bool CheckSameAttrs(const Symbol &, const Symbol &, ATTRS, ATTRS);
  bool ShapesAreCompatible(const DummyDataObject &, const DummyDataObject &);
  evaluate::Shape FoldShape(const evaluate::Shape &);
  std::optional<evaluate::Shape> FoldShape(
      const std::optional<evaluate::Shape> &shape) {
    if (shape) {
      return FoldShape(*shape);
    }
    return std::nullopt;
  }
  std::string AsFortran(DummyDataObject::Attr attr) {
    return parser::ToUpperCaseLetters(DummyDataObject::EnumToString(attr));
  }
  std::string AsFortran(DummyProcedure::Attr attr) {
    return parser::ToUpperCaseLetters(DummyProcedure::EnumToString(attr));
  }

  CheckHelper &checkHelper;
};

// 15.6.2.6 para 3 - can the result of an ENTRY differ from its function?
bool CheckHelper::IsResultOkToDiffer(const FunctionResult &result) {
  if (result.attrs.test(FunctionResult::Attr::Allocatable) ||
      result.attrs.test(FunctionResult::Attr::Pointer)) {
    return false;
  }
  const auto *typeAndShape{result.GetTypeAndShape()};
  if (!typeAndShape || typeAndShape->Rank() != 0) {
    return false;
  }
  auto category{typeAndShape->type().category()};
  if (category == TypeCategory::Character ||
      category == TypeCategory::Derived) {
    return false;
  }
  int kind{typeAndShape->type().kind()};
  return kind == context_.GetDefaultKind(category) ||
      (category == TypeCategory::Real &&
          kind == context_.doublePrecisionKind());
}

void CheckHelper::CheckSubprogram(
    const Symbol &symbol, const SubprogramDetails &details) {
  // Evaluate a procedure definition's characteristics to flush out
  // any errors that analysis might expose, in case this subprogram hasn't
  // had any calls in this compilation unit that would have validated them.
  if (!context_.HasError(symbol) && !details.isDummy() &&
      !details.isInterface() && !details.stmtFunction()) {
    if (!Procedure::Characterize(symbol, foldingContext_)) {
      context_.SetError(symbol);
    }
  }
  if (const Symbol *iface{FindSeparateModuleSubprogramInterface(&symbol)}) {
    SubprogramMatchHelper{*this}.Check(symbol, *iface);
  }
  if (const Scope *entryScope{details.entryScope()}) {
    // ENTRY F'2023 15.6.2.6
    std::optional<parser::MessageFixedText> error;
    const Symbol *subprogram{entryScope->symbol()};
    const SubprogramDetails *subprogramDetails{nullptr};
    if (subprogram) {
      subprogramDetails = subprogram->detailsIf<SubprogramDetails>();
    }
    if (!(entryScope->parent().IsGlobal() || entryScope->parent().IsModule() ||
            entryScope->parent().IsSubmodule())) {
      error = "ENTRY may not appear in an internal subprogram"_err_en_US;
    } else if (subprogramDetails && details.isFunction() &&
        subprogramDetails->isFunction() &&
        !context_.HasError(details.result()) &&
        !context_.HasError(subprogramDetails->result())) {
      auto result{FunctionResult::Characterize(
          details.result(), context_.foldingContext())};
      auto subpResult{FunctionResult::Characterize(
          subprogramDetails->result(), context_.foldingContext())};
      if (result && subpResult && *result != *subpResult &&
          (!IsResultOkToDiffer(*result) || !IsResultOkToDiffer(*subpResult))) {
        error =
            "Result of ENTRY is not compatible with result of containing function"_err_en_US;
      }
    }
    if (error) {
      if (auto *msg{messages_.Say(symbol.name(), *error)}) {
        if (subprogram) {
          msg->Attach(subprogram->name(), "Containing subprogram"_en_US);
        }
      }
    }
  }
  if (details.isFunction() &&
      details.result().name() != symbol.name()) { // F'2023 C1569 & C1583
    if (auto iter{symbol.owner().find(details.result().name())};
        iter != symbol.owner().end()) {
      const Symbol &resNameSym{*iter->second};
      if (const auto *resNameSubp{resNameSym.detailsIf<SubprogramDetails>()}) {
        if (const Scope * resNameEntryScope{resNameSubp->entryScope()}) {
          const Scope *myScope{
              details.entryScope() ? details.entryScope() : symbol.scope()};
          if (resNameEntryScope == myScope) {
            if (auto *msg{messages_.Say(symbol.name(),
                    "Explicit RESULT('%s') of function '%s' cannot have the same name as a distinct ENTRY into the same scope"_err_en_US,
                    details.result().name(), symbol.name())}) {
              msg->Attach(
                  resNameSym.name(), "ENTRY with conflicting name"_en_US);
            }
          }
        }
      }
    }
  }
  if (const MaybeExpr & stmtFunction{details.stmtFunction()}) {
    if (auto msg{evaluate::CheckStatementFunction(
            symbol, *stmtFunction, context_.foldingContext())}) {
      SayWithDeclaration(symbol, std::move(*msg));
    } else if (IsPointer(symbol)) {
      SayWithDeclaration(symbol,
          "A statement function must not have the POINTER attribute"_err_en_US);
    } else if (details.result().flags().test(Symbol::Flag::Implicit)) {
      // 15.6.4 p2 weird requirement
      if (const Symbol *
          host{symbol.owner().parent().FindSymbol(symbol.name())}) {
        evaluate::AttachDeclaration(
            Warn(common::LanguageFeature::StatementFunctionExtensions,
                symbol.name(),
                "An implicitly typed statement function should not appear when the same symbol is available in its host scope"_port_en_US),
            *host);
      }
    }
    if (GetProgramUnitOrBlockConstructContaining(symbol).kind() ==
        Scope::Kind::BlockConstruct) { // C1107
      messages_.Say(symbol.name(),
          "A statement function definition may not appear in a BLOCK construct"_err_en_US);
    }
  }
  if (IsElementalProcedure(symbol)) {
    // See comment on the similar check in CheckProcEntity()
    if (details.isDummy()) {
      messages_.Say("A dummy procedure may not be ELEMENTAL"_err_en_US);
    } else {
      for (const Symbol *dummy : details.dummyArgs()) {
        if (!dummy) { // C15100
          messages_.Say(
              "An ELEMENTAL subroutine may not have an alternate return dummy argument"_err_en_US);
        }
      }
    }
  }
  if (details.isInterface()) {
    if (!details.isDummy() && details.isFunction() &&
        IsAssumedLengthCharacter(details.result())) { // C721
      messages_.Say(details.result().name(),
          "A function interface may not declare an assumed-length CHARACTER(*) result"_err_en_US);
    }
    if (symbol.attrs().test(Attr::ABSTRACT) &&
        (symbol.name() == "integer" || symbol.name() == "unsigned" ||
            symbol.name() == "real" || symbol.name() == "complex" ||
            symbol.name() == "character" ||
            symbol.name() == "logical")) { // F'2023 C1503
      messages_.Say(
          "An ABSTRACT interface may not have the same name as an intrinsic type"_err_en_US);
    }
  }
  CheckExternal(symbol);
  CheckModuleProcedureDef(symbol);
  auto cudaAttrs{details.cudaSubprogramAttrs()};
  if (cudaAttrs &&
      (*cudaAttrs == common::CUDASubprogramAttrs::Global ||
          *cudaAttrs == common::CUDASubprogramAttrs::Grid_Global) &&
      details.isFunction()) {
    messages_.Say(symbol.name(),
        "A function may not have ATTRIBUTES(GLOBAL) or ATTRIBUTES(GRID_GLOBAL)"_err_en_US);
  }
  if (cudaAttrs &&
      (*cudaAttrs == common::CUDASubprogramAttrs::Global ||
          *cudaAttrs == common::CUDASubprogramAttrs::Grid_Global) &&
      symbol.attrs().HasAny({Attr::RECURSIVE, Attr::PURE, Attr::ELEMENTAL})) {
    messages_.Say(symbol.name(),
        "A kernel subprogram may not be RECURSIVE, PURE, or ELEMENTAL"_err_en_US);
  }
  if (cudaAttrs && *cudaAttrs != common::CUDASubprogramAttrs::Host) {
    // CUDA device subprogram checks
    if (ClassifyProcedure(symbol) == ProcedureDefinitionClass::Internal) {
      messages_.Say(symbol.name(),
          "A device subprogram may not be an internal subprogram"_err_en_US);
    }
  }
  if ((!details.cudaLaunchBounds().empty() ||
          !details.cudaClusterDims().empty()) &&
      !(cudaAttrs &&
          (*cudaAttrs == common::CUDASubprogramAttrs::Global ||
              *cudaAttrs == common::CUDASubprogramAttrs::Grid_Global))) {
    messages_.Say(symbol.name(),
        "A subroutine may not have LAUNCH_BOUNDS() or CLUSTER_DIMS() unless it has ATTRIBUTES(GLOBAL) or ATTRIBUTES(GRID_GLOBAL)"_err_en_US);
  }
  if (!IsStmtFunction(symbol)) {
    if (const Scope * outerDevice{FindCUDADeviceContext(&symbol.owner())};
        outerDevice && outerDevice->symbol()) {
      if (auto *msg{messages_.Say(symbol.name(),
              "'%s' may not be an internal procedure of CUDA device subprogram '%s'"_err_en_US,
              symbol.name(), outerDevice->symbol()->name())}) {
        msg->Attach(outerDevice->symbol()->name(),
            "Containing CUDA device subprogram"_en_US);
      }
    }
  }
}

void CheckHelper::CheckExternal(const Symbol &symbol) {
  if (IsExternal(symbol)) {
    std::string interfaceName{symbol.name().ToString()};
    if (const auto *bind{symbol.GetBindName()}) {
      interfaceName = *bind;
    }
    if (const Symbol * global{FindGlobal(symbol)};
        global && global != &symbol) {
      std::string definitionName{global->name().ToString()};
      if (const auto *bind{global->GetBindName()}) {
        definitionName = *bind;
      }
      if (interfaceName == definitionName) {
        parser::Message *msg{nullptr};
        if (!IsProcedure(*global)) {
          if ((symbol.flags().test(Symbol::Flag::Function) ||
                  symbol.flags().test(Symbol::Flag::Subroutine))) {
            msg = Warn(common::UsageWarning::ExternalNameConflict,
                "The global entity '%s' corresponding to the local procedure '%s' is not a callable subprogram"_warn_en_US,
                global->name(), symbol.name());
          }
        } else if (auto chars{Characterize(symbol)}) {
          if (auto globalChars{Characterize(*global)}) {
            if (chars->HasExplicitInterface()) {
              std::string whyNot;
              if (!chars->IsCompatibleWith(*globalChars,
                      /*ignoreImplicitVsExplicit=*/false, &whyNot)) {
                msg = Warn(common::UsageWarning::ExternalInterfaceMismatch,
                    "The global subprogram '%s' is not compatible with its local procedure declaration (%s)"_warn_en_US,
                    global->name(), whyNot);
              }
            } else if (!globalChars->CanBeCalledViaImplicitInterface()) {
              // TODO: This should be a hard error if the procedure has
              // actually been called (as opposed to just being used as a
              // procedure pointer target or passed as an actual argument).
              msg = Warn(common::UsageWarning::ExternalInterfaceMismatch,
                  "The global subprogram '%s' should not be referenced via the implicit interface '%s'"_warn_en_US,
                  global->name(), symbol.name());
            }
          }
        }
        if (msg) {
          if (msg->IsFatal()) {
            context_.SetError(symbol);
          }
          evaluate::AttachDeclaration(msg, *global);
          evaluate::AttachDeclaration(msg, symbol);
        }
      }
    } else if (auto iter{externalNames_.find(interfaceName)};
               iter != externalNames_.end()) {
      const Symbol &previous{*iter->second};
      if (auto chars{Characterize(symbol)}) {
        if (auto previousChars{Characterize(previous)}) {
          std::string whyNot;
          if (!chars->IsCompatibleWith(*previousChars,
                  /*ignoreImplicitVsExplicit=*/true, &whyNot)) {
            if (auto *msg{Warn(common::UsageWarning::ExternalInterfaceMismatch,
                    "The external interface '%s' is not compatible with an earlier definition (%s)"_warn_en_US,
                    symbol.name(), whyNot)}) {
              evaluate::AttachDeclaration(msg, previous);
              evaluate::AttachDeclaration(msg, symbol);
            }
          }
        }
      }
    } else {
      externalNames_.emplace(interfaceName, symbol);
    }
  }
}

void CheckHelper::CheckDerivedType(
    const Symbol &derivedType, const DerivedTypeDetails &details) {
  if (details.isForwardReferenced() && !context_.HasError(derivedType)) {
    messages_.Say("The derived type '%s' has not been defined"_err_en_US,
        derivedType.name());
  }
  const Scope *scope{derivedType.scope()};
  if (!scope) {
    CHECK(details.isForwardReferenced());
    return;
  }
  CHECK(scope->symbol() == &derivedType);
  CHECK(scope->IsDerivedType());
  if (derivedType.attrs().test(Attr::ABSTRACT) && // C734
      (derivedType.attrs().test(Attr::BIND_C) || details.sequence())) {
    messages_.Say("An ABSTRACT derived type must be extensible"_err_en_US);
  }
  if (const DeclTypeSpec *parent{FindParentTypeSpec(derivedType)}) {
    const DerivedTypeSpec *parentDerived{parent->AsDerived()};
    if (!IsExtensibleType(parentDerived)) { // C705
      messages_.Say("The parent type is not extensible"_err_en_US);
    }
    if (!derivedType.attrs().test(Attr::ABSTRACT) && parentDerived &&
        parentDerived->typeSymbol().attrs().test(Attr::ABSTRACT)) {
      ScopeComponentIterator components{*parentDerived};
      for (const Symbol &component : components) {
        if (component.attrs().test(Attr::DEFERRED)) {
          if (scope->FindComponent(component.name()) == &component) {
            SayWithDeclaration(component,
                "Non-ABSTRACT extension of ABSTRACT derived type '%s' lacks a binding for DEFERRED procedure '%s'"_err_en_US,
                parentDerived->typeSymbol().name(), component.name());
          }
        }
      }
    }
    DerivedTypeSpec derived{derivedType.name(), derivedType};
    derived.set_scope(*scope);
    if (FindCoarrayUltimateComponent(derived) && // C736
        !(parentDerived && FindCoarrayUltimateComponent(*parentDerived))) {
      messages_.Say(
          "Type '%s' has a coarray ultimate component so the type at the base "
          "of its type extension chain ('%s') must be a type that has a "
          "coarray ultimate component"_err_en_US,
          derivedType.name(), scope->GetDerivedTypeBase().GetSymbol()->name());
    }
    if (FindEventOrLockPotentialComponent(derived) && // C737
        !(FindEventOrLockPotentialComponent(*parentDerived) ||
            IsEventTypeOrLockType(parentDerived))) {
      messages_.Say(
          "Type '%s' has an EVENT_TYPE or LOCK_TYPE component, so the type "
          "at the base of its type extension chain ('%s') must either have an "
          "EVENT_TYPE or LOCK_TYPE component, or be EVENT_TYPE or "
          "LOCK_TYPE"_err_en_US,
          derivedType.name(), scope->GetDerivedTypeBase().GetSymbol()->name());
    }
  }
  if (HasIntrinsicTypeName(derivedType)) { // C729
    messages_.Say("A derived type name cannot be the name of an intrinsic"
                  " type"_err_en_US);
  }
  std::map<SourceName, SymbolRef> previous;
  for (const auto &pair : details.finals()) {
    SourceName source{pair.first};
    const Symbol &ref{*pair.second};
    if (CheckFinal(ref, source, derivedType) &&
        std::all_of(previous.begin(), previous.end(),
            [&](std::pair<SourceName, SymbolRef> prev) {
              return CheckDistinguishableFinals(
                  ref, source, *prev.second, prev.first, derivedType);
            })) {
      previous.emplace(source, ref);
    }
  }
}

// C786
bool CheckHelper::CheckFinal(
    const Symbol &subroutine, SourceName finalName, const Symbol &derivedType) {
  if (!IsModuleProcedure(subroutine)) {
    SayWithDeclaration(subroutine, finalName,
        "FINAL subroutine '%s' of derived type '%s' must be a module procedure"_err_en_US,
        subroutine.name(), derivedType.name());
    return false;
  }
  const Procedure *proc{Characterize(subroutine)};
  if (!proc) {
    return false; // error recovery
  }
  if (!proc->IsSubroutine()) {
    SayWithDeclaration(subroutine, finalName,
        "FINAL subroutine '%s' of derived type '%s' must be a subroutine"_err_en_US,
        subroutine.name(), derivedType.name());
    return false;
  }
  if (proc->dummyArguments.size() != 1) {
    SayWithDeclaration(subroutine, finalName,
        "FINAL subroutine '%s' of derived type '%s' must have a single dummy argument"_err_en_US,
        subroutine.name(), derivedType.name());
    return false;
  }
  const auto &arg{proc->dummyArguments[0]};
  const Symbol *errSym{&subroutine};
  if (const auto *details{subroutine.detailsIf<SubprogramDetails>()}) {
    if (!details->dummyArgs().empty()) {
      if (const Symbol *argSym{details->dummyArgs()[0]}) {
        errSym = argSym;
      }
    }
  }
  const auto *ddo{std::get_if<DummyDataObject>(&arg.u)};
  if (!ddo) {
    SayWithDeclaration(subroutine, finalName,
        "FINAL subroutine '%s' of derived type '%s' must have a single dummy argument that is a data object"_err_en_US,
        subroutine.name(), derivedType.name());
    return false;
  }
  bool ok{true};
  if (arg.IsOptional()) {
    SayWithDeclaration(*errSym, finalName,
        "FINAL subroutine '%s' of derived type '%s' must not have an OPTIONAL dummy argument"_err_en_US,
        subroutine.name(), derivedType.name());
    ok = false;
  }
  if (ddo->attrs.test(DummyDataObject::Attr::Allocatable)) {
    SayWithDeclaration(*errSym, finalName,
        "FINAL subroutine '%s' of derived type '%s' must not have an ALLOCATABLE dummy argument"_err_en_US,
        subroutine.name(), derivedType.name());
    ok = false;
  }
  if (ddo->attrs.test(DummyDataObject::Attr::Pointer)) {
    SayWithDeclaration(*errSym, finalName,
        "FINAL subroutine '%s' of derived type '%s' must not have a POINTER dummy argument"_err_en_US,
        subroutine.name(), derivedType.name());
    ok = false;
  }
  if (ddo->intent == common::Intent::Out) {
    SayWithDeclaration(*errSym, finalName,
        "FINAL subroutine '%s' of derived type '%s' must not have a dummy argument with INTENT(OUT)"_err_en_US,
        subroutine.name(), derivedType.name());
    ok = false;
  }
  if (ddo->attrs.test(DummyDataObject::Attr::Value)) {
    SayWithDeclaration(*errSym, finalName,
        "FINAL subroutine '%s' of derived type '%s' must not have a dummy argument with the VALUE attribute"_err_en_US,
        subroutine.name(), derivedType.name());
    ok = false;
  }
  if (ddo->type.corank() > 0) {
    SayWithDeclaration(*errSym, finalName,
        "FINAL subroutine '%s' of derived type '%s' must not have a coarray dummy argument"_err_en_US,
        subroutine.name(), derivedType.name());
    ok = false;
  }
  if (ddo->type.type().IsPolymorphic()) {
    SayWithDeclaration(*errSym, finalName,
        "FINAL subroutine '%s' of derived type '%s' must not have a polymorphic dummy argument"_err_en_US,
        subroutine.name(), derivedType.name());
    ok = false;
  } else if (ddo->type.type().category() != TypeCategory::Derived ||
      &ddo->type.type().GetDerivedTypeSpec().typeSymbol() != &derivedType) {
    SayWithDeclaration(*errSym, finalName,
        "FINAL subroutine '%s' of derived type '%s' must have a TYPE(%s) dummy argument"_err_en_US,
        subroutine.name(), derivedType.name(), derivedType.name());
    ok = false;
  } else { // check that all LEN type parameters are assumed
    for (auto ref : OrderParameterDeclarations(derivedType)) {
      if (IsLenTypeParameter(*ref)) {
        const auto *value{
            ddo->type.type().GetDerivedTypeSpec().FindParameter(ref->name())};
        if (!value || !value->isAssumed()) {
          SayWithDeclaration(*errSym, finalName,
              "FINAL subroutine '%s' of derived type '%s' must have a dummy argument with an assumed LEN type parameter '%s=*'"_err_en_US,
              subroutine.name(), derivedType.name(), ref->name());
          ok = false;
        }
      }
    }
  }
  return ok;
}

bool CheckHelper::CheckDistinguishableFinals(const Symbol &f1,
    SourceName f1Name, const Symbol &f2, SourceName f2Name,
    const Symbol &derivedType) {
  const Procedure *p1{Characterize(f1)};
  const Procedure *p2{Characterize(f2)};
  if (p1 && p2) {
    if (characteristics::Distinguishable(context_.languageFeatures(), *p1, *p2)
            .value_or(false)) {
      return true;
    }
    if (auto *msg{messages_.Say(f1Name,
            "FINAL subroutines '%s' and '%s' of derived type '%s' cannot be distinguished by rank or KIND type parameter value"_err_en_US,
            f1Name, f2Name, derivedType.name())}) {
      msg->Attach(f2Name, "FINAL declaration of '%s'"_en_US, f2.name())
          .Attach(f1.name(), "Definition of '%s'"_en_US, f1Name)
          .Attach(f2.name(), "Definition of '%s'"_en_US, f2Name);
    }
  }
  return false;
}

void CheckHelper::CheckHostAssoc(
    const Symbol &symbol, const HostAssocDetails &details) {
  const Symbol &hostSymbol{details.symbol()};
  if (hostSymbol.test(Symbol::Flag::ImplicitOrError)) {
    if (details.implicitOrSpecExprError) {
      messages_.Say("Implicitly typed local entity '%s' not allowed in"
                    " specification expression"_err_en_US,
          symbol.name());
    } else if (details.implicitOrExplicitTypeError) {
      messages_.Say(
          "No explicit type declared for '%s'"_err_en_US, symbol.name());
    }
  }
}

void CheckHelper::CheckGeneric(
    const Symbol &symbol, const GenericDetails &details) {
  CheckSpecifics(symbol, details);
  common::visit(common::visitors{
                    [&](const common::DefinedIo &io) {
                      CheckDefinedIoProc(symbol, details, io);
                    },
                    [&](const GenericKind::OtherKind &other) {
                      if (other == GenericKind::OtherKind::Name) {
                        CheckGenericVsIntrinsic(symbol, details);
                      }
                    },
                    [](const auto &) {},
                },
      details.kind().u);
  // Ensure that shadowed symbols are checked
  if (details.specific()) {
    Check(*details.specific());
  }
  if (details.derivedType()) {
    Check(*details.derivedType());
  }
}

// Check that the specifics of this generic are distinguishable from each other
void CheckHelper::CollectSpecifics(DistinguishabilityHelper &helper,
    const Symbol &generic, const GenericDetails &details) {
  GenericKind kind{details.kind()};
  for (const Symbol &specific : details.specificProcs()) {
    if (specific.attrs().test(Attr::ABSTRACT)) {
      if (auto *msg{messages_.Say(generic.name(),
              "Generic interface '%s' must not use abstract interface '%s' as a specific procedure"_err_en_US,
              generic.name(), specific.name())}) {
        msg->Attach(
            specific.name(), "Definition of '%s'"_en_US, specific.name());
      }
      continue;
    }
    if (specific.attrs().test(Attr::INTRINSIC)) {
      // GNU Fortran allows INTRINSIC procedures in generics.
      auto intrinsic{context_.intrinsics().IsSpecificIntrinsicFunction(
          specific.name().ToString())};
      if (intrinsic && !intrinsic->isRestrictedSpecific) {
        if (auto *msg{Warn(common::LanguageFeature::IntrinsicAsSpecific,
                specific.name(),
                "Specific procedure '%s' of generic interface '%s' should not be INTRINSIC"_port_en_US,
                specific.name(), generic.name())}) {
          msg->Attach(
              generic.name(), "Definition of '%s'"_en_US, generic.name());
        }
      } else {
        if (auto *msg{Warn(common::LanguageFeature::IntrinsicAsSpecific,
                specific.name(),
                "Procedure '%s' of generic interface '%s' is INTRINSIC but not an unrestricted specific intrinsic function"_port_en_US,
                specific.name(), generic.name())}) {
          msg->Attach(
              generic.name(), "Definition of '%s'"_en_US, generic.name());
        }
        continue;
      }
    }
    if (IsStmtFunction(specific)) {
      if (auto *msg{messages_.Say(specific.name(),
              "Specific procedure '%s' of generic interface '%s' may not be a statement function"_err_en_US,
              specific.name(), generic.name())}) {
        msg->Attach(generic.name(), "Definition of '%s'"_en_US, generic.name());
      }
      continue;
    }
    if (const Procedure *procedure{Characterize(specific)}) {
      if (procedure->HasExplicitInterface()) {
        helper.Add(generic, kind, specific, *procedure);
      } else {
        if (auto *msg{messages_.Say(specific.name(),
                "Specific procedure '%s' of generic interface '%s' must have an explicit interface"_err_en_US,
                specific.name(), generic.name())}) {
          msg->Attach(
              generic.name(), "Definition of '%s'"_en_US, generic.name());
        }
      }
    }
  }
  if (const Scope * parent{generic.owner().GetDerivedTypeParent()}) {
    if (const Symbol * inherited{parent->FindComponent(generic.name())}) {
      if (IsAccessible(*inherited, generic.owner().parent())) {
        if (const auto *details{inherited->detailsIf<GenericDetails>()}) {
          // Include specifics of inherited generic of the same name, too
          CollectSpecifics(helper, *inherited, *details);
        }
      }
    }
  }
}

void CheckHelper::CheckSpecifics(
    const Symbol &generic, const GenericDetails &details) {
  DistinguishabilityHelper helper{context_};
  CollectSpecifics(helper, generic, details);
  helper.Check(generic.owner());
}

static bool CUDAHostDeviceDiffer(
    const Procedure &proc, const DummyDataObject &arg) {
  auto procCUDA{
      proc.cudaSubprogramAttrs.value_or(common::CUDASubprogramAttrs::Host)};
  bool procIsHostOnly{procCUDA == common::CUDASubprogramAttrs::Host};
  bool procIsDeviceOnly{
      !procIsHostOnly && procCUDA != common::CUDASubprogramAttrs::HostDevice};
  const auto &argCUDA{arg.cudaDataAttr};
  bool argIsHostOnly{!argCUDA || *argCUDA == common::CUDADataAttr::Pinned};
  bool argIsDeviceOnly{(!argCUDA && procIsDeviceOnly) ||
      (argCUDA &&
          (*argCUDA != common::CUDADataAttr::Managed &&
              *argCUDA != common::CUDADataAttr::Pinned &&
              *argCUDA != common::CUDADataAttr::Unified))};
  return (procIsHostOnly && argIsDeviceOnly) ||
      (procIsDeviceOnly && argIsHostOnly);
}

static bool ConflictsWithIntrinsicAssignment(const Procedure &proc) {
  const auto &lhsData{std::get<DummyDataObject>(proc.dummyArguments[0].u)};
  const auto &lhsTnS{lhsData.type};
  const auto &rhsData{std::get<DummyDataObject>(proc.dummyArguments[1].u)};
  const auto &rhsTnS{rhsData.type};
  return !CUDAHostDeviceDiffer(proc, lhsData) &&
      !CUDAHostDeviceDiffer(proc, rhsData) &&
      Tristate::No ==
      IsDefinedAssignment(
          lhsTnS.type(), lhsTnS.Rank(), rhsTnS.type(), rhsTnS.Rank());
}

static bool ConflictsWithIntrinsicOperator(
    const GenericKind &kind, const Procedure &proc, SemanticsContext &context) {
  if (!kind.IsIntrinsicOperator()) {
    return false;
  }
  const auto &arg0Data{std::get<DummyDataObject>(proc.dummyArguments[0].u)};
  if (CUDAHostDeviceDiffer(proc, arg0Data)) {
    return false;
  }
  const auto &arg0TnS{arg0Data.type};
  auto type0{arg0TnS.type()};
  if (proc.dummyArguments.size() == 1) { // unary
    return common::visit(
        common::visitors{
            [&](common::NumericOperator) { return IsIntrinsicNumeric(type0); },
            [&](common::LogicalOperator) { return IsIntrinsicLogical(type0); },
            [](const auto &) -> bool { DIE("bad generic kind"); },
        },
        kind.u);
  } else { // binary
    int rank0{arg0TnS.Rank()};
    const auto &arg1Data{std::get<DummyDataObject>(proc.dummyArguments[1].u)};
    if (CUDAHostDeviceDiffer(proc, arg1Data)) {
      return false;
    }
    const auto &arg1TnS{arg1Data.type};
    auto type1{arg1TnS.type()};
    int rank1{arg1TnS.Rank()};
    return common::visit(
        common::visitors{
            [&](common::NumericOperator) {
              return IsIntrinsicNumeric(type0, rank0, type1, rank1);
            },
            [&](common::LogicalOperator) {
              return IsIntrinsicLogical(type0, rank0, type1, rank1);
            },
            [&](common::RelationalOperator opr) {
              return IsIntrinsicRelational(opr, type0, rank0, type1, rank1);
            },
            [&](GenericKind::OtherKind x) {
              CHECK(x == GenericKind::OtherKind::Concat);
              return IsIntrinsicConcat(type0, rank0, type1, rank1);
            },
            [](const auto &) -> bool { DIE("bad generic kind"); },
        },
        kind.u);
  }
}

// Check if this procedure can be used for defined operators (see 15.4.3.4.2).
bool CheckHelper::CheckDefinedOperator(SourceName opName, GenericKind kind,
    const Symbol &specific, const Procedure &proc) {
  if (context_.HasError(specific)) {
    return false;
  }
  std::optional<parser::MessageFixedText> msg;
  auto checkDefinedOperatorArgs{
      [&](SourceName opName, const Symbol &specific, const Procedure &proc) {
        bool arg0Defined{CheckDefinedOperatorArg(opName, specific, proc, 0)};
        bool arg1Defined{CheckDefinedOperatorArg(opName, specific, proc, 1)};
        return arg0Defined && arg1Defined;
      }};
  if (specific.attrs().test(Attr::NOPASS)) { // C774
    msg = "%s procedure '%s' may not have NOPASS attribute"_err_en_US;
  } else if (!proc.functionResult.has_value()) {
    msg = "%s procedure '%s' must be a function"_err_en_US;
  } else if (proc.functionResult->IsAssumedLengthCharacter()) {
    const auto *subpDetails{specific.detailsIf<SubprogramDetails>()};
    if (subpDetails && !subpDetails->isDummy() && subpDetails->isInterface()) {
      // Error is caught by more general test for interfaces with
      // assumed-length character function results
      return true;
    }
    msg = "%s function '%s' may not have assumed-length CHARACTER(*)"
          " result"_err_en_US;
  } else if (auto m{CheckNumberOfArgs(kind, proc.dummyArguments.size())}) {
    if (m->IsFatal()) {
      msg = *m;
    } else {
      evaluate::AttachDeclaration(
          Warn(common::UsageWarning::DefinedOperatorArgs, specific.name(),
              std::move(*m), MakeOpName(opName), specific.name()),
          specific);
      return true;
    }
  } else if (!checkDefinedOperatorArgs(opName, specific, proc)) {
    return false; // error was reported
  } else if (ConflictsWithIntrinsicOperator(kind, proc, context_)) {
    msg = "%s function '%s' conflicts with intrinsic operator"_err_en_US;
  }
  if (msg) {
    SayWithDeclaration(
        specific, std::move(*msg), MakeOpName(opName), specific.name());
    context_.SetError(specific);
    return false;
  }
  return true;
}

// If the number of arguments is wrong for this intrinsic operator, return
// false and return the error message in msg.
std::optional<parser::MessageFixedText> CheckHelper::CheckNumberOfArgs(
    const GenericKind &kind, std::size_t nargs) {
  if (!kind.IsIntrinsicOperator()) {
    if (nargs < 1 || nargs > 2) {
      if (context_.ShouldWarn(common::UsageWarning::DefinedOperatorArgs)) {
        return "%s function '%s' should have 1 or 2 dummy arguments"_warn_en_US;
      }
    }
    return std::nullopt;
  }
  std::size_t min{2}, max{2}; // allowed number of args; default is binary
  common::visit(common::visitors{
                    [&](const common::NumericOperator &x) {
                      if (x == common::NumericOperator::Add ||
                          x == common::NumericOperator::Subtract) {
                        min = 1; // + and - are unary or binary
                      }
                    },
                    [&](const common::LogicalOperator &x) {
                      if (x == common::LogicalOperator::Not) {
                        min = 1; // .NOT. is unary
                        max = 1;
                      }
                    },
                    [](const common::RelationalOperator &) {
                      // all are binary
                    },
                    [](const GenericKind::OtherKind &x) {
                      CHECK(x == GenericKind::OtherKind::Concat);
                    },
                    [](const auto &) { DIE("expected intrinsic operator"); },
                },
      kind.u);
  if (nargs >= min && nargs <= max) {
    return std::nullopt;
  } else if (max == 1) {
    return "%s function '%s' must have one dummy argument"_err_en_US;
  } else if (min == 2) {
    return "%s function '%s' must have two dummy arguments"_err_en_US;
  } else {
    return "%s function '%s' must have one or two dummy arguments"_err_en_US;
  }
}

bool CheckHelper::CheckDefinedOperatorArg(const SourceName &opName,
    const Symbol &symbol, const Procedure &proc, std::size_t pos) {
  if (pos >= proc.dummyArguments.size()) {
    return true;
  }
  auto &arg{proc.dummyArguments.at(pos)};
  std::optional<parser::MessageFixedText> msg;
  if (arg.IsOptional()) {
    msg =
        "In %s function '%s', dummy argument '%s' may not be OPTIONAL"_err_en_US;
  } else if (const auto *dataObject{std::get_if<DummyDataObject>(&arg.u)};
             dataObject == nullptr) {
    msg =
        "In %s function '%s', dummy argument '%s' must be a data object"_err_en_US;
  } else if (dataObject->intent == common::Intent::Out) {
    msg =
        "In %s function '%s', dummy argument '%s' may not be INTENT(OUT)"_err_en_US;
  } else if (dataObject->intent != common::Intent::In &&
      !dataObject->attrs.test(DummyDataObject::Attr::Value)) {
    evaluate::AttachDeclaration(
        Warn(common::UsageWarning::DefinedOperatorArgs,
            "In %s function '%s', dummy argument '%s' should have INTENT(IN) or VALUE attribute"_warn_en_US,
            parser::ToUpperCaseLetters(opName.ToString()), symbol.name(),
            arg.name),
        symbol);
    return true;
  }
  if (msg) {
    SayWithDeclaration(symbol, std::move(*msg),
        parser::ToUpperCaseLetters(opName.ToString()), symbol.name(), arg.name);
    return false;
  }
  return true;
}

// Check if this procedure can be used for defined assignment (see 15.4.3.4.3).
bool CheckHelper::CheckDefinedAssignment(
    const Symbol &specific, const Procedure &proc) {
  if (context_.HasError(specific)) {
    return false;
  }
  std::optional<parser::MessageFixedText> msg;
  if (specific.attrs().test(Attr::NOPASS)) { // C774
    msg = "Defined assignment procedure '%s' may not have"
          " NOPASS attribute"_err_en_US;
  } else if (!proc.IsSubroutine()) {
    msg = "Defined assignment procedure '%s' must be a subroutine"_err_en_US;
  } else if (proc.dummyArguments.size() != 2) {
    msg = "Defined assignment subroutine '%s' must have"
          " two dummy arguments"_err_en_US;
  } else {
    // Check both arguments even if the first has an error.
    bool ok0{CheckDefinedAssignmentArg(specific, proc.dummyArguments[0], 0)};
    bool ok1{CheckDefinedAssignmentArg(specific, proc.dummyArguments[1], 1)};
    if (!(ok0 && ok1)) {
      return false; // error was reported
    } else if (ConflictsWithIntrinsicAssignment(proc)) {
      msg =
          "Defined assignment subroutine '%s' conflicts with intrinsic assignment"_err_en_US;
    } else {
      return true; // OK
    }
  }
  SayWithDeclaration(specific, std::move(msg.value()), specific.name());
  context_.SetError(specific);
  return false;
}

bool CheckHelper::CheckDefinedAssignmentArg(
    const Symbol &symbol, const DummyArgument &arg, int pos) {
  std::optional<parser::MessageFixedText> msg;
  if (arg.IsOptional()) {
    msg = "In defined assignment subroutine '%s', dummy argument '%s'"
          " may not be OPTIONAL"_err_en_US;
  } else if (const auto *dataObject{std::get_if<DummyDataObject>(&arg.u)}) {
    if (pos == 0) {
      if (dataObject->intent == common::Intent::In) {
        msg = "In defined assignment subroutine '%s', first dummy argument '%s'"
              " may not have INTENT(IN)"_err_en_US;
      } else if (dataObject->intent != common::Intent::Out &&
          dataObject->intent != common::Intent::InOut) {
        msg =
            "In defined assignment subroutine '%s', first dummy argument '%s' should have INTENT(OUT) or INTENT(INOUT)"_warn_en_US;
      }
    } else if (pos == 1) {
      if (dataObject->intent == common::Intent::Out) {
        msg = "In defined assignment subroutine '%s', second dummy"
              " argument '%s' may not have INTENT(OUT)"_err_en_US;
      } else if (dataObject->intent != common::Intent::In &&
          !dataObject->attrs.test(DummyDataObject::Attr::Value)) {
        msg =
            "In defined assignment subroutine '%s', second dummy argument '%s' should have INTENT(IN) or VALUE attribute"_warn_en_US;
      } else if (dataObject->attrs.test(DummyDataObject::Attr::Pointer)) {
        msg =
            "In defined assignment subroutine '%s', second dummy argument '%s' must not be a pointer"_err_en_US;
      } else if (dataObject->attrs.test(DummyDataObject::Attr::Allocatable)) {
        msg =
            "In defined assignment subroutine '%s', second dummy argument '%s' must not be an allocatable"_err_en_US;
      }
    } else {
      DIE("pos must be 0 or 1");
    }
  } else {
    msg = "In defined assignment subroutine '%s', dummy argument '%s'"
          " must be a data object"_err_en_US;
  }
  if (msg) {
    if (msg->IsFatal()) {
      SayWithDeclaration(symbol, std::move(*msg), symbol.name(), arg.name);
      context_.SetError(symbol);
      return false;
    } else {
      evaluate::AttachDeclaration(
          Warn(common::UsageWarning::DefinedOperatorArgs, std::move(*msg),
              symbol.name(), arg.name),
          symbol);
    }
  }
  return true;
}

// Report a conflicting attribute error if symbol has both of these attributes
bool CheckHelper::CheckConflicting(const Symbol &symbol, Attr a1, Attr a2) {
  if (symbol.attrs().test(a1) && symbol.attrs().test(a2)) {
    messages_.Say("'%s' may not have both the %s and %s attributes"_err_en_US,
        symbol.name(), AttrToString(a1), AttrToString(a2));
    return true;
  } else {
    return false;
  }
}

void CheckHelper::WarnMissingFinal(const Symbol &symbol) {
  const auto *object{symbol.detailsIf<ObjectEntityDetails>()};
  if (!object || object->IsAssumedRank() ||
      (!IsAutomaticallyDestroyed(symbol) &&
          symbol.owner().kind() != Scope::Kind::DerivedType)) {
    return;
  }
  const DeclTypeSpec *type{object->type()};
  const DerivedTypeSpec *derived{type ? type->AsDerived() : nullptr};
  const Symbol *derivedSym{derived ? &derived->typeSymbol() : nullptr};
  int rank{object->shape().Rank()};
  const Symbol *initialDerivedSym{derivedSym};
  while (const auto *derivedDetails{
      derivedSym ? derivedSym->detailsIf<DerivedTypeDetails>() : nullptr}) {
    if (!derivedDetails->finals().empty() &&
        !derivedDetails->GetFinalForRank(rank)) {
      if (auto *msg{derivedSym == initialDerivedSym
                  ? Warn(common::UsageWarning::Final, symbol.name(),
                        "'%s' of derived type '%s' does not have a FINAL subroutine for its rank (%d)"_warn_en_US,
                        symbol.name(), derivedSym->name(), rank)
                  : Warn(common::UsageWarning::Final, symbol.name(),
                        "'%s' of derived type '%s' extended from '%s' does not have a FINAL subroutine for its rank (%d)"_warn_en_US,
                        symbol.name(), initialDerivedSym->name(),
                        derivedSym->name(), rank)}) {
        msg->Attach(derivedSym->name(),
            "Declaration of derived type '%s'"_en_US, derivedSym->name());
      }
      return;
    }
    derived = derivedSym->GetParentTypeSpec();
    derivedSym = derived ? &derived->typeSymbol() : nullptr;
  }
}

const Procedure *CheckHelper::Characterize(const Symbol &symbol) {
  auto it{characterizeCache_.find(symbol)};
  if (it == characterizeCache_.end()) {
    auto pair{characterizeCache_.emplace(SymbolRef{symbol},
        Procedure::Characterize(symbol, context_.foldingContext()))};
    it = pair.first;
  }
  return common::GetPtrFromOptional(it->second);
}

void CheckHelper::CheckVolatile(const Symbol &symbol,
    const DerivedTypeSpec *derived) { // C866 - C868
  if (IsIntentIn(symbol)) {
    messages_.Say(
        "VOLATILE attribute may not apply to an INTENT(IN) argument"_err_en_US);
  }
  if (IsProcedure(symbol)) {
    messages_.Say("VOLATILE attribute may apply only to a variable"_err_en_US);
  }
  if (symbol.has<UseDetails>() || symbol.has<HostAssocDetails>()) {
    const Symbol &ultimate{symbol.GetUltimate()};
    if (evaluate::IsCoarray(ultimate)) {
      messages_.Say(
          "VOLATILE attribute may not apply to a coarray accessed by USE or host association"_err_en_US);
    }
    if (derived) {
      if (FindCoarrayUltimateComponent(*derived)) {
        messages_.Say(
            "VOLATILE attribute may not apply to a type with a coarray ultimate component accessed by USE or host association"_err_en_US);
      }
    }
  }
}

void CheckHelper::CheckContiguous(const Symbol &symbol) {
  if (evaluate::IsVariable(symbol) &&
      ((IsPointer(symbol) && symbol.Rank() > 0) || IsAssumedShape(symbol) ||
          IsAssumedRank(symbol))) {
  } else {
    parser::MessageFixedText msg{symbol.owner().IsDerivedType()
            ? "CONTIGUOUS component '%s' should be an array with the POINTER attribute"_port_en_US
            : "CONTIGUOUS entity '%s' should be an array pointer, assumed-shape, or assumed-rank"_port_en_US};
    if (!context_.IsEnabled(common::LanguageFeature::RedundantContiguous)) {
      msg.set_severity(parser::Severity::Error);
      messages_.Say(std::move(msg), symbol.name());
    } else {
      Warn(common::LanguageFeature::RedundantContiguous, std::move(msg),
          symbol.name());
    }
  }
}

void CheckHelper::CheckPointer(const Symbol &symbol) { // C852
  CheckConflicting(symbol, Attr::POINTER, Attr::TARGET);
  CheckConflicting(symbol, Attr::POINTER, Attr::ALLOCATABLE); // C751
  CheckConflicting(symbol, Attr::POINTER, Attr::INTRINSIC);
  // Prohibit constant pointers.  The standard does not explicitly prohibit
  // them, but the PARAMETER attribute requires a entity-decl to have an
  // initialization that is a constant-expr, and the only form of
  // initialization that allows a constant-expr is the one that's not a "=>"
  // pointer initialization.  See C811, C807, and section 8.5.13.
  CheckConflicting(symbol, Attr::POINTER, Attr::PARAMETER);
  if (symbol.Corank() > 0) {
    messages_.Say(
        "'%s' may not have the POINTER attribute because it is a coarray"_err_en_US,
        symbol.name());
  }
}

// C760 constraints on the passed-object dummy argument
// C757 constraints on procedure pointer components
void CheckHelper::CheckPassArg(
    const Symbol &proc, const Symbol *interface0, const WithPassArg &details) {
  if (proc.attrs().test(Attr::NOPASS)) {
    return;
  }
  const auto &name{proc.name()};
  const Symbol *interface {
    interface0 ? FindInterface(*interface0) : nullptr
  };
  if (!interface) {
    messages_.Say(name,
        "Procedure component '%s' must have NOPASS attribute or explicit interface"_err_en_US,
        name);
    return;
  }
  const auto *subprogram{interface->detailsIf<SubprogramDetails>()};
  if (!subprogram) {
    messages_.Say(name,
        "Procedure component '%s' has invalid interface '%s'"_err_en_US, name,
        interface->name());
    return;
  }
  std::optional<SourceName> passName{details.passName()};
  const auto &dummyArgs{subprogram->dummyArgs()};
  if (!passName) {
    if (dummyArgs.empty()) {
      messages_.Say(name,
          proc.has<ProcEntityDetails>()
              ? "Procedure component '%s' with no dummy arguments"
                " must have NOPASS attribute"_err_en_US
              : "Procedure binding '%s' with no dummy arguments"
                " must have NOPASS attribute"_err_en_US,
          name);
      context_.SetError(*interface);
      return;
    }
    Symbol *argSym{dummyArgs[0]};
    if (!argSym) {
      messages_.Say(interface->name(),
          "Cannot use an alternate return as the passed-object dummy "
          "argument"_err_en_US);
      return;
    }
    passName = dummyArgs[0]->name();
  }
  std::optional<int> passArgIndex{};
  for (std::size_t i{0}; i < dummyArgs.size(); ++i) {
    if (dummyArgs[i] && dummyArgs[i]->name() == *passName) {
      passArgIndex = i;
      break;
    }
  }
  if (!passArgIndex) { // C758
    messages_.Say(*passName,
        "'%s' is not a dummy argument of procedure interface '%s'"_err_en_US,
        *passName, interface->name());
    return;
  }
  const Symbol &passArg{*dummyArgs[*passArgIndex]};
  std::optional<parser::MessageFixedText> msg;
  if (!passArg.has<ObjectEntityDetails>()) {
    msg = "Passed-object dummy argument '%s' of procedure '%s'"
          " must be a data object"_err_en_US;
  } else if (passArg.attrs().test(Attr::ALLOCATABLE)) {
    msg = "Passed-object dummy argument '%s' of procedure '%s'"
          " may not have the ALLOCATABLE attribute"_err_en_US;
  } else if (passArg.attrs().test(Attr::VALUE)) {
    msg = "Passed-object dummy argument '%s' of procedure '%s'"
          " may not have the VALUE attribute"_err_en_US;
  } else if (passArg.Rank() > 0) {
    msg = "Passed-object dummy argument '%s' of procedure '%s'"
          " must be scalar"_err_en_US;
  } else if (passArg.attrs().test(Attr::POINTER)) {
    if (context_.IsEnabled(common::LanguageFeature::PointerPassObject) &&
        IsIntentIn(passArg)) {
      if (proc.has<ProcBindingDetails>()) {
        // Extension: allow a passed object to be an INTENT(IN) POINTER.
        // Only works for TBPs, needs lowering work for proc ptr components.
        Warn(common::LanguageFeature::PointerPassObject, name,
            "Passed-object dummy argument '%s' of procedure '%s' that is an INTENT(IN) POINTER is not standard"_port_en_US,
            *passName, name);
      } else {
        msg =
            "Passed-object dummy argument '%s' of procedure '%s' used as procedure pointer component interface may not have the POINTER attribute"_err_en_US;
      }
    } else {
      msg =
          "Passed-object dummy argument '%s' of procedure '%s' may not have the POINTER attribute unless INTENT(IN)"_err_en_US;
    }
  }
  if (msg) {
    messages_.Say(name, std::move(*msg), passName.value(), name);
    return;
  }
  const DeclTypeSpec *type{passArg.GetType()};
  if (!type) {
    return; // an error already occurred
  }
  const Symbol &typeSymbol{*proc.owner().GetSymbol()};
  const DerivedTypeSpec *derived{type->AsDerived()};
  if (!derived || derived->typeSymbol() != typeSymbol) {
    messages_.Say(name,
        "Passed-object dummy argument '%s' of procedure '%s'"
        " must be of type '%s' but is '%s'"_err_en_US,
        passName.value(), name, typeSymbol.name(), type->AsFortran());
    return;
  }
  if (IsExtensibleType(derived) != type->IsPolymorphic()) {
    messages_.Say(name,
        type->IsPolymorphic()
            ? "Passed-object dummy argument '%s' of procedure '%s'"
              " may not be polymorphic because '%s' is not extensible"_err_en_US
            : "Passed-object dummy argument '%s' of procedure '%s'"
              " must be polymorphic because '%s' is extensible"_err_en_US,
        passName.value(), name, typeSymbol.name());
    return;
  }
  for (const auto &[paramName, paramValue] : derived->parameters()) {
    if (paramValue.isLen() && !paramValue.isAssumed()) {
      messages_.Say(name,
          "Passed-object dummy argument '%s' of procedure '%s'"
          " has non-assumed length parameter '%s'"_err_en_US,
          passName.value(), name, paramName);
    }
  }
}

void CheckHelper::CheckProcBinding(
    const Symbol &symbol, const ProcBindingDetails &binding) {
  const Scope &dtScope{symbol.owner()};
  CHECK(dtScope.kind() == Scope::Kind::DerivedType);
  bool isInaccessibleDeferred{false};
  const Symbol *overridden{
      FindOverriddenBinding(symbol, isInaccessibleDeferred)};
  if (symbol.attrs().test(Attr::DEFERRED)) {
    if (const Symbol *dtSymbol{dtScope.symbol()}) {
      if (!dtSymbol->attrs().test(Attr::ABSTRACT)) { // C733
        SayWithDeclaration(*dtSymbol,
            "Procedure bound to non-ABSTRACT derived type '%s' may not be DEFERRED"_err_en_US,
            dtSymbol->name());
      }
    }
    if (symbol.attrs().test(Attr::NON_OVERRIDABLE)) {
      messages_.Say(
          "Type-bound procedure '%s' may not be both DEFERRED and NON_OVERRIDABLE"_err_en_US,
          symbol.name());
    }
    if (overridden && !overridden->attrs().test(Attr::DEFERRED)) {
      SayWithDeclaration(*overridden,
          "Override of non-DEFERRED '%s' must not be DEFERRED"_err_en_US,
          symbol.name());
    }
  }
  if (binding.symbol().attrs().test(Attr::INTRINSIC) &&
      !context_.intrinsics().IsSpecificIntrinsicFunction(
          binding.symbol().name().ToString())) {
    messages_.Say(
        "Intrinsic procedure '%s' is not a specific intrinsic permitted for use in the definition of binding '%s'"_err_en_US,
        binding.symbol().name(), symbol.name());
  }
  if (overridden) {
    if (isInaccessibleDeferred) {
      evaluate::AttachDeclaration(
          Warn(common::LanguageFeature::InaccessibleDeferredOverride,
              symbol.name(),
              "Override of PRIVATE DEFERRED '%s' should appear in its module"_warn_en_US,
              symbol.name()),
          *overridden);
    }
    if (overridden->attrs().test(Attr::NON_OVERRIDABLE)) {
      SayWithDeclaration(*overridden,
          "Override of NON_OVERRIDABLE '%s' is not permitted"_err_en_US,
          symbol.name());
    }
    if (const auto *overriddenBinding{
            overridden->detailsIf<ProcBindingDetails>()}) {
      if (!IsPureProcedure(symbol) && IsPureProcedure(*overridden)) {
        SayWithDeclaration(*overridden,
            "An overridden pure type-bound procedure binding must also be pure"_err_en_US);
        return;
      }
      if (!IsElementalProcedure(binding.symbol()) &&
          IsElementalProcedure(*overridden)) {
        SayWithDeclaration(*overridden,
            "A type-bound procedure and its override must both, or neither, be ELEMENTAL"_err_en_US);
        return;
      }
      bool isNopass{symbol.attrs().test(Attr::NOPASS)};
      if (isNopass != overridden->attrs().test(Attr::NOPASS)) {
        SayWithDeclaration(*overridden,
            isNopass
                ? "A NOPASS type-bound procedure may not override a passed-argument procedure"_err_en_US
                : "A passed-argument type-bound procedure may not override a NOPASS procedure"_err_en_US);
      } else {
        const auto *bindingChars{Characterize(symbol)};
        const auto *overriddenChars{Characterize(*overridden)};
        if (bindingChars && overriddenChars) {
          if (isNopass) {
            if (!bindingChars->CanOverride(*overriddenChars, std::nullopt)) {
              SayWithDeclaration(*overridden,
                  "A NOPASS type-bound procedure and its override must have identical interfaces"_err_en_US);
            }
          } else if (!context_.HasError(binding.symbol())) {
            auto passIndex{bindingChars->FindPassIndex(binding.passName())};
            auto overriddenPassIndex{
                overriddenChars->FindPassIndex(overriddenBinding->passName())};
            if (passIndex && overriddenPassIndex) {
              if (*passIndex != *overriddenPassIndex) {
                SayWithDeclaration(*overridden,
                    "A type-bound procedure and its override must use the same PASS argument"_err_en_US);
              } else if (!bindingChars->CanOverride(
                             *overriddenChars, passIndex)) {
                SayWithDeclaration(*overridden,
                    "A type-bound procedure and its override must have compatible interfaces"_err_en_US);
              }
            }
          }
        }
      }
      if (symbol.attrs().test(Attr::PRIVATE)) {
        if (FindModuleContaining(dtScope) ==
            FindModuleContaining(overridden->owner())) {
          // types declared in same madule
          if (!overridden->attrs().test(Attr::PRIVATE)) {
            SayWithDeclaration(*overridden,
                "A PRIVATE procedure may not override a PUBLIC procedure"_err_en_US);
          }
        } else { // types declared in distinct madules
          if (!CheckAccessibleSymbol(dtScope.parent(), *overridden)) {
            SayWithDeclaration(*overridden,
                "A PRIVATE procedure may not override an accessible procedure"_err_en_US);
          }
        }
      }
    } else {
      SayWithDeclaration(*overridden,
          "A type-bound procedure binding may not have the same name as a parent component"_err_en_US);
    }
  }
  CheckPassArg(symbol, &binding.symbol(), binding);
}

void CheckHelper::Check(const Scope &scope) {
  scope_ = &scope;
  common::Restorer<const Symbol *> restorer{innermostSymbol_, innermostSymbol_};
  if (const Symbol *symbol{scope.symbol()}) {
    innermostSymbol_ = symbol;
  }
  if (scope.IsParameterizedDerivedTypeInstantiation()) {
    auto restorer{common::ScopedSet(scopeIsUninstantiatedPDT_, false)};
    auto restorer2{context_.foldingContext().messages().SetContext(
        scope.instantiationContext().get())};
    for (const auto &pair : scope) {
      CheckPointerInitialization(*pair.second);
    }
  } else {
    auto restorer{common::ScopedSet(
        scopeIsUninstantiatedPDT_, scope.IsParameterizedDerivedType())};
    for (const auto &set : scope.equivalenceSets()) {
      CheckEquivalenceSet(set);
    }
    for (const auto &pair : scope) {
      Check(*pair.second);
    }
    if (scope.IsSubmodule() && scope.symbol()) {
      // Submodule names are not in their parent's scopes
      Check(*scope.symbol());
    }
    for (const auto &pair : scope.commonBlocks()) {
      CheckCommonBlock(*pair.second);
    }
    int mainProgCnt{0};
    for (const Scope &child : scope.children()) {
      Check(child);
      // A program shall consist of exactly one main program (5.2.2).
      if (child.kind() == Scope::Kind::MainProgram) {
        ++mainProgCnt;
        if (mainProgCnt > 1) {
          messages_.Say(child.sourceRange(),
              "A source file cannot contain more than one main program"_err_en_US);
        }
      }
    }
    if (scope.kind() == Scope::Kind::BlockData) {
      CheckBlockData(scope);
    }
    if (auto name{scope.GetName()}) {
      auto iter{scope.find(*name)};
      if (iter != scope.end()) {
        const char *kind{nullptr};
        switch (scope.kind()) {
        case Scope::Kind::Module:
          kind = scope.symbol()->get<ModuleDetails>().isSubmodule()
              ? "submodule"
              : "module";
          break;
        case Scope::Kind::MainProgram:
          kind = "main program";
          break;
        case Scope::Kind::BlockData:
          kind = "BLOCK DATA subprogram";
          break;
        default:;
        }
        if (kind) {
          Warn(common::LanguageFeature::BenignNameClash, iter->second->name(),
              "Name '%s' declared in a %s should not have the same name as the %s"_port_en_US,
              *name, kind, kind);
        }
      }
    }
    CheckGenericOps(scope);
  }
}

void CheckHelper::CheckEquivalenceSet(const EquivalenceSet &set) {
  auto iter{
      std::find_if(set.begin(), set.end(), [](const EquivalenceObject &object) {
        return FindCommonBlockContaining(object.symbol) != nullptr;
      })};
  if (iter != set.end()) {
    const Symbol &commonBlock{DEREF(FindCommonBlockContaining(iter->symbol))};
    for (auto &object : set) {
      if (&object != &*iter) {
        if (auto *details{object.symbol.detailsIf<ObjectEntityDetails>()}) {
          if (details->commonBlock()) {
            if (details->commonBlock() != &commonBlock) { // 8.10.3 paragraph 1
              if (auto *msg{messages_.Say(object.symbol.name(),
                      "Two objects in the same EQUIVALENCE set may not be members of distinct COMMON blocks"_err_en_US)}) {
                msg->Attach(iter->symbol.name(),
                       "Other object in EQUIVALENCE set"_en_US)
                    .Attach(details->commonBlock()->name(),
                        "COMMON block containing '%s'"_en_US,
                        object.symbol.name())
                    .Attach(commonBlock.name(),
                        "COMMON block containing '%s'"_en_US,
                        iter->symbol.name());
              }
            }
          } else {
            // Mark all symbols in the equivalence set with the same COMMON
            // block to prevent spurious error messages about initialization
            // in BLOCK DATA outside COMMON
            details->set_commonBlock(commonBlock);
          }
        }
      }
    }
  }
  for (const EquivalenceObject &object : set) {
    CheckEquivalenceObject(object);
  }
}

static bool InCommonWithBind(const Symbol &symbol) {
  if (const auto *details{symbol.detailsIf<ObjectEntityDetails>()}) {
    const Symbol *commonBlock{details->commonBlock()};
    return commonBlock && commonBlock->attrs().test(Attr::BIND_C);
  } else {
    return false;
  }
}

void CheckHelper::CheckEquivalenceObject(const EquivalenceObject &object) {
  parser::MessageFixedText msg;
  const Symbol &symbol{object.symbol};
  if (symbol.owner().IsDerivedType()) {
    msg =
        "Derived type component '%s' is not allowed in an equivalence set"_err_en_US;
  } else if (IsDummy(symbol)) {
    msg = "Dummy argument '%s' is not allowed in an equivalence set"_err_en_US;
  } else if (symbol.IsFuncResult()) {
    msg = "Function result '%s' is not allow in an equivalence set"_err_en_US;
  } else if (IsPointer(symbol)) {
    msg = "Pointer '%s' is not allowed in an equivalence set"_err_en_US;
  } else if (IsAllocatable(symbol)) {
    msg =
        "Allocatable variable '%s' is not allowed in an equivalence set"_err_en_US;
  } else if (symbol.Corank() > 0) {
    msg = "Coarray '%s' is not allowed in an equivalence set"_err_en_US;
  } else if (symbol.has<UseDetails>()) {
    msg =
        "Use-associated variable '%s' is not allowed in an equivalence set"_err_en_US;
  } else if (symbol.attrs().test(Attr::BIND_C)) {
    msg =
        "Variable '%s' with BIND attribute is not allowed in an equivalence set"_err_en_US;
  } else if (symbol.attrs().test(Attr::TARGET)) {
    msg =
        "Variable '%s' with TARGET attribute is not allowed in an equivalence set"_err_en_US;
  } else if (IsNamedConstant(symbol)) {
    msg = "Named constant '%s' is not allowed in an equivalence set"_err_en_US;
  } else if (InCommonWithBind(symbol)) {
    msg =
        "Variable '%s' in common block with BIND attribute is not allowed in an equivalence set"_err_en_US;
  } else if (!symbol.has<ObjectEntityDetails>()) {
    msg = "'%s' in equivalence set is not a data object"_err_en_US;
  } else if (const auto *type{symbol.GetType()}) {
    const auto *derived{type->AsDerived()};
    if (derived && !derived->IsVectorType()) {
      if (const auto *comp{
              FindUltimateComponent(*derived, IsAllocatableOrPointer)}) {
        msg = IsPointer(*comp)
            ? "Derived type object '%s' with pointer ultimate component is not allowed in an equivalence set"_err_en_US
            : "Derived type object '%s' with allocatable ultimate component is not allowed in an equivalence set"_err_en_US;
      } else if (!derived->typeSymbol().get<DerivedTypeDetails>().sequence()) {
        msg =
            "Nonsequence derived type object '%s' is not allowed in an equivalence set"_err_en_US;
      }
    } else if (IsAutomatic(symbol)) {
      msg =
          "Automatic object '%s' is not allowed in an equivalence set"_err_en_US;
    } else if (symbol.test(Symbol::Flag::CrayPointee)) {
      messages_.Say(object.symbol.name(),
          "Cray pointee '%s' may not be a member of an EQUIVALENCE group"_err_en_US,
          object.symbol.name());
    }
  }
  if (!msg.text().empty()) {
    context_.Say(object.source, std::move(msg), symbol.name());
  }
}

void CheckHelper::CheckBlockData(const Scope &scope) {
  // BLOCK DATA subprograms should contain only named common blocks.
  // C1415 presents a list of statements that shouldn't appear in
  // BLOCK DATA, but so long as the subprogram contains no executable
  // code and allocates no storage outside named COMMON, we're happy
  // (e.g., an ENUM is strictly not allowed).
  for (const auto &pair : scope) {
    const Symbol &symbol{*pair.second};
    if (!(symbol.has<CommonBlockDetails>() || symbol.has<UseDetails>() ||
            symbol.has<UseErrorDetails>() || symbol.has<DerivedTypeDetails>() ||
            symbol.has<SubprogramDetails>() ||
            symbol.has<ObjectEntityDetails>() ||
            (symbol.has<ProcEntityDetails>() &&
                !symbol.attrs().test(Attr::POINTER)))) {
      messages_.Say(symbol.name(),
          "'%s' may not appear in a BLOCK DATA subprogram"_err_en_US,
          symbol.name());
    }
  }
}

// Check distinguishability of generic assignment and operators.
// For these, generics and generic bindings must be considered together.
void CheckHelper::CheckGenericOps(const Scope &scope) {
  DistinguishabilityHelper helper{context_};
  auto addSpecifics{[&](const Symbol &generic) {
    if (!IsAccessible(generic, scope)) {
      return;
    }
    const auto *details{generic.GetUltimate().detailsIf<GenericDetails>()};
    if (!details) {
      // Not a generic; ensure characteristics are defined if a function.
      auto restorer{messages_.SetLocation(generic.name())};
      if (IsFunction(generic) && !context_.HasError(generic)) {
        if (const Symbol *result{FindFunctionResult(generic)};
            result && !context_.HasError(*result)) {
          Characterize(generic);
        }
      }
      return;
    }
    GenericKind kind{details->kind()};
    if (!kind.IsAssignment() && !kind.IsOperator()) {
      return;
    }
    const SymbolVector &specifics{details->specificProcs()};
    const std::vector<SourceName> &bindingNames{details->bindingNames()};
    for (std::size_t i{0}; i < specifics.size(); ++i) {
      const Symbol &specific{*specifics[i]};
      auto restorer{messages_.SetLocation(bindingNames[i])};
      if (const Procedure *proc{Characterize(specific)}) {
        if (kind.IsAssignment()) {
          if (!CheckDefinedAssignment(specific, *proc)) {
            continue;
          }
        } else {
          if (!CheckDefinedOperator(generic.name(), kind, specific, *proc)) {
            continue;
          }
        }
        helper.Add(generic, kind, specific, *proc);
      }
    }
  }};
  for (const auto &pair : scope) {
    const Symbol &symbol{*pair.second};
    addSpecifics(symbol);
    const Symbol &ultimate{symbol.GetUltimate()};
    if (ultimate.has<DerivedTypeDetails>()) {
      if (const Scope *typeScope{ultimate.scope()}) {
        for (const auto &pair2 : *typeScope) {
          addSpecifics(*pair2.second);
        }
      }
    }
  }
  helper.Check(scope);
}

static bool IsSubprogramDefinition(const Symbol &symbol) {
  const auto *subp{symbol.detailsIf<SubprogramDetails>()};
  return subp && !subp->isInterface() && symbol.scope() &&
      symbol.scope()->kind() == Scope::Kind::Subprogram;
}

static bool IsExternalProcedureDefinition(const Symbol &symbol) {
  return IsBlockData(symbol) ||
      ((IsSubprogramDefinition(symbol) || IsAlternateEntry(&symbol)) &&
          (IsExternal(symbol) || symbol.GetBindName()));
}

static std::optional<std::string> DefinesGlobalName(const Symbol &symbol) {
  if (const auto *module{symbol.detailsIf<ModuleDetails>()}) {
    if (!module->isSubmodule() && !symbol.owner().IsIntrinsicModules()) {
      return symbol.name().ToString();
    }
  } else if (IsBlockData(symbol)) {
    return symbol.name().ToString();
  } else {
    const std::string *bindC{symbol.GetBindName()};
    if (symbol.has<CommonBlockDetails>() ||
        IsExternalProcedureDefinition(symbol) ||
        (symbol.owner().IsGlobal() && IsExternal(symbol))) {
      return bindC ? *bindC : symbol.name().ToString();
    } else if (bindC &&
        (symbol.has<ObjectEntityDetails>() || IsModuleProcedure(symbol))) {
      return *bindC;
    }
  }
  return std::nullopt;
}

// 19.2 p2
void CheckHelper::CheckGlobalName(const Symbol &symbol) {
  if (auto global{DefinesGlobalName(symbol)}) {
    auto pair{globalNames_.emplace(std::move(*global), symbol)};
    if (!pair.second) {
      const Symbol &other{*pair.first->second};
      if (context_.HasError(symbol) || context_.HasError(other)) {
        // don't pile on
      } else if (symbol.has<CommonBlockDetails>() &&
          other.has<CommonBlockDetails>() && symbol.name() == other.name()) {
        // Two common blocks can have the same global name so long as
        // they're not in the same scope.
      } else if ((IsProcedure(symbol) || IsBlockData(symbol)) &&
          (IsProcedure(other) || IsBlockData(other)) &&
          (!IsExternalProcedureDefinition(symbol) ||
              !IsExternalProcedureDefinition(other))) {
        // both are procedures/BLOCK DATA, not both definitions
      } else if (AreSameModuleSymbol(symbol, other)) {
        // Both symbols are the same thing.
      } else if (symbol.has<ModuleDetails>()) {
        Warn(common::LanguageFeature::BenignNameClash, symbol.name(),
            "Module '%s' conflicts with a global name"_port_en_US,
            pair.first->first);
      } else if (other.has<ModuleDetails>()) {
        Warn(common::LanguageFeature::BenignNameClash, symbol.name(),
            "Global name '%s' conflicts with a module"_port_en_US,
            pair.first->first);
      } else if (auto *msg{messages_.Say(symbol.name(),
                     "Two entities have the same global name '%s'"_err_en_US,
                     pair.first->first)}) {
        msg->Attach(other.name(), "Conflicting declaration"_en_US);
        context_.SetError(symbol);
        context_.SetError(other);
      }
    }
  }
}

void CheckHelper::CheckProcedureAssemblyName(const Symbol &symbol) {
  if (!IsProcedure(symbol) || symbol != symbol.GetUltimate())
    return;
  const std::string *bindName{symbol.GetBindName()};
  const bool hasExplicitBindingLabel{
      symbol.GetIsExplicitBindName() && bindName};
  if (hasExplicitBindingLabel || IsExternal(symbol)) {
    const std::string assemblyName{hasExplicitBindingLabel
            ? *bindName
            : common::GetExternalAssemblyName(
                  symbol.name().ToString(), context_.underscoring())};
    auto pair{procedureAssemblyNames_.emplace(std::move(assemblyName), symbol)};
    if (!pair.second) {
      const Symbol &other{*pair.first->second};
      const bool otherHasExplicitBindingLabel{
          other.GetIsExplicitBindName() && other.GetBindName()};
      if (otherHasExplicitBindingLabel != hasExplicitBindingLabel) {
        // The BIND(C,NAME="...") binding label is the same as the name that
        // will be used in LLVM IR for an external procedure declared without
        // BIND(C) in the same file. While this is not forbidden by the
        // standard, this name collision would lead to a crash when producing
        // the IR.
        if (auto *msg{messages_.Say(symbol.name(),
                "%s procedure assembly name conflicts with %s procedure assembly name"_err_en_US,
                hasExplicitBindingLabel ? "BIND(C)" : "Non BIND(C)",
                hasExplicitBindingLabel ? "non BIND(C)" : "BIND(C)")}) {
          msg->Attach(other.name(), "Conflicting declaration"_en_US);
        }
        context_.SetError(symbol);
        context_.SetError(other);
      }
      // Otherwise, the global names also match and the conflict is analyzed
      // by CheckGlobalName.
    }
  }
}

parser::Messages CheckHelper::WhyNotInteroperableDerivedType(
    const Symbol &symbol) {
  parser::Messages msgs;
  if (examinedByWhyNotInteroperable_.find(symbol) !=
      examinedByWhyNotInteroperable_.end()) {
    return msgs;
  }
  examinedByWhyNotInteroperable_.insert(symbol);
  if (const auto *derived{symbol.detailsIf<DerivedTypeDetails>()}) {
    if (derived->sequence()) { // C1801
      msgs.Say(symbol.name(),
          "An interoperable derived type cannot have the SEQUENCE attribute"_err_en_US);
    } else if (!derived->paramNameOrder().empty()) { // C1802
      msgs.Say(symbol.name(),
          "An interoperable derived type cannot have a type parameter"_err_en_US);
    } else if (const auto *parent{
                   symbol.scope()->GetDerivedTypeParent()}) { // C1803
      if (symbol.attrs().test(Attr::BIND_C)) {
        msgs.Say(symbol.name(),
            "A derived type with the BIND attribute cannot be an extended derived type"_err_en_US);
      } else {
        bool interoperableParent{true};
        if (parent->symbol()) {
          auto bad{WhyNotInteroperableDerivedType(*parent->symbol())};
          if (bad.AnyFatalError()) {
            auto &msg{msgs.Say(symbol.name(),
                "The parent of an interoperable type is not interoperable"_err_en_US)};
            bad.AttachTo(msg, parser::Severity::None);
            interoperableParent = false;
          }
        }
        if (interoperableParent) {
          msgs.Say(symbol.name(),
              "An interoperable type should not be an extended derived type"_warn_en_US);
        }
      }
    }
    const Symbol *parentComponent{symbol.scope()
            ? derived->GetParentComponent(*symbol.scope())
            : nullptr};
    for (const auto &pair : *symbol.scope()) {
      const Symbol &component{*pair.second};
      if (&component == parentComponent) {
        continue; // was checked above
      }
      if (IsProcedure(component)) { // C1804
        msgs.Say(component.name(),
            "An interoperable derived type cannot have a type bound procedure"_err_en_US);
      } else if (IsAllocatableOrPointer(component)) { // C1806
        msgs.Say(component.name(),
            "An interoperable derived type cannot have a pointer or allocatable component"_err_en_US);
      } else if (const auto *type{component.GetType()}) {
        if (const auto *derived{type->AsDerived()}) {
          auto bad{WhyNotInteroperableDerivedType(derived->typeSymbol())};
          if (bad.AnyFatalError()) {
            auto &msg{msgs.Say(component.name(),
                "Component '%s' of an interoperable derived type must have an interoperable type but does not"_err_en_US,
                component.name())};
            bad.AttachTo(msg, parser::Severity::None);
          } else if (!derived->typeSymbol().GetUltimate().attrs().test(
                         Attr::BIND_C)) {
            auto &msg{
                msgs.Say(component.name(),
                        "Derived type of component '%s' of an interoperable derived type should have the BIND attribute"_warn_en_US,
                        component.name())
                    .Attach(derived->typeSymbol().name(),
                        "Non-BIND(C) component type"_en_US)};
            bad.AttachTo(msg, parser::Severity::None);
          } else {
            msgs.Annex(std::move(bad));
          }
        } else if (auto dyType{evaluate::DynamicType::From(*type)}; dyType &&
                   !evaluate::IsInteroperableIntrinsicType(
                       *dyType, &context_.languageFeatures())
                        .value_or(false)) {
          if (type->category() == DeclTypeSpec::Logical) {
            context().Warn(msgs, common::UsageWarning::LogicalVsCBool,
                component.name(),
                "A LOGICAL component of an interoperable type should have the interoperable KIND=C_BOOL"_port_en_US);
          } else if (type->category() == DeclTypeSpec::Character && dyType &&
              dyType->kind() == 1) {
            context().Warn(msgs, common::UsageWarning::BindCCharLength,
                component.name(),
                "A CHARACTER component of an interoperable type should have length 1"_port_en_US);
          } else {
            msgs.Say(component.name(),
                "Each component of an interoperable derived type must have an interoperable type"_err_en_US);
          }
        }
      }
      if (auto extents{
              evaluate::GetConstantExtents(foldingContext_, &component)};
          extents && evaluate::GetSize(*extents) == 0) {
        msgs.Say(component.name(),
            "An array component of an interoperable type must have at least one element"_err_en_US);
      }
    }
    if (derived->componentNames().empty()) { // F'2023 C1805
      context().Warn(msgs, common::LanguageFeature::EmptyBindCDerivedType,
          symbol.name(),
          "A derived type with the BIND attribute should not be empty"_warn_en_US);
    }
  }
  if (msgs.AnyFatalError()) {
    examinedByWhyNotInteroperable_.erase(symbol);
  }
  return msgs;
}

parser::Messages CheckHelper::WhyNotInteroperableObject(
    const Symbol &symbol, bool allowNonInteroperableType, bool forCommonBlock) {
  parser::Messages msgs;
  if (!forCommonBlock) {
    if (examinedByWhyNotInteroperable_.find(symbol) !=
        examinedByWhyNotInteroperable_.end()) {
      return msgs;
    }
    examinedByWhyNotInteroperable_.insert(symbol);
  }
  bool isExplicitBindC{symbol.attrs().test(Attr::BIND_C)};
  CHECK(symbol.has<ObjectEntityDetails>());
  if (isExplicitBindC && !symbol.owner().IsModule()) {
    msgs.Say(symbol.name(),
        "A variable with BIND(C) attribute may only appear in the specification part of a module"_err_en_US);
  }
  auto shape{evaluate::GetShape(foldingContext_, symbol)};
  if (shape) {
    if (evaluate::GetRank(*shape) == 0) { // 18.3.4
      if (IsAllocatableOrPointer(symbol) && !IsDummy(symbol)) {
        msgs.Say(symbol.name(),
            "A scalar interoperable variable may not be ALLOCATABLE or POINTER"_err_en_US);
      }
    } else if (auto extents{
                   evaluate::AsConstantExtents(foldingContext_, *shape)}) {
      if (evaluate::GetSize(*extents) == 0) {
        msgs.Say(symbol.name(),
            "Interoperable array must have at least one element"_err_en_US);
      }
    } else if (!evaluate::IsExplicitShape(symbol) &&
        !IsAssumedSizeArray(symbol) &&
        !(IsDummy(symbol) && !symbol.attrs().test(Attr::VALUE))) {
      msgs.Say(symbol.name(),
          "BIND(C) array must have explicit shape or be assumed-size unless a dummy argument without the VALUE attribute"_err_en_US);
    }
  }
  if (const auto *type{symbol.GetType()}) {
    const auto *derived{type->AsDerived()};
    if (derived && !derived->typeSymbol().attrs().test(Attr::BIND_C)) {
      if (allowNonInteroperableType) { // portability warning only
        evaluate::AttachDeclaration(
            Warn(common::UsageWarning::Portability, symbol.name(),
                "The derived type of this interoperable object should be BIND(C)"_port_en_US),
            derived->typeSymbol());
      } else if (!context_.IsEnabled(
                     common::LanguageFeature::NonBindCInteroperability)) {
        msgs.Say(symbol.name(),
                "The derived type of an interoperable object must be BIND(C)"_err_en_US)
            .Attach(derived->typeSymbol().name(), "Non-BIND(C) type"_en_US);
      } else if (auto bad{
                     WhyNotInteroperableDerivedType(derived->typeSymbol())};
                 bad.AnyFatalError()) {
        bad.AttachTo(
            msgs.Say(symbol.name(),
                    "The derived type of an interoperable object must be interoperable, but is not"_err_en_US)
                .Attach(derived->typeSymbol().name(),
                    "Non-interoperable type"_en_US),
            parser::Severity::None);
      } else {
        msgs.Say(symbol.name(),
                "The derived type of an interoperable object should be BIND(C)"_warn_en_US)
            .Attach(derived->typeSymbol().name(), "Non-BIND(C) type"_en_US);
      }
    }
    if (type->IsAssumedType()) { // ok
    } else if (IsAssumedLengthCharacter(symbol) &&
        !IsAllocatableOrPointer(symbol)) {
    } else if (IsAllocatableOrPointer(symbol) &&
        type->category() == DeclTypeSpec::Character &&
        type->characterTypeSpec().length().isDeferred()) {
      // ok; F'2023 18.3.7 p2(6)
    } else if (derived) { // type has been checked
    } else if (auto dyType{evaluate::DynamicType::From(*type)}; dyType &&
        evaluate::IsInteroperableIntrinsicType(
            *dyType, InModuleFile() ? nullptr : &context_.languageFeatures())
            .value_or(false)) {
      // F'2023 18.3.7 p2(4,5)
      // N.B. Language features are not passed to IsInteroperableIntrinsicType
      // when processing a module file, since the module file might have been
      // compiled with CUDA while the client is not.
    } else if (type->category() == DeclTypeSpec::Logical) {
      if (context_.ShouldWarn(common::UsageWarning::LogicalVsCBool)) {
        if (IsDummy(symbol)) {
          Warn(common::UsageWarning::LogicalVsCBool, symbol.name(),
              "A BIND(C) LOGICAL dummy argument should have the interoperable KIND=C_BOOL"_port_en_US);
        } else {
          Warn(common::UsageWarning::LogicalVsCBool, symbol.name(),
              "A BIND(C) LOGICAL object should have the interoperable KIND=C_BOOL"_port_en_US);
        }
      }
    } else if (symbol.attrs().test(Attr::VALUE)) {
      msgs.Say(symbol.name(),
          "A BIND(C) VALUE dummy argument must have an interoperable type"_err_en_US);
    } else {
      msgs.Say(symbol.name(),
          "A BIND(C) object must have an interoperable type"_err_en_US);
    }
  }
  if (IsOptional(symbol) && !symbol.attrs().test(Attr::VALUE)) {
    msgs.Say(symbol.name(),
        "An interoperable procedure with an OPTIONAL dummy argument might not be portable"_port_en_US);
  }
  if (IsDescriptor(symbol) && IsPointer(symbol) &&
      symbol.attrs().test(Attr::CONTIGUOUS)) {
    msgs.Say(symbol.name(),
        "An interoperable pointer must not be CONTIGUOUS"_err_en_US);
  }
  if (!forCommonBlock && msgs.AnyFatalError()) {
    examinedByWhyNotInteroperable_.erase(symbol);
  }
  return msgs;
}

parser::Messages CheckHelper::WhyNotInteroperableFunctionResult(
    const Symbol &symbol) {
  parser::Messages msgs;
  if (IsPointer(symbol) || IsAllocatable(symbol)) {
    msgs.Say(symbol.name(),
        "Interoperable function result may not have ALLOCATABLE or POINTER attribute"_err_en_US);
  }
  if (const DeclTypeSpec * type{symbol.GetType()};
      type && type->category() == DeclTypeSpec::Character) {
    bool isConstOne{false}; // 18.3.1(1)
    if (const auto &len{type->characterTypeSpec().length().GetExplicit()}) {
      if (auto constLen{evaluate::ToInt64(*len)}) {
        isConstOne = constLen == 1;
      }
    }
    if (!isConstOne) {
      msgs.Say(symbol.name(),
          "Interoperable character function result must have length one"_err_en_US);
    }
  }
  if (symbol.Rank() > 0) {
    msgs.Say(symbol.name(),
        "Interoperable function result must be scalar"_err_en_US);
  }
  return msgs;
}

parser::Messages CheckHelper::WhyNotInteroperableProcedure(
    const Symbol &symbol, bool isError) {
  parser::Messages msgs;
  if (examinedByWhyNotInteroperable_.find(symbol) !=
      examinedByWhyNotInteroperable_.end()) {
    return msgs;
  }
  isError |= symbol.attrs().test(Attr::BIND_C);
  examinedByWhyNotInteroperable_.insert(symbol);
  if (const auto *proc{symbol.detailsIf<ProcEntityDetails>()}) {
    if (isError) {
      if (!proc->procInterface() ||
          !proc->procInterface()->attrs().test(Attr::BIND_C)) {
        msgs.Say(symbol.name(),
            "An interface name with the BIND attribute must appear if the BIND attribute appears in a procedure declaration"_err_en_US);
      }
    } else if (!proc->procInterface()) {
      msgs.Say(symbol.name(),
          "An interoperable procedure should have an interface"_port_en_US);
    } else if (!proc->procInterface()->attrs().test(Attr::BIND_C)) {
      auto bad{WhyNotInteroperableProcedure(
          *proc->procInterface(), /*isError=*/false)};
      if (bad.AnyFatalError()) {
        bad.AttachTo(msgs.Say(symbol.name(),
            "An interoperable procedure must have an interoperable interface"_err_en_US));
      } else {
        msgs.Say(symbol.name(),
            "An interoperable procedure should have an interface with the BIND attribute"_warn_en_US);
      }
    }
  } else if (const auto *subp{symbol.detailsIf<SubprogramDetails>()}) {
    for (const Symbol *dummy : subp->dummyArgs()) {
      if (dummy) {
        parser::Messages dummyMsgs;
        if (dummy->has<ProcEntityDetails>() ||
            dummy->has<SubprogramDetails>()) {
          dummyMsgs = WhyNotInteroperableProcedure(*dummy, /*isError=*/false);
          if (dummyMsgs.empty() && !dummy->attrs().test(Attr::BIND_C)) {
            dummyMsgs.Say(dummy->name(),
                "A dummy procedure of an interoperable procedure should be BIND(C)"_warn_en_US);
          }
        } else if (dummy->has<ObjectEntityDetails>()) {
          // Emit only optional portability warnings for non-interoperable
          // types when the dummy argument is not VALUE and will be implemented
          // on the C side by either a cdesc_t * or a void *.  F'2023 18.3.7 (5)
          bool allowNonInteroperableType{!dummy->attrs().test(Attr::VALUE) &&
              (IsDescriptor(*dummy) || IsAssumedType(*dummy))};
          dummyMsgs = WhyNotInteroperableObject(
              *dummy, allowNonInteroperableType, /*forCommonBlock=*/false);
        } else {
          CheckBindC(*dummy);
        }
        msgs.Annex(std::move(dummyMsgs));
      } else {
        msgs.Say(symbol.name(),
            "A subprogram interface with the BIND attribute may not have an alternate return argument"_err_en_US);
      }
    }
    if (subp->isFunction()) {
      if (subp->result().has<ObjectEntityDetails>()) {
        msgs.Annex(WhyNotInteroperableFunctionResult(subp->result()));
      } else {
        msgs.Say(subp->result().name(),
            "The result of an interoperable function must be a data object"_err_en_US);
      }
    }
  }
  if (msgs.AnyFatalError()) {
    examinedByWhyNotInteroperable_.erase(symbol);
  }
  return msgs;
}

void CheckHelper::CheckBindC(const Symbol &symbol) {
  bool isExplicitBindC{symbol.attrs().test(Attr::BIND_C)};
  if (isExplicitBindC) {
    CheckConflicting(symbol, Attr::BIND_C, Attr::ELEMENTAL);
    CheckConflicting(symbol, Attr::BIND_C, Attr::INTRINSIC);
    CheckConflicting(symbol, Attr::BIND_C, Attr::PARAMETER);
  } else {
    // symbol must be interoperable (e.g., dummy argument of interoperable
    // procedure interface) but is not itself BIND(C).
  }
  parser::Messages whyNot;
  if (const std::string * bindName{symbol.GetBindName()};
      bindName) { // has a binding name
    if (!bindName->empty()) {
      bool ok{bindName->front() == '_' || parser::IsLetter(bindName->front())};
      for (char ch : *bindName) {
        ok &= ch == '_' || parser::IsLetter(ch) || parser::IsDecimalDigit(ch);
      }
      if (!ok) {
        messages_.Say(symbol.name(),
            "Symbol has a BIND(C) name that is not a valid C language identifier"_err_en_US);
        context_.SetError(symbol);
      }
    }
  }
  if (symbol.GetIsExplicitBindName()) { // BIND(C,NAME=...); C1552, C1529
    auto defClass{ClassifyProcedure(symbol)};
    if (IsProcedurePointer(symbol)) {
      messages_.Say(symbol.name(),
          "A procedure pointer may not have a BIND attribute with a name"_err_en_US);
      context_.SetError(symbol);
    } else if (defClass == ProcedureDefinitionClass::None ||
        IsExternal(symbol)) {
    } else if (symbol.attrs().test(Attr::ABSTRACT)) {
      messages_.Say(symbol.name(),
          "An ABSTRACT interface may not have a BIND attribute with a name"_err_en_US);
      context_.SetError(symbol);
    } else if (defClass == ProcedureDefinitionClass::Internal ||
        defClass == ProcedureDefinitionClass::Dummy) {
      messages_.Say(symbol.name(),
          "An internal or dummy procedure may not have a BIND(C,NAME=) binding label"_err_en_US);
      context_.SetError(symbol);
    }
  }
  if (symbol.has<ObjectEntityDetails>()) {
    whyNot = WhyNotInteroperableObject(symbol);
  } else if (symbol.has<ProcEntityDetails>() ||
      symbol.has<SubprogramDetails>()) {
    whyNot = WhyNotInteroperableProcedure(symbol, /*isError=*/isExplicitBindC);
  } else if (symbol.has<DerivedTypeDetails>()) {
    whyNot = WhyNotInteroperableDerivedType(symbol);
  }
  if (!whyNot.empty()) {
    bool anyFatal{whyNot.AnyFatalError()};
    if (anyFatal ||
        (!InModuleFile() &&
            context_.ShouldWarn(
                common::LanguageFeature::NonBindCInteroperability))) {
      context_.messages().Annex(std::move(whyNot));
    }
    if (anyFatal) {
      context_.SetError(symbol);
    }
  }
}

bool CheckHelper::CheckDioDummyIsData(
    const Symbol &subp, const Symbol *arg, std::size_t position) {
  if (arg && arg->detailsIf<ObjectEntityDetails>()) {
    if (IsAssumedRank(*arg)) {
      messages_.Say(arg->name(),
          "Dummy argument '%s' may not be assumed-rank"_err_en_US, arg->name());
      return false;
    } else {
      return true;
    }
  } else {
    if (arg) {
      messages_.Say(arg->name(),
          "Dummy argument '%s' must be a data object"_err_en_US, arg->name());
    } else {
      messages_.Say(subp.name(),
          "Dummy argument %d of '%s' must be a data object"_err_en_US, position,
          subp.name());
    }
    return false;
  }
}

void CheckHelper::CheckAlreadySeenDefinedIo(const DerivedTypeSpec &derivedType,
    common::DefinedIo ioKind, const Symbol &proc, const Symbol &generic) {
  // Check for conflict between non-type-bound defined I/O and type-bound
  // generics. It's okay to have two or more distinct defined I/O procedures for
  // the same type if they're coming from distinct non-type-bound interfaces.
  // (The non-type-bound interfaces would have been merged into a single generic
  //  -- with errors where indistinguishable --  when both were visible from the
  // same scope.)
  if (generic.owner().IsDerivedType()) {
    return;
  }
  if (const Scope * dtScope{derivedType.scope()}) {
    if (auto iter{dtScope->find(generic.name())}; iter != dtScope->end() &&
        IsAccessible(*iter->second, generic.owner())) {
      for (auto specRef : iter->second->get<GenericDetails>().specificProcs()) {
        const Symbol *specific{&specRef->get<ProcBindingDetails>().symbol()};
        if (specific == &proc) {
          continue; // unambiguous, accept
        }
        if (const auto *peDetails{specific->detailsIf<ProcEntityDetails>()}) {
          specific = peDetails->procInterface();
          if (!specific) {
            continue;
          }
        }
        if (const auto *specDT{GetDtvArgDerivedType(*specific)};
            specDT && evaluate::AreSameDerivedType(derivedType, *specDT)) {
          SayWithDeclaration(*specRef, proc.name(),
              "Derived type '%s' has conflicting type-bound input/output procedure '%s'"_err_en_US,
              derivedType.name(), GenericKind::AsFortran(ioKind));
          return;
        }
      }
    }
  }
}

void CheckHelper::CheckDioDummyIsDerived(const Symbol &proc, const Symbol &arg,
    common::DefinedIo ioKind, const Symbol &generic) {
  if (const DeclTypeSpec *type{arg.GetType()}) {
    if (const DerivedTypeSpec *derivedType{type->AsDerived()}) {
      CheckAlreadySeenDefinedIo(*derivedType, ioKind, proc, generic);
      bool isPolymorphic{type->IsPolymorphic()};
      if (isPolymorphic != IsExtensibleType(derivedType)) {
        messages_.Say(arg.name(),
            "Dummy argument '%s' of a defined input/output procedure must be %s when the derived type is %s"_err_en_US,
            arg.name(), isPolymorphic ? "TYPE()" : "CLASS()",
            isPolymorphic ? "not extensible" : "extensible");
      }
    } else {
      messages_.Say(arg.name(),
          "Dummy argument '%s' of a defined input/output procedure must have a derived type"_err_en_US,
          arg.name());
    }
  }
}

void CheckHelper::CheckDioDummyIsDefaultInteger(
    const Symbol &subp, const Symbol &arg) {
  if (const DeclTypeSpec *type{arg.GetType()};
      type && type->IsNumeric(TypeCategory::Integer)) {
    if (const auto kind{evaluate::ToInt64(type->numericTypeSpec().kind())};
        kind && *kind == context_.GetDefaultKind(TypeCategory::Integer)) {
      return;
    }
  }
  messages_.Say(arg.name(),
      "Dummy argument '%s' of a defined input/output procedure must be an INTEGER of default KIND"_err_en_US,
      arg.name());
}

void CheckHelper::CheckDioDummyIsScalar(const Symbol &subp, const Symbol &arg) {
  if (arg.Rank() > 0) {
    messages_.Say(arg.name(),
        "Dummy argument '%s' of a defined input/output procedure must be a scalar"_err_en_US,
        arg.name());
  }
}

void CheckHelper::CheckDioDtvArg(const Symbol &proc, const Symbol &subp,
    const Symbol *arg, common::DefinedIo ioKind, const Symbol &generic) {
  // Dtv argument looks like: dtv-type-spec, INTENT(INOUT) :: dtv
  if (CheckDioDummyIsData(subp, arg, 0)) {
    CheckDioDummyIsDerived(proc, *arg, ioKind, generic);
    CheckDioDummyAttrs(subp, *arg,
        ioKind == common::DefinedIo::ReadFormatted ||
                ioKind == common::DefinedIo::ReadUnformatted
            ? Attr::INTENT_INOUT
            : Attr::INTENT_IN);
    CheckDioDummyIsScalar(subp, *arg);
  }
}

// If an explicit INTRINSIC name is a function, so must all the specifics be,
// and similarly for subroutines
void CheckHelper::CheckGenericVsIntrinsic(
    const Symbol &symbol, const GenericDetails &generic) {
  if (symbol.attrs().test(Attr::INTRINSIC)) {
    const evaluate::IntrinsicProcTable &table{
        context_.foldingContext().intrinsics()};
    bool isSubroutine{table.IsIntrinsicSubroutine(symbol.name().ToString())};
    if (isSubroutine || table.IsIntrinsicFunction(symbol.name().ToString())) {
      for (const SymbolRef &ref : generic.specificProcs()) {
        const Symbol &ultimate{ref->GetUltimate()};
        bool specificFunc{ultimate.test(Symbol::Flag::Function)};
        bool specificSubr{ultimate.test(Symbol::Flag::Subroutine)};
        if (!specificFunc && !specificSubr) {
          if (const auto *proc{ultimate.detailsIf<SubprogramDetails>()}) {
            if (proc->isFunction()) {
              specificFunc = true;
            } else {
              specificSubr = true;
            }
          }
        }
        if ((specificFunc || specificSubr) &&
            isSubroutine != specificSubr) { // C848
          messages_.Say(symbol.name(),
              "Generic interface '%s' with explicit intrinsic %s of the same name may not have specific procedure '%s' that is a %s"_err_en_US,
              symbol.name(), isSubroutine ? "subroutine" : "function",
              ref->name(), isSubroutine ? "function" : "subroutine");
        }
      }
    }
  }
}

void CheckHelper::CheckDefaultIntegerArg(
    const Symbol &subp, const Symbol *arg, Attr intent) {
  // Argument looks like: INTEGER, INTENT(intent) :: arg
  if (CheckDioDummyIsData(subp, arg, 1)) {
    CheckDioDummyIsDefaultInteger(subp, *arg);
    CheckDioDummyIsScalar(subp, *arg);
    CheckDioDummyAttrs(subp, *arg, intent);
  }
}

void CheckHelper::CheckDioAssumedLenCharacterArg(const Symbol &subp,
    const Symbol *arg, std::size_t argPosition, Attr intent) {
  // Argument looks like: CHARACTER (LEN=*), INTENT(intent) :: (iotype OR iomsg)
  if (CheckDioDummyIsData(subp, arg, argPosition)) {
    CheckDioDummyAttrs(subp, *arg, intent);
    const DeclTypeSpec *type{arg ? arg->GetType() : nullptr};
    const IntrinsicTypeSpec *intrinsic{type ? type->AsIntrinsic() : nullptr};
    const auto kind{
        intrinsic ? evaluate::ToInt64(intrinsic->kind()) : std::nullopt};
    if (!IsAssumedLengthCharacter(*arg) ||
        (!kind ||
            *kind !=
                context_.defaultKinds().GetDefaultKind(
                    TypeCategory::Character))) {
      messages_.Say(arg->name(),
          "Dummy argument '%s' of a defined input/output procedure must be assumed-length CHARACTER of default kind"_err_en_US,
          arg->name());
    }
    CheckDioDummyIsScalar(subp, *arg);
  }
}

void CheckHelper::CheckDioVlistArg(
    const Symbol &subp, const Symbol *arg, std::size_t argPosition) {
  // Vlist argument looks like: INTEGER, INTENT(IN) :: v_list(:)
  if (CheckDioDummyIsData(subp, arg, argPosition)) {
    CheckDioDummyIsDefaultInteger(subp, *arg);
    CheckDioDummyAttrs(subp, *arg, Attr::INTENT_IN);
    const auto *objectDetails{arg->detailsIf<ObjectEntityDetails>()};
    if (!objectDetails || !objectDetails->shape().CanBeAssumedShape() ||
        objectDetails->shape().Rank() != 1) {
      messages_.Say(arg->name(),
          "Dummy argument '%s' of a defined input/output procedure must be assumed shape vector"_err_en_US,
          arg->name());
    }
  }
}

void CheckHelper::CheckDioArgCount(
    const Symbol &subp, common::DefinedIo ioKind, std::size_t argCount) {
  const std::size_t requiredArgCount{
      (std::size_t)(ioKind == common::DefinedIo::ReadFormatted ||
                  ioKind == common::DefinedIo::WriteFormatted
              ? 6
              : 4)};
  if (argCount != requiredArgCount) {
    SayWithDeclaration(subp,
        "Defined input/output procedure '%s' must have %d dummy arguments rather than %d"_err_en_US,
        subp.name(), requiredArgCount, argCount);
    context_.SetError(subp);
  }
}

void CheckHelper::CheckDioDummyAttrs(
    const Symbol &subp, const Symbol &arg, Attr goodIntent) {
  // Defined I/O procedures can't have attributes other than INTENT
  Attrs attrs{arg.attrs()};
  if (!attrs.test(goodIntent)) {
    messages_.Say(arg.name(),
        "Dummy argument '%s' of a defined input/output procedure must have intent '%s'"_err_en_US,
        arg.name(), AttrToString(goodIntent));
  }
  attrs = attrs - Attr::INTENT_IN - Attr::INTENT_OUT - Attr::INTENT_INOUT;
  if (!attrs.empty()) {
    messages_.Say(arg.name(),
        "Dummy argument '%s' of a defined input/output procedure may not have any attributes"_err_en_US,
        arg.name());
  }
}

// Enforce semantics for defined input/output procedures (12.6.4.8.2) and C777
void CheckHelper::CheckDefinedIoProc(const Symbol &symbol,
    const GenericDetails &details, common::DefinedIo ioKind) {
  for (auto ref : details.specificProcs()) {
    const Symbol &ultimate{ref->GetUltimate()};
    const auto *binding{ultimate.detailsIf<ProcBindingDetails>()};
    if (ultimate.attrs().test(Attr::NOPASS)) { // C774
      messages_.Say(
          "Defined input/output procedure '%s' may not have NOPASS attribute"_err_en_US,
          ultimate.name());
      context_.SetError(ultimate);
    }
    const Symbol *specificProc{binding ? &binding->symbol() : &ultimate};
    const Symbol *specificSubp{specificProc};
    if (const auto *peDetails{specificSubp->detailsIf<ProcEntityDetails>()}) {
      specificSubp = peDetails->procInterface();
      if (!specificSubp) {
        continue;
      }
    }
    if (const auto *subpDetails{specificSubp->detailsIf<SubprogramDetails>()}) {
      const std::vector<Symbol *> &dummyArgs{subpDetails->dummyArgs()};
      CheckDioArgCount(*specificSubp, ioKind, dummyArgs.size());
      int argCount{0};
      for (auto *arg : dummyArgs) {
        if (arg && arg->Corank() > 0) {
          evaluate::AttachDeclaration(
              messages_.Say(arg->name(),
                  "Dummy argument '%s' of defined input/output procedure '%s' may not be a coarray"_err_en_US,
                  arg->name(), ultimate.name()),
              *arg);
        }
        switch (argCount++) {
        case 0:
          // dtv-type-spec, INTENT(INOUT) :: dtv
          CheckDioDtvArg(*specificProc, *specificSubp, arg, ioKind, symbol);
          break;
        case 1:
          // INTEGER, INTENT(IN) :: unit
          CheckDefaultIntegerArg(*specificSubp, arg, Attr::INTENT_IN);
          break;
        case 2:
          if (ioKind == common::DefinedIo::ReadFormatted ||
              ioKind == common::DefinedIo::WriteFormatted) {
            // CHARACTER (LEN=*), INTENT(IN) :: iotype
            CheckDioAssumedLenCharacterArg(
                *specificSubp, arg, argCount, Attr::INTENT_IN);
          } else {
            // INTEGER, INTENT(OUT) :: iostat
            CheckDefaultIntegerArg(*specificSubp, arg, Attr::INTENT_OUT);
          }
          break;
        case 3:
          if (ioKind == common::DefinedIo::ReadFormatted ||
              ioKind == common::DefinedIo::WriteFormatted) {
            // INTEGER, INTENT(IN) :: v_list(:)
            CheckDioVlistArg(*specificSubp, arg, argCount);
          } else {
            // CHARACTER (LEN=*), INTENT(INOUT) :: iomsg
            CheckDioAssumedLenCharacterArg(
                *specificSubp, arg, argCount, Attr::INTENT_INOUT);
          }
          break;
        case 4:
          // INTEGER, INTENT(OUT) :: iostat
          CheckDefaultIntegerArg(*specificSubp, arg, Attr::INTENT_OUT);
          break;
        case 5:
          // CHARACTER (LEN=*), INTENT(INOUT) :: iomsg
          CheckDioAssumedLenCharacterArg(
              *specificSubp, arg, argCount, Attr::INTENT_INOUT);
          break;
        default:;
        }
      }
    }
  }
}

void CheckHelper::CheckSymbolType(const Symbol &symbol) {
  const Symbol *result{FindFunctionResult(symbol)};
  const Symbol &relevant{result ? *result : symbol};
  if (IsAllocatable(relevant)) { // always ok
  } else if (IsProcedurePointer(symbol) && result && IsPointer(*result)) {
    // procedure pointer returning allocatable or pointer: ok
  } else if (IsPointer(relevant) && !IsProcedure(relevant)) {
    // object pointers are always ok
  } else if (auto dyType{evaluate::DynamicType::From(relevant)}) {
    if (dyType->IsPolymorphic() && !dyType->IsAssumedType() &&
        !(IsDummy(symbol) && !IsProcedure(relevant))) { // C708
      if (IsProcedure(symbol)) {
        messages_.Say(
            "Polymorphic function%s '%s' must have an explicit interface whose result is ALLOCATABLE or POINTER"_err_en_US,
            IsPointer(symbol) ? " pointer" : "", symbol.name());
      } else {
        messages_.Say(
            "CLASS entity '%s' must be a dummy argument, allocatable, or object pointer"_err_en_US,
            symbol.name());
      }
    }
    if (dyType->HasDeferredTypeParameter()) { // C702
      messages_.Say(
          "'%s' has a type %s with a deferred type parameter but is neither an allocatable nor an object pointer"_err_en_US,
          symbol.name(), dyType->AsFortran());
    }
    if (!symbol.has<ObjectEntityDetails>()) {
      if (const DerivedTypeSpec *
          derived{evaluate::GetDerivedTypeSpec(*dyType)}) {
        if (IsEventTypeOrLockType(derived)) {
          messages_.Say(
              "Entity '%s' with EVENT_TYPE or LOCK_TYPE must be an object"_err_en_US,
              symbol.name());
        } else if (auto iter{FindEventOrLockPotentialComponent(*derived)}) {
          messages_.Say(
              "Entity '%s' with EVENT_TYPE or LOCK_TYPE potential subobject component '%s' must be an object"_err_en_US,
              symbol.name(), iter.BuildResultDesignatorName());
        }
      }
    }
  }
}

void CheckHelper::CheckModuleProcedureDef(const Symbol &symbol) {
  auto procClass{ClassifyProcedure(symbol)};
  if (const auto *subprogram{symbol.detailsIf<SubprogramDetails>()};
      subprogram &&
      (procClass == ProcedureDefinitionClass::Module &&
          symbol.attrs().test(Attr::MODULE)) &&
      !subprogram->bindName() && !subprogram->isInterface()) {
    const Symbol &interface {
      subprogram->moduleInterface() ? *subprogram->moduleInterface() : symbol
    };
    if (const Symbol *
            module{interface.owner().kind() == Scope::Kind::Module
                    ? interface.owner().symbol()
                    : nullptr};
        module && module->has<ModuleDetails>()) {
      std::pair<SourceName, const Symbol *> key{symbol.name(), module};
      auto iter{moduleProcs_.find(key)};
      if (iter == moduleProcs_.end()) {
        moduleProcs_.emplace(std::move(key), symbol);
      } else if (
          auto *msg{messages_.Say(symbol.name(),
              "Module procedure '%s' in '%s' has multiple definitions"_err_en_US,
              symbol.name(), GetModuleOrSubmoduleName(*module))}) {
        msg->Attach(iter->second->name(), "Previous definition of '%s'"_en_US,
            symbol.name());
      }
    }
  }
}

void SubprogramMatchHelper::Check(
    const Symbol &symbol1, const Symbol &symbol2) {
  const auto details1{symbol1.get<SubprogramDetails>()};
  const auto details2{symbol2.get<SubprogramDetails>()};
  if (details1.isFunction() != details2.isFunction()) {
    Say(symbol1, symbol2,
        details1.isFunction()
            ? "Module function '%s' was declared as a subroutine in the"
              " corresponding interface body"_err_en_US
            : "Module subroutine '%s' was declared as a function in the"
              " corresponding interface body"_err_en_US);
    return;
  }
  const auto &args1{details1.dummyArgs()};
  const auto &args2{details2.dummyArgs()};
  int nargs1{static_cast<int>(args1.size())};
  int nargs2{static_cast<int>(args2.size())};
  if (nargs1 != nargs2) {
    Say(symbol1, symbol2,
        "Module subprogram '%s' has %d args but the corresponding interface"
        " body has %d"_err_en_US,
        nargs1, nargs2);
    return;
  }
  bool nonRecursive1{symbol1.attrs().test(Attr::NON_RECURSIVE)};
  if (nonRecursive1 != symbol2.attrs().test(Attr::NON_RECURSIVE)) { // C1551
    Say(symbol1, symbol2,
        nonRecursive1
            ? "Module subprogram '%s' has NON_RECURSIVE prefix but"
              " the corresponding interface body does not"_err_en_US
            : "Module subprogram '%s' does not have NON_RECURSIVE prefix but "
              "the corresponding interface body does"_err_en_US);
  }
  const std::string *bindName1{details1.bindName()};
  const std::string *bindName2{details2.bindName()};
  if (!bindName1 && !bindName2) {
    // OK - neither has a binding label
  } else if (!bindName1) {
    Say(symbol1, symbol2,
        "Module subprogram '%s' does not have a binding label but the"
        " corresponding interface body does"_err_en_US);
  } else if (!bindName2) {
    Say(symbol1, symbol2,
        "Module subprogram '%s' has a binding label but the"
        " corresponding interface body does not"_err_en_US);
  } else if (*bindName1 != *bindName2) {
    Say(symbol1, symbol2,
        "Module subprogram '%s' has binding label '%s' but the corresponding"
        " interface body has '%s'"_err_en_US,
        *details1.bindName(), *details2.bindName());
  }
  const Procedure *proc1{checkHelper.Characterize(symbol1)};
  const Procedure *proc2{checkHelper.Characterize(symbol2)};
  if (!proc1 || !proc2) {
    return;
  }
  if (proc1->attrs.test(Procedure::Attr::Pure) !=
      proc2->attrs.test(Procedure::Attr::Pure)) {
    Say(symbol1, symbol2,
        "Module subprogram '%s' and its corresponding interface body are not both PURE"_err_en_US);
  }
  if (proc1->attrs.test(Procedure::Attr::Elemental) !=
      proc2->attrs.test(Procedure::Attr::Elemental)) {
    Say(symbol1, symbol2,
        "Module subprogram '%s' and its corresponding interface body are not both ELEMENTAL"_err_en_US);
  }
  if (proc1->attrs.test(Procedure::Attr::BindC) !=
      proc2->attrs.test(Procedure::Attr::BindC)) {
    Say(symbol1, symbol2,
        "Module subprogram '%s' and its corresponding interface body are not both BIND(C)"_err_en_US);
  }
  if (proc1->functionResult && proc2->functionResult) {
    std::string whyNot;
    if (!proc1->functionResult->IsCompatibleWith(
            *proc2->functionResult, &whyNot)) {
      Say(symbol1, symbol2,
          "Result of function '%s' is not compatible with the result of the corresponding interface body: %s"_err_en_US,
          whyNot);
    }
  }
  for (int i{0}; i < nargs1; ++i) {
    const Symbol *arg1{args1[i]};
    const Symbol *arg2{args2[i]};
    if (arg1 && !arg2) {
      Say(symbol1, symbol2,
          "Dummy argument %2$d of '%1$s' is not an alternate return indicator"
          " but the corresponding argument in the interface body is"_err_en_US,
          i + 1);
    } else if (!arg1 && arg2) {
      Say(symbol1, symbol2,
          "Dummy argument %2$d of '%1$s' is an alternate return indicator but"
          " the corresponding argument in the interface body is not"_err_en_US,
          i + 1);
    } else if (arg1 && arg2) {
      SourceName name1{arg1->name()};
      SourceName name2{arg2->name()};
      if (name1 != name2) {
        Say(*arg1, *arg2,
            "Dummy argument name '%s' does not match corresponding name '%s'"
            " in interface body"_err_en_US,
            name2);
      } else {
        CheckDummyArg(
            *arg1, *arg2, proc1->dummyArguments[i], proc2->dummyArguments[i]);
      }
    }
  }
}

void SubprogramMatchHelper::CheckDummyArg(const Symbol &symbol1,
    const Symbol &symbol2, const DummyArgument &arg1,
    const DummyArgument &arg2) {
  common::visit(
      common::visitors{
          [&](const DummyDataObject &obj1, const DummyDataObject &obj2) {
            CheckDummyDataObject(symbol1, symbol2, obj1, obj2);
          },
          [&](const DummyProcedure &proc1, const DummyProcedure &proc2) {
            CheckDummyProcedure(symbol1, symbol2, proc1, proc2);
          },
          [&](const DummyDataObject &, const auto &) {
            Say(symbol1, symbol2,
                "Dummy argument '%s' is a data object; the corresponding"
                " argument in the interface body is not"_err_en_US);
          },
          [&](const DummyProcedure &, const auto &) {
            Say(symbol1, symbol2,
                "Dummy argument '%s' is a procedure; the corresponding"
                " argument in the interface body is not"_err_en_US);
          },
          [&](const auto &, const auto &) {
            llvm_unreachable("Dummy arguments are not data objects or"
                             "procedures");
          },
      },
      arg1.u, arg2.u);
}

void SubprogramMatchHelper::CheckDummyDataObject(const Symbol &symbol1,
    const Symbol &symbol2, const DummyDataObject &obj1,
    const DummyDataObject &obj2) {
  if (!CheckSameIntent(symbol1, symbol2, obj1.intent, obj2.intent)) {
  } else if (!CheckSameAttrs(symbol1, symbol2, obj1.attrs, obj2.attrs)) {
  } else if (!obj1.type.type().IsEquivalentTo(obj2.type.type())) {
    Say(symbol1, symbol2,
        "Dummy argument '%s' has type %s; the corresponding argument in the interface body has distinct type %s"_err_en_US,
        obj1.type.type().AsFortran(), obj2.type.type().AsFortran());
  } else if (!ShapesAreCompatible(obj1, obj2)) {
    Say(symbol1, symbol2,
        "The shape of dummy argument '%s' does not match the shape of the"
        " corresponding argument in the interface body"_err_en_US);
  }
  // TODO: coshape
}

void SubprogramMatchHelper::CheckDummyProcedure(const Symbol &symbol1,
    const Symbol &symbol2, const DummyProcedure &proc1,
    const DummyProcedure &proc2) {
  std::string whyNot;
  if (!CheckSameIntent(symbol1, symbol2, proc1.intent, proc2.intent)) {
  } else if (!CheckSameAttrs(symbol1, symbol2, proc1.attrs, proc2.attrs)) {
  } else if (!proc2.IsCompatibleWith(proc1, &whyNot)) {
    Say(symbol1, symbol2,
        "Dummy procedure '%s' is not compatible with the corresponding argument in the interface body: %s"_err_en_US,
        whyNot);
  } else if (proc1 != proc2) {
    evaluate::AttachDeclaration(
        symbol1.owner().context().Warn(
            common::UsageWarning::MismatchingDummyProcedure,
            "Dummy procedure '%s' does not exactly match the corresponding argument in the interface body"_warn_en_US,
            symbol1.name()),
        symbol2);
  }
}

bool SubprogramMatchHelper::CheckSameIntent(const Symbol &symbol1,
    const Symbol &symbol2, common::Intent intent1, common::Intent intent2) {
  if (intent1 == intent2) {
    return true;
  } else {
    Say(symbol1, symbol2,
        "The intent of dummy argument '%s' does not match the intent"
        " of the corresponding argument in the interface body"_err_en_US);
    return false;
  }
}

// Report an error referring to first symbol with declaration of second symbol
template <typename... A>
void SubprogramMatchHelper::Say(const Symbol &symbol1, const Symbol &symbol2,
    parser::MessageFixedText &&text, A &&...args) {
  auto &message{context().Say(symbol1.name(), std::move(text), symbol1.name(),
      std::forward<A>(args)...)};
  evaluate::AttachDeclaration(message, symbol2);
}

template <typename ATTRS>
bool SubprogramMatchHelper::CheckSameAttrs(
    const Symbol &symbol1, const Symbol &symbol2, ATTRS attrs1, ATTRS attrs2) {
  if (attrs1 == attrs2) {
    return true;
  }
  attrs1.IterateOverMembers([&](auto attr) {
    if (!attrs2.test(attr)) {
      Say(symbol1, symbol2,
          "Dummy argument '%s' has the %s attribute; the corresponding"
          " argument in the interface body does not"_err_en_US,
          AsFortran(attr));
    }
  });
  attrs2.IterateOverMembers([&](auto attr) {
    if (!attrs1.test(attr)) {
      Say(symbol1, symbol2,
          "Dummy argument '%s' does not have the %s attribute; the"
          " corresponding argument in the interface body does"_err_en_US,
          AsFortran(attr));
    }
  });
  return false;
}

bool SubprogramMatchHelper::ShapesAreCompatible(
    const DummyDataObject &obj1, const DummyDataObject &obj2) {
  return characteristics::ShapesAreCompatible(
      FoldShape(obj1.type.shape()), FoldShape(obj2.type.shape()));
}

evaluate::Shape SubprogramMatchHelper::FoldShape(const evaluate::Shape &shape) {
  evaluate::Shape result;
  for (const auto &extent : shape) {
    result.emplace_back(
        evaluate::Fold(context().foldingContext(), common::Clone(extent)));
  }
  return result;
}

void DistinguishabilityHelper::Add(const Symbol &generic, GenericKind kind,
    const Symbol &specific, const Procedure &procedure) {
  const Symbol &ultimate{specific.GetUltimate()};
  if (!context_.HasError(ultimate)) {
    nameToSpecifics_[generic.name()].emplace(
        &ultimate, ProcedureInfo{kind, procedure});
  }
}

void DistinguishabilityHelper::Check(const Scope &scope) {
  if (FindModuleFileContaining(scope)) {
    // Distinguishability was checked when the module was created;
    // don't let optional warnings then become errors now.
    return;
  }
  for (const auto &[name, info] : nameToSpecifics_) {
    for (auto iter1{info.begin()}; iter1 != info.end(); ++iter1) {
      const auto &[ultimate, procInfo]{*iter1};
      const auto &[kind, proc]{procInfo};
      for (auto iter2{iter1}; ++iter2 != info.end();) {
        const auto &[ultimate2, procInfo2]{*iter2};
        if (&*ultimate == &*ultimate2) {
          continue; // ok, actually the same procedure/binding
        } else if (const auto *binding1{
                       ultimate->detailsIf<ProcBindingDetails>()}) {
          if (const auto *binding2{
                  ultimate2->detailsIf<ProcBindingDetails>()}) {
            if (&binding1->symbol().GetUltimate() ==
                &binding2->symbol().GetUltimate()) {
              continue; // ok, (NOPASS) bindings resolve identically
            } else if (ultimate->name() == ultimate2->name()) {
              continue; // override, possibly of DEFERRED
            }
          }
        } else if (ultimate->has<ProcBindingDetails>() &&
            ultimate2->has<ProcBindingDetails>() &&
            ultimate->name() == ultimate2->name()) {
          continue; // override, possibly of DEFERRED
        }
        auto distinguishable{kind.IsName()
                ? evaluate::characteristics::Distinguishable
                : evaluate::characteristics::DistinguishableOpOrAssign};
        std::optional<bool> distinct{distinguishable(
            context_.languageFeatures(), proc, procInfo2.procedure)};
        if (!distinct.value_or(false)) {
          SayNotDistinguishable(GetTopLevelUnitContaining(scope), name, kind,
              *ultimate, *ultimate2, distinct.has_value());
        }
      }
    }
  }
}

void DistinguishabilityHelper::SayNotDistinguishable(const Scope &scope,
    const SourceName &name, GenericKind kind, const Symbol &proc1,
    const Symbol &proc2, bool isHardConflict) {
  bool isUseAssociated{!scope.sourceRange().Contains(name)};
  // The rules for distinguishing specific procedures (F'2023 15.4.3.4.5)
  // are inadequate for some real-world cases like pFUnit.
  // When there are optional dummy arguments or unlimited polymorphic
  // dummy data object arguments, the best that we can do is emit an optional
  // portability warning.  Also, named generics created by USE association
  // merging shouldn't receive hard errors for ambiguity.
  // (Non-named generics might be defined I/O procedures or defined
  // assignments that need to be used by the runtime.)
  bool isWarning{!isHardConflict || (isUseAssociated && kind.IsName())};
  if (isWarning &&
      (!context_.ShouldWarn(
           common::LanguageFeature::IndistinguishableSpecifics) ||
          FindModuleFileContaining(scope))) {
    return;
  }
  std::string name1{proc1.name().ToString()};
  std::string name2{proc2.name().ToString()};
  if (kind.IsOperator() || kind.IsAssignment()) {
    // proc1 and proc2 may come from different scopes so qualify their names
    if (proc1.owner().IsDerivedType()) {
      name1 = proc1.owner().GetName()->ToString() + '%' + name1;
    }
    if (proc2.owner().IsDerivedType()) {
      name2 = proc2.owner().GetName()->ToString() + '%' + name2;
    }
  }
  parser::Message *msg;
  if (!isUseAssociated) {
    CHECK(isWarning == !isHardConflict);
    msg = &context_.Say(name,
        isHardConflict
            ? "Generic '%s' may not have specific procedures '%s' and '%s' as their interfaces are not distinguishable"_err_en_US
            : "Generic '%s' should not have specific procedures '%s' and '%s' as their interfaces are not distinguishable by the rules in the standard"_port_en_US,
        MakeOpName(name), name1, name2);
  } else {
    msg = &context_.Say(*GetTopLevelUnitContaining(proc1).GetName(),
        isHardConflict
            ? (isWarning
                      ? "USE-associated generic '%s' should not have specific procedures '%s' and '%s' as their interfaces are not distinguishable"_warn_en_US
                      : "USE-associated generic '%s' may not have specific procedures '%s' and '%s' as their interfaces are not distinguishable"_err_en_US)
            : "USE-associated generic '%s' should not have specific procedures '%s' and '%s' as their interfaces are not distinguishable by the rules in the standard"_port_en_US,
        MakeOpName(name), name1, name2);
  }
  AttachDeclaration(*msg, scope, proc1);
  AttachDeclaration(*msg, scope, proc2);
}

// `evaluate::AttachDeclaration` doesn't handle the generic case where `proc`
// comes from a different module but is not necessarily use-associated.
void DistinguishabilityHelper::AttachDeclaration(
    parser::Message &msg, const Scope &scope, const Symbol &proc) {
  if (proc.owner().IsTopLevel()) {
    evaluate::AttachDeclaration(msg, proc);
  } else {
    const Scope &unit{GetTopLevelUnitContaining(proc)};
    if (unit == scope) {
      evaluate::AttachDeclaration(msg, proc);
    } else {
      msg.Attach(unit.GetName().value(),
          "'%s' is USE-associated from module '%s'"_en_US, proc.name(),
          unit.GetName().value());
    }
  }
}

void CheckDeclarations(SemanticsContext &context) {
  CheckHelper{context}.Check();
}
} // namespace Fortran::semantics