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//===--- InlayHints.cpp ------------------------------------------*- C++-*-===//
//
// 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
//
//===----------------------------------------------------------------------===//
#include "InlayHints.h"
#include "Config.h"
#include "HeuristicResolver.h"
#include "ParsedAST.h"
#include "clang/AST/DeclarationName.h"
#include "clang/AST/ExprCXX.h"
#include "clang/AST/RecursiveASTVisitor.h"
#include "clang/Basic/SourceManager.h"
#include "llvm/ADT/ScopeExit.h"
namespace clang {
namespace clangd {
namespace {
// For now, inlay hints are always anchored at the left or right of their range.
enum class HintSide { Left, Right };
// Helper class to iterate over the designator names of an aggregate type.
//
// For an array type, yields [0], [1], [2]...
// For aggregate classes, yields null for each base, then .field1, .field2, ...
class AggregateDesignatorNames {
public:
AggregateDesignatorNames(QualType T) {
if (!T.isNull()) {
T = T.getCanonicalType();
if (T->isArrayType()) {
IsArray = true;
Valid = true;
return;
}
if (const RecordDecl *RD = T->getAsRecordDecl()) {
Valid = true;
FieldsIt = RD->field_begin();
FieldsEnd = RD->field_end();
if (const auto *CRD = llvm::dyn_cast<CXXRecordDecl>(RD)) {
BasesIt = CRD->bases_begin();
BasesEnd = CRD->bases_end();
Valid = CRD->isAggregate();
}
OneField = Valid && BasesIt == BasesEnd && FieldsIt != FieldsEnd &&
std::next(FieldsIt) == FieldsEnd;
}
}
}
// Returns false if the type was not an aggregate.
operator bool() { return Valid; }
// Advance to the next element in the aggregate.
void next() {
if (IsArray)
++Index;
else if (BasesIt != BasesEnd)
++BasesIt;
else if (FieldsIt != FieldsEnd)
++FieldsIt;
}
// Print the designator to Out.
// Returns false if we could not produce a designator for this element.
bool append(std::string &Out, bool ForSubobject) {
if (IsArray) {
Out.push_back('[');
Out.append(std::to_string(Index));
Out.push_back(']');
return true;
}
if (BasesIt != BasesEnd)
return false; // Bases can't be designated. Should we make one up?
if (FieldsIt != FieldsEnd) {
llvm::StringRef FieldName;
if (const IdentifierInfo *II = FieldsIt->getIdentifier())
FieldName = II->getName();
// For certain objects, their subobjects may be named directly.
if (ForSubobject &&
(FieldsIt->isAnonymousStructOrUnion() ||
// std::array<int,3> x = {1,2,3}. Designators not strictly valid!
(OneField && isReservedName(FieldName))))
return true;
if (!FieldName.empty() && !isReservedName(FieldName)) {
Out.push_back('.');
Out.append(FieldName.begin(), FieldName.end());
return true;
}
return false;
}
return false;
}
private:
bool Valid = false;
bool IsArray = false;
bool OneField = false; // e.g. std::array { T __elements[N]; }
unsigned Index = 0;
CXXRecordDecl::base_class_const_iterator BasesIt;
CXXRecordDecl::base_class_const_iterator BasesEnd;
RecordDecl::field_iterator FieldsIt;
RecordDecl::field_iterator FieldsEnd;
};
// Collect designator labels describing the elements of an init list.
//
// This function contributes the designators of some (sub)object, which is
// represented by the semantic InitListExpr Sem.
// This includes any nested subobjects, but *only* if they are part of the same
// original syntactic init list (due to brace elision).
// In other words, it may descend into subobjects but not written init-lists.
//
// For example: struct Outer { Inner a,b; }; struct Inner { int x, y; }
// Outer o{{1, 2}, 3};
// This function will be called with Sem = { {1, 2}, {3, ImplicitValue} }
// It should generate designators '.a:' and '.b.x:'.
// '.a:' is produced directly without recursing into the written sublist.
// (The written sublist will have a separate collectDesignators() call later).
// Recursion with Prefix='.b' and Sem = {3, ImplicitValue} produces '.b.x:'.
void collectDesignators(const InitListExpr *Sem,
llvm::DenseMap<SourceLocation, std::string> &Out,
const llvm::DenseSet<SourceLocation> &NestedBraces,
std::string &Prefix) {
if (!Sem || Sem->isTransparent())
return;
assert(Sem->isSemanticForm());
// The elements of the semantic form all correspond to direct subobjects of
// the aggregate type. `Fields` iterates over these subobject names.
AggregateDesignatorNames Fields(Sem->getType());
if (!Fields)
return;
for (const Expr *Init : Sem->inits()) {
auto Next = llvm::make_scope_exit([&, Size(Prefix.size())] {
Fields.next(); // Always advance to the next subobject name.
Prefix.resize(Size); // Erase any designator we appended.
});
if (llvm::isa<ImplicitValueInitExpr>(Init))
continue; // a "hole" for a subobject that was not explicitly initialized
const auto *BraceElidedSubobject = llvm::dyn_cast<InitListExpr>(Init);
if (BraceElidedSubobject &&
NestedBraces.contains(BraceElidedSubobject->getLBraceLoc()))
BraceElidedSubobject = nullptr; // there were braces!
if (!Fields.append(Prefix, BraceElidedSubobject != nullptr))
continue; // no designator available for this subobject
if (BraceElidedSubobject) {
// If the braces were elided, this aggregate subobject is initialized
// inline in the same syntactic list.
// Descend into the semantic list describing the subobject.
// (NestedBraces are still correct, they're from the same syntactic list).
collectDesignators(BraceElidedSubobject, Out, NestedBraces, Prefix);
continue;
}
Out.try_emplace(Init->getBeginLoc(), Prefix);
}
}
// Get designators describing the elements of a (syntactic) init list.
// This does not produce designators for any explicitly-written nested lists.
llvm::DenseMap<SourceLocation, std::string>
getDesignators(const InitListExpr *Syn) {
assert(Syn->isSyntacticForm());
// collectDesignators needs to know which InitListExprs in the semantic tree
// were actually written, but InitListExpr::isExplicit() lies.
// Instead, record where braces of sub-init-lists occur in the syntactic form.
llvm::DenseSet<SourceLocation> NestedBraces;
for (const Expr *Init : Syn->inits())
if (auto *Nested = llvm::dyn_cast<InitListExpr>(Init))
NestedBraces.insert(Nested->getLBraceLoc());
// Traverse the semantic form to find the designators.
// We use their SourceLocation to correlate with the syntactic form later.
llvm::DenseMap<SourceLocation, std::string> Designators;
std::string EmptyPrefix;
collectDesignators(Syn->isSemanticForm() ? Syn : Syn->getSemanticForm(),
Designators, NestedBraces, EmptyPrefix);
return Designators;
}
class InlayHintVisitor : public RecursiveASTVisitor<InlayHintVisitor> {
public:
InlayHintVisitor(std::vector<InlayHint> &Results, ParsedAST &AST,
const Config &Cfg, llvm::Optional<Range> RestrictRange)
: Results(Results), AST(AST.getASTContext()), Cfg(Cfg),
RestrictRange(std::move(RestrictRange)),
MainFileID(AST.getSourceManager().getMainFileID()),
Resolver(AST.getHeuristicResolver()),
TypeHintPolicy(this->AST.getPrintingPolicy()),
StructuredBindingPolicy(this->AST.getPrintingPolicy()) {
bool Invalid = false;
llvm::StringRef Buf =
AST.getSourceManager().getBufferData(MainFileID, &Invalid);
MainFileBuf = Invalid ? StringRef{} : Buf;
TypeHintPolicy.SuppressScope = true; // keep type names short
TypeHintPolicy.AnonymousTagLocations =
false; // do not print lambda locations
// For structured bindings, print canonical types. This is important because
// for bindings that use the tuple_element protocol, the non-canonical types
// would be "tuple_element<I, A>::type".
// For "auto", we often prefer sugared types.
// Not setting PrintCanonicalTypes for "auto" allows
// SuppressDefaultTemplateArgs (set by default) to have an effect.
StructuredBindingPolicy = TypeHintPolicy;
StructuredBindingPolicy.PrintCanonicalTypes = true;
}
bool VisitCXXConstructExpr(CXXConstructExpr *E) {
// Weed out constructor calls that don't look like a function call with
// an argument list, by checking the validity of getParenOrBraceRange().
// Also weed out std::initializer_list constructors as there are no names
// for the individual arguments.
if (!E->getParenOrBraceRange().isValid() ||
E->isStdInitListInitialization()) {
return true;
}
processCall(E->getParenOrBraceRange().getBegin(), E->getConstructor(),
{E->getArgs(), E->getNumArgs()});
return true;
}
bool VisitCallExpr(CallExpr *E) {
if (!Cfg.InlayHints.Parameters)
return true;
// Do not show parameter hints for operator calls written using operator
// syntax or user-defined literals. (Among other reasons, the resulting
// hints can look awkard, e.g. the expression can itself be a function
// argument and then we'd get two hints side by side).
if (isa<CXXOperatorCallExpr>(E) || isa<UserDefinedLiteral>(E))
return true;
auto CalleeDecls = Resolver->resolveCalleeOfCallExpr(E);
if (CalleeDecls.size() != 1)
return true;
const FunctionDecl *Callee = nullptr;
if (const auto *FD = dyn_cast<FunctionDecl>(CalleeDecls[0]))
Callee = FD;
else if (const auto *FTD = dyn_cast<FunctionTemplateDecl>(CalleeDecls[0]))
Callee = FTD->getTemplatedDecl();
if (!Callee)
return true;
processCall(E->getRParenLoc(), Callee, {E->getArgs(), E->getNumArgs()});
return true;
}
bool VisitFunctionDecl(FunctionDecl *D) {
if (auto *AT = D->getReturnType()->getContainedAutoType()) {
QualType Deduced = AT->getDeducedType();
if (!Deduced.isNull()) {
addTypeHint(D->getFunctionTypeLoc().getRParenLoc(), D->getReturnType(),
/*Prefix=*/"-> ");
}
}
return true;
}
bool VisitVarDecl(VarDecl *D) {
// Do not show hints for the aggregate in a structured binding,
// but show hints for the individual bindings.
if (auto *DD = dyn_cast<DecompositionDecl>(D)) {
for (auto *Binding : DD->bindings()) {
addTypeHint(Binding->getLocation(), Binding->getType(), /*Prefix=*/": ",
StructuredBindingPolicy);
}
return true;
}
if (D->getType()->getContainedAutoType()) {
if (!D->getType()->isDependentType()) {
// Our current approach is to place the hint on the variable
// and accordingly print the full type
// (e.g. for `const auto& x = 42`, print `const int&`).
// Alternatively, we could place the hint on the `auto`
// (and then just print the type deduced for the `auto`).
addTypeHint(D->getLocation(), D->getType(), /*Prefix=*/": ");
}
}
return true;
}
bool VisitInitListExpr(InitListExpr *Syn) {
// We receive the syntactic form here (shouldVisitImplicitCode() is false).
// This is the one we will ultimately attach designators to.
// It may have subobject initializers inlined without braces. The *semantic*
// form of the init-list has nested init-lists for these.
// getDesignators will look at the semantic form to determine the labels.
assert(Syn->isSyntacticForm() && "RAV should not visit implicit code!");
if (!Cfg.InlayHints.Designators)
return true;
if (Syn->isIdiomaticZeroInitializer(AST.getLangOpts()))
return true;
llvm::DenseMap<SourceLocation, std::string> Designators =
getDesignators(Syn);
for (const Expr *Init : Syn->inits()) {
if (llvm::isa<DesignatedInitExpr>(Init))
continue;
auto It = Designators.find(Init->getBeginLoc());
if (It != Designators.end() &&
!isPrecededByParamNameComment(Init, It->second))
addDesignatorHint(Init->getSourceRange(), It->second);
}
return true;
}
// FIXME: Handle RecoveryExpr to try to hint some invalid calls.
private:
using NameVec = SmallVector<StringRef, 8>;
// The purpose of Anchor is to deal with macros. It should be the call's
// opening or closing parenthesis or brace. (Always using the opening would
// make more sense but CallExpr only exposes the closing.) We heuristically
// assume that if this location does not come from a macro definition, then
// the entire argument list likely appears in the main file and can be hinted.
void processCall(SourceLocation Anchor, const FunctionDecl *Callee,
llvm::ArrayRef<const Expr *const> Args) {
if (!Cfg.InlayHints.Parameters || Args.size() == 0 || !Callee)
return;
// If the anchor location comes from a macro defintion, there's nowhere to
// put hints.
if (!AST.getSourceManager().getTopMacroCallerLoc(Anchor).isFileID())
return;
// The parameter name of a move or copy constructor is not very interesting.
if (auto *Ctor = dyn_cast<CXXConstructorDecl>(Callee))
if (Ctor->isCopyOrMoveConstructor())
return;
// Don't show hints for variadic parameters.
size_t FixedParamCount = getFixedParamCount(Callee);
size_t ArgCount = std::min(FixedParamCount, Args.size());
NameVec ParameterNames = chooseParameterNames(Callee, ArgCount);
// Exclude setters (i.e. functions with one argument whose name begins with
// "set"), as their parameter name is also not likely to be interesting.
if (isSetter(Callee, ParameterNames))
return;
for (size_t I = 0; I < ArgCount; ++I) {
StringRef Name = ParameterNames[I];
if (!shouldHint(Args[I], Name))
continue;
addInlayHint(Args[I]->getSourceRange(), HintSide::Left,
InlayHintKind::ParameterHint, /*Prefix=*/"", Name,
/*Suffix=*/": ");
}
}
static bool isSetter(const FunctionDecl *Callee, const NameVec &ParamNames) {
if (ParamNames.size() != 1)
return false;
StringRef Name = getSimpleName(*Callee);
if (!Name.startswith_insensitive("set"))
return false;
// In addition to checking that the function has one parameter and its
// name starts with "set", also check that the part after "set" matches
// the name of the parameter (ignoring case). The idea here is that if
// the parameter name differs, it may contain extra information that
// may be useful to show in a hint, as in:
// void setTimeout(int timeoutMillis);
// This currently doesn't handle cases where params use snake_case
// and functions don't, e.g.
// void setExceptionHandler(EHFunc exception_handler);
// We could improve this by replacing `equals_insensitive` with some
// `sloppy_equals` which ignores case and also skips underscores.
StringRef WhatItIsSetting = Name.substr(3).ltrim("_");
return WhatItIsSetting.equals_insensitive(ParamNames[0]);
}
bool shouldHint(const Expr *Arg, StringRef ParamName) {
if (ParamName.empty())
return false;
// If the argument expression is a single name and it matches the
// parameter name exactly, omit the hint.
if (ParamName == getSpelledIdentifier(Arg))
return false;
// Exclude argument expressions preceded by a /*paramName*/.
if (isPrecededByParamNameComment(Arg, ParamName))
return false;
return true;
}
// Checks if "E" is spelled in the main file and preceded by a C-style comment
// whose contents match ParamName (allowing for whitespace and an optional "="
// at the end.
bool isPrecededByParamNameComment(const Expr *E, StringRef ParamName) {
auto &SM = AST.getSourceManager();
auto ExprStartLoc = SM.getTopMacroCallerLoc(E->getBeginLoc());
auto Decomposed = SM.getDecomposedLoc(ExprStartLoc);
if (Decomposed.first != MainFileID)
return false;
StringRef SourcePrefix = MainFileBuf.substr(0, Decomposed.second);
// Allow whitespace between comment and expression.
SourcePrefix = SourcePrefix.rtrim();
// Check for comment ending.
if (!SourcePrefix.consume_back("*/"))
return false;
// Ignore some punctuation and whitespace around comment.
// In particular this allows designators to match nicely.
llvm::StringLiteral IgnoreChars = " =.";
SourcePrefix = SourcePrefix.rtrim(IgnoreChars);
ParamName = ParamName.trim(IgnoreChars);
// Other than that, the comment must contain exactly ParamName.
if (!SourcePrefix.consume_back(ParamName))
return false;
SourcePrefix = SourcePrefix.rtrim(IgnoreChars);
return SourcePrefix.endswith("/*");
}
// If "E" spells a single unqualified identifier, return that name.
// Otherwise, return an empty string.
static StringRef getSpelledIdentifier(const Expr *E) {
E = E->IgnoreUnlessSpelledInSource();
if (auto *DRE = dyn_cast<DeclRefExpr>(E))
if (!DRE->getQualifier())
return getSimpleName(*DRE->getDecl());
if (auto *ME = dyn_cast<MemberExpr>(E))
if (!ME->getQualifier() && ME->isImplicitAccess())
return getSimpleName(*ME->getMemberDecl());
return {};
}
NameVec chooseParameterNames(const FunctionDecl *Callee, size_t ArgCount) {
// The current strategy here is to use all the parameter names from the
// canonical declaration, unless they're all empty, in which case we
// use all the parameter names from the definition (in present in the
// translation unit).
// We could try a bit harder, e.g.:
// - try all re-declarations, not just canonical + definition
// - fall back arg-by-arg rather than wholesale
NameVec ParameterNames = getParameterNamesForDecl(Callee, ArgCount);
if (llvm::all_of(ParameterNames, std::mem_fn(&StringRef::empty))) {
if (const FunctionDecl *Def = Callee->getDefinition()) {
ParameterNames = getParameterNamesForDecl(Def, ArgCount);
}
}
assert(ParameterNames.size() == ArgCount);
// Standard library functions often have parameter names that start
// with underscores, which makes the hints noisy, so strip them out.
for (auto &Name : ParameterNames)
stripLeadingUnderscores(Name);
return ParameterNames;
}
static void stripLeadingUnderscores(StringRef &Name) {
Name = Name.ltrim('_');
}
// Return the number of fixed parameters Function has, that is, not counting
// parameters that are variadic (instantiated from a parameter pack) or
// C-style varargs.
static size_t getFixedParamCount(const FunctionDecl *Function) {
if (FunctionTemplateDecl *Template = Function->getPrimaryTemplate()) {
FunctionDecl *F = Template->getTemplatedDecl();
size_t Result = 0;
for (ParmVarDecl *Parm : F->parameters()) {
if (Parm->isParameterPack()) {
break;
}
++Result;
}
return Result;
}
// C-style varargs don't need special handling, they're already
// not included in getNumParams().
return Function->getNumParams();
}
static StringRef getSimpleName(const NamedDecl &D) {
if (IdentifierInfo *Ident = D.getDeclName().getAsIdentifierInfo()) {
return Ident->getName();
}
return StringRef();
}
NameVec getParameterNamesForDecl(const FunctionDecl *Function,
size_t ArgCount) {
NameVec Result;
for (size_t I = 0; I < ArgCount; ++I) {
const ParmVarDecl *Parm = Function->getParamDecl(I);
assert(Parm);
Result.emplace_back(getSimpleName(*Parm));
}
return Result;
}
// We pass HintSide rather than SourceLocation because we want to ensure
// it is in the same file as the common file range.
void addInlayHint(SourceRange R, HintSide Side, InlayHintKind Kind,
llvm::StringRef Prefix, llvm::StringRef Label,
llvm::StringRef Suffix) {
// We shouldn't get as far as adding a hint if the category is disabled.
// We'd like to disable as much of the analysis as possible above instead.
// Assert in debug mode but add a dynamic check in production.
assert(Cfg.InlayHints.Enabled && "Shouldn't get here if disabled!");
switch (Kind) {
#define CHECK_KIND(Enumerator, ConfigProperty) \
case InlayHintKind::Enumerator: \
assert(Cfg.InlayHints.ConfigProperty && \
"Shouldn't get here if kind is disabled!"); \
if (!Cfg.InlayHints.ConfigProperty) \
return; \
break
CHECK_KIND(ParameterHint, Parameters);
CHECK_KIND(TypeHint, DeducedTypes);
CHECK_KIND(DesignatorHint, Designators);
#undef CHECK_KIND
}
auto FileRange =
toHalfOpenFileRange(AST.getSourceManager(), AST.getLangOpts(), R);
if (!FileRange)
return;
Range LSPRange{
sourceLocToPosition(AST.getSourceManager(), FileRange->getBegin()),
sourceLocToPosition(AST.getSourceManager(), FileRange->getEnd())};
Position LSPPos = Side == HintSide::Left ? LSPRange.start : LSPRange.end;
if (RestrictRange &&
(LSPPos < RestrictRange->start || !(LSPPos < RestrictRange->end)))
return;
// The hint may be in a file other than the main file (for example, a header
// file that was included after the preamble), do not show in that case.
if (!AST.getSourceManager().isWrittenInMainFile(FileRange->getBegin()))
return;
Results.push_back(
InlayHint{LSPPos, LSPRange, Kind, (Prefix + Label + Suffix).str()});
}
void addTypeHint(SourceRange R, QualType T, llvm::StringRef Prefix) {
addTypeHint(R, T, Prefix, TypeHintPolicy);
}
void addTypeHint(SourceRange R, QualType T, llvm::StringRef Prefix,
const PrintingPolicy &Policy) {
if (!Cfg.InlayHints.DeducedTypes || T.isNull())
return;
std::string TypeName = T.getAsString(Policy);
if (TypeName.length() < TypeNameLimit)
addInlayHint(R, HintSide::Right, InlayHintKind::TypeHint, Prefix,
TypeName, /*Suffix=*/"");
}
void addDesignatorHint(SourceRange R, llvm::StringRef Text) {
addInlayHint(R, HintSide::Left, InlayHintKind::DesignatorHint,
/*Prefix=*/"", Text, /*Suffix=*/"=");
}
std::vector<InlayHint> &Results;
ASTContext &AST;
const Config &Cfg;
llvm::Optional<Range> RestrictRange;
FileID MainFileID;
StringRef MainFileBuf;
const HeuristicResolver *Resolver;
// We want to suppress default template arguments, but otherwise print
// canonical types. Unfortunately, they're conflicting policies so we can't
// have both. For regular types, suppressing template arguments is more
// important, whereas printing canonical types is crucial for structured
// bindings, so we use two separate policies. (See the constructor where
// the policies are initialized for more details.)
PrintingPolicy TypeHintPolicy;
PrintingPolicy StructuredBindingPolicy;
static const size_t TypeNameLimit = 32;
};
} // namespace
std::vector<InlayHint> inlayHints(ParsedAST &AST,
llvm::Optional<Range> RestrictRange) {
std::vector<InlayHint> Results;
const auto &Cfg = Config::current();
if (!Cfg.InlayHints.Enabled)
return Results;
InlayHintVisitor Visitor(Results, AST, Cfg, std::move(RestrictRange));
Visitor.TraverseAST(AST.getASTContext());
// De-duplicate hints. Duplicates can sometimes occur due to e.g. explicit
// template instantiations.
llvm::sort(Results);
Results.erase(std::unique(Results.begin(), Results.end()), Results.end());
return Results;
}
} // namespace clangd
} // namespace clang