| //===--- UseConstraintsCheck.cpp - clang-tidy -----------------------------===// |
| // |
| // 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 "UseConstraintsCheck.h" |
| #include "clang/AST/ASTContext.h" |
| #include "clang/ASTMatchers/ASTMatchFinder.h" |
| #include "clang/Lex/Lexer.h" |
| |
| #include "../utils/LexerUtils.h" |
| |
| #include <optional> |
| #include <utility> |
| |
| using namespace clang::ast_matchers; |
| |
| namespace clang::tidy::modernize { |
| |
| struct EnableIfData { |
| TemplateSpecializationTypeLoc Loc; |
| TypeLoc Outer; |
| }; |
| |
| namespace { |
| AST_MATCHER(FunctionDecl, hasOtherDeclarations) { |
| auto It = Node.redecls_begin(); |
| auto EndIt = Node.redecls_end(); |
| |
| if (It == EndIt) |
| return false; |
| |
| ++It; |
| return It != EndIt; |
| } |
| } // namespace |
| |
| void UseConstraintsCheck::registerMatchers(MatchFinder *Finder) { |
| Finder->addMatcher( |
| functionTemplateDecl( |
| has(functionDecl(unless(hasOtherDeclarations()), isDefinition(), |
| hasReturnTypeLoc(typeLoc().bind("return"))) |
| .bind("function"))) |
| .bind("functionTemplate"), |
| this); |
| } |
| |
| static std::optional<TemplateSpecializationTypeLoc> |
| matchEnableIfSpecializationImplTypename(TypeLoc TheType) { |
| if (const auto Dep = TheType.getAs<DependentNameTypeLoc>()) { |
| const IdentifierInfo *Identifier = Dep.getTypePtr()->getIdentifier(); |
| if (!Identifier || Identifier->getName() != "type" || |
| Dep.getTypePtr()->getKeyword() != ElaboratedTypeKeyword::Typename) { |
| return std::nullopt; |
| } |
| TheType = Dep.getQualifierLoc().getTypeLoc(); |
| } |
| |
| if (const auto SpecializationLoc = |
| TheType.getAs<TemplateSpecializationTypeLoc>()) { |
| |
| const auto *Specialization = |
| dyn_cast<TemplateSpecializationType>(SpecializationLoc.getTypePtr()); |
| if (!Specialization) |
| return std::nullopt; |
| |
| const TemplateDecl *TD = |
| Specialization->getTemplateName().getAsTemplateDecl(); |
| if (!TD || TD->getName() != "enable_if") |
| return std::nullopt; |
| |
| int NumArgs = SpecializationLoc.getNumArgs(); |
| if (NumArgs != 1 && NumArgs != 2) |
| return std::nullopt; |
| |
| return SpecializationLoc; |
| } |
| return std::nullopt; |
| } |
| |
| static std::optional<TemplateSpecializationTypeLoc> |
| matchEnableIfSpecializationImplTrait(TypeLoc TheType) { |
| if (const auto Elaborated = TheType.getAs<ElaboratedTypeLoc>()) |
| TheType = Elaborated.getNamedTypeLoc(); |
| |
| if (const auto SpecializationLoc = |
| TheType.getAs<TemplateSpecializationTypeLoc>()) { |
| |
| const auto *Specialization = |
| dyn_cast<TemplateSpecializationType>(SpecializationLoc.getTypePtr()); |
| if (!Specialization) |
| return std::nullopt; |
| |
| const TemplateDecl *TD = |
| Specialization->getTemplateName().getAsTemplateDecl(); |
| if (!TD || TD->getName() != "enable_if_t") |
| return std::nullopt; |
| |
| if (!Specialization->isTypeAlias()) |
| return std::nullopt; |
| |
| if (const auto *AliasedType = |
| dyn_cast<DependentNameType>(Specialization->getAliasedType())) { |
| if (AliasedType->getIdentifier()->getName() != "type" || |
| AliasedType->getKeyword() != ElaboratedTypeKeyword::Typename) { |
| return std::nullopt; |
| } |
| } else { |
| return std::nullopt; |
| } |
| int NumArgs = SpecializationLoc.getNumArgs(); |
| if (NumArgs != 1 && NumArgs != 2) |
| return std::nullopt; |
| |
| return SpecializationLoc; |
| } |
| return std::nullopt; |
| } |
| |
| static std::optional<TemplateSpecializationTypeLoc> |
| matchEnableIfSpecializationImpl(TypeLoc TheType) { |
| if (auto EnableIf = matchEnableIfSpecializationImplTypename(TheType)) |
| return EnableIf; |
| return matchEnableIfSpecializationImplTrait(TheType); |
| } |
| |
| static std::optional<EnableIfData> |
| matchEnableIfSpecialization(TypeLoc TheType) { |
| if (const auto Pointer = TheType.getAs<PointerTypeLoc>()) |
| TheType = Pointer.getPointeeLoc(); |
| else if (const auto Reference = TheType.getAs<ReferenceTypeLoc>()) |
| TheType = Reference.getPointeeLoc(); |
| if (const auto Qualified = TheType.getAs<QualifiedTypeLoc>()) |
| TheType = Qualified.getUnqualifiedLoc(); |
| |
| if (auto EnableIf = matchEnableIfSpecializationImpl(TheType)) |
| return EnableIfData{std::move(*EnableIf), TheType}; |
| return std::nullopt; |
| } |
| |
| static std::pair<std::optional<EnableIfData>, const Decl *> |
| matchTrailingTemplateParam(const FunctionTemplateDecl *FunctionTemplate) { |
| // For non-type trailing param, match very specifically |
| // 'template <..., enable_if_type<Condition, Type> = Default>' where |
| // enable_if_type is 'enable_if' or 'enable_if_t'. E.g., 'template <typename |
| // T, enable_if_t<is_same_v<T, bool>, int*> = nullptr> |
| // |
| // Otherwise, match a trailing default type arg. |
| // E.g., 'template <typename T, typename = enable_if_t<is_same_v<T, bool>>>' |
| |
| const TemplateParameterList *TemplateParams = |
| FunctionTemplate->getTemplateParameters(); |
| if (TemplateParams->size() == 0) |
| return {}; |
| |
| const NamedDecl *LastParam = |
| TemplateParams->getParam(TemplateParams->size() - 1); |
| if (const auto *LastTemplateParam = |
| dyn_cast<NonTypeTemplateParmDecl>(LastParam)) { |
| |
| if (!LastTemplateParam->hasDefaultArgument() || |
| !LastTemplateParam->getName().empty()) |
| return {}; |
| |
| return {matchEnableIfSpecialization( |
| LastTemplateParam->getTypeSourceInfo()->getTypeLoc()), |
| LastTemplateParam}; |
| } |
| if (const auto *LastTemplateParam = |
| dyn_cast<TemplateTypeParmDecl>(LastParam)) { |
| if (LastTemplateParam->hasDefaultArgument() && |
| LastTemplateParam->getIdentifier() == nullptr) { |
| return {matchEnableIfSpecialization( |
| LastTemplateParam->getDefaultArgumentInfo()->getTypeLoc()), |
| LastTemplateParam}; |
| } |
| } |
| return {}; |
| } |
| |
| template <typename T> |
| static SourceLocation getRAngleFileLoc(const SourceManager &SM, |
| const T &Element) { |
| // getFileLoc handles the case where the RAngle loc is part of a synthesized |
| // '>>', which ends up allocating a 'scratch space' buffer in the source |
| // manager. |
| return SM.getFileLoc(Element.getRAngleLoc()); |
| } |
| |
| static SourceRange |
| getConditionRange(ASTContext &Context, |
| const TemplateSpecializationTypeLoc &EnableIf) { |
| // TemplateArgumentLoc's SourceRange End is the location of the last token |
| // (per UnqualifiedId docs). E.g., in `enable_if<AAA && BBB>`, the End |
| // location will be the first 'B' in 'BBB'. |
| const LangOptions &LangOpts = Context.getLangOpts(); |
| const SourceManager &SM = Context.getSourceManager(); |
| if (EnableIf.getNumArgs() > 1) { |
| TemplateArgumentLoc NextArg = EnableIf.getArgLoc(1); |
| return {EnableIf.getLAngleLoc().getLocWithOffset(1), |
| utils::lexer::findPreviousTokenKind( |
| NextArg.getSourceRange().getBegin(), SM, LangOpts, tok::comma)}; |
| } |
| |
| return {EnableIf.getLAngleLoc().getLocWithOffset(1), |
| getRAngleFileLoc(SM, EnableIf)}; |
| } |
| |
| static SourceRange getTypeRange(ASTContext &Context, |
| const TemplateSpecializationTypeLoc &EnableIf) { |
| TemplateArgumentLoc Arg = EnableIf.getArgLoc(1); |
| const LangOptions &LangOpts = Context.getLangOpts(); |
| const SourceManager &SM = Context.getSourceManager(); |
| return {utils::lexer::findPreviousTokenKind(Arg.getSourceRange().getBegin(), |
| SM, LangOpts, tok::comma) |
| .getLocWithOffset(1), |
| getRAngleFileLoc(SM, EnableIf)}; |
| } |
| |
| // Returns the original source text of the second argument of a call to |
| // enable_if_t. E.g., in enable_if_t<Condition, TheType>, this function |
| // returns 'TheType'. |
| static std::optional<StringRef> |
| getTypeText(ASTContext &Context, |
| const TemplateSpecializationTypeLoc &EnableIf) { |
| if (EnableIf.getNumArgs() > 1) { |
| const LangOptions &LangOpts = Context.getLangOpts(); |
| const SourceManager &SM = Context.getSourceManager(); |
| bool Invalid = false; |
| StringRef Text = Lexer::getSourceText(CharSourceRange::getCharRange( |
| getTypeRange(Context, EnableIf)), |
| SM, LangOpts, &Invalid) |
| .trim(); |
| if (Invalid) |
| return std::nullopt; |
| |
| return Text; |
| } |
| |
| return "void"; |
| } |
| |
| static std::optional<SourceLocation> |
| findInsertionForConstraint(const FunctionDecl *Function, ASTContext &Context) { |
| SourceManager &SM = Context.getSourceManager(); |
| const LangOptions &LangOpts = Context.getLangOpts(); |
| |
| if (const auto *Constructor = dyn_cast<CXXConstructorDecl>(Function)) { |
| for (const CXXCtorInitializer *Init : Constructor->inits()) { |
| if (Init->getSourceOrder() == 0) |
| return utils::lexer::findPreviousTokenKind(Init->getSourceLocation(), |
| SM, LangOpts, tok::colon); |
| } |
| if (Constructor->init_begin() != Constructor->init_end()) |
| return std::nullopt; |
| } |
| if (Function->isDeleted()) { |
| SourceLocation FunctionEnd = Function->getSourceRange().getEnd(); |
| return utils::lexer::findNextAnyTokenKind(FunctionEnd, SM, LangOpts, |
| tok::equal, tok::equal); |
| } |
| const Stmt *Body = Function->getBody(); |
| if (!Body) |
| return std::nullopt; |
| |
| return Body->getBeginLoc(); |
| } |
| |
| bool isPrimaryExpression(const Expr *Expression) { |
| // This function is an incomplete approximation of checking whether |
| // an Expr is a primary expression. In particular, if this function |
| // returns true, the expression is a primary expression. The converse |
| // is not necessarily true. |
| |
| if (const auto *Cast = dyn_cast<ImplicitCastExpr>(Expression)) |
| Expression = Cast->getSubExprAsWritten(); |
| if (isa<ParenExpr, DependentScopeDeclRefExpr>(Expression)) |
| return true; |
| |
| return false; |
| } |
| |
| // Return the original source text of an enable_if_t condition, i.e., the |
| // first template argument). For example, in |
| // 'enable_if_t<FirstCondition || SecondCondition, AType>', the text |
| // the text 'FirstCondition || SecondCondition' is returned. |
| static std::optional<std::string> getConditionText(const Expr *ConditionExpr, |
| SourceRange ConditionRange, |
| ASTContext &Context) { |
| SourceManager &SM = Context.getSourceManager(); |
| const LangOptions &LangOpts = Context.getLangOpts(); |
| |
| SourceLocation PrevTokenLoc = ConditionRange.getEnd(); |
| if (PrevTokenLoc.isInvalid()) |
| return std::nullopt; |
| |
| const bool SkipComments = false; |
| Token PrevToken; |
| std::tie(PrevToken, PrevTokenLoc) = utils::lexer::getPreviousTokenAndStart( |
| PrevTokenLoc, SM, LangOpts, SkipComments); |
| bool EndsWithDoubleSlash = |
| PrevToken.is(tok::comment) && |
| Lexer::getSourceText(CharSourceRange::getCharRange( |
| PrevTokenLoc, PrevTokenLoc.getLocWithOffset(2)), |
| SM, LangOpts) == "//"; |
| |
| bool Invalid = false; |
| llvm::StringRef ConditionText = Lexer::getSourceText( |
| CharSourceRange::getCharRange(ConditionRange), SM, LangOpts, &Invalid); |
| if (Invalid) |
| return std::nullopt; |
| |
| auto AddParens = [&](llvm::StringRef Text) -> std::string { |
| if (isPrimaryExpression(ConditionExpr)) |
| return Text.str(); |
| return "(" + Text.str() + ")"; |
| }; |
| |
| if (EndsWithDoubleSlash) |
| return AddParens(ConditionText); |
| return AddParens(ConditionText.trim()); |
| } |
| |
| // Handle functions that return enable_if_t, e.g., |
| // template <...> |
| // enable_if_t<Condition, ReturnType> function(); |
| // |
| // Return a vector of FixItHints if the code can be replaced with |
| // a C++20 requires clause. In the example above, returns FixItHints |
| // to result in |
| // template <...> |
| // ReturnType function() requires Condition {} |
| static std::vector<FixItHint> handleReturnType(const FunctionDecl *Function, |
| const TypeLoc &ReturnType, |
| const EnableIfData &EnableIf, |
| ASTContext &Context) { |
| TemplateArgumentLoc EnableCondition = EnableIf.Loc.getArgLoc(0); |
| |
| SourceRange ConditionRange = getConditionRange(Context, EnableIf.Loc); |
| |
| std::optional<std::string> ConditionText = getConditionText( |
| EnableCondition.getSourceExpression(), ConditionRange, Context); |
| if (!ConditionText) |
| return {}; |
| |
| std::optional<StringRef> TypeText = getTypeText(Context, EnableIf.Loc); |
| if (!TypeText) |
| return {}; |
| |
| SmallVector<const Expr *, 3> ExistingConstraints; |
| Function->getAssociatedConstraints(ExistingConstraints); |
| if (!ExistingConstraints.empty()) { |
| // FIXME - Support adding new constraints to existing ones. Do we need to |
| // consider subsumption? |
| return {}; |
| } |
| |
| std::optional<SourceLocation> ConstraintInsertionLoc = |
| findInsertionForConstraint(Function, Context); |
| if (!ConstraintInsertionLoc) |
| return {}; |
| |
| std::vector<FixItHint> FixIts; |
| FixIts.push_back(FixItHint::CreateReplacement( |
| CharSourceRange::getTokenRange(EnableIf.Outer.getSourceRange()), |
| *TypeText)); |
| FixIts.push_back(FixItHint::CreateInsertion( |
| *ConstraintInsertionLoc, "requires " + *ConditionText + " ")); |
| return FixIts; |
| } |
| |
| // Handle enable_if_t in a trailing template parameter, e.g., |
| // template <..., enable_if_t<Condition, Type> = Type{}> |
| // ReturnType function(); |
| // |
| // Return a vector of FixItHints if the code can be replaced with |
| // a C++20 requires clause. In the example above, returns FixItHints |
| // to result in |
| // template <...> |
| // ReturnType function() requires Condition {} |
| static std::vector<FixItHint> |
| handleTrailingTemplateType(const FunctionTemplateDecl *FunctionTemplate, |
| const FunctionDecl *Function, |
| const Decl *LastTemplateParam, |
| const EnableIfData &EnableIf, ASTContext &Context) { |
| SourceManager &SM = Context.getSourceManager(); |
| const LangOptions &LangOpts = Context.getLangOpts(); |
| |
| TemplateArgumentLoc EnableCondition = EnableIf.Loc.getArgLoc(0); |
| |
| SourceRange ConditionRange = getConditionRange(Context, EnableIf.Loc); |
| |
| std::optional<std::string> ConditionText = getConditionText( |
| EnableCondition.getSourceExpression(), ConditionRange, Context); |
| if (!ConditionText) |
| return {}; |
| |
| SmallVector<const Expr *, 3> ExistingConstraints; |
| Function->getAssociatedConstraints(ExistingConstraints); |
| if (!ExistingConstraints.empty()) { |
| // FIXME - Support adding new constraints to existing ones. Do we need to |
| // consider subsumption? |
| return {}; |
| } |
| |
| SourceRange RemovalRange; |
| const TemplateParameterList *TemplateParams = |
| FunctionTemplate->getTemplateParameters(); |
| if (!TemplateParams || TemplateParams->size() == 0) |
| return {}; |
| |
| if (TemplateParams->size() == 1) { |
| RemovalRange = |
| SourceRange(TemplateParams->getTemplateLoc(), |
| getRAngleFileLoc(SM, *TemplateParams).getLocWithOffset(1)); |
| } else { |
| RemovalRange = |
| SourceRange(utils::lexer::findPreviousTokenKind( |
| LastTemplateParam->getSourceRange().getBegin(), SM, |
| LangOpts, tok::comma), |
| getRAngleFileLoc(SM, *TemplateParams)); |
| } |
| |
| std::optional<SourceLocation> ConstraintInsertionLoc = |
| findInsertionForConstraint(Function, Context); |
| if (!ConstraintInsertionLoc) |
| return {}; |
| |
| std::vector<FixItHint> FixIts; |
| FixIts.push_back( |
| FixItHint::CreateRemoval(CharSourceRange::getCharRange(RemovalRange))); |
| FixIts.push_back(FixItHint::CreateInsertion( |
| *ConstraintInsertionLoc, "requires " + *ConditionText + " ")); |
| return FixIts; |
| } |
| |
| void UseConstraintsCheck::check(const MatchFinder::MatchResult &Result) { |
| const auto *FunctionTemplate = |
| Result.Nodes.getNodeAs<FunctionTemplateDecl>("functionTemplate"); |
| const auto *Function = Result.Nodes.getNodeAs<FunctionDecl>("function"); |
| const auto *ReturnType = Result.Nodes.getNodeAs<TypeLoc>("return"); |
| if (!FunctionTemplate || !Function || !ReturnType) |
| return; |
| |
| // Check for |
| // |
| // Case 1. Return type of function |
| // |
| // template <...> |
| // enable_if_t<Condition, ReturnType>::type function() {} |
| // |
| // Case 2. Trailing template parameter |
| // |
| // template <..., enable_if_t<Condition, Type> = Type{}> |
| // ReturnType function() {} |
| // |
| // or |
| // |
| // template <..., typename = enable_if_t<Condition, void>> |
| // ReturnType function() {} |
| // |
| |
| // Case 1. Return type of function |
| if (auto EnableIf = matchEnableIfSpecialization(*ReturnType)) { |
| diag(ReturnType->getBeginLoc(), |
| "use C++20 requires constraints instead of enable_if") |
| << handleReturnType(Function, *ReturnType, *EnableIf, *Result.Context); |
| return; |
| } |
| |
| // Case 2. Trailing template parameter |
| if (auto [EnableIf, LastTemplateParam] = |
| matchTrailingTemplateParam(FunctionTemplate); |
| EnableIf && LastTemplateParam) { |
| diag(LastTemplateParam->getSourceRange().getBegin(), |
| "use C++20 requires constraints instead of enable_if") |
| << handleTrailingTemplateType(FunctionTemplate, Function, |
| LastTemplateParam, *EnableIf, |
| *Result.Context); |
| return; |
| } |
| } |
| |
| } // namespace clang::tidy::modernize |
