================
@@ -0,0 +1,972 @@
+//===--- UseConstexprCheck.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 "UseConstexprCheck.h"
+#include "../utils/ASTUtils.h"
+#include "../utils/LexerUtils.h"
+#include "clang/AST/ASTContext.h"
+#include "clang/AST/ASTTypeTraits.h"
+#include "clang/AST/Decl.h"
+#include "clang/AST/DeclBase.h"
+#include "clang/AST/DeclCXX.h"
+#include "clang/AST/ExprCXX.h"
+#include "clang/AST/OperationKinds.h"
+#include "clang/AST/RecursiveASTVisitor.h"
+#include "clang/AST/Stmt.h"
+#include "clang/AST/StmtCXX.h"
+#include "clang/ASTMatchers/ASTMatchFinder.h"
+#include "clang/ASTMatchers/ASTMatchers.h"
+#include "clang/ASTMatchers/ASTMatchersInternal.h"
+#include "clang/ASTMatchers/ASTMatchersMacros.h"
+#include "clang/Basic/LangOptions.h"
+#include "clang/Basic/SourceLocation.h"
+#include "clang/Basic/SourceManager.h"
+#include "clang/Basic/Specifiers.h"
+#include "clang/Basic/TokenKinds.h"
+#include "llvm/ADT/STLExtras.h"
+#include "llvm/ADT/SmallPtrSet.h"
+#include "llvm/Support/Casting.h"
+#include <cstddef>
+#include <functional>
+
+using namespace clang::ast_matchers;
+
+namespace clang::tidy::modernize {
+
+namespace {
+AST_MATCHER(FunctionDecl, locationPermitsConstexpr) {
+ const bool IsInMainFile =
+ Finder->getASTContext().getSourceManager().isInMainFile(
+ Node.getLocation());
+
+ if (IsInMainFile && Node.hasExternalFormalLinkage())
+ return false;
+ if (!IsInMainFile && !Node.isInlined())
+ return false;
+
+ return true;
+}
+
+AST_MATCHER(Expr, isCXX11ConstantExpr) {
+ return !Node.isValueDependent() &&
+ Node.isCXX11ConstantExpr(Finder->getASTContext());
+}
+
+AST_MATCHER(DeclaratorDecl, isInMacro) {
+ const SourceRange R =
+ SourceRange(Node.getTypeSpecStartLoc(), Node.getLocation());
+
+ return Node.getLocation().isMacroID() || Node.getEndLoc().isMacroID() ||
+ utils::rangeContainsMacroExpansion(
+ R, &Finder->getASTContext().getSourceManager()) ||
+ utils::rangeIsEntirelyWithinMacroArgument(
+ R, &Finder->getASTContext().getSourceManager());
+}
+
+AST_MATCHER(Decl, hasNoRedecl) {
+ // There is always the actual declaration
+ return !Node.redecls().empty() &&
+ std::next(Node.redecls_begin()) == Node.redecls_end();
+}
+
+AST_MATCHER(Decl, allRedeclsInSameFile) {
+ const SourceManager &SM = Finder->getASTContext().getSourceManager();
+ const SourceLocation L = Node.getLocation();
+ for (const Decl *ReDecl : Node.redecls()) {
+ if (!SM.isWrittenInSameFile(L, ReDecl->getLocation()))
+ return false;
+ }
+ return true;
+}
+} // namespace
+
+static bool
+satisfiesConstructorPropertiesUntil20(const CXXConstructorDecl *Ctor,
+ ASTContext &Ctx) {
+ const CXXRecordDecl *Rec = Ctor->getParent();
+ llvm::SmallPtrSet<const RecordDecl *, 8> Bases{};
+ for (const CXXBaseSpecifier Base : Rec->bases())
+ Bases.insert(Base.getType()->getAsRecordDecl());
+
+ llvm::SmallPtrSet<const FieldDecl *, 8> Fields{Rec->field_begin(),
+ Rec->field_end()};
+ llvm::SmallPtrSet<const FieldDecl *, 4> Indirects{};
+
+ for (const CXXCtorInitializer *const Init : Ctor->inits()) {
+ const Type *InitType = Init->getBaseClass();
+ if (InitType && InitType->isRecordType()) {
+ const auto *ConstructingInit =
+ llvm::dyn_cast<CXXConstructExpr>(Init->getInit());
+ if (ConstructingInit &&
+ !ConstructingInit->getConstructor()->isConstexprSpecified())
+ return false;
+ }
+
+ if (Init->isBaseInitializer()) {
+ Bases.erase(Init->getBaseClass()->getAsRecordDecl());
+ continue;
+ }
+
+ if (Init->isMemberInitializer()) {
+ const FieldDecl *Field = Init->getMember();
+
+ if (Field->isAnonymousStructOrUnion())
+ Indirects.insert(Field);
+
+ Fields.erase(Field);
+ continue;
+ }
+ }
+
+ for (const auto &Match :
+ match(cxxRecordDecl(forEach(indirectFieldDecl().bind("indirect"))),
*Rec,
+ Ctx)) {
+ const auto *IField = Match.getNodeAs<IndirectFieldDecl>("indirect");
+
+ size_t NumInitializations = false;
+ for (const NamedDecl *ND : IField->chain())
+ NumInitializations += Indirects.erase(llvm::dyn_cast<FieldDecl>(ND));
+
+ if (NumInitializations != 1)
+ return false;
+
+ for (const NamedDecl *ND : IField->chain())
+ Fields.erase(llvm::dyn_cast<FieldDecl>(ND));
+ }
+
+ if (!Fields.empty())
+ return false;
+
+ return true;
+}
+
+static const Type *unwrapPointee(const Type *T) {
+ if (!T->isPointerOrReferenceType())
+ return T;
+
+ while (T && T->isPointerOrReferenceType()) {
+ if (T->isReferenceType()) {
+ const QualType QType = T->getPointeeType();
+ if (!QType.isNull())
+ T = QType.getTypePtr();
+ } else
+ T = T->getPointeeOrArrayElementType();
+ }
+
+ return T;
+}
+
+static bool isLiteralType(QualType QT, const ASTContext &Ctx,
+ const bool ConservativeLiteralType);
+
+static bool isLiteralType(const Type *T, const ASTContext &Ctx,
+ const bool ConservativeLiteralType) {
+ if (!T)
+ return false;
+
+ if (!T->isLiteralType(Ctx))
+ return false;
+
+ if (!ConservativeLiteralType)
+ return T->isLiteralType(Ctx) && !T->isVoidType();
+
+ if (T->isIncompleteType() || T->isIncompleteArrayType())
+ return false;
+
+ T = unwrapPointee(T);
+ if (!T)
+ return false;
+
+ assert(!T->isPointerOrReferenceType());
+
+ if (T->isIncompleteType() || T->isIncompleteArrayType())
+ return false;
+
+ if (T->isLiteralType(Ctx))
+ return true;
+
+ if (const CXXRecordDecl *Rec = T->getAsCXXRecordDecl()) {
+ if (llvm::any_of(Rec->ctors(), [](const CXXConstructorDecl *Ctor) {
+ return !Ctor->isCopyOrMoveConstructor() &&
+ Ctor->isConstexprSpecified();
+ }))
+ return false;
+
+ for (const CXXBaseSpecifier Base : Rec->bases()) {
+ if (!isLiteralType(Base.getType(), Ctx, ConservativeLiteralType))
+ return false;
+ }
+ }
+
+ if (const Type *ArrayElementType = T->getArrayElementTypeNoTypeQual())
+ return isLiteralType(ArrayElementType, Ctx, ConservativeLiteralType);
+
+ return false;
+}
+
+static bool isLiteralType(QualType QT, const ASTContext &Ctx,
+ const bool ConservativeLiteralType) {
+ return !QT.isVolatileQualified() &&
+ isLiteralType(QT.getTypePtr(), Ctx, ConservativeLiteralType);
+}
+
+static bool satisfiesProperties11(
+ const FunctionDecl *FDecl, ASTContext &Ctx,
+ const bool ConservativeLiteralType,
+ const bool AddConstexprToMethodOfClassWithoutConstexprConstructor) {
+ if (FDecl->isConstexprSpecified())
+ return true;
+
+ const LangOptions LO = Ctx.getLangOpts();
+ const auto *Method = llvm::dyn_cast<CXXMethodDecl>(FDecl);
+ if (Method && !Method->isStatic() &&
+ !Method->getParent()->hasConstexprNonCopyMoveConstructor() &&
+ !AddConstexprToMethodOfClassWithoutConstexprConstructor)
+ return false;
+
+ if (Method &&
+ (Method->isVirtual() ||
+ !match(cxxMethodDecl(hasBody(cxxTryStmt())), *Method, Ctx).empty()))
+ return false;
+
+ if (const auto *Ctor = llvm::dyn_cast<CXXConstructorDecl>(FDecl);
+ Ctor && (!satisfiesConstructorPropertiesUntil20(Ctor, Ctx) ||
+ llvm::any_of(Ctor->getParent()->bases(),
+ [](const CXXBaseSpecifier &Base) {
+ return Base.isVirtual();
+ })))
+ return false;
+
+ if (const auto *Dtor = llvm::dyn_cast<CXXDestructorDecl>(FDecl);
+ Dtor && !Dtor->isTrivial())
+ return false;
+
+ if (!isLiteralType(FDecl->getReturnType(), Ctx, ConservativeLiteralType))
+ return false;
+
+ for (const ParmVarDecl *Param : FDecl->parameters())
+ if (!isLiteralType(Param->getType(), Ctx, ConservativeLiteralType))
+ return false;
+
+ class Visitor11 : public clang::RecursiveASTVisitor<Visitor11> {
+ public:
+ using Base = clang::RecursiveASTVisitor<Visitor11>;
+ bool shouldVisitImplicitCode() const { return true; }
+
+ Visitor11(ASTContext &Ctx, bool ConservativeLiteralType)
+ : Ctx(Ctx), ConservativeLiteralType(ConservativeLiteralType) {}
+
+ bool WalkUpFromNullStmt(NullStmt *) {
+ Possible = false;
+ return false;
+ }
+ bool WalkUpFromDeclStmt(DeclStmt *DS) {
+ for (const Decl *D : DS->decls())
+ if (!llvm::isa<StaticAssertDecl, TypedefNameDecl, UsingDecl,
+ UsingDirectiveDecl>(D)) {
+ Possible = false;
+ return false;
+ }
+ return true;
+ }
+
+ bool WalkUpFromExpr(Expr *) { return true; }
+ bool WalkUpFromCompoundStmt(CompoundStmt *S) {
+ for (const DynTypedNode &Node : Ctx.getParents(*S))
+ if (Node.get<FunctionDecl>() != nullptr)
+ return true;
+
+ Possible = false;
+ return false;
+ }
+ bool WalkUpFromStmt(Stmt *) {
+ Possible = false;
+ return false;
+ }
+
+ bool WalkUpFromReturnStmt(ReturnStmt *S) {
+ ++NumReturns;
+ if (NumReturns != 1U) {
+ Possible = false;
+ return false;
+ }
+ return true;
+ }
+
+ bool WalkUpFromCastExpr(CastExpr *CE) {
+ if (llvm::is_contained(
+ {
+ CK_LValueBitCast,
+ CK_IntegralToPointer,
+ CK_PointerToIntegral,
+ },
+ CE->getCastKind())) {
+ Possible = false;
+ return false;
+ }
+ return true;
+ }
+
+ bool TraverseCXXDynamicCastExpr(CXXDynamicCastExpr *) {
+ Possible = false;
+ return false;
+ }
+
+ bool TraverseCXXReinterpretCastExpr(CXXReinterpretCastExpr *) {
+ Possible = false;
+ return false;
+ }
+
+ bool TraverseType(QualType QT) {
+ if (QT.isNull())
+ return true;
+ if (!isLiteralType(QT, Ctx, ConservativeLiteralType)) {
+ Possible = false;
+ return false;
+ }
+ return Base::TraverseType(QT);
+ }
+
+ bool WalkUpFromCXXConstructExpr(CXXConstructExpr *CE) {
+ if (const CXXConstructorDecl *Ctor = CE->getConstructor();
+ Ctor && !Ctor->isConstexprSpecified()) {
+ Possible = false;
+ return false;
+ }
+
+ return true;
+ }
+ bool WalkUpFromCallExpr(CallExpr *CE) {
+ if (const auto *FDecl =
+ llvm::dyn_cast_if_present<FunctionDecl>(CE->getCalleeDecl());
+ FDecl && !FDecl->isConstexprSpecified()) {
+ Possible = false;
+ return false;
+ }
+ return true;
+ }
+
+ bool TraverseCXXNewExpr(CXXNewExpr *) {
+ Possible = false;
+ return false;
+ }
+
+ bool TraverseDeclRefExpr(DeclRefExpr *DRef) {
+ if (DRef->getType().isVolatileQualified()) {
+ Possible = false;
+ return false;
+ }
+ return Base::TraverseDeclRefExpr(DRef);
+ }
+
+ ASTContext &Ctx;
+ const bool ConservativeLiteralType;
+ bool Possible = true;
+ size_t NumReturns = 0;
+ };
+
+ Visitor11 V{Ctx, ConservativeLiteralType};
+ V.TraverseDecl(const_cast<FunctionDecl *>(FDecl));
+ if (!V.Possible)
+ return false;
+
+ return true;
+}
+
+// The only difference between C++14 and C++17 is that `constexpr` lambdas
+// can be used in C++17.
+static bool satisfiesProperties1417(
+ const FunctionDecl *FDecl, ASTContext &Ctx,
+ const bool ConservativeLiteralType,
+ const bool AddConstexprToMethodOfClassWithoutConstexprConstructor) {
+ if (FDecl->isConstexprSpecified())
+ return true;
+
+ const LangOptions LO = Ctx.getLangOpts();
+ const auto *Method = llvm::dyn_cast<CXXMethodDecl>(FDecl);
+ if (Method && !Method->isStatic() &&
+ !Method->getParent()->hasConstexprNonCopyMoveConstructor() &&
+ !AddConstexprToMethodOfClassWithoutConstexprConstructor)
+ return false;
+
+ if (Method && Method->isVirtual())
+ return false;
+
+ if (llvm::isa<CXXConstructorDecl>(FDecl) &&
+ llvm::any_of(
+ Method->getParent()->bases(),
+ [](const CXXBaseSpecifier &Base) { return Base.isVirtual(); }))
+ return false;
+
+ if (!isLiteralType(FDecl->getReturnType(), Ctx, ConservativeLiteralType))
+ return false;
+
+ for (const ParmVarDecl *Param : FDecl->parameters())
+ if (!isLiteralType(Param->getType(), Ctx, ConservativeLiteralType))
+ return false;
+
+ class Visitor14 : public clang::RecursiveASTVisitor<Visitor14> {
+ public:
+ using Base = clang::RecursiveASTVisitor<Visitor14>;
+ bool shouldVisitImplicitCode() const { return true; }
+
+ Visitor14(bool CXX17, ASTContext &Ctx, bool ConservativeLiteralType,
+ bool AddConstexprToMethodOfClassWithoutConstexprConstructor)
+ : CXX17(CXX17), Ctx(Ctx),
+ ConservativeLiteralType(ConservativeLiteralType),
+ AddConstexprToMethodOfClassWithoutConstexprConstructor(
+ AddConstexprToMethodOfClassWithoutConstexprConstructor) {}
+
+ bool TraverseGotoStmt(GotoStmt *) {
+ Possible = false;
+ return false;
+ }
+ bool TraverseLabelStmt(LabelStmt *) {
+ Possible = false;
+ return false;
+ }
+ bool TraverseCXXTryStmt(CXXTryStmt *) {
+ Possible = false;
+ return false;
+ }
+ bool TraverseGCCAsmStmt(GCCAsmStmt *) {
+ Possible = false;
+ return false;
+ }
+ bool TraverseMSAsmStmt(MSAsmStmt *) {
+ Possible = false;
+ return false;
+ }
+ bool TraverseDecompositionDecl(DecompositionDecl * /*DD*/) {
+ Possible = false;
+ return false;
+ }
+ bool TraverseVarDecl(VarDecl *VD) {
+ const StorageDuration StorageDur = VD->getStorageDuration();
+ Possible = VD->hasInit() &&
+ isLiteralType(VD->getType(), VD->getASTContext(),
+ ConservativeLiteralType) &&
+ (StorageDur != StorageDuration::SD_Static &&
+ StorageDur != StorageDuration::SD_Thread);
+ return Possible && Base::TraverseVarDecl(VD);
+ }
+ bool TraverseLambdaExpr(LambdaExpr *LE) {
+ if (CXX17) {
+ Possible = satisfiesProperties1417(
+ LE->getCallOperator(), Ctx, ConservativeLiteralType,
+ AddConstexprToMethodOfClassWithoutConstexprConstructor);
+ return Possible;
+ }
+ Possible = false;
+ return false;
+ }
+ bool TraverseCXXNewExpr(CXXNewExpr *) {
+ Possible = false;
+ return false;
+ }
+
+ bool TraverseDeclRefExpr(DeclRefExpr *DRef) {
+ if (const auto *D = llvm::dyn_cast_if_present<VarDecl>(DRef->getDecl());
+ D && !D->isLocalVarDeclOrParm() && D->hasGlobalStorage()) {
+ Possible = false;
+ return false;
+ }
+
+ if (DRef->getType().isVolatileQualified()) {
+ Possible = false;
+ return false;
+ }
+ return true;
+ }
+
+ bool WalkUpFromCastExpr(CastExpr *CE) {
+ if (llvm::is_contained(
+ {
+ CK_LValueBitCast,
+ CK_IntegralToPointer,
+ CK_PointerToIntegral,
+ },
+ CE->getCastKind())) {
+ Possible = false;
+ return false;
+ }
+ return true;
+ }
+
+ bool TraverseCXXDynamicCastExpr(CXXDynamicCastExpr *) {
+ Possible = false;
+ return false;
+ }
+
+ bool TraverseCXXReinterpretCastExpr(CXXReinterpretCastExpr *) {
+ Possible = false;
+ return false;
+ }
+
+ bool TraverseType(QualType QT) {
+ if (QT.isNull())
+ return true;
+ if (!isLiteralType(QT, Ctx, ConservativeLiteralType)) {
+ Possible = false;
+ return false;
+ }
+ return Base::TraverseType(QT);
+ }
+
+ bool WalkUpFromCXXConstructExpr(CXXConstructExpr *CE) {
+ if (const CXXConstructorDecl *Ctor = CE->getConstructor();
+ Ctor && !Ctor->isConstexprSpecified()) {
+ Possible = false;
+ return false;
+ }
+
+ return true;
+ }
+ bool WalkUpFromCallExpr(CallExpr *CE) {
+ if (const auto *FDecl =
+ llvm::dyn_cast_if_present<FunctionDecl>(CE->getCalleeDecl());
+ FDecl && !FDecl->isConstexprSpecified()) {
+ Possible = false;
+ return false;
+ }
+ return true;
+ }
+
+ const bool CXX17;
+ bool Possible = true;
+ ASTContext &Ctx;
+ const bool ConservativeLiteralType;
+ const bool AddConstexprToMethodOfClassWithoutConstexprConstructor;
+ };
+
+ Visitor14 V{Ctx.getLangOpts().CPlusPlus17 != 0, Ctx, ConservativeLiteralType,
+ AddConstexprToMethodOfClassWithoutConstexprConstructor};
+ V.TraverseDecl(const_cast<FunctionDecl *>(FDecl));
+ if (!V.Possible)
+ return false;
+
+ if (const auto *Ctor = llvm::dyn_cast<CXXConstructorDecl>(FDecl);
+ Ctor && !satisfiesConstructorPropertiesUntil20(Ctor, Ctx))
+ return false;
+
+ if (const auto *Dtor = llvm::dyn_cast<CXXDestructorDecl>(FDecl);
+ Dtor && !Dtor->isTrivial())
+ return false;
+
+ return true;
+}
+
+static bool satisfiesProperties20(
+ const FunctionDecl *FDecl, ASTContext &Ctx,
+ const bool ConservativeLiteralType,
+ const bool AddConstexprToMethodOfClassWithoutConstexprConstructor) {
+ if (FDecl->isConstexprSpecified())
+ return true;
+
+ const LangOptions LO = Ctx.getLangOpts();
+ const auto *Method = llvm::dyn_cast<CXXMethodDecl>(FDecl);
+ if (Method && !Method->isStatic() &&
+ !Method->getParent()->hasConstexprNonCopyMoveConstructor() &&
+ !AddConstexprToMethodOfClassWithoutConstexprConstructor)
+ return false;
+
+ if (FDecl->hasBody() && llvm::isa<CoroutineBodyStmt>(FDecl->getBody()))
+ return false;
+
+ if ((llvm::isa<CXXConstructorDecl>(FDecl) ||
+ llvm::isa<CXXDestructorDecl>(FDecl)) &&
+ llvm::any_of(
+ Method->getParent()->bases(),
+ [](const CXXBaseSpecifier &Base) { return Base.isVirtual(); }))
+ return false;
+
+ if (!isLiteralType(FDecl->getReturnType(), Ctx, ConservativeLiteralType))
+ return false;
+
+ for (const ParmVarDecl *Param : FDecl->parameters())
+ if (!isLiteralType(Param->getType(), Ctx, ConservativeLiteralType))
+ return false;
+
+ class Visitor20 : public clang::RecursiveASTVisitor<Visitor20> {
+ public:
+ bool shouldVisitImplicitCode() const { return true; }
+
+ Visitor20(bool ConservativeLiteralType)
+ : ConservativeLiteralType(ConservativeLiteralType) {}
+
+ bool TraverseGotoStmt(GotoStmt *) {
+ Possible = false;
+ return false;
+ }
+ bool TraverseLabelStmt(LabelStmt *) {
+ Possible = false;
+ return false;
+ }
+ bool TraverseCXXTryStmt(CXXTryStmt *) {
+ Possible = false;
+ return false;
+ }
+ bool TraverseGCCAsmStmt(GCCAsmStmt *) {
+ Possible = false;
+ return false;
+ }
+ bool TraverseMSAsmStmt(MSAsmStmt *) {
+ Possible = false;
+ return false;
+ }
+ bool TraverseDecompositionDecl(DecompositionDecl * /*DD*/) {
+ Possible = false;
+ return false;
+ }
+ bool TraverseVarDecl(VarDecl *VD) {
+ const StorageDuration StorageDur = VD->getStorageDuration();
+ Possible = isLiteralType(VD->getType(), VD->getASTContext(),
+ ConservativeLiteralType) &&
+ (StorageDur != StorageDuration::SD_Static &&
+ StorageDur != StorageDuration::SD_Thread);
+ return Possible;
+ }
+
+ bool WalkUpFromCastExpr(CastExpr *CE) {
+ if (llvm::is_contained(
+ {
+ CK_LValueBitCast,
+ CK_IntegralToPointer,
+ CK_PointerToIntegral,
+ },
+ CE->getCastKind())) {
+ Possible = false;
+ return false;
+ }
+ return true;
+ }
+
+ bool TraverseCXXReinterpretCastExpr(CXXReinterpretCastExpr *) {
+ Possible = false;
+ return false;
+ }
+
+ bool TraverseDeclRefExpr(DeclRefExpr *DRef) {
+ if (DRef->getType().isVolatileQualified()) {
+ Possible = false;
+ return false;
+ }
+ return true;
+ }
+
+ bool Possible = true;
+ bool ConservativeLiteralType;
+ };
+
+ Visitor20 V{ConservativeLiteralType};
+ V.TraverseDecl(const_cast<FunctionDecl *>(FDecl));
+ if (!V.Possible)
+ return false;
+
+ if (const auto *Ctor = llvm::dyn_cast<CXXConstructorDecl>(FDecl))
+ satisfiesConstructorPropertiesUntil20(Ctor, Ctx);
+
+ if (const auto *Dtor = llvm::dyn_cast<CXXDestructorDecl>(FDecl);
+ Dtor && !Dtor->isTrivial())
+ return false;
+
+ class BodyVisitor : public clang::RecursiveASTVisitor<BodyVisitor> {
+ public:
+ using Base = clang::RecursiveASTVisitor<BodyVisitor>;
+ bool shouldVisitImplicitCode() const { return true; }
+
+ explicit BodyVisitor(const ASTContext &Ctx, bool ConservativeLiteralType)
+ : Ctx(Ctx), LO(Ctx.getLangOpts()),
+ ConservativeLiteralType(ConservativeLiteralType) {}
+
+ bool TraverseType(QualType QT) {
+ if (QT.isNull())
+ return true;
+ if (!isLiteralType(QT, Ctx, ConservativeLiteralType)) {
+ Possible = false;
+ return false;
+ }
+ return Base::TraverseType(QT);
+ }
+
+ bool WalkUpFromCXXConstructExpr(CXXConstructExpr *CE) {
+ if (const CXXConstructorDecl *Ctor = CE->getConstructor();
+ Ctor && !Ctor->isConstexprSpecified()) {
+ Possible = false;
+ return false;
+ }
+
+ return true;
+ }
+ bool WalkUpFromCallExpr(CallExpr *CE) {
+ if (const auto *FDecl =
+ llvm::dyn_cast_if_present<FunctionDecl>(CE->getCalleeDecl());
+ FDecl && !FDecl->isConstexprSpecified()) {
+ Possible = false;
+ return false;
+ }
+ return true;
+ }
+
+ const ASTContext &Ctx;
+ const LangOptions &LO;
+ const bool ConservativeLiteralType;
+ bool Possible = true;
+ };
+
+ if (FDecl->hasBody() && ConservativeLiteralType) {
+ BodyVisitor Visitor(Ctx, ConservativeLiteralType);
+ Visitor.TraverseStmt(FDecl->getBody());
+ if (!Visitor.Possible)
+ return false;
+ }
+ return true;
+}
+
+static bool satisfiesProperties2326(
+ const FunctionDecl *FDecl, ASTContext &Ctx,
+ const bool AddConstexprToMethodOfClassWithoutConstexprConstructor) {
+ if (FDecl->isConstexprSpecified())
+ return true;
+
+ const LangOptions LO = Ctx.getLangOpts();
+ const auto *Method = llvm::dyn_cast<CXXMethodDecl>(FDecl);
+ if (Method && !Method->isStatic() &&
+ !Method->getParent()->hasConstexprNonCopyMoveConstructor() &&
+ !AddConstexprToMethodOfClassWithoutConstexprConstructor)
+ return false;
+
+ if (FDecl->hasBody() && llvm::isa<CoroutineBodyStmt>(FDecl->getBody()))
+ return false;
+
+ if ((llvm::isa<CXXConstructorDecl>(FDecl) ||
+ llvm::isa<CXXDestructorDecl>(FDecl)) &&
+ llvm::any_of(
+ Method->getParent()->bases(),
+ [](const CXXBaseSpecifier &Base) { return Base.isVirtual(); }))
+ return false;
+ return true;
+}
+
+namespace {
+// FIXME: fix CXX23 allowing decomposition decls, but it is only a feature
since
+// CXX26
+AST_MATCHER_P2(FunctionDecl, satisfiesProperties, bool,
ConservativeLiteralType,
+ bool, AddConstexprToMethodOfClassWithoutConstexprConstructor) {
+ ASTContext &Ctx = Finder->getASTContext();
+ const LangOptions LO = Ctx.getLangOpts();
+
+ if (LO.CPlusPlus26) {
+ return satisfiesProperties2326(
+ &Node, Ctx, AddConstexprToMethodOfClassWithoutConstexprConstructor);
+ }
+ if (LO.CPlusPlus23) {
+ return satisfiesProperties2326(
+ &Node, Ctx, AddConstexprToMethodOfClassWithoutConstexprConstructor);
+ }
+ if (LO.CPlusPlus20) {
+ return satisfiesProperties20(
+ &Node, Ctx, ConservativeLiteralType,
+ AddConstexprToMethodOfClassWithoutConstexprConstructor);
+ }
+ if (LO.CPlusPlus17) {
+ return satisfiesProperties1417(
+ &Node, Ctx, ConservativeLiteralType,
+ AddConstexprToMethodOfClassWithoutConstexprConstructor);
+ }
+ if (LO.CPlusPlus14) {
+ return satisfiesProperties1417(
+ &Node, Ctx, ConservativeLiteralType,
+ AddConstexprToMethodOfClassWithoutConstexprConstructor);
+ }
+ if (LO.CPlusPlus11)
+ return satisfiesProperties11(
+ &Node, Ctx, ConservativeLiteralType,
+ AddConstexprToMethodOfClassWithoutConstexprConstructor);
+
+ return false;
+}
+
+AST_MATCHER_P(VarDecl, satisfiesVariableProperties, bool,
+ ConservativeLiteralType) {
+ ASTContext &Ctx = Finder->getASTContext();
+ const LangOptions LO = Ctx.getLangOpts();
+
+ const QualType QT = Node.getType();
+ const Type *T = QT.getTypePtr();
+ if (!T)
+ return false;
+
+ if (!isLiteralType(QT, Ctx, ConservativeLiteralType))
+ return false;
+
+ const bool IsDeclaredInsideConstexprFunction = std::invoke([&Node]() {
+ const auto *Func = llvm::dyn_cast<FunctionDecl>(Node.getDeclContext());
+ if (!Func)
+ return false;
+ return !Func->isConstexpr();
+ });
+
+ if (!Finder->getASTContext().getLangOpts().CPlusPlus23 &&
+ Node.isStaticLocal() && IsDeclaredInsideConstexprFunction)
+ return false;
+
+ if (!Finder->getASTContext().getLangOpts().CPlusPlus20)
+ return true;
+
+ const CXXRecordDecl *RDecl = T->getAsCXXRecordDecl();
+ const Type *const ArrayOrPtrElement = T->getPointeeOrArrayElementType();
+ if (ArrayOrPtrElement)
+ RDecl = ArrayOrPtrElement->getAsCXXRecordDecl();
+
+ if (RDecl && (!RDecl->hasDefinition() || !RDecl->hasConstexprDestructor()))
+ return false;
+
+ return true;
+}
+} // namespace
+
+void UseConstexprCheck::registerMatchers(MatchFinder *Finder) {
+ Finder->addMatcher(
+ functionDecl(
+ isDefinition(),
+ unless(anyOf(isConstexpr(), isImplicit(), hasExternalFormalLinkage(),
+ isInMacro(), isMain(), isInStdNamespace(),
+ isExpansionInSystemHeader(), isExternC(),
+ cxxMethodDecl(ofClass(cxxRecordDecl(isLambda()))))),
+ locationPermitsConstexpr(), allRedeclsInSameFile(),
+ satisfiesProperties(
+ ConservativeLiteralType,
+ AddConstexprToMethodOfClassWithoutConstexprConstructor))
+ .bind("func"),
+ this);
+
+ Finder->addMatcher(
+ varDecl(
+ unless(anyOf(parmVarDecl(), isImplicit(), isInStdNamespace(),
+ isExpansionInSystemHeader(), isConstexpr(), isExternC(),
+ hasExternalFormalLinkage(), isInMacro())),
+ hasNoRedecl(), hasType(qualType(isConstQualified())),
+ satisfiesVariableProperties(ConservativeLiteralType),
+ hasInitializer(expr(isCXX11ConstantExpr())))
+ .bind("var"),
+ this);
+}
+
+void UseConstexprCheck::check(const MatchFinder::MatchResult &Result) {
+ constexpr const auto MaybeResolveToTemplateDecl =
+ [](const FunctionDecl *Func) {
+ if (Func && Func->isTemplateInstantiation())
+ Func = Func->getTemplateInstantiationPattern();
+ return Func;
+ };
+
+ if (const auto *Func = Result.Nodes.getNodeAs<FunctionDecl>("func")) {
+ Func = MaybeResolveToTemplateDecl(Func);
+ if (Func)
+ Functions.insert(Func);
+ return;
+ }
+
+ if (const auto *Var = Result.Nodes.getNodeAs<VarDecl>("var")) {
+ if (const VarDecl *VarTemplate = Var->getTemplateInstantiationPattern())
+ Var = VarTemplate;
+
+ VariableMapping.insert({Var, MaybeResolveToTemplateDecl(
+ llvm::dyn_cast_if_present<FunctionDecl>(
+ Var->getDeclContext()))});
+ return;
+ }
+}
+
+void UseConstexprCheck::onEndOfTranslationUnit() {
+ const std::string FunctionReplacement = ConstexprString + " ";
+ for (const FunctionDecl *Func : Functions) {
+ const SourceRange R =
+ SourceRange(Func->getTypeSpecStartLoc(), Func->getLocation());
+ auto Diag =
+ diag(Func->getLocation(), "function %0 can be declared 'constexpr'")
+ << Func << R;
+
+ for (const Decl *D : Func->redecls())
+ if (const auto *FDecl = llvm::dyn_cast<FunctionDecl>(D))
+ Diag << FixItHint::CreateInsertion(FDecl->getTypeSpecStartLoc(),
+ FunctionReplacement);
+ }
+
+ const std::string VariableReplacementWithStatic = StaticConstexprString + "
";
+ const auto VariableReplacement =
+ [&FunctionReplacement, this, &VariableReplacementWithStatic](
+ const VarDecl *Var, const FunctionDecl *FuncCtx,
+ const bool IsAddingConstexprToFuncCtx) -> const std::string & {
+ if (!FuncCtx)
+ return FunctionReplacement;
+
+ if (!getLangOpts().CPlusPlus23)
+ return FunctionReplacement;
+
+ // We'll prefer the function to be constexpr over the function not being
+ // constexpr just for the var to be static constexpr instead of just
+ // constexpr.
+ if (IsAddingConstexprToFuncCtx)
+ return FunctionReplacement;
+
+ if (Var->isStaticLocal())
+ return FunctionReplacement;
+
+ return VariableReplacementWithStatic;
+ };
+
+ for (const auto &[Var, FuncCtx] : VariableMapping) {
+ const bool IsAddingConstexprToFuncCtx = Functions.contains(FuncCtx);
+ if (FuncCtx && getLangOpts().CPlusPlus23 && Var->isStaticLocal() &&
+ IsAddingConstexprToFuncCtx)
+ continue;
+ const SourceRange R =
+ SourceRange(Var->getTypeSpecStartLoc(), Var->getLocation());
+ auto Diag =
+ diag(Var->getLocation(), "variable %0 can be declared 'constexpr'")
+ << Var << R
+ << FixItHint::CreateInsertion(
+ Var->getTypeSpecStartLoc(),
+ VariableReplacement(Var, FuncCtx, IsAddingConstexprToFuncCtx));
+ // Since either of the locs can be in a macro, use `makeFileCharRange` to
be
+ // sure that we have a consistent `CharSourceRange`, located entirely in
the
+ // source file.
+ const CharSourceRange FileRange = Lexer::makeFileCharRange(
+ CharSourceRange::getCharRange(Var->getInnerLocStart(),
+ Var->getLocation()),
+ Var->getASTContext().getSourceManager(), getLangOpts());
+ if (const std::optional<Token> ConstToken =
+ utils::lexer::getQualifyingToken(
+ tok::TokenKind::kw_const, FileRange, Var->getASTContext(),
+ Var->getASTContext().getSourceManager())) {
+ Diag << FixItHint::CreateRemoval(ConstToken->getLocation());
+ }
+ }
+
+ Functions.clear();
+ VariableMapping.clear();
+}
+
+UseConstexprCheck::UseConstexprCheck(StringRef Name, ClangTidyContext *Context)
+ : ClangTidyCheck(Name, Context),
+ ConservativeLiteralType(Options.get("ConservativeLiteralType", true)),
+ AddConstexprToMethodOfClassWithoutConstexprConstructor(Options.get(
+ "AddConstexprToMethodOfClassWithoutConstexprConstructor", false)),
+ ConstexprString(Options.get("ConstexprString", "constexpr")),
+ StaticConstexprString(
+ Options.get("StaticConstexprString", "static " + ConstexprString)) {}
+void UseConstexprCheck::storeOptions(ClangTidyOptions::OptionMap &Opts) {
----------------
vbvictor wrote:
```suggestion
Options.get("StaticConstexprString", "static " + ConstexprString)) {}
void UseConstexprCheck::storeOptions(ClangTidyOptions::OptionMap &Opts) {
```
https://github.com/llvm/llvm-project/pull/146553
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