151 lines · cpp
1//===--- SpecialMembers.cpp - Generate C++ special member functions -------===//2//3// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.4// See https://llvm.org/LICENSE.txt for license information.5// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception6//7//===----------------------------------------------------------------------===//8#include "ParsedAST.h"9#include "refactor/InsertionPoint.h"10#include "refactor/Tweak.h"11#include "clang/AST/DeclCXX.h"12#include "clang/Sema/Sema.h"13#include "clang/Tooling/Core/Replacement.h"14#include "llvm/ADT/StringRef.h"15#include "llvm/Support/Casting.h"16#include "llvm/Support/Error.h"17 18namespace clang {19namespace clangd {20namespace {21 22// Returns code to declare missing copy/move constructors/assignment operators.23// They will be deleted or defaulted to match the class's current state.24std::string buildSpecialMemberDeclarations(const CXXRecordDecl &Class) {25 struct Members {26 const CXXMethodDecl *Copy = nullptr;27 const CXXMethodDecl *Move = nullptr;28 } Ctor, Assign;29 30 for (const auto &M : Class.methods()) {31 if (M->isCopyAssignmentOperator())32 Assign.Copy = M;33 else if (M->isMoveAssignmentOperator())34 Assign.Move = M;35 if (const auto *C = llvm::dyn_cast<CXXConstructorDecl>(M)) {36 if (C->isCopyConstructor())37 Ctor.Copy = C;38 else if (C->isMoveConstructor())39 Ctor.Move = C;40 }41 }42 43 std::string S;44 llvm::raw_string_ostream OS(S);45 46 auto PrintMember = [&](const CXXMethodDecl *D, const char *MemberPattern,47 const char *ParmPattern) {48 if (D && !D->isImplicit())49 return;50 bool Delete = !D || D->isDeleted();51 OS << llvm::formatv(52 "{0} = {1};\n",53 llvm::formatv(MemberPattern, Class.getName(),54 llvm::formatv(ParmPattern, Class.getName())),55 Delete ? "delete" : "default");56 };57 auto PrintMembers = [&](const Members &M, const char *MemberPattern) {58 PrintMember(M.Copy, MemberPattern, /*ParmPattern=*/"const {0}&");59 PrintMember(M.Move, MemberPattern, /*ParmPattern=*/"{0}&&");60 };61 PrintMembers(Ctor, /*MemberPattern=*/"{0}({1})");62 PrintMembers(Assign, /*MemberPattern=*/"{0} &operator=({1})");63 64 return S;65}66 67// A tweak that adds missing declarations of copy & move constructors.68//69// e.g. given `struct ^S{};`, produces:70// struct S {71// S(const S&) = default;72// S(S&&) = default;73// S &operator=(const S&) = default;74// S &operator=(S&&) = default;75// };76//77// Added members are defaulted or deleted to approximately preserve semantics.78// (May not be a strict no-op when they were not implicitly declared).79//80// Having these spelled out is useful:81// - to understand the implicit behavior82// - to avoid relying on the implicit behavior83// - as a baseline for explicit modification84class SpecialMembers : public Tweak {85public:86 const char *id() const final;87 llvm::StringLiteral kind() const override {88 return CodeAction::REFACTOR_KIND;89 }90 std::string title() const override {91 return llvm::formatv("Declare implicit {0} members",92 NeedCopy ? NeedMove ? "copy/move" : "copy" : "move");93 }94 95 bool prepare(const Selection &Inputs) override {96 // This tweak relies on =default and =delete.97 if (!Inputs.AST->getLangOpts().CPlusPlus11)98 return false;99 100 // Trigger only on class definitions.101 if (auto *N = Inputs.ASTSelection.commonAncestor())102 Class = const_cast<CXXRecordDecl *>(N->ASTNode.get<CXXRecordDecl>());103 if (!Class || !Class->isThisDeclarationADefinition() || Class->isUnion())104 return false;105 106 // Tweak is only available if some members are missing.107 NeedCopy = !Class->hasUserDeclaredCopyConstructor() ||108 !Class->hasUserDeclaredCopyAssignment();109 NeedMove = !Class->hasUserDeclaredMoveAssignment() ||110 !Class->hasUserDeclaredMoveConstructor();111 return NeedCopy || NeedMove;112 }113 114 Expected<Effect> apply(const Selection &Inputs) override {115 // Implicit special members are created lazily by clang.116 // We need them so we can tell whether they should be =default or =delete.117 Inputs.AST->getSema().ForceDeclarationOfImplicitMembers(Class);118 std::string Code = buildSpecialMemberDeclarations(*Class);119 120 // Prefer to place the new members...121 std::vector<Anchor> Anchors = {122 // Below the default constructor123 {[](const Decl *D) {124 if (const auto *CCD = llvm::dyn_cast<CXXConstructorDecl>(D))125 return CCD->isDefaultConstructor();126 return false;127 },128 Anchor::Below},129 // Above existing constructors130 {[](const Decl *D) { return llvm::isa<CXXConstructorDecl>(D); },131 Anchor::Above},132 // At the top of the public section133 {[](const Decl *D) { return true; }, Anchor::Above},134 };135 auto Edit = insertDecl(Code, *Class, std::move(Anchors), AS_public);136 if (!Edit)137 return Edit.takeError();138 return Effect::mainFileEdit(Inputs.AST->getSourceManager(),139 tooling::Replacements{std::move(*Edit)});140 }141 142private:143 bool NeedCopy = false, NeedMove = false;144 CXXRecordDecl *Class = nullptr;145};146REGISTER_TWEAK(SpecialMembers)147 148} // namespace149} // namespace clangd150} // namespace clang151