clang-tools-extra/clang-tidy/performance/UnnecessaryCopyInitialization.h

//===--- UnnecessaryCopyInitialization.h - clang-tidy------------*- 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
//
//===----------------------------------------------------------------------===//

#ifndef LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_PERFORMANCE_UNNECESSARY_COPY_INITIALIZATION_H
#define LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_PERFORMANCE_UNNECESSARY_COPY_INITIALIZATION_H

#include "../ClangTidyCheck.h"
#include "clang/AST/Decl.h"

namespace clang::tidy::performance {

// The check detects local variable declarations that are copy initialized with
// the const reference of a function call or the const reference of a method
// call whose object is guaranteed to outlive the variable's scope and suggests
// to use a const reference.
//
// The check currently only understands a subset of variables that are
// guaranteed to outlive the const reference returned, namely: const variables,
// const references, and const pointers to const.
class UnnecessaryCopyInitialization : public ClangTidyCheck {
public:
  UnnecessaryCopyInitialization(StringRef Name, ClangTidyContext *Context);
  bool isLanguageVersionSupported(const LangOptions &LangOpts) const override {
    return LangOpts.CPlusPlus;
  }
  void registerMatchers(ast_matchers::MatchFinder *Finder) override;
  void check(const ast_matchers::MatchFinder::MatchResult &Result) override;
  void storeOptions(ClangTidyOptions::OptionMap &Opts) override;

protected:
  // A helper to manipulate the state common to
  // `CopyFromMethodReturn` and `CopyFromLocalVar`.
  struct CheckContext {
    const VarDecl &Var;
    const Stmt &BlockStmt;
    const DeclStmt &VarDeclStmt;
    clang::ASTContext &ASTCtx;
    const bool IssueFix;
    const bool IsVarUnused;
    const bool IsVarOnlyUsedAsConst;
  };

  // Create diagnostics. These are virtual so that derived classes can change
  // behaviour.
  virtual void diagnoseCopyFromMethodReturn(const CheckContext &Ctx);
  virtual void diagnoseCopyFromLocalVar(const CheckContext &Ctx,
                                        const VarDecl &OldVar);

private:
  void handleCopyFromMethodReturn(const CheckContext &Ctx,
                                  const VarDecl *ObjectArg);
  void handleCopyFromLocalVar(const CheckContext &Ctx, const VarDecl &OldVar);

  void maybeIssueFixes(const CheckContext &Ctx, DiagnosticBuilder &Diagnostic);

  const std::vector<StringRef> AllowedTypes;
  const std::vector<StringRef> ExcludedContainerTypes;
};

} // namespace clang::tidy::performance

#endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_PERFORMANCE_UNNECESSARY_COPY_INITIALIZATION_H