MisleadingCaptureDefaultByValueCheck.cpp

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//===----------------------------------------------------------------------===//
//
// 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 "MisleadingCaptureDefaultByValueCheck.h"
#include "../utils/LexerUtils.h"
#include "clang/AST/ASTContext.h"
#include "clang/ASTMatchers/ASTMatchFinder.h"
#include "llvm/Support/raw_ostream.h"
 
#include <algorithm>
 
using namespace clang::ast_matchers;
 
namespace clang::tidy::cppcoreguidelines {
 
MisleadingCaptureDefaultByValueCheck::MisleadingCaptureDefaultByValueCheck(
    StringRef Name, ClangTidyContext *Context)
    : ClangTidyCheck(Name, Context) {}
 
void MisleadingCaptureDefaultByValueCheck::registerMatchers(
    MatchFinder *Finder) {
  Finder->addMatcher(lambdaExpr(hasAnyCapture(capturesThis())).bind("lambda"),
                     this);
}
 
static SourceLocation findDefaultCaptureEnd(const LambdaExpr *Lambda,
                                            ASTContext &Context) {
  for (const LambdaCapture &Capture : Lambda->explicit_captures()) {
    if (Capture.isExplicit()) {
      if (Capture.getCaptureKind() == LCK_ByRef) {
        const SourceManager &SourceMgr = Context.getSourceManager();
        SourceLocation AddressofLoc = utils::lexer::findPreviousTokenKind(
            Capture.getLocation(), SourceMgr, Context.getLangOpts(), tok::amp);
        return AddressofLoc;
      }
      return Capture.getLocation();
    }
  }
  return Lambda->getIntroducerRange().getEnd();
}
 
static std::string createReplacementText(const LambdaExpr *Lambda) {
  std::string Replacement;
  llvm::raw_string_ostream Stream(Replacement);
 
  auto AppendName = [&](llvm::StringRef Name) {
    if (!Replacement.empty())
      Stream << ", ";
    if (Lambda->getCaptureDefault() == LCD_ByRef && Name != "this")
      Stream << "&" << Name;
    else
      Stream << Name;
  };
 
  for (const LambdaCapture &Capture : Lambda->implicit_captures()) {
    assert(Capture.isImplicit());
    if (Capture.capturesVariable() && Capture.isImplicit())
      AppendName(Capture.getCapturedVar()->getName());
    else if (Capture.capturesThis())
      AppendName("this");
  }
  if (!Replacement.empty() && !Lambda->explicit_captures().empty()) {
    // Add back separator if we are adding explicit capture variables.
    Stream << ", ";
  }
  return Replacement;
}
 
void MisleadingCaptureDefaultByValueCheck::check(
    const MatchFinder::MatchResult &Result) {
  const auto *Lambda = Result.Nodes.getNodeAs<LambdaExpr>("lambda");
  if (!Lambda)
    return;
 
  if (Lambda->getCaptureDefault() == LCD_ByCopy) {
    const bool IsThisImplicitlyCaptured = std::any_of(
        Lambda->implicit_capture_begin(), Lambda->implicit_capture_end(),
        [](const LambdaCapture &Capture) { return Capture.capturesThis(); });
    auto Diag = diag(Lambda->getCaptureDefaultLoc(),
                     "lambdas that %select{|implicitly }0capture 'this' "
                     "should not specify a by-value capture default")
                << IsThisImplicitlyCaptured;
 
    const std::string ReplacementText = createReplacementText(Lambda);
    const SourceLocation DefaultCaptureEnd =
        findDefaultCaptureEnd(Lambda, *Result.Context);
    Diag << FixItHint::CreateReplacement(
        CharSourceRange::getCharRange(Lambda->getCaptureDefaultLoc(),
                                      DefaultCaptureEnd),
        ReplacementText);
  }
}
 
} // namespace clang::tidy::cppcoreguidelines