clang-tools-extra/clang-tidy/cppcoreguidelines/MisleadingCaptureDefaultByValueCheck.cpp

   1 //===--- MisleadingCaptureDefaultByValueCheck.cpp - clang-tidy-------------===//
   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-exception
   6 //
   7 //===----------------------------------------------------------------------===//
   8
   9 #include "MisleadingCaptureDefaultByValueCheck.h"
  10 #include "../utils/LexerUtils.h"
  11 #include "clang/AST/ASTContext.h"
  12 #include "clang/ASTMatchers/ASTMatchFinder.h"
  13 #include "llvm/Support/raw_ostream.h"
  14
  15 #include <algorithm>
  16
  17 using namespace clang::ast_matchers;
  18
  19 namespace clang::tidy::cppcoreguidelines {
  20
  21 MisleadingCaptureDefaultByValueCheck::MisleadingCaptureDefaultByValueCheck(
  22     StringRef Name, ClangTidyContext *Context)
  23     : ClangTidyCheck(Name, Context) {}
  24
  25 void MisleadingCaptureDefaultByValueCheck::registerMatchers(
  26     MatchFinder *Finder) {
  27   Finder->addMatcher(lambdaExpr(hasAnyCapture(capturesThis())).bind("lambda"),
  28                      this);
  29 }
  30
  31 static SourceLocation findDefaultCaptureEnd(const LambdaExpr *Lambda,
  32                                             ASTContext &Context) {
  33   for (const LambdaCapture &Capture : Lambda->explicit_captures()) {
  34     if (Capture.isExplicit()) {
  35       if (Capture.getCaptureKind() == LCK_ByRef) {
  36         const SourceManager &SourceMgr = Context.getSourceManager();
  37         SourceLocation AddressofLoc = utils::lexer::findPreviousTokenKind(
  38             Capture.getLocation(), SourceMgr, Context.getLangOpts(), tok::amp);
  39         return AddressofLoc;
  40       } else {
  41         return Capture.getLocation();
  42       }
  43     }
  44   }
  45   return Lambda->getIntroducerRange().getEnd();
  46 }
  47
  48 static std::string createReplacementText(const LambdaExpr *Lambda) {
  49   std::string Replacement;
  50   llvm::raw_string_ostream Stream(Replacement);
  51
  52   auto AppendName = [&](llvm::StringRef Name) {
  53     if (Replacement.size() != 0) {
  54       Stream << ", ";
  55     }
  56     if (Lambda->getCaptureDefault() == LCD_ByRef && Name != "this") {
  57       Stream << "&" << Name;
  58     } else {
  59       Stream << Name;
  60     }
  61   };
  62
  63   for (const LambdaCapture &Capture : Lambda->implicit_captures()) {
  64     assert(Capture.isImplicit());
  65     if (Capture.capturesVariable() && Capture.isImplicit()) {
  66       AppendName(Capture.getCapturedVar()->getName());
  67     } else if (Capture.capturesThis()) {
  68       AppendName("this");
  69     }
  70   }
  71   if (Replacement.size() &&
  72       Lambda->explicit_capture_begin() != Lambda->explicit_capture_end()) {
  73     // Add back separator if we are adding explicit capture variables.
  74     Stream << ", ";
  75   }
  76   return Replacement;
  77 }
  78
  79 void MisleadingCaptureDefaultByValueCheck::check(
  80     const MatchFinder::MatchResult &Result) {
  81   const auto *Lambda = Result.Nodes.getNodeAs<LambdaExpr>("lambda");
  82   if (!Lambda)
  83     return;
  84
  85   if (Lambda->getCaptureDefault() == LCD_ByCopy) {
  86     bool IsThisImplicitlyCaptured = std::any_of(
  87         Lambda->implicit_capture_begin(), Lambda->implicit_capture_end(),
  88         [](const LambdaCapture &Capture) { return Capture.capturesThis(); });
  89     auto Diag = diag(Lambda->getCaptureDefaultLoc(),
  90                      "lambdas that %select{|implicitly }0capture 'this' "
  91                      "should not specify a by-value capture default")
  92                 << IsThisImplicitlyCaptured;
  93
  94     std::string ReplacementText = createReplacementText(Lambda);
  95     SourceLocation DefaultCaptureEnd =
  96         findDefaultCaptureEnd(Lambda, *Result.Context);
  97     Diag << FixItHint::CreateReplacement(
  98         CharSourceRange::getCharRange(Lambda->getCaptureDefaultLoc(),
  99                                       DefaultCaptureEnd),
 100         ReplacementText);
 101   }
 102 }
 103
 104 } // namespace clang::tidy::cppcoreguidelines