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 
MisleadingCaptureDefaultByValueCheck(StringRef Name,ClangTidyContext * Context)21 MisleadingCaptureDefaultByValueCheck::MisleadingCaptureDefaultByValueCheck(
22     StringRef Name, ClangTidyContext *Context)
23     : ClangTidyCheck(Name, Context) {}
24 
registerMatchers(MatchFinder * Finder)25 void MisleadingCaptureDefaultByValueCheck::registerMatchers(
26     MatchFinder *Finder) {
27   Finder->addMatcher(lambdaExpr(hasAnyCapture(capturesThis())).bind("lambda"),
28                      this);
29 }
30 
findDefaultCaptureEnd(const LambdaExpr * Lambda,ASTContext & Context)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       }
41       return Capture.getLocation();
42     }
43   }
44   return Lambda->getIntroducerRange().getEnd();
45 }
46 
createReplacementText(const LambdaExpr * Lambda)47 static std::string createReplacementText(const LambdaExpr *Lambda) {
48   std::string Replacement;
49   llvm::raw_string_ostream Stream(Replacement);
50 
51   auto AppendName = [&](llvm::StringRef Name) {
52     if (!Replacement.empty()) {
53       Stream << ", ";
54     }
55     if (Lambda->getCaptureDefault() == LCD_ByRef && Name != "this") {
56       Stream << "&" << Name;
57     } else {
58       Stream << Name;
59     }
60   };
61 
62   for (const LambdaCapture &Capture : Lambda->implicit_captures()) {
63     assert(Capture.isImplicit());
64     if (Capture.capturesVariable() && Capture.isImplicit()) {
65       AppendName(Capture.getCapturedVar()->getName());
66     } else if (Capture.capturesThis()) {
67       AppendName("this");
68     }
69   }
70   if (!Replacement.empty() && !Lambda->explicit_captures().empty()) {
71     // Add back separator if we are adding explicit capture variables.
72     Stream << ", ";
73   }
74   return Replacement;
75 }
76 
check(const MatchFinder::MatchResult & Result)77 void MisleadingCaptureDefaultByValueCheck::check(
78     const MatchFinder::MatchResult &Result) {
79   const auto *Lambda = Result.Nodes.getNodeAs<LambdaExpr>("lambda");
80   if (!Lambda)
81     return;
82 
83   if (Lambda->getCaptureDefault() == LCD_ByCopy) {
84     bool IsThisImplicitlyCaptured = std::any_of(
85         Lambda->implicit_capture_begin(), Lambda->implicit_capture_end(),
86         [](const LambdaCapture &Capture) { return Capture.capturesThis(); });
87     auto Diag = diag(Lambda->getCaptureDefaultLoc(),
88                      "lambdas that %select{|implicitly }0capture 'this' "
89                      "should not specify a by-value capture default")
90                 << IsThisImplicitlyCaptured;
91 
92     std::string ReplacementText = createReplacementText(Lambda);
93     SourceLocation DefaultCaptureEnd =
94         findDefaultCaptureEnd(Lambda, *Result.Context);
95     Diag << FixItHint::CreateReplacement(
96         CharSourceRange::getCharRange(Lambda->getCaptureDefaultLoc(),
97                                       DefaultCaptureEnd),
98         ReplacementText);
99   }
100 }
101 
102 } // namespace clang::tidy::cppcoreguidelines
103