clang-tools  10.0.0
MoveForwardingReferenceCheck.cpp
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1 //===--- MoveForwardingReferenceCheck.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 
10 #include "clang/Lex/Lexer.h"
11 #include "llvm/Support/raw_ostream.h"
12 
13 #include <algorithm>
14 
15 using namespace clang::ast_matchers;
16 
17 namespace clang {
18 namespace tidy {
19 namespace bugprone {
20 
21 static void replaceMoveWithForward(const UnresolvedLookupExpr *Callee,
22  const ParmVarDecl *ParmVar,
23  const TemplateTypeParmDecl *TypeParmDecl,
24  DiagnosticBuilder &Diag,
25  const ASTContext &Context) {
26  const SourceManager &SM = Context.getSourceManager();
27  const LangOptions &LangOpts = Context.getLangOpts();
28 
29  CharSourceRange CallRange =
30  Lexer::makeFileCharRange(CharSourceRange::getTokenRange(
31  Callee->getBeginLoc(), Callee->getEndLoc()),
32  SM, LangOpts);
33 
34  if (CallRange.isValid()) {
35  const std::string TypeName =
36  (TypeParmDecl->getIdentifier() && !TypeParmDecl->isImplicit())
37  ? TypeParmDecl->getName().str()
38  : (llvm::Twine("decltype(") + ParmVar->getName() + ")").str();
39 
40  const std::string ForwardName =
41  (llvm::Twine("forward<") + TypeName + ">").str();
42 
43  // Create a replacement only if we see a "standard" way of calling
44  // std::move(). This will hopefully prevent erroneous replacements if the
45  // code does unusual things (e.g. create an alias for std::move() in
46  // another namespace).
47  NestedNameSpecifier *NNS = Callee->getQualifier();
48  if (!NNS) {
49  // Called as "move" (i.e. presumably the code had a "using std::move;").
50  // We still conservatively put a "std::" in front of the forward because
51  // we don't know whether the code also had a "using std::forward;".
52  Diag << FixItHint::CreateReplacement(CallRange, "std::" + ForwardName);
53  } else if (const NamespaceDecl *Namespace = NNS->getAsNamespace()) {
54  if (Namespace->getName() == "std") {
55  if (!NNS->getPrefix()) {
56  // Called as "std::move".
57  Diag << FixItHint::CreateReplacement(CallRange,
58  "std::" + ForwardName);
59  } else if (NNS->getPrefix()->getKind() == NestedNameSpecifier::Global) {
60  // Called as "::std::move".
61  Diag << FixItHint::CreateReplacement(CallRange,
62  "::std::" + ForwardName);
63  }
64  }
65  }
66  }
67 }
68 
69 void MoveForwardingReferenceCheck::registerMatchers(MatchFinder *Finder) {
70  if (!getLangOpts().CPlusPlus11)
71  return;
72 
73  // Matches a ParmVarDecl for a forwarding reference, i.e. a non-const rvalue
74  // reference of a function template parameter type.
75  auto ForwardingReferenceParmMatcher =
76  parmVarDecl(
77  hasType(qualType(rValueReferenceType(),
78  references(templateTypeParmType(hasDeclaration(
79  templateTypeParmDecl().bind("type-parm-decl")))),
80  unless(references(qualType(isConstQualified()))))))
81  .bind("parm-var");
82 
83  Finder->addMatcher(
84  callExpr(callee(unresolvedLookupExpr(
85  hasAnyDeclaration(namedDecl(
86  hasUnderlyingDecl(hasName("::std::move")))))
87  .bind("lookup")),
88  argumentCountIs(1),
89  hasArgument(0, ignoringParenImpCasts(declRefExpr(
90  to(ForwardingReferenceParmMatcher)))))
91  .bind("call-move"),
92  this);
93 }
94 
95 void MoveForwardingReferenceCheck::check(
96  const MatchFinder::MatchResult &Result) {
97  const auto *CallMove = Result.Nodes.getNodeAs<CallExpr>("call-move");
98  const auto *UnresolvedLookup =
99  Result.Nodes.getNodeAs<UnresolvedLookupExpr>("lookup");
100  const auto *ParmVar = Result.Nodes.getNodeAs<ParmVarDecl>("parm-var");
101  const auto *TypeParmDecl =
102  Result.Nodes.getNodeAs<TemplateTypeParmDecl>("type-parm-decl");
103 
104  // Get the FunctionDecl and FunctionTemplateDecl containing the function
105  // parameter.
106  const auto *FuncForParam = dyn_cast<FunctionDecl>(ParmVar->getDeclContext());
107  if (!FuncForParam)
108  return;
109  const FunctionTemplateDecl *FuncTemplate =
110  FuncForParam->getDescribedFunctionTemplate();
111  if (!FuncTemplate)
112  return;
113 
114  // Check that the template type parameter belongs to the same function
115  // template as the function parameter of that type. (This implies that type
116  // deduction will happen on the type.)
117  const TemplateParameterList *Params = FuncTemplate->getTemplateParameters();
118  if (!std::count(Params->begin(), Params->end(), TypeParmDecl))
119  return;
120 
121  auto Diag = diag(CallMove->getExprLoc(),
122  "forwarding reference passed to std::move(), which may "
123  "unexpectedly cause lvalues to be moved; use "
124  "std::forward() instead");
125 
126  replaceMoveWithForward(UnresolvedLookup, ParmVar, TypeParmDecl, Diag,
127  *Result.Context);
128 }
129 
130 } // namespace bugprone
131 } // namespace tidy
132 } // namespace clang
llvm::Optional< Range > getTokenRange(const SourceManager &SM, const LangOptions &LangOpts, SourceLocation TokLoc)
Returns the taken range at TokLoc.
Definition: SourceCode.cpp:227
static void replaceMoveWithForward(const UnresolvedLookupExpr *Callee, const ParmVarDecl *ParmVar, const TemplateTypeParmDecl *TypeParmDecl, DiagnosticBuilder &Diag, const ASTContext &Context)
===– Representation.cpp - ClangDoc Representation --------—*- C++ -*-===//