clang-tools  9.0.0
ForwardingReferenceOverloadCheck.cpp
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1 //===--- ForwardingReferenceOverloadCheck.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/AST/ASTContext.h"
11 #include "clang/ASTMatchers/ASTMatchFinder.h"
12 #include <algorithm>
13 
14 using namespace clang::ast_matchers;
15 
16 namespace clang {
17 namespace tidy {
18 namespace bugprone {
19 
20 namespace {
21 // Check if the given type is related to std::enable_if.
22 AST_MATCHER(QualType, isEnableIf) {
23  auto CheckTemplate = [](const TemplateSpecializationType *Spec) {
24  if (!Spec || !Spec->getTemplateName().getAsTemplateDecl()) {
25  return false;
26  }
27  const NamedDecl *TypeDecl =
28  Spec->getTemplateName().getAsTemplateDecl()->getTemplatedDecl();
29  return TypeDecl->isInStdNamespace() &&
30  (TypeDecl->getName().equals("enable_if") ||
31  TypeDecl->getName().equals("enable_if_t"));
32  };
33  const Type *BaseType = Node.getTypePtr();
34  // Case: pointer or reference to enable_if.
35  while (BaseType->isPointerType() || BaseType->isReferenceType()) {
36  BaseType = BaseType->getPointeeType().getTypePtr();
37  }
38  // Case: type parameter dependent (enable_if<is_integral<T>>).
39  if (const auto *Dependent = BaseType->getAs<DependentNameType>()) {
40  BaseType = Dependent->getQualifier()->getAsType();
41  }
42  if (!BaseType)
43  return false;
44  if (CheckTemplate(BaseType->getAs<TemplateSpecializationType>())) {
45  return true; // Case: enable_if_t< >.
46  } else if (const auto *Elaborated = BaseType->getAs<ElaboratedType>()) {
47  if (const auto *Qualifier = Elaborated->getQualifier()->getAsType()) {
48  if (CheckTemplate(Qualifier->getAs<TemplateSpecializationType>())) {
49  return true; // Case: enable_if< >::type.
50  }
51  }
52  }
53  return false;
54 }
55 AST_MATCHER_P(TemplateTypeParmDecl, hasDefaultArgument,
56  clang::ast_matchers::internal::Matcher<QualType>, TypeMatcher) {
57  return Node.hasDefaultArgument() &&
58  TypeMatcher.matches(Node.getDefaultArgument(), Finder, Builder);
59 }
60 } // namespace
61 
62 void ForwardingReferenceOverloadCheck::registerMatchers(MatchFinder *Finder) {
63  // Forwarding references require C++11 or later.
64  if (!getLangOpts().CPlusPlus11)
65  return;
66 
67  auto ForwardingRefParm =
68  parmVarDecl(
69  hasType(qualType(rValueReferenceType(),
70  references(templateTypeParmType(hasDeclaration(
71  templateTypeParmDecl().bind("type-parm-decl")))),
72  unless(references(isConstQualified())))))
73  .bind("parm-var");
74 
75  DeclarationMatcher findOverload =
76  cxxConstructorDecl(
77  hasParameter(0, ForwardingRefParm),
78  unless(hasAnyParameter(
79  // No warning: enable_if as constructor parameter.
80  parmVarDecl(hasType(isEnableIf())))),
81  unless(hasParent(functionTemplateDecl(has(templateTypeParmDecl(
82  // No warning: enable_if as type parameter.
83  hasDefaultArgument(isEnableIf())))))))
84  .bind("ctor");
85  Finder->addMatcher(findOverload, this);
86 }
87 
88 void ForwardingReferenceOverloadCheck::check(
89  const MatchFinder::MatchResult &Result) {
90  const auto *ParmVar = Result.Nodes.getNodeAs<ParmVarDecl>("parm-var");
91  const auto *TypeParmDecl =
92  Result.Nodes.getNodeAs<TemplateTypeParmDecl>("type-parm-decl");
93 
94  // Get the FunctionDecl and FunctionTemplateDecl containing the function
95  // parameter.
96  const auto *FuncForParam = dyn_cast<FunctionDecl>(ParmVar->getDeclContext());
97  if (!FuncForParam)
98  return;
99  const FunctionTemplateDecl *FuncTemplate =
100  FuncForParam->getDescribedFunctionTemplate();
101  if (!FuncTemplate)
102  return;
103 
104  // Check that the template type parameter belongs to the same function
105  // template as the function parameter of that type. (This implies that type
106  // deduction will happen on the type.)
107  const TemplateParameterList *Params = FuncTemplate->getTemplateParameters();
108  if (!llvm::is_contained(*Params, TypeParmDecl))
109  return;
110 
111  // Every parameter after the first must have a default value.
112  const auto *Ctor = Result.Nodes.getNodeAs<CXXConstructorDecl>("ctor");
113  for (auto Iter = Ctor->param_begin() + 1; Iter != Ctor->param_end(); ++Iter) {
114  if (!(*Iter)->hasDefaultArg())
115  return;
116  }
117  bool EnabledCopy = false, DisabledCopy = false, EnabledMove = false,
118  DisabledMove = false;
119  for (const auto *OtherCtor : Ctor->getParent()->ctors()) {
120  if (OtherCtor->isCopyOrMoveConstructor()) {
121  if (OtherCtor->isDeleted() || OtherCtor->getAccess() == AS_private)
122  (OtherCtor->isCopyConstructor() ? DisabledCopy : DisabledMove) = true;
123  else
124  (OtherCtor->isCopyConstructor() ? EnabledCopy : EnabledMove) = true;
125  }
126  }
127  bool Copy = (!EnabledMove && !DisabledMove && !DisabledCopy) || EnabledCopy;
128  bool Move = !DisabledMove || EnabledMove;
129  if (!Copy && !Move)
130  return;
131  diag(Ctor->getLocation(),
132  "constructor accepting a forwarding reference can "
133  "hide the %select{copy|move|copy and move}0 constructor%s1")
134  << (Copy && Move ? 2 : (Copy ? 0 : 1)) << Copy + Move;
135  for (const auto *OtherCtor : Ctor->getParent()->ctors()) {
136  if (OtherCtor->isCopyOrMoveConstructor() && !OtherCtor->isDeleted() &&
137  OtherCtor->getAccess() != AS_private) {
138  diag(OtherCtor->getLocation(),
139  "%select{copy|move}0 constructor declared here", DiagnosticIDs::Note)
140  << OtherCtor->isMoveConstructor();
141  }
142  }
143 }
144 
145 } // namespace bugprone
146 } // namespace tidy
147 } // namespace clang
CodeCompletionBuilder Builder
===– Representation.cpp - ClangDoc Representation --------—*- C++ -*-===//
llvm::Optional< llvm::Expected< tooling::AtomicChanges > > Result
Definition: Rename.cpp:36
NodeType Type
AST_MATCHER_P(CXXMethodDecl, hasCanonicalDecl, ast_matchers::internal::Matcher< CXXMethodDecl >, InnerMatcher)