clang-tools  4.0.0
UnusedUsingDeclsCheck.cpp
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1 //===--- UnusedUsingDeclsCheck.cpp - clang-tidy----------------------------===//
2 //
3 // The LLVM Compiler Infrastructure
4 //
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
7 //
8 //===----------------------------------------------------------------------===//
9 
10 #include "UnusedUsingDeclsCheck.h"
11 #include "clang/AST/ASTContext.h"
12 #include "clang/ASTMatchers/ASTMatchFinder.h"
13 #include "clang/Lex/Lexer.h"
14 
15 using namespace clang::ast_matchers;
16 
17 namespace clang {
18 namespace tidy {
19 namespace misc {
20 
21 // A function that helps to tell whether a TargetDecl in a UsingDecl will be
22 // checked. Only variable, function, function template, class template, class,
23 // enum declaration and enum constant declaration are considered.
24 static bool ShouldCheckDecl(const Decl *TargetDecl) {
25  return isa<RecordDecl>(TargetDecl) || isa<ClassTemplateDecl>(TargetDecl) ||
26  isa<FunctionDecl>(TargetDecl) || isa<VarDecl>(TargetDecl) ||
27  isa<FunctionTemplateDecl>(TargetDecl) || isa<EnumDecl>(TargetDecl) ||
28  isa<EnumConstantDecl>(TargetDecl);
29 }
30 
31 void UnusedUsingDeclsCheck::registerMatchers(MatchFinder *Finder) {
32  Finder->addMatcher(usingDecl(isExpansionInMainFile()).bind("using"), this);
33  auto DeclMatcher = hasDeclaration(namedDecl().bind("used"));
34  Finder->addMatcher(loc(enumType(DeclMatcher)), this);
35  Finder->addMatcher(loc(recordType(DeclMatcher)), this);
36  Finder->addMatcher(loc(templateSpecializationType(DeclMatcher)), this);
37  Finder->addMatcher(declRefExpr().bind("used"), this);
38  Finder->addMatcher(callExpr(callee(unresolvedLookupExpr().bind("used"))),
39  this);
40  Finder->addMatcher(
41  callExpr(hasDeclaration(functionDecl(hasAnyTemplateArgument(
42  anyOf(refersToTemplate(templateName().bind("used")),
43  refersToDeclaration(functionDecl().bind("used"))))))),
44  this);
45  Finder->addMatcher(loc(templateSpecializationType(hasAnyTemplateArgument(
46  templateArgument().bind("used")))),
47  this);
48 }
49 
50 void UnusedUsingDeclsCheck::check(const MatchFinder::MatchResult &Result) {
51  if (const auto *Using = Result.Nodes.getNodeAs<UsingDecl>("using")) {
52  // Ignores using-declarations defined in macros.
53  if (Using->getLocation().isMacroID())
54  return;
55 
56  // Ignores using-declarations defined in class definition.
57  if (isa<CXXRecordDecl>(Using->getDeclContext()))
58  return;
59 
60  // FIXME: We ignore using-decls defined in function definitions at the
61  // moment because of false positives caused by ADL and different function
62  // scopes.
63  if (isa<FunctionDecl>(Using->getDeclContext()))
64  return;
65 
66  UsingDeclContext Context(Using);
67  Context.UsingDeclRange = CharSourceRange::getCharRange(
68  Using->getLocStart(),
69  Lexer::findLocationAfterToken(
70  Using->getLocEnd(), tok::semi, *Result.SourceManager, getLangOpts(),
71  /*SkipTrailingWhitespaceAndNewLine=*/true));
72  for (const auto *UsingShadow : Using->shadows()) {
73  const auto *TargetDecl = UsingShadow->getTargetDecl()->getCanonicalDecl();
74  if (ShouldCheckDecl(TargetDecl))
75  Context.UsingTargetDecls.insert(TargetDecl);
76  }
77  if (!Context.UsingTargetDecls.empty())
78  Contexts.push_back(Context);
79  return;
80  }
81  // Mark using declarations as used by setting FoundDecls' value to zero. As
82  // the AST is walked in order, usages are only marked after a the
83  // corresponding using declaration has been found.
84  // FIXME: This currently doesn't look at whether the type reference is
85  // actually found with the help of the using declaration.
86  if (const auto *Used = Result.Nodes.getNodeAs<NamedDecl>("used")) {
87  if (const auto *FD = dyn_cast<FunctionDecl>(Used)) {
88  removeFromFoundDecls(FD->getPrimaryTemplate());
89  } else if (const auto *Specialization =
90  dyn_cast<ClassTemplateSpecializationDecl>(Used)) {
91  Used = Specialization->getSpecializedTemplate();
92  }
93  removeFromFoundDecls(Used);
94  return;
95  }
96 
97  if (const auto *Used = Result.Nodes.getNodeAs<TemplateArgument>("used")) {
98  // FIXME: Support non-type template parameters.
99  if (Used->getKind() == TemplateArgument::Template) {
100  if (const auto *TD = Used->getAsTemplate().getAsTemplateDecl())
101  removeFromFoundDecls(TD);
102  } else if (Used->getKind() == TemplateArgument::Type) {
103  if (auto *RD = Used->getAsType()->getAsCXXRecordDecl())
104  removeFromFoundDecls(RD);
105  }
106  return;
107  }
108 
109  if (const auto *Used = Result.Nodes.getNodeAs<TemplateName>("used")) {
110  removeFromFoundDecls(Used->getAsTemplateDecl());
111  return;
112  }
113 
114  if (const auto *DRE = Result.Nodes.getNodeAs<DeclRefExpr>("used")) {
115  if (const auto *FD = dyn_cast<FunctionDecl>(DRE->getDecl())) {
116  if (const auto *FDT = FD->getPrimaryTemplate())
117  removeFromFoundDecls(FDT);
118  else
119  removeFromFoundDecls(FD);
120  } else if (const auto *VD = dyn_cast<VarDecl>(DRE->getDecl())) {
121  removeFromFoundDecls(VD);
122  } else if (const auto *ECD = dyn_cast<EnumConstantDecl>(DRE->getDecl())) {
123  removeFromFoundDecls(ECD);
124  if (const auto *ET = ECD->getType()->getAs<EnumType>())
125  removeFromFoundDecls(ET->getDecl());
126  }
127  }
128  // Check the uninstantiated template function usage.
129  if (const auto *ULE = Result.Nodes.getNodeAs<UnresolvedLookupExpr>("used")) {
130  for (const NamedDecl *ND : ULE->decls()) {
131  if (const auto *USD = dyn_cast<UsingShadowDecl>(ND))
132  removeFromFoundDecls(USD->getTargetDecl()->getCanonicalDecl());
133  }
134  }
135 }
136 
137 void UnusedUsingDeclsCheck::removeFromFoundDecls(const Decl *D) {
138  if (!D)
139  return;
140  // FIXME: Currently, we don't handle the using-decls being used in different
141  // scopes (such as different namespaces, different functions). Instead of
142  // giving an incorrect message, we mark all of them as used.
143  //
144  // FIXME: Use a more efficient way to find a matching context.
145  for (auto &Context : Contexts) {
146  if (Context.UsingTargetDecls.count(D->getCanonicalDecl()) > 0)
147  Context.IsUsed = true;
148  }
149 }
150 
151 void UnusedUsingDeclsCheck::onEndOfTranslationUnit() {
152  for (const auto &Context : Contexts) {
153  if (!Context.IsUsed) {
154  diag(Context.FoundUsingDecl->getLocation(), "using decl %0 is unused")
155  << Context.FoundUsingDecl
156  << FixItHint::CreateRemoval(Context.UsingDeclRange);
157  }
158  }
159  Contexts.clear();
160 }
161 
162 } // namespace misc
163 } // namespace tidy
164 } // namespace clang
std::unique_ptr< ast_matchers::MatchFinder > Finder
Definition: ClangTidy.cpp:262
static bool ShouldCheckDecl(const Decl *TargetDecl)
ClangTidyContext & Context
Definition: ClangTidy.cpp:87
const NamedDecl * Result
Definition: USRFinder.cpp:162