clang-tools  7.0.0
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 (Result.Context->getDiagnostics().hasUncompilableErrorOccurred())
52  return;
53 
54  if (const auto *Using = Result.Nodes.getNodeAs<UsingDecl>("using")) {
55  // Ignores using-declarations defined in macros.
56  if (Using->getLocation().isMacroID())
57  return;
58 
59  // Ignores using-declarations defined in class definition.
60  if (isa<CXXRecordDecl>(Using->getDeclContext()))
61  return;
62 
63  // FIXME: We ignore using-decls defined in function definitions at the
64  // moment because of false positives caused by ADL and different function
65  // scopes.
66  if (isa<FunctionDecl>(Using->getDeclContext()))
67  return;
68 
69  UsingDeclContext Context(Using);
70  Context.UsingDeclRange = CharSourceRange::getCharRange(
71  Using->getLocStart(),
72  Lexer::findLocationAfterToken(
73  Using->getLocEnd(), tok::semi, *Result.SourceManager, getLangOpts(),
74  /*SkipTrailingWhitespaceAndNewLine=*/true));
75  for (const auto *UsingShadow : Using->shadows()) {
76  const auto *TargetDecl = UsingShadow->getTargetDecl()->getCanonicalDecl();
77  if (ShouldCheckDecl(TargetDecl))
78  Context.UsingTargetDecls.insert(TargetDecl);
79  }
80  if (!Context.UsingTargetDecls.empty())
81  Contexts.push_back(Context);
82  return;
83  }
84  // Mark using declarations as used by setting FoundDecls' value to zero. As
85  // the AST is walked in order, usages are only marked after a the
86  // corresponding using declaration has been found.
87  // FIXME: This currently doesn't look at whether the type reference is
88  // actually found with the help of the using declaration.
89  if (const auto *Used = Result.Nodes.getNodeAs<NamedDecl>("used")) {
90  if (const auto *FD = dyn_cast<FunctionDecl>(Used)) {
91  removeFromFoundDecls(FD->getPrimaryTemplate());
92  } else if (const auto *Specialization =
93  dyn_cast<ClassTemplateSpecializationDecl>(Used)) {
94  Used = Specialization->getSpecializedTemplate();
95  }
96  removeFromFoundDecls(Used);
97  return;
98  }
99 
100  if (const auto *Used = Result.Nodes.getNodeAs<TemplateArgument>("used")) {
101  // FIXME: Support non-type template parameters.
102  if (Used->getKind() == TemplateArgument::Template) {
103  if (const auto *TD = Used->getAsTemplate().getAsTemplateDecl())
104  removeFromFoundDecls(TD);
105  } else if (Used->getKind() == TemplateArgument::Type) {
106  if (auto *RD = Used->getAsType()->getAsCXXRecordDecl())
107  removeFromFoundDecls(RD);
108  }
109  return;
110  }
111 
112  if (const auto *Used = Result.Nodes.getNodeAs<TemplateName>("used")) {
113  removeFromFoundDecls(Used->getAsTemplateDecl());
114  return;
115  }
116 
117  if (const auto *DRE = Result.Nodes.getNodeAs<DeclRefExpr>("used")) {
118  if (const auto *FD = dyn_cast<FunctionDecl>(DRE->getDecl())) {
119  if (const auto *FDT = FD->getPrimaryTemplate())
120  removeFromFoundDecls(FDT);
121  else
122  removeFromFoundDecls(FD);
123  } else if (const auto *VD = dyn_cast<VarDecl>(DRE->getDecl())) {
124  removeFromFoundDecls(VD);
125  } else if (const auto *ECD = dyn_cast<EnumConstantDecl>(DRE->getDecl())) {
126  removeFromFoundDecls(ECD);
127  if (const auto *ET = ECD->getType()->getAs<EnumType>())
128  removeFromFoundDecls(ET->getDecl());
129  }
130  }
131  // Check the uninstantiated template function usage.
132  if (const auto *ULE = Result.Nodes.getNodeAs<UnresolvedLookupExpr>("used")) {
133  for (const NamedDecl *ND : ULE->decls()) {
134  if (const auto *USD = dyn_cast<UsingShadowDecl>(ND))
135  removeFromFoundDecls(USD->getTargetDecl()->getCanonicalDecl());
136  }
137  }
138 }
139 
140 void UnusedUsingDeclsCheck::removeFromFoundDecls(const Decl *D) {
141  if (!D)
142  return;
143  // FIXME: Currently, we don't handle the using-decls being used in different
144  // scopes (such as different namespaces, different functions). Instead of
145  // giving an incorrect message, we mark all of them as used.
146  //
147  // FIXME: Use a more efficient way to find a matching context.
148  for (auto &Context : Contexts) {
149  if (Context.UsingTargetDecls.count(D->getCanonicalDecl()) > 0)
150  Context.IsUsed = true;
151  }
152 }
153 
154 void UnusedUsingDeclsCheck::onEndOfTranslationUnit() {
155  for (const auto &Context : Contexts) {
156  if (!Context.IsUsed) {
157  diag(Context.FoundUsingDecl->getLocation(), "using decl %0 is unused")
158  << Context.FoundUsingDecl
159  << FixItHint::CreateRemoval(Context.UsingDeclRange);
160  }
161  }
162  Contexts.clear();
163 }
164 
165 } // namespace misc
166 } // namespace tidy
167 } // namespace clang
static bool ShouldCheckDecl(const Decl *TargetDecl)
===– Representation.cpp - ClangDoc Representation --------—*- C++ -*-===//