clang-tools  7.0.0
RedundantSmartptrGetCheck.cpp
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1 //===--- RedundantSmartptrGetCheck.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 
11 #include "clang/ASTMatchers/ASTMatchFinder.h"
12 #include "clang/Lex/Lexer.h"
13 
14 using namespace clang::ast_matchers;
15 
16 namespace clang {
17 namespace tidy {
18 namespace readability {
19 
20 namespace {
21 internal::Matcher<Expr> callToGet(const internal::Matcher<Decl> &OnClass) {
22  return cxxMemberCallExpr(
23  on(expr(anyOf(hasType(OnClass),
24  hasType(qualType(
25  pointsTo(decl(OnClass).bind("ptr_to_ptr"))))))
26  .bind("smart_pointer")),
27  unless(callee(memberExpr(hasObjectExpression(cxxThisExpr())))),
28  callee(cxxMethodDecl(
29  hasName("get"),
30  returns(qualType(pointsTo(type().bind("getType")))))))
31  .bind("redundant_get");
32 }
33 
34 void registerMatchersForGetArrowStart(MatchFinder *Finder,
35  MatchFinder::MatchCallback *Callback) {
36  const auto QuacksLikeASmartptr = recordDecl(
37  recordDecl().bind("duck_typing"),
38  has(cxxMethodDecl(hasName("operator->"),
39  returns(qualType(pointsTo(type().bind("op->Type")))))),
40  has(cxxMethodDecl(hasName("operator*"), returns(qualType(references(
41  type().bind("op*Type")))))));
42 
43  // Catch 'ptr.get()->Foo()'
44  Finder->addMatcher(memberExpr(expr().bind("memberExpr"), isArrow(),
45  hasObjectExpression(ignoringImpCasts(
46  callToGet(QuacksLikeASmartptr)))),
47  Callback);
48 
49  // Catch '*ptr.get()' or '*ptr->get()'
50  Finder->addMatcher(
51  unaryOperator(hasOperatorName("*"),
52  hasUnaryOperand(callToGet(QuacksLikeASmartptr))),
53  Callback);
54 
55  // Catch '!ptr.get()'
56  const auto CallToGetAsBool = ignoringParenImpCasts(callToGet(recordDecl(
57  QuacksLikeASmartptr, has(cxxConversionDecl(returns(booleanType()))))));
58  Finder->addMatcher(
59  unaryOperator(hasOperatorName("!"), hasUnaryOperand(CallToGetAsBool)),
60  Callback);
61 
62  // Catch 'if(ptr.get())'
63  Finder->addMatcher(ifStmt(hasCondition(CallToGetAsBool)), Callback);
64 
65  // Catch 'ptr.get() ? X : Y'
66  Finder->addMatcher(conditionalOperator(hasCondition(CallToGetAsBool)),
67  Callback);
68 }
69 
70 void registerMatchersForGetEquals(MatchFinder *Finder,
71  MatchFinder::MatchCallback *Callback) {
72  // This one is harder to do with duck typing.
73  // The operator==/!= that we are looking for might be member or non-member,
74  // might be on global namespace or found by ADL, might be a template, etc.
75  // For now, lets keep a list of known standard types.
76 
77  const auto IsAKnownSmartptr =
78  recordDecl(hasAnyName("::std::unique_ptr", "::std::shared_ptr"));
79 
80  // Matches against nullptr.
81  Finder->addMatcher(
82  binaryOperator(anyOf(hasOperatorName("=="), hasOperatorName("!=")),
83  hasEitherOperand(ignoringImpCasts(
84  anyOf(cxxNullPtrLiteralExpr(), gnuNullExpr(),
85  integerLiteral(equals(0))))),
86  hasEitherOperand(callToGet(IsAKnownSmartptr))),
87  Callback);
88 
89  // FIXME: Match and fix if (l.get() == r.get()).
90 }
91 
92 } // namespace
93 
94 void RedundantSmartptrGetCheck::registerMatchers(MatchFinder *Finder) {
95  // Only register the matchers for C++; the functionality currently does not
96  // provide any benefit to other languages, despite being benign.
97  if (!getLangOpts().CPlusPlus)
98  return;
99 
100  registerMatchersForGetArrowStart(Finder, this);
101  registerMatchersForGetEquals(Finder, this);
102 }
103 
104 namespace {
105 bool allReturnTypesMatch(const MatchFinder::MatchResult &Result) {
106  if (Result.Nodes.getNodeAs<Decl>("duck_typing") == nullptr)
107  return true;
108  // Verify that the types match.
109  // We can't do this on the matcher because the type nodes can be different,
110  // even though they represent the same type. This difference comes from how
111  // the type is referenced (eg. through a typedef, a type trait, etc).
112  const Type *OpArrowType =
113  Result.Nodes.getNodeAs<Type>("op->Type")->getUnqualifiedDesugaredType();
114  const Type *OpStarType =
115  Result.Nodes.getNodeAs<Type>("op*Type")->getUnqualifiedDesugaredType();
116  const Type *GetType =
117  Result.Nodes.getNodeAs<Type>("getType")->getUnqualifiedDesugaredType();
118  return OpArrowType == OpStarType && OpArrowType == GetType;
119 }
120 } // namespace
121 
122 void RedundantSmartptrGetCheck::check(const MatchFinder::MatchResult &Result) {
123  if (!allReturnTypesMatch(Result))
124  return;
125 
126  bool IsPtrToPtr = Result.Nodes.getNodeAs<Decl>("ptr_to_ptr") != nullptr;
127  bool IsMemberExpr = Result.Nodes.getNodeAs<Expr>("memberExpr") != nullptr;
128  const auto *GetCall = Result.Nodes.getNodeAs<Expr>("redundant_get");
129  const auto *Smartptr = Result.Nodes.getNodeAs<Expr>("smart_pointer");
130 
131  if (IsPtrToPtr && IsMemberExpr) {
132  // Ignore this case (eg. Foo->get()->DoSomething());
133  return;
134  }
135 
136  StringRef SmartptrText = Lexer::getSourceText(
137  CharSourceRange::getTokenRange(Smartptr->getSourceRange()),
138  *Result.SourceManager, getLangOpts());
139  // Replace foo->get() with *foo, and foo.get() with foo.
140  std::string Replacement = Twine(IsPtrToPtr ? "*" : "", SmartptrText).str();
141  diag(GetCall->getLocStart(), "redundant get() call on smart pointer")
142  << FixItHint::CreateReplacement(GetCall->getSourceRange(), Replacement);
143 }
144 
145 } // namespace readability
146 } // namespace tidy
147 } // namespace clang
llvm::unique_function< void(llvm::Expected< T >)> Callback
A Callback<T> is a void function that accepts Expected<T>.
Definition: Function.h:28
===– Representation.cpp - ClangDoc Representation --------—*- C++ -*-===//