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 
10 #include "RedundantSmartptrGetCheck.h"
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(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 
56 void registerMatchersForGetEquals(MatchFinder *Finder,
57                                   MatchFinder::MatchCallback *Callback) {
58   // This one is harder to do with duck typing.
59   // The operator==/!= that we are looking for might be member or non-member,
60   // might be on global namespace or found by ADL, might be a template, etc.
61   // For now, lets keep a list of known standard types.
62 
63   const auto IsAKnownSmartptr = recordDecl(
64       anyOf(hasName("::std::unique_ptr"), hasName("::std::shared_ptr")));
65 
66   // Matches against nullptr.
67   Finder->addMatcher(
68       binaryOperator(
69           anyOf(hasOperatorName("=="), hasOperatorName("!=")),
70           hasEitherOperand(ignoringImpCasts(cxxNullPtrLiteralExpr())),
71           hasEitherOperand(callToGet(IsAKnownSmartptr))),
72       Callback);
73   // TODO: Catch ptr.get() == other_ptr.get()
74 }
75 
76 
77 }  // namespace
78 
79 void RedundantSmartptrGetCheck::registerMatchers(MatchFinder *Finder) {
80   // Only register the matchers for C++; the functionality currently does not
81   // provide any benefit to other languages, despite being benign.
82   if (!getLangOpts().CPlusPlus)
83     return;
84 
85   registerMatchersForGetArrowStart(Finder, this);
86   registerMatchersForGetEquals(Finder, this);
87 }
88 
89 namespace {
90 bool allReturnTypesMatch(const MatchFinder::MatchResult &Result) {
91   if (Result.Nodes.getNodeAs<Decl>("duck_typing") == nullptr)
92     return true;
93   // Verify that the types match.
94   // We can't do this on the matcher because the type nodes can be different,
95   // even though they represent the same type. This difference comes from how
96   // the type is referenced (eg. through a typedef, a type trait, etc).
97   const Type *OpArrowType =
98       Result.Nodes.getNodeAs<Type>("op->Type")->getUnqualifiedDesugaredType();
99   const Type *OpStarType =
100       Result.Nodes.getNodeAs<Type>("op*Type")->getUnqualifiedDesugaredType();
101   const Type *GetType =
102       Result.Nodes.getNodeAs<Type>("getType")->getUnqualifiedDesugaredType();
103   return OpArrowType == OpStarType && OpArrowType == GetType;
104 }
105 }  // namespace
106 
107 void RedundantSmartptrGetCheck::check(const MatchFinder::MatchResult &Result) {
108   if (!allReturnTypesMatch(Result)) return;
109 
110   bool IsPtrToPtr = Result.Nodes.getNodeAs<Decl>("ptr_to_ptr") != nullptr;
111   bool IsMemberExpr = Result.Nodes.getNodeAs<Expr>("memberExpr") != nullptr;
112   const Expr *GetCall = Result.Nodes.getNodeAs<Expr>("redundant_get");
113   const Expr *Smartptr = Result.Nodes.getNodeAs<Expr>("smart_pointer");
114 
115   if (IsPtrToPtr && IsMemberExpr) {
116     // Ignore this case (eg. Foo->get()->DoSomething());
117     return;
118   }
119 
120   StringRef SmartptrText = Lexer::getSourceText(
121       CharSourceRange::getTokenRange(Smartptr->getSourceRange()),
122       *Result.SourceManager, Result.Context->getLangOpts());
123   // Replace foo->get() with *foo, and foo.get() with foo.
124   std::string Replacement = Twine(IsPtrToPtr ? "*" : "", SmartptrText).str();
125   diag(GetCall->getLocStart(), "redundant get() call on smart pointer")
126       << FixItHint::CreateReplacement(GetCall->getSourceRange(), Replacement);
127 }
128 
129 } // namespace readability
130 } // namespace tidy
131 } // namespace clang
132