clang-tools-extra/clang-tidy/readability/RedundantSmartptrGetCheck.cpp

   1 //===--- RedundantSmartptrGetCheck.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
   9 #include "RedundantSmartptrGetCheck.h"
  10 #include "clang/ASTMatchers/ASTMatchFinder.h"
  11 #include "clang/Lex/Lexer.h"
  12
  13 using namespace clang::ast_matchers;
  14
  15 namespace clang::tidy::readability {
  16
  17 namespace {
  18 internal::Matcher<Expr> callToGet(const internal::Matcher<Decl> &OnClass) {
  19   return expr(
  20              anyOf(cxxMemberCallExpr(
  21                        on(expr(anyOf(hasType(OnClass),
  22                                      hasType(qualType(pointsTo(
  23                                          decl(OnClass).bind("ptr_to_ptr"))))))
  24                               .bind("smart_pointer")),
  25                        unless(callee(
  26                            memberExpr(hasObjectExpression(cxxThisExpr())))),
  27                        callee(cxxMethodDecl(hasName("get"),
  28                                             returns(qualType(pointsTo(
  29                                                 type().bind("getType"))))))),
  30                    cxxDependentScopeMemberExpr(
  31                        hasMemberName("get"),
  32                        hasObjectExpression(
  33                            expr(hasType(qualType(hasCanonicalType(
  34                                     templateSpecializationType(hasDeclaration(
  35                                         classTemplateDecl(has(cxxRecordDecl(
  36                                             OnClass,
  37                                             hasMethod(cxxMethodDecl(
  38                                                 hasName("get"),
  39                                                 returns(qualType(
  40                                                     pointsTo(type().bind(
  41                                                         "getType")))))))))))))))
  42                                .bind("smart_pointer")))))
  43       .bind("redundant_get");
  44 }
  45
  46 internal::Matcher<Decl> knownSmartptr() {
  47   return recordDecl(hasAnyName("::std::unique_ptr", "::std::shared_ptr"));
  48 }
  49
  50 void registerMatchersForGetArrowStart(MatchFinder *Finder,
  51                                       MatchFinder::MatchCallback *Callback) {
  52   const auto QuacksLikeASmartptr = recordDecl(
  53       recordDecl().bind("duck_typing"),
  54       has(cxxMethodDecl(hasName("operator->"),
  55                         returns(qualType(pointsTo(type().bind("op->Type")))))),
  56       has(cxxMethodDecl(hasName("operator*"), returns(qualType(references(
  57                                                   type().bind("op*Type")))))));
  58
  59   // Make sure we are not missing the known standard types.
  60   const auto Smartptr = anyOf(knownSmartptr(), QuacksLikeASmartptr);
  61
  62   // Catch 'ptr.get()->Foo()'
  63   Finder->addMatcher(memberExpr(expr().bind("memberExpr"), isArrow(),
  64                                 hasObjectExpression(callToGet(Smartptr))),
  65                      Callback);
  66
  67   // Catch '*ptr.get()' or '*ptr->get()'
  68   Finder->addMatcher(
  69       unaryOperator(hasOperatorName("*"), hasUnaryOperand(callToGet(Smartptr))),
  70       Callback);
  71
  72   // Catch '!ptr.get()'
  73   const auto CallToGetAsBool = callToGet(
  74       recordDecl(Smartptr, has(cxxConversionDecl(returns(booleanType())))));
  75   Finder->addMatcher(
  76       unaryOperator(hasOperatorName("!"), hasUnaryOperand(CallToGetAsBool)),
  77       Callback);
  78
  79   // Catch 'if(ptr.get())'
  80   Finder->addMatcher(ifStmt(hasCondition(CallToGetAsBool)), Callback);
  81
  82   // Catch 'ptr.get() ? X : Y'
  83   Finder->addMatcher(conditionalOperator(hasCondition(CallToGetAsBool)),
  84                      Callback);
  85
  86   Finder->addMatcher(cxxDependentScopeMemberExpr(hasObjectExpression(
  87                          callExpr(has(callToGet(Smartptr))).bind("obj"))),
  88                      Callback);
  89 }
  90
  91 void registerMatchersForGetEquals(MatchFinder *Finder,
  92                                   MatchFinder::MatchCallback *Callback) {
  93   // This one is harder to do with duck typing.
  94   // The operator==/!= that we are looking for might be member or non-member,
  95   // might be on global namespace or found by ADL, might be a template, etc.
  96   // For now, lets keep it to the known standard types.
  97
  98   // Matches against nullptr.
  99   Finder->addMatcher(
 100       binaryOperator(hasAnyOperatorName("==", "!="),
 101                      hasOperands(anyOf(cxxNullPtrLiteralExpr(), gnuNullExpr(),
 102                                        integerLiteral(equals(0))),
 103                                  callToGet(knownSmartptr()))),
 104       Callback);
 105
 106   // FIXME: Match and fix if (l.get() == r.get()).
 107 }
 108
 109 } // namespace
 110
 111 void RedundantSmartptrGetCheck::storeOptions(
 112     ClangTidyOptions::OptionMap &Opts) {
 113   Options.store(Opts, "IgnoreMacros", IgnoreMacros);
 114 }
 115
 116 void RedundantSmartptrGetCheck::registerMatchers(MatchFinder *Finder) {
 117   registerMatchersForGetArrowStart(Finder, this);
 118   registerMatchersForGetEquals(Finder, this);
 119 }
 120
 121 namespace {
 122 bool allReturnTypesMatch(const MatchFinder::MatchResult &Result) {
 123   if (Result.Nodes.getNodeAs<Decl>("duck_typing") == nullptr)
 124     return true;
 125   // Verify that the types match.
 126   // We can't do this on the matcher because the type nodes can be different,
 127   // even though they represent the same type. This difference comes from how
 128   // the type is referenced (eg. through a typedef, a type trait, etc).
 129   const Type *OpArrowType =
 130       Result.Nodes.getNodeAs<Type>("op->Type")->getUnqualifiedDesugaredType();
 131   const Type *OpStarType =
 132       Result.Nodes.getNodeAs<Type>("op*Type")->getUnqualifiedDesugaredType();
 133   const Type *GetType =
 134       Result.Nodes.getNodeAs<Type>("getType")->getUnqualifiedDesugaredType();
 135   return OpArrowType == OpStarType && OpArrowType == GetType;
 136 }
 137 } // namespace
 138
 139 void RedundantSmartptrGetCheck::check(const MatchFinder::MatchResult &Result) {
 140   if (!allReturnTypesMatch(Result))
 141     return;
 142
 143   bool IsPtrToPtr = Result.Nodes.getNodeAs<Decl>("ptr_to_ptr") != nullptr;
 144   bool IsMemberExpr = Result.Nodes.getNodeAs<Expr>("memberExpr") != nullptr;
 145   const auto *GetCall = Result.Nodes.getNodeAs<Expr>("redundant_get");
 146   if (GetCall->getBeginLoc().isMacroID() && IgnoreMacros)
 147     return;
 148
 149   const auto *Smartptr = Result.Nodes.getNodeAs<Expr>("smart_pointer");
 150
 151   if (IsPtrToPtr && IsMemberExpr) {
 152     // Ignore this case (eg. Foo->get()->DoSomething());
 153     return;
 154   }
 155
 156   auto SR = GetCall->getSourceRange();
 157   // CXXDependentScopeMemberExpr source range does not include parens
 158   // Extend the source range of the get call to account for them.
 159   if (isa<CXXDependentScopeMemberExpr>(GetCall))
 160     SR.setEnd(Lexer::getLocForEndOfToken(SR.getEnd(), 0, *Result.SourceManager,
 161                                          getLangOpts())
 162                   .getLocWithOffset(1));
 163
 164   StringRef SmartptrText = Lexer::getSourceText(
 165       CharSourceRange::getTokenRange(Smartptr->getSourceRange()),
 166       *Result.SourceManager, getLangOpts());
 167   // Replace foo->get() with *foo, and foo.get() with foo.
 168   std::string Replacement = Twine(IsPtrToPtr ? "*" : "", SmartptrText).str();
 169   diag(GetCall->getBeginLoc(), "redundant get() call on smart pointer")
 170       << FixItHint::CreateReplacement(SR, Replacement);
 171 }
 172
 173 } // namespace clang::tidy::readability