1 //===--- UseTransparentFunctorsCheck.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 "UseTransparentFunctorsCheck.h"
10 #include "clang/AST/ASTContext.h"
11 #include "clang/ASTMatchers/ASTMatchFinder.h"
12 
13 using namespace clang::ast_matchers;
14 
15 namespace clang {
16 namespace tidy {
17 namespace modernize {
18 
19 UseTransparentFunctorsCheck::UseTransparentFunctorsCheck(
20     StringRef Name, ClangTidyContext *Context)
21     : ClangTidyCheck(Name, Context), SafeMode(Options.get("SafeMode", false)) {}
22 
23 void UseTransparentFunctorsCheck::storeOptions(
24     ClangTidyOptions::OptionMap &Opts) {
25   Options.store(Opts, "SafeMode", SafeMode);
26 }
27 
28 void UseTransparentFunctorsCheck::registerMatchers(MatchFinder *Finder) {
29   const auto TransparentFunctors =
30       classTemplateSpecializationDecl(
31           unless(hasAnyTemplateArgument(refersToType(voidType()))),
32           hasAnyName("::std::plus", "::std::minus", "::std::multiplies",
33                      "::std::divides", "::std::modulus", "::std::negate",
34                      "::std::equal_to", "::std::not_equal_to", "::std::greater",
35                      "::std::less", "::std::greater_equal", "::std::less_equal",
36                      "::std::logical_and", "::std::logical_or",
37                      "::std::logical_not", "::std::bit_and", "::std::bit_or",
38                      "::std::bit_xor", "::std::bit_not"))
39           .bind("FunctorClass");
40 
41   // Non-transparent functor mentioned as a template parameter. FIXIT.
42   Finder->addMatcher(
43       loc(qualType(
44               unless(elaboratedType()),
45               hasDeclaration(classTemplateSpecializationDecl(
46                   unless(hasAnyTemplateArgument(templateArgument(refersToType(
47                       qualType(pointsTo(qualType(isAnyCharacter()))))))),
48                   hasAnyTemplateArgument(
49                       templateArgument(refersToType(qualType(hasDeclaration(
50                                            TransparentFunctors))))
51                           .bind("Functor"))))))
52           .bind("FunctorParentLoc"),
53       this);
54 
55   if (SafeMode)
56     return;
57 
58   // Non-transparent functor constructed. No FIXIT. There is no easy way
59   // to rule out the problematic char* vs string case.
60   Finder->addMatcher(cxxConstructExpr(hasDeclaration(cxxMethodDecl(
61                                           ofClass(TransparentFunctors))),
62                                       unless(isInTemplateInstantiation()))
63                          .bind("FuncInst"),
64                      this);
65 }
66 
67 static const StringRef Message = "prefer transparent functors '%0<>'";
68 
69 template <typename T> static T getInnerTypeLocAs(TypeLoc Loc) {
70   T Result;
71   while (Result.isNull() && !Loc.isNull()) {
72     Result = Loc.getAs<T>();
73     Loc = Loc.getNextTypeLoc();
74   }
75   return Result;
76 }
77 
78 void UseTransparentFunctorsCheck::check(
79     const MatchFinder::MatchResult &Result) {
80   const auto *FuncClass =
81       Result.Nodes.getNodeAs<ClassTemplateSpecializationDecl>("FunctorClass");
82   if (const auto *FuncInst =
83           Result.Nodes.getNodeAs<CXXConstructExpr>("FuncInst")) {
84     diag(FuncInst->getBeginLoc(), Message) << FuncClass->getName();
85     return;
86   }
87 
88   const auto *Functor = Result.Nodes.getNodeAs<TemplateArgument>("Functor");
89   const auto FunctorParentLoc =
90       Result.Nodes.getNodeAs<TypeLoc>("FunctorParentLoc")
91           ->getAs<TemplateSpecializationTypeLoc>();
92 
93   if (!FunctorParentLoc)
94     return;
95 
96   unsigned ArgNum = 0;
97   const auto *FunctorParentType =
98       FunctorParentLoc.getType()->castAs<TemplateSpecializationType>();
99   for (; ArgNum < FunctorParentType->getNumArgs(); ++ArgNum) {
100     const TemplateArgument &Arg = FunctorParentType->getArg(ArgNum);
101     if (Arg.getKind() != TemplateArgument::Type)
102       continue;
103     QualType ParentArgType = Arg.getAsType();
104     if (ParentArgType->isRecordType() &&
105         ParentArgType->getAsCXXRecordDecl() ==
106             Functor->getAsType()->getAsCXXRecordDecl())
107       break;
108   }
109   // Functor is a default template argument.
110   if (ArgNum == FunctorParentType->getNumArgs())
111     return;
112   TemplateArgumentLoc FunctorLoc = FunctorParentLoc.getArgLoc(ArgNum);
113   auto FunctorTypeLoc = getInnerTypeLocAs<TemplateSpecializationTypeLoc>(
114       FunctorLoc.getTypeSourceInfo()->getTypeLoc());
115   if (FunctorTypeLoc.isNull())
116     return;
117 
118   SourceLocation ReportLoc = FunctorLoc.getLocation();
119   if (ReportLoc.isInvalid())
120     return;
121   diag(ReportLoc, Message) << FuncClass->getName()
122                            << FixItHint::CreateRemoval(
123                                   FunctorTypeLoc.getArgLoc(0).getSourceRange());
124 }
125 
126 } // namespace modernize
127 } // namespace tidy
128 } // namespace clang
129