1 //===--- PostfixOperatorCheck.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 "PostfixOperatorCheck.h"
10 #include "clang/AST/ASTContext.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 cert {
19 
registerMatchers(MatchFinder * Finder)20 void PostfixOperatorCheck::registerMatchers(MatchFinder *Finder) {
21   Finder->addMatcher(functionDecl(hasAnyOverloadedOperatorName("++", "--"),
22                                   unless(isInstantiated()))
23                          .bind("decl"),
24                      this);
25 }
26 
check(const MatchFinder::MatchResult & Result)27 void PostfixOperatorCheck::check(const MatchFinder::MatchResult &Result) {
28   const auto *FuncDecl = Result.Nodes.getNodeAs<FunctionDecl>("decl");
29 
30   bool HasThis = false;
31   if (const auto *MethodDecl = dyn_cast<CXXMethodDecl>(FuncDecl))
32     HasThis = MethodDecl->isInstance();
33 
34   // Check if the operator is a postfix one.
35   if (FuncDecl->getNumParams() != (HasThis ? 1 : 2))
36     return;
37 
38   SourceRange ReturnRange = FuncDecl->getReturnTypeSourceRange();
39   SourceLocation Location = ReturnRange.getBegin();
40   if (!Location.isValid())
41     return;
42 
43   QualType ReturnType = FuncDecl->getReturnType();
44 
45   // Warn when the operators return a reference.
46   if (const auto *RefType = ReturnType->getAs<ReferenceType>()) {
47     auto Diag = diag(Location, "overloaded %0 returns a reference instead of a "
48                                "constant object type")
49                 << FuncDecl;
50 
51     if (Location.isMacroID() || ReturnType->getAs<TypedefType>() ||
52         RefType->getPointeeTypeAsWritten()->getAs<TypedefType>())
53       return;
54 
55     QualType ReplaceType =
56         ReturnType.getNonReferenceType().getLocalUnqualifiedType();
57     // The getReturnTypeSourceRange omits the qualifiers. We do not want to
58     // duplicate the const.
59     if (!ReturnType->getPointeeType().isConstQualified())
60       ReplaceType.addConst();
61 
62     Diag << FixItHint::CreateReplacement(
63         ReturnRange,
64         ReplaceType.getAsString(Result.Context->getPrintingPolicy()) + " ");
65 
66     return;
67   }
68 
69   if (ReturnType.isConstQualified() || ReturnType->isBuiltinType() ||
70       ReturnType->isPointerType())
71     return;
72 
73   auto Diag =
74       diag(Location, "overloaded %0 returns a non-constant object instead of a "
75                      "constant object type")
76       << FuncDecl;
77 
78   if (!Location.isMacroID() && !ReturnType->getAs<TypedefType>())
79     Diag << FixItHint::CreateInsertion(Location, "const ");
80 }
81 
82 } // namespace cert
83 } // namespace tidy
84 } // namespace clang
85