1 //===--- UnconventionalAssignOperatorCheck.cpp - clang-tidy -----*- C++ -*-===//
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 "UnconventionalAssignOperatorCheck.h"
10 #include "clang/ASTMatchers/ASTMatchFinder.h"
11 #include "clang/ASTMatchers/ASTMatchers.h"
12 
13 using namespace clang::ast_matchers;
14 
15 namespace clang {
16 namespace tidy {
17 namespace misc {
18 
19 void UnconventionalAssignOperatorCheck::registerMatchers(
20     ast_matchers::MatchFinder *Finder) {
21   // Only register the matchers for C++; the functionality currently does not
22   // provide any benefit to other languages, despite being benign.
23   if (!getLangOpts().CPlusPlus)
24     return;
25 
26   const auto HasGoodReturnType = cxxMethodDecl(returns(lValueReferenceType(
27       pointee(unless(isConstQualified()),
28               anyOf(autoType(), hasDeclaration(equalsBoundNode("class")))))));
29 
30   const auto IsSelf = qualType(
31       anyOf(hasDeclaration(equalsBoundNode("class")),
32             referenceType(pointee(hasDeclaration(equalsBoundNode("class"))))));
33   const auto IsAssign =
34       cxxMethodDecl(unless(anyOf(isDeleted(), isPrivate(), isImplicit())),
35                     hasName("operator="), ofClass(recordDecl().bind("class")))
36           .bind("method");
37   const auto IsSelfAssign =
38       cxxMethodDecl(IsAssign, hasParameter(0, parmVarDecl(hasType(IsSelf))))
39           .bind("method");
40 
41   Finder->addMatcher(
42       cxxMethodDecl(IsAssign, unless(HasGoodReturnType)).bind("ReturnType"),
43       this);
44 
45   const auto BadSelf = referenceType(
46       anyOf(lValueReferenceType(pointee(unless(isConstQualified()))),
47             rValueReferenceType(pointee(isConstQualified()))));
48 
49   Finder->addMatcher(
50       cxxMethodDecl(IsSelfAssign,
51                     hasParameter(0, parmVarDecl(hasType(BadSelf))))
52           .bind("ArgumentType"),
53       this);
54 
55   Finder->addMatcher(
56       cxxMethodDecl(IsSelfAssign, anyOf(isConst(), isVirtual())).bind("cv"),
57       this);
58 
59   const auto IsBadReturnStatement = returnStmt(unless(has(ignoringParenImpCasts(
60       anyOf(unaryOperator(hasOperatorName("*"), hasUnaryOperand(cxxThisExpr())),
61             cxxOperatorCallExpr(argumentCountIs(1),
62                                 callee(unresolvedLookupExpr()),
63                                 hasArgument(0, cxxThisExpr())))))));
64   const auto IsGoodAssign = cxxMethodDecl(IsAssign, HasGoodReturnType);
65 
66   Finder->addMatcher(returnStmt(IsBadReturnStatement, forFunction(IsGoodAssign))
67                          .bind("returnStmt"),
68                      this);
69 }
70 
71 void UnconventionalAssignOperatorCheck::check(
72     const MatchFinder::MatchResult &Result) {
73   if (const auto *RetStmt = Result.Nodes.getNodeAs<ReturnStmt>("returnStmt")) {
74     diag(RetStmt->getBeginLoc(), "operator=() should always return '*this'");
75   } else {
76     static const char *const Messages[][2] = {
77         {"ReturnType", "operator=() should return '%0&'"},
78         {"ArgumentType", "operator=() should take '%0 const&', '%0&&' or '%0'"},
79         {"cv", "operator=() should not be marked '%1'"}};
80 
81     const auto *Method = Result.Nodes.getNodeAs<CXXMethodDecl>("method");
82     for (const auto &Message : Messages) {
83       if (Result.Nodes.getNodeAs<Decl>(Message[0]))
84         diag(Method->getBeginLoc(), Message[1])
85             << Method->getParent()->getName()
86             << (Method->isConst() ? "const" : "virtual");
87     }
88   }
89 }
90 
91 } // namespace misc
92 } // namespace tidy
93 } // namespace clang
94