1 //===--- UnconventionalAssignOperatorCheck.cpp - clang-tidy -----*- C++ -*-===//
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 "UnconventionalAssignOperatorCheck.h"
11 #include "clang/ASTMatchers/ASTMatchFinder.h"
12 #include "clang/ASTMatchers/ASTMatchers.h"
13 
14 using namespace clang::ast_matchers;
15 
16 namespace clang {
17 namespace tidy {
18 namespace misc {
19 
20 void UnconventionalAssignOperatorCheck::registerMatchers(
21     ast_matchers::MatchFinder *Finder) {
22   // Only register the matchers for C++; the functionality currently does not
23   // provide any benefit to other languages, despite being benign.
24   if (!getLangOpts().CPlusPlus)
25     return;
26 
27   const auto HasGoodReturnType = cxxMethodDecl(returns(
28       lValueReferenceType(pointee(unless(isConstQualified()),
29                                   hasDeclaration(equalsBoundNode("class"))))));
30 
31   const auto IsSelf = qualType(
32       anyOf(hasDeclaration(equalsBoundNode("class")),
33             referenceType(pointee(hasDeclaration(equalsBoundNode("class"))))));
34   const auto IsAssign =
35       cxxMethodDecl(unless(anyOf(isDeleted(), isPrivate(), isImplicit())),
36                     hasName("operator="), ofClass(recordDecl().bind("class")))
37           .bind("method");
38   const auto IsSelfAssign =
39       cxxMethodDecl(IsAssign, hasParameter(0, parmVarDecl(hasType(IsSelf))))
40           .bind("method");
41 
42   Finder->addMatcher(
43       cxxMethodDecl(IsAssign, unless(HasGoodReturnType)).bind("ReturnType"),
44       this);
45 
46   const auto BadSelf = referenceType(
47       anyOf(lValueReferenceType(pointee(unless(isConstQualified()))),
48             rValueReferenceType(pointee(isConstQualified()))));
49 
50   Finder->addMatcher(
51       cxxMethodDecl(IsSelfAssign,
52                     hasParameter(0, parmVarDecl(hasType(BadSelf))))
53           .bind("ArgumentType"),
54       this);
55 
56   Finder->addMatcher(
57       cxxMethodDecl(IsSelfAssign, anyOf(isConst(), isVirtual())).bind("cv"),
58       this);
59 
60   const auto IsBadReturnStatement = returnStmt(unless(has(ignoringParenImpCasts(
61       anyOf(unaryOperator(hasOperatorName("*"), hasUnaryOperand(cxxThisExpr())),
62             cxxOperatorCallExpr(argumentCountIs(1),
63                                 callee(unresolvedLookupExpr()),
64                                 hasArgument(0, cxxThisExpr())))))));
65   const auto IsGoodAssign = cxxMethodDecl(IsAssign, HasGoodReturnType);
66 
67   Finder->addMatcher(returnStmt(IsBadReturnStatement, forFunction(IsGoodAssign))
68                          .bind("returnStmt"),
69                      this);
70 }
71 
72 void UnconventionalAssignOperatorCheck::check(
73     const MatchFinder::MatchResult &Result) {
74   if (const auto *RetStmt = Result.Nodes.getNodeAs<ReturnStmt>("returnStmt")) {
75     diag(RetStmt->getLocStart(), "operator=() should always return '*this'");
76   } else {
77     static const char *const Messages[][2] = {
78         {"ReturnType", "operator=() should return '%0&'"},
79         {"ArgumentType", "operator=() should take '%0 const&', '%0&&' or '%0'"},
80         {"cv", "operator=() should not be marked '%1'"}};
81 
82     const auto *Method = Result.Nodes.getNodeAs<CXXMethodDecl>("method");
83     for (const auto &Message : Messages) {
84       if (Result.Nodes.getNodeAs<Decl>(Message[0]))
85         diag(Method->getLocStart(), Message[1])
86             << Method->getParent()->getName()
87             << (Method->isConst() ? "const" : "virtual");
88     }
89   }
90 }
91 
92 } // namespace misc
93 } // namespace tidy
94 } // namespace clang
95