1 //===--- ExplicitConstructorCheck.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 "ExplicitConstructorCheck.h"
10 #include "clang/AST/ASTContext.h"
11 #include "clang/ASTMatchers/ASTMatchFinder.h"
12 #include "clang/ASTMatchers/ASTMatchers.h"
13 #include "clang/Lex/Lexer.h"
14
15 using namespace clang::ast_matchers;
16
17 namespace clang {
18 namespace tidy {
19 namespace google {
20
registerMatchers(MatchFinder * Finder)21 void ExplicitConstructorCheck::registerMatchers(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 Finder->addMatcher(
27 cxxConstructorDecl(unless(anyOf(isImplicit(), // Compiler-generated.
28 isDeleted(), isInstantiated())))
29 .bind("ctor"),
30 this);
31 Finder->addMatcher(
32 cxxConversionDecl(unless(anyOf(isExplicit(), // Already marked explicit.
33 isImplicit(), // Compiler-generated.
34 isDeleted(), isInstantiated())))
35
36 .bind("conversion"),
37 this);
38 }
39
40 // Looks for the token matching the predicate and returns the range of the found
41 // token including trailing whitespace.
FindToken(const SourceManager & Sources,const LangOptions & LangOpts,SourceLocation StartLoc,SourceLocation EndLoc,bool (* Pred)(const Token &))42 static SourceRange FindToken(const SourceManager &Sources,
43 const LangOptions &LangOpts,
44 SourceLocation StartLoc, SourceLocation EndLoc,
45 bool (*Pred)(const Token &)) {
46 if (StartLoc.isMacroID() || EndLoc.isMacroID())
47 return SourceRange();
48 FileID File = Sources.getFileID(Sources.getSpellingLoc(StartLoc));
49 StringRef Buf = Sources.getBufferData(File);
50 const char *StartChar = Sources.getCharacterData(StartLoc);
51 Lexer Lex(StartLoc, LangOpts, StartChar, StartChar, Buf.end());
52 Lex.SetCommentRetentionState(true);
53 Token Tok;
54 do {
55 Lex.LexFromRawLexer(Tok);
56 if (Pred(Tok)) {
57 Token NextTok;
58 Lex.LexFromRawLexer(NextTok);
59 return SourceRange(Tok.getLocation(), NextTok.getLocation());
60 }
61 } while (Tok.isNot(tok::eof) && Tok.getLocation() < EndLoc);
62
63 return SourceRange();
64 }
65
declIsStdInitializerList(const NamedDecl * D)66 static bool declIsStdInitializerList(const NamedDecl *D) {
67 // First use the fast getName() method to avoid unnecessary calls to the
68 // slow getQualifiedNameAsString().
69 return D->getName() == "initializer_list" &&
70 D->getQualifiedNameAsString() == "std::initializer_list";
71 }
72
isStdInitializerList(QualType Type)73 static bool isStdInitializerList(QualType Type) {
74 Type = Type.getCanonicalType();
75 if (const auto *TS = Type->getAs<TemplateSpecializationType>()) {
76 if (const TemplateDecl *TD = TS->getTemplateName().getAsTemplateDecl())
77 return declIsStdInitializerList(TD);
78 }
79 if (const auto *RT = Type->getAs<RecordType>()) {
80 if (const auto *Specialization =
81 dyn_cast<ClassTemplateSpecializationDecl>(RT->getDecl()))
82 return declIsStdInitializerList(Specialization->getSpecializedTemplate());
83 }
84 return false;
85 }
86
check(const MatchFinder::MatchResult & Result)87 void ExplicitConstructorCheck::check(const MatchFinder::MatchResult &Result) {
88 constexpr char WarningMessage[] =
89 "%0 must be marked explicit to avoid unintentional implicit conversions";
90
91 if (const auto *Conversion =
92 Result.Nodes.getNodeAs<CXXConversionDecl>("conversion")) {
93 if (Conversion->isOutOfLine())
94 return;
95 SourceLocation Loc = Conversion->getLocation();
96 // Ignore all macros until we learn to ignore specific ones (e.g. used in
97 // gmock to define matchers).
98 if (Loc.isMacroID())
99 return;
100 diag(Loc, WarningMessage)
101 << Conversion << FixItHint::CreateInsertion(Loc, "explicit ");
102 return;
103 }
104
105 const auto *Ctor = Result.Nodes.getNodeAs<CXXConstructorDecl>("ctor");
106 if (Ctor->isOutOfLine() || Ctor->getNumParams() == 0 ||
107 Ctor->getMinRequiredArguments() > 1)
108 return;
109
110 bool takesInitializerList = isStdInitializerList(
111 Ctor->getParamDecl(0)->getType().getNonReferenceType());
112 if (Ctor->isExplicit() &&
113 (Ctor->isCopyOrMoveConstructor() || takesInitializerList)) {
114 auto isKWExplicit = [](const Token &Tok) {
115 return Tok.is(tok::raw_identifier) &&
116 Tok.getRawIdentifier() == "explicit";
117 };
118 SourceRange ExplicitTokenRange =
119 FindToken(*Result.SourceManager, getLangOpts(),
120 Ctor->getOuterLocStart(), Ctor->getEndLoc(), isKWExplicit);
121 StringRef ConstructorDescription;
122 if (Ctor->isMoveConstructor())
123 ConstructorDescription = "move";
124 else if (Ctor->isCopyConstructor())
125 ConstructorDescription = "copy";
126 else
127 ConstructorDescription = "initializer-list";
128
129 auto Diag = diag(Ctor->getLocation(),
130 "%0 constructor should not be declared explicit")
131 << ConstructorDescription;
132 if (ExplicitTokenRange.isValid()) {
133 Diag << FixItHint::CreateRemoval(
134 CharSourceRange::getCharRange(ExplicitTokenRange));
135 }
136 return;
137 }
138
139 if (Ctor->isExplicit() || Ctor->isCopyOrMoveConstructor() ||
140 takesInitializerList)
141 return;
142
143 bool SingleArgument =
144 Ctor->getNumParams() == 1 && !Ctor->getParamDecl(0)->isParameterPack();
145 SourceLocation Loc = Ctor->getLocation();
146 diag(Loc, WarningMessage)
147 << (SingleArgument
148 ? "single-argument constructors"
149 : "constructors that are callable with a single argument")
150 << FixItHint::CreateInsertion(Loc, "explicit ");
151 }
152
153 } // namespace google
154 } // namespace tidy
155 } // namespace clang
156