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1 //===--- ExplicitConstructorCheck.cpp - clang-tidy ------------------------===//
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2 //
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3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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4 // See https://llvm.org/LICENSE.txt for license information.
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5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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6 //
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7 //===----------------------------------------------------------------------===//
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8
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9 #include "ExplicitConstructorCheck.h"
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10 #include "clang/AST/ASTContext.h"
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11 #include "clang/ASTMatchers/ASTMatchFinder.h"
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12 #include "clang/ASTMatchers/ASTMatchers.h"
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13 #include "clang/Lex/Lexer.h"
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14
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15 using namespace clang::ast_matchers;
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16
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17 namespace clang {
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18 namespace tidy {
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19 namespace google {
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20
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21 void ExplicitConstructorCheck::registerMatchers(MatchFinder *Finder) {
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22 // Only register the matchers for C++; the functionality currently does not
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23 // provide any benefit to other languages, despite being benign.
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24 if (!getLangOpts().CPlusPlus)
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25 return;
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26 Finder->addMatcher(
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27 cxxConstructorDecl(unless(anyOf(isImplicit(), // Compiler-generated.
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28 isDeleted(), isInstantiated())))
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29 .bind("ctor"),
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30 this);
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31 Finder->addMatcher(
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32 cxxConversionDecl(unless(anyOf(isExplicit(), // Already marked explicit.
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33 isImplicit(), // Compiler-generated.
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34 isDeleted(), isInstantiated())))
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35
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36 .bind("conversion"),
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37 this);
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38 }
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39
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40 // Looks for the token matching the predicate and returns the range of the found
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41 // token including trailing whitespace.
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42 static SourceRange FindToken(const SourceManager &Sources,
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43 const LangOptions &LangOpts,
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44 SourceLocation StartLoc, SourceLocation EndLoc,
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45 bool (*Pred)(const Token &)) {
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46 if (StartLoc.isMacroID() || EndLoc.isMacroID())
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47 return SourceRange();
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48 FileID File = Sources.getFileID(Sources.getSpellingLoc(StartLoc));
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49 StringRef Buf = Sources.getBufferData(File);
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50 const char *StartChar = Sources.getCharacterData(StartLoc);
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51 Lexer Lex(StartLoc, LangOpts, StartChar, StartChar, Buf.end());
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52 Lex.SetCommentRetentionState(true);
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53 Token Tok;
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54 do {
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55 Lex.LexFromRawLexer(Tok);
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56 if (Pred(Tok)) {
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57 Token NextTok;
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58 Lex.LexFromRawLexer(NextTok);
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59 return SourceRange(Tok.getLocation(), NextTok.getLocation());
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60 }
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61 } while (Tok.isNot(tok::eof) && Tok.getLocation() < EndLoc);
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62
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63 return SourceRange();
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64 }
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65
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66 static bool declIsStdInitializerList(const NamedDecl *D) {
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67 // First use the fast getName() method to avoid unnecessary calls to the
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68 // slow getQualifiedNameAsString().
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69 return D->getName() == "initializer_list" &&
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70 D->getQualifiedNameAsString() == "std::initializer_list";
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71 }
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72
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73 static bool isStdInitializerList(QualType Type) {
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74 Type = Type.getCanonicalType();
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75 if (const auto *TS = Type->getAs<TemplateSpecializationType>()) {
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76 if (const TemplateDecl *TD = TS->getTemplateName().getAsTemplateDecl())
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77 return declIsStdInitializerList(TD);
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78 }
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79 if (const auto *RT = Type->getAs<RecordType>()) {
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80 if (const auto *Specialization =
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81 dyn_cast<ClassTemplateSpecializationDecl>(RT->getDecl()))
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82 return declIsStdInitializerList(Specialization->getSpecializedTemplate());
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83 }
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84 return false;
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85 }
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86
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87 void ExplicitConstructorCheck::check(const MatchFinder::MatchResult &Result) {
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88 constexpr char WarningMessage[] =
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89 "%0 must be marked explicit to avoid unintentional implicit conversions";
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90
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91 if (const auto *Conversion =
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92 Result.Nodes.getNodeAs<CXXConversionDecl>("conversion")) {
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93 if (Conversion->isOutOfLine())
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94 return;
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95 SourceLocation Loc = Conversion->getLocation();
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96 // Ignore all macros until we learn to ignore specific ones (e.g. used in
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97 // gmock to define matchers).
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98 if (Loc.isMacroID())
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99 return;
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100 diag(Loc, WarningMessage)
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101 << Conversion << FixItHint::CreateInsertion(Loc, "explicit ");
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102 return;
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103 }
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104
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105 const auto *Ctor = Result.Nodes.getNodeAs<CXXConstructorDecl>("ctor");
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106 if (Ctor->isOutOfLine() || Ctor->getNumParams() == 0 ||
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107 Ctor->getMinRequiredArguments() > 1)
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108 return;
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109
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110 bool takesInitializerList = isStdInitializerList(
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111 Ctor->getParamDecl(0)->getType().getNonReferenceType());
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112 if (Ctor->isExplicit() &&
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113 (Ctor->isCopyOrMoveConstructor() || takesInitializerList)) {
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114 auto isKWExplicit = [](const Token &Tok) {
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115 return Tok.is(tok::raw_identifier) &&
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116 Tok.getRawIdentifier() == "explicit";
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117 };
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118 SourceRange ExplicitTokenRange =
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119 FindToken(*Result.SourceManager, getLangOpts(),
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120 Ctor->getOuterLocStart(), Ctor->getEndLoc(), isKWExplicit);
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121 StringRef ConstructorDescription;
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122 if (Ctor->isMoveConstructor())
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123 ConstructorDescription = "move";
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124 else if (Ctor->isCopyConstructor())
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125 ConstructorDescription = "copy";
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126 else
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127 ConstructorDescription = "initializer-list";
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128
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129 auto Diag = diag(Ctor->getLocation(),
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130 "%0 constructor should not be declared explicit")
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131 << ConstructorDescription;
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132 if (ExplicitTokenRange.isValid()) {
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133 Diag << FixItHint::CreateRemoval(
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134 CharSourceRange::getCharRange(ExplicitTokenRange));
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135 }
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136 return;
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137 }
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138
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139 if (Ctor->isExplicit() || Ctor->isCopyOrMoveConstructor() ||
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140 takesInitializerList)
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141 return;
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142
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143 bool SingleArgument =
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144 Ctor->getNumParams() == 1 && !Ctor->getParamDecl(0)->isParameterPack();
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145 SourceLocation Loc = Ctor->getLocation();
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146 diag(Loc, WarningMessage)
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147 << (SingleArgument
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148 ? "single-argument constructors"
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149 : "constructors that are callable with a single argument")
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150 << FixItHint::CreateInsertion(Loc, "explicit ");
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151 }
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152
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153 } // namespace google
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154 } // namespace tidy
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155 } // namespace clang
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