clang-tools  4.0.0
ExplicitConstructorCheck.cpp
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1 //===--- ExplicitConstructorCheck.cpp - clang-tidy ------------------------===//
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 
11 #include "clang/AST/ASTContext.h"
12 #include "clang/ASTMatchers/ASTMatchFinder.h"
13 #include "clang/ASTMatchers/ASTMatchers.h"
14 #include "clang/Lex/Lexer.h"
15 
16 using namespace clang::ast_matchers;
17 
18 namespace clang {
19 namespace tidy {
20 namespace google {
21 
22 void ExplicitConstructorCheck::registerMatchers(MatchFinder *Finder) {
23  // Only register the matchers for C++; the functionality currently does not
24  // provide any benefit to other languages, despite being benign.
25  if (!getLangOpts().CPlusPlus)
26  return;
27  Finder->addMatcher(cxxConstructorDecl(unless(isInstantiated())).bind("ctor"),
28  this);
29  Finder->addMatcher(
30  cxxConversionDecl(unless(anyOf(isExplicit(), // Already marked explicit.
31  isImplicit(), // Compiler-generated.
32  isInstantiated())))
33 
34  .bind("conversion"),
35  this);
36 }
37 
38 // Looks for the token matching the predicate and returns the range of the found
39 // token including trailing whitespace.
40 static SourceRange FindToken(const SourceManager &Sources,
41  const LangOptions &LangOpts,
42  SourceLocation StartLoc, SourceLocation EndLoc,
43  bool (*Pred)(const Token &)) {
44  if (StartLoc.isMacroID() || EndLoc.isMacroID())
45  return SourceRange();
46  FileID File = Sources.getFileID(Sources.getSpellingLoc(StartLoc));
47  StringRef Buf = Sources.getBufferData(File);
48  const char *StartChar = Sources.getCharacterData(StartLoc);
49  Lexer Lex(StartLoc, LangOpts, StartChar, StartChar, Buf.end());
50  Lex.SetCommentRetentionState(true);
51  Token Tok;
52  do {
53  Lex.LexFromRawLexer(Tok);
54  if (Pred(Tok)) {
55  Token NextTok;
56  Lex.LexFromRawLexer(NextTok);
57  return SourceRange(Tok.getLocation(), NextTok.getLocation());
58  }
59  } while (Tok.isNot(tok::eof) && Tok.getLocation() < EndLoc);
60 
61  return SourceRange();
62 }
63 
64 static bool declIsStdInitializerList(const NamedDecl *D) {
65  // First use the fast getName() method to avoid unnecessary calls to the
66  // slow getQualifiedNameAsString().
67  return D->getName() == "initializer_list" &&
68  D->getQualifiedNameAsString() == "std::initializer_list";
69 }
70 
71 static bool isStdInitializerList(QualType Type) {
72  Type = Type.getCanonicalType();
73  if (const auto *TS = Type->getAs<TemplateSpecializationType>()) {
74  if (const TemplateDecl *TD = TS->getTemplateName().getAsTemplateDecl())
75  return declIsStdInitializerList(TD);
76  }
77  if (const auto *RT = Type->getAs<RecordType>()) {
78  if (const auto *Specialization =
79  dyn_cast<ClassTemplateSpecializationDecl>(RT->getDecl()))
80  return declIsStdInitializerList(Specialization->getSpecializedTemplate());
81  }
82  return false;
83 }
84 
85 void ExplicitConstructorCheck::check(const MatchFinder::MatchResult &Result) {
86  constexpr char WarningMessage[] =
87  "%0 must be marked explicit to avoid unintentional implicit conversions";
88 
89  if (const auto *Conversion =
90  Result.Nodes.getNodeAs<CXXConversionDecl>("conversion")) {
91  SourceLocation Loc = Conversion->getLocation();
92  // Ignore all macros until we learn to ignore specific ones (e.g. used in
93  // gmock to define matchers).
94  if (Loc.isMacroID())
95  return;
96  diag(Loc, WarningMessage)
97  << Conversion << FixItHint::CreateInsertion(Loc, "explicit ");
98  return;
99  }
100 
101  const auto *Ctor = Result.Nodes.getNodeAs<CXXConstructorDecl>("ctor");
102  // Do not be confused: isExplicit means 'explicit' keyword is present,
103  // isImplicit means that it's a compiler-generated constructor.
104  if (Ctor->isOutOfLine() || Ctor->isImplicit() || Ctor->isDeleted() ||
105  Ctor->getNumParams() == 0 || Ctor->getMinRequiredArguments() > 1)
106  return;
107 
108  bool takesInitializerList = isStdInitializerList(
109  Ctor->getParamDecl(0)->getType().getNonReferenceType());
110  if (Ctor->isExplicit() &&
111  (Ctor->isCopyOrMoveConstructor() || takesInitializerList)) {
112  auto isKWExplicit = [](const Token &Tok) {
113  return Tok.is(tok::raw_identifier) &&
114  Tok.getRawIdentifier() == "explicit";
115  };
116  SourceRange ExplicitTokenRange =
117  FindToken(*Result.SourceManager, getLangOpts(),
118  Ctor->getOuterLocStart(), Ctor->getLocEnd(), isKWExplicit);
119  StringRef ConstructorDescription;
120  if (Ctor->isMoveConstructor())
121  ConstructorDescription = "move";
122  else if (Ctor->isCopyConstructor())
123  ConstructorDescription = "copy";
124  else
125  ConstructorDescription = "initializer-list";
126 
127  auto Diag = diag(Ctor->getLocation(),
128  "%0 constructor should not be declared explicit")
129  << ConstructorDescription;
130  if (ExplicitTokenRange.isValid()) {
131  Diag << FixItHint::CreateRemoval(
132  CharSourceRange::getCharRange(ExplicitTokenRange));
133  }
134  return;
135  }
136 
137  if (Ctor->isExplicit() || Ctor->isCopyOrMoveConstructor() ||
138  takesInitializerList)
139  return;
140 
141  bool SingleArgument =
142  Ctor->getNumParams() == 1 && !Ctor->getParamDecl(0)->isParameterPack();
143  SourceLocation Loc = Ctor->getLocation();
144  diag(Loc, WarningMessage)
145  << (SingleArgument
146  ? "single-argument constructors"
147  : "constructors that are callable with a single argument")
148  << FixItHint::CreateInsertion(Loc, "explicit ");
149 }
150 
151 } // namespace google
152 } // namespace tidy
153 } // namespace clang
SourceLocation Loc
'#' location in the include directive
static bool isStdInitializerList(QualType Type)
LangOptions LangOpts
Definition: ClangTidy.cpp:240
std::unique_ptr< ast_matchers::MatchFinder > Finder
Definition: ClangTidy.cpp:262
HeaderHandle File
static SourceRange FindToken(const SourceManager &Sources, const LangOptions &LangOpts, SourceLocation StartLoc, SourceLocation EndLoc, bool(*Pred)(const Token &))
static bool declIsStdInitializerList(const NamedDecl *D)
const NamedDecl * Result
Definition: USRFinder.cpp:162