clang-tools  10.0.0
UseAutoCheck.cpp
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1 //===--- UseAutoCheck.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 "UseAutoCheck.h"
10 #include "clang/AST/ASTContext.h"
11 #include "clang/ASTMatchers/ASTMatchFinder.h"
12 #include "clang/ASTMatchers/ASTMatchers.h"
13 #include "clang/Basic/CharInfo.h"
14 #include "clang/Tooling/FixIt.h"
15 
16 using namespace clang;
17 using namespace clang::ast_matchers;
18 using namespace clang::ast_matchers::internal;
19 
20 namespace clang {
21 namespace tidy {
22 namespace modernize {
23 namespace {
24 
25 const char IteratorDeclStmtId[] = "iterator_decl";
26 const char DeclWithNewId[] = "decl_new";
27 const char DeclWithCastId[] = "decl_cast";
28 const char DeclWithTemplateCastId[] = "decl_template";
29 
30 size_t GetTypeNameLength(bool RemoveStars, StringRef Text) {
31  enum CharType { Space, Alpha, Punctuation };
32  CharType LastChar = Space, BeforeSpace = Punctuation;
33  size_t NumChars = 0;
34  int TemplateTypenameCntr = 0;
35  for (const unsigned char C : Text) {
36  if (C == '<')
37  ++TemplateTypenameCntr;
38  else if (C == '>')
39  --TemplateTypenameCntr;
40  const CharType NextChar =
41  isAlphanumeric(C)
42  ? Alpha
43  : (isWhitespace(C) ||
44  (!RemoveStars && TemplateTypenameCntr == 0 && C == '*'))
45  ? Space
46  : Punctuation;
47  if (NextChar != Space) {
48  ++NumChars; // Count the non-space character.
49  if (LastChar == Space && NextChar == Alpha && BeforeSpace == Alpha)
50  ++NumChars; // Count a single space character between two words.
51  BeforeSpace = NextChar;
52  }
53  LastChar = NextChar;
54  }
55  return NumChars;
56 }
57 
58 /// Matches variable declarations that have explicit initializers that
59 /// are not initializer lists.
60 ///
61 /// Given
62 /// \code
63 /// iterator I = Container.begin();
64 /// MyType A(42);
65 /// MyType B{2};
66 /// MyType C;
67 /// \endcode
68 ///
69 /// varDecl(hasWrittenNonListInitializer()) maches \c I and \c A but not \c B
70 /// or \c C.
71 AST_MATCHER(VarDecl, hasWrittenNonListInitializer) {
72  const Expr *Init = Node.getAnyInitializer();
73  if (!Init)
74  return false;
75 
76  Init = Init->IgnoreImplicit();
77 
78  // The following test is based on DeclPrinter::VisitVarDecl() to find if an
79  // initializer is implicit or not.
80  if (const auto *Construct = dyn_cast<CXXConstructExpr>(Init)) {
81  return !Construct->isListInitialization() && Construct->getNumArgs() > 0 &&
82  !Construct->getArg(0)->isDefaultArgument();
83  }
84  return Node.getInitStyle() != VarDecl::ListInit;
85 }
86 
87 /// Matches QualTypes that are type sugar for QualTypes that match \c
88 /// SugarMatcher.
89 ///
90 /// Given
91 /// \code
92 /// class C {};
93 /// typedef C my_type;
94 /// typedef my_type my_other_type;
95 /// \endcode
96 ///
97 /// qualType(isSugarFor(recordType(hasDeclaration(namedDecl(hasName("C"))))))
98 /// matches \c my_type and \c my_other_type.
99 AST_MATCHER_P(QualType, isSugarFor, Matcher<QualType>, SugarMatcher) {
100  QualType QT = Node;
101  while (true) {
102  if (SugarMatcher.matches(QT, Finder, Builder))
103  return true;
104 
105  QualType NewQT = QT.getSingleStepDesugaredType(Finder->getASTContext());
106  if (NewQT == QT)
107  return false;
108  QT = NewQT;
109  }
110 }
111 
112 /// Matches named declarations that have one of the standard iterator
113 /// names: iterator, reverse_iterator, const_iterator, const_reverse_iterator.
114 ///
115 /// Given
116 /// \code
117 /// iterator I;
118 /// const_iterator CI;
119 /// \endcode
120 ///
121 /// namedDecl(hasStdIteratorName()) matches \c I and \c CI.
122 AST_MATCHER(NamedDecl, hasStdIteratorName) {
123  static const char *const IteratorNames[] = {"iterator", "reverse_iterator",
124  "const_iterator",
125  "const_reverse_iterator"};
126 
127  for (const char *Name : IteratorNames) {
128  if (hasName(Name).matches(Node, Finder, Builder))
129  return true;
130  }
131  return false;
132 }
133 
134 /// Matches named declarations that have one of the standard container
135 /// names.
136 ///
137 /// Given
138 /// \code
139 /// class vector {};
140 /// class forward_list {};
141 /// class my_ver{};
142 /// \endcode
143 ///
144 /// recordDecl(hasStdContainerName()) matches \c vector and \c forward_list
145 /// but not \c my_vec.
146 AST_MATCHER(NamedDecl, hasStdContainerName) {
147  static const char *const ContainerNames[] = {
148  "array", "deque",
149  "forward_list", "list",
150  "vector",
151 
152  "map", "multimap",
153  "set", "multiset",
154 
155  "unordered_map", "unordered_multimap",
156  "unordered_set", "unordered_multiset",
157 
158  "queue", "priority_queue",
159  "stack"};
160 
161  for (const char *Name : ContainerNames) {
162  if (hasName(Name).matches(Node, Finder, Builder))
163  return true;
164  }
165  return false;
166 }
167 
168 /// Matches declarations whose declaration context is the C++ standard library
169 /// namespace std.
170 ///
171 /// Note that inline namespaces are silently ignored during the lookup since
172 /// both libstdc++ and libc++ are known to use them for versioning purposes.
173 ///
174 /// Given:
175 /// \code
176 /// namespace ns {
177 /// struct my_type {};
178 /// using namespace std;
179 /// }
180 ///
181 /// using std::vector;
182 /// using ns:my_type;
183 /// using ns::list;
184 /// \code
185 ///
186 /// usingDecl(hasAnyUsingShadowDecl(hasTargetDecl(isFromStdNamespace())))
187 /// matches "using std::vector" and "using ns::list".
188 AST_MATCHER(Decl, isFromStdNamespace) {
189  const DeclContext *D = Node.getDeclContext();
190 
191  while (D->isInlineNamespace())
192  D = D->getParent();
193 
194  if (!D->isNamespace() || !D->getParent()->isTranslationUnit())
195  return false;
196 
197  const IdentifierInfo *Info = cast<NamespaceDecl>(D)->getIdentifier();
198 
199  return (Info && Info->isStr("std"));
200 }
201 
202 /// Matches declaration reference or member expressions with explicit template
203 /// arguments.
204 AST_POLYMORPHIC_MATCHER(hasExplicitTemplateArgs,
205  AST_POLYMORPHIC_SUPPORTED_TYPES(DeclRefExpr,
206  MemberExpr)) {
207  return Node.hasExplicitTemplateArgs();
208 }
209 
210 /// Returns a DeclarationMatcher that matches standard iterators nested
211 /// inside records with a standard container name.
212 DeclarationMatcher standardIterator() {
213  return decl(
214  namedDecl(hasStdIteratorName()),
215  hasDeclContext(recordDecl(hasStdContainerName(), isFromStdNamespace())));
216 }
217 
218 /// Returns a TypeMatcher that matches typedefs for standard iterators
219 /// inside records with a standard container name.
220 TypeMatcher typedefIterator() {
221  return typedefType(hasDeclaration(standardIterator()));
222 }
223 
224 /// Returns a TypeMatcher that matches records named for standard
225 /// iterators nested inside records named for standard containers.
226 TypeMatcher nestedIterator() {
227  return recordType(hasDeclaration(standardIterator()));
228 }
229 
230 /// Returns a TypeMatcher that matches types declared with using
231 /// declarations and which name standard iterators for standard containers.
232 TypeMatcher iteratorFromUsingDeclaration() {
233  auto HasIteratorDecl = hasDeclaration(namedDecl(hasStdIteratorName()));
234  // Types resulting from using declarations are represented by elaboratedType.
235  return elaboratedType(
236  // Unwrap the nested name specifier to test for one of the standard
237  // containers.
238  hasQualifier(specifiesType(templateSpecializationType(hasDeclaration(
239  namedDecl(hasStdContainerName(), isFromStdNamespace()))))),
240  // the named type is what comes after the final '::' in the type. It
241  // should name one of the standard iterator names.
242  namesType(
243  anyOf(typedefType(HasIteratorDecl), recordType(HasIteratorDecl))));
244 }
245 
246 /// This matcher returns declaration statements that contain variable
247 /// declarations with written non-list initializer for standard iterators.
248 StatementMatcher makeIteratorDeclMatcher() {
249  return declStmt(unless(has(
250  varDecl(anyOf(unless(hasWrittenNonListInitializer()),
251  unless(hasType(isSugarFor(anyOf(
252  typedefIterator(), nestedIterator(),
253  iteratorFromUsingDeclaration())))))))))
254  .bind(IteratorDeclStmtId);
255 }
256 
257 StatementMatcher makeDeclWithNewMatcher() {
258  return declStmt(
259  unless(has(varDecl(anyOf(
260  unless(hasInitializer(ignoringParenImpCasts(cxxNewExpr()))),
261  // FIXME: TypeLoc information is not reliable where CV
262  // qualifiers are concerned so these types can't be
263  // handled for now.
264  hasType(pointerType(
265  pointee(hasCanonicalType(hasLocalQualifiers())))),
266 
267  // FIXME: Handle function pointers. For now we ignore them
268  // because the replacement replaces the entire type
269  // specifier source range which includes the identifier.
270  hasType(pointsTo(
271  pointsTo(parenType(innerType(functionType()))))))))))
272  .bind(DeclWithNewId);
273 }
274 
275 StatementMatcher makeDeclWithCastMatcher() {
276  return declStmt(
277  unless(has(varDecl(unless(hasInitializer(explicitCastExpr()))))))
278  .bind(DeclWithCastId);
279 }
280 
281 StatementMatcher makeDeclWithTemplateCastMatcher() {
282  auto ST =
283  substTemplateTypeParmType(hasReplacementType(equalsBoundNode("arg")));
284 
285  auto ExplicitCall =
286  anyOf(has(memberExpr(hasExplicitTemplateArgs())),
287  has(ignoringImpCasts(declRefExpr(hasExplicitTemplateArgs()))));
288 
289  auto TemplateArg =
290  hasTemplateArgument(0, refersToType(qualType().bind("arg")));
291 
292  auto TemplateCall = callExpr(
293  ExplicitCall,
294  callee(functionDecl(TemplateArg,
295  returns(anyOf(ST, pointsTo(ST), references(ST))))));
296 
297  return declStmt(unless(has(varDecl(
298  unless(hasInitializer(ignoringImplicit(TemplateCall)))))))
299  .bind(DeclWithTemplateCastId);
300 }
301 
302 StatementMatcher makeCombinedMatcher() {
303  return declStmt(
304  // At least one varDecl should be a child of the declStmt to ensure
305  // it's a declaration list and avoid matching other declarations,
306  // e.g. using directives.
307  has(varDecl(unless(isImplicit()))),
308  // Skip declarations that are already using auto.
309  unless(has(varDecl(anyOf(hasType(autoType()),
310  hasType(qualType(hasDescendant(autoType()))))))),
311  anyOf(makeIteratorDeclMatcher(), makeDeclWithNewMatcher(),
312  makeDeclWithCastMatcher(), makeDeclWithTemplateCastMatcher()));
313 }
314 
315 } // namespace
316 
317 UseAutoCheck::UseAutoCheck(StringRef Name, ClangTidyContext *Context)
318  : ClangTidyCheck(Name, Context),
319  MinTypeNameLength(Options.get("MinTypeNameLength", 5)),
320  RemoveStars(Options.get("RemoveStars", 0)) {}
321 
322 void UseAutoCheck::storeOptions(ClangTidyOptions::OptionMap &Opts) {
323  Options.store(Opts, "MinTypeNameLength", MinTypeNameLength);
324  Options.store(Opts, "RemoveStars", RemoveStars ? 1 : 0);
325 }
326 
327 void UseAutoCheck::registerMatchers(MatchFinder *Finder) {
328  // Only register the matchers for C++; the functionality currently does not
329  // provide any benefit to other languages, despite being benign.
330  if (getLangOpts().CPlusPlus) {
331  Finder->addMatcher(makeCombinedMatcher(), this);
332  }
333 }
334 
335 void UseAutoCheck::replaceIterators(const DeclStmt *D, ASTContext *Context) {
336  for (const auto *Dec : D->decls()) {
337  const auto *V = cast<VarDecl>(Dec);
338  const Expr *ExprInit = V->getInit();
339 
340  // Skip expressions with cleanups from the intializer expression.
341  if (const auto *E = dyn_cast<ExprWithCleanups>(ExprInit))
342  ExprInit = E->getSubExpr();
343 
344  const auto *Construct = dyn_cast<CXXConstructExpr>(ExprInit);
345  if (!Construct)
346  continue;
347 
348  // Ensure that the constructor receives a single argument.
349  if (Construct->getNumArgs() != 1)
350  return;
351 
352  // Drill down to the as-written initializer.
353  const Expr *E = (*Construct->arg_begin())->IgnoreParenImpCasts();
354  if (E != E->IgnoreConversionOperator()) {
355  // We hit a conversion operator. Early-out now as they imply an implicit
356  // conversion from a different type. Could also mean an explicit
357  // conversion from the same type but that's pretty rare.
358  return;
359  }
360 
361  if (const auto *NestedConstruct = dyn_cast<CXXConstructExpr>(E)) {
362  // If we ran into an implicit conversion constructor, can't convert.
363  //
364  // FIXME: The following only checks if the constructor can be used
365  // implicitly, not if it actually was. Cases where the converting
366  // constructor was used explicitly won't get converted.
367  if (NestedConstruct->getConstructor()->isConvertingConstructor(false))
368  return;
369  }
370  if (!Context->hasSameType(V->getType(), E->getType()))
371  return;
372  }
373 
374  // Get the type location using the first declaration.
375  const auto *V = cast<VarDecl>(*D->decl_begin());
376 
377  // WARNING: TypeLoc::getSourceRange() will include the identifier for things
378  // like function pointers. Not a concern since this action only works with
379  // iterators but something to keep in mind in the future.
380 
381  SourceRange Range(V->getTypeSourceInfo()->getTypeLoc().getSourceRange());
382  diag(Range.getBegin(), "use auto when declaring iterators")
383  << FixItHint::CreateReplacement(Range, "auto");
384 }
385 
386 void UseAutoCheck::replaceExpr(
387  const DeclStmt *D, ASTContext *Context,
388  llvm::function_ref<QualType(const Expr *)> GetType, StringRef Message) {
389  const auto *FirstDecl = dyn_cast<VarDecl>(*D->decl_begin());
390  // Ensure that there is at least one VarDecl within the DeclStmt.
391  if (!FirstDecl)
392  return;
393 
394  const QualType FirstDeclType = FirstDecl->getType().getCanonicalType();
395 
396  std::vector<FixItHint> StarRemovals;
397  for (const auto *Dec : D->decls()) {
398  const auto *V = cast<VarDecl>(Dec);
399  // Ensure that every DeclStmt child is a VarDecl.
400  if (!V)
401  return;
402 
403  const auto *Expr = V->getInit()->IgnoreParenImpCasts();
404  // Ensure that every VarDecl has an initializer.
405  if (!Expr)
406  return;
407 
408  // If VarDecl and Initializer have mismatching unqualified types.
409  if (!Context->hasSameUnqualifiedType(V->getType(), GetType(Expr)))
410  return;
411 
412  // All subsequent variables in this declaration should have the same
413  // canonical type. For example, we don't want to use `auto` in
414  // `T *p = new T, **pp = new T*;`.
415  if (FirstDeclType != V->getType().getCanonicalType())
416  return;
417 
418  if (RemoveStars) {
419  // Remove explicitly written '*' from declarations where there's more than
420  // one declaration in the declaration list.
421  if (Dec == *D->decl_begin())
422  continue;
423 
424  auto Q = V->getTypeSourceInfo()->getTypeLoc().getAs<PointerTypeLoc>();
425  while (!Q.isNull()) {
426  StarRemovals.push_back(FixItHint::CreateRemoval(Q.getStarLoc()));
427  Q = Q.getNextTypeLoc().getAs<PointerTypeLoc>();
428  }
429  }
430  }
431 
432  // FIXME: There is, however, one case we can address: when the VarDecl pointee
433  // is the same as the initializer, just more CV-qualified. However, TypeLoc
434  // information is not reliable where CV qualifiers are concerned so we can't
435  // do anything about this case for now.
436  TypeLoc Loc = FirstDecl->getTypeSourceInfo()->getTypeLoc();
437  if (!RemoveStars) {
438  while (Loc.getTypeLocClass() == TypeLoc::Pointer ||
439  Loc.getTypeLocClass() == TypeLoc::Qualified)
440  Loc = Loc.getNextTypeLoc();
441  }
442  while (Loc.getTypeLocClass() == TypeLoc::LValueReference ||
443  Loc.getTypeLocClass() == TypeLoc::RValueReference ||
444  Loc.getTypeLocClass() == TypeLoc::Qualified) {
445  Loc = Loc.getNextTypeLoc();
446  }
447  SourceRange Range(Loc.getSourceRange());
448 
449  if (MinTypeNameLength != 0 &&
450  GetTypeNameLength(RemoveStars,
451  tooling::fixit::getText(Loc.getSourceRange(),
452  FirstDecl->getASTContext())) <
453  MinTypeNameLength)
454  return;
455 
456  auto Diag = diag(Range.getBegin(), Message);
457 
458  // Space after 'auto' to handle cases where the '*' in the pointer type is
459  // next to the identifier. This avoids changing 'int *p' into 'autop'.
460  // FIXME: This doesn't work for function pointers because the variable name
461  // is inside the type.
462  Diag << FixItHint::CreateReplacement(Range, RemoveStars ? "auto " : "auto")
463  << StarRemovals;
464 }
465 
466 void UseAutoCheck::check(const MatchFinder::MatchResult &Result) {
467  if (const auto *Decl = Result.Nodes.getNodeAs<DeclStmt>(IteratorDeclStmtId)) {
468  replaceIterators(Decl, Result.Context);
469  } else if (const auto *Decl =
470  Result.Nodes.getNodeAs<DeclStmt>(DeclWithNewId)) {
471  replaceExpr(Decl, Result.Context,
472  [](const Expr *Expr) { return Expr->getType(); },
473  "use auto when initializing with new to avoid "
474  "duplicating the type name");
475  } else if (const auto *Decl =
476  Result.Nodes.getNodeAs<DeclStmt>(DeclWithCastId)) {
477  replaceExpr(
478  Decl, Result.Context,
479  [](const Expr *Expr) {
480  return cast<ExplicitCastExpr>(Expr)->getTypeAsWritten();
481  },
482  "use auto when initializing with a cast to avoid duplicating the type "
483  "name");
484  } else if (const auto *Decl =
485  Result.Nodes.getNodeAs<DeclStmt>(DeclWithTemplateCastId)) {
486  replaceExpr(
487  Decl, Result.Context,
488  [](const Expr *Expr) {
489  return cast<CallExpr>(Expr->IgnoreImplicit())
490  ->getDirectCallee()
491  ->getReturnType();
492  },
493  "use auto when initializing with a template cast to avoid duplicating "
494  "the type name");
495  } else {
496  llvm_unreachable("Bad Callback. No node provided.");
497  }
498 }
499 
500 } // namespace modernize
501 } // namespace tidy
502 } // namespace clang
SourceLocation Loc
&#39;#&#39; location in the include directive
const FunctionDecl * Decl
AST_POLYMORPHIC_MATCHER(isInAbseilFile, AST_POLYMORPHIC_SUPPORTED_TYPES(Decl, Stmt, TypeLoc, NestedNameSpecifierLoc))
Matches AST nodes that were found within Abseil files.
Definition: AbseilMatcher.h:31
constexpr llvm::StringLiteral Message
const LangOptions & getLangOpts() const
Returns the language options from the context.
void store(ClangTidyOptions::OptionMap &Options, StringRef LocalName, StringRef Value) const
Stores an option with the check-local name LocalName with string value Value to Options.
static constexpr llvm::StringLiteral Name
std::map< std::string, std::string > OptionMap
FunctionInfo Info
CodeCompletionBuilder Builder
===– Representation.cpp - ClangDoc Representation --------—*- C++ -*-===//
CharSourceRange Range
SourceRange for the file name.
const Expr * E
DiagnosticBuilder diag(SourceLocation Loc, StringRef Description, DiagnosticIDs::Level Level=DiagnosticIDs::Warning)
Add a diagnostic with the check&#39;s name.
AST_MATCHER_P(CXXMethodDecl, hasCanonicalDecl, ast_matchers::internal::Matcher< CXXMethodDecl >, InnerMatcher)