clang-tools 17.0.0git
LoopConvertCheck.cpp
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1//===--- LoopConvertCheck.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 "LoopConvertCheck.h"
10#include "clang/AST/ASTContext.h"
11#include "clang/ASTMatchers/ASTMatchFinder.h"
12#include "clang/Basic/LLVM.h"
13#include "clang/Basic/LangOptions.h"
14#include "clang/Basic/SourceLocation.h"
15#include "clang/Basic/SourceManager.h"
16#include "clang/Lex/Lexer.h"
17#include "llvm/ADT/ArrayRef.h"
18#include "llvm/ADT/SmallVector.h"
19#include "llvm/ADT/StringRef.h"
20#include "llvm/Support/Casting.h"
21#include "llvm/Support/raw_ostream.h"
22#include <cassert>
23#include <cstring>
24#include <optional>
25#include <utility>
26
27using namespace clang::ast_matchers;
28using namespace llvm;
29
30namespace clang::tidy {
31
32template <> struct OptionEnumMapping<modernize::Confidence::Level> {
33 static llvm::ArrayRef<std::pair<modernize::Confidence::Level, StringRef>>
35 static constexpr std::pair<modernize::Confidence::Level, StringRef>
36 Mapping[] = {{modernize::Confidence::CL_Reasonable, "reasonable"},
39 return ArrayRef(Mapping);
40 }
41};
42
43template <> struct OptionEnumMapping<modernize::VariableNamer::NamingStyle> {
44 static llvm::ArrayRef<
45 std::pair<modernize::VariableNamer::NamingStyle, StringRef>>
47 static constexpr std::pair<modernize::VariableNamer::NamingStyle, StringRef>
48 Mapping[] = {{modernize::VariableNamer::NS_CamelCase, "CamelCase"},
52 return ArrayRef(Mapping);
53 }
54};
55
56namespace modernize {
57
58static const char LoopNameArray[] = "forLoopArray";
59static const char LoopNameIterator[] = "forLoopIterator";
60static const char LoopNameReverseIterator[] = "forLoopReverseIterator";
61static const char LoopNamePseudoArray[] = "forLoopPseudoArray";
62static const char ConditionBoundName[] = "conditionBound";
63static const char InitVarName[] = "initVar";
64static const char BeginCallName[] = "beginCall";
65static const char EndCallName[] = "endCall";
66static const char EndVarName[] = "endVar";
67static const char DerefByValueResultName[] = "derefByValueResult";
68static const char DerefByRefResultName[] = "derefByRefResult";
69
70static const StatementMatcher integerComparisonMatcher() {
71 return expr(ignoringParenImpCasts(
72 declRefExpr(to(varDecl(equalsBoundNode(InitVarName))))));
73}
74
75static const DeclarationMatcher initToZeroMatcher() {
76 return varDecl(
77 hasInitializer(ignoringParenImpCasts(integerLiteral(equals(0)))))
78 .bind(InitVarName);
79}
80
81static const StatementMatcher incrementVarMatcher() {
82 return declRefExpr(to(varDecl(equalsBoundNode(InitVarName))));
83}
84
85static StatementMatcher
86arrayConditionMatcher(internal::Matcher<Expr> LimitExpr) {
87 return binaryOperator(
88 anyOf(allOf(hasOperatorName("<"), hasLHS(integerComparisonMatcher()),
89 hasRHS(LimitExpr)),
90 allOf(hasOperatorName(">"), hasLHS(LimitExpr),
91 hasRHS(integerComparisonMatcher())),
92 allOf(hasOperatorName("!="),
93 hasOperands(integerComparisonMatcher(), LimitExpr))));
94}
95
96/// The matcher for loops over arrays.
97/// \code
98/// for (int i = 0; i < 3 + 2; ++i) { ... }
99/// \endcode
100/// The following string identifiers are bound to these parts of the AST:
101/// ConditionBoundName: '3 + 2' (as an Expr)
102/// InitVarName: 'i' (as a VarDecl)
103/// LoopName: The entire for loop (as a ForStmt)
104///
105/// Client code will need to make sure that:
106/// - The index variable is only used as an array index.
107/// - All arrays indexed by the loop are the same.
108StatementMatcher makeArrayLoopMatcher() {
109 StatementMatcher ArrayBoundMatcher =
110 expr(hasType(isInteger())).bind(ConditionBoundName);
111
112 return forStmt(unless(isInTemplateInstantiation()),
113 hasLoopInit(declStmt(hasSingleDecl(initToZeroMatcher()))),
114 hasCondition(arrayConditionMatcher(ArrayBoundMatcher)),
115 hasIncrement(
116 unaryOperator(hasOperatorName("++"),
117 hasUnaryOperand(incrementVarMatcher()))))
118 .bind(LoopNameArray);
119}
120
121/// The matcher used for iterator-based for loops.
122///
123/// This matcher is more flexible than array-based loops. It will match
124/// catch loops of the following textual forms (regardless of whether the
125/// iterator type is actually a pointer type or a class type):
126///
127/// \code
128/// for (containerType::iterator it = container.begin(),
129/// e = createIterator(); it != e; ++it) { ... }
130/// for (containerType::iterator it = container.begin();
131/// it != anotherContainer.end(); ++it) { ... }
132/// \endcode
133/// The following string identifiers are bound to the parts of the AST:
134/// InitVarName: 'it' (as a VarDecl)
135/// LoopName: The entire for loop (as a ForStmt)
136/// In the first example only:
137/// EndVarName: 'e' (as a VarDecl)
138/// In the second example only:
139/// EndCallName: 'container.end()' (as a CXXMemberCallExpr)
140///
141/// Client code will need to make sure that:
142/// - The two containers on which 'begin' and 'end' are called are the same.
143StatementMatcher makeIteratorLoopMatcher(bool IsReverse) {
144
145 auto BeginNameMatcher = IsReverse ? hasAnyName("rbegin", "crbegin")
146 : hasAnyName("begin", "cbegin");
147
148 auto EndNameMatcher =
149 IsReverse ? hasAnyName("rend", "crend") : hasAnyName("end", "cend");
150
151 StatementMatcher BeginCallMatcher =
152 cxxMemberCallExpr(argumentCountIs(0),
153 callee(cxxMethodDecl(BeginNameMatcher)))
154 .bind(BeginCallName);
155
156 DeclarationMatcher InitDeclMatcher =
157 varDecl(hasInitializer(anyOf(ignoringParenImpCasts(BeginCallMatcher),
158 materializeTemporaryExpr(
159 ignoringParenImpCasts(BeginCallMatcher)),
160 hasDescendant(BeginCallMatcher))))
161 .bind(InitVarName);
162
163 DeclarationMatcher EndDeclMatcher =
164 varDecl(hasInitializer(anything())).bind(EndVarName);
165
166 StatementMatcher EndCallMatcher = cxxMemberCallExpr(
167 argumentCountIs(0), callee(cxxMethodDecl(EndNameMatcher)));
168
169 StatementMatcher IteratorBoundMatcher =
170 expr(anyOf(ignoringParenImpCasts(
171 declRefExpr(to(varDecl(equalsBoundNode(EndVarName))))),
172 ignoringParenImpCasts(expr(EndCallMatcher).bind(EndCallName)),
173 materializeTemporaryExpr(ignoringParenImpCasts(
174 expr(EndCallMatcher).bind(EndCallName)))));
175
176 StatementMatcher IteratorComparisonMatcher = expr(ignoringParenImpCasts(
177 declRefExpr(to(varDecl(equalsBoundNode(InitVarName))))));
178
179 // This matcher tests that a declaration is a CXXRecordDecl that has an
180 // overloaded operator*(). If the operator*() returns by value instead of by
181 // reference then the return type is tagged with DerefByValueResultName.
182 internal::Matcher<VarDecl> TestDerefReturnsByValue =
183 hasType(hasUnqualifiedDesugaredType(
184 recordType(hasDeclaration(cxxRecordDecl(hasMethod(cxxMethodDecl(
185 hasOverloadedOperatorName("*"),
186 anyOf(
187 // Tag the return type if it's by value.
188 returns(qualType(unless(hasCanonicalType(referenceType())))
190 returns(
191 // Skip loops where the iterator's operator* returns an
192 // rvalue reference. This is just weird.
193 qualType(unless(hasCanonicalType(rValueReferenceType())))
194 .bind(DerefByRefResultName))))))))));
195
196 return forStmt(
197 unless(isInTemplateInstantiation()),
198 hasLoopInit(anyOf(declStmt(declCountIs(2),
199 containsDeclaration(0, InitDeclMatcher),
200 containsDeclaration(1, EndDeclMatcher)),
201 declStmt(hasSingleDecl(InitDeclMatcher)))),
202 hasCondition(ignoringImplicit(binaryOperation(
203 hasOperatorName("!="), hasOperands(IteratorComparisonMatcher,
204 IteratorBoundMatcher)))),
205 hasIncrement(anyOf(
206 unaryOperator(hasOperatorName("++"),
207 hasUnaryOperand(declRefExpr(
208 to(varDecl(equalsBoundNode(InitVarName)))))),
209 cxxOperatorCallExpr(
210 hasOverloadedOperatorName("++"),
211 hasArgument(0, declRefExpr(to(
212 varDecl(equalsBoundNode(InitVarName),
213 TestDerefReturnsByValue))))))))
214 .bind(IsReverse ? LoopNameReverseIterator : LoopNameIterator);
215}
216
217/// The matcher used for array-like containers (pseudoarrays).
218///
219/// This matcher is more flexible than array-based loops. It will match
220/// loops of the following textual forms (regardless of whether the
221/// iterator type is actually a pointer type or a class type):
222///
223/// \code
224/// for (int i = 0, j = container.size(); i < j; ++i) { ... }
225/// for (int i = 0; i < container.size(); ++i) { ... }
226/// \endcode
227/// The following string identifiers are bound to the parts of the AST:
228/// InitVarName: 'i' (as a VarDecl)
229/// LoopName: The entire for loop (as a ForStmt)
230/// In the first example only:
231/// EndVarName: 'j' (as a VarDecl)
232/// In the second example only:
233/// EndCallName: 'container.size()' (as a CXXMemberCallExpr)
234///
235/// Client code will need to make sure that:
236/// - The containers on which 'size()' is called is the container indexed.
237/// - The index variable is only used in overloaded operator[] or
238/// container.at().
239/// - The container's iterators would not be invalidated during the loop.
240StatementMatcher makePseudoArrayLoopMatcher() {
241 // Test that the incoming type has a record declaration that has methods
242 // called 'begin' and 'end'. If the incoming type is const, then make sure
243 // these methods are also marked const.
244 //
245 // FIXME: To be completely thorough this matcher should also ensure the
246 // return type of begin/end is an iterator that dereferences to the same as
247 // what operator[] or at() returns. Such a test isn't likely to fail except
248 // for pathological cases.
249 //
250 // FIXME: Also, a record doesn't necessarily need begin() and end(). Free
251 // functions called begin() and end() taking the container as an argument
252 // are also allowed.
253 TypeMatcher RecordWithBeginEnd = qualType(anyOf(
254 qualType(isConstQualified(),
255 hasUnqualifiedDesugaredType(recordType(hasDeclaration(
256 cxxRecordDecl(isSameOrDerivedFrom(cxxRecordDecl(
257 hasMethod(cxxMethodDecl(hasName("begin"), isConst())),
258 hasMethod(cxxMethodDecl(hasName("end"),
259 isConst())))))) // hasDeclaration
260 ))), // qualType
261 qualType(unless(isConstQualified()),
262 hasUnqualifiedDesugaredType(recordType(hasDeclaration(
263 cxxRecordDecl(isSameOrDerivedFrom(cxxRecordDecl(
264 hasMethod(hasName("begin")),
265 hasMethod(hasName("end"))))))))) // qualType
266 ));
267
268 StatementMatcher SizeCallMatcher = cxxMemberCallExpr(
269 argumentCountIs(0), callee(cxxMethodDecl(hasAnyName("size", "length"))),
270 on(anyOf(hasType(pointsTo(RecordWithBeginEnd)),
271 hasType(RecordWithBeginEnd))));
272
273 StatementMatcher EndInitMatcher =
274 expr(anyOf(ignoringParenImpCasts(expr(SizeCallMatcher).bind(EndCallName)),
275 explicitCastExpr(hasSourceExpression(ignoringParenImpCasts(
276 expr(SizeCallMatcher).bind(EndCallName))))));
277
278 DeclarationMatcher EndDeclMatcher =
279 varDecl(hasInitializer(EndInitMatcher)).bind(EndVarName);
280
281 StatementMatcher IndexBoundMatcher =
282 expr(anyOf(ignoringParenImpCasts(
283 declRefExpr(to(varDecl(equalsBoundNode(EndVarName))))),
284 EndInitMatcher));
285
286 return forStmt(unless(isInTemplateInstantiation()),
287 hasLoopInit(
288 anyOf(declStmt(declCountIs(2),
289 containsDeclaration(0, initToZeroMatcher()),
290 containsDeclaration(1, EndDeclMatcher)),
291 declStmt(hasSingleDecl(initToZeroMatcher())))),
292 hasCondition(arrayConditionMatcher(IndexBoundMatcher)),
293 hasIncrement(
294 unaryOperator(hasOperatorName("++"),
295 hasUnaryOperand(incrementVarMatcher()))))
296 .bind(LoopNamePseudoArray);
297}
298
299/// Determine whether Init appears to be an initializing an iterator.
300///
301/// If it is, returns the object whose begin() or end() method is called, and
302/// the output parameter isArrow is set to indicate whether the initialization
303/// is called via . or ->.
304static const Expr *getContainerFromBeginEndCall(const Expr *Init, bool IsBegin,
305 bool *IsArrow, bool IsReverse) {
306 // FIXME: Maybe allow declaration/initialization outside of the for loop.
307 const auto *TheCall = dyn_cast_or_null<CXXMemberCallExpr>(
309 if (!TheCall || TheCall->getNumArgs() != 0)
310 return nullptr;
311
312 const auto *Member = dyn_cast<MemberExpr>(TheCall->getCallee());
313 if (!Member)
314 return nullptr;
315 StringRef Name = Member->getMemberDecl()->getName();
316 if (!Name.consume_back(IsBegin ? "begin" : "end"))
317 return nullptr;
318 if (IsReverse && !Name.consume_back("r"))
319 return nullptr;
320 if (!Name.empty() && !Name.equals("c"))
321 return nullptr;
322
323 const Expr *SourceExpr = Member->getBase();
324 if (!SourceExpr)
325 return nullptr;
326
327 *IsArrow = Member->isArrow();
328 return SourceExpr;
329}
330
331/// Determines the container whose begin() and end() functions are called
332/// for an iterator-based loop.
333///
334/// BeginExpr must be a member call to a function named "begin()", and EndExpr
335/// must be a member.
336static const Expr *findContainer(ASTContext *Context, const Expr *BeginExpr,
337 const Expr *EndExpr,
338 bool *ContainerNeedsDereference,
339 bool IsReverse) {
340 // Now that we know the loop variable and test expression, make sure they are
341 // valid.
342 bool BeginIsArrow = false;
343 bool EndIsArrow = false;
344 const Expr *BeginContainerExpr = getContainerFromBeginEndCall(
345 BeginExpr, /*IsBegin=*/true, &BeginIsArrow, IsReverse);
346 if (!BeginContainerExpr)
347 return nullptr;
348
349 const Expr *EndContainerExpr = getContainerFromBeginEndCall(
350 EndExpr, /*IsBegin=*/false, &EndIsArrow, IsReverse);
351 // Disallow loops that try evil things like this (note the dot and arrow):
352 // for (IteratorType It = Obj.begin(), E = Obj->end(); It != E; ++It) { }
353 if (!EndContainerExpr || BeginIsArrow != EndIsArrow ||
354 !areSameExpr(Context, EndContainerExpr, BeginContainerExpr))
355 return nullptr;
356
357 *ContainerNeedsDereference = BeginIsArrow;
358 return BeginContainerExpr;
359}
360
361/// Obtain the original source code text from a SourceRange.
362static StringRef getStringFromRange(SourceManager &SourceMgr,
363 const LangOptions &LangOpts,
364 SourceRange Range) {
365 if (SourceMgr.getFileID(Range.getBegin()) !=
366 SourceMgr.getFileID(Range.getEnd())) {
367 return StringRef(); // Empty string.
368 }
369
370 return Lexer::getSourceText(CharSourceRange(Range, true), SourceMgr,
371 LangOpts);
372}
373
374/// If the given expression is actually a DeclRefExpr or a MemberExpr,
375/// find and return the underlying ValueDecl; otherwise, return NULL.
376static const ValueDecl *getReferencedVariable(const Expr *E) {
377 if (const DeclRefExpr *DRE = getDeclRef(E))
378 return dyn_cast<VarDecl>(DRE->getDecl());
379 if (const auto *Mem = dyn_cast<MemberExpr>(E->IgnoreParenImpCasts()))
380 return dyn_cast<FieldDecl>(Mem->getMemberDecl());
381 return nullptr;
382}
383
384/// Returns true when the given expression is a member expression
385/// whose base is `this` (implicitly or not).
386static bool isDirectMemberExpr(const Expr *E) {
387 if (const auto *Member = dyn_cast<MemberExpr>(E->IgnoreParenImpCasts()))
388 return isa<CXXThisExpr>(Member->getBase()->IgnoreParenImpCasts());
389 return false;
390}
391
392/// Given an expression that represents an usage of an element from the
393/// containter that we are iterating over, returns false when it can be
394/// guaranteed this element cannot be modified as a result of this usage.
395static bool canBeModified(ASTContext *Context, const Expr *E) {
396 if (E->getType().isConstQualified())
397 return false;
398 auto Parents = Context->getParents(*E);
399 if (Parents.size() != 1)
400 return true;
401 if (const auto *Cast = Parents[0].get<ImplicitCastExpr>()) {
402 if ((Cast->getCastKind() == CK_NoOp &&
403 Context->hasSameType(Cast->getType(), E->getType().withConst())) ||
404 (Cast->getCastKind() == CK_LValueToRValue &&
405 !Cast->getType().isNull() && Cast->getType()->isFundamentalType()))
406 return false;
407 }
408 // FIXME: Make this function more generic.
409 return true;
410}
411
412/// Returns true when it can be guaranteed that the elements of the
413/// container are not being modified.
414static bool usagesAreConst(ASTContext *Context, const UsageResult &Usages) {
415 for (const Usage &U : Usages) {
416 // Lambda captures are just redeclarations (VarDecl) of the same variable,
417 // not expressions. If we want to know if a variable that is captured by
418 // reference can be modified in an usage inside the lambda's body, we need
419 // to find the expression corresponding to that particular usage, later in
420 // this loop.
421 if (U.Kind != Usage::UK_CaptureByCopy && U.Kind != Usage::UK_CaptureByRef &&
422 canBeModified(Context, U.Expression))
423 return false;
424 }
425 return true;
426}
427
428/// Returns true if the elements of the container are never accessed
429/// by reference.
430static bool usagesReturnRValues(const UsageResult &Usages) {
431 for (const auto &U : Usages) {
432 if (U.Expression && !U.Expression->isPRValue())
433 return false;
434 }
435 return true;
436}
437
438/// Returns true if the container is const-qualified.
439static bool containerIsConst(const Expr *ContainerExpr, bool Dereference) {
440 if (const auto *VDec = getReferencedVariable(ContainerExpr)) {
441 QualType CType = VDec->getType();
442 if (Dereference) {
443 if (!CType->isPointerType())
444 return false;
445 CType = CType->getPointeeType();
446 }
447 // If VDec is a reference to a container, Dereference is false,
448 // but we still need to check the const-ness of the underlying container
449 // type.
450 CType = CType.getNonReferenceType();
451 return CType.isConstQualified();
452 }
453 return false;
454}
455
456LoopConvertCheck::RangeDescriptor::RangeDescriptor()
457 : ContainerNeedsDereference(false), DerefByConstRef(false),
458 DerefByValue(false), NeedsReverseCall(false) {}
459
460LoopConvertCheck::LoopConvertCheck(StringRef Name, ClangTidyContext *Context)
461 : ClangTidyCheck(Name, Context), TUInfo(new TUTrackingInfo),
462 MaxCopySize(Options.get("MaxCopySize", 16ULL)),
463 MinConfidence(Options.get("MinConfidence", Confidence::CL_Reasonable)),
464 NamingStyle(Options.get("NamingStyle", VariableNamer::NS_CamelCase)),
465 Inserter(Options.getLocalOrGlobal("IncludeStyle",
466 utils::IncludeSorter::IS_LLVM),
467 areDiagsSelfContained()),
468 UseCxx20IfAvailable(Options.get("UseCxx20ReverseRanges", true)),
469 ReverseFunction(Options.get("MakeReverseRangeFunction", "")),
470 ReverseHeader(Options.get("MakeReverseRangeHeader", "")) {
471
472 if (ReverseFunction.empty() && !ReverseHeader.empty()) {
474 "modernize-loop-convert: 'MakeReverseRangeHeader' is set but "
475 "'MakeReverseRangeFunction' is not, disabling reverse loop "
476 "transformation");
477 UseReverseRanges = false;
478 } else if (ReverseFunction.empty()) {
479 UseReverseRanges = UseCxx20IfAvailable && getLangOpts().CPlusPlus20;
480 } else {
481 UseReverseRanges = true;
482 }
483}
484
486 Options.store(Opts, "MaxCopySize", MaxCopySize);
487 Options.store(Opts, "MinConfidence", MinConfidence);
488 Options.store(Opts, "NamingStyle", NamingStyle);
489 Options.store(Opts, "IncludeStyle", Inserter.getStyle());
490 Options.store(Opts, "UseCxx20ReverseRanges", UseCxx20IfAvailable);
491 Options.store(Opts, "MakeReverseRangeFunction", ReverseFunction);
492 Options.store(Opts, "MakeReverseRangeHeader", ReverseHeader);
493}
494
495void LoopConvertCheck::registerPPCallbacks(const SourceManager &SM,
496 Preprocessor *PP,
497 Preprocessor *ModuleExpanderPP) {
498 Inserter.registerPreprocessor(PP);
499}
500
501void LoopConvertCheck::registerMatchers(MatchFinder *Finder) {
502 Finder->addMatcher(traverse(TK_AsIs, makeArrayLoopMatcher()), this);
503 Finder->addMatcher(traverse(TK_AsIs, makeIteratorLoopMatcher(false)), this);
504 Finder->addMatcher(traverse(TK_AsIs, makePseudoArrayLoopMatcher()), this);
505 if (UseReverseRanges)
506 Finder->addMatcher(traverse(TK_AsIs, makeIteratorLoopMatcher(true)), this);
507}
508
509/// Given the range of a single declaration, such as:
510/// \code
511/// unsigned &ThisIsADeclarationThatCanSpanSeveralLinesOfCode =
512/// InitializationValues[I];
513/// next_instruction;
514/// \endcode
515/// Finds the range that has to be erased to remove this declaration without
516/// leaving empty lines, by extending the range until the beginning of the
517/// next instruction.
518///
519/// We need to delete a potential newline after the deleted alias, as
520/// clang-format will leave empty lines untouched. For all other formatting we
521/// rely on clang-format to fix it.
522void LoopConvertCheck::getAliasRange(SourceManager &SM, SourceRange &Range) {
523 bool Invalid = false;
524 const char *TextAfter =
525 SM.getCharacterData(Range.getEnd().getLocWithOffset(1), &Invalid);
526 if (Invalid)
527 return;
528 unsigned Offset = std::strspn(TextAfter, " \t\r\n");
529 Range =
530 SourceRange(Range.getBegin(), Range.getEnd().getLocWithOffset(Offset));
531}
532
533/// Computes the changes needed to convert a given for loop, and
534/// applies them.
535void LoopConvertCheck::doConversion(
536 ASTContext *Context, const VarDecl *IndexVar,
537 const ValueDecl *MaybeContainer, const UsageResult &Usages,
538 const DeclStmt *AliasDecl, bool AliasUseRequired, bool AliasFromForInit,
539 const ForStmt *Loop, RangeDescriptor Descriptor) {
540 std::string VarName;
541 bool VarNameFromAlias = (Usages.size() == 1) && AliasDecl;
542 bool AliasVarIsRef = false;
543 bool CanCopy = true;
544 std::vector<FixItHint> FixIts;
545 if (VarNameFromAlias) {
546 const auto *AliasVar = cast<VarDecl>(AliasDecl->getSingleDecl());
547 VarName = AliasVar->getName().str();
548
549 // Use the type of the alias if it's not the same
550 QualType AliasVarType = AliasVar->getType();
551 assert(!AliasVarType.isNull() && "Type in VarDecl is null");
552 if (AliasVarType->isReferenceType()) {
553 AliasVarType = AliasVarType.getNonReferenceType();
554 AliasVarIsRef = true;
555 }
556 if (Descriptor.ElemType.isNull() ||
557 !Context->hasSameUnqualifiedType(AliasVarType, Descriptor.ElemType))
558 Descriptor.ElemType = AliasVarType;
559
560 // We keep along the entire DeclStmt to keep the correct range here.
561 SourceRange ReplaceRange = AliasDecl->getSourceRange();
562
563 std::string ReplacementText;
564 if (AliasUseRequired) {
565 ReplacementText = VarName;
566 } else if (AliasFromForInit) {
567 // FIXME: Clang includes the location of the ';' but only for DeclStmt's
568 // in a for loop's init clause. Need to put this ';' back while removing
569 // the declaration of the alias variable. This is probably a bug.
570 ReplacementText = ";";
571 } else {
572 // Avoid leaving empty lines or trailing whitespaces.
573 getAliasRange(Context->getSourceManager(), ReplaceRange);
574 }
575
576 FixIts.push_back(FixItHint::CreateReplacement(
577 CharSourceRange::getTokenRange(ReplaceRange), ReplacementText));
578 // No further replacements are made to the loop, since the iterator or index
579 // was used exactly once - in the initialization of AliasVar.
580 } else {
581 VariableNamer Namer(&TUInfo->getGeneratedDecls(),
582 &TUInfo->getParentFinder().getStmtToParentStmtMap(),
583 Loop, IndexVar, MaybeContainer, Context, NamingStyle);
584 VarName = Namer.createIndexName();
585 // First, replace all usages of the array subscript expression with our new
586 // variable.
587 for (const auto &Usage : Usages) {
588 std::string ReplaceText;
589 SourceRange Range = Usage.Range;
590 if (Usage.Expression) {
591 // If this is an access to a member through the arrow operator, after
592 // the replacement it must be accessed through the '.' operator.
593 ReplaceText = Usage.Kind == Usage::UK_MemberThroughArrow ? VarName + "."
594 : VarName;
595 auto Parents = Context->getParents(*Usage.Expression);
596 if (Parents.size() == 1) {
597 if (const auto *Paren = Parents[0].get<ParenExpr>()) {
598 // Usage.Expression will be replaced with the new index variable,
599 // and parenthesis around a simple DeclRefExpr can always be
600 // removed.
601 Range = Paren->getSourceRange();
602 } else if (const auto *UOP = Parents[0].get<UnaryOperator>()) {
603 // If we are taking the address of the loop variable, then we must
604 // not use a copy, as it would mean taking the address of the loop's
605 // local index instead.
606 // FIXME: This won't catch cases where the address is taken outside
607 // of the loop's body (for instance, in a function that got the
608 // loop's index as a const reference parameter), or where we take
609 // the address of a member (like "&Arr[i].A.B.C").
610 if (UOP->getOpcode() == UO_AddrOf)
611 CanCopy = false;
612 }
613 }
614 } else {
615 // The Usage expression is only null in case of lambda captures (which
616 // are VarDecl). If the index is captured by value, add '&' to capture
617 // by reference instead.
618 ReplaceText =
619 Usage.Kind == Usage::UK_CaptureByCopy ? "&" + VarName : VarName;
620 }
621 TUInfo->getReplacedVars().insert(std::make_pair(Loop, IndexVar));
622 FixIts.push_back(FixItHint::CreateReplacement(
623 CharSourceRange::getTokenRange(Range), ReplaceText));
624 }
625 }
626
627 // Now, we need to construct the new range expression.
628 SourceRange ParenRange(Loop->getLParenLoc(), Loop->getRParenLoc());
629
630 QualType Type = Context->getAutoDeductType();
631 if (!Descriptor.ElemType.isNull() && Descriptor.ElemType->isFundamentalType())
632 Type = Descriptor.ElemType.getUnqualifiedType();
633 Type = Type.getDesugaredType(*Context);
634
635 // If the new variable name is from the aliased variable, then the reference
636 // type for the new variable should only be used if the aliased variable was
637 // declared as a reference.
638 bool IsCheapToCopy =
639 !Descriptor.ElemType.isNull() &&
640 Descriptor.ElemType.isTriviallyCopyableType(*Context) &&
641 // TypeInfo::Width is in bits.
642 Context->getTypeInfo(Descriptor.ElemType).Width <= 8 * MaxCopySize;
643 bool UseCopy = CanCopy && ((VarNameFromAlias && !AliasVarIsRef) ||
644 (Descriptor.DerefByConstRef && IsCheapToCopy));
645
646 if (!UseCopy) {
647 if (Descriptor.DerefByConstRef) {
648 Type = Context->getLValueReferenceType(Context->getConstType(Type));
649 } else if (Descriptor.DerefByValue) {
650 if (!IsCheapToCopy)
651 Type = Context->getRValueReferenceType(Type);
652 } else {
653 Type = Context->getLValueReferenceType(Type);
654 }
655 }
656
657 SmallString<128> Range;
658 llvm::raw_svector_ostream Output(Range);
659 Output << '(';
660 Type.print(Output, getLangOpts());
661 Output << ' ' << VarName << " : ";
662 if (Descriptor.NeedsReverseCall)
663 Output << getReverseFunction() << '(';
664 if (Descriptor.ContainerNeedsDereference)
665 Output << '*';
666 Output << Descriptor.ContainerString;
667 if (Descriptor.NeedsReverseCall)
668 Output << "))";
669 else
670 Output << ')';
671 FixIts.push_back(FixItHint::CreateReplacement(
672 CharSourceRange::getTokenRange(ParenRange), Range));
673
674 if (Descriptor.NeedsReverseCall && !getReverseHeader().empty()) {
675 if (std::optional<FixItHint> Insertion = Inserter.createIncludeInsertion(
676 Context->getSourceManager().getFileID(Loop->getBeginLoc()),
677 getReverseHeader()))
678 FixIts.push_back(*Insertion);
679 }
680 diag(Loop->getForLoc(), "use range-based for loop instead") << FixIts;
681 TUInfo->getGeneratedDecls().insert(make_pair(Loop, VarName));
682}
683
684/// Returns a string which refers to the container iterated over.
685StringRef LoopConvertCheck::getContainerString(ASTContext *Context,
686 const ForStmt *Loop,
687 const Expr *ContainerExpr) {
688 StringRef ContainerString;
689 ContainerExpr = ContainerExpr->IgnoreParenImpCasts();
690 if (isa<CXXThisExpr>(ContainerExpr)) {
691 ContainerString = "this";
692 } else {
693 // For CXXOperatorCallExpr such as vector_ptr->size() we want the class
694 // object vector_ptr, but for vector[2] we need the whole expression.
695 if (const auto* E = dyn_cast<CXXOperatorCallExpr>(ContainerExpr))
696 if (E->getOperator() != OO_Subscript)
697 ContainerExpr = E->getArg(0);
698 ContainerString =
699 getStringFromRange(Context->getSourceManager(), Context->getLangOpts(),
700 ContainerExpr->getSourceRange());
701 }
702
703 return ContainerString;
704}
705
706/// Determines what kind of 'auto' must be used after converting a for
707/// loop that iterates over an array or pseudoarray.
708void LoopConvertCheck::getArrayLoopQualifiers(ASTContext *Context,
709 const BoundNodes &Nodes,
710 const Expr *ContainerExpr,
711 const UsageResult &Usages,
712 RangeDescriptor &Descriptor) {
713 // On arrays and pseudoarrays, we must figure out the qualifiers from the
714 // usages.
715 if (usagesAreConst(Context, Usages) ||
716 containerIsConst(ContainerExpr, Descriptor.ContainerNeedsDereference)) {
717 Descriptor.DerefByConstRef = true;
718 }
719 if (usagesReturnRValues(Usages)) {
720 // If the index usages (dereference, subscript, at, ...) return rvalues,
721 // then we should not use a reference, because we need to keep the code
722 // correct if it mutates the returned objects.
723 Descriptor.DerefByValue = true;
724 }
725 // Try to find the type of the elements on the container, to check if
726 // they are trivially copyable.
727 for (const Usage &U : Usages) {
728 if (!U.Expression || U.Expression->getType().isNull())
729 continue;
730 QualType Type = U.Expression->getType().getCanonicalType();
731 if (U.Kind == Usage::UK_MemberThroughArrow) {
732 if (!Type->isPointerType()) {
733 continue;
734 }
735 Type = Type->getPointeeType();
736 }
737 Descriptor.ElemType = Type;
738 }
739}
740
741/// Determines what kind of 'auto' must be used after converting an
742/// iterator based for loop.
743void LoopConvertCheck::getIteratorLoopQualifiers(ASTContext *Context,
744 const BoundNodes &Nodes,
745 RangeDescriptor &Descriptor) {
746 // The matchers for iterator loops provide bound nodes to obtain this
747 // information.
748 const auto *InitVar = Nodes.getNodeAs<VarDecl>(InitVarName);
749 QualType CanonicalInitVarType = InitVar->getType().getCanonicalType();
750 const auto *DerefByValueType =
751 Nodes.getNodeAs<QualType>(DerefByValueResultName);
752 Descriptor.DerefByValue = DerefByValueType;
753
754 if (Descriptor.DerefByValue) {
755 // If the dereference operator returns by value then test for the
756 // canonical const qualification of the init variable type.
757 Descriptor.DerefByConstRef = CanonicalInitVarType.isConstQualified();
758 Descriptor.ElemType = *DerefByValueType;
759 } else {
760 if (const auto *DerefType =
761 Nodes.getNodeAs<QualType>(DerefByRefResultName)) {
762 // A node will only be bound with DerefByRefResultName if we're dealing
763 // with a user-defined iterator type. Test the const qualification of
764 // the reference type.
765 auto ValueType = DerefType->getNonReferenceType();
766
767 Descriptor.DerefByConstRef = ValueType.isConstQualified();
768 Descriptor.ElemType = ValueType;
769 } else {
770 // By nature of the matcher this case is triggered only for built-in
771 // iterator types (i.e. pointers).
772 assert(isa<PointerType>(CanonicalInitVarType) &&
773 "Non-class iterator type is not a pointer type");
774
775 // We test for const qualification of the pointed-at type.
776 Descriptor.DerefByConstRef =
777 CanonicalInitVarType->getPointeeType().isConstQualified();
778 Descriptor.ElemType = CanonicalInitVarType->getPointeeType();
779 }
780 }
781}
782
783/// Determines the parameters needed to build the range replacement.
784void LoopConvertCheck::determineRangeDescriptor(
785 ASTContext *Context, const BoundNodes &Nodes, const ForStmt *Loop,
786 LoopFixerKind FixerKind, const Expr *ContainerExpr,
787 const UsageResult &Usages, RangeDescriptor &Descriptor) {
788 Descriptor.ContainerString =
789 std::string(getContainerString(Context, Loop, ContainerExpr));
790 Descriptor.NeedsReverseCall = (FixerKind == LFK_ReverseIterator);
791
792 if (FixerKind == LFK_Iterator || FixerKind == LFK_ReverseIterator)
793 getIteratorLoopQualifiers(Context, Nodes, Descriptor);
794 else
795 getArrayLoopQualifiers(Context, Nodes, ContainerExpr, Usages, Descriptor);
796}
797
798/// Check some of the conditions that must be met for the loop to be
799/// convertible.
800bool LoopConvertCheck::isConvertible(ASTContext *Context,
801 const ast_matchers::BoundNodes &Nodes,
802 const ForStmt *Loop,
803 LoopFixerKind FixerKind) {
804 // In self contained diagnosics mode we don't want dependancies on other
805 // loops, otherwise, If we already modified the range of this for loop, don't
806 // do any further updates on this iteration.
808 TUInfo = std::make_unique<TUTrackingInfo>();
809 else if (TUInfo->getReplacedVars().count(Loop))
810 return false;
811
812 // Check that we have exactly one index variable and at most one end variable.
813 const auto *InitVar = Nodes.getNodeAs<VarDecl>(InitVarName);
814
815 // FIXME: Try to put most of this logic inside a matcher.
816 if (FixerKind == LFK_Iterator || FixerKind == LFK_ReverseIterator) {
817 QualType InitVarType = InitVar->getType();
818 QualType CanonicalInitVarType = InitVarType.getCanonicalType();
819
820 const auto *BeginCall = Nodes.getNodeAs<CXXMemberCallExpr>(BeginCallName);
821 assert(BeginCall && "Bad Callback. No begin call expression");
822 QualType CanonicalBeginType =
823 BeginCall->getMethodDecl()->getReturnType().getCanonicalType();
824 if (CanonicalBeginType->isPointerType() &&
825 CanonicalInitVarType->isPointerType()) {
826 // If the initializer and the variable are both pointers check if the
827 // un-qualified pointee types match, otherwise we don't use auto.
828 if (!Context->hasSameUnqualifiedType(
829 CanonicalBeginType->getPointeeType(),
830 CanonicalInitVarType->getPointeeType()))
831 return false;
832 }
833 } else if (FixerKind == LFK_PseudoArray) {
834 // This call is required to obtain the container.
835 const auto *EndCall = Nodes.getNodeAs<CXXMemberCallExpr>(EndCallName);
836 if (!EndCall || !isa<MemberExpr>(EndCall->getCallee()))
837 return false;
838 }
839 return true;
840}
841
842void LoopConvertCheck::check(const MatchFinder::MatchResult &Result) {
843 const BoundNodes &Nodes = Result.Nodes;
844 Confidence ConfidenceLevel(Confidence::CL_Safe);
845 ASTContext *Context = Result.Context;
846
847 const ForStmt *Loop;
848 LoopFixerKind FixerKind;
849 RangeDescriptor Descriptor;
850
851 if ((Loop = Nodes.getNodeAs<ForStmt>(LoopNameArray))) {
852 FixerKind = LFK_Array;
853 } else if ((Loop = Nodes.getNodeAs<ForStmt>(LoopNameIterator))) {
854 FixerKind = LFK_Iterator;
855 } else if ((Loop = Nodes.getNodeAs<ForStmt>(LoopNameReverseIterator))) {
856 FixerKind = LFK_ReverseIterator;
857 } else {
858 Loop = Nodes.getNodeAs<ForStmt>(LoopNamePseudoArray);
859 assert(Loop && "Bad Callback. No for statement");
860 FixerKind = LFK_PseudoArray;
861 }
862
863 if (!isConvertible(Context, Nodes, Loop, FixerKind))
864 return;
865
866 const auto *LoopVar = Nodes.getNodeAs<VarDecl>(InitVarName);
867 const auto *EndVar = Nodes.getNodeAs<VarDecl>(EndVarName);
868
869 // If the loop calls end()/size() after each iteration, lower our confidence
870 // level.
871 if (FixerKind != LFK_Array && !EndVar)
872 ConfidenceLevel.lowerTo(Confidence::CL_Reasonable);
873
874 // If the end comparison isn't a variable, we can try to work with the
875 // expression the loop variable is being tested against instead.
876 const auto *EndCall = Nodes.getNodeAs<CXXMemberCallExpr>(EndCallName);
877 const auto *BoundExpr = Nodes.getNodeAs<Expr>(ConditionBoundName);
878
879 // Find container expression of iterators and pseudoarrays, and determine if
880 // this expression needs to be dereferenced to obtain the container.
881 // With array loops, the container is often discovered during the
882 // ForLoopIndexUseVisitor traversal.
883 const Expr *ContainerExpr = nullptr;
884 if (FixerKind == LFK_Iterator || FixerKind == LFK_ReverseIterator) {
885 ContainerExpr = findContainer(
886 Context, LoopVar->getInit(), EndVar ? EndVar->getInit() : EndCall,
887 &Descriptor.ContainerNeedsDereference,
888 /*IsReverse=*/FixerKind == LFK_ReverseIterator);
889 } else if (FixerKind == LFK_PseudoArray) {
890 ContainerExpr = EndCall->getImplicitObjectArgument();
891 Descriptor.ContainerNeedsDereference =
892 dyn_cast<MemberExpr>(EndCall->getCallee())->isArrow();
893 }
894
895 // We must know the container or an array length bound.
896 if (!ContainerExpr && !BoundExpr)
897 return;
898
899 ForLoopIndexUseVisitor Finder(Context, LoopVar, EndVar, ContainerExpr,
900 BoundExpr,
901 Descriptor.ContainerNeedsDereference);
902
903 // Find expressions and variables on which the container depends.
904 if (ContainerExpr) {
905 ComponentFinderASTVisitor ComponentFinder;
906 ComponentFinder.findExprComponents(ContainerExpr->IgnoreParenImpCasts());
907 Finder.addComponents(ComponentFinder.getComponents());
908 }
909
910 // Find usages of the loop index. If they are not used in a convertible way,
911 // stop here.
912 if (!Finder.findAndVerifyUsages(Loop->getBody()))
913 return;
914 ConfidenceLevel.lowerTo(Finder.getConfidenceLevel());
915
916 // Obtain the container expression, if we don't have it yet.
917 if (FixerKind == LFK_Array) {
918 ContainerExpr = Finder.getContainerIndexed()->IgnoreParenImpCasts();
919
920 // Very few loops are over expressions that generate arrays rather than
921 // array variables. Consider loops over arrays that aren't just represented
922 // by a variable to be risky conversions.
923 if (!getReferencedVariable(ContainerExpr) &&
924 !isDirectMemberExpr(ContainerExpr))
925 ConfidenceLevel.lowerTo(Confidence::CL_Risky);
926 }
927
928 // Find out which qualifiers we have to use in the loop range.
929 TraversalKindScope RAII(*Context, TK_AsIs);
930 const UsageResult &Usages = Finder.getUsages();
931 determineRangeDescriptor(Context, Nodes, Loop, FixerKind, ContainerExpr,
932 Usages, Descriptor);
933
934 // Ensure that we do not try to move an expression dependent on a local
935 // variable declared inside the loop outside of it.
936 // FIXME: Determine when the external dependency isn't an expression converted
937 // by another loop.
938 TUInfo->getParentFinder().gatherAncestors(*Context);
939 DependencyFinderASTVisitor DependencyFinder(
940 &TUInfo->getParentFinder().getStmtToParentStmtMap(),
941 &TUInfo->getParentFinder().getDeclToParentStmtMap(),
942 &TUInfo->getReplacedVars(), Loop);
943
944 if (DependencyFinder.dependsOnInsideVariable(ContainerExpr) ||
945 Descriptor.ContainerString.empty() || Usages.empty() ||
946 ConfidenceLevel.getLevel() < MinConfidence)
947 return;
948
949 doConversion(Context, LoopVar, getReferencedVariable(ContainerExpr), Usages,
950 Finder.getAliasDecl(), Finder.aliasUseRequired(),
951 Finder.aliasFromForInit(), Loop, Descriptor);
952}
953
954llvm::StringRef LoopConvertCheck::getReverseFunction() const {
955 if (!ReverseFunction.empty())
956 return ReverseFunction;
957 if (UseReverseRanges)
958 return "std::ranges::reverse_view";
959 return "";
960}
961
962llvm::StringRef LoopConvertCheck::getReverseHeader() const {
963 if (!ReverseHeader.empty())
964 return ReverseHeader;
965 if (UseReverseRanges && ReverseFunction.empty()) {
966 return "<ranges>";
967 }
968 return "";
969}
970
971} // namespace modernize
972} // namespace clang::tidy
const Expr * E
const char Usage[]
size_t Offset
NodeType Type
CharSourceRange Range
SourceRange for the file name.
Token Name
std::string Output
Definition: TraceTests.cpp:159
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.
Base class for all clang-tidy checks.
DiagnosticBuilder diag(SourceLocation Loc, StringRef Description, DiagnosticIDs::Level Level=DiagnosticIDs::Warning)
Add a diagnostic with the check's name.
DiagnosticBuilder configurationDiag(StringRef Description, DiagnosticIDs::Level Level=DiagnosticIDs::Warning) const
Adds a diagnostic to report errors in the check's configuration.
bool areDiagsSelfContained() const
Returns true when the check is run in a use case when only 1 fix will be applied at a time.
const LangOptions & getLangOpts() const
Returns the language options from the context.
Every ClangTidyCheck reports errors through a DiagnosticsEngine provided by this context.
Class used to find the variables and member expressions on which an arbitrary expression depends.
void findExprComponents(const clang::Expr *SourceExpr)
Find the components of an expression and place them in a ComponentVector.
const ComponentVector & getComponents()
Accessor for Components.
A class to encapsulate lowering of the tool's confidence level.
Level getLevel() const
Return the internal confidence level.
void lowerTo(Confidence::Level Level)
Lower the internal confidence level to Level, but do not raise it.
Class used to determine if an expression is dependent on a variable declared inside of the loop where...
bool dependsOnInsideVariable(const clang::Stmt *Body)
Run the analysis on Body, and return true iff the expression depends on some variable declared within...
Discover usages of expressions consisting of index or iterator access.
void registerPPCallbacks(const SourceManager &SM, Preprocessor *PP, Preprocessor *ModuleExpanderPP) override
Override this to register PPCallbacks in the preprocessor.
void storeOptions(ClangTidyOptions::OptionMap &Opts) override
Should store all options supported by this check with their current values or default values for opti...
void check(const ast_matchers::MatchFinder::MatchResult &Result) override
ClangTidyChecks that register ASTMatchers should do the actual work in here.
void registerMatchers(ast_matchers::MatchFinder *Finder) override
Override this to register AST matchers with Finder.
Create names for generated variables within a particular statement.
void registerPreprocessor(Preprocessor *PP)
Registers this with the Preprocessor PP, must be called before this class is used.
std::optional< FixItHint > createIncludeInsertion(FileID FileID, llvm::StringRef Header)
Creates a Header inclusion directive fixit in the File FileID.
IncludeSorter::IncludeStyle getStyle() const
static const StatementMatcher incrementVarMatcher()
static const char EndCallName[]
static StringRef getStringFromRange(SourceManager &SourceMgr, const LangOptions &LangOpts, SourceRange Range)
Obtain the original source code text from a SourceRange.
static bool empty(SourceRange Range)
static const DeclarationMatcher initToZeroMatcher()
static const char DerefByValueResultName[]
static bool canBeModified(ASTContext *Context, const Expr *E)
Given an expression that represents an usage of an element from the containter that we are iterating ...
static const char LoopNamePseudoArray[]
static const char BeginCallName[]
static const char ConditionBoundName[]
const DeclRefExpr * getDeclRef(const Expr *E)
Returns the DeclRefExpr represented by E, or NULL if there isn't one.
static const Expr * getContainerFromBeginEndCall(const Expr *Init, bool IsBegin, bool *IsArrow, bool IsReverse)
Determine whether Init appears to be an initializing an iterator.
static bool usagesReturnRValues(const UsageResult &Usages)
Returns true if the elements of the container are never accessed by reference.
static const ValueDecl * getReferencedVariable(const Expr *E)
If the given expression is actually a DeclRefExpr or a MemberExpr, find and return the underlying Val...
StatementMatcher makeArrayLoopMatcher()
The matcher for loops over arrays.
const Expr * digThroughConstructorsConversions(const Expr *E)
Look through conversion/copy constructors and member functions to find the explicit initialization ex...
static const char DerefByRefResultName[]
static bool containerIsConst(const Expr *ContainerExpr, bool Dereference)
Returns true if the container is const-qualified.
static const Expr * findContainer(ASTContext *Context, const Expr *BeginExpr, const Expr *EndExpr, bool *ContainerNeedsDereference, bool IsReverse)
Determines the container whose begin() and end() functions are called for an iterator-based loop.
static const char LoopNameIterator[]
static const StatementMatcher integerComparisonMatcher()
llvm::SmallVector< Usage, 8 > UsageResult
static const char InitVarName[]
bool areSameExpr(ASTContext *Context, const Expr *First, const Expr *Second)
Returns true when two Exprs are equivalent.
static const char EndVarName[]
StatementMatcher makeIteratorLoopMatcher(bool IsReverse)
The matcher used for iterator-based for loops.
static bool isDirectMemberExpr(const Expr *E)
Returns true when the given expression is a member expression whose base is this (implicitly or not).
static const char LoopNameReverseIterator[]
static const char LoopNameArray[]
static bool usagesAreConst(ASTContext *Context, const UsageResult &Usages)
Returns true when it can be guaranteed that the elements of the container are not being modified.
static StatementMatcher arrayConditionMatcher(internal::Matcher< Expr > LimitExpr)
StatementMatcher makePseudoArrayLoopMatcher()
The matcher used for array-like containers (pseudoarrays).
Some operations such as code completion produce a set of candidates.
llvm::StringMap< ClangTidyValue > OptionMap
static llvm::ArrayRef< std::pair< modernize::Confidence::Level, StringRef > > getEnumMapping()
static llvm::ArrayRef< std::pair< modernize::VariableNamer::NamingStyle, StringRef > > getEnumMapping()
This class should be specialized by any enum type that needs to be converted to and from an llvm::Str...
The information needed to describe a valid convertible usage of an array index or iterator.