1 //===-- SimplifyBooleanExprCheck.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 "SimplifyBooleanExprCheck.h"
10 #include "clang/AST/RecursiveASTVisitor.h"
11 #include "clang/Lex/Lexer.h"
12 
13 #include <cassert>
14 #include <string>
15 #include <utility>
16 
17 using namespace clang::ast_matchers;
18 
19 namespace clang {
20 namespace tidy {
21 namespace readability {
22 
23 namespace {
24 
25 StringRef getText(const MatchFinder::MatchResult &Result, SourceRange Range) {
26   return Lexer::getSourceText(CharSourceRange::getTokenRange(Range),
27                               *Result.SourceManager,
28                               Result.Context->getLangOpts());
29 }
30 
31 template <typename T>
32 StringRef getText(const MatchFinder::MatchResult &Result, T &Node) {
33   return getText(Result, Node.getSourceRange());
34 }
35 
36 const char ConditionThenStmtId[] = "if-bool-yields-then";
37 const char ConditionElseStmtId[] = "if-bool-yields-else";
38 const char TernaryId[] = "ternary-bool-yields-condition";
39 const char TernaryNegatedId[] = "ternary-bool-yields-not-condition";
40 const char IfReturnsBoolId[] = "if-return";
41 const char IfReturnsNotBoolId[] = "if-not-return";
42 const char ThenLiteralId[] = "then-literal";
43 const char IfAssignVariableId[] = "if-assign-lvalue";
44 const char IfAssignLocId[] = "if-assign-loc";
45 const char IfAssignBoolId[] = "if-assign";
46 const char IfAssignNotBoolId[] = "if-assign-not";
47 const char IfAssignVarId[] = "if-assign-var";
48 const char CompoundReturnId[] = "compound-return";
49 const char CompoundBoolId[] = "compound-bool";
50 const char CompoundNotBoolId[] = "compound-bool-not";
51 
52 const char IfStmtId[] = "if";
53 
54 const char SimplifyOperatorDiagnostic[] =
55     "redundant boolean literal supplied to boolean operator";
56 const char SimplifyConditionDiagnostic[] =
57     "redundant boolean literal in if statement condition";
58 const char SimplifyConditionalReturnDiagnostic[] =
59     "redundant boolean literal in conditional return statement";
60 
61 const CXXBoolLiteralExpr *getBoolLiteral(const MatchFinder::MatchResult &Result,
62                                          StringRef Id) {
63   const auto *Literal = Result.Nodes.getNodeAs<CXXBoolLiteralExpr>(Id);
64   return (Literal && Literal->getBeginLoc().isMacroID()) ? nullptr : Literal;
65 }
66 
67 internal::Matcher<Stmt> returnsBool(bool Value, StringRef Id = "ignored") {
68   auto SimpleReturnsBool =
69       returnStmt(has(cxxBoolLiteral(equals(Value)).bind(Id)))
70           .bind("returns-bool");
71   return anyOf(SimpleReturnsBool,
72                compoundStmt(statementCountIs(1), has(SimpleReturnsBool)));
73 }
74 
75 bool needsParensAfterUnaryNegation(const Expr *E) {
76   E = E->IgnoreImpCasts();
77   if (isa<BinaryOperator>(E) || isa<ConditionalOperator>(E))
78     return true;
79 
80   if (const auto *Op = dyn_cast<CXXOperatorCallExpr>(E))
81     return Op->getNumArgs() == 2 && Op->getOperator() != OO_Call &&
82            Op->getOperator() != OO_Subscript;
83 
84   return false;
85 }
86 
87 std::pair<BinaryOperatorKind, BinaryOperatorKind> Opposites[] = {
88     {BO_LT, BO_GE}, {BO_GT, BO_LE}, {BO_EQ, BO_NE}};
89 
90 StringRef negatedOperator(const BinaryOperator *BinOp) {
91   const BinaryOperatorKind Opcode = BinOp->getOpcode();
92   for (auto NegatableOp : Opposites) {
93     if (Opcode == NegatableOp.first)
94       return BinOp->getOpcodeStr(NegatableOp.second);
95     if (Opcode == NegatableOp.second)
96       return BinOp->getOpcodeStr(NegatableOp.first);
97   }
98   return StringRef();
99 }
100 
101 std::pair<OverloadedOperatorKind, StringRef> OperatorNames[] = {
102     {OO_EqualEqual, "=="},   {OO_ExclaimEqual, "!="}, {OO_Less, "<"},
103     {OO_GreaterEqual, ">="}, {OO_Greater, ">"},       {OO_LessEqual, "<="}};
104 
105 StringRef getOperatorName(OverloadedOperatorKind OpKind) {
106   for (auto Name : OperatorNames) {
107     if (Name.first == OpKind)
108       return Name.second;
109   }
110 
111   return StringRef();
112 }
113 
114 std::pair<OverloadedOperatorKind, OverloadedOperatorKind> OppositeOverloads[] =
115     {{OO_EqualEqual, OO_ExclaimEqual},
116      {OO_Less, OO_GreaterEqual},
117      {OO_Greater, OO_LessEqual}};
118 
119 StringRef negatedOperator(const CXXOperatorCallExpr *OpCall) {
120   const OverloadedOperatorKind Opcode = OpCall->getOperator();
121   for (auto NegatableOp : OppositeOverloads) {
122     if (Opcode == NegatableOp.first)
123       return getOperatorName(NegatableOp.second);
124     if (Opcode == NegatableOp.second)
125       return getOperatorName(NegatableOp.first);
126   }
127   return StringRef();
128 }
129 
130 std::string asBool(StringRef text, bool NeedsStaticCast) {
131   if (NeedsStaticCast)
132     return ("static_cast<bool>(" + text + ")").str();
133 
134   return text;
135 }
136 
137 bool needsNullPtrComparison(const Expr *E) {
138   if (const auto *ImpCast = dyn_cast<ImplicitCastExpr>(E))
139     return ImpCast->getCastKind() == CK_PointerToBoolean ||
140            ImpCast->getCastKind() == CK_MemberPointerToBoolean;
141 
142   return false;
143 }
144 
145 bool needsZeroComparison(const Expr *E) {
146   if (const auto *ImpCast = dyn_cast<ImplicitCastExpr>(E))
147     return ImpCast->getCastKind() == CK_IntegralToBoolean;
148 
149   return false;
150 }
151 
152 bool needsStaticCast(const Expr *E) {
153   if (const auto *ImpCast = dyn_cast<ImplicitCastExpr>(E)) {
154     if (ImpCast->getCastKind() == CK_UserDefinedConversion &&
155         ImpCast->getSubExpr()->getType()->isBooleanType()) {
156       if (const auto *MemCall =
157               dyn_cast<CXXMemberCallExpr>(ImpCast->getSubExpr())) {
158         if (const auto *MemDecl =
159                 dyn_cast<CXXConversionDecl>(MemCall->getMethodDecl())) {
160           if (MemDecl->isExplicit())
161             return true;
162         }
163       }
164     }
165   }
166 
167   E = E->IgnoreImpCasts();
168   return !E->getType()->isBooleanType();
169 }
170 
171 std::string compareExpressionToConstant(const MatchFinder::MatchResult &Result,
172                                         const Expr *E, bool Negated,
173                                         const char *Constant) {
174   E = E->IgnoreImpCasts();
175   const std::string ExprText =
176       (isa<BinaryOperator>(E) ? ("(" + getText(Result, *E) + ")")
177                               : getText(Result, *E))
178           .str();
179   return ExprText + " " + (Negated ? "!=" : "==") + " " + Constant;
180 }
181 
182 std::string compareExpressionToNullPtr(const MatchFinder::MatchResult &Result,
183                                        const Expr *E, bool Negated) {
184   const char *NullPtr =
185       Result.Context->getLangOpts().CPlusPlus11 ? "nullptr" : "NULL";
186   return compareExpressionToConstant(Result, E, Negated, NullPtr);
187 }
188 
189 std::string compareExpressionToZero(const MatchFinder::MatchResult &Result,
190                                     const Expr *E, bool Negated) {
191   return compareExpressionToConstant(Result, E, Negated, "0");
192 }
193 
194 std::string replacementExpression(const MatchFinder::MatchResult &Result,
195                                   bool Negated, const Expr *E) {
196   E = E->ignoreParenBaseCasts();
197   if (const auto *EC = dyn_cast<ExprWithCleanups>(E))
198     E = EC->getSubExpr();
199 
200   const bool NeedsStaticCast = needsStaticCast(E);
201   if (Negated) {
202     if (const auto *UnOp = dyn_cast<UnaryOperator>(E)) {
203       if (UnOp->getOpcode() == UO_LNot) {
204         if (needsNullPtrComparison(UnOp->getSubExpr()))
205           return compareExpressionToNullPtr(Result, UnOp->getSubExpr(), true);
206 
207         if (needsZeroComparison(UnOp->getSubExpr()))
208           return compareExpressionToZero(Result, UnOp->getSubExpr(), true);
209 
210         return replacementExpression(Result, false, UnOp->getSubExpr());
211       }
212     }
213 
214     if (needsNullPtrComparison(E))
215       return compareExpressionToNullPtr(Result, E, false);
216 
217     if (needsZeroComparison(E))
218       return compareExpressionToZero(Result, E, false);
219 
220     StringRef NegatedOperator;
221     const Expr *LHS = nullptr;
222     const Expr *RHS = nullptr;
223     if (const auto *BinOp = dyn_cast<BinaryOperator>(E)) {
224       NegatedOperator = negatedOperator(BinOp);
225       LHS = BinOp->getLHS();
226       RHS = BinOp->getRHS();
227     } else if (const auto *OpExpr = dyn_cast<CXXOperatorCallExpr>(E)) {
228       if (OpExpr->getNumArgs() == 2) {
229         NegatedOperator = negatedOperator(OpExpr);
230         LHS = OpExpr->getArg(0);
231         RHS = OpExpr->getArg(1);
232       }
233     }
234     if (!NegatedOperator.empty() && LHS && RHS)
235       return (asBool((getText(Result, *LHS) + " " + NegatedOperator + " " +
236                       getText(Result, *RHS))
237                          .str(),
238                      NeedsStaticCast));
239 
240     StringRef Text = getText(Result, *E);
241     if (!NeedsStaticCast && needsParensAfterUnaryNegation(E))
242       return ("!(" + Text + ")").str();
243 
244     if (needsNullPtrComparison(E))
245       return compareExpressionToNullPtr(Result, E, false);
246 
247     if (needsZeroComparison(E))
248       return compareExpressionToZero(Result, E, false);
249 
250     return ("!" + asBool(Text, NeedsStaticCast));
251   }
252 
253   if (const auto *UnOp = dyn_cast<UnaryOperator>(E)) {
254     if (UnOp->getOpcode() == UO_LNot) {
255       if (needsNullPtrComparison(UnOp->getSubExpr()))
256         return compareExpressionToNullPtr(Result, UnOp->getSubExpr(), false);
257 
258       if (needsZeroComparison(UnOp->getSubExpr()))
259         return compareExpressionToZero(Result, UnOp->getSubExpr(), false);
260     }
261   }
262 
263   if (needsNullPtrComparison(E))
264     return compareExpressionToNullPtr(Result, E, true);
265 
266   if (needsZeroComparison(E))
267     return compareExpressionToZero(Result, E, true);
268 
269   return asBool(getText(Result, *E), NeedsStaticCast);
270 }
271 
272 const CXXBoolLiteralExpr *stmtReturnsBool(const ReturnStmt *Ret, bool Negated) {
273   if (const auto *Bool = dyn_cast<CXXBoolLiteralExpr>(Ret->getRetValue())) {
274     if (Bool->getValue() == !Negated)
275       return Bool;
276   }
277 
278   return nullptr;
279 }
280 
281 const CXXBoolLiteralExpr *stmtReturnsBool(const IfStmt *IfRet, bool Negated) {
282   if (IfRet->getElse() != nullptr)
283     return nullptr;
284 
285   if (const auto *Ret = dyn_cast<ReturnStmt>(IfRet->getThen()))
286     return stmtReturnsBool(Ret, Negated);
287 
288   if (const auto *Compound = dyn_cast<CompoundStmt>(IfRet->getThen())) {
289     if (Compound->size() == 1) {
290       if (const auto *CompoundRet = dyn_cast<ReturnStmt>(Compound->body_back()))
291         return stmtReturnsBool(CompoundRet, Negated);
292     }
293   }
294 
295   return nullptr;
296 }
297 
298 bool containsDiscardedTokens(const MatchFinder::MatchResult &Result,
299                              CharSourceRange CharRange) {
300   std::string ReplacementText =
301       Lexer::getSourceText(CharRange, *Result.SourceManager,
302                            Result.Context->getLangOpts())
303           .str();
304   Lexer Lex(CharRange.getBegin(), Result.Context->getLangOpts(),
305             ReplacementText.data(), ReplacementText.data(),
306             ReplacementText.data() + ReplacementText.size());
307   Lex.SetCommentRetentionState(true);
308 
309   Token Tok;
310   while (!Lex.LexFromRawLexer(Tok)) {
311     if (Tok.is(tok::TokenKind::comment) || Tok.is(tok::TokenKind::hash))
312       return true;
313   }
314 
315   return false;
316 }
317 
318 } // namespace
319 
320 class SimplifyBooleanExprCheck::Visitor : public RecursiveASTVisitor<Visitor> {
321  public:
322   Visitor(SimplifyBooleanExprCheck *Check,
323           const MatchFinder::MatchResult &Result)
324       : Check(Check), Result(Result) {}
325 
326   bool VisitBinaryOperator(BinaryOperator *Op) {
327     Check->reportBinOp(Result, Op);
328     return true;
329   }
330 
331  private:
332   SimplifyBooleanExprCheck *Check;
333   const MatchFinder::MatchResult &Result;
334 };
335 
336 
337 SimplifyBooleanExprCheck::SimplifyBooleanExprCheck(StringRef Name,
338                                                    ClangTidyContext *Context)
339     : ClangTidyCheck(Name, Context),
340       ChainedConditionalReturn(Options.get("ChainedConditionalReturn", 0U)),
341       ChainedConditionalAssignment(
342           Options.get("ChainedConditionalAssignment", 0U)) {}
343 
344 bool containsBoolLiteral(const Expr *E) {
345   if (!E)
346     return false;
347   E = E->IgnoreParenImpCasts();
348   if (isa<CXXBoolLiteralExpr>(E))
349     return true;
350   if (const auto *BinOp = dyn_cast<BinaryOperator>(E))
351     return containsBoolLiteral(BinOp->getLHS()) ||
352            containsBoolLiteral(BinOp->getRHS());
353   if (const auto *UnaryOp = dyn_cast<UnaryOperator>(E))
354     return containsBoolLiteral(UnaryOp->getSubExpr());
355   return false;
356 }
357 
358 void SimplifyBooleanExprCheck::reportBinOp(
359     const MatchFinder::MatchResult &Result, const BinaryOperator *Op) {
360   const auto *LHS = Op->getLHS()->IgnoreParenImpCasts();
361   const auto *RHS = Op->getRHS()->IgnoreParenImpCasts();
362 
363   const CXXBoolLiteralExpr *Bool;
364   const Expr *Other = nullptr;
365   if ((Bool = dyn_cast<CXXBoolLiteralExpr>(LHS)))
366     Other = RHS;
367   else if ((Bool = dyn_cast<CXXBoolLiteralExpr>(RHS)))
368     Other = LHS;
369   else
370     return;
371 
372   if (Bool->getBeginLoc().isMacroID())
373     return;
374 
375   // FIXME: why do we need this?
376   if (!isa<CXXBoolLiteralExpr>(Other) && containsBoolLiteral(Other))
377     return;
378 
379   bool BoolValue = Bool->getValue();
380 
381   auto replaceWithExpression = [this, &Result, LHS, RHS, Bool](
382                                    const Expr *ReplaceWith, bool Negated) {
383     std::string Replacement =
384         replacementExpression(Result, Negated, ReplaceWith);
385     SourceRange Range(LHS->getBeginLoc(), RHS->getEndLoc());
386     issueDiag(Result, Bool->getBeginLoc(), SimplifyOperatorDiagnostic, Range,
387               Replacement);
388   };
389 
390   switch (Op->getOpcode()) {
391     case BO_LAnd:
392       if (BoolValue) {
393         // expr && true -> expr
394         replaceWithExpression(Other, /*Negated=*/false);
395       } else {
396         // expr && false -> false
397         replaceWithExpression(Bool, /*Negated=*/false);
398       }
399       break;
400     case BO_LOr:
401       if (BoolValue) {
402         // expr || true -> true
403         replaceWithExpression(Bool, /*Negated=*/false);
404       } else {
405         // expr || false -> expr
406         replaceWithExpression(Other, /*Negated=*/false);
407       }
408       break;
409     case BO_EQ:
410       // expr == true -> expr, expr == false -> !expr
411       replaceWithExpression(Other, /*Negated=*/!BoolValue);
412       break;
413     case BO_NE:
414       // expr != true -> !expr, expr != false -> expr
415       replaceWithExpression(Other, /*Negated=*/BoolValue);
416       break;
417     default:
418       break;
419   }
420 }
421 
422 void SimplifyBooleanExprCheck::matchBoolCondition(MatchFinder *Finder,
423                                                   bool Value,
424                                                   StringRef BooleanId) {
425   Finder->addMatcher(
426       ifStmt(isExpansionInMainFile(),
427              hasCondition(cxxBoolLiteral(equals(Value)).bind(BooleanId)))
428           .bind(IfStmtId),
429       this);
430 }
431 
432 void SimplifyBooleanExprCheck::matchTernaryResult(MatchFinder *Finder,
433                                                   bool Value,
434                                                   StringRef TernaryId) {
435   Finder->addMatcher(
436       conditionalOperator(isExpansionInMainFile(),
437                           hasTrueExpression(cxxBoolLiteral(equals(Value))),
438                           hasFalseExpression(cxxBoolLiteral(equals(!Value))))
439           .bind(TernaryId),
440       this);
441 }
442 
443 void SimplifyBooleanExprCheck::matchIfReturnsBool(MatchFinder *Finder,
444                                                   bool Value, StringRef Id) {
445   if (ChainedConditionalReturn)
446     Finder->addMatcher(ifStmt(isExpansionInMainFile(),
447                               hasThen(returnsBool(Value, ThenLiteralId)),
448                               hasElse(returnsBool(!Value)))
449                            .bind(Id),
450                        this);
451   else
452     Finder->addMatcher(ifStmt(isExpansionInMainFile(),
453                               unless(hasParent(ifStmt())),
454                               hasThen(returnsBool(Value, ThenLiteralId)),
455                               hasElse(returnsBool(!Value)))
456                            .bind(Id),
457                        this);
458 }
459 
460 void SimplifyBooleanExprCheck::matchIfAssignsBool(MatchFinder *Finder,
461                                                   bool Value, StringRef Id) {
462   auto VarAssign = declRefExpr(hasDeclaration(decl().bind(IfAssignVarId)));
463   auto VarRef = declRefExpr(hasDeclaration(equalsBoundNode(IfAssignVarId)));
464   auto MemAssign = memberExpr(hasDeclaration(decl().bind(IfAssignVarId)));
465   auto MemRef = memberExpr(hasDeclaration(equalsBoundNode(IfAssignVarId)));
466   auto SimpleThen =
467       binaryOperator(hasOperatorName("="), hasLHS(anyOf(VarAssign, MemAssign)),
468                      hasLHS(expr().bind(IfAssignVariableId)),
469                      hasRHS(cxxBoolLiteral(equals(Value)).bind(IfAssignLocId)));
470   auto Then = anyOf(SimpleThen, compoundStmt(statementCountIs(1),
471                                              hasAnySubstatement(SimpleThen)));
472   auto SimpleElse =
473       binaryOperator(hasOperatorName("="), hasLHS(anyOf(VarRef, MemRef)),
474                      hasRHS(cxxBoolLiteral(equals(!Value))));
475   auto Else = anyOf(SimpleElse, compoundStmt(statementCountIs(1),
476                                              hasAnySubstatement(SimpleElse)));
477   if (ChainedConditionalAssignment)
478     Finder->addMatcher(ifStmt(hasThen(Then), hasElse(Else)).bind(Id), this);
479   else
480     Finder->addMatcher(
481         ifStmt(unless(hasParent(ifStmt())), hasThen(Then), hasElse(Else))
482             .bind(Id),
483         this);
484 }
485 
486 void SimplifyBooleanExprCheck::matchCompoundIfReturnsBool(MatchFinder *Finder,
487                                                           bool Value,
488                                                           StringRef Id) {
489   Finder->addMatcher(
490       compoundStmt(
491           hasAnySubstatement(
492               ifStmt(hasThen(returnsBool(Value)), unless(hasElse(stmt())))),
493           hasAnySubstatement(returnStmt(has(ignoringParenImpCasts(
494                                             cxxBoolLiteral(equals(!Value)))))
495                                  .bind(CompoundReturnId)))
496           .bind(Id),
497       this);
498 }
499 
500 void SimplifyBooleanExprCheck::storeOptions(ClangTidyOptions::OptionMap &Opts) {
501   Options.store(Opts, "ChainedConditionalReturn", ChainedConditionalReturn);
502   Options.store(Opts, "ChainedConditionalAssignment",
503                 ChainedConditionalAssignment);
504 }
505 
506 void SimplifyBooleanExprCheck::registerMatchers(MatchFinder *Finder) {
507   Finder->addMatcher(translationUnitDecl().bind("top"), this);
508 
509   matchBoolCondition(Finder, true, ConditionThenStmtId);
510   matchBoolCondition(Finder, false, ConditionElseStmtId);
511 
512   matchTernaryResult(Finder, true, TernaryId);
513   matchTernaryResult(Finder, false, TernaryNegatedId);
514 
515   matchIfReturnsBool(Finder, true, IfReturnsBoolId);
516   matchIfReturnsBool(Finder, false, IfReturnsNotBoolId);
517 
518   matchIfAssignsBool(Finder, true, IfAssignBoolId);
519   matchIfAssignsBool(Finder, false, IfAssignNotBoolId);
520 
521   matchCompoundIfReturnsBool(Finder, true, CompoundBoolId);
522   matchCompoundIfReturnsBool(Finder, false, CompoundNotBoolId);
523 }
524 
525 void SimplifyBooleanExprCheck::check(const MatchFinder::MatchResult &Result) {
526   if (Result.Nodes.getNodeAs<TranslationUnitDecl>("top"))
527     Visitor(this, Result).TraverseAST(*Result.Context);
528   else if (const CXXBoolLiteralExpr *TrueConditionRemoved =
529                getBoolLiteral(Result, ConditionThenStmtId))
530     replaceWithThenStatement(Result, TrueConditionRemoved);
531   else if (const CXXBoolLiteralExpr *FalseConditionRemoved =
532                getBoolLiteral(Result, ConditionElseStmtId))
533     replaceWithElseStatement(Result, FalseConditionRemoved);
534   else if (const auto *Ternary =
535                Result.Nodes.getNodeAs<ConditionalOperator>(TernaryId))
536     replaceWithCondition(Result, Ternary);
537   else if (const auto *TernaryNegated =
538                Result.Nodes.getNodeAs<ConditionalOperator>(TernaryNegatedId))
539     replaceWithCondition(Result, TernaryNegated, true);
540   else if (const auto *If = Result.Nodes.getNodeAs<IfStmt>(IfReturnsBoolId))
541     replaceWithReturnCondition(Result, If);
542   else if (const auto *IfNot =
543                Result.Nodes.getNodeAs<IfStmt>(IfReturnsNotBoolId))
544     replaceWithReturnCondition(Result, IfNot, true);
545   else if (const auto *IfAssign =
546                Result.Nodes.getNodeAs<IfStmt>(IfAssignBoolId))
547     replaceWithAssignment(Result, IfAssign);
548   else if (const auto *IfAssignNot =
549                Result.Nodes.getNodeAs<IfStmt>(IfAssignNotBoolId))
550     replaceWithAssignment(Result, IfAssignNot, true);
551   else if (const auto *Compound =
552                Result.Nodes.getNodeAs<CompoundStmt>(CompoundBoolId))
553     replaceCompoundReturnWithCondition(Result, Compound);
554   else if (const auto *Compound =
555                Result.Nodes.getNodeAs<CompoundStmt>(CompoundNotBoolId))
556     replaceCompoundReturnWithCondition(Result, Compound, true);
557 }
558 
559 void SimplifyBooleanExprCheck::issueDiag(
560     const ast_matchers::MatchFinder::MatchResult &Result, SourceLocation Loc,
561     StringRef Description, SourceRange ReplacementRange,
562     StringRef Replacement) {
563   CharSourceRange CharRange =
564       Lexer::makeFileCharRange(CharSourceRange::getTokenRange(ReplacementRange),
565                                *Result.SourceManager, getLangOpts());
566 
567   DiagnosticBuilder Diag = diag(Loc, Description);
568   if (!containsDiscardedTokens(Result, CharRange))
569     Diag << FixItHint::CreateReplacement(CharRange, Replacement);
570 }
571 
572 void SimplifyBooleanExprCheck::replaceWithThenStatement(
573     const MatchFinder::MatchResult &Result,
574     const CXXBoolLiteralExpr *TrueConditionRemoved) {
575   const auto *IfStatement = Result.Nodes.getNodeAs<IfStmt>(IfStmtId);
576   issueDiag(Result, TrueConditionRemoved->getBeginLoc(),
577             SimplifyConditionDiagnostic, IfStatement->getSourceRange(),
578             getText(Result, *IfStatement->getThen()));
579 }
580 
581 void SimplifyBooleanExprCheck::replaceWithElseStatement(
582     const MatchFinder::MatchResult &Result,
583     const CXXBoolLiteralExpr *FalseConditionRemoved) {
584   const auto *IfStatement = Result.Nodes.getNodeAs<IfStmt>(IfStmtId);
585   const Stmt *ElseStatement = IfStatement->getElse();
586   issueDiag(Result, FalseConditionRemoved->getBeginLoc(),
587             SimplifyConditionDiagnostic, IfStatement->getSourceRange(),
588             ElseStatement ? getText(Result, *ElseStatement) : "");
589 }
590 
591 void SimplifyBooleanExprCheck::replaceWithCondition(
592     const MatchFinder::MatchResult &Result, const ConditionalOperator *Ternary,
593     bool Negated) {
594   std::string Replacement =
595       replacementExpression(Result, Negated, Ternary->getCond());
596   issueDiag(Result, Ternary->getTrueExpr()->getBeginLoc(),
597             "redundant boolean literal in ternary expression result",
598             Ternary->getSourceRange(), Replacement);
599 }
600 
601 void SimplifyBooleanExprCheck::replaceWithReturnCondition(
602     const MatchFinder::MatchResult &Result, const IfStmt *If, bool Negated) {
603   StringRef Terminator = isa<CompoundStmt>(If->getElse()) ? ";" : "";
604   std::string Condition = replacementExpression(Result, Negated, If->getCond());
605   std::string Replacement = ("return " + Condition + Terminator).str();
606   SourceLocation Start =
607       Result.Nodes.getNodeAs<CXXBoolLiteralExpr>(ThenLiteralId)->getBeginLoc();
608   issueDiag(Result, Start, SimplifyConditionalReturnDiagnostic,
609             If->getSourceRange(), Replacement);
610 }
611 
612 void SimplifyBooleanExprCheck::replaceCompoundReturnWithCondition(
613     const MatchFinder::MatchResult &Result, const CompoundStmt *Compound,
614     bool Negated) {
615   const auto *Ret = Result.Nodes.getNodeAs<ReturnStmt>(CompoundReturnId);
616 
617   // The body shouldn't be empty because the matcher ensures that it must
618   // contain at least two statements:
619   // 1) A `return` statement returning a boolean literal `false` or `true`
620   // 2) An `if` statement with no `else` clause that consists of a single
621   //    `return` statement returning the opposite boolean literal `true` or
622   //    `false`.
623   assert(Compound->size() >= 2);
624   const IfStmt *BeforeIf = nullptr;
625   CompoundStmt::const_body_iterator Current = Compound->body_begin();
626   CompoundStmt::const_body_iterator After = Compound->body_begin();
627   for (++After; After != Compound->body_end() && *Current != Ret;
628        ++Current, ++After) {
629     if (const auto *If = dyn_cast<IfStmt>(*Current)) {
630       if (const CXXBoolLiteralExpr *Lit = stmtReturnsBool(If, Negated)) {
631         if (*After == Ret) {
632           if (!ChainedConditionalReturn && BeforeIf)
633             continue;
634 
635           const Expr *Condition = If->getCond();
636           std::string Replacement =
637               "return " + replacementExpression(Result, Negated, Condition);
638           issueDiag(
639               Result, Lit->getBeginLoc(), SimplifyConditionalReturnDiagnostic,
640               SourceRange(If->getBeginLoc(), Ret->getEndLoc()), Replacement);
641           return;
642         }
643 
644         BeforeIf = If;
645       }
646     } else {
647       BeforeIf = nullptr;
648     }
649   }
650 }
651 
652 void SimplifyBooleanExprCheck::replaceWithAssignment(
653     const MatchFinder::MatchResult &Result, const IfStmt *IfAssign,
654     bool Negated) {
655   SourceRange Range = IfAssign->getSourceRange();
656   StringRef VariableName =
657       getText(Result, *Result.Nodes.getNodeAs<Expr>(IfAssignVariableId));
658   StringRef Terminator = isa<CompoundStmt>(IfAssign->getElse()) ? ";" : "";
659   std::string Condition =
660       replacementExpression(Result, Negated, IfAssign->getCond());
661   std::string Replacement =
662       (VariableName + " = " + Condition + Terminator).str();
663   SourceLocation Location =
664       Result.Nodes.getNodeAs<CXXBoolLiteralExpr>(IfAssignLocId)->getBeginLoc();
665   issueDiag(Result, Location,
666             "redundant boolean literal in conditional assignment", Range,
667             Replacement);
668 }
669 
670 } // namespace readability
671 } // namespace tidy
672 } // namespace clang
673