clang-tools-extra/clang-tidy/readability/SimplifyBooleanExprCheck.cpp

//===--- SimplifyBooleanExpr.cpp clang-tidy ---------------------*- C++ -*-===//
//
//                     The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//

#include "SimplifyBooleanExprCheck.h"
#include "clang/Lex/Lexer.h"

#include <cassert>
#include <string>
#include <utility>

using namespace clang::ast_matchers;

namespace clang {
namespace tidy {
namespace readability {

namespace {

StringRef getText(const MatchFinder::MatchResult &Result, SourceRange Range) {
  return Lexer::getSourceText(CharSourceRange::getTokenRange(Range),
                              *Result.SourceManager,
                              Result.Context->getLangOpts());
}

template <typename T>
StringRef getText(const MatchFinder::MatchResult &Result, T &Node) {
  return getText(Result, Node.getSourceRange());
}

const char RightExpressionId[] = "bool-op-expr-yields-expr";
const char LeftExpressionId[] = "expr-op-bool-yields-expr";
const char NegatedRightExpressionId[] = "bool-op-expr-yields-not-expr";
const char NegatedLeftExpressionId[] = "expr-op-bool-yields-not-expr";
const char ConditionThenStmtId[] = "if-bool-yields-then";
const char ConditionElseStmtId[] = "if-bool-yields-else";
const char TernaryId[] = "ternary-bool-yields-condition";
const char TernaryNegatedId[] = "ternary-bool-yields-not-condition";
const char IfReturnsBoolId[] = "if-return";
const char IfReturnsNotBoolId[] = "if-not-return";
const char ThenLiteralId[] = "then-literal";
const char IfAssignVariableId[] = "if-assign-lvalue";
const char IfAssignLocId[] = "if-assign-loc";
const char IfAssignBoolId[] = "if-assign";
const char IfAssignNotBoolId[] = "if-assign-not";
const char IfAssignObjId[] = "if-assign-obj";
const char CompoundReturnId[] = "compound-return";
const char CompoundBoolId[] = "compound-bool";
const char CompoundNotBoolId[] = "compound-bool-not";

const char IfStmtId[] = "if";
const char LHSId[] = "lhs-expr";
const char RHSId[] = "rhs-expr";

const char SimplifyOperatorDiagnostic[] =
    "redundant boolean literal supplied to boolean operator";
const char SimplifyConditionDiagnostic[] =
    "redundant boolean literal in if statement condition";
const char SimplifyConditionalReturnDiagnostic[] =
    "redundant boolean literal in conditional return statement";

const CXXBoolLiteralExpr *getBoolLiteral(const MatchFinder::MatchResult &Result,
                                         StringRef Id) {
  const auto *Literal = Result.Nodes.getNodeAs<CXXBoolLiteralExpr>(Id);
  return (Literal &&
          Result.SourceManager->isMacroBodyExpansion(Literal->getLocStart()))
             ? nullptr
             : Literal;
}

internal::Matcher<Stmt> returnsBool(bool Value, StringRef Id = "ignored") {
  auto SimpleReturnsBool =
      returnStmt(has(cxxBoolLiteral(equals(Value)).bind(Id)))
          .bind("returns-bool");
  return anyOf(SimpleReturnsBool,
               compoundStmt(statementCountIs(1), has(SimpleReturnsBool)));
}

bool needsParensAfterUnaryNegation(const Expr *E) {
  E = E->IgnoreImpCasts();
  if (isa<BinaryOperator>(E) || isa<ConditionalOperator>(E))
    return true;
  if (const auto *Op = dyn_cast<CXXOperatorCallExpr>(E)) {
    return Op->getNumArgs() == 2 && Op->getOperator() != OO_Call &&
           Op->getOperator() != OO_Subscript;
  }
  return false;
}

std::pair<BinaryOperatorKind, BinaryOperatorKind> Opposites[] = {
    {BO_LT, BO_GE}, {BO_GT, BO_LE}, {BO_EQ, BO_NE}};

StringRef negatedOperator(const BinaryOperator *BinOp) {
  const BinaryOperatorKind Opcode = BinOp->getOpcode();
  for (auto NegatableOp : Opposites) {
    if (Opcode == NegatableOp.first)
      return BinOp->getOpcodeStr(NegatableOp.second);
    if (Opcode == NegatableOp.second)
      return BinOp->getOpcodeStr(NegatableOp.first);
  }
  return StringRef();
}

std::pair<OverloadedOperatorKind, StringRef> OperatorNames[] = {
    {OO_EqualEqual, "=="},   {OO_ExclaimEqual, "!="}, {OO_Less, "<"},
    {OO_GreaterEqual, ">="}, {OO_Greater, ">"},       {OO_LessEqual, "<="}};

StringRef getOperatorName(OverloadedOperatorKind OpKind) {
  for (auto Name : OperatorNames) {
    if (Name.first == OpKind)
      return Name.second;
  }

  return StringRef();
}

std::pair<OverloadedOperatorKind, OverloadedOperatorKind> OppositeOverloads[] =
    {{OO_EqualEqual, OO_ExclaimEqual},
     {OO_Less, OO_GreaterEqual},
     {OO_Greater, OO_LessEqual}};

StringRef negatedOperator(const CXXOperatorCallExpr *OpCall) {
  const OverloadedOperatorKind Opcode = OpCall->getOperator();
  for (auto NegatableOp : OppositeOverloads) {
    if (Opcode == NegatableOp.first)
      return getOperatorName(NegatableOp.second);
    if (Opcode == NegatableOp.second)
      return getOperatorName(NegatableOp.first);
  }
  return StringRef();
}

std::string asBool(StringRef text, bool NeedsStaticCast) {
  if (NeedsStaticCast)
    return ("static_cast<bool>(" + text + ")").str();

  return text;
}

bool needsNullPtrComparison(const Expr *E) {
  if (const auto *ImpCast = dyn_cast<ImplicitCastExpr>(E))
    return ImpCast->getCastKind() == CK_PointerToBoolean;

  return false;
}

bool needsStaticCast(const Expr *E) {
  if (const auto *ImpCast = dyn_cast<ImplicitCastExpr>(E)) {
    if (ImpCast->getCastKind() == CK_UserDefinedConversion &&
        ImpCast->getSubExpr()->getType()->isBooleanType()) {
      if (const auto *MemCall =
              dyn_cast<CXXMemberCallExpr>(ImpCast->getSubExpr())) {
        if (const auto *MemDecl =
                dyn_cast<CXXConversionDecl>(MemCall->getMethodDecl())) {
          if (MemDecl->isExplicit())
            return true;
        }
      }
    }
  }

  E = E->IgnoreImpCasts();
  return !E->getType()->isBooleanType();
}

std::string replacementExpression(const MatchFinder::MatchResult &Result,
                                  bool Negated, const Expr *E) {
  E = E->ignoreParenBaseCasts();
  const bool NeedsStaticCast = needsStaticCast(E);
  if (Negated) {
    if (const auto *UnOp = dyn_cast<UnaryOperator>(E)) {
      if (UnOp->getOpcode() == UO_LNot) {
        if (needsNullPtrComparison(UnOp->getSubExpr()))
          return (getText(Result, *UnOp->getSubExpr()) + " != nullptr").str();

        return replacementExpression(Result, false, UnOp->getSubExpr());
      }
    }

    if (needsNullPtrComparison(E))
      return (getText(Result, *E) + " == nullptr").str();

    StringRef NegatedOperator;
    const Expr *LHS = nullptr;
    const Expr *RHS = nullptr;
    if (const auto *BinOp = dyn_cast<BinaryOperator>(E)) {
      NegatedOperator = negatedOperator(BinOp);
      LHS = BinOp->getLHS();
      RHS = BinOp->getRHS();
    } else if (const auto *OpExpr = dyn_cast<CXXOperatorCallExpr>(E)) {
      if (OpExpr->getNumArgs() == 2) {
        NegatedOperator = negatedOperator(OpExpr);
        LHS = OpExpr->getArg(0);
        RHS = OpExpr->getArg(1);
      }
    }
    if (!NegatedOperator.empty() && LHS && RHS) {
      return (asBool((getText(Result, *LHS) + " " + NegatedOperator + " " +
                      getText(Result, *RHS))
                         .str(),
                     NeedsStaticCast));
    }

    StringRef Text = getText(Result, *E);
    if (!NeedsStaticCast && needsParensAfterUnaryNegation(E))
      return ("!(" + Text + ")").str();

    if (needsNullPtrComparison(E))
      return (getText(Result, *E) + " == nullptr").str();

    return ("!" + asBool(Text, NeedsStaticCast));
  }

  if (const auto *UnOp = dyn_cast<UnaryOperator>(E)) {
    if (UnOp->getOpcode() == UO_LNot) {
      if (needsNullPtrComparison(UnOp->getSubExpr()))
        return (getText(Result, *UnOp->getSubExpr()) + " == nullptr").str();
    }
  }

  if (needsNullPtrComparison(E))
    return (getText(Result, *E) + " != nullptr").str();

  return asBool(getText(Result, *E), NeedsStaticCast);
}

const CXXBoolLiteralExpr *stmtReturnsBool(const ReturnStmt *Ret, bool Negated) {
  if (const auto *Bool = dyn_cast<CXXBoolLiteralExpr>(Ret->getRetValue())) {
    if (Bool->getValue() == !Negated)
      return Bool;
  }

  return nullptr;
}

const CXXBoolLiteralExpr *stmtReturnsBool(const IfStmt *IfRet, bool Negated) {
  if (IfRet->getElse() != nullptr)
    return nullptr;

  if (const auto *Ret = dyn_cast<ReturnStmt>(IfRet->getThen()))
    return stmtReturnsBool(Ret, Negated);

  if (const auto *Compound = dyn_cast<CompoundStmt>(IfRet->getThen())) {
    if (Compound->size() == 1) {
      if (const auto *CompoundRet = dyn_cast<ReturnStmt>(Compound->body_back()))
        return stmtReturnsBool(CompoundRet, Negated);
    }
  }

  return nullptr;
}

} // namespace

SimplifyBooleanExprCheck::SimplifyBooleanExprCheck(StringRef Name,
                                                   ClangTidyContext *Context)
    : ClangTidyCheck(Name, Context),
      ChainedConditionalReturn(Options.get("ChainedConditionalReturn", 0U)),
      ChainedConditionalAssignment(
          Options.get("ChainedConditionalAssignment", 0U)) {}

void SimplifyBooleanExprCheck::matchBoolBinOpExpr(MatchFinder *Finder,
                                                  bool Value,
                                                  StringRef OperatorName,
                                                  StringRef BooleanId) {
  Finder->addMatcher(
      binaryOperator(
          isExpansionInMainFile(), hasOperatorName(OperatorName),
          hasLHS(allOf(expr().bind(LHSId),
                       cxxBoolLiteral(equals(Value)).bind(BooleanId))),
          hasRHS(expr().bind(RHSId)),
          unless(hasRHS(hasDescendant(cxxBoolLiteral())))),
      this);
}

void SimplifyBooleanExprCheck::matchExprBinOpBool(MatchFinder *Finder,
                                                  bool Value,
                                                  StringRef OperatorName,
                                                  StringRef BooleanId) {
  Finder->addMatcher(
      binaryOperator(
          isExpansionInMainFile(), hasOperatorName(OperatorName),
          hasLHS(expr().bind(LHSId)),
          unless(
              hasLHS(anyOf(cxxBoolLiteral(), hasDescendant(cxxBoolLiteral())))),
          hasRHS(allOf(expr().bind(RHSId),
                       cxxBoolLiteral(equals(Value)).bind(BooleanId)))),
      this);
}

void SimplifyBooleanExprCheck::matchBoolCompOpExpr(MatchFinder *Finder,
                                                   bool Value,
                                                   StringRef OperatorName,
                                                   StringRef BooleanId) {
  Finder->addMatcher(
      binaryOperator(isExpansionInMainFile(), hasOperatorName(OperatorName),
                     hasLHS(allOf(expr().bind(LHSId),
                                  ignoringImpCasts(cxxBoolLiteral(equals(Value))
                                                       .bind(BooleanId)))),
                     hasRHS(expr().bind(RHSId)),
                     unless(hasRHS(hasDescendant(cxxBoolLiteral())))),
      this);
}

void SimplifyBooleanExprCheck::matchExprCompOpBool(MatchFinder *Finder,
                                                   bool Value,
                                                   StringRef OperatorName,
                                                   StringRef BooleanId) {
  Finder->addMatcher(
      binaryOperator(isExpansionInMainFile(), hasOperatorName(OperatorName),
                     unless(hasLHS(hasDescendant(cxxBoolLiteral()))),
                     hasLHS(expr().bind(LHSId)),
                     hasRHS(allOf(expr().bind(RHSId),
                                  ignoringImpCasts(cxxBoolLiteral(equals(Value))
                                                       .bind(BooleanId))))),
      this);
}

void SimplifyBooleanExprCheck::matchBoolCondition(MatchFinder *Finder,
                                                  bool Value,
                                                  StringRef BooleanId) {
  Finder->addMatcher(
      ifStmt(isExpansionInMainFile(),
             hasCondition(cxxBoolLiteral(equals(Value)).bind(BooleanId)))
          .bind(IfStmtId),
      this);
}

void SimplifyBooleanExprCheck::matchTernaryResult(MatchFinder *Finder,
                                                  bool Value,
                                                  StringRef TernaryId) {
  Finder->addMatcher(
      conditionalOperator(isExpansionInMainFile(),
                          hasTrueExpression(cxxBoolLiteral(equals(Value))),
                          hasFalseExpression(cxxBoolLiteral(equals(!Value))))
          .bind(TernaryId),
      this);
}

void SimplifyBooleanExprCheck::matchIfReturnsBool(MatchFinder *Finder,
                                                  bool Value, StringRef Id) {
  if (ChainedConditionalReturn) {
    Finder->addMatcher(ifStmt(isExpansionInMainFile(),
                              hasThen(returnsBool(Value, ThenLiteralId)),
                              hasElse(returnsBool(!Value)))
                           .bind(Id),
                       this);
  } else {
    Finder->addMatcher(ifStmt(isExpansionInMainFile(),
                              unless(hasParent(ifStmt())),
                              hasThen(returnsBool(Value, ThenLiteralId)),
                              hasElse(returnsBool(!Value)))
                           .bind(Id),
                       this);
  }
}

void SimplifyBooleanExprCheck::matchIfAssignsBool(MatchFinder *Finder,
                                                  bool Value, StringRef Id) {
  auto SimpleThen = binaryOperator(
      hasOperatorName("="),
      hasLHS(declRefExpr(hasDeclaration(decl().bind(IfAssignObjId)))),
      hasLHS(expr().bind(IfAssignVariableId)),
      hasRHS(cxxBoolLiteral(equals(Value)).bind(IfAssignLocId)));
  auto Then = anyOf(SimpleThen, compoundStmt(statementCountIs(1),
                                             hasAnySubstatement(SimpleThen)));
  auto SimpleElse = binaryOperator(
      hasOperatorName("="),
      hasLHS(declRefExpr(hasDeclaration(equalsBoundNode(IfAssignObjId)))),
      hasRHS(cxxBoolLiteral(equals(!Value))));
  auto Else = anyOf(SimpleElse, compoundStmt(statementCountIs(1),
                                             hasAnySubstatement(SimpleElse)));
  if (ChainedConditionalAssignment) {
    Finder->addMatcher(
        ifStmt(isExpansionInMainFile(), hasThen(Then), hasElse(Else)).bind(Id),
        this);
  } else {
    Finder->addMatcher(ifStmt(isExpansionInMainFile(),
                              unless(hasParent(ifStmt())), hasThen(Then),
                              hasElse(Else))
                           .bind(Id),
                       this);
  }
}

void SimplifyBooleanExprCheck::matchCompoundIfReturnsBool(MatchFinder *Finder,
                                                          bool Value,
                                                          StringRef Id) {
  Finder->addMatcher(
      compoundStmt(allOf(hasAnySubstatement(ifStmt(hasThen(returnsBool(Value)),
                                                   unless(hasElse(stmt())))),
                         hasAnySubstatement(
                             returnStmt(has(cxxBoolLiteral(equals(!Value))))
                                 .bind(CompoundReturnId))))
          .bind(Id),
      this);
}

void SimplifyBooleanExprCheck::storeOptions(ClangTidyOptions::OptionMap &Opts) {
  Options.store(Opts, "ChainedConditionalReturn", ChainedConditionalReturn);
  Options.store(Opts, "ChainedConditionalAssignment",
                ChainedConditionalAssignment);
}

void SimplifyBooleanExprCheck::registerMatchers(MatchFinder *Finder) {
  matchBoolBinOpExpr(Finder, true, "&&", RightExpressionId);
  matchBoolBinOpExpr(Finder, false, "||", RightExpressionId);
  matchExprBinOpBool(Finder, false, "&&", RightExpressionId);
  matchExprBinOpBool(Finder, true, "||", RightExpressionId);
  matchBoolCompOpExpr(Finder, true, "==", RightExpressionId);
  matchBoolCompOpExpr(Finder, false, "!=", RightExpressionId);

  matchExprBinOpBool(Finder, true, "&&", LeftExpressionId);
  matchExprBinOpBool(Finder, false, "||", LeftExpressionId);
  matchBoolBinOpExpr(Finder, false, "&&", LeftExpressionId);
  matchBoolBinOpExpr(Finder, true, "||", LeftExpressionId);
  matchExprCompOpBool(Finder, true, "==", LeftExpressionId);
  matchExprCompOpBool(Finder, false, "!=", LeftExpressionId);

  matchBoolCompOpExpr(Finder, false, "==", NegatedRightExpressionId);
  matchBoolCompOpExpr(Finder, true, "!=", NegatedRightExpressionId);

  matchExprCompOpBool(Finder, false, "==", NegatedLeftExpressionId);
  matchExprCompOpBool(Finder, true, "!=", NegatedLeftExpressionId);

  matchBoolCondition(Finder, true, ConditionThenStmtId);
  matchBoolCondition(Finder, false, ConditionElseStmtId);

  matchTernaryResult(Finder, true, TernaryId);
  matchTernaryResult(Finder, false, TernaryNegatedId);

  matchIfReturnsBool(Finder, true, IfReturnsBoolId);
  matchIfReturnsBool(Finder, false, IfReturnsNotBoolId);

  matchIfAssignsBool(Finder, true, IfAssignBoolId);
  matchIfAssignsBool(Finder, false, IfAssignNotBoolId);

  matchCompoundIfReturnsBool(Finder, true, CompoundBoolId);
  matchCompoundIfReturnsBool(Finder, false, CompoundNotBoolId);
}

void SimplifyBooleanExprCheck::check(const MatchFinder::MatchResult &Result) {
  if (const CXXBoolLiteralExpr *LeftRemoved =
          getBoolLiteral(Result, RightExpressionId)) {
    replaceWithExpression(Result, LeftRemoved, false);
  } else if (const CXXBoolLiteralExpr *RightRemoved =
                 getBoolLiteral(Result, LeftExpressionId)) {
    replaceWithExpression(Result, RightRemoved, true);
  } else if (const CXXBoolLiteralExpr *NegatedLeftRemoved =
                 getBoolLiteral(Result, NegatedRightExpressionId)) {
    replaceWithExpression(Result, NegatedLeftRemoved, false, true);
  } else if (const CXXBoolLiteralExpr *NegatedRightRemoved =
                 getBoolLiteral(Result, NegatedLeftExpressionId)) {
    replaceWithExpression(Result, NegatedRightRemoved, true, true);
  } else if (const CXXBoolLiteralExpr *TrueConditionRemoved =
                 getBoolLiteral(Result, ConditionThenStmtId)) {
    replaceWithThenStatement(Result, TrueConditionRemoved);
  } else if (const CXXBoolLiteralExpr *FalseConditionRemoved =
                 getBoolLiteral(Result, ConditionElseStmtId)) {
    replaceWithElseStatement(Result, FalseConditionRemoved);
  } else if (const auto *Ternary =
                 Result.Nodes.getNodeAs<ConditionalOperator>(TernaryId)) {
    replaceWithCondition(Result, Ternary);
  } else if (const auto *TernaryNegated =
                 Result.Nodes.getNodeAs<ConditionalOperator>(
                     TernaryNegatedId)) {
    replaceWithCondition(Result, TernaryNegated, true);
  } else if (const auto *If = Result.Nodes.getNodeAs<IfStmt>(IfReturnsBoolId)) {
    replaceWithReturnCondition(Result, If);
  } else if (const auto *IfNot =
                 Result.Nodes.getNodeAs<IfStmt>(IfReturnsNotBoolId)) {
    replaceWithReturnCondition(Result, IfNot, true);
  } else if (const auto *IfAssign =
                 Result.Nodes.getNodeAs<IfStmt>(IfAssignBoolId)) {
    replaceWithAssignment(Result, IfAssign);
  } else if (const auto *IfAssignNot =
                 Result.Nodes.getNodeAs<IfStmt>(IfAssignNotBoolId)) {
    replaceWithAssignment(Result, IfAssignNot, true);
  } else if (const auto *Compound =
                 Result.Nodes.getNodeAs<CompoundStmt>(CompoundBoolId)) {
    replaceCompoundReturnWithCondition(Result, Compound);
  } else if (const auto *Compound =
                 Result.Nodes.getNodeAs<CompoundStmt>(CompoundNotBoolId)) {
    replaceCompoundReturnWithCondition(Result, Compound, true);
  }
}

void SimplifyBooleanExprCheck::replaceWithExpression(
    const ast_matchers::MatchFinder::MatchResult &Result,
    const CXXBoolLiteralExpr *BoolLiteral, bool UseLHS, bool Negated) {
  const auto *LHS = Result.Nodes.getNodeAs<Expr>(LHSId);
  const auto *RHS = Result.Nodes.getNodeAs<Expr>(RHSId);
  std::string Replacement =
      replacementExpression(Result, Negated, UseLHS ? LHS : RHS);
  SourceLocation Start = LHS->getLocStart();
  SourceLocation End = RHS->getLocEnd();
  diag(BoolLiteral->getLocStart(), SimplifyOperatorDiagnostic)
      << FixItHint::CreateReplacement(SourceRange(Start, End), Replacement);
}

void SimplifyBooleanExprCheck::replaceWithThenStatement(
    const MatchFinder::MatchResult &Result,
    const CXXBoolLiteralExpr *TrueConditionRemoved) {
  const auto *IfStatement = Result.Nodes.getNodeAs<IfStmt>(IfStmtId);
  diag(TrueConditionRemoved->getLocStart(), SimplifyConditionDiagnostic)
      << FixItHint::CreateReplacement(IfStatement->getSourceRange(),
                                      getText(Result, *IfStatement->getThen()));
}

void SimplifyBooleanExprCheck::replaceWithElseStatement(
    const MatchFinder::MatchResult &Result,
    const CXXBoolLiteralExpr *FalseConditionRemoved) {
  const auto *IfStatement = Result.Nodes.getNodeAs<IfStmt>(IfStmtId);
  const Stmt *ElseStatement = IfStatement->getElse();
  diag(FalseConditionRemoved->getLocStart(), SimplifyConditionDiagnostic)
      << FixItHint::CreateReplacement(
          IfStatement->getSourceRange(),
          ElseStatement ? getText(Result, *ElseStatement) : "");
}

void SimplifyBooleanExprCheck::replaceWithCondition(
    const MatchFinder::MatchResult &Result, const ConditionalOperator *Ternary,
    bool Negated) {
  std::string Replacement =
      replacementExpression(Result, Negated, Ternary->getCond());
  diag(Ternary->getTrueExpr()->getLocStart(),
       "redundant boolean literal in ternary expression result")
      << FixItHint::CreateReplacement(Ternary->getSourceRange(), Replacement);
}

void SimplifyBooleanExprCheck::replaceWithReturnCondition(
    const MatchFinder::MatchResult &Result, const IfStmt *If, bool Negated) {
  StringRef Terminator = isa<CompoundStmt>(If->getElse()) ? ";" : "";
  std::string Condition = replacementExpression(Result, Negated, If->getCond());
  std::string Replacement = ("return " + Condition + Terminator).str();
  SourceLocation Start =
      Result.Nodes.getNodeAs<CXXBoolLiteralExpr>(ThenLiteralId)->getLocStart();
  diag(Start, SimplifyConditionalReturnDiagnostic)
      << FixItHint::CreateReplacement(If->getSourceRange(), Replacement);
}

void SimplifyBooleanExprCheck::replaceCompoundReturnWithCondition(
    const MatchFinder::MatchResult &Result, const CompoundStmt *Compound,
    bool Negated) {
  const auto *Ret = Result.Nodes.getNodeAs<ReturnStmt>(CompoundReturnId);

  // The body shouldn't be empty because the matcher ensures that it must
  // contain at least two statements:
  // 1) A `return` statement returning a boolean literal `false` or `true`
  // 2) An `if` statement with no `else` clause that consists fo a single
  //    `return` statement returning the opposite boolean literal `true` or
  //    `false`.
  assert(Compound->size() >= 2);
  const IfStmt *BeforeIf = nullptr;
  CompoundStmt::const_body_iterator Current = Compound->body_begin();
  CompoundStmt::const_body_iterator After = Compound->body_begin();
  for (++After; After != Compound->body_end() && *Current != Ret;
       ++Current, ++After) {
    if (const auto *If = dyn_cast<IfStmt>(*Current)) {
      if (const CXXBoolLiteralExpr *Lit = stmtReturnsBool(If, Negated)) {
        if (*After == Ret) {
          if (!ChainedConditionalReturn && BeforeIf)
            continue;

          const Expr *Condition = If->getCond();
          std::string Replacement =
              "return " + replacementExpression(Result, Negated, Condition);
          diag(Lit->getLocStart(), SimplifyConditionalReturnDiagnostic)
              << FixItHint::CreateReplacement(
                  SourceRange(If->getLocStart(), Ret->getLocEnd()),
                  Replacement);
          return;
        }

        BeforeIf = If;
      }
    } else {
      BeforeIf = nullptr;
    }
  }
}

void SimplifyBooleanExprCheck::replaceWithAssignment(
    const MatchFinder::MatchResult &Result, const IfStmt *IfAssign,
    bool Negated) {
  SourceRange Range = IfAssign->getSourceRange();
  StringRef VariableName =
      getText(Result, *Result.Nodes.getNodeAs<Expr>(IfAssignVariableId));
  StringRef Terminator = isa<CompoundStmt>(IfAssign->getElse()) ? ";" : "";
  std::string Condition =
      replacementExpression(Result, Negated, IfAssign->getCond());
  std::string Replacement =
      (VariableName + " = " + Condition + Terminator).str();
  SourceLocation Location =
      Result.Nodes.getNodeAs<CXXBoolLiteralExpr>(IfAssignLocId)->getLocStart();
  this->diag(Location, "redundant boolean literal in conditional assignment")
      << FixItHint::CreateReplacement(Range, Replacement);
}

} // namespace readability
} // namespace tidy
} // namespace clang