text: //=- AnalysisBasedWarnings.cpp - Sema warnings based on libAnalysis -*- C++ -*-=//
  //
  // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
  // See https://llvm.org/LICENSE.txt for license information.
  // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
  //
  //===----------------------------------------------------------------------===//
  //
  // This file defines analysis_warnings::[Policy,Executor].
  // Together they are used by Sema to issue warnings based on inexpensive
  // static analysis algorithms in libAnalysis.
  //
  //===----------------------------------------------------------------------===//
  
  #include "clang/Sema/AnalysisBasedWarnings.h"
  #include "clang/AST/DeclCXX.h"
  #include "clang/AST/DeclObjC.h"
  #include "clang/AST/EvaluatedExprVisitor.h"
  #include "clang/AST/ExprCXX.h"
  #include "clang/AST/ExprObjC.h"
  #include "clang/AST/ParentMap.h"
  #include "clang/AST/RecursiveASTVisitor.h"
  #include "clang/AST/StmtCXX.h"
  #include "clang/AST/StmtObjC.h"
  #include "clang/AST/StmtVisitor.h"
  #include "clang/Analysis/Analyses/CFGReachabilityAnalysis.h"
  #include "clang/Analysis/Analyses/Consumed.h"
  #include "clang/Analysis/Analyses/ReachableCode.h"
  #include "clang/Analysis/Analyses/ThreadSafety.h"
  #include "clang/Analysis/Analyses/UninitializedValues.h"
  #include "clang/Analysis/AnalysisDeclContext.h"
  #include "clang/Analysis/CFG.h"
  #include "clang/Analysis/CFGStmtMap.h"
  #include "clang/Basic/SourceLocation.h"
  #include "clang/Basic/SourceManager.h"
  #include "clang/Lex/Preprocessor.h"
  #include "clang/Sema/ScopeInfo.h"
  #include "clang/Sema/SemaInternal.h"
  #include "llvm/ADT/BitVector.h"
  #include "llvm/ADT/MapVector.h"
  #include "llvm/ADT/SmallString.h"
  #include "llvm/ADT/SmallVector.h"
  #include "llvm/ADT/StringRef.h"
  #include "llvm/Support/Casting.h"
  #include <algorithm>
  #include <deque>
  #include <iterator>
  
  using namespace clang;
  
  //===----------------------------------------------------------------------===//
  // Unreachable code analysis.
  //===----------------------------------------------------------------------===//
  
  namespace {
    class UnreachableCodeHandler : public reachable_code::Callback {
      Sema &S;
      SourceRange PreviousSilenceableCondVal;
  
    public:
      UnreachableCodeHandler(Sema &s) : S(s) {}
  
      void HandleUnreachable(reachable_code::UnreachableKind UK,
                             SourceLocation L,
                             SourceRange SilenceableCondVal,
                             SourceRange R1,
                             SourceRange R2) override {
        // Avoid reporting multiple unreachable code diagnostics that are
        // triggered by the same conditional value.
        if (PreviousSilenceableCondVal.isValid() &&
            SilenceableCondVal.isValid() &&
            PreviousSilenceableCondVal == SilenceableCondVal)
          return;
        PreviousSilenceableCondVal = SilenceableCondVal;
  
        unsigned diag = diag::warn_unreachable;
        switch (UK) {
          case reachable_code::UK_Break:
            diag = diag::warn_unreachable_break;
            break;
          case reachable_code::UK_Return:
            diag = diag::warn_unreachable_return;
            break;
          case reachable_code::UK_Loop_Increment:
            diag = diag::warn_unreachable_loop_increment;
            break;
          case reachable_code::UK_Other:
            break;
        }
  
        S.Diag(L, diag) << R1 << R2;
  
        SourceLocation Open = SilenceableCondVal.getBegin();
        if (Open.isValid()) {
          SourceLocation Close = SilenceableCondVal.getEnd();
          Close = S.getLocForEndOfToken(Close);
          if (Close.isValid()) {
            S.Diag(Open, diag::note_unreachable_silence)
              << FixItHint::CreateInsertion(Open, "/* DISABLES CODE */ (")
              << FixItHint::CreateInsertion(Close, ")");
          }
        }
      }
    };
  } // anonymous namespace
  
  /// CheckUnreachable - Check for unreachable code.
  static void CheckUnreachable(Sema &S, AnalysisDeclContext &AC) {
    // As a heuristic prune all diagnostics not in the main file.  Currently
    // the majority of warnings in headers are false positives.  These
    // are largely caused by configuration state, e.g. preprocessor
    // defined code, etc.
    //
    // Note that this is also a performance optimization.  Analyzing
    // headers many times can be expensive.
    if (!S.getSourceManager().isInMainFile(AC.getDecl()->getBeginLoc()))
      return;
  
    UnreachableCodeHandler UC(S);
    reachable_code::FindUnreachableCode(AC, S.getPreprocessor(), UC);
  }
  
  namespace {
  /// Warn on logical operator errors in CFGBuilder
  class LogicalErrorHandler : public CFGCallback {
    Sema &S;
  
  public:
    LogicalErrorHandler(Sema &S) : CFGCallback(), S(S) {}
  
    static bool HasMacroID(const Expr *E) {
      if (E->getExprLoc().isMacroID())
        return true;
  
      // Recurse to children.
      for (const Stmt *SubStmt : E->children())
        if (const Expr *SubExpr = dyn_cast_or_null<Expr>(SubStmt))
          if (HasMacroID(SubExpr))
            return true;
  
      return false;
    }
  
    void compareAlwaysTrue(const BinaryOperator *B, bool isAlwaysTrue) override {
      if (HasMacroID(B))
        return;
  
      SourceRange DiagRange = B->getSourceRange();
      S.Diag(B->getExprLoc(), diag::warn_tautological_overlap_comparison)
          << DiagRange << isAlwaysTrue;
    }
  
    void compareBitwiseEquality(const BinaryOperator *B,
                                bool isAlwaysTrue) override {
      if (HasMacroID(B))
        return;
  
      SourceRange DiagRange = B->getSourceRange();
      S.Diag(B->getExprLoc(), diag::warn_comparison_bitwise_always)
          << DiagRange << isAlwaysTrue;
    }
  };
  } // anonymous namespace
  
  //===----------------------------------------------------------------------===//
  // Check for infinite self-recursion in functions
  //===----------------------------------------------------------------------===//
  
  // Returns true if the function is called anywhere within the CFGBlock.
  // For member functions, the additional condition of being call from the
  // this pointer is required.
  static bool hasRecursiveCallInPath(const FunctionDecl *FD, CFGBlock &Block) {
    // Process all the Stmt's in this block to find any calls to FD.
    for (const auto &B : Block) {
      if (B.getKind() != CFGElement::Statement)
        continue;
  
      const CallExpr *CE = dyn_cast<CallExpr>(B.getAs<CFGStmt>()->getStmt());
      if (!CE || !CE->getCalleeDecl() ||
          CE->getCalleeDecl()->getCanonicalDecl() != FD)
        continue;
  
      // Skip function calls which are qualified with a templated class.
      if (const DeclRefExpr *DRE =
              dyn_cast<DeclRefExpr>(CE->getCallee()->IgnoreParenImpCasts())) {
        if (NestedNameSpecifier *NNS = DRE->getQualifier()) {
          if (NNS->getKind() == NestedNameSpecifier::TypeSpec &&
              isa<TemplateSpecializationType>(NNS->getAsType())) {
            continue;
          }
        }
      }
  
      const CXXMemberCallExpr *MCE = dyn_cast<CXXMemberCallExpr>(CE);
      if (!MCE || isa<CXXThisExpr>(MCE->getImplicitObjectArgument()) ||
          !MCE->getMethodDecl()->isVirtual())
        return true;
    }
    return false;
  }
  
  // Returns true if every path from the entry block passes through a call to FD.
  static bool checkForRecursiveFunctionCall(const FunctionDecl *FD, CFG *cfg) {
    llvm::SmallPtrSet<CFGBlock *, 16> Visited;
    llvm::SmallVector<CFGBlock *, 16> WorkList;
    // Keep track of whether we found at least one recursive path.
    bool foundRecursion = false;
  
    const unsigned ExitID = cfg->getExit().getBlockID();
  
    // Seed the work list with the entry block.
    WorkList.push_back(&cfg->getEntry());
  
    while (!WorkList.empty()) {
      CFGBlock *Block = WorkList.pop_back_val();
  
      for (auto I = Block->succ_begin(), E = Block->succ_end(); I != E; ++I) {
        if (CFGBlock *SuccBlock = *I) {
          if (!Visited.insert(SuccBlock).second)
            continue;
  
          // Found a path to the exit node without a recursive call.
          if (ExitID == SuccBlock->getBlockID())
            return false;
  
          // If the successor block contains a recursive call, end analysis there.
          if (hasRecursiveCallInPath(FD, *SuccBlock)) {
            foundRecursion = true;
            continue;
          }
  
          WorkList.push_back(SuccBlock);
        }
      }
    }
    return foundRecursion;
  }
  
  static void checkRecursiveFunction(Sema &S, const FunctionDecl *FD,
                                     const Stmt *Body, AnalysisDeclContext &AC) {
    FD = FD->getCanonicalDecl();
  
    // Only run on non-templated functions and non-templated members of
    // templated classes.
    if (FD->getTemplatedKind() != FunctionDecl::TK_NonTemplate &&
        FD->getTemplatedKind() != FunctionDecl::TK_MemberSpecialization)
      return;
  
    CFG *cfg = AC.getCFG();
    if (!cfg) return;
  
    // If the exit block is unreachable, skip processing the function.
    if (cfg->getExit().pred_empty())
      return;
  
    // Emit diagnostic if a recursive function call is detected for all paths.
    if (checkForRecursiveFunctionCall(FD, cfg))
      S.Diag(Body->getBeginLoc(), diag::warn_infinite_recursive_function);
  }
  
  //===----------------------------------------------------------------------===//
  // Check for throw in a non-throwing function.
  //===----------------------------------------------------------------------===//
  
  /// Determine whether an exception thrown by E, unwinding from ThrowBlock,
  /// can reach ExitBlock.
  static bool throwEscapes(Sema &S, const CXXThrowExpr *E, CFGBlock &ThrowBlock,
                           CFG *Body) {
    SmallVector<CFGBlock *, 16> Stack;
    llvm::BitVector Queued(Body->getNumBlockIDs());
  
    Stack.push_back(&ThrowBlock);
    Queued[ThrowBlock.getBlockID()] = true;
  
    while (!Stack.empty()) {
      CFGBlock &UnwindBlock = *Stack.back();
      Stack.pop_back();
  
      for (auto &Succ : UnwindBlock.succs()) {
        if (!Succ.isReachable() || Queued[Succ->getBlockID()])
          continue;
  
        if (Succ->getBlockID() == Body->getExit().getBlockID())
          return true;
  
        if (auto *Catch =
                dyn_cast_or_null<CXXCatchStmt>(Succ->getLabel())) {
          QualType Caught = Catch->getCaughtType();
          if (Caught.isNull() || // catch (...) catches everything
              !E->getSubExpr() || // throw; is considered cuaght by any handler
              S.handlerCanCatch(Caught, E->getSubExpr()->getType()))
            // Exception doesn't escape via this path.
            break;
        } else {
          Stack.push_back(Succ);
          Queued[Succ->getBlockID()] = true;
        }
      }
    }
  
    return false;
  }
  
  static void visitReachableThrows(
      CFG *BodyCFG,
      llvm::function_ref<void(const CXXThrowExpr *, CFGBlock &)> Visit) {
    llvm::BitVector Reachable(BodyCFG->getNumBlockIDs());
    clang::reachable_code::ScanReachableFromBlock(&BodyCFG->getEntry(), Reachable);
    for (CFGBlock *B : *BodyCFG) {
      if (!Reachable[B->getBlockID()])
        continue;
      for (CFGElement &E : *B) {
        Optional<CFGStmt> S = E.getAs<CFGStmt>();
        if (!S)
          continue;
        if (auto *Throw = dyn_cast<CXXThrowExpr>(S->getStmt()))
          Visit(Throw, *B);
      }
    }
  }
  
  static void EmitDiagForCXXThrowInNonThrowingFunc(Sema &S, SourceLocation OpLoc,
                                                   const FunctionDecl *FD) {
    if (!S.getSourceManager().isInSystemHeader(OpLoc) &&
        FD->getTypeSourceInfo()) {
      S.Diag(OpLoc, diag::warn_throw_in_noexcept_func) << FD;
      if (S.getLangOpts().CPlusPlus11 &&
          (isa<CXXDestructorDecl>(FD) ||
           FD->getDeclName().getCXXOverloadedOperator() == OO_Delete ||
           FD->getDeclName().getCXXOverloadedOperator() == OO_Array_Delete)) {
        if (const auto *Ty = FD->getTypeSourceInfo()->getType()->
                                           getAs<FunctionProtoType>())
          S.Diag(FD->getLocation(), diag::note_throw_in_dtor)
              << !isa<CXXDestructorDecl>(FD) << !Ty->hasExceptionSpec()
              << FD->getExceptionSpecSourceRange();
      } else
        S.Diag(FD->getLocation(), diag::note_throw_in_function)
            << FD->getExceptionSpecSourceRange();
    }
  }
  
  static void checkThrowInNonThrowingFunc(Sema &S, const FunctionDecl *FD,
                                          AnalysisDeclContext &AC) {
    CFG *BodyCFG = AC.getCFG();
    if (!BodyCFG)
      return;
    if (BodyCFG->getExit().pred_empty())
      return;
    visitReachableThrows(BodyCFG, [&](const CXXThrowExpr *Throw, CFGBlock &Block) {
      if (throwEscapes(S, Throw, Block, BodyCFG))
        EmitDiagForCXXThrowInNonThrowingFunc(S, Throw->getThrowLoc(), FD);
    });
  }
  
  static bool isNoexcept(const FunctionDecl *FD) {
    const auto *FPT = FD->getType()->castAs<FunctionProtoType>();
    if (FPT->isNothrow() || FD->hasAttr<NoThrowAttr>())
      return true;
    return false;
  }
  
  //===----------------------------------------------------------------------===//
  // Check for missing return value.
  //===----------------------------------------------------------------------===//
  
  enum ControlFlowKind {
    UnknownFallThrough,
    NeverFallThrough,
    MaybeFallThrough,
    AlwaysFallThrough,
    NeverFallThroughOrReturn
  };
  
  /// CheckFallThrough - Check that we don't fall off the end of a
  /// Statement that should return a value.
  ///
  /// \returns AlwaysFallThrough iff we always fall off the end of the statement,
  /// MaybeFallThrough iff we might or might not fall off the end,
  /// NeverFallThroughOrReturn iff we never fall off the end of the statement or
  /// return.  We assume NeverFallThrough iff we never fall off the end of the
  /// statement but we may return.  We assume that functions not marked noreturn
  /// will return.
  static ControlFlowKind CheckFallThrough(AnalysisDeclContext &AC) {
    CFG *cfg = AC.getCFG();
    if (!cfg) return UnknownFallThrough;
  
    // The CFG leaves in dead things, and we don't want the dead code paths to
    // confuse us, so we mark all live things first.
    llvm::BitVector live(cfg->getNumBlockIDs());
    unsigned count = reachable_code::ScanReachableFromBlock(&cfg->getEntry(),
                                                            live);
  
    bool AddEHEdges = AC.getAddEHEdges();
    if (!AddEHEdges && count != cfg->getNumBlockIDs())
      // When there are things remaining dead, and we didn't add EH edges
      // from CallExprs to the catch clauses, we have to go back and
      // mark them as live.
      for (const auto *B : *cfg) {
        if (!live[B->getBlockID()]) {
          if (B->pred_begin() == B->pred_end()) {
            if (B->getTerminator() && isa<CXXTryStmt>(B->getTerminator()))
              // When not adding EH edges from calls, catch clauses
              // can otherwise seem dead.  Avoid noting them as dead.
              count += reachable_code::ScanReachableFromBlock(B, live);
            continue;
          }
        }
      }
  
    // Now we know what is live, we check the live precessors of the exit block
    // and look for fall through paths, being careful to ignore normal returns,
    // and exceptional paths.
    bool HasLiveReturn = false;
    bool HasFakeEdge = false;
    bool HasPlainEdge = false;
    bool HasAbnormalEdge = false;
  
    // Ignore default cases that aren't likely to be reachable because all
    // enums in a switch(X) have explicit case statements.
    CFGBlock::FilterOptions FO;
    FO.IgnoreDefaultsWithCoveredEnums = 1;
  
    for (CFGBlock::filtered_pred_iterator I =
             cfg->getExit().filtered_pred_start_end(FO);
         I.hasMore(); ++I) {
      const CFGBlock &B = **I;
      if (!live[B.getBlockID()])
        continue;
  
      // Skip blocks which contain an element marked as no-return. They don't
      // represent actually viable edges into the exit block, so mark them as
      // abnormal.
      if (B.hasNoReturnElement()) {
        HasAbnormalEdge = true;
        continue;
      }
  
      // Destructors can appear after the 'return' in the CFG.  This is
      // normal.  We need to look pass the destructors for the return
      // statement (if it exists).
      CFGBlock::const_reverse_iterator ri = B.rbegin(), re = B.rend();
  
      for ( ; ri != re ; ++ri)
        if (ri->getAs<CFGStmt>())
          break;
  
      // No more CFGElements in the block?
      if (ri == re) {
        if (B.getTerminator() && isa<CXXTryStmt>(B.getTerminator())) {
          HasAbnormalEdge = true;
          continue;
        }
        // A labeled empty statement, or the entry block...
        HasPlainEdge = true;
        continue;
      }
  
      CFGStmt CS = ri->castAs<CFGStmt>();
      const Stmt *S = CS.getStmt();
      if (isa<ReturnStmt>(S) || isa<CoreturnStmt>(S)) {
        HasLiveReturn = true;
        continue;
      }
      if (isa<ObjCAtThrowStmt>(S)) {
        HasFakeEdge = true;
        continue;
      }
      if (isa<CXXThrowExpr>(S)) {
        HasFakeEdge = true;
        continue;
      }
      if (isa<MSAsmStmt>(S)) {
        // TODO: Verify this is correct.
        HasFakeEdge = true;
        HasLiveReturn = true;
        continue;
      }
      if (isa<CXXTryStmt>(S)) {
        HasAbnormalEdge = true;
        continue;
      }
      if (std::find(B.succ_begin(), B.succ_end(), &cfg->getExit())
          == B.succ_end()) {
        HasAbnormalEdge = true;
        continue;
      }
  
      HasPlainEdge = true;
    }
    if (!HasPlainEdge) {
      if (HasLiveReturn)
        return NeverFallThrough;
      return NeverFallThroughOrReturn;
    }
    if (HasAbnormalEdge || HasFakeEdge || HasLiveReturn)
      return MaybeFallThrough;
    // This says AlwaysFallThrough for calls to functions that are not marked
    // noreturn, that don't return.  If people would like this warning to be more
    // accurate, such functions should be marked as noreturn.
    return AlwaysFallThrough;
  }
  
  namespace {
  
  struct CheckFallThroughDiagnostics {
    unsigned diag_MaybeFallThrough_HasNoReturn;
    unsigned diag_MaybeFallThrough_ReturnsNonVoid;
    unsigned diag_AlwaysFallThrough_HasNoReturn;
    unsigned diag_AlwaysFallThrough_ReturnsNonVoid;
    unsigned diag_NeverFallThroughOrReturn;
    enum { Function, Block, Lambda, Coroutine } funMode;
    SourceLocation FuncLoc;
  
    static CheckFallThroughDiagnostics MakeForFunction(const Decl *Func) {
      CheckFallThroughDiagnostics D;
      D.FuncLoc = Func->getLocation();
      D.diag_MaybeFallThrough_HasNoReturn =
        diag::warn_falloff_noreturn_function;
      D.diag_MaybeFallThrough_ReturnsNonVoid =
        diag::warn_maybe_falloff_nonvoid_function;
      D.diag_AlwaysFallThrough_HasNoReturn =
        diag::warn_falloff_noreturn_function;
      D.diag_AlwaysFallThrough_ReturnsNonVoid =
        diag::warn_falloff_nonvoid_function;
  
      // Don't suggest that virtual functions be marked "noreturn", since they
      // might be overridden by non-noreturn functions.
      bool isVirtualMethod = false;
      if (const CXXMethodDecl *Method = dyn_cast<CXXMethodDecl>(Func))
        isVirtualMethod = Method->isVirtual();
  
      // Don't suggest that template instantiations be marked "noreturn"
      bool isTemplateInstantiation = false;
      if (const FunctionDecl *Function = dyn_cast<FunctionDecl>(Func))
        isTemplateInstantiation = Function->isTemplateInstantiation();
  
      if (!isVirtualMethod && !isTemplateInstantiation)
        D.diag_NeverFallThroughOrReturn =
          diag::warn_suggest_noreturn_function;
      else
        D.diag_NeverFallThroughOrReturn = 0;
  
      D.funMode = Function;
      return D;
    }
  
    static CheckFallThroughDiagnostics MakeForCoroutine(const Decl *Func) {
      CheckFallThroughDiagnostics D;
      D.FuncLoc = Func->getLocation();
      D.diag_MaybeFallThrough_HasNoReturn = 0;
      D.diag_MaybeFallThrough_ReturnsNonVoid =
          diag::warn_maybe_falloff_nonvoid_coroutine;
      D.diag_AlwaysFallThrough_HasNoReturn = 0;
      D.diag_AlwaysFallThrough_ReturnsNonVoid =
          diag::warn_falloff_nonvoid_coroutine;
      D.funMode = Coroutine;
      return D;
    }
  
    static CheckFallThroughDiagnostics MakeForBlock() {
      CheckFallThroughDiagnostics D;
      D.diag_MaybeFallThrough_HasNoReturn =
        diag::err_noreturn_block_has_return_expr;
      D.diag_MaybeFallThrough_ReturnsNonVoid =
        diag::err_maybe_falloff_nonvoid_block;
      D.diag_AlwaysFallThrough_HasNoReturn =
        diag::err_noreturn_block_has_return_expr;
      D.diag_AlwaysFallThrough_ReturnsNonVoid =
        diag::err_falloff_nonvoid_block;
      D.diag_NeverFallThroughOrReturn = 0;
      D.funMode = Block;
      return D;
    }
  
    static CheckFallThroughDiagnostics MakeForLambda() {
      CheckFallThroughDiagnostics D;
      D.diag_MaybeFallThrough_HasNoReturn =
        diag::err_noreturn_lambda_has_return_expr;
      D.diag_MaybeFallThrough_ReturnsNonVoid =
        diag::warn_maybe_falloff_nonvoid_lambda;
      D.diag_AlwaysFallThrough_HasNoReturn =
        diag::err_noreturn_lambda_has_return_expr;
      D.diag_AlwaysFallThrough_ReturnsNonVoid =
        diag::warn_falloff_nonvoid_lambda;
      D.diag_NeverFallThroughOrReturn = 0;
      D.funMode = Lambda;
      return D;
    }
  
    bool checkDiagnostics(DiagnosticsEngine &D, bool ReturnsVoid,
                          bool HasNoReturn) const {
      if (funMode == Function) {
        return (ReturnsVoid ||
                D.isIgnored(diag::warn_maybe_falloff_nonvoid_function,
                            FuncLoc)) &&
               (!HasNoReturn ||
                D.isIgnored(diag::warn_noreturn_function_has_return_expr,
                            FuncLoc)) &&
               (!ReturnsVoid ||
                D.isIgnored(diag::warn_suggest_noreturn_block, FuncLoc));
      }
      if (funMode == Coroutine) {
        return (ReturnsVoid ||
                D.isIgnored(diag::warn_maybe_falloff_nonvoid_function, FuncLoc) ||
                D.isIgnored(diag::warn_maybe_falloff_nonvoid_coroutine,
                            FuncLoc)) &&
               (!HasNoReturn);
      }
      // For blocks / lambdas.
      return ReturnsVoid && !HasNoReturn;
    }
  };
  
  } // anonymous namespace
  
  /// CheckFallThroughForBody - Check that we don't fall off the end of a
  /// function that should return a value.  Check that we don't fall off the end
  /// of a noreturn function.  We assume that functions and blocks not marked
  /// noreturn will return.
  static void CheckFallThroughForBody(Sema &S, const Decl *D, const Stmt *Body,
                                      const BlockExpr *blkExpr,
                                      const CheckFallThroughDiagnostics &CD,
                                      AnalysisDeclContext &AC,
                                      sema::FunctionScopeInfo *FSI) {
  
    bool ReturnsVoid = false;
    bool HasNoReturn = false;
    bool IsCoroutine = FSI->isCoroutine();
  
    if (const auto *FD = dyn_cast<FunctionDecl>(D)) {
      if (const auto *CBody = dyn_cast<CoroutineBodyStmt>(Body))
        ReturnsVoid = CBody->getFallthroughHandler() != nullptr;
      else
        ReturnsVoid = FD->getReturnType()->isVoidType();
      HasNoReturn = FD->isNoReturn();
    }
    else if (const auto *MD = dyn_cast<ObjCMethodDecl>(D)) {
      ReturnsVoid = MD->getReturnType()->isVoidType();
      HasNoReturn = MD->hasAttr<NoReturnAttr>();
    }
    else if (isa<BlockDecl>(D)) {
      QualType BlockTy = blkExpr->getType();
      if (const FunctionType *FT =
            BlockTy->getPointeeType()->getAs<FunctionType>()) {
        if (FT->getReturnType()->isVoidType())
          ReturnsVoid = true;
        if (FT->getNoReturnAttr())
          HasNoReturn = true;
      }
    }
  
    DiagnosticsEngine &Diags = S.getDiagnostics();
  
    // Short circuit for compilation speed.
    if (CD.checkDiagnostics(Diags, ReturnsVoid, HasNoReturn))
        return;
    SourceLocation LBrace = Body->getBeginLoc(), RBrace = Body->getEndLoc();
    auto EmitDiag = [&](SourceLocation Loc, unsigned DiagID) {
      if (IsCoroutine)
        S.Diag(Loc, DiagID) << FSI->CoroutinePromise->getType();
      else
        S.Diag(Loc, DiagID);
    };
  
    // cpu_dispatch functions permit empty function bodies for ICC compatibility.
    if (D->getAsFunction() && D->getAsFunction()->isCPUDispatchMultiVersion())
      return;
  
    // Either in a function body compound statement, or a function-try-block.
    switch (CheckFallThrough(AC)) {
      case UnknownFallThrough:
        break;
  
      case MaybeFallThrough:
        if (HasNoReturn)
          EmitDiag(RBrace, CD.diag_MaybeFallThrough_HasNoReturn);
        else if (!ReturnsVoid)
          EmitDiag(RBrace, CD.diag_MaybeFallThrough_ReturnsNonVoid);
        break;
      case AlwaysFallThrough:
        if (HasNoReturn)
          EmitDiag(RBrace, CD.diag_AlwaysFallThrough_HasNoReturn);
        else if (!ReturnsVoid)
          EmitDiag(RBrace, CD.diag_AlwaysFallThrough_ReturnsNonVoid);
        break;
      case NeverFallThroughOrReturn:
        if (ReturnsVoid && !HasNoReturn && CD.diag_NeverFallThroughOrReturn) {
          if (const FunctionDecl *FD = dyn_cast<FunctionDecl>(D)) {
            S.Diag(LBrace, CD.diag_NeverFallThroughOrReturn) << 0 << FD;
          } else if (const ObjCMethodDecl *MD = dyn_cast<ObjCMethodDecl>(D)) {
            S.Diag(LBrace, CD.diag_NeverFallThroughOrReturn) << 1 << MD;
          } else {
            S.Diag(LBrace, CD.diag_NeverFallThroughOrReturn);
          }
        }
        break;
      case NeverFallThrough:
        break;
    }
  }
  
  //===----------------------------------------------------------------------===//
  // -Wuninitialized
  //===----------------------------------------------------------------------===//
  
  namespace {
  /// ContainsReference - A visitor class to search for references to
  /// a particular declaration (the needle) within any evaluated component of an
  /// expression (recursively).
  class ContainsReference : public ConstEvaluatedExprVisitor<ContainsReference> {
    bool FoundReference;
    const DeclRefExpr *Needle;
  
  public:
    typedef ConstEvaluatedExprVisitor<ContainsReference> Inherited;
  
    ContainsReference(ASTContext &Context, const DeclRefExpr *Needle)
      : Inherited(Context), FoundReference(false), Needle(Needle) {}
  
    void VisitExpr(const Expr *E) {
      // Stop evaluating if we already have a reference.
      if (FoundReference)
        return;
  
      Inherited::VisitExpr(E);
    }
  
    void VisitDeclRefExpr(const DeclRefExpr *E) {
      if (E == Needle)
        FoundReference = true;
      else
        Inherited::VisitDeclRefExpr(E);
    }
  
    bool doesContainReference() const { return FoundReference; }
  };
  } // anonymous namespace
  
  static bool SuggestInitializationFixit(Sema &S, const VarDecl *VD) {
    QualType VariableTy = VD->getType().getCanonicalType();
    if (VariableTy->isBlockPointerType() &&
        !VD->hasAttr<BlocksAttr>()) {
      S.Diag(VD->getLocation(), diag::note_block_var_fixit_add_initialization)
          << VD->getDeclName()
          << FixItHint::CreateInsertion(VD->getLocation(), "__block ");
      return true;
    }
  
    // Don't issue a fixit if there is already an initializer.
    if (VD->getInit())
      return false;
  
    // Don't suggest a fixit inside macros.
    if (VD->getEndLoc().isMacroID())
      return false;
  
    SourceLocation Loc = S.getLocForEndOfToken(VD->getEndLoc());
  
    // Suggest possible initialization (if any).
    std::string Init = S.getFixItZeroInitializerForType(VariableTy, Loc);
    if (Init.empty())
      return false;
  
    S.Diag(Loc, diag::note_var_fixit_add_initialization) << VD->getDeclName()
      << FixItHint::CreateInsertion(Loc, Init);
    return true;
  }
  
  /// Create a fixit to remove an if-like statement, on the assumption that its
  /// condition is CondVal.
  static void CreateIfFixit(Sema &S, const Stmt *If, const Stmt *Then,
                            const Stmt *Else, bool CondVal,
                            FixItHint &Fixit1, FixItHint &Fixit2) {
    if (CondVal) {
      // If condition is always true, remove all but the 'then'.
      Fixit1 = FixItHint::CreateRemoval(
          CharSourceRange::getCharRange(If->getBeginLoc(), Then->getBeginLoc()));
      if (Else) {
        SourceLocation ElseKwLoc = S.getLocForEndOfToken(Then->getEndLoc());
        Fixit2 =
            FixItHint::CreateRemoval(SourceRange(ElseKwLoc, Else->getEndLoc()));
      }
    } else {
      // If condition is always false, remove all but the 'else'.
      if (Else)
        Fixit1 = FixItHint::CreateRemoval(CharSourceRange::getCharRange(
            If->getBeginLoc(), Else->getBeginLoc()));
      else
        Fixit1 = FixItHint::CreateRemoval(If->getSourceRange());
    }
  }
  
  /// DiagUninitUse -- Helper function to produce a diagnostic for an
  /// uninitialized use of a variable.
  static void DiagUninitUse(Sema &S, const VarDecl *VD, const UninitUse &Use,
                            bool IsCapturedByBlock) {
    bool Diagnosed = false;
  
    switch (Use.getKind()) {
    case UninitUse::Always:
      S.Diag(Use.getUser()->getBeginLoc(), diag::warn_uninit_var)
          << VD->getDeclName() << IsCapturedByBlock
          << Use.getUser()->getSourceRange();
      return;
  
    case UninitUse::AfterDecl:
    case UninitUse::AfterCall:
      S.Diag(VD->getLocation(), diag::warn_sometimes_uninit_var)
        << VD->getDeclName() << IsCapturedByBlock
        << (Use.getKind() == UninitUse::AfterDecl ? 4 : 5)
        << const_cast<DeclContext*>(VD->getLexicalDeclContext())
        << VD->getSourceRange();
      S.Diag(Use.getUser()->getBeginLoc(), diag::note_uninit_var_use)
          << IsCapturedByBlock << Use.getUser()->getSourceRange();
      return;
  
    case UninitUse::Maybe:
    case UninitUse::Sometimes:
      // Carry on to report sometimes-uninitialized branches, if possible,
      // or a 'may be used uninitialized' diagnostic otherwise.
      break;
    }
  
    // Diagnose each branch which leads to a sometimes-uninitialized use.
    for (UninitUse::branch_iterator I = Use.branch_begin(), E = Use.branch_end();
         I != E; ++I) {
      assert(Use.getKind() == UninitUse::Sometimes);
  
      const Expr *User = Use.getUser();
      const Stmt *Term = I->Terminator;
  
      // Information used when building the diagnostic.
      unsigned DiagKind;
      StringRef Str;
      SourceRange Range;
  
      // FixIts to suppress the diagnostic by removing the dead condition.
      // For all binary terminators, branch 0 is taken if the condition is true,
      // and branch 1 is taken if the condition is false.
      int RemoveDiagKind = -1;
      const char *FixitStr =
          S.getLangOpts().CPlusPlus ? (I->Output ? "true" : "false")
                                    : (I->Output ? "1" : "0");
      FixItHint Fixit1, Fixit2;
  
      switch (Term ? Term->getStmtClass() : Stmt::DeclStmtClass) {
      default:
        // Don't know how to report this. Just fall back to 'may be used
        // uninitialized'. FIXME: Can this happen?
        continue;
  
      // "condition is true / condition is false".
      case Stmt::IfStmtClass: {
        const IfStmt *IS = cast<IfStmt>(Term);
        DiagKind = 0;
        Str = "if";
        Range = IS->getCond()->getSourceRange();
        RemoveDiagKind = 0;
        CreateIfFixit(S, IS, IS->getThen(), IS->getElse(),
                      I->Output, Fixit1, Fixit2);
        break;
      }
      case Stmt::ConditionalOperatorClass: {
        const ConditionalOperator *CO = cast<ConditionalOperator>(Term);
        DiagKind = 0;
        Str = "?:";
        Range = CO->getCond()->getSourceRange();
        RemoveDiagKind = 0;
        CreateIfFixit(S, CO, CO->getTrueExpr(), CO->getFalseExpr(),
                      I->Output, Fixit1, Fixit2);
        break;
      }
      case Stmt::BinaryOperatorClass: {
        const BinaryOperator *BO = cast<BinaryOperator>(Term);
        if (!BO->isLogicalOp())
          continue;
        DiagKind = 0;
        Str = BO->getOpcodeStr();
        Range = BO->getLHS()->getSourceRange();
        RemoveDiagKind = 0;
        if ((BO->getOpcode() == BO_LAnd && I->Output) ||
            (BO->getOpcode() == BO_LOr && !I->Output))
          // true && y -> y, false || y -> y.
          Fixit1 = FixItHint::CreateRemoval(
              SourceRange(BO->getBeginLoc(), BO->getOperatorLoc()));
        else
          // false && y -> false, true || y -> true.
          Fixit1 = FixItHint::CreateReplacement(BO->getSourceRange(), FixitStr);
        break;
      }
  
      // "loop is entered / loop is exited".
      case Stmt::WhileStmtClass:
        DiagKind = 1;
        Str = "while";
        Range = cast<WhileStmt>(Term)->getCond()->getSourceRange();
        RemoveDiagKind = 1;
        Fixit1 = FixItHint::CreateReplacement(Range, FixitStr);
        break;
      case Stmt::ForStmtClass:
        DiagKind = 1;
        Str = "for";
        Range = cast<ForStmt>(Term)->getCond()->getSourceRange();
        RemoveDiagKind = 1;
        if (I->Output)
          Fixit1 = FixItHint::CreateRemoval(Range);
        else
          Fixit1 = FixItHint::CreateReplacement(Range, FixitStr);
        break;
      case Stmt::CXXForRangeStmtClass:
        if (I->Output == 1) {
          // The use occurs if a range-based for loop's body never executes.
          // That may be impossible, and there's no syntactic fix for this,
          // so treat it as a 'may be uninitialized' case.
          continue;
        }
        DiagKind = 1;
        Str = "for";
        Range = cast<CXXForRangeStmt>(Term)->getRangeInit()->getSourceRange();
        break;
  
      // "condition is true / loop is exited".
      case Stmt::DoStmtClass:
        DiagKind = 2;
        Str = "do";
        Range = cast<DoStmt>(Term)->getCond()->getSourceRange();
        RemoveDiagKind = 1;
        Fixit1 = FixItHint::CreateReplacement(Range, FixitStr);
        break;
  
      // "switch case is taken".
      case Stmt::CaseStmtClass:
        DiagKind = 3;
        Str = "case";
        Range = cast<CaseStmt>(Term)->getLHS()->getSourceRange();
        break;
      case Stmt::DefaultStmtClass:
        DiagKind = 3;
        Str = "default";
        Range = cast<DefaultStmt>(Term)->getDefaultLoc();
        break;
      }
  
      S.Diag(Range.getBegin(), diag::warn_sometimes_uninit_var)
        << VD->getDeclName() << IsCapturedByBlock << DiagKind
        << Str << I->Output << Range;
      S.Diag(User->getBeginLoc(), diag::note_uninit_var_use)
          << IsCapturedByBlock << User->getSourceRange();
      if (RemoveDiagKind != -1)
        S.Diag(Fixit1.RemoveRange.getBegin(), diag::note_uninit_fixit_remove_cond)
          << RemoveDiagKind << Str << I->Output << Fixit1 << Fixit2;
  
      Diagnosed = true;
    }
  
    if (!Diagnosed)
      S.Diag(Use.getUser()->getBeginLoc(), diag::warn_maybe_uninit_var)
          << VD->getDeclName() << IsCapturedByBlock
          << Use.getUser()->getSourceRange();
  }
  
  /// DiagnoseUninitializedUse -- Helper function for diagnosing uses of an
  /// uninitialized variable. This manages the different forms of diagnostic
  /// emitted for particular types of uses. Returns true if the use was diagnosed
  /// as a warning. If a particular use is one we omit warnings for, returns
  /// false.
  static bool DiagnoseUninitializedUse(Sema &S, const VarDecl *VD,
                                       const UninitUse &Use,
                                       bool alwaysReportSelfInit = false) {
    if (const DeclRefExpr *DRE = dyn_cast<DeclRefExpr>(Use.getUser())) {
      // Inspect the initializer of the variable declaration which is
      // being referenced prior to its initialization. We emit
      // specialized diagnostics for self-initialization, and we
      // specifically avoid warning about self references which take the
      // form of:
      //
      //   int x = x;
      //
      // This is used to indicate to GCC that 'x' is intentionally left
      // uninitialized. Proven code paths which access 'x' in
      // an uninitialized state after this will still warn.
      if (const Expr *Initializer = VD->getInit()) {
        if (!alwaysReportSelfInit && DRE == Initializer->IgnoreParenImpCasts())
          return false;
  
        ContainsReference CR(S.Context, DRE);
        CR.Visit(Initializer);
        if (CR.doesContainReference()) {
          S.Diag(DRE->getBeginLoc(), diag::warn_uninit_self_reference_in_init)
              << VD->getDeclName() << VD->getLocation() << DRE->getSourceRange();
          return true;
        }
      }
  
      DiagUninitUse(S, VD, Use, false);
    } else {
      const BlockExpr *BE = cast<BlockExpr>(Use.getUser());
      if (VD->getType()->isBlockPointerType() && !VD->hasAttr<BlocksAttr>())
        S.Diag(BE->getBeginLoc(),
               diag::warn_uninit_byref_blockvar_captured_by_block)
            << VD->getDeclName();
      else
        DiagUninitUse(S, VD, Use, true);
    }
  
    // Report where the variable was declared when the use wasn't within
    // the initializer of that declaration & we didn't already suggest
    // an initialization fixit.
    if (!SuggestInitializationFixit(S, VD))
      S.Diag(VD->getBeginLoc(), diag::note_var_declared_here)
          << VD->getDeclName();
  
    return true;
  }
  
  namespace {
    class FallthroughMapper : public RecursiveASTVisitor<FallthroughMapper> {
    public:
      FallthroughMapper(Sema &S)
        : FoundSwitchStatements(false),
          S(S) {
      }
  
      bool foundSwitchStatements() const { return FoundSwitchStatements; }
  
      void markFallthroughVisited(const AttributedStmt *Stmt) {
        bool Found = FallthroughStmts.erase(Stmt);
        assert(Found);
        (void)Found;
      }
  
      typedef llvm::SmallPtrSet<const AttributedStmt*, 8> AttrStmts;
  
      const AttrStmts &getFallthroughStmts() const {
        return FallthroughStmts;
      }
  
      void fillReachableBlocks(CFG *Cfg) {
        assert(ReachableBlocks.empty() && "ReachableBlocks already filled");
        std::deque<const CFGBlock *> BlockQueue;
  
        ReachableBlocks.insert(&Cfg->getEntry());
        BlockQueue.push_back(&Cfg->getEntry());
        // Mark all case blocks reachable to avoid problems with switching on
        // constants, covered enums, etc.
        // These blocks can contain fall-through annotations, and we don't want to
        // issue a warn_fallthrough_attr_unreachable for them.
        for (const auto *B : *Cfg) {
          const Stmt *L = B->getLabel();
          if (L && isa<SwitchCase>(L) && ReachableBlocks.insert(B).second)
            BlockQueue.push_back(B);
        }
  
        while (!BlockQueue.empty()) {
          const CFGBlock *P = BlockQueue.front();
          BlockQueue.pop_front();
          for (CFGBlock::const_succ_iterator I = P->succ_begin(),
                                             E = P->succ_end();
               I != E; ++I) {
            if (*I && ReachableBlocks.insert(*I).second)
              BlockQueue.push_back(*I);
          }
        }
      }
  
      bool checkFallThroughIntoBlock(const CFGBlock &B, int &AnnotatedCnt,
                                     bool IsTemplateInstantiation) {
        assert(!ReachableBlocks.empty() && "ReachableBlocks empty");
  
        int UnannotatedCnt = 0;
        AnnotatedCnt = 0;
  
        std::deque<const CFGBlock*> BlockQueue(B.pred_begin(), B.pred_end());
        while (!BlockQueue.empty()) {
          const CFGBlock *P = BlockQueue.front();
          BlockQueue.pop_front();
          if (!P) continue;
  
          const Stmt *Term = P->getTerminator();
          if (Term && isa<SwitchStmt>(Term))
            continue; // Switch statement, good.
  
          const SwitchCase *SW = dyn_cast_or_null<SwitchCase>(P->getLabel());
          if (SW && SW->getSubStmt() == B.getLabel() && P->begin() == P->end())
            continue; // Previous case label has no statements, good.
  
          const LabelStmt *L = dyn_cast_or_null<LabelStmt>(P->getLabel());
          if (L && L->getSubStmt() == B.getLabel() && P->begin() == P->end())
            continue; // Case label is preceded with a normal label, good.
  
          if (!ReachableBlocks.count(P)) {
            for (CFGBlock::const_reverse_iterator ElemIt = P->rbegin(),
                                                  ElemEnd = P->rend();
                 ElemIt != ElemEnd; ++ElemIt) {
              if (Optional<CFGStmt> CS = ElemIt->getAs<CFGStmt>()) {
                if (const AttributedStmt *AS = asFallThroughAttr(CS->getStmt())) {
                  // Don't issue a warning for an unreachable fallthrough
                  // attribute in template instantiations as it may not be
                  // unreachable in all instantiations of the template.
                  if (!IsTemplateInstantiation)
                    S.Diag(AS->getBeginLoc(),
                           diag::warn_fallthrough_attr_unreachable);
                  markFallthroughVisited(AS);
                  ++AnnotatedCnt;
                  break;
                }
                // Don't care about other unreachable statements.
              }
            }
            // If there are no unreachable statements, this may be a special
            // case in CFG:
            // case X: {
            //    A a;  // A has a destructor.
            //    break;
            // }
            // // <<<< This place is represented by a 'hanging' CFG block.
            // case Y:
            continue;
          }
  
          const Stmt *LastStmt = getLastStmt(*P);
          if (const AttributedStmt *AS = asFallThroughAttr(LastStmt)) {
            markFallthroughVisited(AS);
            ++AnnotatedCnt;
            continue; // Fallthrough annotation, good.
          }
  
          if (!LastStmt) { // This block contains no executable statements.
            // Traverse its predecessors.
            std::copy(P->pred_begin(), P->pred_end(),
                      std::back_inserter(BlockQueue));
            continue;
          }
  
          ++UnannotatedCnt;
        }
        return !!UnannotatedCnt;
      }
  
      // RecursiveASTVisitor setup.
      bool shouldWalkTypesOfTypeLocs() const { return false; }
  
      bool VisitAttributedStmt(AttributedStmt *S) {
        if (asFallThroughAttr(S))
          FallthroughStmts.insert(S);
        return true;
      }
  
      bool VisitSwitchStmt(SwitchStmt *S) {
        FoundSwitchStatements = true;
        return true;
      }
  
      // We don't want to traverse local type declarations. We analyze their
      // methods separately.
      bool TraverseDecl(Decl *D) { return true; }
  
      // We analyze lambda bodies separately. Skip them here.
      bool TraverseLambdaExpr(LambdaExpr *LE) {
        // Traverse the captures, but not the body.
        for (const auto &C : zip(LE->captures(), LE->capture_inits()))
          TraverseLambdaCapture(LE, &std::get<0>(C), std::get<1>(C));
        return true;
      }
  
    private:
  
      static const AttributedStmt *asFallThroughAttr(const Stmt *S) {
        if (const AttributedStmt *AS = dyn_cast_or_null<AttributedStmt>(S)) {
          if (hasSpecificAttr<FallThroughAttr>(AS->getAttrs()))
            return AS;
        }
        return nullptr;
      }
  
      static const Stmt *getLastStmt(const CFGBlock &B) {
        if (const Stmt *Term = B.getTerminator())
          return Term;
        for (CFGBlock::const_reverse_iterator ElemIt = B.rbegin(),
                                              ElemEnd = B.rend();
                                              ElemIt != ElemEnd; ++ElemIt) {
          if (Optional<CFGStmt> CS = ElemIt->getAs<CFGStmt>())
            return CS->getStmt();
        }
        // Workaround to detect a statement thrown out by CFGBuilder:
        //   case X: {} case Y:
        //   case X: ; case Y:
        if (const SwitchCase *SW = dyn_cast_or_null<SwitchCase>(B.getLabel()))
          if (!isa<SwitchCase>(SW->getSubStmt()))
            return SW->getSubStmt();
  
        return nullptr;
      }
  
      bool FoundSwitchStatements;
      AttrStmts FallthroughStmts;
      Sema &S;
      llvm::SmallPtrSet<const CFGBlock *, 16> ReachableBlocks;
    };
  } // anonymous namespace
  
  static StringRef getFallthroughAttrSpelling(Preprocessor &PP,
                                              SourceLocation Loc) {
    TokenValue FallthroughTokens[] = {
      tok::l_square, tok::l_square,
      PP.getIdentifierInfo("fallthrough"),
      tok::r_square, tok::r_square
    };
  
    TokenValue ClangFallthroughTokens[] = {
      tok::l_square, tok::l_square, PP.getIdentifierInfo("clang"),
      tok::coloncolon, PP.getIdentifierInfo("fallthrough"),
      tok::r_square, tok::r_square
    };
  
    bool PreferClangAttr = !PP.getLangOpts().CPlusPlus17;
  
    StringRef MacroName;
    if (PreferClangAttr)
      MacroName = PP.getLastMacroWithSpelling(Loc, ClangFallthroughTokens);
    if (MacroName.empty())
      MacroName = PP.getLastMacroWithSpelling(Loc, FallthroughTokens);
    if (MacroName.empty() && !PreferClangAttr)
      MacroName = PP.getLastMacroWithSpelling(Loc, ClangFallthroughTokens);
    if (MacroName.empty())
      MacroName = PreferClangAttr ? "[[clang::fallthrough]]" : "[[fallthrough]]";
    return MacroName;
  }
  
  static void DiagnoseSwitchLabelsFallthrough(Sema &S, AnalysisDeclContext &AC,
                                              bool PerFunction) {
    // Only perform this analysis when using [[]] attributes. There is no good
    // workflow for this warning when not using C++11. There is no good way to
    // silence the warning (no attribute is available) unless we are using
    // [[]] attributes. One could use pragmas to silence the warning, but as a
    // general solution that is gross and not in the spirit of this warning.
    //
    // NOTE: This an intermediate solution. There are on-going discussions on
    // how to properly support this warning outside of C++11 with an annotation.
    if (!AC.getASTContext().getLangOpts().DoubleSquareBracketAttributes)
      return;
  
    FallthroughMapper FM(S);
    FM.TraverseStmt(AC.getBody());
  
    if (!FM.foundSwitchStatements())
      return;
  
    if (PerFunction && FM.getFallthroughStmts().empty())
      return;
  
    CFG *Cfg = AC.getCFG();
  
    if (!Cfg)
      return;
  
    FM.fillReachableBlocks(Cfg);
  
    for (const CFGBlock *B : llvm::reverse(*Cfg)) {
      const Stmt *Label = B->getLabel();
  
      if (!Label || !isa<SwitchCase>(Label))
        continue;
  
      int AnnotatedCnt;
  
      bool IsTemplateInstantiation = false;
      if (const FunctionDecl *Function = dyn_cast<FunctionDecl>(AC.getDecl()))
        IsTemplateInstantiation = Function->isTemplateInstantiation();
      if (!FM.checkFallThroughIntoBlock(*B, AnnotatedCnt,
                                        IsTemplateInstantiation))
        continue;
  
      S.Diag(Label->getBeginLoc(),
             PerFunction ? diag::warn_unannotated_fallthrough_per_function
                         : diag::warn_unannotated_fallthrough);
  
      if (!AnnotatedCnt) {
        SourceLocation L = Label->getBeginLoc();
        if (L.isMacroID())
          continue;
        if (S.getLangOpts().CPlusPlus11) {
          const Stmt *Term = B->getTerminator();
          // Skip empty cases.
          while (B->empty() && !Term && B->succ_size() == 1) {
            B = *B->succ_begin();
            Term = B->getTerminator();
          }
          if (!(B->empty() && Term && isa<BreakStmt>(Term))) {
            Preprocessor &PP = S.getPreprocessor();
            StringRef AnnotationSpelling = getFallthroughAttrSpelling(PP, L);
            SmallString<64> TextToInsert(AnnotationSpelling);
            TextToInsert += "; ";
            S.Diag(L, diag::note_insert_fallthrough_fixit) <<
                AnnotationSpelling <<
                FixItHint::CreateInsertion(L, TextToInsert);
          }
        }
        S.Diag(L, diag::note_insert_break_fixit) <<
          FixItHint::CreateInsertion(L, "break; ");
      }
    }
  
    for (const auto *F : FM.getFallthroughStmts())
      S.Diag(F->getBeginLoc(), diag::err_fallthrough_attr_invalid_placement);
  }
  
  static bool isInLoop(const ASTContext &Ctx, const ParentMap &PM,
                       const Stmt *S) {
    assert(S);
  
    do {
      switch (S->getStmtClass()) {
      case Stmt::ForStmtClass:
      case Stmt::WhileStmtClass:
      case Stmt::CXXForRangeStmtClass:
      case Stmt::ObjCForCollectionStmtClass:
        return true;
      case Stmt::DoStmtClass: {
        Expr::EvalResult Result;
        if (!cast<DoStmt>(S)->getCond()->EvaluateAsInt(Result, Ctx))
          return true;
        return Result.Val.getInt().getBoolValue();
      }
      default:
        break;
      }
    } while ((S = PM.getParent(S)));
  
    return false;
  }
  
  static void diagnoseRepeatedUseOfWeak(Sema &S,
                                        const sema::FunctionScopeInfo *CurFn,
                                        const Decl *D,
                                        const ParentMap &PM) {
    typedef sema::FunctionScopeInfo::WeakObjectProfileTy WeakObjectProfileTy;
    typedef sema::FunctionScopeInfo::WeakObjectUseMap WeakObjectUseMap;
    typedef sema::FunctionScopeInfo::WeakUseVector WeakUseVector;
    typedef std::pair<const Stmt *, WeakObjectUseMap::const_iterator>
    StmtUsesPair;
  
    ASTContext &Ctx = S.getASTContext();
  
    const WeakObjectUseMap &WeakMap = CurFn->getWeakObjectUses();
  
    // Extract all weak objects that are referenced more than once.
    SmallVector<StmtUsesPair, 8> UsesByStmt;
    for (WeakObjectUseMap::const_iterator I = WeakMap.begin(), E = WeakMap.end();
         I != E; ++I) {
      const WeakUseVector &Uses = I->second;
  
      // Find the first read of the weak object.
      WeakUseVector::const_iterator UI = Uses.begin(), UE = Uses.end();
      for ( ; UI != UE; ++UI) {
        if (UI->isUnsafe())
          break;
      }
  
      // If there were only writes to this object, don't warn.
      if (UI == UE)
        continue;
  
      // If there was only one read, followed by any number of writes, and the
      // read is not within a loop, don't warn. Additionally, don't warn in a
      // loop if the base object is a local variable -- local variables are often
      // changed in loops.
      if (UI == Uses.begin()) {
        WeakUseVector::const_iterator UI2 = UI;
        for (++UI2; UI2 != UE; ++UI2)
          if (UI2->isUnsafe())
            break;
  
        if (UI2 == UE) {
          if (!isInLoop(Ctx, PM, UI->getUseExpr()))
            continue;
  
          const WeakObjectProfileTy &Profile = I->first;
          if (!Profile.isExactProfile())
            continue;
  
          const NamedDecl *Base = Profile.getBase();
          if (!Base)
            Base = Profile.getProperty();
          assert(Base && "A profile always has a base or property.");
  
          if (const VarDecl *BaseVar = dyn_cast<VarDecl>(Base))
            if (BaseVar->hasLocalStorage() && !isa<ParmVarDecl>(Base))
              continue;
        }
      }
  
      UsesByStmt.push_back(StmtUsesPair(UI->getUseExpr(), I));
    }
  
    if (UsesByStmt.empty())
      return;
  
    // Sort by first use so that we emit the warnings in a deterministic order.
    SourceManager &SM = S.getSourceManager();
    llvm::sort(UsesByStmt,
               [&SM](const StmtUsesPair &LHS, const StmtUsesPair &RHS) {
                 return SM.isBeforeInTranslationUnit(LHS.first->getBeginLoc(),
                                                     RHS.first->getBeginLoc());
               });
  
    // Classify the current code body for better warning text.
    // This enum should stay in sync with the cases in
    // warn_arc_repeated_use_of_weak and warn_arc_possible_repeated_use_of_weak.
    // FIXME: Should we use a common classification enum and the same set of
    // possibilities all throughout Sema?
    enum {
      Function,
      Method,
      Block,
      Lambda
    } FunctionKind;
  
    if (isa<sema::BlockScopeInfo>(CurFn))
      FunctionKind = Block;
    else if (isa<sema::LambdaScopeInfo>(CurFn))
      FunctionKind = Lambda;
    else if (isa<ObjCMethodDecl>(D))
      FunctionKind = Method;
    else
      FunctionKind = Function;
  
    // Iterate through the sorted problems and emit warnings for each.
    for (const auto &P : UsesByStmt) {
      const Stmt *FirstRead = P.first;
      const WeakObjectProfileTy &Key = P.second->first;
      const WeakUseVector &Uses = P.second->second;
  
      // For complicated expressions like 'a.b.c' and 'x.b.c', WeakObjectProfileTy
      // may not contain enough information to determine that these are different
      // properties. We can only be 100% sure of a repeated use in certain cases,
      // and we adjust the diagnostic kind accordingly so that the less certain
      // case can be turned off if it is too noisy.
      unsigned DiagKind;
      if (Key.isExactProfile())
        DiagKind = diag::warn_arc_repeated_use_of_weak;
      else
        DiagKind = diag::warn_arc_possible_repeated_use_of_weak;
  
      // Classify the weak object being accessed for better warning text.
      // This enum should stay in sync with the cases in
      // warn_arc_repeated_use_of_weak and warn_arc_possible_repeated_use_of_weak.
      enum {
        Variable,
        Property,
        ImplicitProperty,
        Ivar
      } ObjectKind;
  
      const NamedDecl *KeyProp = Key.getProperty();
      if (isa<VarDecl>(KeyProp))
        ObjectKind = Variable;
      else if (isa<ObjCPropertyDecl>(KeyProp))
        ObjectKind = Property;
      else if (isa<ObjCMethodDecl>(KeyProp))
        ObjectKind = ImplicitProperty;
      else if (isa<ObjCIvarDecl>(KeyProp))
        ObjectKind = Ivar;
      else
        llvm_unreachable("Unexpected weak object kind!");
  
      // Do not warn about IBOutlet weak property receivers being set to null
      // since they are typically only used from the main thread.
      if (const ObjCPropertyDecl *Prop = dyn_cast<ObjCPropertyDecl>(KeyProp))
        if (Prop->hasAttr<IBOutletAttr>())
          continue;
  
      // Show the first time the object was read.
      S.Diag(FirstRead->getBeginLoc(), DiagKind)
          << int(ObjectKind) << KeyProp << int(FunctionKind)
          << FirstRead->getSourceRange();
  
      // Print all the other accesses as notes.
      for (const auto &Use : Uses) {
        if (Use.getUseExpr() == FirstRead)
          continue;
        S.Diag(Use.getUseExpr()->getBeginLoc(),
               diag::note_arc_weak_also_accessed_here)
            << Use.getUseExpr()->getSourceRange();
      }
    }
  }
  
  namespace {
  class UninitValsDiagReporter : public UninitVariablesHandler {
    Sema &S;
    typedef SmallVector<UninitUse, 2> UsesVec;
    typedef llvm::PointerIntPair<UsesVec *, 1, bool> MappedType;
    // Prefer using MapVector to DenseMap, so that iteration order will be
    // the same as insertion order. This is needed to obtain a deterministic
    // order of diagnostics when calling flushDiagnostics().
    typedef llvm::MapVector<const VarDecl *, MappedType> UsesMap;
    UsesMap uses;
  
  public:
    UninitValsDiagReporter(Sema &S) : S(S) {}
    ~UninitValsDiagReporter() override { flushDiagnostics(); }
  
    MappedType &getUses(const VarDecl *vd) {
      MappedType &V = uses[vd];
      if (!V.getPointer())
        V.setPointer(new UsesVec());
      return V;
    }
  
    void handleUseOfUninitVariable(const VarDecl *vd,
                                   const UninitUse &use) override {
      getUses(vd).getPointer()->push_back(use);
    }
  
    void handleSelfInit(const VarDecl *vd) override {
      getUses(vd).setInt(true);
    }
  
    void flushDiagnostics() {
      for (const auto &P : uses) {
        const VarDecl *vd = P.first;
        const MappedType &V = P.second;
  
        UsesVec *vec = V.getPointer();
        bool hasSelfInit = V.getInt();
  
        // Specially handle the case where we have uses of an uninitialized
        // variable, but the root cause is an idiomatic self-init.  We want
        // to report the diagnostic at the self-init since that is the root cause.
        if (!vec->empty() && hasSelfInit && hasAlwaysUninitializedUse(vec))
          DiagnoseUninitializedUse(S, vd,
                                   UninitUse(vd->getInit()->IgnoreParenCasts(),
                                             /* isAlwaysUninit */ true),
                                   /* alwaysReportSelfInit */ true);
        else {
          // Sort the uses by their SourceLocations.  While not strictly
          // guaranteed to produce them in line/column order, this will provide
          // a stable ordering.
          llvm::sort(vec->begin(), vec->end(),
                     [](const UninitUse &a, const UninitUse &b) {
            // Prefer a more confident report over a less confident one.
            if (a.getKind() != b.getKind())
              return a.getKind() > b.getKind();
            return a.getUser()->getBeginLoc() < b.getUser()->getBeginLoc();
          });
  
          for (const auto &U : *vec) {
            // If we have self-init, downgrade all uses to 'may be uninitialized'.
            UninitUse Use = hasSelfInit ? UninitUse(U.getUser(), false) : U;
  
            if (DiagnoseUninitializedUse(S, vd, Use))
              // Skip further diagnostics for this variable. We try to warn only
              // on the first point at which a variable is used uninitialized.
              break;
          }
        }
  
        // Release the uses vector.
        delete vec;
      }
  
      uses.clear();
    }
  
  private:
    static bool hasAlwaysUninitializedUse(const UsesVec* vec) {
      return std::any_of(vec->begin(), vec->end(), [](const UninitUse &U) {
        return U.getKind() == UninitUse::Always ||
               U.getKind() == UninitUse::AfterCall ||
               U.getKind() == UninitUse::AfterDecl;
      });
    }
  };
  } // anonymous namespace
  
  namespace clang {
  namespace {
  typedef SmallVector<PartialDiagnosticAt, 1> OptionalNotes;
  typedef std::pair<PartialDiagnosticAt, OptionalNotes> DelayedDiag;
  typedef std::list<DelayedDiag> DiagList;
  
  struct SortDiagBySourceLocation {
    SourceManager &SM;
    SortDiagBySourceLocation(SourceManager &SM) : SM(SM) {}
  
    bool operator()(const DelayedDiag &left, const DelayedDiag &right) {
      // Although this call will be slow, this is only called when outputting
      // multiple warnings.
      return SM.isBeforeInTranslationUnit(left.first.first, right.first.first);
    }
  };
  } // anonymous namespace
  } // namespace clang
  
  //===----------------------------------------------------------------------===//
  // -Wthread-safety
  //===----------------------------------------------------------------------===//
  namespace clang {
  namespace threadSafety {
  namespace {
  class ThreadSafetyReporter : public clang::threadSafety::ThreadSafetyHandler {
    Sema &S;
    DiagList Warnings;
    SourceLocation FunLocation, FunEndLocation;
  
    const FunctionDecl *CurrentFunction;
    bool Verbose;
  
    OptionalNotes getNotes() const {
      if (Verbose && CurrentFunction) {
        PartialDiagnosticAt FNote(CurrentFunction->getBody()->getBeginLoc(),
                                  S.PDiag(diag::note_thread_warning_in_fun)
                                      << CurrentFunction);
        return OptionalNotes(1, FNote);
      }
      return OptionalNotes();
    }
  
    OptionalNotes getNotes(const PartialDiagnosticAt &Note) const {
      OptionalNotes ONS(1, Note);
      if (Verbose && CurrentFunction) {
        PartialDiagnosticAt FNote(CurrentFunction->getBody()->getBeginLoc(),
                                  S.PDiag(diag::note_thread_warning_in_fun)
                                      << CurrentFunction);
        ONS.push_back(std::move(FNote));
      }
      return ONS;
    }
  
    OptionalNotes getNotes(const PartialDiagnosticAt &Note1,
                           const PartialDiagnosticAt &Note2) const {
      OptionalNotes ONS;
      ONS.push_back(Note1);
      ONS.push_back(Note2);
      if (Verbose && CurrentFunction) {
        PartialDiagnosticAt FNote(CurrentFunction->getBody()->getBeginLoc(),
                                  S.PDiag(diag::note_thread_warning_in_fun)
                                      << CurrentFunction);
        ONS.push_back(std::move(FNote));
      }
      return ONS;
    }
  
    OptionalNotes makeLockedHereNote(SourceLocation LocLocked, StringRef Kind) {
      return LocLocked.isValid()
                 ? getNotes(PartialDiagnosticAt(
                       LocLocked, S.PDiag(diag::note_locked_here) << Kind))
                 : getNotes();
    }
  
   public:
    ThreadSafetyReporter(Sema &S, SourceLocation FL, SourceLocation FEL)
      : S(S), FunLocation(FL), FunEndLocation(FEL),
        CurrentFunction(nullptr), Verbose(false) {}
  
    void setVerbose(bool b) { Verbose = b; }
  
    /// Emit all buffered diagnostics in order of sourcelocation.
    /// We need to output diagnostics produced while iterating through
    /// the lockset in deterministic order, so this function orders diagnostics
    /// and outputs them.
    void emitDiagnostics() {
      Warnings.sort(SortDiagBySourceLocation(S.getSourceManager()));
      for (const auto &Diag : Warnings) {
        S.Diag(Diag.first.first, Diag.first.second);
        for (const auto &Note : Diag.second)
          S.Diag(Note.first, Note.second);
      }
    }
  
    void handleInvalidLockExp(StringRef Kind, SourceLocation Loc) override {
      PartialDiagnosticAt Warning(Loc, S.PDiag(diag::warn_cannot_resolve_lock)
                                           << Loc);
      Warnings.emplace_back(std::move(Warning), getNotes());
    }
  
    void handleUnmatchedUnlock(StringRef Kind, Name LockName,
                               SourceLocation Loc) override {
      if (Loc.isInvalid())
        Loc = FunLocation;
      PartialDiagnosticAt Warning(Loc, S.PDiag(diag::warn_unlock_but_no_lock)
                                           << Kind << LockName);
      Warnings.emplace_back(std::move(Warning), getNotes());
    }
  
    void handleIncorrectUnlockKind(StringRef Kind, Name LockName,
                                   LockKind Expected, LockKind Received,
                                   SourceLocation LocLocked,
                                   SourceLocation LocUnlock) override {
      if (LocUnlock.isInvalid())
        LocUnlock = FunLocation;
      PartialDiagnosticAt Warning(
          LocUnlock, S.PDiag(diag::warn_unlock_kind_mismatch)
                         << Kind << LockName << Received << Expected);
      Warnings.emplace_back(std::move(Warning),
                            makeLockedHereNote(LocLocked, Kind));
    }
  
    void handleDoubleLock(StringRef Kind, Name LockName, SourceLocation LocLocked,
                          SourceLocation LocDoubleLock) override {
      if (LocDoubleLock.isInvalid())
        LocDoubleLock = FunLocation;
      PartialDiagnosticAt Warning(LocDoubleLock, S.PDiag(diag::warn_double_lock)
                                                     << Kind << LockName);
      Warnings.emplace_back(std::move(Warning),
                            makeLockedHereNote(LocLocked, Kind));
    }
  
    void handleMutexHeldEndOfScope(StringRef Kind, Name LockName,
                                   SourceLocation LocLocked,
                                   SourceLocation LocEndOfScope,
                                   LockErrorKind LEK) override {
      unsigned DiagID = 0;
      switch (LEK) {
        case LEK_LockedSomePredecessors:
          DiagID = diag::warn_lock_some_predecessors;
          break;
        case LEK_LockedSomeLoopIterations:
          DiagID = diag::warn_expecting_lock_held_on_loop;
          break;
        case LEK_LockedAtEndOfFunction:
          DiagID = diag::warn_no_unlock;
          break;
        case LEK_NotLockedAtEndOfFunction:
          DiagID = diag::warn_expecting_locked;
          break;
      }
      if (LocEndOfScope.isInvalid())
        LocEndOfScope = FunEndLocation;
  
      PartialDiagnosticAt Warning(LocEndOfScope, S.PDiag(DiagID) << Kind
                                                                 << LockName);
      Warnings.emplace_back(std::move(Warning),
                            makeLockedHereNote(LocLocked, Kind));
    }
  
    void handleExclusiveAndShared(StringRef Kind, Name LockName,
                                  SourceLocation Loc1,
                                  SourceLocation Loc2) override {
      PartialDiagnosticAt Warning(Loc1,
                                  S.PDiag(diag::warn_lock_exclusive_and_shared)
                                      << Kind << LockName);
      PartialDiagnosticAt Note(Loc2, S.PDiag(diag::note_lock_exclusive_and_shared)
                                         << Kind << LockName);
      Warnings.emplace_back(std::move(Warning), getNotes(Note));
    }
  
    void handleNoMutexHeld(StringRef Kind, const NamedDecl *D,
                           ProtectedOperationKind POK, AccessKind AK,
                           SourceLocation Loc) override {
      assert((POK == POK_VarAccess || POK == POK_VarDereference) &&
             "Only works for variables");
      unsigned DiagID = POK == POK_VarAccess?
                          diag::warn_variable_requires_any_lock:
                          diag::warn_var_deref_requires_any_lock;
      PartialDiagnosticAt Warning(Loc, S.PDiag(DiagID)
        << D << getLockKindFromAccessKind(AK));
      Warnings.emplace_back(std::move(Warning), getNotes());
    }
  
    void handleMutexNotHeld(StringRef Kind, const NamedDecl *D,
                            ProtectedOperationKind POK, Name LockName,
                            LockKind LK, SourceLocation Loc,
                            Name *PossibleMatch) override {
      unsigned DiagID = 0;
      if (PossibleMatch) {
        switch (POK) {
          case POK_VarAccess:
            DiagID = diag::warn_variable_requires_lock_precise;
            break;
          case POK_VarDereference:
            DiagID = diag::warn_var_deref_requires_lock_precise;
            break;
          case POK_FunctionCall:
            DiagID = diag::warn_fun_requires_lock_precise;
            break;
          case POK_PassByRef:
            DiagID = diag::warn_guarded_pass_by_reference;
            break;
          case POK_PtPassByRef:
            DiagID = diag::warn_pt_guarded_pass_by_reference;
            break;
        }
        PartialDiagnosticAt Warning(Loc, S.PDiag(DiagID) << Kind
                                                         << D
                                                         << LockName << LK);
        PartialDiagnosticAt Note(Loc, S.PDiag(diag::note_found_mutex_near_match)
                                          << *PossibleMatch);
        if (Verbose && POK == POK_VarAccess) {
          PartialDiagnosticAt VNote(D->getLocation(),
                                   S.PDiag(diag::note_guarded_by_declared_here)
                                       << D->getNameAsString());
          Warnings.emplace_back(std::move(Warning), getNotes(Note, VNote));
        } else
          Warnings.emplace_back(std::move(Warning), getNotes(Note));
      } else {
        switch (POK) {
          case POK_VarAccess:
            DiagID = diag::warn_variable_requires_lock;
            break;
          case POK_VarDereference:
            DiagID = diag::warn_var_deref_requires_lock;
            break;
          case POK_FunctionCall:
            DiagID = diag::warn_fun_requires_lock;
            break;
          case POK_PassByRef:
            DiagID = diag::warn_guarded_pass_by_reference;
            break;
          case POK_PtPassByRef:
            DiagID = diag::warn_pt_guarded_pass_by_reference;
            break;
        }
        PartialDiagnosticAt Warning(Loc, S.PDiag(DiagID) << Kind
                                                         << D
                                                         << LockName << LK);
        if (Verbose && POK == POK_VarAccess) {
          PartialDiagnosticAt Note(D->getLocation(),
                                   S.PDiag(diag::note_guarded_by_declared_here));
          Warnings.emplace_back(std::move(Warning), getNotes(Note));
        } else
          Warnings.emplace_back(std::move(Warning), getNotes());
      }
    }
  
    void handleNegativeNotHeld(StringRef Kind, Name LockName, Name Neg,
                               SourceLocation Loc) override {
      PartialDiagnosticAt Warning(Loc,
          S.PDiag(diag::warn_acquire_requires_negative_cap)
          << Kind << LockName << Neg);
      Warnings.emplace_back(std::move(Warning), getNotes());
    }
  
    void handleFunExcludesLock(StringRef Kind, Name FunName, Name LockName,
                               SourceLocation Loc) override {
      PartialDiagnosticAt Warning(Loc, S.PDiag(diag::warn_fun_excludes_mutex)
                                           << Kind << FunName << LockName);
      Warnings.emplace_back(std::move(Warning), getNotes());
    }
  
    void handleLockAcquiredBefore(StringRef Kind, Name L1Name, Name L2Name,
                                  SourceLocation Loc) override {
      PartialDiagnosticAt Warning(Loc,
        S.PDiag(diag::warn_acquired_before) << Kind << L1Name << L2Name);
      Warnings.emplace_back(std::move(Warning), getNotes());
    }
  
    void handleBeforeAfterCycle(Name L1Name, SourceLocation Loc) override {
      PartialDiagnosticAt Warning(Loc,
        S.PDiag(diag::warn_acquired_before_after_cycle) << L1Name);
      Warnings.emplace_back(std::move(Warning), getNotes());
    }
  
    void enterFunction(const FunctionDecl* FD) override {
      CurrentFunction = FD;
    }
  
    void leaveFunction(const FunctionDecl* FD) override {
      CurrentFunction = nullptr;
    }
  };
  } // anonymous namespace
  } // namespace threadSafety
  } // namespace clang
  
  //===----------------------------------------------------------------------===//
  // -Wconsumed
  //===----------------------------------------------------------------------===//
  
  namespace clang {
  namespace consumed {
  namespace {
  class ConsumedWarningsHandler : public ConsumedWarningsHandlerBase {
  
    Sema &S;
    DiagList Warnings;
  
  public:
  
    ConsumedWarningsHandler(Sema &S) : S(S) {}
  
    void emitDiagnostics() override {
      Warnings.sort(SortDiagBySourceLocation(S.getSourceManager()));
      for (const auto &Diag : Warnings) {
        S.Diag(Diag.first.first, Diag.first.second);
        for (const auto &Note : Diag.second)
          S.Diag(Note.first, Note.second);
      }
    }
  
    void warnLoopStateMismatch(SourceLocation Loc,
                               StringRef VariableName) override {
      PartialDiagnosticAt Warning(Loc, S.PDiag(diag::warn_loop_state_mismatch) <<
        VariableName);
  
      Warnings.emplace_back(std::move(Warning), OptionalNotes());
    }
  
    void warnParamReturnTypestateMismatch(SourceLocation Loc,
                                          StringRef VariableName,
                                          StringRef ExpectedState,
                                          StringRef ObservedState) override {
  
      PartialDiagnosticAt Warning(Loc, S.PDiag(
        diag::warn_param_return_typestate_mismatch) << VariableName <<
          ExpectedState << ObservedState);
  
      Warnings.emplace_back(std::move(Warning), OptionalNotes());
    }
  
    void warnParamTypestateMismatch(SourceLocation Loc, StringRef ExpectedState,
                                    StringRef ObservedState) override {
  
      PartialDiagnosticAt Warning(Loc, S.PDiag(
        diag::warn_param_typestate_mismatch) << ExpectedState << ObservedState);
  
      Warnings.emplace_back(std::move(Warning), OptionalNotes());
    }
  
    void warnReturnTypestateForUnconsumableType(SourceLocation Loc,
                                                StringRef TypeName) override {
      PartialDiagnosticAt Warning(Loc, S.PDiag(
        diag::warn_return_typestate_for_unconsumable_type) << TypeName);
  
      Warnings.emplace_back(std::move(Warning), OptionalNotes());
    }
  
    void warnReturnTypestateMismatch(SourceLocation Loc, StringRef ExpectedState,
                                     StringRef ObservedState) override {
  
      PartialDiagnosticAt Warning(Loc, S.PDiag(
        diag::warn_return_typestate_mismatch) << ExpectedState << ObservedState);
  
      Warnings.emplace_back(std::move(Warning), OptionalNotes());
    }
  
    void warnUseOfTempInInvalidState(StringRef MethodName, StringRef State,
                                     SourceLocation Loc) override {
  
      PartialDiagnosticAt Warning(Loc, S.PDiag(
        diag::warn_use_of_temp_in_invalid_state) << MethodName << State);
  
      Warnings.emplace_back(std::move(Warning), OptionalNotes());
    }
  
    void warnUseInInvalidState(StringRef MethodName, StringRef VariableName,
                               StringRef State, SourceLocation Loc) override {
  
      PartialDiagnosticAt Warning(Loc, S.PDiag(diag::warn_use_in_invalid_state) <<
                                  MethodName << VariableName << State);
  
      Warnings.emplace_back(std::move(Warning), OptionalNotes());
    }
  };
  } // anonymous namespace
  } // namespace consumed
  } // namespace clang
  
  //===----------------------------------------------------------------------===//
  // AnalysisBasedWarnings - Worker object used by Sema to execute analysis-based
  //  warnings on a function, method, or block.
  //===----------------------------------------------------------------------===//
  
  clang::sema::AnalysisBasedWarnings::Policy::Policy() {
    enableCheckFallThrough = 1;
    enableCheckUnreachable = 0;
    enableThreadSafetyAnalysis = 0;
    enableConsumedAnalysis = 0;
  }
  
  static unsigned isEnabled(DiagnosticsEngine &D, unsigned diag) {
    return (unsigned)!D.isIgnored(diag, SourceLocation());
  }
  
  clang::sema::AnalysisBasedWarnings::AnalysisBasedWarnings(Sema &s)
    : S(s),
      NumFunctionsAnalyzed(0),
      NumFunctionsWithBadCFGs(0),
      NumCFGBlocks(0),
      MaxCFGBlocksPerFunction(0),
      NumUninitAnalysisFunctions(0),
      NumUninitAnalysisVariables(0),
      MaxUninitAnalysisVariablesPerFunction(0),
      NumUninitAnalysisBlockVisits(0),
      MaxUninitAnalysisBlockVisitsPerFunction(0) {
  
    using namespace diag;
    DiagnosticsEngine &D = S.getDiagnostics();
  
    DefaultPolicy.enableCheckUnreachable =
      isEnabled(D, warn_unreachable) ||
      isEnabled(D, warn_unreachable_break) ||
      isEnabled(D, warn_unreachable_return) ||
      isEnabled(D, warn_unreachable_loop_increment);
  
    DefaultPolicy.enableThreadSafetyAnalysis =
      isEnabled(D, warn_double_lock);
  
    DefaultPolicy.enableConsumedAnalysis =
      isEnabled(D, warn_use_in_invalid_state);
  }
  
  static void flushDiagnostics(Sema &S, const sema::FunctionScopeInfo *fscope) {
    for (const auto &D : fscope->PossiblyUnreachableDiags)
      S.Diag(D.Loc, D.PD);
  }
  
  void clang::sema::
  AnalysisBasedWarnings::IssueWarnings(sema::AnalysisBasedWarnings::Policy P,
                                       sema::FunctionScopeInfo *fscope,
                                       const Decl *D, const BlockExpr *blkExpr) {
  
    // We avoid doing analysis-based warnings when there are errors for
    // two reasons:
    // (1) The CFGs often can't be constructed (if the body is invalid), so
    //     don't bother trying.
    // (2) The code already has problems; running the analysis just takes more
    //     time.
    DiagnosticsEngine &Diags = S.getDiagnostics();
  
    // Do not do any analysis if we are going to just ignore them.
    if (Diags.getIgnoreAllWarnings() ||
        (Diags.getSuppressSystemWarnings() &&
         S.SourceMgr.isInSystemHeader(D->getLocation())))
      return;
  
    // For code in dependent contexts, we'll do this at instantiation time.
    if (cast<DeclContext>(D)->isDependentContext())
      return;
  
    if (Diags.hasUncompilableErrorOccurred()) {
      // Flush out any possibly unreachable diagnostics.
      flushDiagnostics(S, fscope);
      return;
    }
  
    const Stmt *Body = D->getBody();
    assert(Body);
  
    // Construct the analysis context with the specified CFG build options.
    AnalysisDeclContext AC(/* AnalysisDeclContextManager */ nullptr, D);
  
    // Don't generate EH edges for CallExprs as we'd like to avoid the n^2
    // explosion for destructors that can result and the compile time hit.
    AC.getCFGBuildOptions().PruneTriviallyFalseEdges = true;
    AC.getCFGBuildOptions().AddEHEdges = false;
    AC.getCFGBuildOptions().AddInitializers = true;
    AC.getCFGBuildOptions().AddImplicitDtors = true;
    AC.getCFGBuildOptions().AddTemporaryDtors = true;
    AC.getCFGBuildOptions().AddCXXNewAllocator = false;
    AC.getCFGBuildOptions().AddCXXDefaultInitExprInCtors = true;
  
    // Force that certain expressions appear as CFGElements in the CFG.  This
    // is used to speed up various analyses.
    // FIXME: This isn't the right factoring.  This is here for initial
    // prototyping, but we need a way for analyses to say what expressions they
    // expect to always be CFGElements and then fill in the BuildOptions
    // appropriately.  This is essentially a layering violation.
    if (P.enableCheckUnreachable || P.enableThreadSafetyAnalysis ||
        P.enableConsumedAnalysis) {
      // Unreachable code analysis and thread safety require a linearized CFG.
      AC.getCFGBuildOptions().setAllAlwaysAdd();
    }
    else {
      AC.getCFGBuildOptions()
        .setAlwaysAdd(Stmt::BinaryOperatorClass)
        .setAlwaysAdd(Stmt::CompoundAssignOperatorClass)
        .setAlwaysAdd(Stmt::BlockExprClass)
        .setAlwaysAdd(Stmt::CStyleCastExprClass)
        .setAlwaysAdd(Stmt::DeclRefExprClass)
        .setAlwaysAdd(Stmt::ImplicitCastExprClass)
        .setAlwaysAdd(Stmt::UnaryOperatorClass)
        .setAlwaysAdd(Stmt::AttributedStmtClass);
    }
  
    // Install the logical handler for -Wtautological-overlap-compare
    llvm::Optional<LogicalErrorHandler> LEH;
    if (!Diags.isIgnored(diag::warn_tautological_overlap_comparison,
                         D->getBeginLoc())) {
      LEH.emplace(S);
      AC.getCFGBuildOptions().Observer = &*LEH;
    }
  
    // Emit delayed diagnostics.
    if (!fscope->PossiblyUnreachableDiags.empty()) {
      bool analyzed = false;
  
      // Register the expressions with the CFGBuilder.
      for (const auto &D : fscope->PossiblyUnreachableDiags) {
        if (D.stmt)
          AC.registerForcedBlockExpression(D.stmt);
      }
  
      if (AC.getCFG()) {
        analyzed = true;
        for (const auto &D : fscope->PossiblyUnreachableDiags) {
          bool processed = false;
          if (D.stmt) {
            const CFGBlock *block = AC.getBlockForRegisteredExpression(D.stmt);
            CFGReverseBlockReachabilityAnalysis *cra =
                AC.getCFGReachablityAnalysis();
            // FIXME: We should be able to assert that block is non-null, but
            // the CFG analysis can skip potentially-evaluated expressions in
            // edge cases; see test/Sema/vla-2.c.
            if (block && cra) {
              // Can this block be reached from the entrance?
              if (cra->isReachable(&AC.getCFG()->getEntry(), block))
                S.Diag(D.Loc, D.PD);
              processed = true;
            }
          }
          if (!processed) {
            // Emit the warning anyway if we cannot map to a basic block.
            S.Diag(D.Loc, D.PD);
          }
        }
      }
  
      if (!analyzed)
        flushDiagnostics(S, fscope);
    }
  
    // Warning: check missing 'return'
    if (P.enableCheckFallThrough) {
      const CheckFallThroughDiagnostics &CD =
          (isa<BlockDecl>(D)
               ? CheckFallThroughDiagnostics::MakeForBlock()
               : (isa<CXXMethodDecl>(D) &&
                  cast<CXXMethodDecl>(D)->getOverloadedOperator() == OO_Call &&
                  cast<CXXMethodDecl>(D)->getParent()->isLambda())
                     ? CheckFallThroughDiagnostics::MakeForLambda()
                     : (fscope->isCoroutine()
                            ? CheckFallThroughDiagnostics::MakeForCoroutine(D)
                            : CheckFallThroughDiagnostics::MakeForFunction(D)));
      CheckFallThroughForBody(S, D, Body, blkExpr, CD, AC, fscope);
    }
  
    // Warning: check for unreachable code
    if (P.enableCheckUnreachable) {
      // Only check for unreachable code on non-template instantiations.
      // Different template instantiations can effectively change the control-flow
      // and it is very difficult to prove that a snippet of code in a template
      // is unreachable for all instantiations.
      bool isTemplateInstantiation = false;
      if (const FunctionDecl *Function = dyn_cast<FunctionDecl>(D))
        isTemplateInstantiation = Function->isTemplateInstantiation();
      if (!isTemplateInstantiation)
        CheckUnreachable(S, AC);
    }
  
    // Check for thread safety violations
    if (P.enableThreadSafetyAnalysis) {
      SourceLocation FL = AC.getDecl()->getLocation();
      SourceLocation FEL = AC.getDecl()->getEndLoc();
      threadSafety::ThreadSafetyReporter Reporter(S, FL, FEL);
      if (!Diags.isIgnored(diag::warn_thread_safety_beta, D->getBeginLoc()))
        Reporter.setIssueBetaWarnings(true);
      if (!Diags.isIgnored(diag::warn_thread_safety_verbose, D->getBeginLoc()))
        Reporter.setVerbose(true);
  
      threadSafety::runThreadSafetyAnalysis(AC, Reporter,
                                            &S.ThreadSafetyDeclCache);
      Reporter.emitDiagnostics();
    }
  
    // Check for violations of consumed properties.
    if (P.enableConsumedAnalysis) {
      consumed::ConsumedWarningsHandler WarningHandler(S);
      consumed::ConsumedAnalyzer Analyzer(WarningHandler);
      Analyzer.run(AC);
    }
  
    if (!Diags.isIgnored(diag::warn_uninit_var, D->getBeginLoc()) ||
        !Diags.isIgnored(diag::warn_sometimes_uninit_var, D->getBeginLoc()) ||
        !Diags.isIgnored(diag::warn_maybe_uninit_var, D->getBeginLoc())) {
      if (CFG *cfg = AC.getCFG()) {
        UninitValsDiagReporter reporter(S);
        UninitVariablesAnalysisStats stats;
        std::memset(&stats, 0, sizeof(UninitVariablesAnalysisStats));
        runUninitializedVariablesAnalysis(*cast<DeclContext>(D), *cfg, AC,
                                          reporter, stats);
  
        if (S.CollectStats && stats.NumVariablesAnalyzed > 0) {
          ++NumUninitAnalysisFunctions;
          NumUninitAnalysisVariables += stats.NumVariablesAnalyzed;
          NumUninitAnalysisBlockVisits += stats.NumBlockVisits;
          MaxUninitAnalysisVariablesPerFunction =
              std::max(MaxUninitAnalysisVariablesPerFunction,
                       stats.NumVariablesAnalyzed);
          MaxUninitAnalysisBlockVisitsPerFunction =
              std::max(MaxUninitAnalysisBlockVisitsPerFunction,
                       stats.NumBlockVisits);
        }
      }
    }
  
    bool FallThroughDiagFull =
        !Diags.isIgnored(diag::warn_unannotated_fallthrough, D->getBeginLoc());
    bool FallThroughDiagPerFunction = !Diags.isIgnored(
        diag::warn_unannotated_fallthrough_per_function, D->getBeginLoc());
    if (FallThroughDiagFull || FallThroughDiagPerFunction ||
        fscope->HasFallthroughStmt) {
      DiagnoseSwitchLabelsFallthrough(S, AC, !FallThroughDiagFull);
    }
  
    if (S.getLangOpts().ObjCWeak &&
        !Diags.isIgnored(diag::warn_arc_repeated_use_of_weak, D->getBeginLoc()))
      diagnoseRepeatedUseOfWeak(S, fscope, D, AC.getParentMap());
  
  
    // Check for infinite self-recursion in functions
    if (!Diags.isIgnored(diag::warn_infinite_recursive_function,
                         D->getBeginLoc())) {
      if (const FunctionDecl *FD = dyn_cast<FunctionDecl>(D)) {
        checkRecursiveFunction(S, FD, Body, AC);
      }
    }
  
    // Check for throw out of non-throwing function.
    if (!Diags.isIgnored(diag::warn_throw_in_noexcept_func, D->getBeginLoc()))
      if (const FunctionDecl *FD = dyn_cast<FunctionDecl>(D))
        if (S.getLangOpts().CPlusPlus && isNoexcept(FD))
          checkThrowInNonThrowingFunc(S, FD, AC);
  
    // If none of the previous checks caused a CFG build, trigger one here
    // for -Wtautological-overlap-compare
    if (!Diags.isIgnored(diag::warn_tautological_overlap_comparison,
                         D->getBeginLoc())) {
      AC.getCFG();
    }
  
    // Collect statistics about the CFG if it was built.
    if (S.CollectStats && AC.isCFGBuilt()) {
      ++NumFunctionsAnalyzed;
      if (CFG *cfg = AC.getCFG()) {
        // If we successfully built a CFG for this context, record some more
        // detail information about it.
        NumCFGBlocks += cfg->getNumBlockIDs();
        MaxCFGBlocksPerFunction = std::max(MaxCFGBlocksPerFunction,
                                           cfg->getNumBlockIDs());
      } else {
        ++NumFunctionsWithBadCFGs;
      }
    }
  }
  
  void clang::sema::AnalysisBasedWarnings::PrintStats() const {
    llvm::errs() << "\n*** Analysis Based Warnings Stats:\n";
  
    unsigned NumCFGsBuilt = NumFunctionsAnalyzed - NumFunctionsWithBadCFGs;
    unsigned AvgCFGBlocksPerFunction =
        !NumCFGsBuilt ? 0 : NumCFGBlocks/NumCFGsBuilt;
    llvm::errs() << NumFunctionsAnalyzed << " functions analyzed ("
                 << NumFunctionsWithBadCFGs << " w/o CFGs).\n"
                 << "  " << NumCFGBlocks << " CFG blocks built.\n"
                 << "  " << AvgCFGBlocksPerFunction
                 << " average CFG blocks per function.\n"
                 << "  " << MaxCFGBlocksPerFunction
                 << " max CFG blocks per function.\n";
  
    unsigned AvgUninitVariablesPerFunction = !NumUninitAnalysisFunctions ? 0
        : NumUninitAnalysisVariables/NumUninitAnalysisFunctions;
    unsigned AvgUninitBlockVisitsPerFunction = !NumUninitAnalysisFunctions ? 0
        : NumUninitAnalysisBlockVisits/NumUninitAnalysisFunctions;
    llvm::errs() << NumUninitAnalysisFunctions
                 << " functions analyzed for uninitialiazed variables\n"
                 << "  " << NumUninitAnalysisVariables << " variables analyzed.\n"
                 << "  " << AvgUninitVariablesPerFunction
                 << " average variables per function.\n"
                 << "  " << MaxUninitAnalysisVariablesPerFunction
                 << " max variables per function.\n"
                 << "  " << NumUninitAnalysisBlockVisits << " block visits.\n"
                 << "  " << AvgUninitBlockVisitsPerFunction
                 << " average block visits per function.\n"
                 << "  " << MaxUninitAnalysisBlockVisitsPerFunction
                 << " max block visits per function.\n";
  }
  