Remove the CFGElement "Invalid" state.

Use Optional<CFG*> where invalid states were needed previously. In the one case
where that's not possible (beginAutomaticObjDtorsInsert) just use a dummy
CFGAutomaticObjDtor.

Thanks for the help from Jordan Rose & discussion/feedback from Ted Kremenek
and Doug Gregor.

Post commit code review feedback on r175796 by Ted Kremenek.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@175938 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Analysis/CFG.cpp b/lib/Analysis/CFG.cpp
index 8754fe8..4d20467 100644
--- a/lib/Analysis/CFG.cpp
+++ b/lib/Analysis/CFG.cpp
@@ -3332,7 +3332,6 @@
 const CXXDestructorDecl *
 CFGImplicitDtor::getDestructorDecl(ASTContext &astContext) const {
   switch (getKind()) {
-    case CFGElement::Invalid:
     case CFGElement::Statement:
     case CFGElement::Initializer:
       llvm_unreachable("getDestructorDecl should only be used with "
@@ -3406,8 +3405,8 @@
 
   for (CFG::iterator I=cfg.begin(), E=cfg.end(); I != E; ++I)
     for (CFGBlock::iterator BI=(*I)->begin(), EI=(*I)->end(); BI != EI; ++BI)
-      if (CFGStmt S = BI->getAs<CFGStmt>())
-        FindSubExprAssignments(S.getStmt(), SubExprAssignments);
+      if (Optional<CFGStmt> S = BI->getAs<CFGStmt>())
+        FindSubExprAssignments(S->getStmt(), SubExprAssignments);
 
   for (CFG::iterator I=cfg.begin(), E=cfg.end(); I != E; ++I) {
 
@@ -3415,10 +3414,10 @@
     // block-level that are block-level expressions.
 
     for (CFGBlock::iterator BI=(*I)->begin(), EI=(*I)->end(); BI != EI; ++BI) {
-      CFGStmt CS = BI->getAs<CFGStmt>();
+      Optional<CFGStmt> CS = BI->getAs<CFGStmt>();
       if (!CS)
         continue;
-      if (const Expr *Exp = dyn_cast<Expr>(CS.getStmt())) {
+      if (const Expr *Exp = dyn_cast<Expr>(CS->getStmt())) {
         assert((Exp->IgnoreParens() == Exp) && "No parens on block-level exps");
 
         if (const BinaryOperator* B = dyn_cast<BinaryOperator>(Exp)) {
@@ -3531,8 +3530,8 @@
       unsigned j = 1;
       for (CFGBlock::const_iterator BI = (*I)->begin(), BEnd = (*I)->end() ;
            BI != BEnd; ++BI, ++j ) {        
-        if (CFGStmt SE = BI->getAs<CFGStmt>()) {
-          const Stmt *stmt= SE.getStmt();
+        if (Optional<CFGStmt> SE = BI->getAs<CFGStmt>()) {
+          const Stmt *stmt= SE->getStmt();
           std::pair<unsigned, unsigned> P((*I)->getBlockID(), j);
           StmtMap[stmt] = P;
 
@@ -3721,8 +3720,8 @@
 
 static void print_elem(raw_ostream &OS, StmtPrinterHelper* Helper,
                        const CFGElement &E) {
-  if (CFGStmt CS = E.getAs<CFGStmt>()) {
-    const Stmt *S = CS.getStmt();
+  if (Optional<CFGStmt> CS = E.getAs<CFGStmt>()) {
+    const Stmt *S = CS->getStmt();
     
     if (Helper) {
 
@@ -3769,8 +3768,8 @@
     if (isa<Expr>(S))
       OS << '\n';
 
-  } else if (CFGInitializer IE = E.getAs<CFGInitializer>()) {
-    const CXXCtorInitializer *I = IE.getInitializer();
+  } else if (Optional<CFGInitializer> IE = E.getAs<CFGInitializer>()) {
+    const CXXCtorInitializer *I = IE->getInitializer();
     if (I->isBaseInitializer())
       OS << I->getBaseClass()->getAsCXXRecordDecl()->getName();
     else OS << I->getAnyMember()->getName();
@@ -3784,8 +3783,9 @@
       OS << " (Base initializer)\n";
     else OS << " (Member initializer)\n";
 
-  } else if (CFGAutomaticObjDtor DE = E.getAs<CFGAutomaticObjDtor>()){
-    const VarDecl *VD = DE.getVarDecl();
+  } else if (Optional<CFGAutomaticObjDtor> DE =
+                 E.getAs<CFGAutomaticObjDtor>()) {
+    const VarDecl *VD = DE->getVarDecl();
     Helper->handleDecl(VD, OS);
 
     const Type* T = VD->getType().getTypePtr();
@@ -3796,20 +3796,20 @@
     OS << ".~" << T->getAsCXXRecordDecl()->getName().str() << "()";
     OS << " (Implicit destructor)\n";
 
-  } else if (CFGBaseDtor BE = E.getAs<CFGBaseDtor>()) {
-    const CXXBaseSpecifier *BS = BE.getBaseSpecifier();
+  } else if (Optional<CFGBaseDtor> BE = E.getAs<CFGBaseDtor>()) {
+    const CXXBaseSpecifier *BS = BE->getBaseSpecifier();
     OS << "~" << BS->getType()->getAsCXXRecordDecl()->getName() << "()";
     OS << " (Base object destructor)\n";
 
-  } else if (CFGMemberDtor ME = E.getAs<CFGMemberDtor>()) {
-    const FieldDecl *FD = ME.getFieldDecl();
+  } else if (Optional<CFGMemberDtor> ME = E.getAs<CFGMemberDtor>()) {
+    const FieldDecl *FD = ME->getFieldDecl();
     const Type *T = FD->getType()->getBaseElementTypeUnsafe();
     OS << "this->" << FD->getName();
     OS << ".~" << T->getAsCXXRecordDecl()->getName() << "()";
     OS << " (Member object destructor)\n";
 
-  } else if (CFGTemporaryDtor TE = E.getAs<CFGTemporaryDtor>()) {
-    const CXXBindTemporaryExpr *BT = TE.getBindTemporaryExpr();
+  } else if (Optional<CFGTemporaryDtor> TE = E.getAs<CFGTemporaryDtor>()) {
+    const CXXBindTemporaryExpr *BT = TE->getBindTemporaryExpr();
     OS << "~" << BT->getType()->getAsCXXRecordDecl()->getName() << "()";
     OS << " (Temporary object destructor)\n";
   }
diff --git a/lib/Analysis/CFGStmtMap.cpp b/lib/Analysis/CFGStmtMap.cpp
index 7daeef9..87c2f5b 100644
--- a/lib/Analysis/CFGStmtMap.cpp
+++ b/lib/Analysis/CFGStmtMap.cpp
@@ -50,11 +50,11 @@
   // First walk the block-level expressions.
   for (CFGBlock::iterator I = B->begin(), E = B->end(); I != E; ++I) {
     const CFGElement &CE = *I;
-    CFGStmt CS = CE.getAs<CFGStmt>();
+    Optional<CFGStmt> CS = CE.getAs<CFGStmt>();
     if (!CS)
       continue;
     
-    CFGBlock *&Entry = SM[CS.getStmt()];
+    CFGBlock *&Entry = SM[CS->getStmt()];
     // If 'Entry' is already initialized (e.g., a terminator was already),
     // skip.
     if (Entry)
diff --git a/lib/Analysis/LiveVariables.cpp b/lib/Analysis/LiveVariables.cpp
index 519d528..b43892a 100644
--- a/lib/Analysis/LiveVariables.cpp
+++ b/lib/Analysis/LiveVariables.cpp
@@ -474,8 +474,9 @@
        ei = block->rend(); it != ei; ++it) {
     const CFGElement &elem = *it;
 
-    if (CFGAutomaticObjDtor Dtor = elem.getAs<CFGAutomaticObjDtor>()){
-      val.liveDecls = DSetFact.add(val.liveDecls, Dtor.getVarDecl());
+    if (Optional<CFGAutomaticObjDtor> Dtor =
+            elem.getAs<CFGAutomaticObjDtor>()) {
+      val.liveDecls = DSetFact.add(val.liveDecls, Dtor->getVarDecl());
       continue;
     }
 
@@ -534,8 +535,9 @@
     if (killAtAssign)
       for (CFGBlock::const_iterator bi = block->begin(), be = block->end();
            bi != be; ++bi) {
-        if (CFGStmt cs = bi->getAs<CFGStmt>()) {
-          if (const BinaryOperator *BO = dyn_cast<BinaryOperator>(cs.getStmt())) {
+        if (Optional<CFGStmt> cs = bi->getAs<CFGStmt>()) {
+          if (const BinaryOperator *BO =
+                  dyn_cast<BinaryOperator>(cs->getStmt())) {
             if (BO->getOpcode() == BO_Assign) {
               if (const DeclRefExpr *DR =
                     dyn_cast<DeclRefExpr>(BO->getLHS()->IgnoreParens())) {
diff --git a/lib/Analysis/ReachableCode.cpp b/lib/Analysis/ReachableCode.cpp
index f85e2de..a90aebb 100644
--- a/lib/Analysis/ReachableCode.cpp
+++ b/lib/Analysis/ReachableCode.cpp
@@ -95,8 +95,8 @@
 
 const Stmt *DeadCodeScan::findDeadCode(const clang::CFGBlock *Block) {
   for (CFGBlock::const_iterator I = Block->begin(), E = Block->end(); I!=E; ++I)
-    if (CFGStmt CS = I->getAs<CFGStmt>()) {
-      const Stmt *S = CS.getStmt();
+    if (Optional<CFGStmt> CS = I->getAs<CFGStmt>()) {
+      const Stmt *S = CS->getStmt();
       if (isValidDeadStmt(S))
         return S;
     }
diff --git a/lib/Analysis/ThreadSafety.cpp b/lib/Analysis/ThreadSafety.cpp
index 2e3abc0..7bb54d6 100644
--- a/lib/Analysis/ThreadSafety.cpp
+++ b/lib/Analysis/ThreadSafety.cpp
@@ -1397,8 +1397,8 @@
       for (CFGBlock::const_reverse_iterator BI = CurrBlock->rbegin(),
            BE = CurrBlock->rend(); BI != BE; ++BI) {
         // FIXME: Handle other CFGElement kinds.
-        if (CFGStmt CS = BI->getAs<CFGStmt>()) {
-          CurrBlockInfo->ExitLoc = CS.getStmt()->getLocStart();
+        if (Optional<CFGStmt> CS = BI->getAs<CFGStmt>()) {
+          CurrBlockInfo->ExitLoc = CS->getStmt()->getLocStart();
           break;
         }
       }
@@ -1410,8 +1410,8 @@
       for (CFGBlock::const_iterator BI = CurrBlock->begin(),
            BE = CurrBlock->end(); BI != BE; ++BI) {
         // FIXME: Handle other CFGElement kinds.
-        if (CFGStmt CS = BI->getAs<CFGStmt>()) {
-          CurrBlockInfo->EntryLoc = CS.getStmt()->getLocStart();
+        if (Optional<CFGStmt> CS = BI->getAs<CFGStmt>()) {
+          CurrBlockInfo->EntryLoc = CS->getStmt()->getLocStart();
           break;
         }
       }
@@ -2234,8 +2234,8 @@
     return false;
 
   CFGElement Last = B->back();
-  if (CFGStmt S = Last.getAs<CFGStmt>()) {
-    if (isa<CXXThrowExpr>(S.getStmt()))
+  if (Optional<CFGStmt> S = Last.getAs<CFGStmt>()) {
+    if (isa<CXXThrowExpr>(S->getStmt()))
       return true;
   }
   return false;
diff --git a/lib/Analysis/UninitializedValues.cpp b/lib/Analysis/UninitializedValues.cpp
index 022bb7d..730aa6b 100644
--- a/lib/Analysis/UninitializedValues.cpp
+++ b/lib/Analysis/UninitializedValues.cpp
@@ -746,9 +746,8 @@
   TransferFunctions tf(vals, cfg, block, ac, classification, handler);
   for (CFGBlock::const_iterator I = block->begin(), E = block->end(); 
        I != E; ++I) {
-    if (CFGStmt cs = I->getAs<CFGStmt>()) {
-      tf.Visit(const_cast<Stmt*>(cs.getStmt()));
-    }
+    if (Optional<CFGStmt> cs = I->getAs<CFGStmt>())
+      tf.Visit(const_cast<Stmt*>(cs->getStmt()));
   }
   return vals.updateValueVectorWithScratch(block);
 }