Replace TypeLoc llvm::cast support to be well-defined.

The TypeLoc hierarchy used the llvm::cast machinery to perform undefined
behavior by casting pointers/references to TypeLoc objects to derived types
and then using the derived copy constructors (or even returning pointers to
derived types that actually point to the original TypeLoc object).

Some context is in this thread:
http://lists.cs.uiuc.edu/pipermail/llvmdev/2012-December/056804.html
Though it's spread over a few months which can be hard to read in the mail
archive.

llvm-svn: 175462

1 files changed, 12 insertions, 13 deletions

diff --git a/clang/lib/Sema/SemaTemplateInstantiateDecl.cpp b/clang/lib/Sema/SemaTemplateInstantiateDecl.cpp
index 2d3d0bd5b69..d854f7a25e5 100644
--- a/clang/lib/Sema/SemaTemplateInstantiateDecl.cpp
+++ b/clang/lib/Sema/SemaTemplateInstantiateDecl.cpp
@@ -1706,7 +1706,7 @@ Decl *TemplateDeclInstantiator::VisitNonTypeTemplateParmDecl(
     // The non-type template parameter pack's type is a pack expansion of types.
     // Determine whether we need to expand this parameter pack into separate
     // types.
-    PackExpansionTypeLoc Expansion = cast<PackExpansionTypeLoc>(TL);
+    PackExpansionTypeLoc Expansion = TL.castAs<PackExpansionTypeLoc>();
     TypeLoc Pattern = Expansion.getPatternLoc();
     SmallVector<UnexpandedParameterPack, 2> Unexpanded;
     SemaRef.collectUnexpandedParameterPacks(Pattern, Unexpanded);
@@ -2335,15 +2335,14 @@ TemplateDeclInstantiator::SubstFunctionType(FunctionDecl *D,
   if (NewTInfo != OldTInfo) {
     // Get parameters from the new type info.
     TypeLoc OldTL = OldTInfo->getTypeLoc().IgnoreParens();
-    if (FunctionProtoTypeLoc *OldProtoLoc
-                                  = dyn_cast<FunctionProtoTypeLoc>(&OldTL)) {
+    if (FunctionProtoTypeLoc OldProtoLoc =
+            OldTL.getAs<FunctionProtoTypeLoc>()) {
       TypeLoc NewTL = NewTInfo->getTypeLoc().IgnoreParens();
-      FunctionProtoTypeLoc *NewProtoLoc = cast<FunctionProtoTypeLoc>(&NewTL);
-      assert(NewProtoLoc && "Missing prototype?");
+      FunctionProtoTypeLoc NewProtoLoc = NewTL.castAs<FunctionProtoTypeLoc>();
       unsigned NewIdx = 0;
-      for (unsigned OldIdx = 0, NumOldParams = OldProtoLoc->getNumArgs();
+      for (unsigned OldIdx = 0, NumOldParams = OldProtoLoc.getNumArgs();
            OldIdx != NumOldParams; ++OldIdx) {
-        ParmVarDecl *OldParam = OldProtoLoc->getArg(OldIdx);
+        ParmVarDecl *OldParam = OldProtoLoc.getArg(OldIdx);
         LocalInstantiationScope *Scope = SemaRef.CurrentInstantiationScope;
 
         llvm::Optional<unsigned> NumArgumentsInExpansion;
@@ -2354,14 +2353,14 @@ TemplateDeclInstantiator::SubstFunctionType(FunctionDecl *D,
         if (!NumArgumentsInExpansion) {
           // Simple case: normal parameter, or a parameter pack that's
           // instantiated to a (still-dependent) parameter pack.
-          ParmVarDecl *NewParam = NewProtoLoc->getArg(NewIdx++);
+          ParmVarDecl *NewParam = NewProtoLoc.getArg(NewIdx++);
           Params.push_back(NewParam);
           Scope->InstantiatedLocal(OldParam, NewParam);
         } else {
           // Parameter pack expansion: make the instantiation an argument pack.
           Scope->MakeInstantiatedLocalArgPack(OldParam);
           for (unsigned I = 0; I != *NumArgumentsInExpansion; ++I) {
-            ParmVarDecl *NewParam = NewProtoLoc->getArg(NewIdx++);
+            ParmVarDecl *NewParam = NewProtoLoc.getArg(NewIdx++);
             Params.push_back(NewParam);
             Scope->InstantiatedLocalPackArg(OldParam, NewParam);
           }
@@ -2373,10 +2372,10 @@ TemplateDeclInstantiator::SubstFunctionType(FunctionDecl *D,
     // substitution occurred. However, we still need to instantiate
     // the function parameters themselves.
     TypeLoc OldTL = OldTInfo->getTypeLoc().IgnoreParens();
-    if (FunctionProtoTypeLoc *OldProtoLoc
-                                    = dyn_cast<FunctionProtoTypeLoc>(&OldTL)) {
-      for (unsigned i = 0, i_end = OldProtoLoc->getNumArgs(); i != i_end; ++i) {
-        ParmVarDecl *Parm = VisitParmVarDecl(OldProtoLoc->getArg(i));
+    if (FunctionProtoTypeLoc OldProtoLoc =
+            OldTL.getAs<FunctionProtoTypeLoc>()) {
+      for (unsigned i = 0, i_end = OldProtoLoc.getNumArgs(); i != i_end; ++i) {
+        ParmVarDecl *Parm = VisitParmVarDecl(OldProtoLoc.getArg(i));
         if (!Parm)
           return 0;
         Params.push_back(Parm);