[clang][Interp] Don't try to decay non-pointers to pointers

Author: tbaederr

clang/lib/AST/Interp/ByteCodeExprGen.cpp

@@ -4250,7 +4250,7 @@ bool ByteCodeExprGen<Emitter>::visitDeclRef(const ValueDecl *D, const Expr *E) {
     if (E->getType()->isVoidType())
       return true;
     // Convert the dummy pointer to another pointer type if we have to.
-    if (PrimType PT = classifyPrim(E); PT != PT_Ptr) {
+    if (PrimType PT = classifyPrim(E); PT != PT_Ptr && isPtrType(PT)) {
       if (!this->emitDecayPtr(PT_Ptr, PT, E))
         return false;
     }

clang/test/CXX/temp/temp.res/temp.dep/temp.dep.constexpr/p2-0x.cpp

@@ -1,4 +1,4 @@
-// RUN: %clang_cc1 -std=c++11 -verify %s
+// RUN: %clang_cc1 -std=c++11 -verify %s -fexperimental-new-constant-interpreter
 
 template<int n> struct S; // expected-note 3{{here}}