[PATCH] AST: Address of dllimport variables isn't constant

[David Majnemer]

Sure, I'll add a SemaCXX test for that.

================
Comment at: lib/AST/ExprConstant.cpp:4395
@@ -4393,1 +4394,3 @@
+    if (VD->hasAttr<DLLImportAttr>())
+      return ZeroInitialization(E);
     return Success(VD);
----------------
Reid Kleckner wrote:
> How is ZeroInitialization(E) different from Error(E)?
It isn't other than being, in my opinion, less confusing.  This isn't actually an error per-se because it isn't outright nonsense, it's just not evaluatable.  This matches what the codebase does for:
  int x = foo();

where `x` is at file scope and `foo` isn't constexpr.

http://reviews.llvm.org/D4250