Parse: MS property members cannot have an in-class initializer

We would crash trying to treat a property member as a field.  These
shoudl be forbidden anyway, reject programs which contain them.

This fixes PR21840.

llvm-svn: 224193
diff --git a/clang/lib/Sema/SemaDeclCXX.cpp b/clang/lib/Sema/SemaDeclCXX.cpp
index a6ff02c..82407250 100644
--- a/clang/lib/Sema/SemaDeclCXX.cpp
+++ b/clang/lib/Sema/SemaDeclCXX.cpp
@@ -2656,13 +2656,14 @@
   // Pop the notional constructor scope we created earlier.
   PopFunctionScopeInfo(nullptr, D);
 
-  FieldDecl *FD = cast<FieldDecl>(D);
-  assert(FD->getInClassInitStyle() != ICIS_NoInit &&
+  FieldDecl *FD = dyn_cast<FieldDecl>(D);
+  assert((isa<MSPropertyDecl>(D) || FD->getInClassInitStyle() != ICIS_NoInit) &&
          "must set init style when field is created");
 
   if (!InitExpr) {
-    FD->setInvalidDecl();
-    FD->removeInClassInitializer();
+    D->setInvalidDecl();
+    if (FD)
+      FD->removeInClassInitializer();
     return;
   }