Implement effects of 'mutable', and a few comments from Chris on its parsing.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@59470 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/test/SemaCXX/class.cpp b/test/SemaCXX/class.cpp
index ada508a..b7d1ca3 100644
--- a/test/SemaCXX/class.cpp
+++ b/test/SemaCXX/class.cpp
@@ -82,6 +82,18 @@
   }
 };
 
+struct C3 {
+  int i;
+  mutable int j;
+};
+void f()
+{
+  const C3 c3 = { 1, 2 };
+  (void)static_cast<int*>(&c3.i); // expected-error {{static_cast from 'int const *' to 'int *' is not allowed}}
+  // but no error here
+  (void)static_cast<int*>(&c3.j);
+}
+
 // Play with mutable a bit more, to make sure it doesn't crash anything.
 mutable int gi; // expected-error {{error: 'mutable' can only be applied to member variables}}
 mutable void gfn(); // expected-error {{illegal storage class on function}}