add test that repros issue #47338

This currently fails for the CFE with:

static error failures:
- Unexpected error at line 137, column 14: A value of type 'int?' can't be assigned to a variable of type 'int' because 'int?' is nullable and 'int' isn't.
- Unexpected error at line 137, column 25: Operand of null-aware operation '!' has type 'int' which excludes null.

Bug: #47338
Change-Id: Ia55e19a0bf296a8427f6510d6ddda5016acdecea
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/215101
Reviewed-by: Johnni Winther <johnniwinther@google.com>
Commit-Queue: Jake Macdonald <jakemac@google.com>

Author: jakemac53

tests/language/null_aware/access_test.dart

@@ -132,4 +132,7 @@ main() {
   //                                        ^^^^^^^^
   // [analyzer] COMPILE_TIME_ERROR.UNDEFINED_GETTER
   // [cfe] Member not found: 'hashCode'.
+
+  // (C.staticInt?.floor())! can be assigned to int.
+  int y = (C.staticInt?.floor())!;
 }