[clang] [Clang] Fix integer promotion of bit-fields in statement expressions (PR #225597)

[Aaron Ballman via cfe-commits]

================
@@ -7,3 +7,12 @@ void stmtexprs(int i) {
   // expected-warning at +1 {{assumption is ignored because it contains (potential) side-effects}}
   __builtin_assume( ({ if (i) ({ stmtexpr_fn(); }); 1; }) );
 }
+
+struct S {
+  unsigned b : 3;
+};
+
+void test_bitfield_promotion(struct S s) {
+  _Static_assert(_Generic(+({ s.b; }), int: 1, unsigned: 2) == 1,
----------------
AaronBallman wrote:

Can you also add these test cases just to round out coverage:
```
  _Static_assert(_Generic(+s.b, int: 1, unsigned: 2) == 1,
                 "this should be promoted");
  _Static_assert(_Generic(({ s.b; }), int: 1, unsigned: 2) == 2,
                 "this one does not get promoted");
  _Static_assert(_Generic(s.b, int: 1, unsigned: 2) == 2,
                 "nor does this one");
```

https://github.com/llvm/llvm-project/pull/225597