add one more test for type ascription of never

Author: WaffleLapkin

tests/ui/unreachable-code/type_ascribe_never_field.rs

@@ -0,0 +1,17 @@
+// Regression test for <https://github.com/rust-lang/rust/issues/149431>
+//
+// Checks that type ascription of a field place with type never is correctly
+// checked for if it constitutes a read of type never. (it doesn't)
+//
+//@ check-pass
+
+#![feature(never_type)]
+#![feature(type_ascription)]
+#![deny(unreachable_code)]
+
+fn main() {
+   let x: (!,);
+   let _ = type_ascribe!(x.0, _);
+
+   (); // reachable
+}