Add regression test

Author: ahejlsberg

tests/cases/conformance/types/literal/literalTypeWidening.ts

@@ -134,3 +134,10 @@ function test<T extends { a: string, b: string }>(obj: T): T {
     let { a, ...rest } = obj;
     return { a: 'hello', ...rest } as T;
 }
+
+// Repro from #32169
+
+declare function f<T>(x: T): NonNullable<T>;
+enum E { A, B }
+const a = f(E.A);
+const b: E.A = a;