add more tests

src/test/ui/mir/field-ty-ascription-enums.rs

@@ -0,0 +1,15 @@
+// build-pass
+
+enum Foo<T> {
+    Var(T),
+} // `T` is covariant.
+
+fn foo<'b>(x: Foo<for<'a> fn(&'a ())>) {
+    let Foo::Var(x): Foo<fn(&'b ())> = x;
+}
+
+fn foo_nested<'b>(x: Foo<Foo<for<'a> fn(&'a ())>>) {
+    let Foo::Var(Foo::Var(x)): Foo<Foo<fn(&'b ())>> = x;
+}
+
+fn main() {}

src/test/ui/mir/field-ty-ascription.rs

@@ -2,6 +2,22 @@
 
 struct Foo<T>(T); // `T` is covariant.
 
+struct Bar<T> {
+    x: T,
+} // `T` is covariant.
+
+fn bar<'b>(x: Bar<for<'a> fn(&'a ())>) {
+    let Bar { x }: Bar<fn(&'b ())> = x;
+}
+
+fn bar_nested<'b>(x: Bar<Bar<for<'a> fn(&'a ())>>) {
+    let Bar { x: Bar { x } }: Bar<Bar<fn(&'b ())>> = x;
+}
+
+fn bar_foo_nested<'b>(x: Bar<Foo<for<'a> fn(&'a ())>>) {
+    let Bar { x: Foo ( x ) }: Bar<Foo<fn(&'b ())>> = x;
+}
+
 fn foo<'b>(x: Foo<for<'a> fn(&'a ())>) {
     let Foo(y): Foo<fn(&'b ())> = x;
 }