remove outdated opaque type test

tests/ui/type-alias-impl-trait/fallback.rs

@@ -1,29 +0,0 @@
-// Tests that we correctly handle opaque types being used opaquely,
-// even within their defining scope.
-//
-#![feature(type_alias_impl_trait)]
-
-type Foo = impl Copy;
-
-enum Wrapper<T> {
-    First(T),
-    Second,
-}
-
-// This method constrains `Foo` to be `bool`
-#[define_opaque(Foo)]
-fn constrained_foo() -> Foo {
-    true
-}
-
-// This method does not constrain `Foo`.
-// Per RFC 2071, function bodies may either
-// fully constrain an opaque type, or place no
-// constraints on it.
-#[define_opaque(Foo)]
-fn unconstrained_foo() -> Wrapper<Foo> {
-    Wrapper::Second
-    //~^ ERROR: type annotations needed
-}
-
-fn main() {}

tests/ui/type-alias-impl-trait/fallback.stderr

@@ -1,20 +0,0 @@
-error[E0283]: type annotations needed
-  --> $DIR/fallback.rs:25:5
-   |
-LL | fn unconstrained_foo() -> Wrapper<Foo> {
-   |                           ------------ type must be known at this point
-LL |     Wrapper::Second
-   |     ^^^^^^^^^^^^^^^
-   |     |
-   |     cannot infer type of the type parameter `T` declared on the enum `Wrapper`
-   |     return type was inferred to be `Wrapper<_>` here
-   |
-   = note: cannot satisfy `_: Copy`
-help: consider specifying the generic argument
-   |
-LL |     Wrapper::<T>::Second
-   |            +++++
-
-error: aborting due to 1 previous error
-
-For more information about this error, try `rustc --explain E0283`.