method calls on opaques in defining scope: auto deref steps results in ambiguity 

```rust
#![feature(type_alias_impl_trait)]
fn main() {
    assert_eq!(foo().to_string(), "foo");
}

type Foo = impl std::fmt::Display;
fn foo() -> Foo {
    "foo"
}
```

this example has to compile but doesn't with the new solver