Can't use names to impl them

[kmcallister]

struct Foo;

mod bar {
    use super::Foo;
    impl Foo {
        fn f() { }
    }
}

gives

baz.rs:5:10: 5:13 error: found module name used as a type: impl bar::Foo::Foo (id=8)
baz.rs:5     impl Foo {
                  ^~~

when impl super::Foo works fine.

rustc 0.11.0 (49bc17b 2014-07-07 17:16:34 +0000)

[kmcallister]

See also #16144

[jdm]

Dup of #12729.