What's the error for something like this?

mod Foo {} 
impl Foo {}

It's still

break.rs:3:1: 3:11 error: duplicate definition of type or module `Foo`
break.rs:3 mod Foo {}
           ^~~~~~~~~~
break.rs:2:1: 2:12 note: first definition of type or module `Foo` here
break.rs:2 impl Foo {}
           ^~~~~~~~~~~
error: aborting due to previous error

I'm a little wary about closing all those issues without seeing tests for them as well. Do any of these error messages improve?

#7607

pub mod a {
    pub struct Foo { a: uint }
}

pub mod b {
    use a::Foo;
    impl Foo { // ERROR: found value name used as type
        fn bar(&self) { }
    }
}

pub fn main() { }

foo.rs:6:9: 6:15 error: import `Foo` conflicts with type in this module
foo.rs:6     use a::Foo;
                 ^~~~~~
foo.rs:7:5: 9:6 note: note conflicting type here
foo.rs:7     impl Foo { // ERROR: found value name used as type
foo.rs:8         fn bar(&self) { }
foo.rs:9     }
error: aborting due to previous error

#8767

impl B {
}

fn main() {
}

foo.rs:1:6: 1:7 error: found module name used as a type: impl B::B (id=4)
foo.rs:1 impl B {
              ^

#12729

pub struct Foo;

mod bar {
    use Foo;

    impl Foo {
        fn baz(&self) {}
    }
}
fn main() {}

foo.rs:4:9: 4:12 error: import `Foo` conflicts with type in this module
foo.rs:4     use Foo;
                 ^~~
foo.rs:6:5: 8:6 note: note conflicting type here
foo.rs:6     impl Foo {
foo.rs:7         fn baz(&self) {}
foo.rs:8     }
error: aborting due to previous error

The error from the comments on #7607 you posted changes to "import Foo conflicts with type in this module", which (a) is not my doing, and (b) is not an improvement. The error in the original bug report is improved.

:/ this is embarrasing: #12729 does not change at all. (An error posted in the comments for that one is fixed, which I think is how it got swept up; but that error was actually a dupe of #7607 I think.)

#8767 and #15060 both trigger the improved error message. I'll add compile-fail tests for these.

I see how to fix the error messages for #12729 and #7607. Should I do those in this PR or submit a separate one?

It's ok to do them as part of this PR as well

Sorry for the delay, I was out of town. I've updated to fix the remaining error messages, and added compile-fail tests for all of them.

New push: puts error messages all on one line in compile-fail tests, also moves errors on use statements to the conflicting impl, where they logically belong.

Oops, missed one two-line compile-fail error message, sorry!