duplicate definition should report location of the definition

[erickt]

I'm running into this error:

./request.rs:1:7: 1:29 error: duplicate definition of type request
./request.rs:1 import mre::request::request;
                      ^~~~~~~~~~~~~~~~~~~~~~

even though I only import mre::request::request once in that file. Perhaps I'm running into a compiler bug, or maybe I just don't quite understand the import rules. So, it would be helpful if the duplicate definition error also reported where rust first found the definition.

[catamorphism]

#2386 is related.

[nikomatsakis]

I agree, it should print more details. @erickt likely the problem is an import in an outer scope. Why this is considered an error and not a shadow, I am not precisely sure, but I have seen it happen.

[gwillen]

I was going to file a bug suggesting that duplicate definition should report more information; specifically, if the duplicate definition is in an impl, rather than just "to_str", I'd like to see "impl to_str of to_str for @t".

But giving me the location would also be good.

[catamorphism]

The error message reports the first definition's span now.