Can't have impls for a type outside of the defining module.

[alexcrichton]

I may have regressed this at some point during resolve, but this program fails to compile

pub mod a {                               
    struct A;                             
    impl A {                              
        fn foo(&self) {}                  
    }                                     
}                                         

pub mod b {                               
    use a::A;                             

    impl A {                              
        fn bar(&self) {}                  
    }                                     
}                                         
fn main() {}                                         

with the error message

foo.rs:11:9: 11:10 error: found value name used as a type: DefMod(syntax::ast::DefId{crate: 0, node: 19})        
foo.rs:11     impl A {                                                                                           
                   ^                                                                                             
task '<unnamed>' failed at 'explicit failure', /Users/alex/code/rust-opt/src/libsyntax/diagnostic.rs:75          
task '<unnamed>' failed at 'explicit failure', /Users/alex/code/rust-opt/src/librustc/rustc.rs:396               

I'm not sure if we event want to allow this. If we do, this should get fixed. If we don't, then the error message should be improved.

This seems to me like something that should work, but there may be reasons that it shouldn't...

[alexcrichton]

Closing as a dupe of #7607 (one of the comments on that bug is the exact same as this)