Resolve: incorrect error messages after a duplicate module definition

[jseyfried]

For example,

mod foo {
    fn bar() -> bool { bar() }
}

mod foo {
    fn baz() { baz() }
    fn bar() { bar() }
}

reports the duplicate definition of foo, but also reports

<anon>:6:16: 6:19 error: unresolved name `baz` [E0425]
<anon>:6     fn baz() { baz() }
                        ^~~
<anon>:6:16: 6:19 help: see the detailed explanation for E0425
<anon>:7:16: 7:21 error: mismatched types:
 expected `()`,
    found `bool`
(expected (),
    found bool) [E0308]
<anon>:7     fn bar() { bar() }

The example compiles without errors if one of the modules' name is changed.