Point to type argument span when used as trait

Given the following code:

```rust
struct Foo<T: Clone>(T);

use std::ops::Add;

impl<T: Clone, Add> Add for Foo<T> {
    type Output = usize;

    fn add(self, rhs: Self) -> Self::Output {
      unimplemented!();
    }
}
```

present the following output:

```nocode
error[E0404]: `Add` is not a trait
 --> file3.rs:5:21
  |
5 | impl<T: Clone, Add> Add for Okok<T> {
  |                ---  ^^^ expected trait, found type parameter
  |                |
  |                type parameter defined here
```

1 files changed, 1 insertions, 1 deletions

diff --git a/src/test/ui/codemap_tests/two_files.stderr b/src/test/ui/codemap_tests/two_files.stderr
index d58e7148f61..d05e6eb2bbe 100644
--- a/src/test/ui/codemap_tests/two_files.stderr
+++ b/src/test/ui/codemap_tests/two_files.stderr
@@ -2,7 +2,7 @@ error[E0404]: `Bar` is not a trait
   --> $DIR/two_files.rs:15:6
    |
 15 | impl Bar for Baz { }
-   |      ^^^ not a trait
+   |      ^^^ expected trait, found type alias
    |
    = note: type aliases cannot be used for traits