enum type instead of variant suggestion unification

Weirdly, we were deciding between a help note and a structured
suggestion based on whether the import candidate span was a dummy—but
we weren't using that span in any case! The dummy-ness of the span
(which appears to be a matter of this-crate vs. other-crate
definition) isn't the right criterion by which we should decide
whether it's germane to mention that "there is an enum variant";
instead, let's use the someness of `def` (which is used as the
`has_unexpected_resolution` argument to `error_code`).

Since `import_candidate_to_paths` has no other callers, we are free to
stop returning the span and rename the function. By using
`span_suggestions_`, we leverage the max-suggestions output limit
already built in to the emitter, thus resolving #56028.

In the matter of message wording, "you can" is redundant (and perhaps
too informal); prefer the imperative.

1 files changed, 6 insertions, 10 deletions

diff --git a/src/test/ui/variants/variant-used-as-type.stderr b/src/test/ui/variants/variant-used-as-type.stderr
index 972fe8a8a61..c72729923ef 100644
--- a/src/test/ui/variants/variant-used-as-type.stderr
+++ b/src/test/ui/variants/variant-used-as-type.stderr
@@ -3,28 +3,24 @@ error[E0573]: expected type, found variant `Ty::A`
    |
 LL |     B(Ty::A),
    |       ^^^^^ not a type
-help: you can try using the variant's enum
-   |
-LL |     B(Ty),
-   |       ^^
-help: you can try using the variant's enum
+help: try using the variant's enum
    |
 LL |     B(E),
    |       ^
+LL |     B(Ty),
+   |       ^^
 
 error[E0573]: expected type, found variant `E::A`
   --> $DIR/variant-used-as-type.rs:27:6
    |
 LL | impl E::A {}
    |      ^^^^ not a type
-help: you can try using the variant's enum
-   |
-LL | impl Ty {}
-   |      ^^
-help: you can try using the variant's enum
+help: try using the variant's enum
    |
 LL | impl E {}
    |      ^
+LL | impl Ty {}
+   |      ^^
 
 error: aborting due to 2 previous errors