E0004 needs to be updated to new format

[sophiajt]

From: src/test/compile-fail/E0004.rs

E0004 needs a span_label, taking it from:

error[E0004]: non-exhaustive patterns: `HastaLaVistaBaby` not covered
  --> src/test/compile-fail/E0004.rs:19:5
   |
19 |     match x { //~ ERROR E0004
   |     ^

to:

error[E0004]: non-exhaustive patterns: `HastaLaVistaBaby` not covered
  --> src/test/compile-fail/E0004.rs:19:5
   |
19 |     match x { //~ ERROR E0004
   |     ^ pattern `HastaLaVistaBaby` not covered

Bonus: We may want to update the span that this error uses as well to point at something other than the beginning of the match.

[TheZoq2]

I'll give this one a shot

[TheZoq2]

I wouldn't mind working on the bonus part of this issue too but i'm not sure what to change the span to. To me, it might make more sense to change it to

match x {
^^^^^^^

or

match x {
^^^^^

[sophiajt]

Yeah, I like:

match x {
^^^^^^^ pattern `HastaLaVistaBaby` not covered

[TheZoq2]

Alright, i'll try implementing that

[KiChjang]

@TheZoq2 Did you manage to include the bonus in your PR (#35380)? If not, I can take over.