fix parsing certain multiline match / indentation cases

[aryairani]

Overview

There is a weird situation currently in a match / with where if a function argument starts in the same column as the start of the scrutinee, there's a parse failure. e.g.,

-- ok
match a 
       b c with _ -> ()
-- bad
match a 
      b c with _ -> ()
-- ok
match a 
     b c with _ -> ()
-- bad
match a 
    b c with _ -> ()
-- ok
match a 
   b c with _ -> ()

So that's weird.

How do we want this to work?

If we want all of the above to work, then merging this PR will do that and fix #6048.

• What does this change accomplish and why?

  • i.e. How does it change the user experience?
  • i.e. What was the old behavior/API and what is the new behavior/API?

• Include "before and after" examples if appropriate. (You can copy/paste screenshots directly into this editor.)

• List any Github issues that this PR closes, in closing-issues-using-keywords format.

Implementation approach and notes

The PR just adds match to the set of syntax constructions in which to not emit virtual semis; equivalent to surrounding the contents in parens.

I wonder whether handle/with needs the same treatment? But it didn't exhibit exactly the same bug so idk.

Interesting/controversial decisions

Test coverage

• Have you included tests (which could be a transcript) for this change, or is it somehow covered by existing tests?

New before-and-after transcript in the two commits.

• Would you recommend improving the test coverage (either as part of this PR or as a separate issue) or do you think it’s adequate?

Seems good.

• If you only tested by hand, because that's all that's practical to do for this change, mention that. Include screenshots.

Loose ends

n/a

Final checklist

• Choose your PR title well: Your pull request title is what's used to create release notes, so please make it descriptive of the change itself, which may be different from the initial motivation to make the change.
• Update your PR description if the specifics of the PR have changed over time.
• Include transcripts or screenshots that demonstrate the changed behavior.
• If you changed .cabal files, make sure the package.yaml files are up-to-date instead.