Bad diagnostics for bogus effects specifier before arrow or brace in function

[ahoppen]

Issue Kind

Bad Diagnostic Produced

Source Code

func foo() bogus -> Int {}
() bogus reasync -> Int

Description

Instead of using at to check for the -> or {, we should check whether we can recover to it on the same line, possibly reducing the recovery precedence when parsing function types because they could be followed by an identifier.

[ahoppen]

rdar://104621275

[StevenWong12]

Hi @ahoppen, I've just started investigating this issue. I ran the parse cli to print the diagnosics for the code snippet above and I got the following diagnostics

1 │ func test() bogus -> Int {}
  ∣            ╰─ error: consecutive statements on a line must be separated by ';'

From my understanding, it should produce a more useful diagnostics message for that e.g.

1 │ func test() bogus -> Int {}
  ∣            ╰─ error: unknown effect specifier

Have I got that right?

Thanks in advance!

[ahoppen]

Yes, exactly.

The first step would be to get it to produce something like the following by improving recovery inside there parser itself

1 │ func test() bogus -> Int {}
  ∣            ╰─ error: unexpected code 'bogus' in function declaration

As a second step you can then improve the diagnostic to unknown effect specifier 'bogus' in the diagnostic generator.

[StevenWong12]

Great! Thanks for your advice. I am about to try it out and hope this will be my first contribution to this repo!

[ahoppen]

Fixed by #1381