Fix 11873: Name is bound multiple times is not reported in 'as' pattern

[edgarfgp]

Description

Fixes #11873

Before

let f1 a a = ()
         ^
         Error: "'a' is bound twice in this pattern"
let f2 (a, b as c) c = ()
				   ^
				   Error: "'c' is bound twice in this pattern"

let f3 (a, b as c) a = ()
				   ^
				   No Error

After

let f1 a a = ()
         ^
         Error: "'a' is bound twice in this pattern"
let f2 (a, b as c) c = ()
				   ^
				   Error: "'c' is bound twice in this pattern"

let f3 (a, b as c) a = ()
				   ^
				   Error: "'a' is bound twice in this pattern"

Checklist

• Test cases added
• Release notes entry updated

[github-actions]

❗ Release notes required

---

✅ Found changes and release notes in following paths:

Change path	Release notes path	Description
src/Compiler	docs/release-notes/.FSharp.Compiler.Service/11.0.0.md

[auduchinok]

Please add a few tests showing that this won't clash with a real pattern named unitVar, i.e. something like the following works as expected, there's no error and the patterns are not considered to be same-named:

let (unitVar, ()) = 1, ()

let f unitVar () = ()

let f (unitVar, ()) = ()

[edgarfgp]

Like 6375cd8 ?

[auduchinok]

Could you also try to replicate the problem from the initial issue?

[edgarfgp]

Sure. I guess you mean adding a test for code shown in the #11873 .

let f1 a a = ()
let f2 (a, b as c) c = ()
let f3 (a, b as c) a = ()

[edgarfgp]

Added 3a1028b

[auduchinok]

Please cover unitVar there in the cases that are fixed here.

[edgarfgp]

Added in e6ea704

[auduchinok]

@edgarfgp You've added many tests, but none of them cover both 1) the initial issue about different pattern groups and 2) () and unitVar possibly being considered to have the same name (which would be a regression if there's a new error). This change introduces a possible regression and we need just one case to ensure it doesn't happen, but none of these additional tests seem to cover the actual change.

[edgarfgp]

Added in 5488c00