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Allow let! and use! binding with type annotation without parentheses. #18508

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@edgarfgp edgarfgp commented Apr 26, 2025

Description

Allow let! and use! binding with type annotation without parentheses.

Fixes #10697

BEFORE

let f =
    async {
        let! (a: int) = async { return 1 } // Valid
        let! b: int = async { return 1 } // Error
        use! (a: int) = ...  //Error
        use! b: int = ... //Error
        return a
    }

AFTER

let f =
    async {
        let! (a: int) = ... // Valid
        let! b: int = ... // Valid
        return a
    }

Once #18487 is merged

let f =
    async {
        use! (a: int) = ...  // Valid
        use! b: int = ... // Valid
        return a
    }

At this point I want to see

  • What the CI says.
  • Check the SynTaxTree changes won't affect existing code.

Checklist

  • Test cases added
  • Release notes entry updated

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❗ Release notes required

@edgarfgp,

Caution

No release notes found for the changed paths (see table below).

Please make sure to add an entry with an informative description of the change as well as link to this pull request, issue and language suggestion if applicable. Release notes for this repository are based on Keep A Changelog format.

The following format is recommended for this repository:

* <Informative description>. ([PR #XXXXX](https://github.com/dotnet/fsharp/pull/XXXXX))

See examples in the files, listed in the table below or in th full documentation at https://fsharp.github.io/fsharp-compiler-docs/release-notes/About.html.

If you believe that release notes are not necessary for this PR, please add NO_RELEASE_NOTES label to the pull request.

You can open this PR in browser to add release notes: open in github.dev

Change path Release notes path Description
src/Compiler docs/release-notes/.FSharp.Compiler.Service/9.0.300.md No release notes found or release notes format is not correct

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let! binding with type annotation without parentheses yields error FS0010: Unexpected symbol ':' in expression
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