Allow typed bindings(and!) in CE without parentheses

[edgarfgp]

Description

Allow computation expression (CE) bindings (let!, use!, and!) to accept type annotations without requiring parentheses.

Continuation of #18508
Implements RFC FS-1329: fsharp/fslang-design#802

Introduces significant grammar unification:

• New parsing rules: bindingPatternWithOptType and ceBindingCore
• New helper functions: mkLetExpression and mkAndBang
• Renamed language feature to AllowTypedLetUseAndBang

The above rule unification will allow us to remove in a separate PR LetOrUseBang, adding boolenisComputed property(true for let!/use!, false for let/use) to LetOrUse.

type SynExpr =
    | LetOrUse of 
        isRecursive: bool * 
        isUse: bool * 
        isComputed: bool *     // NEW: true for let!/use!, false for let/use
        bindings: SynBinding list * 
        body: SynExpr * 
        range: range * 
        trivia: SynExprLetOrUseTrivia

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/10.0.100.md
LanguageFeatures.fsi	docs/release-notes/.Language/preview.md

[auduchinok]

@edgarfgp Thanks for this! Could you also cover error cases in the grammar, please? If unified with the let parsing, we could probably get a lot of recovery for free as well.

[edgarfgp]

/azp run

[azure-pipelines]

Commenter does not have sufficient privileges for PR 18682 in repo dotnet/fsharp

[Copilot]

Pull Request Overview

This PR implements support for allowing type annotations on let!, use!, and and! bindings in computation expressions without requiring parentheses, in line with RFC FS-1329.

• Grammar and AST updates introduce unified parsing rules (bindingPatternWithOptType, ceBindingCore) and new helper functions (mkLetExpression, mkAndBang) to build the correct AST nodes.
• Language feature renamed to AllowTypedLetUseAndBang and its usage updated in both the feature registry and computation expression checker.
• Extensive updates to parser-service tests, component tests, and release notes ensure coverage of the new scenarios and adjust expected diagnostics.

Reviewed Changes

Copilot reviewed 86 out of 86 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
tests/service/data/SyntaxTree/SynType/Typed UseBang.fs / .fs.bsl	Updated parser-service test cases for typed use! scenarios, adjusting expected parse errors and AST shapes.
tests/service/data/SyntaxTree/SynType/Typed LetBang AndBang.fs / .fs.bsl	Extended test suite across 18+ variations to cover typed let!, and!, patterns, lists, tuples, unions, etc.
tests/service/data/SyntaxTree/Pattern/Typed - Missing type*.fs.bsl	Added missing Expecting type parse errors to existing pattern tests.
tests/service/data/SyntaxTree/Member/Member 13.fs.bsl	Injected Expecting type parse error for incomplete member definitions.
tests/service/data/SyntaxTree/Expression/Yield* / Return*!*.fs.bsl	Added Expecting type parse errors to yield/return tests for completeness.
tests/service/data/SyntaxTree/ComputationExpression/SynExprAndBangRange.fs.bsl	Fixed ranges for SynExprAndBang to reflect trimmed spans after grammar changes.
tests/FSharp.Compiler.ComponentTests/Language/ComputationExpressionTests.fs	Extended CE component tests to cover and! type-annotation behavior and adjusted diagnostic positions.
tests/FSharp.Compiler.ComponentTests/Conformance/BasicGrammarElements/UseBindings/*.fs	Adjusted diagnostic column spans in UseBangBindingsVersion9 tests to match new grammar.
src/Compiler/pars.fsy	Introduced bindingPatternWithOptType and ceBindingCore, updated and! grammar rules and error recovery.
src/Compiler/SyntaxTree/ParseHelpers.fsi	Added mkLetExpression and mkAndBang signatures; replaced old mkLocalBindings.
src/Compiler/SyntaxTree/ParseHelpers.fs	Implemented mkLetExpression and mkAndBang, removed mkLocalBindings, unified binding AST creation.
src/Compiler/Facilities/LanguageFeatures.fsi / .fs	Renamed feature flag to AllowTypedLetUseAndBang and updated version support.
src/Compiler/Checking/Expressions/CheckComputationExpressions.fs	Updated computation expression checker to use the new AllowTypedLetUseAndBang language feature.
docs/release-notes/.Language/preview.md	Added entry for preview support of and! type annotations without parentheses.
docs/release-notes/.FSharp.Compiler.Service/10.0.100.md	Updated release notes to include and! in the feature description.

Comments suppressed due to low confidence (2)

src/Compiler/SyntaxTree/ParseHelpers.fs:871

• [nitpick] Consider adding XML documentation comments for mkAndBang in the .fsi file to explain its parameters and use in computation expressions.

let mkAndBang (mKeyword: range, pat: SynPat, rhs: SynExpr, mWhole: range, mEquals: range, mIn: range option) =

src/Compiler/pars.fsy:3523

• [nitpick] It may help to expand this comment with an example of how bindingPatternWithOptType interacts with ceBindingCore and the new and! rules, improving future maintainability.

// This rule unifies the pattern parsing for both regular 'let' bindings and (let!, use!, and!)