XML comments - support "include" and "inherit"

[T-Gro]

I propose we add support for the <inheritdoc> and <include> XML documentation tags in F#'s XML documentation comments, aligning with C#'s capabilities. This would allow F# code to inherit and include XML doc content in a more maintainable manner, improving documentation parity with C#.

This suggestion is based on dotnet/fsharp#19175 opened by @jwosty, who noted that the F# docs explicitly mention this is not supported and that there was no issue tracking it. We are moving this idea forward here for formal language suggestion tracking.

The existing way of approaching this problem in F# is manually duplicating all XML documentation across overrides or repeated API patterns. Neither <inheritdoc> nor <include> are supported. The F# docs explicitly state this limitation: F# XML Documentation Limitations.

Pros and Cons

The advantages of making this adjustment to F# are

• Parity with C# for documentation reuse and inheritance.
• Easier to write and maintain comprehensive documentation, especially in larger codebases with many overrides or repeated API patterns.
• Improved documentation consistency across projects.
• Reduces duplication and risk of documentation drifting out of sync.

The disadvantages of making this adjustment to F# are

• Implementation introduces some compiler complexity.
• Could potentially hide places where docs should be uniquely written, if over-used.

Extra information

Estimated cost (XS, S, M, L, XL, XXL):
S (for <include>) / M (for <inheritdoc>)

Related suggestions:

• Original issue at dotnet/fsharp: Support xmldoc <inheritdoc> and <include> (#19175)
• WIP - Prototype implementation for <include> support: Add support for <include> XML documentation tag (#19186)
• Support for <inheritdoc> does not yet have a working prototype implementation.

Affidavit (please submit!)

Please tick these items by placing a cross in the box:

• This is not a question (e. g. like one you might ask on StackOverflow) and I have searched StackOverflow for discussions of this issue
• This is a language change and not purely a tooling change (e.g. compiler bug, editor support, warning/error messages, new warning, non-breaking optimisation) belonging to the compiler and tooling repo.
• This is not something which has obviously "already been decided" in previous versions of F#. If you're questioning a fundamental design decision that has obviously already been taken (e.g. "Make everything mutable by default"), please say so.
• I have searched both open and closed suggestions on this site and believe this is not a duplicate

Please tick all that apply:

• This is not a breaking change to the F# language design
• I or my company would be willing to help implement and/or test this

For Readers

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[T-Gro]

RFC at fsharp/fslang-design#827