Allow static let bindings in union, record, struct, non-incremental-class types

[dsyme]

I propose we allow static let bindings in a wider range of type definitions:

type T =
    static let f _ = ()

type AB = 
    | A
    | B of int
    static let b0 = B 0
    static let b1 = B 1
    static member B0 = b0
    static member B1 = b1

Currently static let bindings are only allowed in types with incremental constructors. This restriction makes sense for let bindings but not static let bindings. They should be allowed in all nominal type definitions including stucts etc.

There are many situations where this results in an artificial need for a module or class-type-holding-statics

Pros and Cons

The advantages of making this adjustment to F# are regularity, simplicity, fewer restrictions.

The disadvantages of making this adjustment to F# are needs to be implemented

Extra information

Estimated cost (XS, S, M, L, XL, XXL): M

Related suggestions: (put links to related suggestions here)

Affidavit (please submit!)

Please tick this by placing a cross in the box:

• [x] This is not a question (e.g. like one you might ask on stackoverflow) and I have searched stackoverflow for discussions of this issue
• [x] I have searched both open and closed suggestions on this site and believe this is not a duplicate
• [ ] 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 F# untyped") then please don't submit it.

Please tick all that apply:

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

For Readers

If you would like to see this issue implemented, please click the :+1: emoji on this issue. These counts are used to generally order the suggestions by engagement.