Disallow calling abstract methods directly on interfaces

[edgarfgp]

Fixes #14012

• Check introduced to ensure we can call on virtual members, can't call abstracts.

open System.Numerics
IAdditionOperators.op_Addition (3, 6) // New compiler error as this is an static abstract

IAdditionOperators.op_CheckedAddition (3, 6) // Compiles and run as this a static virtual

See:
https://source.dot.net/#System.Private.CoreLib/src/libraries/System.Private.CoreLib/src/System/Numerics/IAdditionOperators.cs,5b77e6b404819054

[vzarytovskii]

That's not right, constrained calls 'T.Parse should work through multiple levels of inheritance, since it will know specific implementation at runtime. ISpanParsable<'T>.Parse, if it's non-virtual, shouldn't on other hand.

[vzarytovskii]

Thanks for changing it @edgarfgp, do you think it makes sense to just filter those out as non-valid methods or is it just me? It's a quite unique and new situation, since we don't really have it for non-statics.

[vzarytovskii]

Also, a reminder for myself for Monday: test that we still have autocomplete on type constrained call, e.g. 'T.<autocompletes all abstract methods>.

[edgarfgp]

Thanks for changing it @edgarfgp, do you think it makes sense to just filter those out as non-valid methods or is it just me? It's a quite unique and new situation, since we don't really have it for non-statics.

I think the static nature of this methods will raise the expectation of been available through competition in a type tbh and it that case a dedicated error message explaining the reasoning of this behaviour will be desirable. That being said in this PR my main focus is to prevent the runtime errors currently happening.

[edgarfgp]

Also, a reminder for myself for Monday: test that we still have autocomplete on type constrained call, e.g. 'T.<autocompletes all abstract methods>.

Could you also check the filtering condition please. I haven’t found yet a way to make this test pass.

[vzarytovskii]

Thanks for changing it @edgarfgp, do you think it makes sense to just filter those out as non-valid methods or is it just me? It's a quite unique and new situation, since we don't really have it for non-statics.

I think the static nature of this methods will raise the expectation of been available through competition in a type tbh and it that case a dedicated error message explaining the reasoning of this behaviour will be desirable. That being said in this PR my main focus is to prevent the runtime errors currently happening.

Do we really want for it to be available via completion, it it will lead to the compile time error? I.e. not usable if it's non-virtual?

[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/8.0.300.md

[edgarfgp]

Replaced by #17021