FS3356 Extension members

[pezipink]

The following code used to work

module Test =
    type Holding.Position with 
        member this.X = ""
        member this.Y = ""

    type Reporting.Position with 
        member this.A = ""
        member this.B = ""

Where these types are declared somewhere else. In the new compiler I now get:

Extension members extending types with the same simple name 'Position' but different fully qualified names cannot be defined in the same module. Consider defining these extensions in separate modules.

I have reported this is a bug since this has always worked over many versions. The error is very specific though, is this a new behaviour and breaking change?

[T-Gro]

This is already fixed, but not yet part of the release VS product.
93c31cb

CheckForDuplicateExtensionMemberNames (added by #18821) was flagging all extension members on types with the same simple name from different namespaces. However, the underlying IL collision problem only affects static extension members — instance extension members compile with the extended type as the first IL parameter, which differentiates their signatures.

[pezipink]

Excellent, thanks! Apologies if this issue already existed - I couldn't find it.

[T-Gro]

I think it surfaced when adding "try build IcedTasks projects" regression test, I guess separate issue was never created - good to have this one as a reference point for anyone else.

[pezipink]

Hi, I just wanted to check on this one since you said it was fixed. I have seen the fix for #19527 filter down into production, and since this one was already fixed at that time, I expected to see this in the release as well.

However, it still seems to be an issue for me in my codebase, and my minimal repro above still causes the error. Is this expected? Has this fix gone out yet?

[T-Gro]

Can you please send your .NET/VS version info as well ?