Bugfix :: Fix optimizer bug where field.Index included compiler generated static fields

[T-Gro]

Fixes #18165

The issue was caused by optimizer using a recordField.Index member which was also increment with compiler generated static fields, like init@5. Those should not be part of Index calculation.

There are two usages of the .Index member (I am putting them here, since GH text based diff will not show that)

• To sort fields. This remains the same if compiler generated static fields are excluded: let sortedRecdFields = unsortedRecdFields |> List.indexed |> Array.ofList |> Array.sortBy (fun (_, r) -> r.Index)
• In the optimizer path for optimizing away field get => this is the one which this fix targets and where the reported issue was coming from.

and TryOptimizeRecordFieldGet cenv _env (e1info, (RecdFieldRef (rtcref, _) as r), _tinst, m) =
    let g = cenv.g

    match destRecdValue e1info.Info with
    | Some finfos when cenv.settings.EliminateRecdFieldGet && not e1info.HasEffect ->
        match TryFindFSharpAttribute g g.attrib_CLIMutableAttribute rtcref.Attribs with
        | Some _ -> None
        | None ->
            let n = r.Index
            if n >= finfos.Length then errorR(InternalError( "TryOptimizeRecordFieldGet: term argument out of range", m))
            Some finfos[n]

[github-actions]

❗ Release notes required

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✅ Found changes and release notes in following paths:

Change path	Release notes path	Description
src/Compiler	docs/release-notes/.FSharp.Compiler.Service/9.0.300.md