[Inheritance] [protected] Cannot derive from `NpgsqlTypeMappingSource` beause of inability to override

[xperiandri]

If I override all the methods F# complains about I get
System.TypeLoadException: 'Return type in method 'Npgsql.EntityFrameworkCore.PostgreSQL.Storage.Internal.NpgsqlDiscriminatedUnionEnumTypeMappingSource.FindMapping(System.Type)' on type 'Npgsql.EntityFrameworkCore.PostgreSQL.Storage.Internal.NpgsqlDiscriminatedUnionEnumTypeMappingSource' from assembly 'NpgsqlDiscriminatedUnionEnumTypeMappingSourceRepro, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null' is not compatible with base type method 'Microsoft.EntityFrameworkCore.Storage.RelationalTypeMappingSource.FindMapping(System.Type)'.'

Repro steps

NpgsqlDiscriminatedUnionEnumTypeMappingSourceRepro.zip

1. Extract the attached sample
2. Run
3. See exception
4. Try removing lines 71-79 from NpgsqlDiscriminatedUnionEnumTypeMapping.fs
5. See that the compiler complaints about protected members

Expected behavior

Lines 71-79 in NpgsqlDiscriminatedUnionEnumTypeMapping.fs are not required and the file successfully builds

Actual behavior

F# complaints about not implemented methods that are actually implemented

Known workarounds

No

Related information

• .NET SDK 7.0.400-preview.23274.1
• Visual Studio 2022 17.7 Preview 2.0
• Visual F# Tools from @vzarytovskii OneDrive

[0101]

fsharp/fslang-suggestions#157 needs to be implemented to fix this