[Proposal]: UTF-8 Literal Pattern Matching Support

[333fred]

UTF-8 Literal Pattern Matching Support

The LDM looked at the concept and approved it in theory, but it needs an approved specification. This is in the Any Time milestone, so we'd accept a specification from a community member.

Discussion: #6036

Design Meetings

• https://github.com/dotnet/csharplang/blob/main/meetings/2022/LDM-2022-05-11.md#pattern-matching-with-utf-8-string-literals

[neon-sunset]

@333fred I would like to try writing a specification for this proposal (will be able to start next week).

[333fred]

Go for it, though I will be out until late August.

[bill-poole]

It would be very useful if C# also provided the ability to specify a UTF-8 string (e.g., "MyUtf8String"u8) as a constant, which would then allow such constants to be used in the respective case statements of a switch statement. That would then have the potential to allow developers to more easily build much more efficient JsonConverter<T> implementations because at present, each JSON property is found/identified through a chain of if/else-if statements using Utf8JsonReader.ValueTextEquals calls.

If the switch statement performance improvements for switching string options implemented in .NET 8 were to be made available for UTF-8 strings and then employed in JsonConverter<T> implementations, we could see a significant performance boost in JSON deserialization.