Fix partially #30 (only Scala 3)

[y-yu]

• I try to make Scala3 version Eff implementation
  • It will uses Union and higher kind types for effect stacks
• So I need this TagMacro: make HKTag summonable for unapplied type lambdas with type bounds #30 , but I cannot fix this in Scala 2 😢

[CLAassistant]

All committers have signed the CLA.

[neko-kai]

@y-yu
Wow, thank you! 🙏

[neko-kai]

For Scala 2 fix, I think most of the issue is contained in mkHKTagArgStruct function in TagMacro.scala - as far as I remember all we have to do is generate bounds for the parameters there, e.g. add ability to generate types like HKTag[{ type Arg[T <: Int] = K[T] }] in addition to HKTag[{ type Arg[T] = K[T] }] types that we generate right now.

[neko-kai]

Is there a way to avoid implicit search here? In what situation do we need to regard a type parameter as strong if it doesn't have an implicit Tag?

[y-yu]

I was trying to fix this and finally it had worked without implicit search 🎉 after merging #279. (But I don't understand why it worked... 😇 )

[neko-kai]

@y-yu Thank you! 🙏