Type hints should evaluate type matches with known arguments

[belamenso]

Is your feature request related to a problem? Please describe.

Scala 3.6.2. Consider this code

import scala.Tuple

class Container[Rs <: Tuple] {
  def guard(a: Tuple.Tail[Rs]): Unit = ()
}

@main def main(): Unit =
  Container[(1,2,3)].guard(null)

Hover with mouse in Metals-enabled VS Code at the word guard in the main function. You will see a type hint of this method

def guard(a: Tail[(1, 2, 3)]): Unit

This is not ideal because the type contains unevaluated type matches like Tuple.Tail that depend on entirely known types.

Describe the solution you'd like

I would like to see this type simplified to

def guard(a: (2, 3)): Unit

Describe alternatives you've considered

I do not know of alternative solutions to simplifying such expressions.

Additional context

No response

Search terms

type hint, type match, simplification

[tgodzik]

Thanks for reporting! I don't even know if that is possible, will need to ask around the compiler.

[belamenso]

I also link an almost identical issue I opened against the compiler but in the context of displaying error messages: scala/scala3#22333