The opposite of compiletime.constValue[T] in Scala 3

Question

If we have a transparent inline def f(...): Boolean = ..., is it possible to convert the result of f to true or false types, assuming the result of f is known at compile-time? I would like to use those types in an implicit search.

For example,

given [A](using f(5) <:< true): MyTypeClass with ...

However, the problem is that f(5) is a value, not a type. So the above code won't compile.

Answer 1

I guess the closest is

val x = TypeOf(f(5))

given [A](using x.T <:< A): MyTypeClass[A] = ???

class TypeOf[A](a: A):
  type T = A

trait MyTypeClass[A]

transparent inline def f(inline i: Int): Any = inline i match
  case 5 => true
  case _ => "a"

summon[MyTypeClass[Boolean]] // compiles
summon[MyTypeClass[String]] // doesn't compile

Unfortunately we can't replace (using x.T <:< A) with (using TypeOf(f(5)).T <:< A) because path-dependent types must have stable prefix even in Scala 3.

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