Given search doesn't work with identical polymorphic function types

[p-pavel]

Compiler version

3.3.x, 3.4.x, 3.5.x, 3.6.x, probably earlier too

Minimized code

//> using scala 3.6.4
type TF1[Lang[_]] = [A] => Lang[A] ?=> A
type TF2[Lang[_]] = [A] => Lang[A] ?=> A
type TF3[Lang[_]] = TF1[Lang]

trait IsTF[T]
given [T[_]] => IsTF[TF1[T]] = new IsTF {}

trait Abc[A]:
  def plus(a: A, b: A): A

val s1 = summon[TF1[Abc] =:= TF2[Abc]] // Ok
val s2 = summon[TF1[Abc] =:= ([A] => Abc[A] ?=> A)] //Ok
val t1 = summon[IsTF[ TF1[Abc]]] //Ok
val t2 = summon[IsTF[ [A] => Abc[A] ?=> A ]] //Not found
val t3 = summon[IsTF[ TF2[Abc]]] // Not found
val t4 = summon[IsTF[ TF3[Abc]]] // Ok

Output

No given instance of type IsTF[[A] => (x$1: Abc[A]) ?=> A] was found for parameter x of method summon in object Predef
No given instance of type IsTF[TF2[Abc]] was found for parameter x of method summon in object Predef

Expectation

given instances should be found

[p-pavel]

the workaround I used (it's not a general workaround, because I specify the Algebra):

trait IsTF[T[_], A]

given [T[_], A] => (A =:= TF1[T]) => IsTF[T,A] = ....

Compiler is able to find the instance for TF2[T] and derive the proof that TF2[T] =:= TF1[T]