given T = summon[T] sometimes loops forever

Compiler version

3.2.0

Minimized code

package Scope:
  class BaseClass:
    opaque type Opaque = Foo
    given TypeClass[Opaque] = summon[TypeClass[Opaque]]
    def getFoo: Foo = Foo()

  class SubClass extends BaseClass:
    override def getFoo: Opaque & Foo = new Foo().asInstanceOf[Opaque & Foo]

  class Foo

  trait TypeClass[T]:
    extension (b: T)
      def other: T

  given TypeClass[Foo] with
    extension (b: Foo)
      final def other: Foo = ???

@main def main(): Unit =
  val instance = Scope.SubClass()
  val concrete = instance.getFoo
  println("About to hang")
  val other = concrete.other
  println("Never reached")

Output

About to hang

Expectation

Termination (with a runtime error)

[odersky]

So I can think we can safely close this now.

[kyri-petrou]

I see warnings for all three summons that were shown in the examples above

Okay I see, I was using Scala 3.2.0 which doesn’t produce any warnings, but 3.2.1-RC1 and 3.2.1-RC2 do. Apologies for not checking that beforehand