Consider inferring return types of case class constructors

[illicitonion]

In this code:

case class Foo(s: String) {}

object Lib {
  def h1 = Foo("Hello")

  val h2 = Foo("World")
}

it's kind of verbose/repetitive to require def h1: Foo = Foo("Hello").

That said, if Foo stops being a case class, needing to update call sites is kind of annoying.

Maybe we should also allow inferring generally constructor or apply calls where the public return type of the apply is the same as the name of the type...