EtaExpand can produce code that does not compile when there is a SAM conversion

[eejbyfeldt]

The following code

trait TC[X] {
  def gen(r: Int): X
}

val gen: Int => Int = ???
val tc: TC[Int] = x => gen(x)

get rewritten to

trait TC[X] {
  def gen(r: Int): X
}

val gen: Int => Int = ???
val tc: TC[Int] = gen

That does not compile due to

     Found:    (gen : Int => Int)
     Required: TC[Int]

Seems like one might need semantic information to detect and fix this case, but I am not sure.