Can't pattern match against function type sugar

[scabug]

The following works:

scala> val f : Int => Int = (x:Int) => x * x
f: (Int) => Int = <function>
scala> f match { case (g : Function1[_,_]) => g(2) }
res0: Any = 4

But the following doesn't:

scala> val f : Int => Int = (x:Int) => x * x
f: (Int) => Int = <function>
scala> f match { case (g : (_ => _)) => g(2) }
<console>:1: error: ')' expected but '=>' found.
       f match { case (g : (_ => _)) => g(2) }
                              ^
<console>:1: error: ')' expected but '}' found.
       f match { case (g : (_ => _)) => g(2) }

[scabug]

Imported From: https://issues.scala-lang.org/browse/SI-1285?orig=1
Reporter: Geoffrey Alan Washburn (washburn)

[scabug]

@paulp said:
Note to self: See also #2161.

[scabug]

@paulp said:
Note to self: took me a long time to notice, but this always worked, just not with underscores.

scala> f match { case g : (Int => Int) => g(2) } 
warning: there were unchecked warnings; re-run with -unchecked for details
res2: Int = 4

[scabug]

@paulp said:
More precisely, not with anything which the parser thinks is a variable, but yes with uppercase.