Extending Scala's arrow notation for pairs -

scala, in predef, defines support -> , → (here cleaned bit):

final class arrowassoc[a](val __leftofarrow: a) extends anyval {         def -> [b](y: b): tuple2[a, b] = tuple2(__leftofarrow, y)     def →[b](y: b): tuple2[a, b] = ->(y) } 

this conveniently allows create pairs using arrow notation instead of plain tuple syntax:

scala> "foo" → 42 res0: (string, int) = (foo,42) 

this arrow syntax can extended type definition , extractor (here → shown):

type →[a, b] = (a, b) object → { def unapply[a, b](t: (a, b)) = some(t) } 

this allows write things like:

"a" → 42 match { case → b ⇒ println(s"found `$a` , `$b`") } 

and:

def foo[a, b](t: → b) = ??? 

i wondering if there reason scala doesn't define in standard library. there downsides these definitions?

here 1 downside. being able both

def foo[a, b](t: -> b) = ??? 

and

def foo[a, b](t: => b) = ??? 

would confusing. if types don't line up, compiler catch of course. however, experienced scala programmer understand error message quickly.