Leading parens trips up `sourcecode.Text`

[lihaoyi]

scala> def log[T](x: sourcecode.Text[T]) = println(s"[${x.source}]: ${x.value}")
log: [T](x: sourcecode.Text[T])Unit

scala> log(("omg" -> "omg").toString)
["omg" -> "omg"]: (omg,omg)

scala> // should have printed [("omg" -> "omg").toString]: (omg,omg)

As far as I can tell, Scalac sets the pos of the overall tree provided to the macro to the pos of the ->. There thus just isn't any pos anywhere at all which starts at the first (, which is what we'd want.

OTOH, we can tell when we're falling short, since the last pos within the tree should be within the range we parse. We may have to do a hacky parse-search to try and find a place where the parse encompasses all poss in the captured AST

[JohnReedLOL]

I think that what's actually happening is it is doing

toString("omg" -> "omg"); ("omg" -> "omg")