SI-7715 String inpatternation s"$_" for s"${_}"

[som-snytt]

In a pattern,

scala> implicit class RX(val sc: StringContext) {
     | def rx = sc.parts.mkString("(.+)").r }
defined class RX

scala> "2 by 4" match { case rx"$a by $_" => a }
res0: String = 2

scala> val rx"$_ by $b" = "2 by 4"
b: String = 4

[adriaanm]

Oh boy.... How can this happen?

This one appears here and in #2821:

fail - pos/t7690.scala  [compilation failed]% scalac t7690.scala
error: the result type of an implicit conversion must be more specific than AnyRef
one error found

This one, only here:

fail - scalacheck/CheckCollections.scala  [compilation failed]% scalac CheckCollections.scala
CheckCollections.scala:22: error: not found: value map2Conserve
    val res = map2Conserve(xs, ys)(testid)
              ^
CheckCollections.scala:27: error: not found: value map2Conserve
    map2Conserve(xs, ys)(testid)  == map2ConserveOld(xs, ys)(testid) &&
    ^
CheckCollections.scala:11: error: not found: value map2Conserve
      val xs1 = map2Conserve(xs.tail, ys.tail)(f)
                ^
CheckCollections.scala:38: error: not found: value map2Conserve
    map2Conserve(xs, ys){ case(x, y) => x.toLowerCase + y.toString }
    ^
four errors found

[adriaanm]

LGTM -- awesome!