regex interpolation fails ..

gistfile1.scala

Apples-MacBook-Pro:~ debasishg$ scala
Welcome to Scala version 2.10.0 (Java HotSpot(TM) 64-Bit Server VM, Java 1.6.0_45).
Type in expressions to have them evaluated.
Type :help for more information.

scala> :paste
// Entering paste mode (ctrl-D to finish)

implicit class RContext(sc: StringContext) {
  def r = 
    new util.matching.Regex(
         sc.parts.mkString(""), 
         sc.parts.tail.map(_ => "x"): _*)
}

// Exiting paste mode, now interpreting.

defined class RContext

scala> "database:[table1,table2]" matches """(\w+)(:\[(\w+)(,(\w+))*\])?"""
res0: Boolean = true

scala> :paste
// Entering paste mode (ctrl-D to finish)

"database:[table1,table2]" match {
  case r"""(\w+)(:\[(\w+)(,(\w+))*\])?""" => true
  case _ => false
}

// Exiting paste mode, now interpreting.

res1: Boolean = false

scala> 

Your r method should be an extractor object in order to work with match expressions. This is incomplete, but proves the point:

scala> implicit class RContext(sc: StringContext) {
     |   object r {
     |     def apply(args: Any*) =
     |       sc.parts.mkString.r
     | 
     |     def unapplySeq(s: String): Option[Seq[String]] =
     |       sc.parts.mkString.r.unapplySeq(s)
     |   }
     | }
defined class RContext

scala> "database:[table1,table2]" matches """(\w+)(:\[(\w+)(,(\w+))*\])?"""
res25: Boolean = true

scala> "database:[table1,table2]" match {
     |   case r"""(?:\w+)(?::\[(?:\w+)(?:,(?:\w+))*\])?""" => true
     |   case _ => false
     | }
res26: Boolean = true

scala> val pattern = r"""(\w+)(:\[(\w+)(,(\w+))*\])?"""
pattern: scala.util.matching.Regex = (\w+)(:\[(\w+)(,(\w+))*\])?

scala> val pattern(a,b,c,d,e) = "database:[table1,table2]"
a: String = database
b: String = :[table1,table2]
c: String = table1
d: String = ,table2
e: String = table2

scala> 

Notice however that the pattern in the match expressions uses only non-capturing groups, otherwise it wouldn't match. It's possible to extend the extractor to bind named groups to variables, but I'm not sure it's trivial. This friend of mine has achieved something along these lines here:

https://github.com/alexandru/shifter/blob/master/web-api/src/main/scala/shifter/web/api/mvc/PathMatcher.scala
https://github.com/alexandru/shifter/blob/master/web-api/src/test/scala/shifter/web/api/mvc/PathMatcherSuite.scala

Here's also a blog post that gets into some of the details: http://hootenannylas.blogspot.ro/2013/02/pattern-matching-with-string.html

Okay, so your original version works just fine with non-capturing groups. That was the problem.

this works ..

scala> :paste
// Entering paste mode (ctrl-D to finish)

"database:[table1,table2]" match {
  case r"""(\w+)$d(:\[(\w+)$f(,(\w+)$x)*$y\])?$t""" => (d, f, x, y, t)
  case _ => "no match"
}

// Exiting paste mode, now interpreting.

res29: java.io.Serializable = (database,:[table1,table2],table1,,table2,table2)