support val with pattern of > 22 subpats

[scabug]

I tried this in a standalone App object and in the REPL with identical outcome.

Reproduce code:

  type A = Int
  case class Foo(a: A, b: A, c: A, d: A, e: A, f: A, g: A, h: A, i: A, j: A, k: A, l: A, m: A, n: A, o: A, p: A, q: A, r: A, s: A, t: A, u: A, v: A, w: A, x: A, y: A, Z: A)
  val foo = Foo(1,2,3,4,5,6,7,8,9,0,1,2,3,4,5,6,7,8,9,0,1,2,3,4,5,6)
  val Foo(a,b,c,d,e,f,g,h,i,j,k,l,m,n,o,p,q,r,s,t,u,v,w,x,y,z) = foo

Expected result:
compiles fine

Actual result:

[error] object <none> is not a member of package scala
[error]   val Foo(a,b,c,d,e,f,g,h,i,j,k,l,m,n,o,p,q,r,s,t,u,v,w,x,y,z) = foo
[error]          ^
[error] one error found

Same happens for

val Foo(1,2,3,d,e,f,g,h,i,j,k,l,m,n,o,p,q,r,s,t,u,v,w,x,y,z) = foo

But not for

val Foo(1,2,3,4,e,f,g,h,i,j,k,l,m,n,o,p,q,r,s,t,u,v,w,x,y,z) = foo

which compiles fine, as it matches only 22 values.

[scabug]

Imported From: https://issues.scala-lang.org/browse/SI-8468?orig=1
Reporter: @cvogt
Affected Versions: 2.11.0-RC3
See #7296

[scabug]

@adriaanm said:
This is not a blocker since it's a new feature (thus not a regression) and it has a workaround:

 foo match { case Foo(a,b,c,d,e,f,g,h,i,j,k,l,m,n,o,p,q,r,s,t,u,v,w,x,y,z) => }

[scabug]

@adriaanm said:
The problem with the value definition that uses a pattern is that its translation uses Option[TupleN] under the hood, and we don't have enough tuples :-)

[scabug]

@xeno-by said:
What about name-based patmat?

[tOverney]

are there still plans to support this?

[SethTisue]

not in Scala 2. I don't know what the Scala 3 situation is on this. if someone wants to check on it we could perhaps add the "fixed in Dotty" label, if it is fixed.

I'm pretty tempted to just close the ticket as further changes in this area in Scala 2 seem quite unlikely. Someone from the community would have to step forward with a proposal and then follow it up with an implementation, too.