Poor compile time performance of shapeless.ops.record.{ Selector, Updater }

[milessabin]

Compile time scales super-linearly with number of case class members. This seems to account for most of the poor compile time performance of shapeless lens builders.

import shapeless._, record._

case class Foo(
  /*
  z0: Int,
  y0: Int,
  x0: Int,
  w0: Int,
  v0: Int,
  u0: Int,
  t0: Int,
  s0: Int,
  r0: Int,
  q0: Int,
  p0: Int,
  o0: Int,
  n0: Int,
  m0: Int,
  l0: Int,
  k0: Int,
  j0: Int,
  i0: Int,
  h0: Int,
  g0: Int,
  f0: Int,
  e0: Int,
  d0: Int,
  c0: Int,
  b0: Int,
  a0: Int,
  z: Int,
  */
  y: Int,
  x: Int,                                                                                                
  w: Int,                                                                                                
  v: Int,                                                                                                
  u: Int,                                                                                                
  t: Int,                                                                                                
  s: Int,                                                                                                
  r: Int,                                                                                                
  q: Int,                                                                                                
  p: Int,                                                                                                
  o: Int,                                                                                                
  n: Int,                                                                                                
  m: Int,                                                                                                
  l: Int,                                                                                                
  k: Int,                                                                                                
  j: Int,                                                                                                
  i: Int,                                                                                                
  h: Int,                                                                                                
  g: Int,                                                                                                
  f: Int,                                                                                                
  e: Int,                                                                                                
  d: Int,                                                                                                
  c: Int,                                                                                                
  b: Int,                                                                                                
  a: Int                                                                                                 
)                                                                                                        

object Test {                                                                                            
  val lgen = LabelledGeneric[Foo]                                                                        
  val foo: Foo = null                                                                                    
  val r = lgen.to(foo)                                                                                   

  r('a)                                                                                                  
  r.updated('a, 23)                                                                                      
}

[milessabin]

Fixed in d4c3c71.