relates to:

• SR-11159 Typechecker crash on overloaded enum case

Issue Description:

Consider this code:

enum X {
  case x(a: Int)
  case x(b: Int)
}

This definition is happily accepted by swiftc, but the following:

switch X.x(a: 1) {
case .x(a: _):
  break
case .x(b: _):
  break
}

fails with the following error message:

error.swift:7:9: error: tuple pattern element label 'a' must be 'b'
case .x(a: _):

I'm not sure if the bug is due to the fact that the compiler allows the definition of cases with overlapping names (which IMO should be legal, because it's no different than overloading functions on argument names), or if it's due to an error in the switch handling within the compiler.