Fix #1797: Allow case class params with names _1, _2, ...

This was not possible before because it clashed with the automatically
generated name of the accessor. We now allow it, by simply taking the
parameter(accessor) itself as the case class accessor if it already has
that name. But you still cannot write

    case class C(_2: Int, _1: String)

nor should you be able to do this.

1 files changed, 1 insertions, 0 deletions

diff --git a/tests/pos/i1797.scala b/tests/pos/i1797.scala
new file mode 100644
index 000000000..1f10082b7
--- /dev/null
+++ b/tests/pos/i1797.scala
@@ -0,0 +1 @@
+case class Tuple1[T](_1: T)