Support Expr.FunctionBetaReduction for all arities

Author: nicolasstucki

compiler/src/dotty/tools/dotc/core/Definitions.scala

@@ -1232,7 +1232,7 @@ class Definitions {
   }
 
   def tupleTypes(tp: Type, bound: Int = Int.MaxValue)(implicit ctx: Context): Option[List[Type]] = {
-    @tailrec def rec(tp: Type, acc: List[Type], bound: Int): Option[List[Type]] = tp match {
+    @tailrec def rec(tp: Type, acc: List[Type], bound: Int): Option[List[Type]] = tp.normalized match {
       case _ if bound < 0 => Some(acc.reverse)
       case tp: AppliedType if defn.PairClass == tp.classSymbol => rec(tp.args(1), tp.args.head :: acc, bound - 1)
       case tp: AppliedType if defn.isTupleClass(tp.tycon.classSymbol) => Some(acc.reverse ::: tp.args)