Fix expected type of TupleXXL unapply (#16248)

Author: dwijnand

compiler/src/dotty/tools/dotc/typer/Typer.scala

@@ -2818,7 +2818,7 @@ class Typer(@constructorOnly nestingLevel: Int = 0) extends Namer
         val tupleXXLobj = untpd.ref(defn.TupleXXLModule.termRef)
         val app = untpd.cpy.Apply(tree)(tupleXXLobj, elems.map(untpd.TypedSplice(_)))
           .withSpan(tree.span)
-        val app1 = typed(app, defn.TupleXXLClass.typeRef)
+        val app1 = typed(app, if ctx.mode.is(Mode.Pattern) then pt else defn.TupleXXLClass.typeRef)
         if (ctx.mode.is(Mode.Pattern)) app1
         else {
           val elemTpes = elems.lazyZip(pts).map((elem, pt) =>

tests/run/i16213.scala

@@ -0,0 +1,11 @@
+object Test:
+  def main(args: Array[String]): Unit =
+    test(1) // was: ClassCastException: java.lang.Integer cannot be cast to scala.runtime.TupleXXL
+
+  def test(any: Any) = any match
+    case (
+      _, _, _, _, _, _, _, _, _, _,
+      _, _, _, _, _, _, _, _, _, _,
+      _, _, _
+    ) => 23
+    case _ => -1