Revert "Remove faulty test"

This reverts commit e17248f.

Author: Sporarum

tests/neg/interweaving-unmatched.scala

@@ -0,0 +1,4 @@
+object unmatched:
+    def f1[T (x: T)] = ??? // error
+    def f2(x: Any[)T] = ??? // error // error
+    def f3[T(x: T) = ??? // error