Merge pull request #7215 from dotty-staging/fix-7043

Fix #7043: Add regression test

Author: OlivierBlanvillain

tests/neg/7043.scala

@@ -0,0 +1,15 @@
+object Test {
+  type StrHead[X <: Tuple] = X match {
+    case (x <: String) *: _ => x // error
+  }
+
+  // Futher minimized
+  type M[X] = X match {
+    case (x) *: _ => Int
+  }
+
+  // The exception can also be reached with normal pattern matching
+  1 match {
+    case _: Option[(x)] => ()
+  }
+}