Add test t10373

Author: liufengyun

tests/patmat/t10373.scala

@@ -0,0 +1,15 @@
+abstract class Foo {
+  def bar(): Unit = this match {
+    case Foo_1() => //do something
+    case Foo_2() => //do something
+                    // Works fine
+  }
+
+  def baz(that: Foo): Unit = (this, that) match {
+    case (Foo_1(), _) => //do something
+    case (Foo_2(), _) => //do something
+                         // match may not be exhaustive
+  }
+}
+case class Foo_1() extends Foo
+case class Foo_2() extends Foo