Add patman test

Author: noti0na1

tests/explicit-nulls/neg-patmat/patmat1.scala renamed to tests/explicit-nulls/neg-patmat/match-pat.scala

@@ -1,12 +1,9 @@
 class Foo {
+
   val s: String = ???
-  s match {
-    case s: String => 100 // warning: type test will always succeed
-    case _ => 200 // error: unreachable
-  }
 
   s match {
-    case s: String => 100 // warning: type test will always succeed
+    case s: String => 100
     case _ => 200 // error: unreachable
   }
 
@@ -15,20 +12,23 @@ class Foo {
   case object Cat extends Animal
 
   val a: Animal = ???
+
   a match {
     case Dog(name) => 100
     case Cat => 200
     case _ => 300 // error: unreachable
   }
 
-  val a2: Animal|Null = ???
+  val a2: Animal | Null = ???
+
   a2 match {
     case Dog(_) => 100
     case Cat => 200
     case _ => 300
   }
 
-  val a3: Animal|Null = ???
+  val a3: Animal | Null = ???
+
   a3 match {
     case Dog(_) => 100
     case Cat => 200

tests/explicit-nulls/neg-patmat/unsafe-match-null-pat.scala

@@ -0,0 +1,14 @@
+import scala.language.unsafeNulls
+
+def test1 =
+  val s: String = ???
+  s match
+    case _: String =>
+    // under unsafeNulls, we should not get Match case Unreachable Warning
+    case null => // ok
+
+def test2 =
+  val s: String | Null = ???
+  s match
+    case _: String =>
+    case null =>

tests/explicit-nulls/unsafe-common/unsafe-match-null.scala

@@ -2,8 +2,7 @@ def test1 =
   val s: String = ???
   s match
     case _: String =>
-    // under unsafeNulls, we should not get Match case Unreachable Warning
-    case null => // error
+    case null => // error: Values of types Null and String cannot be compared
 
 def test2 =
   val s: String | Null = ???