8 files changed, 115 insertions, 10 deletions
diff --git a/test/files/neg/bug3098.check b/test/files/neg/bug3098.check
new file mode 100644
index 0000000000..403da281c8
--- /dev/null
+++ b/test/files/neg/bug3098.check
@@ -0,0 +1,6 @@
+b.scala:3: error: match is not exhaustive!
+missing combination              C
+
+  def f = (null: T) match {
+               ^
+one error found
diff --git a/test/files/neg/bug3098.flags b/test/files/neg/bug3098.flags
new file mode 100644
index 0000000000..e8fb65d50c
--- /dev/null
+++ b/test/files/neg/bug3098.flags
@@ -0,0 +1 @@
+-Xfatal-warnings
+\ No newline at end of file
diff --git a/test/files/neg/bug3098/a.scala b/test/files/neg/bug3098/a.scala
new file mode 100644
index 0000000000..57a103c7a8
--- /dev/null
+++ b/test/files/neg/bug3098/a.scala
@@ -0,0 +1,6 @@
+// Traits.scala
+sealed trait T
+
+trait A extends T
+trait B extends T
+trait C extends T
diff --git a/test/files/neg/bug3098/b.scala b/test/files/neg/bug3098/b.scala
new file mode 100644
index 0000000000..84a1f9f6f4
--- /dev/null
+++ b/test/files/neg/bug3098/b.scala
@@ -0,0 +1,8 @@
+// Test.scala
+object Test {
+  def f = (null: T) match {
+    case _: A => println("A")
+    case _: B => println("B")
+    // no C
+  }
+}
diff --git a/test/files/neg/patmatexhaust.check b/test/files/neg/patmatexhaust.check
index 8aa9238d2e..5426d61d31 100644
--- a/test/files/neg/patmatexhaust.check
+++ b/test/files/neg/patmatexhaust.check
@@ -35,4 +35,20 @@ missing combination              B
 
   def ma9(x: B) = x match {
                   ^
-7 errors found
+patmatexhaust.scala:100: error: match is not exhaustive!
+missing combination             C1
+
+    def ma10(x: C) = x match { // not exhaustive: C1 is not sealed.
+                     ^
+patmatexhaust.scala:114: error: match is not exhaustive!
+missing combination             D1
+missing combination             D2
+
+    def ma10(x: C) = x match {  // not exhaustive: C1 has subclasses.
+                     ^
+patmatexhaust.scala:126: error: match is not exhaustive!
+missing combination             C1
+
+    def ma10(x: C) = x match { // not exhaustive: C1 is not abstract.
+                     ^
+10 errors found
diff --git a/test/files/neg/patmatexhaust.scala b/test/files/neg/patmatexhaust.scala
index d49c4b207b..45aed558da 100644
--- a/test/files/neg/patmatexhaust.scala
+++ b/test/files/neg/patmatexhaust.scala
@@ -76,14 +76,56 @@ class TestSealedExhaustive { // compile only
     case B1() => true       // missing B, which is not abstract so must be included
     case B2   => true
   }
-  sealed abstract class C
-  abstract class C1 extends C
-  object C2 extends C
-  case object C6 extends C
-  class C3 extends C1
-  case class C4() extends C3
-  def ma10(x: C) = x match { // exhaustive
-    case C4()     => true
-    case C2 | C6  => true
+
+  object ob1 {
+    sealed abstract class C
+    sealed abstract class C1 extends C
+    object C2 extends C
+    case class C3() extends C
+    case object C4 extends C
+
+    def ma10(x: C) = x match {  // exhaustive: abstract sealed C1 is dead end.
+      case C3()     => true
+      case C2 | C4  => true
+    }
+  }
+
+  object ob2 {
+    sealed abstract class C
+    abstract class C1 extends C
+    object C2 extends C
+    case class C3() extends C
+    case object C4 extends C
+
+    def ma10(x: C) = x match { // not exhaustive: C1 is not sealed.
+      case C3()     => true
+      case C2 | C4  => true
+    }
+  }
+  object ob3 {
+    sealed abstract class C
+    sealed abstract class C1 extends C
+    object D1 extends C1
+    case class D2() extends C1
+    object C2 extends C
+    case class C3() extends C
+    case object C4 extends C
+
+    def ma10(x: C) = x match {  // not exhaustive: C1 has subclasses.
+      case C3()     => true
+      case C2 | C4  => true
+    }
+  }
+  object ob4 {
+    sealed abstract class C
+    sealed class C1 extends C
+    object C2 extends C
+    case class C3() extends C
+    case object C4 extends C
+
+    def ma10(x: C) = x match { // not exhaustive: C1 is not abstract.
+      case C3()     => true
+      case C2 | C4  => true
+    }
   }
 }
diff --git a/test/files/pos/bug4020.flags b/test/files/pos/bug4020.flags
new file mode 100644
index 0000000000..85d8eb2ba2
--- /dev/null
+++ b/test/files/pos/bug4020.flags
@@ -0,0 +1 @@
+-Xfatal-warnings
diff --git a/test/files/pos/bug4020.scala b/test/files/pos/bug4020.scala
new file mode 100644
index 0000000000..f976460191
--- /dev/null
+++ b/test/files/pos/bug4020.scala
@@ -0,0 +1,25 @@
+class A {
+    sealed trait Foo
+}
+
+object a1 extends A {
+    case class Foo1(i: Int) extends Foo
+}
+
+object a2 extends A {
+    case class Foo2(i: Int) extends Foo
+}
+
+class B {
+    def mthd(foo: a2.Foo) = {
+        foo match {
+            case a2.Foo2(i) => i
+
+            // Note: This case is impossible.  In fact, scalac
+            // will (correctly) report an error if it is uncommented,
+            // but a warning if it is commented.
+
+            // case a1.Foo1(i) => i
+        }
+    }
+}
+\ No newline at end of file