SI-9398 Treat case classes as one-element ADTs for analysis

Currently, exhaustivity analysis only runs for scrutinees with
a sealed type.

This commit treats any case class as a one-element, sealed type
to enable additional analysis, such as in the new test case.

15 files changed, 35 insertions, 12 deletions

diff --git a/src/compiler/scala/tools/nsc/transform/patmat/MatchAnalysis.scala b/src/compiler/scala/tools/nsc/transform/patmat/MatchAnalysis.scala
index 4286f69c96..ab3b25e76b 100644
--- a/src/compiler/scala/tools/nsc/transform/patmat/MatchAnalysis.scala
+++ b/src/compiler/scala/tools/nsc/transform/patmat/MatchAnalysis.scala
@@ -176,6 +176,8 @@ trait TreeAndTypeAnalysis extends Debugging {
               filterChildren(subclasses)
             })
           }
+        case sym if sym.isCase =>
+          List(List(tp))
 
         case sym =>
           debug.patmat("enum unsealed "+ ((tp, sym, sym.isSealed, isPrimitiveValueClass(sym))))
diff --git a/test/files/neg/t9398.check b/test/files/neg/t9398.check
new file mode 100644
index 0000000000..f0c464daa1
--- /dev/null
+++ b/test/files/neg/t9398.check
@@ -0,0 +1,7 @@
+match.scala:3: warning: match may not be exhaustive.
+It would fail on the following input: CC(B2)
+  def test(c: CC): Unit = c match {
+                          ^
+error: No warnings can be incurred under -Xfatal-warnings.
+one warning found
+one error found
diff --git a/test/files/neg/t9398.flags b/test/files/neg/t9398.flags
new file mode 100644
index 0000000000..85d8eb2ba2
--- /dev/null
+++ b/test/files/neg/t9398.flags
@@ -0,0 +1 @@
+-Xfatal-warnings
diff --git a/test/files/neg/t9398/data.scala b/test/files/neg/t9398/data.scala
new file mode 100644
index 0000000000..7a98c0e8e8
--- /dev/null
+++ b/test/files/neg/t9398/data.scala
@@ -0,0 +1,5 @@
+sealed abstract class TB
+case object B extends TB
+case object B2 extends TB
+
+case class CC(tb: TB)
diff --git a/test/files/neg/t9398/match.scala b/test/files/neg/t9398/match.scala
new file mode 100644
index 0000000000..e110c6a96a
--- /dev/null
+++ b/test/files/neg/t9398/match.scala
@@ -0,0 +1,6 @@
+class Test {
+  // Should warn that CC(B2) isn't matched
+  def test(c: CC): Unit = c match {
+    case CC(B) => ()
+  }
+}
diff --git a/test/files/pos/t5899.scala b/test/files/pos/t5899.scala
index b16f1f84fe..885baca790 100644
--- a/test/files/pos/t5899.scala
+++ b/test/files/pos/t5899.scala
@@ -14,6 +14,7 @@ trait Foo {
     Bippy(Stable) match {
       case Bippy(nme.WILDCARD) => 1
       case Bippy(Stable) => 2 // should not be considered unreachable
+      case Bippy(_) => 3
     }
   }
 }
\ No newline at end of file
diff --git a/test/files/run/Course-2002-07.scala b/test/files/run/Course-2002-07.scala
index 2d9457653f..db6e1d8e04 100644
--- a/test/files/run/Course-2002-07.scala
+++ b/test/files/run/Course-2002-07.scala
@@ -485,7 +485,7 @@ object MB {
   import Utils._;
 
 
-  trait Expr {
+  sealed trait Expr {
 
     private def count: Int = this match {
       case Lit(n)        => n
diff --git a/test/files/run/caseclasses.scala b/test/files/run/caseclasses.scala
index 668c984f3d..10c0916dc0 100644
--- a/test/files/run/caseclasses.scala
+++ b/test/files/run/caseclasses.scala
@@ -18,7 +18,7 @@ object M {
 object Test extends App {
 
   def Abs(x: Int) = new Abs(x * 2){}
-  Abs(2) match {
+  (Abs(2): @unchecked) match {
     case Abs(4) => ;
   }
 
diff --git a/test/files/run/infix.scala b/test/files/run/infix.scala
index a867d03ce8..1d39003644 100644
--- a/test/files/run/infix.scala
+++ b/test/files/run/infix.scala
@@ -7,5 +7,6 @@ object Test extends App {
   Console.println(xs)
   xs match {
     case null op (0, 0) op (1, 1) op (2, 2) => Console.println("OK")
+    case _ =>
   }
 }
diff --git a/test/files/run/patmatnew.scala b/test/files/run/patmatnew.scala
index 3c0d00dc6c..2647d97836 100644
--- a/test/files/run/patmatnew.scala
+++ b/test/files/run/patmatnew.scala
@@ -539,7 +539,7 @@ object Test {
     case class Operator(x: Int);
     val EQ = new Operator(2);
 
-    def analyze(x: Tuple2[Operator, Int]) = x match {
+    def analyze(x: Tuple2[Operator, Int]) = (x: @unchecked) match {
       case (EQ, 0) => "0"
       case (EQ, 1) => "1"
       case (EQ, 2) => "2"
@@ -603,7 +603,7 @@ object Test {
 
   object Bug1093 {
     def run() {
-      assert(Some(3) match {
+      assert((Some(3): @unchecked) match {
         case Some(1 | 2) => false
         case Some(3) => true
       })
diff --git a/test/files/run/t3126.scala b/test/files/run/t3126.scala
index 36322bf896..865047ce4f 100644
--- a/test/files/run/t3126.scala
+++ b/test/files/run/t3126.scala
@@ -4,6 +4,6 @@ object Test {
 
   def main(args: Array[String]): Unit = {
     try C.unapply(null) catch { case _: MatchError => }
-    try v match { case Some(1) => } catch { case _: MatchError => }
+    try ((v: @unchecked) match { case Some(1) => }) catch { case _: MatchError => }
   }
 }
diff --git a/test/files/run/t4124.scala b/test/files/run/t4124.scala
index 9f35b57ce3..db4e382634 100644
--- a/test/files/run/t4124.scala
+++ b/test/files/run/t4124.scala
@@ -2,22 +2,22 @@ import xml.Node
 
 object Test extends App {
   val body: Node = <elem>hi</elem>	
-  println ((body: AnyRef, "foo") match {
+  println (((body: AnyRef, "foo"): @unchecked) match {
     case (node: Node, "bar")        => "bye"
     case (ser: Serializable, "foo") => "hi"
   })
 
-  println ((body, "foo") match {
+  println (((body, "foo"): @unchecked) match {
     case (node: Node, "bar")        => "bye"
     case (ser: Serializable, "foo") => "hi"
   })
 
-  println ((body: AnyRef, "foo") match {
+  println (((body: AnyRef, "foo"): @unchecked) match {
     case (node: Node, "foo")        => "bye"
     case (ser: Serializable, "foo") => "hi"
   })
 
-  println ((body: AnyRef, "foo") match {
+  println (((body: AnyRef, "foo"): @unchecked) match {
     case (node: Node, "foo")        => "bye"
     case (ser: Serializable, "foo") => "hi"
   })
diff --git a/test/files/run/t6089.scala b/test/files/run/t6089.scala
index c72d7ba792..c42a9f68c6 100644
--- a/test/files/run/t6089.scala
+++ b/test/files/run/t6089.scala
@@ -3,7 +3,7 @@ case class Foo(x: Int)
 object Test {
   def bippo(result: Boolean): Boolean = result
   def bungus(m: Foo): Boolean         =
-    bippo(m match { case Foo(2) => bungus(m) })
+    bippo((m: @unchecked) match { case Foo(2) => bungus(m) })
 
   def main(args: Array[String]): Unit = try {
     bungus(Foo(0))
diff --git a/test/files/run/t7459f.scala b/test/files/run/t7459f.scala
index 63e2109560..5cd972129a 100644
--- a/test/files/run/t7459f.scala
+++ b/test/files/run/t7459f.scala
@@ -3,7 +3,7 @@ object Test extends App {
 
   case class FooSeq(x: Int, y: String, z: C*)
 
-  FooSeq(1, "a", new C()) match {
+  (FooSeq(1, "a", new C()): @unchecked) match {
     case FooSeq(1, "a", x@_* ) =>
       //println(x.toList)
       x.asInstanceOf[x.type]
diff --git a/test/junit/scala/tools/nsc/transform/patmat/PatmatBytecodeTest.scala b/test/junit/scala/tools/nsc/transform/patmat/PatmatBytecodeTest.scala
index cef27b4d87..ec4621b230 100644
--- a/test/junit/scala/tools/nsc/transform/patmat/PatmatBytecodeTest.scala
+++ b/test/junit/scala/tools/nsc/transform/patmat/PatmatBytecodeTest.scala
@@ -121,7 +121,7 @@ class PatmatBytecodeTest extends ClearAfterClass {
     val code =
       """case class Foo(x: Any, y: String)
         |class C {
-        |  def a = Foo(1, "a") match {
+        |  def a = (Foo(1, "a"): @unchecked) match {
         |    case Foo(_: String, y) => y
         |  }
         |}