From 26bca73b09d29a7978acdda36d2f85478343f9f4 Mon Sep 17 00:00:00 2001
From: Paul Phillips <paulp@improving.org>
Date: Sun, 5 Jul 2009 23:22:43 +0000
Subject: Implemented proposed strategy for #1503 and mov...

Implemented proposed strategy for #1503 and moved test case out of
pending (and fixed it so it didn't throw a match error.)
---
 src/compiler/scala/tools/nsc/matching/ParallelMatching.scala |  5 ++++-
 test/files/run/castsingleton.check                           |  2 ++
 test/files/run/castsingleton.scala                           | 11 +++++++++++
 test/files/run/patmatnew.scala                               |  7 +++++--
 test/pending/run/castsingleton.check                         |  2 --
 test/pending/run/castsingleton.scala                         | 10 ----------
 6 files changed, 22 insertions(+), 15 deletions(-)
 create mode 100644 test/files/run/castsingleton.check
 create mode 100644 test/files/run/castsingleton.scala
 delete mode 100644 test/pending/run/castsingleton.check
 delete mode 100644 test/pending/run/castsingleton.scala

diff --git a/src/compiler/scala/tools/nsc/matching/ParallelMatching.scala b/src/compiler/scala/tools/nsc/matching/ParallelMatching.scala
index 7f7b492b79..1905cc31b5 100644
--- a/src/compiler/scala/tools/nsc/matching/ParallelMatching.scala
+++ b/src/compiler/scala/tools/nsc/matching/ParallelMatching.scala
@@ -1180,7 +1180,10 @@ trait ParallelMatching extends ast.TreeDSL {
             case v @ Constant(null) if isAnyRef(scrutTree.tpe)  => scrutTree ANY_EQ NULL
             case v                                              => scrutTree ANY_== Literal(v)
           }
-        case _: SingletonType if useEqTest                      => REF(tpe.termSymbol) ANY_== scrutTree
+        case _: SingletonType if useEqTest                      =>
+          // See ticket #1503 for why both these checks are necessary.
+          (REF(tpe.termSymbol) ANY_== scrutTree) AND (scrutTree IS tpe.widen)
+
         case _ if scrutTree.tpe <:< tpe && isAnyRef(tpe)        => scrutTree OBJ_!= NULL
         case _                                                  => scrutTree IS tpe
       })
diff --git a/test/files/run/castsingleton.check b/test/files/run/castsingleton.check
new file mode 100644
index 0000000000..49742281f0
--- /dev/null
+++ b/test/files/run/castsingleton.check
@@ -0,0 +1,2 @@
+L()
+L()
diff --git a/test/files/run/castsingleton.scala b/test/files/run/castsingleton.scala
new file mode 100644
index 0000000000..f907467741
--- /dev/null
+++ b/test/files/run/castsingleton.scala
@@ -0,0 +1,11 @@
+object Test extends Application {
+  case class L();
+  object N extends L();
+
+  def empty(xs : L) : Unit = xs match {
+    case x@N  => println(x); println(x);
+    case x    => println(x); println(x);
+  }
+
+  empty(L())
+}
diff --git a/test/files/run/patmatnew.scala b/test/files/run/patmatnew.scala
index a16f300414..0ab5e92099 100644
--- a/test/files/run/patmatnew.scala
+++ b/test/files/run/patmatnew.scala
@@ -876,8 +876,11 @@ object C {
     }
 
 override def runTest() {
-    assertTrue(empty( new L(Nil) ))
-    assertTrue(singleton( new L(List(1)) ))
+    // We no longer assert these are true, because they are no longer true!
+    // See ticket #1503 for details, but it is unsound to let L(Nil) be
+    // seen as an N by the LHS of a match.
+    // assertTrue(empty( new L(Nil) ))
+    // assertTrue(singleton( new L(List(1)) ))
 }
 
 }  // end Ticket346
diff --git a/test/pending/run/castsingleton.check b/test/pending/run/castsingleton.check
deleted file mode 100644
index 49742281f0..0000000000
--- a/test/pending/run/castsingleton.check
+++ /dev/null
@@ -1,2 +0,0 @@
-L()
-L()
diff --git a/test/pending/run/castsingleton.scala b/test/pending/run/castsingleton.scala
deleted file mode 100644
index 171b380dc9..0000000000
--- a/test/pending/run/castsingleton.scala
+++ /dev/null
@@ -1,10 +0,0 @@
-object Test extends Application {
-  case class L();
-  object N extends L();
-
-  def empty(xs : L) : Unit = xs match {
-    case x@N => println(x); println(x);
-  }
-
-  empty(L())
-}
-- 
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