Two improvements (or so I claim) to MatchErrors.

toString when constructing the exception: it need not be called
until/unless it is printed, which it may never be. 2) Include the name
of the class which triggered it. Don't tell me you haven't wanted that
as many times as I have.

(Sidebar on commit message semantics: I assume nobody interprets "no
review" to mean anything like "unreviewable decision!" It only means I'm
pretty sure the code does what I intended. The floor is always open.)

That said, no review.

1 files changed, 9 insertions, 3 deletions

diff --git a/src/library/scala/MatchError.scala b/src/library/scala/MatchError.scala
index 31783da4d3..5f0f7e2dfc 100644
--- a/src/library/scala/MatchError.scala
+++ b/src/library/scala/MatchError.scala
@@ -19,7 +19,13 @@ package scala
  *  @version 1.1, 05/03/2004
  *  @since   2.0
  */
-final class MatchError(msg: String) extends RuntimeException(msg) {
-  def this(obj: Any) =
-    this(if (null != obj) obj.toString() else "null")
+final class MatchError(obj: Any) extends RuntimeException {
+  /** There's no reason we need to call toString eagerly,
+   *  so defer it until getMessage is called.
+   */
+  private lazy val objString =
+    if (obj == null) "null"
+    else obj.toString() + " (of class " + obj.asInstanceOf[AnyRef].getClass.getName + ")"
+
+  override def getMessage() = objString
 }