SI-7912 Be defensive calling `toString` in `MatchError#getMessage`

Otherwise, objects with exception-throwing `toString` lead to a
cascading error far removed from the originally failed match.

1 files changed, 16 insertions, 0 deletions

diff --git a/test/files/run/t7912.scala b/test/files/run/t7912.scala
new file mode 100644
index 0000000000..3d603e0e97
--- /dev/null
+++ b/test/files/run/t7912.scala
@@ -0,0 +1,16 @@
+case object A { override def toString = ??? }
+
+object Test {
+  def foo: Int = (A: Any) match {
+    case 0 => 0
+  }
+  def main(args: Array[String]): Unit = {
+    try {
+      foo
+      sys.error("no exception")
+    } catch {
+      case me: MatchError => assert(me.getMessage == "an instance of class A$", me.getMessage)
+      case ex: Throwable => sys.error("not a match error: " + ex.getClass)
+    }
+  }
+}