Better error reporting regarding main methods.

Now notices most things which look like main methods and says
something useful if they aren't usable as entry points.
Closes SI-4749.

1 files changed, 44 insertions, 0 deletions

diff --git a/test/files/neg/t4749.scala b/test/files/neg/t4749.scala
new file mode 100644
index 0000000000..0973c36097
--- /dev/null
+++ b/test/files/neg/t4749.scala
@@ -0,0 +1,44 @@
+package bippy {
+  object Fail1 {
+    def main(args: Array[String]): Any = ()
+  }
+
+  object Fail2 {
+    def main[T](args: Array[String]): T = null.asInstanceOf[T]
+  }
+
+  abstract class Bippy[T] {
+    def main(args: Array[String]): T = null.asInstanceOf[T]
+  }
+  object Fail3 extends Bippy[Unit] { }
+
+
+  object Fail4 {
+    def main(args: Array[String]): Unit = ()
+  }
+  trait Fail4 { }
+
+  object Fail5 extends Fail5 { }    
+  class Fail5 {
+    def main(args: Array[String]): Unit = ()
+  }
+
+  object Fail6 {
+    def main(args: Array[String]): Unit = ()
+  }
+  class Fail6 {
+    def main = "bippy"
+  }
+
+  object Win1 {
+    def main(args: Array[String]): Unit = ()
+  }
+  object Win2 extends Bippy[Unit] {
+    override def main(args: Array[String]): Unit = ()
+  }
+  trait WinBippy[T] {
+    def main(args: Array[String]): T = null.asInstanceOf[T]
+  }
+  object Win3 extends WinBippy[Unit] { }
+}
+