4 files changed, 30 insertions, 1 deletions
diff --git a/src/compiler/scala/tools/nsc/ast/parser/Parsers.scala b/src/compiler/scala/tools/nsc/ast/parser/Parsers.scala
index b8b8d1bffb..e4a042325c 100644
--- a/src/compiler/scala/tools/nsc/ast/parser/Parsers.scala
+++ b/src/compiler/scala/tools/nsc/ast/parser/Parsers.scala
@@ -796,8 +796,18 @@ trait Parsers extends NewScanners with MarkupParsers {
       }
       newLineOptWhenFollowedBy(LBRACE)
       atPos(pos) {
-        if (inToken == LBRACE)
+        if (inToken == LBRACE) {
+          // Warn if they are attempting to refine Unit; we can't be certain it's
+          // scala.Unit they're refining because at this point all we have is an
+          // identifier, but at a later stage we lose the ability to tell an empty
+          // refinement from no refinement at all.  See bug #284.
+          for (Ident(name) <- ts) name.toString match {
+            case "Unit" | "scala.Unit"  =>
+              warning("Detected apparent refinement of Unit; are you missing an '=' sign?")
+            case _ =>
+          }
           CompoundTypeTree(Template(ts.toList, emptyValDef, refinement()))
+        }
         else
           makeIntersectionTypeTree(ts.toList)
       }
diff --git a/test/files/neg/bug284.check b/test/files/neg/bug284.check
new file mode 100644
index 0000000000..7e54672365
--- /dev/null
+++ b/test/files/neg/bug284.check
@@ -0,0 +1,8 @@
+bug284.scala:2: warning: Detected apparent refinement of Unit; are you missing an '=' sign?
+    def f1(a: T): Unit { }
+                       ^
+bug284.scala:6: error: eof expected but '}' found.
+}
+^
+one warning found
+one error found
diff --git a/test/files/neg/bug284.scala b/test/files/neg/bug284.scala
new file mode 100644
index 0000000000..c1817466b5
--- /dev/null
+++ b/test/files/neg/bug284.scala
@@ -0,0 +1,6 @@
+trait B[T] {
+    def f1(a: T): Unit { }
+    def f2(a: T): Unit
+    def f3(a: T) { }
+  }
+}
+\ No newline at end of file
diff --git a/test/files/pos/bug284.scala b/test/files/pos/bug284.scala
new file mode 100644
index 0000000000..b5879fb3fe
--- /dev/null
+++ b/test/files/pos/bug284.scala
@@ -0,0 +1,5 @@
+trait B[T] {
+    def f1(a: T): Unit { }
+    def f2(a: T): Unit
+    def f3(a: T) { }
+}
+\ No newline at end of file