3 files changed, 37 insertions, 11 deletions
diff --git a/src/compiler/scala/tools/nsc/typechecker/SyntheticMethods.scala b/src/compiler/scala/tools/nsc/typechecker/SyntheticMethods.scala
index c855abd7fb..0917646f76 100644
--- a/src/compiler/scala/tools/nsc/typechecker/SyntheticMethods.scala
+++ b/src/compiler/scala/tools/nsc/typechecker/SyntheticMethods.scala
@@ -126,6 +126,13 @@ trait SyntheticMethods extends ast.TreeDSL {
       val method = syntheticMethod(nme.toString_, FINAL, makeNoArgConstructor(StringClass.tpe))
       typer typed { DEF(method) === LIT(clazz.name.decode) }
     }
+    def moduleHashCodeMethod: Tree = {
+      val method = syntheticMethod(nme.hashCode_, FINAL, makeNoArgConstructor(IntClass.tpe))
+      // The string being used as hashcode basis is also productPrefix.
+      val code   = clazz.name.decode.hashCode
+
+      typer typed { DEF(method) === LIT(code) }
+    }
 
     def forwardingMethod(name: Name, targetName: Name): Tree = {
       val target      = getMember(ScalaRunTimeModule, targetName)
@@ -262,6 +269,7 @@ trait SyntheticMethods extends ast.TreeDSL {
         )
         // methods for case objects only
         def objectMethods = List(
+          Object_hashCode -> (() => moduleHashCodeMethod),
           Object_toString -> (() => moduleToStringMethod)
         )
         // methods for both classes and objects
diff --git a/src/library/scala/runtime/ScalaRunTime.scala b/src/library/scala/runtime/ScalaRunTime.scala
index 5a20b72fcd..4d5f783d61 100644
--- a/src/library/scala/runtime/ScalaRunTime.scala
+++ b/src/library/scala/runtime/ScalaRunTime.scala
@@ -177,18 +177,26 @@ object ScalaRunTime {
   def _hashCode(x: Product): Int = {
     import scala.util.MurmurHash._
     val arr =  x.productArity
-    var h = startHash(arr)
-    var c = startMagicA
-    var k = startMagicB
-    var i = 0
-    while (i < arr) {
-      val elem = x.productElement(i)
-      h = extendHash(h, elem.##, c, k)
-      c = nextMagicA(c)
-      k = nextMagicB(k)
-      i += 1
+    // Case objects have the hashCode inlined directly into the
+    // synthetic hashCode method, but this method should still give
+    // a correct result if passed a case object.
+    if (arr == 0) {
+      x.productPrefix.hashCode
+    }
+    else {
+      var h = startHash(arr)
+      var c = startMagicA
+      var k = startMagicB
+      var i = 0
+      while (i < arr) {
+        val elem = x.productElement(i)
+        h = extendHash(h, elem.##, c, k)
+        c = nextMagicA(c)
+        k = nextMagicB(k)
+        i += 1
+      }
+      finalizeHash(h)
     }
-    finalizeHash(h)
   }
 
   /** Fast path equality method for inlining; used when -optimise is set.
diff --git a/test/files/run/bug4752.scala b/test/files/run/bug4752.scala
new file mode 100644
index 0000000000..3d5c166a7a
--- /dev/null
+++ b/test/files/run/bug4752.scala
@@ -0,0 +1,10 @@
+object Test {
+  object Bippy {
+    case object Dingus
+  }
+
+  def main(args: Array[String]): Unit = {
+    assert(None.## == "None".##, None)
+    assert(Test.Bippy.Dingus.## == "Dingus".##, Test.Bippy.Dingus)
+  }
+}