Improved an error message.

Closes SI-4319, no review.

Author: paulp

src/compiler/scala/tools/nsc/typechecker/Typers.scala

@@ -1121,9 +1121,9 @@ trait Typers extends Modes with Adaptations {
       if (!phase.erasedTypes) {
         for (ancestor <- clazz.ancestors find (_.isCase)) {
           unit.error(clazz.pos, (
-            "case class `%s' has case ancestor `%s'. Case-to-case inheritance is prohibited."+
-            " To overcome this limitation use extractors to pattern match on non-leaf nodes."
-          ).format(clazz, ancestor))
+            "case %s has case ancestor %s, but case-to-case inheritance is prohibited."+
+            " To overcome this limitation, use extractors to pattern match on non-leaf nodes."
+          ).format(clazz, ancestor.fullName))
         }
       }
     }

test/files/neg/caseinherit.check

@@ -1,10 +1,10 @@
-caseinherit.scala:2: error: case class `class B' has case ancestor `class A'. Case-to-case inheritance is prohibited. To overcome this limitation use extractors to pattern match on non-leaf nodes.
-case class B(y: Int) extends A(y)
-           ^
-caseinherit.scala:3: error: case class `object Bippy' has case ancestor `class A'. Case-to-case inheritance is prohibited. To overcome this limitation use extractors to pattern match on non-leaf nodes.
-case object Bippy extends A(55)
-            ^
-caseinherit.scala:6: error: case class `class Dingus' has case ancestor `class A'. Case-to-case inheritance is prohibited. To overcome this limitation use extractors to pattern match on non-leaf nodes.
-case class Dingus(y: Int) extends Innocent
-           ^
+caseinherit.scala:3: error: case class B has case ancestor foo.A, but case-to-case inheritance is prohibited. To overcome this limitation, use extractors to pattern match on non-leaf nodes.
+  case class B(y: Int) extends A(y)
+             ^
+caseinherit.scala:4: error: case object Bippy has case ancestor foo.A, but case-to-case inheritance is prohibited. To overcome this limitation, use extractors to pattern match on non-leaf nodes.
+  case object Bippy extends A(55)
+              ^
+caseinherit.scala:11: error: case class Dingus has case ancestor foo.A, but case-to-case inheritance is prohibited. To overcome this limitation, use extractors to pattern match on non-leaf nodes.
+  case class Dingus(y: Int) extends Innocent
+             ^
 three errors found

test/files/neg/caseinherit.scala

@@ -1,6 +1,13 @@
-case class A(x: Int)
-case class B(y: Int) extends A(y)
-case object Bippy extends A(55)
+package foo {
+  case class A(x: Int)
+  case class B(y: Int) extends A(y)
+  case object Bippy extends A(55)
+}
+import foo._
 
-class Innocent extends A(5)
-case class Dingus(y: Int) extends Innocent
+package bar {
+  class Blameless(x: Int)
+  class Innocent extends A(5)
+  case class Dingus(y: Int) extends Innocent
+  case object Hungle extends Blameless(5)
+}

test/files/neg/t0816.check

@@ -1,4 +1,4 @@
-t0816.scala:5: error: case class `class Ctest' has case ancestor `class Btest'. Case-to-case inheritance is prohibited. To overcome this limitation use extractors to pattern match on non-leaf nodes.
+t0816.scala:5: error: case class Ctest has case ancestor Btest, but case-to-case inheritance is prohibited. To overcome this limitation, use extractors to pattern match on non-leaf nodes.
 case class Ctest(override val data: String) extends Btest(data, true)
            ^
 one error found

test/files/neg/t425.check

@@ -1,4 +1,4 @@
-t425.scala:3: error: case class `class B' has case ancestor `class A'. Case-to-case inheritance is prohibited. To overcome this limitation use extractors to pattern match on non-leaf nodes.
+t425.scala:3: error: case class B has case ancestor Temp.A, but case-to-case inheritance is prohibited. To overcome this limitation, use extractors to pattern match on non-leaf nodes.
   case class B(override val x: Int, y: Double) extends A(x)
              ^
 one error found