Generalize OverridingPairs to SymbolPairs.

Increases your chance of knowing what is going on in
OverridingPairs. Introduces some new abstractions which I
hope for your own sakes you will put to use in some way:

  RelativeTo: operations relative to a prefix
  SymbolPair: two symbols being compared for something, and
    the enclosing class where the comparison is being performed

Fixed a minor bug with access by accident by way of more
principled pair analysis. See run/private-override.scala.

Upgraded the error message issued on certain conflicts
to give the line numbers of both conflicting methods, as
opposed to just one and you go hunting.

1 files changed, 17 insertions, 0 deletions

diff --git a/test/files/run/private-override.scala b/test/files/run/private-override.scala
new file mode 100644
index 0000000000..0a3f57f97c
--- /dev/null
+++ b/test/files/run/private-override.scala
@@ -0,0 +1,17 @@
+package test.p1.p2 {
+  abstract class A {
+    private[p2] def f2(): Int = 1
+  }
+  abstract class Other extends A {
+    // It's a private method - not a private[p2] method. Not a failed
+    // "weaker access privileges" override, a different namespace.
+    private def f2(): Int = super.f2() + 2
+    def go() = f2()
+  }
+}
+
+object Test extends test.p1.p2.Other {
+  def main(args: Array[String]): Unit = {
+    println(go())
+  }
+}