SI-8143 Regressions with override checks, private members

These regressed in e609f1f20b, which excluded all private methods from
overriding checks. We should only exclude private[this] members on the
low end of a pair, as was done before that commit, and, we must also
exclude private members on the high side.

Why? Warning: reverse engineered intuition follows.

We need to report an error when if a private method in a subclass
has matches a less-private method in the super class and report an
error, lest the user be fooled into thinking it might be invoked
virtually. On the other hand, adding a private method to a super
class shouldn't invalidate the choice names of public members in
its superclasses.

I've removed the test case added by that commit and will lodge a
reworked version of it that Paul provided as a new issue. That shows
a bug with qualified private + inheritance.

In addition, the expectation of `neg/accesses.check` is reverted
to its 2.10.3 version, which I believe is correct. When it was
changed in e609f1f20b it sprouted a variation, `neg/accesses-2`,
which has now changed behaviour. The intent of that test will
be captured in the aforementioned issue covering qualified private
inheritance.

4 files changed, 34 insertions, 2 deletions

diff --git a/test/files/neg/accesses.check b/test/files/neg/accesses.check
index 5a5e03233e..db58af12ce 100644
--- a/test/files/neg/accesses.check
+++ b/test/files/neg/accesses.check
@@ -1,3 +1,7 @@
+accesses.scala:23: error: overriding method f2 in class A of type ()Unit;
+ method f2 has weaker access privileges; it should not be private
+  private def f2(): Unit = ()
+              ^
 accesses.scala:24: error: overriding method f3 in class A of type ()Unit;
  method f3 has weaker access privileges; it should be at least protected
   private[p2] def f3(): Unit = ()
@@ -10,4 +14,4 @@ accesses.scala:26: error: overriding method f5 in class A of type ()Unit;
  method f5 has weaker access privileges; it should be at least protected[p1]
   protected[p2] def f5(): Unit
                     ^
-three errors found
+four errors found
diff --git a/test/files/neg/accesses2.check b/test/files/neg/accesses2.check
index 554a7b4c81..66cf9a116e 100644
--- a/test/files/neg/accesses2.check
+++ b/test/files/neg/accesses2.check
@@ -1,4 +1,12 @@
+accesses2.scala:6: error: overriding method f2 in class A of type ()Int;
+ method f2 has weaker access privileges; it should not be private
+    private def f2(): Int = 1
+                ^
 accesses2.scala:5: error: class B1 needs to be abstract, since method f2 in class A of type ()Int is not defined
   class B1 extends A {
         ^
-one error found
+accesses2.scala:9: error: overriding method f2 in class A of type ()Int;
+ method f2 has weaker access privileges; it should not be private
+    private def f2(): Int = 1
+                ^
+three errors found
diff --git a/test/files/neg/t8143a.check b/test/files/neg/t8143a.check
new file mode 100644
index 0000000000..4e11000a2a
--- /dev/null
+++ b/test/files/neg/t8143a.check
@@ -0,0 +1,5 @@
+t8143a.scala:2: error: overriding method f in class Foo of type => Int;
+ method f has weaker access privileges; it should not be private
+class Bar extends Foo { private def f = 10 }
+                                    ^
+one error found
diff --git a/test/files/neg/t8143a.scala b/test/files/neg/t8143a.scala
new file mode 100644
index 0000000000..4ec539e671
--- /dev/null
+++ b/test/files/neg/t8143a.scala
@@ -0,0 +1,15 @@
+class Foo { def f = 5 }
+class Bar extends Foo { private def f = 10 }
+
+
+class Foo1 { private def f = 5 }
+class Bar1 extends Foo1 { def f = 10 } // okay
+
+class Foo2 { private def f = 5 }
+class Bar2 extends Foo2 { private def f = 10 } // okay
+
+class Foo3 { private[this] def f = 5 }
+class Bar3 extends Foo3 { private def f = 10 } // okay
+
+class Foo4 { private def f = 5 }
+class Bar4 extends Foo4 { private[this] def f = 10 } // okay
\ No newline at end of file