SI-8079 Only expand local aliases during variance checks

We've been flip-flopping on this one through the years, right
now we issue an two errors for the enclosed test.

After this commit, variance validation only expands aliases that
are `{private,protected}[this]`. The rest need not be expanded,
as we have already variance validated the RHS of the alias.

It also removes a seemingly incorrect check in `isLocalOnly`.

This also means that we can use `@uncheckedVariance` to create
variant type aliases for Java interfaces.

However, if such a type alias is declared private local, it
*will* be expanded. That shouldn't be a problem, other than
for the fact that we run through an as-seen-from that strips
the `@uV` annotations in the type expansion. This has been
recorded in a pending test.

1 files changed, 1 insertions, 1 deletions

diff --git a/test/files/neg/variances.check b/test/files/neg/variances.check
index cb1a60a632..3c1545a375 100644
--- a/test/files/neg/variances.check
+++ b/test/files/neg/variances.check
@@ -19,7 +19,7 @@ variances.scala:74: error: covariant type A occurs in contravariant position in
 variances.scala:89: error: covariant type T occurs in invariant position in type T of type A
     type A = T
          ^
-variances.scala:90: error: covariant type T occurs in contravariant position in type => test.TestAlias.B[C.this.A] of method foo
+variances.scala:90: error: covariant type A occurs in contravariant position in type => test.TestAlias.B[C.this.A] of method foo
     def foo: B[A]
         ^
 8 errors found