Fix of too strict variance checking.
Fix of too strict variance checking.

When following an alias type, go directly to aliased type.
Going via the TypeAlias link causes the current variance ot be
narrowed to 0.

dotty-staging/dotty,som-snytt/dotty,lampepfl/dotty,dotty-staging/dotty,lampepfl/dotty,sjrd/dotty,lampepfl/dotty,sjrd/dotty,sjrd/dotty,dotty-staging/dotty,dotty-staging/dotty,som-snytt/dotty,lampepfl/dotty,sjrd/dotty,dotty-staging/dotty,densh/dotty,lampepfl/dotty,som-snytt/dotty,som-snytt/dotty,densh/dotty,sjrd/dotty,som-snytt/dotty