Fix compilation failure by refining adaptation of constants
Fix compilation failure by refining adaptation of constants

Constants that are adapted to a different supertype need to do this
explicitly (not just by changing the type). Otherwise tree checkers
will compute the original type and fail.

This caused a test failure in pos/harmonize. The mystery is why this
was not caught in the checkin tests.

reactormonk/dotty,lampepfl/dotty,dotty-staging/dotty,VladimirNik/dotty,lampepfl/dotty,som-snytt/dotty,som-snytt/dotty,folone/dotty,svalaskevicius/dotty,yusuke2255/dotty,vsalvis/dotty,sjrd/dotty,yusuke2255/dotty,som-snytt/dotty,spetz911/dotty,densh/dotty,dotty-staging/dotty,som-snytt/dotty,auvik/dotty,angi2/dotty,lampepfl/dotty,spetz911/dotty,svalaskevicius/dotty,angi2/dotty,vsalvis/dotty,lampepfl/dotty,densh/dotty,lampepfl/dotty,sjrd/dotty,sjrd/dotty,dotty-staging/dotty,folone/dotty,sjrd/dotty,auvik/dotty,reactormonk/dotty,VladimirNik/dotty,sjrd/dotty,dotty-staging/dotty,som-snytt/dotty,dotty-staging/dotty