Set incomplete `rootTreeOrProvider` in typer
Set incomplete `rootTreeOrProvider` in typer

During typer, set `rootTreeOrProvider` to be the typed class def. This
information will be overwritten in `SetRootTree` to include the whole
package structure, but we may never reach this phase.

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