The completer of a symbol defined by a member def or import (except ClassSymbols)
Sets all missing fields of given denotation
Intentionally left without
implicit ctx parameter. We need
to pick up the context at the point where the completer was created.
The context with which this completer was created
denot by overwriting its info with
denot is a compiler generated case class method that clashes
with a user-defined method in the same scope with a matching type.
If completed symbol is an enum value or a named class, register it as a child in all direct parent classes which are sealed.