LevelAvoidMap

Return a (possibly fresh) type variable of a level no greater than maxLevel which is:

• lower-bounded by tp if variance >= 0
• upper-bounded by tp if variance <= 0 If this isn't possible, return the empty range.

Three deviations from standard derivedSelect:

1. We first try a widening conversion to the type's info with the original prefix. Since the original prefix is known to be a subtype of the returned prefix, this can improve results.
2. Then, if the approximation result is a singleton reference C#x.type, we replace by the widened type, which is usually more natural.
3. Finally, we need to handle the case where the prefix type does not have a member named tp.name anymmore. In that case, we need to fall back to Bot..Top.

Expand parameter reference corresponding to prefix pre; If the expansion is a wildcard parameter reference, convert its underlying bounds to a range, otherwise return the expansion.

Whether it is currently expanding bounds

It is used to avoid following LazyRef in F-Bounds

True iff all NamedTypes on this prefix are static

Can be overridden. By default, only the prefix is mapped.

Map this function over given type

Overridden in TypeOps.avoid

Returns a string representation of the object.

The default representation is platform dependent.

Try to widen a named type to its info relative to given prefix pre, where possible. The possible cases are listed inline in the code.

The type parameters of the constructor of this applied type. Overridden in OrderingConstraint's ConstraintAwareTraversal to take account of instantiations in the constraint that are not yet propagated to the instance types of type variables.

Use an alterate type tp that replaces a range. This can happen if the prefix of a Select is a range and the selected symbol is an alias type or a value with a singleton type. In both cases we can forget the prefix and use the symbol's type.