More specific return type hints

[Emlyn Corrin]

When multiple overloads of a particular arity have different return types, we could look for the common superclass (or a common supertype) of all return types, instead of just hinting with Object.
If we include interfaces, then there will not necessarily be a single most specific common supertype. But in that case picking one is probably still better than just using Object. There could also be an option of a resolving function to give the user control in such situations.
There is some relevant discussion of this here and here.