Instead, create a tree of Parsers all pointing to a top-level Parser.
All module imports and interfaces are stored at the top level, instead
of in a static map. This allows creating multiple IDL::Parsers in the
same process without them stepping on each others toes.
An "inherit attribute" calls an ancestor's getter with the same name,
but defines its own setter. Since a parent class's public methods are
exposed to child classes, we don't have to do any special handling here
to call the parent's methods, it just works. :^)
This requires a little explanation. The overload resolution algorithm,
where this is used, repeatedly has steps like this:
> Otherwise: if V is a platform object, and there is an entry in S that
> has one of the following types at position i of its type list,
> - an interface type that V implements
> - object
> - a nullable version of any of the above types
> - an annotated type whose inner type is one of the above types
> - a union type, nullable union type, or annotated union type that has
> one of the above types in its flattened member types
> then remove from S all other entries.
So, the API here tries to match that. We save the matching entry when
checking through them and then use that in `remove_all_other_entries()`.
Removing all those entries when all we actually care about is looking at
that one matching entry feels silly, but sticking to the spec is more
important while things are still half-implemented. :^)
As part of this, I've moved a couple of methods for checking for
null/undefined from UnionType to Type, and filled in more of their
steps.
This now detects more, and so causes us to hit a `TODO()` which is too
big for me to go after right now, so I've replaced that assertion with
a log message.
Track the kind of Type it is, and use that to provide some convenient
`is_foo()` / `as_foo()` methods. While I was at it, made these all
classes instead of structs and made their data private.
IDL function overload resolution requires knowing each IDL function's
parameters and their types at runtime. The simplest way to do that is
just to make the types the generator uses available to the runtime.
Parsing has moved to LibIDL, but code generation has not, since that is
very specific to WrapperGenerator.
