[type-annos-observers] Comments on the Nov 7 specification

[Michael Ernst]

Eric-

Thanks for the followup; I appreciate it.

We are all agreed on "outside to inside" for generics; it is definitely
superior.

Your original message and my request for clarification was about nested
types.  "Outside to inside" is ambiguous for nested types, so I think we
should avoid that terminology.  For nested types, it seems there is merit
to having paths start at the main type, then proceeding to scoping
information -- which would be similar to the preferred "outside to inside"
approach that is used for generics.

		     Thanks,

		    -Mike


> Subject: Re: [type-annos-observers] Comments on the Nov 7 specification
> From: Eric Bruneton <ebruneton at free.fr>
> To: type-annotations-spec-comments at openjdk.java.net
> Date: Sat, 24 Nov 2012 17:28:47 +0100
>
> 20/11/2012 21:37, Michael Ernst wrote:
> > Eric Bruneton said:
> >
> >>  From an ASM point of view,
> >> ...
> >> The important
> >> point is that all paths should be "from outside to inside" (e.g. for nested
> >> types, the path should go from outer to inner, not the other way around as
> >> proposed in the Nov 7 specification).
> >
> > Eric, I'm willing to make this change, but I would like to be able to give
> > a more specific justification for the design choice.  Can you explain the
> > rationale, or what difference it makes to ASM?  Is the reason that the
> > identifiers appear left-to-right in the class file and you want to process
> > them in that order, or is it something else?
>
> Right, it's basically that. For instance, consider the problem of
> extracting the part of a type signature in the class file format
> (e.g. Ljava.util.Map<+Ljava.lang.String;Ljava.util.List<Ljava.lang.Object;>;>;)
> that corresponds to a given type_path. With 'outside to inside' paths, this
> can be done with a simple recursive function, like
> extract(signature,path)
> - if empty path return signature
> - otherwise parse the first signature element from the left, check conformity
>   with first path element, and call recursively with tail of signature and
>   tail of path.
>
> With 'inside to outside' paths, you have to parse the three inner types in
> the signature to realize that
> "inner_path{inner_path{inner_path{empty_path}}}", for instance, was in fact
> the first parsed type (then you either have to save state during parsing,
> or do another parsing pass).
>
> I'm not sure I'm clear, but I hope you get the idea.
>
> Eric