Improve cross-borrowing ergonomics

Many Rust users say that the ergonomics for borrowing / deref / reborrowing is poor, especially compared to how magically dot (a.f) will behave (with respect to how it auto-derefs and borrows a).

This issue is meant to act as a place to collect the various proposals that have been put forward to resolve this. I guess it might be thought of as a meta-issue, except that I think it will mostly be collecting references to RFC PR's, rather than other issues.

(My current plan is to try to put links to all the appropriate PR's into this description itself; people can feel free to refer back to this issue, but I'm not planning on annotating each PR with a link, especially since the list of references inserted by github can get somewhat polluted... I will also try to link to meeting minutes if I can find them.)

Proposals:

• #226
• #241
• #248

Relevant rust-lang/rust issues:

• rust-lang/rust/issues/13988

Relevant Meeting Snippets

• 2014/05/20 removal of cross-borrowing
• 2013/11/19 autoderef
• 2013/07/30 == and autoderef

Potentially relevant discuss links (pre-RFCs, etc):

• http://discuss.rust-lang.org/t/semi-explicit-coercion-control-with/520
• http://discuss.rust-lang.org/t/pre-rfc-add-a-coerce-trait-to-get-rid-of-the-as-slice-calls/415/4

Start with the proposals listed in this issue (#226, #241, and #248), then review the linked Rust issue and meeting snippets about cross-borrowing and autoderef. The issue is a collection point rather than a defined implementation task; completion would require an agreed proposal and clear scope.