After libsyntax, idents should be replaced by Names

[jbclements]

This is a FIXME issue; right now, an ident contains information used by expansion. After expansion, this is collapsed down to a single Name (an index into the interner). However, the downstream stuff in librustc refers to "ast::ident" everywhere. It would save space and time to just pass around one int rather than two, by replacing uses of "ident" with "Name". I don't know if I'll have time to do this. (Planning for my untimely demi^H^Hparture.)

[jbclements]

More details on the "right way" to fix this.

resolve.rs, generally speaking, builds tables and then resolves identifiers by looking things up in them. Sometimes, this lookup should respect renamings (e.g. lexical bindings). Other times, it shouldn't (e.g., module names).

during expansion, identifiers gain "syntax contexts"; at the end of expansion, each ident has a uint telling what name it started with, and what syntax context it occurred in. There's an operation called mtwt_resolve (that is, the "resolve" operation specified in the MTWT paper) that maps this to a new name.

Ideally, then, this mtwt_resolve would be called when building the tables of lexical bindings, and not called otherwise. This would probably be done by having most of the tables just map Names (that is, uint indexes into the interner) to whatever-it-is-they-map-to.

Currently, however, these tables all map idents to whatever-it-is. I should fix this, but frankly, I'm just scrambling to get through, so I'm taking the short-cut of using the existing data structure rather than updating them.

[pnkfelix]

For those following along, "the MTWT paper" presumably refers to "Macros That Work Together"

[bblum]

AIUI this is just an internal cleanup and possible performance issue. Nominating for no milestone; let's see if the triage committee agrees.

[pnkfelix]

(For what it's worth, I don't think "nominating for no-milestone" explicitly via the I-nominated tag for an Issue that already has no milestone is an appropriate use of the nomination protocoll. More specifically, IMO the triage committee should only be looking at tickets that need their milestone setting changed and where there exists some champion for that change. @graydon any thoughts on process here?)

[graydon]

Yeah, nomination means you think the milestone assignment should change. Removing label.

[emberian]

Triage: still a bunch of work to do on this.

[flaper87]

I started working on this, I'll keep doing so!