syntax: Move ast_map into it's own crate

[erickt]

This lets us remove the arena dependency from libsyntax, which is unstable, and supports making libsyntax compile on beta/1.0 (#24518).

r? @alexcrichton

[alexcrichton]

r? @nikomatsakis, @pnkfelix, or @nrc, I don't mess around with compiler internals enough on this I think.

[nikomatsakis]

I have no objection, but I wonder if this should be a rustc crate? Seems pretty specific to the compiler.

[erickt]

@nikomatsakis: I had thought it could be useful for future syntax extensions, but I suppose if we go down that road we can always rename rustc_ast_map to syntax_ast_map. I'll change the name.

[richo]

I haven't touched this codebase in a long time (and even then it was super
experimental, I was just curious to see how feasible this approach was),
but are changes like this going to affect visibility for something like:
https://github.com/richo/commavm/blob/master/src/main.rs#L1-L5

On Sun, Apr 26, 2015 at 12:55 PM, Erick Tryzelaar notifications@github.com
wrote:

@nikomatsakis https://github.com/nikomatsakis: I had thought it could
be useful for future syntax extensions, but I suppose if we go down that
road we can always rename rustc_ast_map to syntax_ast_map. I'll change
the name.

—
Reply to this email directly or view it on GitHub
#24757 (comment).

[erickt]

@alexcrichton / @nikomatsakis: Updated the PR to rename this new package to rustc_ast_map.

@richo: As far as I can tell you're not using ast_map, so this shouldn't impact you. I suggest you check out syntex though, which hopefully will allow for syntax extensions in 1.0 :)

[nikomatsakis]

@bors r+ ecef439

[bors]

☔ The latest upstream changes (presumably #23606) made this pull request unmergeable. Please resolve the merge conflicts.

[bors]

🔒 Merge conflict

[nikomatsakis]

@bors r+

[bors]

📌 Commit 19f1a15 has been approved by nikomatsakis

[bors]

⌛ Testing commit 19f1a15 with merge 5770f07...

[bors]

💔 Test failed - auto-mac-64-nopt-t

[bors]

☔ The latest upstream changes (presumably #25323) made this pull request unmergeable. Please resolve the merge conflicts.

[Gankra]

@erickt ping (needs rebase)