Macro future proofing

[emberian]

(RFC was accepted and has been heavily amended since; current text is: https://github.com/rust-lang/rfcs/blob/master/text/0550-macro-future-proofing.md )

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Rendered

Implementation: https://github.com/cmr/rust/tree/macro-input-future-proofing

[emberian]

cc @pczarn @nikomatsakis @kmcallister

[emberian]

Forgot one, of course: =

[nrc]

Oh, and a massive +1 to the overall idea here.

[pczarn]

+1, I'm convinced this is necessary. Detailed futures of some NTs are a bit unclear, though.

[emberian]

rust-lang/rust#20563

[nrc]

@cmr are there any changes you'd like to make to this RFC before we merge it?

[emberian]

@nick29581 maybe. The algorithm here no longer reflects the implementation, and the follow sets are subtly incorrect.

[nrc]

@cmr Ok, ping me when you are happy and I'll merge it

[emberian]

@nick29581 this is ready.

[vadimcn]

@cmr, was there a reason for not including Semicolon on this list as well?
It's handy when defining matchers like $( fn $n:ident( $(p:ident : $t:ty),* ) -> $r:ty ; )* (note the trailing 'ty')

[emberian]

No, that was indeed an oversight

sent from my phone
On Jan 23, 2015 12:24 AM, "Vadim Chugunov" notifications@github.com wrote:

In text/0000-macro-future-proofing.md
#550 (comment):

•   continue, else, reject.
  

• 2. If T has the form $(...)U+ or $(...)U* for some token U, run

•   the algorithm on the contents with `F` set to `U`. If it accepts,
  

•   check that the last token in the sequence can be followed by `F`. If
  

•   so, accept. Otherwise, reject.
  

  +This algorithm should be run on every matcher in every macro_rules
  +invocation, with F as EOF. If it rejects a matcher, an error should be
  +emitted and compilation should not complete.
  +
  +The current legal fragment specifiers are: item, block, stmt, pat,
  +expr, ty, ident, path, meta, and tt.
  +
  +- FOLLOW(pat) = {FatArrow, Comma, Eq}
  +- FOLLOW(expr) = {FatArrow, Comma, Semicolon}
  +- FOLLOW(ty) = {Comma, FatArrow, Colon, Eq, Gt, Ident(as)}

@cmr https://github.com/cmr, was there a reason for not including
Semicolon on this list as well?
It's handy when defining matchers like $( fn $n:ident( $(p:ident :
$t:ty),* ) -> $r:ty ; )* (note the trailing 'ty')

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