Re: scratch/accurate-warning-pos: Solid progress: the branch now bootstraps.

[Paul Eggert]

Yuri Khan wrote:
> A macro that has a 'position-aware property on
> it can be called directly on the position-annotated AST and expected
> to use ‘eq-with-position-information’; while a legacy macro will be
> called on a de-annotated AST, may use plain ‘eq’, and will return a
> similarly position-oblivious AST.

Thanks, this is a good suggestion, perhaps the best idea I've heard so far in 
this thread. Here are a few more suggestions on top of it.

1. We could have (equal A B) ignore position information in A and B; this would 
make it more convenient for macros to use existing code based on 'equal', and 
it'd mean we wouldn't need a new predicate eq-with-position-information. In one 
form of this idea, when A and B are symbols then (equal A B) acts like 
(string-equal (symbol-name A) (symbol-name B)), thus ignoring the distinction 
between interned and uninterned symbols. In another form of this idea, (equal A 
B) merely ignores position information.

2. Instead of having a bulky notation for new, position-aware macros, we could 
use a syntax that's shorter or simpler than what we have now, to make new-style 
macros more appealing. For example, we could use "defmac" to define new-style 
macros, and keep "defmacro" for old ones (we can say that the trailing "ro" 
stands for "region oblivious" :-).

3. If (2) is too drastic for you, we could have something like "(require 
'position-macros)" (or some other syntax) that tells the byte-compiler that all 
macros in this file are smart about positions; this would be more convenient 
than annotating each macro individually. Also, we could warn people that this is 
a transition approach, and that eventually the idea will be that position-macros 
will be the default and that if you want an old-style macro you need to 
explicitly annotate it as old-style.