Original bug ID: 4263
Reporter: nogin
Assigned to: ertai
Status: closed (set by @xavierleroy on 2010-04-29T12:18:05Z)
Resolution: fixed
Priority: normal
Severity: major
Version: 3.10+dev
Fixed in version: 3.10+dev
Category: -for Camlp4 use https://github.com/ocaml/camlp4/issues
Monitored by: nogin

Bug description

Currently Camlp4 AST defines the record patterns as

PaRec of loc and list (patt * patt)

and record expressions as

ExRec of Loc.t and binding and expr

where the binding can bind arbitrary patterns to expressions. This was not a big issue prior to 3.10, but now that 3.10 provides very powerful mapping and folding features, this seems a bit problematic. Namely, if I define a Camlp4 filter or an AST mapping function that affects patterns, the array labels will get affected as well, often in an undesired way.

Would it be better to have
PaRec of loc and list (ident * patt)
and
ExRec of loc and list (ident * expr) and expr
instead?

If so, it would seem that now is the time to make the change, as 3.10 is about to make major backwards-incompatible camlp4 changes anyway.