Original bug ID: 7491
Reporter: @gasche
Assigned to: @gasche
Status: resolved (set by @gasche on 2017-02-22T15:42:28Z)
Resolution: suspended
Priority: low
Severity: feature
Target version: undecided
Category: ~DO NOT USE (was: OCaml general)
Monitored by: @yallop @hcarty

Bug description

Deep record field replacement extends the record-replacement construction { r with f1 = e1; f2 = e2 } to support nested field accesses { r with p1 = e1; p2 = e2 }, where the ps are field paths (f.g.h). For example

{ r with f.g = e1; f.h = e2; i = e3 }

Conflicting assignments should be rejected statically. Two paths p1, p2 are in conflict when one is a prefix of the other (in particular if they are equal).

There an uncertainty on whether there should be a specified evaluation order on the values; the implementation should probably be consistent with the behavior of the non-extended construction.

Additional information

This feature was proposed by Romain Bardou in

#291

with an unsatisfying implementation and some uncertainties about the specification. Alain Frisch pointed out that Lexifi's dialect used to have this extension, and that he would be interested in having it again. See the discussion in #291: the general feedback on the feature is positive, but it was pointed out that a robust implementation would require playing with the record-typechecking code, and is expected to be difficult.