I think I have convinced myself that this is expected behaviour, but perhaps we can add a warning in some documentation about how to properly annotate recursive types.
Given the following .ml file that uses our examples/simple-deriver, a user might quite reasonably apply a [@@deriving accessors] to each part of the recursive type (note is only recursive by the use of and not the types themselves).
type x = {
age : int
}[@@deriving accessors]
and y = {
name : string
}[@@deriving accessors]This generates the following code:
type x = {
age: int }[@@deriving accessors]
and y = {
name: string }[@@deriving accessors]
include
struct
let _ = fun (_ : x) -> ()
let _ = fun (_ : y) -> ()
let age x = x.age
let _ = age
let name x = x.name
let _ = name
let age x = x.age
let _ = age
let name x = x.name
let _ = name
end[@@ocaml.doc "@inline"][@@merlin.hide ]Of course, if one were to only add an annotation on one part of the recursive type then you would only get a single instance of the accessors. However, this is definitely happening in the wild, for example: https://git.frama-c.com/pub/frama-c/-/blob/master/src/kernel_services/ast_data/property.ml?ref_type=heads#L107 and (where this issue originally came from) ocaml-ppx/ppx_deriving#292. In general, I think when this does occur, recursive types tend to be rather large ASTs and so the code bloat is probably quite noticeable!
I think I have convinced myself that this is expected behaviour, but perhaps we can add a warning in some documentation about how to properly annotate recursive types.
Given the following
.mlfile that uses ourexamples/simple-deriver, a user might quite reasonably apply a[@@deriving accessors]to each part of the recursive type (note is only recursive by the use ofandnot the types themselves).This generates the following code:
Of course, if one were to only add an annotation on one part of the recursive type then you would only get a single instance of the accessors. However, this is definitely happening in the wild, for example: https://git.frama-c.com/pub/frama-c/-/blob/master/src/kernel_services/ast_data/property.ml?ref_type=heads#L107 and (where this issue originally came from) ocaml-ppx/ppx_deriving#292. In general, I think when this does occur, recursive types tend to be rather large ASTs and so the code bloat is probably quite noticeable!