With F# 8, the following code generates an FS3570 warning about ambiguous "", even though there is only one use of "" (_.Add(k)):
open System.Collections.Generic
module Map =
let update empty k f m =
match Map.tryFind k m with
| Some v -> Map.add k (f v) m
| None -> Map.add k (f empty) m
let invert (dict: IDictionary<'k,#seq<'k>>): Map<'k,Set<'k>> =
(Map.empty, dict)
||> Seq.fold (fun res (KeyValue (k, ks)) ->
(res, ks)
||> Seq.fold (fun res vk -> res |> Map.update Set.empty vk _.Add(k))
)
Rewriting to remove the (|KeyValue|) active pattern gets rid of the warning:
let invert (dict: IDictionary<'k,#seq<'k>>): Map<'k,Set<'k>> =
(Map.empty, dict)
||> Seq.fold (fun res kvp ->
(res, kvp.Value)
||> Seq.fold (fun res vk -> res |> Map.update Set.empty vk _.Add(kvp.Key))
)
With F# 8, the following code generates an FS3570 warning about ambiguous "", even though there is only one use of "" (
_.Add(k)):Rewriting to remove the
(|KeyValue|)active pattern gets rid of the warning: