CombinePipedModuleFunctionsAnalyzer

Problem

Subsequent collection functions like List.filter and List.map can sometimes be combined into List.choose.

let a b =
    b
    |> List.filter (fun x -> x < 20)
    |> List.map (fun y -> y * 2)

Fix

let a b =
    b
    |> List.choose (fun x -> if x < 20 then Some(x * 2) else None)

val a: b: int list -> int list

val b: int list

Multiple items
module List
from Microsoft.FSharp.Collections

--------------------
type List<'T> =
  | op_Nil
  | op_ColonColon of Head: 'T * Tail: 'T list
  interface IReadOnlyList<'T>
  interface IReadOnlyCollection<'T>
  interface IEnumerable
  interface IEnumerable<'T>
  member GetReverseIndex: rank: int * offset: int -> int
  member GetSlice: startIndex: int option * endIndex: int option -> 'T list
  static member Cons: head: 'T * tail: 'T list -> 'T list
  member Head: 'T
  member IsEmpty: bool
  member Item: index: int -> 'T with get
  ...

val filter: predicate: ('T -> bool) -> list: 'T list -> 'T list

val x: int

val map: mapping: ('T -> 'U) -> list: 'T list -> 'U list

val y: int

val choose: chooser: ('T -> 'U option) -> list: 'T list -> 'U list

union case Option.Some: Value: 'T -> Option<'T>

union case Option.None: Option<'T>