[nullsafe] Make trust list operate over sets instead of lists

Summary:
1. Most of trust list operations are abstract anyway, we don't actually
rely on the fact that this is list
2. Inside NullsafeMode.ml, we effectively need set operations, which is both more
idiomatic to express and Ocaml and faster
3. This will simplify implementation of the next diff which introduces
mode intersect operation

Reviewed By: artempyanykh

Differential Revision: D21207207

fbshipit-source-id: 0c1fc4426

infer/src/IR/JavaClassName.ml

@@ -18,6 +18,12 @@ module Map = Caml.Map.Make (struct
   let compare = compare
 end)
 
+module Set = Caml.Set.Make (struct
+  type nonrec t = t
+
+  let compare = compare
+end)
+
 let make ~package ~classname =
   match package with Some "" -> {package= None; classname} | _ -> {package; classname}
 

infer/src/IR/JavaClassName.mli

@@ -11,6 +11,8 @@ type t [@@deriving compare, equal]
 
 module Map : Caml.Map.S with type key = t
 
+module Set : Caml.Set.S with type elt = t
+
 val make : package:string option -> classname:string -> t
 
 val from_string : string -> t

infer/src/nullsafe/ClassLevelAnalysis.ml

@@ -48,7 +48,7 @@ let mode_to_json = function
       `Default
   | NullsafeMode.Local NullsafeMode.Trust.All ->
       `LocalTrustAll
-  | NullsafeMode.Local (NullsafeMode.Trust.Only []) ->
+  | NullsafeMode.Local (NullsafeMode.Trust.Only names) when JavaClassName.Set.is_empty names ->
       `LocalTrustNone
   | NullsafeMode.Local (NullsafeMode.Trust.Only _) ->
       `LocalTrustSome
@@ -96,16 +96,22 @@ let make_meta_issue all_issues current_mode class_name =
       match mode_to_promote_to with
       | Some mode_to_promote_to ->
           (* This class is not @Nullsafe yet, but can become such! *)
+          let trust_none_mode =
+            "`@Nullsafe(value = Nullsafe.Mode.LOCAL, trustOnly = @Nullsafe.TrustList({}))`"
+          in
+          let trust_all_mode = "`@Nullsafe(Nullsafe.Mode.Local)`" in
           let promo_recommendation =
             match mode_to_promote_to with
             | NullsafeMode.Local NullsafeMode.Trust.All ->
-                "`@Nullsafe(Nullsafe.Mode.Local)`"
-            | NullsafeMode.Local (NullsafeMode.Trust.Only [])
+                trust_all_mode
+            | NullsafeMode.Local (NullsafeMode.Trust.Only names)
+              when JavaClassName.Set.is_empty names ->
+                trust_none_mode
             | NullsafeMode.Strict
             (* We don't recommend "strict" for now as it is harder to keep a class in strict mode than it "trust none" mode.
                Trust none is almost as safe alternative, but adding a dependency will require just updating trust list,
                without need to strictify it first. *) ->
-                "`@Nullsafe(value = Nullsafe.Mode.LOCAL, trustOnly = @Nullsafe.TrustList({}))`"
+                trust_none_mode
             | NullsafeMode.Default | NullsafeMode.Local (NullsafeMode.Trust.Only _) ->
                 Logging.die InternalError "Unexpected promotion mode"
           in

infer/src/nullsafe/Nullability.ml

@@ -49,7 +49,8 @@ let is_considered_nonnull ~nullsafe_mode nullability =
     match nullsafe_mode with
     | NullsafeMode.Strict ->
         StrictNonnull
-    | NullsafeMode.Local (NullsafeMode.Trust.Only []) ->
+    | NullsafeMode.Local (NullsafeMode.Trust.Only classes) when JavaClassName.Set.is_empty classes
+      ->
         (* Though "trust none" is technically a subcase of trust some,
            we need this pattern to be different from the one below so we can detect possible
            promotions from "trust some" to "trust none" *)

infer/src/nullsafe/NullsafeMode.ml

@@ -9,20 +9,23 @@ open! IStd
 module F = Format
 
 module Trust = struct
-  type t = All | Only of JavaClassName.t list [@@deriving compare, equal]
+  type t = All | Only of JavaClassName.Set.t [@@deriving compare, equal]
 
-  let none = Only []
+  let none = Only JavaClassName.Set.empty
 
   let extract_trust_list = function
     | Annot.Array class_values ->
         (* The only elements of this array can be class names; therefore short-circuit and return None if it's not the case. *)
-        IList.traverse_opt class_values ~f:(fun el ->
-            match el with
-            | Annot.Class class_typ ->
-                Typ.name class_typ
-                |> Option.map ~f:(fun name -> Typ.Name.Java.get_java_class_name_exn name)
-            | _ ->
-                None )
+        let trust_list =
+          IList.traverse_opt class_values ~f:(fun el ->
+              match el with
+              | Annot.Class class_typ ->
+                  Typ.name class_typ
+                  |> Option.map ~f:(fun name -> Typ.Name.Java.get_java_class_name_exn name)
+              | _ ->
+                  None )
+        in
+        Option.map trust_list ~f:JavaClassName.Set.of_list
     | _ ->
         None
 
@@ -47,15 +50,14 @@ module Trust = struct
         (* We are interested only in explicit lists *)
         false
     | Only classes ->
-        List.exists classes ~f:(JavaClassName.equal name)
+        JavaClassName.Set.exists (JavaClassName.equal name) classes
 
 
   let is_stricter ~stricter ~weaker =
-    let is_stricter_trust_list stricter_list weaker_list =
+    let is_stricter_trust_list stricter_set weaker_set =
       (* stricter trust list should be a strict subset of the weaker one *)
-      List.length stricter_list < List.length weaker_list
-      && List.for_all stricter_list ~f:(fun strict_name ->
-             List.exists weaker_list ~f:(fun name -> JavaClassName.equal name strict_name) )
+      JavaClassName.Set.cardinal stricter_set < JavaClassName.Set.cardinal weaker_set
+      && JavaClassName.Set.subset stricter_set weaker_set
     in
     match (stricter, weaker) with
     | All, All | All, Only _ ->
@@ -70,7 +72,7 @@ module Trust = struct
     match t with
     | All ->
         F.fprintf fmt "all"
-    | Only [] ->
+    | Only names when JavaClassName.Set.is_empty names ->
         F.fprintf fmt "none"
     | Only _names ->
         F.fprintf fmt "selected"

infer/src/nullsafe/NullsafeMode.mli

@@ -12,7 +12,7 @@ open! IStd
 module Trust : sig
   [@@@warning "-32"]
 
-  type t = All | Only of JavaClassName.t list [@@deriving compare, equal]
+  type t = All | Only of JavaClassName.Set.t [@@deriving compare, equal]
 
   val none : t