refactor Tast_env.get_member to be explicit

Summary:
## What

Rather than using a unlabeled boolean to decide which function to call, break get_member into two functions.

## Why

- safer (harder to mix up)
- a step toward consistency in the codebase

## Context

This came up in diff review for another diff https://www.internalfb.com/diff/D78688689?dst_version_fbid=1237203468181760&transaction_fbid=1405234473924772

## Alternative considered

I considered using a labeled parameter, but
- This would make it so that we have three patterns in the code base for the same thing, rather than just two.
- I think it's generally good practice to use normal function dispatch

Reviewed By: madgen

Differential Revision: D79905615

fbshipit-source-id: 95e7171d1d288e183df7fbf5ac1d4c1aa87fdc5a

Author: mheiber

hphp/hack/src/typing/env/typing_env.ml

@@ -942,18 +942,22 @@ module M = struct
     in
     suggest_member members mid
 
-  let get_member is_method env (class_ : Cls.t) mid =
+  let get_method env (class_ : Cls.t) mid =
     (* The type of a member is stored separately in the heap. This means that
      * any user of the member also has a dependency on the class where the member
      * originated.
      *)
-    let ce_opt =
-      if is_method then
-        Cls.get_method class_ mid [@alert "-dependencies"]
-      else
-        Cls.get_prop class_ mid [@alert "-dependencies"]
-    in
-    Deps.add_member_dep ~is_method ~is_static:false env class_ mid ce_opt;
+    let ce_opt = (Cls.get_method class_ mid [@alert "-dependencies"]) in
+    Deps.add_member_dep ~is_method:true ~is_static:false env class_ mid ce_opt;
+    ce_opt
+
+  let get_prop env (class_ : Cls.t) mid =
+    (* The type of a member is stored separately in the heap. This means that
+     * any user of the member also has a dependency on the class where the member
+     * originated.
+     *)
+    let ce_opt = (Cls.get_prop class_ mid [@alert "-dependencies"]) in
+    Deps.add_member_dep ~is_method:false ~is_static:false env class_ mid ce_opt;
     ce_opt
 
   let suggest_member is_method class_ mid =

hphp/hack/src/typing/env/typing_env.mli

@@ -49,8 +49,11 @@ module Expose_to_tast_env : sig
   (** Get class constants declaration from the appropriate backend and add dependency. *)
   val consts : env -> class_decl -> (string * class_const) list
 
-  (** Get class member declaration from the appropriate backend and add dependency. *)
-  val get_member : bool -> env -> class_decl -> string -> class_elt option
+  (** Get class method declaration from the appropriate backend and add dependency. *)
+  val get_method : env -> class_decl -> string -> class_elt option
+
+  (** Get class property declaration from the appropriate backend and add dependency. *)
+  val get_prop : env -> class_decl -> string -> class_elt option
 
   (** Get static member declaration of a class from the appropriate backend and add dependency. *)
   val get_static_member :

hphp/hack/src/typing/folded_class.mli

@@ -126,7 +126,7 @@ val get_typeconst : t -> string -> typeconst_type option
 val get_prop : t -> string -> class_elt option
   [@@alert
     dependencies
-      "Direct use of `get_prop` will not register a dependency. You probably want to use `Typing_env.get_member` instead"]
+      "Direct use of `get_prop` will not register a dependency. You probably want to use `Typing_env.get_prop` instead"]
 
 val get_sprop : t -> string -> class_elt option
   [@@alert
@@ -136,7 +136,7 @@ val get_sprop : t -> string -> class_elt option
 val get_method : t -> string -> class_elt option
   [@@alert
     dependencies
-      "Direct use of `get_method` will not register a dependency. You probably want to use `Typing_env.get_member` instead"]
+      "Direct use of `get_method` will not register a dependency. You probably want to use `Typing_env.get_method` instead"]
 
 val get_smethod : t -> string -> class_elt option
   [@@alert

hphp/hack/src/typing/nastInitCheck.ml

@@ -68,8 +68,7 @@ let lookup_props env class_name props =
           else
             Typing_env.get_class env class_name
             |> Decl_entry.to_option
-            |> Option.bind ~f:(fun cls ->
-                   Typing_env.get_member false env cls name)
+            |> Option.bind ~f:(fun cls -> Typing_env.get_prop env cls name)
             |> Option.bind ~f:(fun ce ->
                    Some (Lazy.force ce.Typing_defs.ce_type))
         in

hphp/hack/src/typing/tast_check/const_write_check.ml

@@ -24,7 +24,7 @@ let check_static_const_prop tenv class_ (pos, id) =
 
 (* Requires id to be a property *)
 let check_const_prop env tenv class_ (pos, id) cty =
-  let cprop = Typing_env.get_member false tenv class_ id in
+  let cprop = Typing_env.get_prop tenv class_ id in
   Option.iter cprop ~f:(fun ce ->
       if get_ce_const ce then
         if

hphp/hack/src/typing/typing.ml

@@ -5213,7 +5213,7 @@ end = struct
       let* dsl_name = dsl_opt in
       let* cls = Env.get_class env dsl_name |> Decl_entry.to_option in
       let* { ce_type = (lazy fun_ty); _ } =
-        Env.get_member true env cls SN.ExpressionTrees.splice
+        Env.get_method env cls SN.ExpressionTrees.splice
       in
       (* Pull the type of third argument to `MyDsl::splice()`.
          If we change the number of arguments this method takes, we might need to
@@ -8882,7 +8882,7 @@ end = struct
       let expr = ((), pos, expr_) in
       unbound_name env class_name expr
     | Decl_entry.Found folded_class -> begin
-      match Env.get_member true env folded_class (snd method_name) with
+      match Env.get_method env folded_class (snd method_name) with
       | None ->
         let () =
           let err = unbound_method class_name method_name folded_class in

hphp/hack/src/typing/typing_extends.ml

@@ -827,7 +827,7 @@ let maybe_poison_ancestors
         | Decl_entry.NotYetAvailable ->
           (child_class, child_return_ty)
         | Decl_entry.Found c ->
-          (match Env.get_member true env c member_name with
+          (match Env.get_method env c member_name with
           | None -> (child_class, child_return_ty)
           | Some elt ->
             let (lazy fty) = elt.ce_type in

hphp/hack/src/typing/typing_exts.ml

@@ -58,8 +58,8 @@ let lookup_magic_type (env : env) use_pos (class_ : locl_ty) (fname : string) :
     let ce_type =
       let lookup_def c =
         Option.first_some
-          (Env.get_member true env c fname)
-          (Env.get_member true env c "format_wild")
+          (Env.get_method env c fname)
+          (Env.get_method env c "format_wild")
       in
       Env.get_class env className |> Decl_entry.to_option >>= lookup_def
       >>= fun { ce_type = (lazy ty); ce_pos = (lazy pos); _ } ->

hphp/hack/src/typing/typing_object_get.ml

@@ -222,7 +222,12 @@ let sound_dynamic_err_opt args env ((_, id_str) as id) read_context =
   | Decl_entry.Found self_class
     when Cls.get_support_dynamic_type self_class || not (Cls.final self_class)
     ->
-    (match Env.get_member args.is_method env self_class id_str with
+    (match
+       if args.is_method then
+         Env.get_method env self_class id_str
+       else
+         Env.get_prop env self_class id_str
+     with
     | Some { ce_visibility = Vprivate _; ce_type = (lazy ty); _ }
       when not args.is_method ->
       if read_context then
@@ -274,7 +279,12 @@ let widen_class_for_obj_get ~is_method ~nullsafe member_name env ty =
       | Decl_entry.NotYetAvailable ->
         default ()
       | Decl_entry.Found class_info ->
-        (match Env.get_member is_method env class_info member_name with
+        (match
+           if is_method then
+             Env.get_method env class_info member_name
+           else
+             Env.get_prop env class_info member_name
+         with
         | Some { ce_origin; _ } ->
           (* If this member was inherited then we obtain the type from which
            * it is inherited as our wider type *)
@@ -534,7 +544,12 @@ and obj_get_concrete_class
       else
         (env, params)
     in
-    let old_member_info = Env.get_member args.is_method env class_info id_str in
+    let old_member_info =
+      if args.is_method then
+        Env.get_method env class_info id_str
+      else
+        Env.get_prop env class_info id_str
+    in
     let self_id = Option.value (Env.get_self_id env) ~default:"" in
     let ancestor_tyargs =
       match Cls.get_ancestor class_info self_id with
@@ -565,7 +580,12 @@ and obj_get_concrete_class
         | Decl_entry.NotYetAvailable ->
           (old_member_info, false)
         | Decl_entry.Found self_class -> begin
-          match Env.get_member args.is_method env self_class id_str with
+          match
+            if args.is_method then
+              Env.get_method env self_class id_str
+            else
+              Env.get_prop env self_class id_str
+          with
           | Some ({ ce_visibility = Vprivate _; _ } as ce) ->
             let ce =
               Decl_instantiate.(