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Fix Function.prototype.apply.bind #7879

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Fix Function.prototype.apply.bind #7879

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1ec4772
[typing] Fix hello.apply.bind
goodmind Jul 2, 2019
e0a50e9
[typing] Remove copy-paste from FunProtoApplyT match
goodmind Jul 2, 2019
17225b0
[tests] Add Function.apply.bind tests
goodmind Jul 9, 2019
f99e5f5
[tests] Add arguments bind test
goodmind Jul 9, 2019
12429f3
[typing] Add partial application to FunProtoApplyT
goodmind Jul 9, 2019
1d65d5c
[tests] Fix partial arguments test
goodmind Jul 9, 2019
25594b3
[typing] Fix rebinding already applied function
goodmind Jul 9, 2019
981f523
[tests] Fix rebinding test
goodmind Jul 9, 2019
c56ab68
[typing] Remove argument from Function$Prototype$Apply
goodmind Jul 9, 2019
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10 changes: 8 additions & 2 deletions src/typing/debug_js.ml
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Expand Up @@ -170,11 +170,15 @@ and _json_of_t_impl json_cx t = Hh_json.(
| NullProtoT _
| ObjProtoT _
| FunProtoT _
| FunProtoApplyT _
| FunProtoApplyT (_, None)
| FunProtoBindT _
| FunProtoCallT _
-> []

| FunProtoApplyT (_, Some t) -> [
"thisType", _json_of_t json_cx t;
]

| DefT (_, _, FunT (static, proto, funtype)) -> [
"static", _json_of_t json_cx static;
"prototype", _json_of_t json_cx proto;
Expand Down Expand Up @@ -1794,9 +1798,11 @@ let rec dump_t_ (depth, tvars) cx t =
| NullProtoT _
| ObjProtoT _
| FunProtoT _
| FunProtoApplyT _
| FunProtoApplyT (_, None)
| FunProtoBindT _
| FunProtoCallT _ -> p t
| FunProtoApplyT (_, Some arg) ->
p ~extra:(kid arg) t
| DefT (_, trust, PolyT (_, tps, c, id)) -> p ~trust:(Some trust) ~extra:(spf "%s [%s] #%d"
(kid c)
(String.concat "; " (Core_list.map ~f:(fun tp -> tp.name) (Nel.to_list tps)))
Expand Down
19 changes: 15 additions & 4 deletions src/typing/flow_js.ml
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Expand Up @@ -5586,8 +5586,12 @@ let rec __flow cx ((l: Type.t), (u: Type.use_t)) trace =
(*******************************************)

(* resolves the arguments... *)
| FunProtoApplyT lreason,
CallT (use_op, reason_op, ({call_this_t = func; call_args_tlist; _} as funtype)) ->
| FunProtoApplyT (lreason, arg),
CallT (use_op, reason_op, ({call_this_t; call_args_tlist; _} as funtype)) ->
let func = match arg with
| Some t -> t
| None -> call_this_t
in
(* Drop the specific AST derived argument reasons. Our new arguments come
* from arbitrary positions in the array. *)
let use_op = match use_op with
Expand Down Expand Up @@ -5710,6 +5714,9 @@ let rec __flow cx ((l: Type.t), (u: Type.use_t)) trace =
) call_args_tlist;
rec_flow_t cx trace (l, call_tout)

| FunProtoApplyT (lreason, _), BindT (_, _, { call_this_t; call_tout; _ }, _) ->
rec_flow_t cx trace (FunProtoApplyT (lreason, Some call_this_t), call_tout)
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This doesn't look right. Look at the FunT _, BindT _ rule for guidance.

  1. The call_this_t field of the BindT use is the this type corresponding to the call of bind. E.g., x in x.bind(...). You want the first argument instead.
  2. Looking at FunT _, BindT _ as a guide, you'll notice some complexity missing from here. Specifically, the constraints involving ResolveSpreadsToMultiflowPartial. This is needed to figure out the full argument list in the presence of spread arguments.

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@goodmind goodmind Jul 9, 2019 •
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What first argument? This is forwarding From

declare var regularApply: $Function$Prototype$Apply;
const b = regularApply.bind(fn) // would be `$Function$Prototype$Apply<typeof fn>`

to $Function$Prototype$Apply<typeof fn>

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If you write a test, I think you will see what I mean. You want the first argument passed to the bind call, which is not call_this_t.

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Ah, sorry, my mistake -- I was confusing BindT with FunProtoBindT. You're right that call_this_t is the first parameter.

You do still need to do something with call_args_tlist, though.

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You mean something like this?

const appliedFn = Function.apply.bind(x); // ok
const reappliedFn = appliedFn.bind(y); // wrong
reappliedFn(null, [""]); // no error

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@goodmind goodmind Jul 9, 2019 •
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@samwgoldman I think you were right 😀

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@samwgoldman would this mean adding second argument with applied parameters? I think one argument is already too much


| _, BindT (_, _, { call_tout; _ }, true) ->
rec_flow_t cx trace (l, call_tout)

Expand Down Expand Up @@ -6512,7 +6519,7 @@ let rec __flow cx ((l: Type.t), (u: Type.use_t)) trace =
rec_flow cx trace (AnyT.make AnyError lreason, u);

(* Special cases of FunT *)
| FunProtoApplyT reason, _
| FunProtoApplyT (reason, _), _
| FunProtoBindT reason, _
| FunProtoCallT reason, _ ->
rec_flow cx trace (FunProtoT reason, u)
Expand Down Expand Up @@ -7296,9 +7303,13 @@ and any_propagated_use cx trace use_op any l =
covariant_flow ~use_op instance;
true

| FunProtoApplyT (_, Some t) ->
contravariant_flow ~use_op t;
true

(* These types have no negative positions in their lower bounds *)
| ExistsT _
| FunProtoApplyT _
| FunProtoApplyT (_, None)
| FunProtoBindT _
| FunProtoCallT _
| FunProtoT _
Expand Down
5 changes: 4 additions & 1 deletion src/typing/resolvableTypeJob.ml
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Expand Up @@ -247,7 +247,7 @@ and collect_of_type ?log_unresolved cx acc = function

| FunProtoBindT _
| FunProtoCallT _
| FunProtoApplyT _
| FunProtoApplyT (_, None)
| FunProtoT _
| NullProtoT _
| ObjProtoT _
Expand All @@ -258,6 +258,9 @@ and collect_of_type ?log_unresolved cx acc = function
->
acc

| FunProtoApplyT (_, Some t) ->
collect_of_type ?log_unresolved cx acc t

and collect_of_destructor ?log_unresolved cx acc = function
| NonMaybeType -> acc
| PropertyType _ -> acc
Expand Down
6 changes: 3 additions & 3 deletions src/typing/type.ml
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Expand Up @@ -93,7 +93,7 @@ module rec TypeTerm : sig
appears as an upper bound of an object type, otherwise the same. *)
| NullProtoT of reason

| FunProtoApplyT of reason (* Function.prototype.apply *)
| FunProtoApplyT of reason * t option (* Function.prototype.apply *)
| FunProtoBindT of reason (* Function.prototype.bind *)
| FunProtoCallT of reason (* Function.prototype.call *)

Expand Down Expand Up @@ -2140,7 +2140,7 @@ end = struct
| ExistsT reason -> reason
| InternalT (ExtendsT (reason, _, _)) -> reason
| FunProtoT reason -> reason
| FunProtoApplyT reason -> reason
| FunProtoApplyT (reason, _) -> reason
| FunProtoBindT reason -> reason
| FunProtoCallT reason -> reason
| KeysT (reason, _) -> reason
Expand Down Expand Up @@ -2303,7 +2303,7 @@ end = struct
| ExactT (reason, t) -> ExactT (f reason, t)
| ExistsT reason -> ExistsT (f reason)
| InternalT (ExtendsT (reason, t1, t2)) -> InternalT (ExtendsT (f reason, t1, t2))
| FunProtoApplyT (reason) -> FunProtoApplyT (f reason)
| FunProtoApplyT (reason, t1) -> FunProtoApplyT (f reason, t1)
| FunProtoT (reason) -> FunProtoT (f reason)
| FunProtoBindT (reason) -> FunProtoBindT (f reason)
| FunProtoCallT (reason) -> FunProtoCallT (f reason)
Expand Down
9 changes: 6 additions & 3 deletions src/typing/type_annotation.ml
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Expand Up @@ -852,9 +852,12 @@ let rec convert cx tparams_map = Ast.Type.(function
)

| "Function$Prototype$Apply" ->
check_type_arg_arity cx loc t_ast targs 0 (fun () ->
let reason = mk_reason RFunctionType loc in
reconstruct_ast (FunProtoApplyT reason) None
let reason = mk_reason RFunctionType loc in
(match convert_type_params () with
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i think this is the only place we'd allow a sometimes-parameterized generic. the most similar concept is having a default, but in that case you'd have to use an empty <> (https://flow.org/en/docs/types/generics/#toc-adding-defaults-to-parameterized-generics).

this feels like a new behavior that we should consider carefully. also, we should consider how it interacts with annotating this, because it might be closer to Function$Prototype$Apply<this=T> or whatever syntax we end up with for that -- we've gone back and forth about annotating this for functions as either function f(this: T, ...) or function f<this = T>(...) (cc @gabelevi )

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I like first one because it mirrors TypeScript

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How can I make this support <>?

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@mroch you can mimic second one with first one
type F<T> = (this: T) => void

| [t], targs ->
reconstruct_ast (FunProtoApplyT (reason, Some t)) targs
| _, targs ->
reconstruct_ast (FunProtoApplyT (reason, None)) targs
)

| "Function$Prototype$Bind" ->
Expand Down
6 changes: 5 additions & 1 deletion src/typing/type_mapper.ml
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Expand Up @@ -105,9 +105,13 @@ class virtual ['a] t = object(self)
| FunProtoT _
| ObjProtoT _
| NullProtoT _
| FunProtoApplyT _
| FunProtoApplyT (_, None)
| FunProtoBindT _
| FunProtoCallT _ -> t
| FunProtoApplyT (r, Some t') ->
let t'' = self#type_ cx map_cx t' in
if t'' == t' then t
else FunProtoApplyT (r, Some t'')
| AnyWithLowerBoundT t' ->
let t'' = self#type_ cx map_cx t' in
if t'' == t' then t
Expand Down
6 changes: 5 additions & 1 deletion src/typing/type_visitor.ml
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Expand Up @@ -32,13 +32,17 @@ class ['a] t = object(self)
acc

| FunProtoT _
| FunProtoApplyT _
| FunProtoApplyT (_, None)
| FunProtoBindT _
| FunProtoCallT _
| ObjProtoT _
| NullProtoT _
-> acc

| FunProtoApplyT (_, Some t) ->
let acc = self#type_ cx pole acc t in
acc

| CustomFunT (_, kind) -> self#custom_fun_kind cx acc kind

| EvalT (t, defer_use_t, id) ->
Expand Down