Add Core standard library support for genType

See https://forum.rescript-lang.org/t/difficulty-with-shims-and-undefined-t-and-null-t/4240

Author: cristianoc

CHANGELOG.md

@@ -26,6 +26,7 @@ subset of the arguments, and return a curried type with the remaining ones https
 - Add support for toplevel `await` https://github.com/rescript-lang/rescript-compiler/pull/5940
 - Support optional named arguments without a final unit in uncurried functions https://github.com/rescript-lang/rescript-compiler/pull/5907
 - Add experimental suppport for directives. An annotation such as `@@directive("use client;")` emits `use client;` verbatim before imports https://github.com/rescript-lang/rescript-compiler/pull/5998
+- Add `Core` standard library support for `genType` https://github.com/rescript-lang/rescript-compiler/pull/6019
 
 #### :boom: Breaking Change
 

jscomp/gentype/Converter.ml

@@ -246,6 +246,9 @@ let typeGetConverterNormalized ~config ~inline ~lookupId ~typeNameIsInterface
       in
       (TupleC innerConversions, Tuple normalizedList)
     | TypeVar _ -> (IdentC, normalized_)
+    | Undefined t ->
+      let tConverter, tNormalized = t |> visit ~visited in
+      (OptionC tConverter, Undefined tNormalized)
     | Variant variant ->
       let allowUnboxed = not variant.polymorphic in
       let withPayloads, normalized, unboxed =

jscomp/gentype/EmitJs.ml

@@ -626,7 +626,7 @@ let propagateAnnotationToSubTypes ~codeItems (typeMap : CodeItem.exportTypeMap)
         retType |> visit
       | GroupOfLabeledArgs fields | Object (_, fields) | Record fields ->
         fields |> List.iter (fun {type_} -> type_ |> visit)
-      | Option t | Null t | Nullable t | Promise t -> t |> visit
+      | Option t | Null t | Nullable t | Promise t | Undefined t -> t |> visit
       | Tuple innerTypes -> innerTypes |> List.iter visit
       | TypeVar _ -> ()
       | Variant {inherits; payloads} ->

jscomp/gentype/EmitType.ml

@@ -157,6 +157,10 @@ let rec renderType ~(config : Config.t) ?(indent = None) ~typeNameIsInterface
       |> String.concat ", ")
     ^ "]"
   | TypeVar s -> s
+  | Undefined type_ ->
+    "(undefined | "
+    ^ (type_ |> renderType ~config ~indent ~typeNameIsInterface ~inFunType)
+    ^ ")"
   | Variant {inherits; noPayloads; payloads; polymorphic; unboxed} ->
     let inheritsRendered =
       inherits

jscomp/gentype/GenTypeCommon.ml

@@ -70,6 +70,7 @@ type type_ =
   | Record of fields
   | Tuple of type_ list
   | TypeVar of string
+  | Undefined of type_
   | Variant of variant
 
 and fields = field list
@@ -119,6 +120,7 @@ let typeIsObject type_ =
   | Record _ -> true
   | Tuple _ -> true
   | TypeVar _ -> false
+  | Undefined _ -> false
   | Variant _ -> false
 
 type label = Nolabel | Label of string | OptLabel of string

jscomp/gentype/TranslateTypeExprFromTypes.ml

@@ -201,9 +201,14 @@ let translateConstr ~config ~paramsTranslation ~(path : Path.t) ~typeEnv =
     {dependencies = []; type_ = EmitType.typeReactElement}
   | (["FB"; "option"] | ["option"]), [paramTranslation] ->
     {paramTranslation with type_ = Option paramTranslation.type_}
-  | (["Js"; "Null"; "t"] | ["Js"; "null"]), [paramTranslation] ->
+  | ( (["Js"; "Undefined"; "t"] | ["Undefined"; "t"] | ["Js"; "undefined"]),
+      [paramTranslation] ) ->
+    {paramTranslation with type_ = Undefined paramTranslation.type_}
+  | (["Js"; "Null"; "t"] | ["Null"; "t"] | ["Js"; "null"]), [paramTranslation]
+    ->
     {paramTranslation with type_ = Null paramTranslation.type_}
   | ( ( ["Js"; "Nullable"; "t"]
+      | ["Nullable"; "t"]
       | ["Js"; "nullable"]
       | ["Js"; "Null_undefined"; "t"]
       | ["Js"; "null_undefined"] ),

jscomp/gentype/TypeVars.ml

@@ -67,6 +67,7 @@ let rec substitute ~f type0 =
     match f s with
     | None -> type0
     | Some type1 -> type1)
+  | Undefined type_ -> Undefined (type_ |> substitute ~f)
   | Variant variant ->
     Variant
       {
@@ -94,7 +95,7 @@ let rec free_ type0 : StringSet.t =
     |> List.fold_left
          (fun s typeArg -> StringSet.union s (typeArg |> free_))
          StringSet.empty
-  | Null type_ | Nullable type_ -> type_ |> free_
+  | Null type_ | Nullable type_ | Undefined type_ -> type_ |> free_
   | Option type_ | Promise type_ -> type_ |> free_
   | Tuple innerTypes ->
     innerTypes

jscomp/gentype_tests/typescript-react-example/src/Core.bs.js

@@ -0,0 +1,25 @@
+/* TypeScript file generated from Core.res by genType. */
+/* eslint-disable import/first */
+
+
+// @ts-ignore: Implicit any on import
+import * as CoreBS__Es6Import from './Core.bs';
+const CoreBS: any = CoreBS__Es6Import;
+
+export const null0: (x:(null | number)) => (null | number) = CoreBS.null0;
+
+export const null1: (x:(null | number)) => (null | number) = CoreBS.null1;
+
+export const nullable0: (x:(null | undefined | number)) => (null | undefined | number) = CoreBS.nullable0;
+
+export const nullable1: (x:(null | undefined | number)) => (null | undefined | number) = CoreBS.nullable1;
+
+export const undefined0: (x:(undefined | number)) => (undefined | number) = function (Arg1: any) {
+  const result = CoreBS.undefined0((Arg1 == null ? undefined : Arg1));
+  return result
+};
+
+export const undefined1: (x:(undefined | number)) => (undefined | number) = function (Arg1: any) {
+  const result = CoreBS.undefined1((Arg1 == null ? undefined : Arg1));
+  return result
+};

jscomp/gentype_tests/typescript-react-example/src/Core.gen.tsx

@@ -0,0 +1,17 @@
+@genType
+let null0 = (x: Js.null<int>) => x
+
+@genType
+let null1 = (x: Null.t<int>) => x
+
+@genType
+let nullable0 = (x: Js.nullable<int>) => x
+
+@genType
+let nullable1 = (x: Nullable.t<int>) => x
+
+@genType
+let undefined0 = (x: Js.undefined<int>) => x
+
+@genType
+let undefined1 = (x: Undefined.t<int>) => x

jscomp/gentype_tests/typescript-react-example/src/Core.res

@@ -0,0 +1 @@
+type t<'a> = Js.null<'a>

jscomp/gentype_tests/typescript-react-example/src/Null.bs.js

@@ -0,0 +1 @@
+type t<'a> = Js.nullable<'a>

jscomp/gentype_tests/typescript-react-example/src/Null.res

@@ -0,0 +1 @@
+type t<'a> = Js.undefined<'a>