Add support for toplevel await.

Fixes #5925

Author: cristianoc

CHANGELOG.md

@@ -15,6 +15,9 @@
 #### :bug: Bug Fix
 - Fix implementation of directives https://github.com/rescript-lang/rescript-compiler/pull/6052
 
+#### :rocket: New Feature
+- Add support for toplevel `await` https://github.com/rescript-lang/rescript-compiler/pull/6054
+
 # 10.1.3
 
 #### :rocket: New Feature

jscomp/build_tests/super_errors/expected/await.res.expected

@@ -0,0 +1,11 @@
+
+  We've found a bug for you!
+  /.../fixtures/await.res:4:9-17
+
+  2 │ let foo = async () => {
+  3 │   let _ = ()
+  4 │   () => await a()
+  5 │ }
+  6 │ 
+
+  Await on expression not in an async context

jscomp/build_tests/super_errors/fixtures/await.res

@@ -0,0 +1,5 @@
+let a = async () => 3
+let foo = async () => {
+  let _ = ()
+  () => await a()
+}

jscomp/frontend/bs_builtin_ppx.ml

@@ -551,7 +551,7 @@ let rec structure_mapper (self : mapper) (stru : Ast_structure.t) =
 let mapper : mapper =
   {
     default_mapper with
-    expr = expr_mapper ~async_context:(ref false) ~in_function_def:(ref false);
+    expr = expr_mapper ~async_context:(ref true) ~in_function_def:(ref false);
     pat = pat_mapper;
     typ = typ_mapper;
     class_type = class_type_mapper;

jscomp/test/async_await.js

@@ -0,0 +1,44 @@
+'use strict';
+
+var Curry = require("../../lib/js/curry.js");
+var Caml_array = require("../../lib/js/caml_array.js");
+
+function next(n) {
+  return n + 1 | 0;
+}
+
+async function useNext(param) {
+  return 4;
+}
+
+function Make(I) {
+  var get = async function (key) {
+    return await Curry._1(I.get, key);
+  };
+  return {
+          get: get
+        };
+}
+
+async function topFoo(param) {
+  return 1;
+}
+
+var arr = [
+  1,
+  2,
+  3
+];
+
+var toplevelAwait = await topFoo(undefined);
+
+var toplevelAwait2 = Caml_array.get(arr, await topFoo(undefined));
+
+exports.next = next;
+exports.useNext = useNext;
+exports.Make = Make;
+exports.topFoo = topFoo;
+exports.arr = arr;
+exports.toplevelAwait = toplevelAwait;
+exports.toplevelAwait2 = toplevelAwait2;
+/* toplevelAwait Not a pure module */

jscomp/test/async_await.res

@@ -0,0 +1,18 @@
+@@uncurried
+
+let next = n => n + 1
+let useNext = async () => next(3)
+
+module type Impl = {
+  let get: string => Js.Promise.t<string>
+}
+
+module Make = (I: Impl) => {
+  let get = async (key) => await I.get(key)
+}
+
+let topFoo = async () => 1
+let arr = [1, 2, 3]
+
+let toplevelAwait = await topFoo()
+let toplevelAwait2 = arr[await topFoo()]

jscomp/test/build.ninja

@@ -273452,7 +273452,7 @@ let rec structure_mapper (self : mapper) (stru : Ast_structure.t) =
 let mapper : mapper =
   {
     default_mapper with
-    expr = expr_mapper ~async_context:(ref false) ~in_function_def:(ref false);
+    expr = expr_mapper ~async_context:(ref true) ~in_function_def:(ref false);
     pat = pat_mapper;
     typ = typ_mapper;
     class_type = class_type_mapper;

lib/4.06.1/unstable/js_compiler.ml

@@ -273452,7 +273452,7 @@ let rec structure_mapper (self : mapper) (stru : Ast_structure.t) =
 let mapper : mapper =
   {
     default_mapper with
-    expr = expr_mapper ~async_context:(ref false) ~in_function_def:(ref false);
+    expr = expr_mapper ~async_context:(ref true) ~in_function_def:(ref false);
     pat = pat_mapper;
     typ = typ_mapper;
     class_type = class_type_mapper;

lib/4.06.1/unstable/js_playground_compiler.ml

@@ -283849,7 +283849,7 @@ let rec structure_mapper (self : mapper) (stru : Ast_structure.t) =
 let mapper : mapper =
   {
     default_mapper with
-    expr = expr_mapper ~async_context:(ref false) ~in_function_def:(ref false);
+    expr = expr_mapper ~async_context:(ref true) ~in_function_def:(ref false);
     pat = pat_mapper;
     typ = typ_mapper;
     class_type = class_type_mapper;