Fix 'Unbound module type' errors that occurred when trying to async import modules (#7783)

* Fix 'Unbound module type' error that occurred when awaiting module in async function with return type constraint

* Fix 'Unbound module type' error that occurred when awaiting module in switch case

* Add CHANGELOG entry

* Add type annotation to case instead of using case.Parsetree.pc_rhs syntax

Author: mediremi

CHANGELOG.md

@@ -27,6 +27,7 @@
 - Preserve `@as(...)` decorator on record fields when creating interface. https://github.com/rescript-lang/rescript/pull/7779
 - Fix parse error with nested record types and attributes on the field name that has the nested record type. https://github.com/rescript-lang/rescript/pull/7781
 - Fix ppx resolution with package inside monorepo. https://github.com/rescript-lang/rescript/pull/7776
+- Fix 'Unbound module type' errors that occurred when trying to async import modules. https://github.com/rescript-lang/rescript/pull/7783
 
 #### :memo: Documentation
 

compiler/frontend/bs_builtin_ppx.ml

@@ -568,6 +568,14 @@ let rec structure_mapper ~await_context (self : mapper) (stru : Ast_structure.t)
               aux then_expr @ aux else_expr
             | Pexp_construct (_, Some expr) -> aux expr
             | Pexp_fun {rhs = expr} | Pexp_newtype (_, expr) -> aux expr
+            | Pexp_constraint (expr, _) -> aux expr
+            | Pexp_match (expr, cases) ->
+              let case_results =
+                List.fold_left
+                  (fun acc (case : Parsetree.case) -> aux case.pc_rhs @ acc)
+                  [] cases
+              in
+              aux expr @ case_results
             | _ -> acc
           in
           aux pvb_expr @ spelunk_vbs acc tl

tests/tests/src/Import.mjs

@@ -120,6 +120,19 @@ async function f7() {
   return 1;
 }
 
+async function f8() {
+  await import("rescript/lib/es6/Belt_MutableQueue.js");
+  return 1;
+}
+
+async function f9(value) {
+  if (value !== undefined) {
+    await import("rescript/lib/es6/Belt_HashMapInt.js");
+    return;
+  }
+  
+}
+
 let each = M1.forEach;
 
 let M2;
@@ -145,5 +158,7 @@ export {
   f5,
   f6,
   f7,
+  f8,
+  f9,
 }
 /*  Not a pure module */

tests/tests/src/Import.res

@@ -90,3 +90,17 @@ let f7 = async () => {
     0
   }
 }
+
+let f8 = async (): int => {
+  module MQ = await Belt.MutableQueue
+  1
+}
+
+let f9 = async value => {
+  switch value {
+  | Some(_) =>
+    module HashMapInt = await Belt.HashMap.Int
+    ()
+  | None => ()
+  }
+}