Fix issue where uncurried async functions were emitted without async

Author: cristianoc

CHANGELOG.md

@@ -25,6 +25,7 @@
 - Fix location issue in error messages with JSX V4 where the multiple props types are defined https://github.com/rescript-lang/syntax/pull/655
 - Fix location issue in make function in JSX V4 that breaks dead code elimination https://github.com/rescript-lang/syntax/pull/660
 - Fix parsing (hence pretty printing) of expressions with underscore `_` and comments.
+- Fix issue where uncurried async functions were emitted without `async`
 
 # 10.1.0-alpha.2
 

jscomp/frontend/ast_async.ml

@@ -15,7 +15,7 @@ let add_async_attribute ~async (body : Parsetree.expression) =
     {
       body with
       pexp_attributes =
-        ({ txt = "async"; loc = Location.none }, PStr [])
+        ({ txt = "res.async"; loc = Location.none }, PStr [])
         :: body.pexp_attributes;
     }
   else body