Fix issue where async as an id cannot be used with application and la… (#708)

* Fix issue where async as an id cannot be used with application and labelled arguments.

Fixes #707

* Add parsing test.

Author: cristianoc

CHANGELOG.md

@@ -49,6 +49,8 @@
 - Fix issue where printing nested pipe discards await https://github.com/rescript-lang/syntax/issues/687
 - Fix issue where the JSX key type is not an optional string https://github.com/rescript-lang/syntax/pull/693
 - Fix issue where the JSX fragment withouth children build error https://github.com/rescript-lang/syntax/pull/704
+- Fix issue where async as an id cannot be used with application and labelled arguments https://github.com/rescript-lang/syntax/issues/707
+
 
 #### :eyeglasses: Spec Compliance
 

src/res_core.ml

@@ -232,9 +232,13 @@ let rec goToClosing closingToken state =
 (* Madness *)
 let isEs6ArrowExpression ~inTernary p =
   Parser.lookahead p (fun state ->
-      (match state.Parser.token with
-      | Lident "async" -> Parser.next state
-      | _ -> ());
+      let async =
+        match state.Parser.token with
+        | Lident "async" ->
+          Parser.next state;
+          true
+        | _ -> false
+      in
       match state.Parser.token with
       | Lident _ | Underscore -> (
         Parser.next state;
@@ -275,7 +279,7 @@ let isEs6ArrowExpression ~inTernary p =
           | EqualGreater -> true
           | _ -> false)
         | Dot (* uncurried *) -> true
-        | Tilde -> true
+        | Tilde when not async -> true
         | Backtick ->
           false
           (* (` always indicates the start of an expr, can't be es6 parameter *)

tests/parsing/grammar/expressions/async.res

@@ -26,4 +26,7 @@ let async = {
     result->async->mapAsync(a => doStuff(a))
 }
 
-let f = isPositive ? (async (a, b) : int => a + b) : async (c, d) : int => c - d
+let f = isPositive ? (async (a, b) : int => a + b) : async (c, d) : int => c - d
+
+let foo = async(~a=34)
+let bar = async(~a)=>a+1

tests/parsing/grammar/expressions/expected/async.res.txt

@@ -25,4 +25,6 @@ let f =
   ((if isPositive
     then ((fun a -> fun b -> (a + b : int))[@res.async ])
     else (((fun c -> fun d -> (c - d : int)))[@res.async ]))
-  [@ns.ternary ])
+  [@ns.ternary ])
+let foo = async ~a:((34)[@ns.namedArgLoc ])
+let bar = ((fun ~a:((a)[@ns.namedArgLoc ]) -> a + 1)[@res.async ])

tests/printer/expr/asyncAwait.res

@@ -98,4 +98,7 @@ let f12 = @a (@b x) => 3
 let f13 = @a @b (~x) => 3
 
 let aw = (await (server->start))->foo
-let aw = (@foo (server->start))->foo
+let aw = (@foo (server->start))->foo
+
+let foo = async(~a=34)
+let bar = async(~a)=>a+1

tests/printer/expr/expected/asyncAwait.res.txt

@@ -121,3 +121,6 @@ let f13 = (@a @b ~x) => 3
 
 let aw = await (server->start)->foo
 let aw = @foo (server->start)->foo
+
+let foo = async(~a=34)
+let bar = async (~a) => a + 1