From 49062100c609daa8404b96fbd57dcd9a415c7c19 Mon Sep 17 00:00:00 2001
From: Cristiano Calcagno <cristianoc@users.noreply.github.com>
Date: Fri, 28 Oct 2022 06:22:17 +0200
Subject: [PATCH 1/2] Fix issue where async as an id cannot be used with
 application and labelled arguments.

Fixes https://github.com/rescript-lang/syntax/issues/707
---
 CHANGELOG.md                                   |  2 ++
 src/res_core.ml                                | 12 ++++++++----
 tests/printer/expr/asyncAwait.res              |  5 ++++-
 tests/printer/expr/expected/asyncAwait.res.txt |  3 +++
 4 files changed, 17 insertions(+), 5 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 1b6984cf..6bddeab2 100644
--- a/CHANGELOG.md
+++ b/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
 
diff --git a/src/res_core.ml b/src/res_core.ml
index b38430df..d535487d 100644
--- a/src/res_core.ml
+++ b/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 *)
diff --git a/tests/printer/expr/asyncAwait.res b/tests/printer/expr/asyncAwait.res
index 765e6597..efabc856 100644
--- a/tests/printer/expr/asyncAwait.res
+++ b/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
\ No newline at end of file
+let aw = (@foo (server->start))->foo
+
+let foo = async(~a=34)
+let bar = async(~a)=>a+1
\ No newline at end of file
diff --git a/tests/printer/expr/expected/asyncAwait.res.txt b/tests/printer/expr/expected/asyncAwait.res.txt
index bfd223bc..1082a3d8 100644
--- a/tests/printer/expr/expected/asyncAwait.res.txt
+++ b/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

From dd421339658da20c68074254492e514086984513 Mon Sep 17 00:00:00 2001
From: Cristiano Calcagno <cristianoc@users.noreply.github.com>
Date: Fri, 28 Oct 2022 08:31:30 +0200
Subject: [PATCH 2/2] Add parsing test.

---
 tests/parsing/grammar/expressions/async.res              | 5 ++++-
 tests/parsing/grammar/expressions/expected/async.res.txt | 4 +++-
 2 files changed, 7 insertions(+), 2 deletions(-)

diff --git a/tests/parsing/grammar/expressions/async.res b/tests/parsing/grammar/expressions/async.res
index b104866d..9f33ef2d 100644
--- a/tests/parsing/grammar/expressions/async.res
+++ b/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
\ No newline at end of file
+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
\ No newline at end of file
diff --git a/tests/parsing/grammar/expressions/expected/async.res.txt b/tests/parsing/grammar/expressions/expected/async.res.txt
index 7aef8ffd..eb4424d9 100644
--- a/tests/parsing/grammar/expressions/expected/async.res.txt
+++ b/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 ])
\ No newline at end of file
+  [@ns.ternary ])
+let foo = async ~a:((34)[@ns.namedArgLoc ])
+let bar = ((fun ~a:((a)[@ns.namedArgLoc ]) -> a + 1)[@res.async ])
\ No newline at end of file