Fix formatter eats comments on the first argument of a uncurried function (#6763)

Print comments inside uncurried arrow function types correctly.

Author: shulhi

jscomp/syntax/src/res_comments_table.ml

@@ -1799,6 +1799,9 @@ and walkCoreType typ t comments =
     attach t.trailing typexpr.ptyp_loc afterTyp
   | Ptyp_variant (rowFields, _, _) ->
     walkList (rowFields |> List.map (fun rf -> RowField rf)) t comments
+  | Ptyp_constr
+      ({txt = Lident "function$"}, [({ptyp_desc = Ptyp_arrow _} as desc); _]) ->
+    walkCoreType desc t comments
   | Ptyp_constr (longident, typexprs) ->
     let beforeLongident, _afterLongident =
       partitionLeadingTrailing comments longident.loc

jscomp/syntax/tests/printer/comments/expected/typexpr.res.txt

@@ -79,3 +79,17 @@ type jsUser = /* before */ {
   // above age
   /* before age */ "age" /* after age */: /* before int */ int /* after int */,
 } /* after */
+
+external test: (
+  // comment 1
+  ~int: int,
+  // comment 2
+  ~int: int,
+) => unit = "test"
+
+external another_test: (
+  // comment 1
+  int,
+  // comment 2
+  int,
+) => unit = "test"

jscomp/syntax/tests/printer/comments/typexpr.res

@@ -64,3 +64,17 @@ type jsUser = /* before */ {
   // above age
   /* before age */"age" /* after age */: /*before int */ int /*after int */
 } /* after */
+
+external test: (
+  // comment 1
+  ~int: int,
+  // comment 2
+  ~int: int,
+) => unit = "test"
+
+external another_test: (
+  // comment 1
+  int,
+  // comment 2
+  int,
+) => unit = "test"