Fix comment removed when function signature has type keyword

Author: shulhi

jscomp/syntax/src/res_comments_table.ml

@@ -1452,6 +1452,8 @@ and walk_expression expr t comments =
         attach t.leading expr.pexp_loc leading;
         walk_expression expr t inside;
         attach t.trailing expr.pexp_loc trailing
+    | Pexp_construct ({txt = Longident.Lident "Function$"}, Some return_expr) ->
+      walk_expression return_expr t comments
     | _ ->
       if is_block_expr return_expr then walk_expression return_expr t comments
       else

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

@@ -226,10 +226,10 @@ let f = (
   /* c6 */ ~x=?,
 ) => /* c7 */ ()
 
-let multiply = (type /* c-2 */ t /* c-1 */, m1 /* c1 */, /* c2 */ m2 /* c3 */) => ()
+let multiply = (type /* c-2 */ t /* c-1 */, /* c0 */ m1 /* c1 */, /* c2 */ m2 /* c3 */) => ()
 let multiply = (
   type /* c-4 */ t /* c-3 */,
-  m1 /* c1 */,
+  /* c0 */ m1 /* c1 */,
   type /* c-2 */ s /* c-1 */,
   /* c2 */ m2 /* c3 */,
 ) => ()