Merge pull request rescript-lang#4715 from rescript-lang/upgrade_syntax

update syntax, prepare to cut the release 8.3

Author: bobzhang

lib/4.06.1/whole_compiler.ml

@@ -417262,6 +417262,7 @@ let log t =
     ]
   ) |> Doc.toString ~width:80 |> print_endline
   [@@live]
+
 let attach tbl loc comments =
   match comments with
   | [] -> ()
@@ -417953,6 +417954,12 @@ let rec walkStructure s t comments =
         partitionLeadingTrailing comments longident.loc in
       attach t.leading longident.loc leading;
       attach t.trailing longident.loc trailing;
+    | Pexp_let (
+        _recFlag,
+        valueBindings,
+        {pexp_desc = Pexp_construct ({txt = Longident.Lident "()"}, None)}
+      ) ->
+      walkValueBindings valueBindings t comments
     | Pexp_let (_recFlag, valueBindings, expr2) ->
       let comments = visitListButContinueWithRemainingComments
         ~getLoc:(fun n ->
@@ -421778,7 +421785,7 @@ let printMultilineCommentContent txt =
       Doc.text "*/";
     ]
 
-let printTrailingComment (nodeLoc : Location.t) comment =
+let printTrailingComment (prevLoc: Location.t) (nodeLoc : Location.t) comment =
   let singleLine = Comment.isSingleLineComment comment in
   let content =
     let txt = Comment.txt comment in
@@ -421789,8 +421796,7 @@ let printTrailingComment (nodeLoc : Location.t) comment =
   in
   let diff =
     let cmtStart = (Comment.loc comment).loc_start in
-    let prevTokEndPos = Comment.prevTokEndPos comment in
-    cmtStart.pos_lnum - prevTokEndPos.pos_lnum
+    cmtStart.pos_lnum - prevLoc.loc_end.pos_lnum
   in
   let isBelow =
     (Comment.loc comment).loc_start.pos_lnum > nodeLoc.loc_end.pos_lnum in
@@ -421912,12 +421918,12 @@ let printLeadingComments node tbl loc =
     loop [] comments
 
 let printTrailingComments node tbl loc =
-  let rec loop acc comments =
+  let rec loop prev acc comments =
     match comments with
     | [] -> Doc.concat (List.rev acc)
     | comment::comments ->
-      let cmtDoc = printTrailingComment loc comment in
-      loop (cmtDoc::acc) comments
+      let cmtDoc = printTrailingComment prev loc comment in
+      loop (Comment.loc comment) (cmtDoc::acc) comments
   in
   match Hashtbl.find tbl loc with
   | exception Not_found -> node
@@ -421926,7 +421932,7 @@ let printTrailingComments node tbl loc =
    (* Remove comments from tbl: Some ast nodes have the same location.
     * We only want to print comments once *)
     Hashtbl.remove tbl loc;
-    let cmtsDoc = loop [] comments in
+    let cmtsDoc = loop loc [] comments in
     Doc.concat [
       node;
       cmtsDoc;