Special-case the one-element record

Author: cknitt

src/res_printer.ml

@@ -2807,19 +2807,19 @@ and printExpression (e : Parsetree.expression) cmtTbl =
     let forceBreak =
       e.pexp_loc.loc_start.pos_lnum < e.pexp_loc.loc_end.pos_lnum
     in
-    let punningAllowed = match spreadExpr, rows with
-    | (None, [_]) -> false (* disallow punning for single-element records *)
-    | _ -> true
-    in
     Doc.breakableGroup ~forceBreak (
       Doc.concat([
         Doc.lbrace;
         Doc.indent (
           Doc.concat [
             Doc.softLine;
-            spread;
-            Doc.join ~sep:(Doc.concat [Doc.text ","; Doc.line])
-              (List.map (fun row -> printRecordRow row cmtTbl punningAllowed) rows)
+            match spreadExpr, rows with
+            | (None, [row]) -> printRecordRowNoPunning row cmtTbl
+            | _ -> Doc.concat [
+              spread;
+              Doc.join ~sep:(Doc.concat [Doc.text ","; Doc.line])
+                (List.map (fun row -> printRecordRow row cmtTbl) rows)
+            ]
           ]
         );
         Doc.trailingComma;
@@ -4822,19 +4822,15 @@ and printDirectionFlag flag = match flag with
   | Asttypes.Downto -> Doc.text " downto "
   | Asttypes.Upto -> Doc.text " to "
 
-and printRecordRow (lbl, expr) cmtTbl punningAllowed =
+and printRecordRowPunned (lbl, expr) cmtTbl =
+  let cmtLoc = {lbl.Asttypes.loc with loc_end = expr.Parsetree.pexp_loc.loc_end} in
+  let doc = Doc.group (printLidentPath lbl cmtTbl) in
+  printComments doc cmtTbl cmtLoc
+
+and printRecordRowNoPunning (lbl, expr) cmtTbl =
   let cmtLoc = {lbl.loc with loc_end = expr.pexp_loc.loc_end} in
   let doc = Doc.group (
-    match expr.pexp_desc with
-    | Pexp_ident({txt = Lident key; loc = keyLoc}) when (
-      punningAllowed && 
-      Longident.last lbl.txt = key &&
-      lbl.loc.loc_start.pos_cnum == keyLoc.loc_start.pos_cnum
-    ) ->
-      (* print punned field *)
-      printLidentPath lbl cmtTbl;
-    | _ ->
-      Doc.concat [
+    Doc.concat [
       printLidentPath lbl cmtTbl;
       Doc.text ": ";
       (let doc = printExpressionWithComments expr cmtTbl in
@@ -4846,6 +4842,14 @@ and printRecordRow (lbl, expr) cmtTbl punningAllowed =
   ) in
   printComments doc cmtTbl cmtLoc
 
+and printRecordRow (lbl, expr) cmtTbl =
+  match expr.pexp_desc with
+  | Pexp_ident({txt = Lident key; loc = keyLoc}) when (
+    Longident.last lbl.txt = key &&
+    lbl.loc.loc_start.pos_cnum == keyLoc.loc_start.pos_cnum
+  ) -> printRecordRowPunned (lbl, expr) cmtTbl;
+  | _ -> printRecordRowNoPunning (lbl, expr) cmtTbl
+
 and printBsObjectRow (lbl, expr) cmtTbl =
   let cmtLoc = {lbl.loc with loc_end = expr.pexp_loc.loc_end} in
   let lblDoc =