Use {} for empty record.

CHANGELOG.md

@@ -15,8 +15,11 @@
 - Add surface syntax for `async`/`await` https://github.com/rescript-lang/syntax/pull/600
 
 - Initial support for JSX V4, still work in progress.
+
   - :boom: when V4 is activated, at most one component is allowed for each module.
 
+- Add support for empty record literal `{}` for records with only optional fields, and type definition of empty record (e.g. `type empty = {}`)  https://github.com/rescript-lang/syntax/pull/632
+
 #### :bug: Bug Fix
 
 - Fix issue where the printer would omit attributes for `->` and `|>` https://github.com/rescript-lang/syntax/pull/629

src/res_core.ml

@@ -2691,13 +2691,9 @@ and parseBracedOrRecordExpr p =
   Parser.expect Lbrace p;
   match p.Parser.token with
   | Rbrace ->
-    Parser.err p (Diagnostics.unexpected Rbrace p.breadcrumbs);
     Parser.next p;
     let loc = mkLoc startPos p.prevEndPos in
-    let braces = makeBracesAttr loc in
-    Ast_helper.Exp.construct ~attrs:[braces] ~loc
-      (Location.mkloc (Longident.Lident "()") loc)
-      None
+    Ast_helper.Exp.record ~loc [] None
   | DotDotDot ->
     (* beginning of record spread, parse record *)
     Parser.next p;
@@ -4913,13 +4909,6 @@ and parseRecordOrObjectDecl p =
           :: parseCommaDelimitedRegion ~grammar:Grammar.FieldDeclarations
                ~closing:Rbrace ~f:parseFieldDeclarationRegion p
       in
-      let () =
-        match fields with
-        | [] ->
-          Parser.err ~startPos p
-            (Diagnostics.message "A record needs at least one field")
-        | _ -> ()
-      in
       Parser.expect Rbrace p;
       Parser.eatBreadcrumb p;
       (None, Asttypes.Public, Parsetree.Ptype_record fields))

tests/parsing/errors/expressions/expected/emptyBlock.res.txt

@@ -1,23 +1,2 @@
-
-  Syntax error!
-  tests/parsing/errors/expressions/emptyBlock.res:1:10
-
-  1 │ let x = {}
-  2 │ 
-  3 │ let f = (a, b) => {}
-
-  This let-binding misses an expression
-
-
-  Syntax error!
-  tests/parsing/errors/expressions/emptyBlock.res:3:20
-
-  1 │ let x = {}
-  2 │ 
-  3 │ let f = (a, b) => {}
-  4 │ 
-
-  Missing expression
-
-let x = ((())[@ns.braces ])
-let f a b = ((())[@ns.braces ])
+let x = {  }
+let f a b = {  }

tests/parsing/errors/typeDef/expected/emptyRecord.res.txt

@@ -1,11 +1,2 @@
-
-  Syntax error!
-  tests/parsing/errors/typeDef/emptyRecord.res:1:15-16
-
-  1 │ type record = {}
-  2 │ 
-
-  A record needs at least one field
-
 type nonrec record = {
   }

tests/parsing/recovery/expression/expected/emptyBlock.res.txt

@@ -1,23 +1,2 @@
-
-  Syntax error!
-  tests/parsing/recovery/expression/emptyBlock.res:1:10
-
-  1 │ let x = {}
-  2 │ 
-  3 │ let f = (a, b) => {}
-
-  This let-binding misses an expression
-
-
-  Syntax error!
-  tests/parsing/recovery/expression/emptyBlock.res:3:20
-
-  1 │ let x = {}
-  2 │ 
-  3 │ let f = (a, b) => {}
-  4 │ 
-
-  Missing expression
-
-let x = ((())[@ns.braces ])
-let f a b = ((())[@ns.braces ])
+let x = {  }
+let f a b = {  }