1 files changed, 3 insertions, 4 deletions

diff --git a/xtask/src/codegen/rust.ungram b/xtask/src/codegen/rust.ungram
index ba922af0d..28b50f021 100644
--- a/xtask/src/codegen/rust.ungram
+++ b/xtask/src/codegen/rust.ungram
@@ -83,22 +83,21 @@ StructDef =
   )
 
 RecordFieldList =
- '{' fields:RecordField* '}'
+ '{' fields:(RecordField (',' RecordField)* ','?)? '}'
 
 RecordField =
   Attr* Visibility? Name ':' ascribed_type:TypeRef
 
 TupleFieldList =
-  '(' fields:TupleField* ')'
+  '(' fields:(TupleField (',' TupleField)* ','?)? ')'
 
 TupleField =
-  Attr* Visibility? Name TypeRef
+  Attr* Visibility? TypeRef
 
 FieldList =
   RecordFieldList
 | TupleFieldList
 
-
 UnionDef =
   Attr* Visibility? 'union' Name GenericParamList? WhereClause?
   RecordFieldList