2 files changed, 35 insertions, 30 deletions

diff --git a/xtask/src/codegen/gen_syntax.rs b/xtask/src/codegen/gen_syntax.rs
index c77fc8a8d..072527208 100644
--- a/xtask/src/codegen/gen_syntax.rs
+++ b/xtask/src/codegen/gen_syntax.rs
@@ -471,6 +471,7 @@ impl Field {
                     "::" => "coloncolon",
                     "#" => "pound",
                     "?" => "question_mark",
+                    "," => "comma",
                     _ => name,
                 };
                 format_ident!("{}_token", name)
@@ -599,13 +600,9 @@ fn lower_rule(acc: &mut Vec<Field>, grammar: &Grammar, rule: &Rule) {
     }
 }
 
-// (T (',' T)* ','?)?
+// (T (',' T)* ','?)
 fn lower_comma_list(acc: &mut Vec<Field>, grammar: &Grammar, rule: &Rule) -> bool {
     let rule = match rule {
-        Rule::Opt(it) => it,
-        _ => return false,
-    };
-    let rule = match &**rule {
         Rule::Seq(it) => it,
         _ => return false,
     };
diff --git a/xtask/src/codegen/rust.ungram b/xtask/src/codegen/rust.ungram
index 449b0242f..760a8dd95 100644
--- a/xtask/src/codegen/rust.ungram
+++ b/xtask/src/codegen/rust.ungram
@@ -8,14 +8,14 @@ Item =
 | EnumDef
 | ExternBlock
 | ExternCrate
-| FnDef
+| Fn
 | ImplDef
 | MacroCall
 | Module
 | StaticDef
 | StructDef
 | TraitDef
-| TypeAliasDef
+| TypeAlias
 | UnionDef
 | Use
 
@@ -42,15 +42,40 @@ UseTree =
 UseTreeList =
   '{' (UseTree (',' UseTree)* ','?)? '}'
 
-FnDef =
- Attr* Visibility? Abi? 'const' 'default' 'async' 'unsafe' 'fn' Name TypeParamList?
- ParamList RetType?
+Fn =
+ Attr* Visibility?
+ 'default'? ('async' | 'const')? 'unsafe'? Abi?
+ 'fn' Name TypeParamList? ParamList RetType?
  WhereClause?
  (body:BlockExpr | ';')
 
+Abi =
+  'extern' 'string'?
+
+ParamList =
+  '('(
+    (Param (',' Param)* ','?)?
+  | SelfParam ','?
+  | SelfParam ',' (Param (',' Param)* ','?)
+  )')'
+
+SelfParam =
+  Attr* (
+    ('&' 'lifetime'?)? 'mut'? 'self'
+  | 'mut'? 'self' ':' ascribed_type:TypeRef
+  )
+
+Param =
+  Attr* Pat (':' ascribed_type:TypeRef)
+| '...'
+
 RetType =
   '->' TypeRef
 
+TypeAlias =
+  Attr* Visibility? 'default'? 'type' Name TypeParamList? (':' TypeBoundList?)? WhereClause?
+  '=' TypeRef ';'
+
 StructDef =
   Attr* Visibility? 'struct' Name TypeParamList? (
     WhereClause?  (RecordFieldDefList | ';')
@@ -103,10 +128,6 @@ StaticDef =
   Attr* Visibility? 'static'? 'mut'? 'static' Name ':' ascribed_type:TypeRef
   '=' body:Expr ';'
 
-TypeAliasDef =
-  Attr* Visibility? 'default'? 'type' Name TypeParamList? WhereClause? (':' TypeBoundList?)?
-  '=' TypeRef ';'
-
 ImplDef =
  Attr* Visibility? 'const'? 'default'? 'unsafe'? 'impl' TypeParamList? '!'? 'for'
  WhereClause?
@@ -388,9 +409,6 @@ WherePred =
 WhereClause =
   'where' predicates:WherePred*
 
-Abi =
-  'string'
-
 ExprStmt =
   Attr* Expr ';'
 
@@ -398,16 +416,6 @@ LetStmt =
   Attr* 'let' Pat (':' ascribed_type:TypeRef)
   '=' initializer:Expr ';'
 
-ParamList =
-  '(' SelfParam Param* ')'
-
-SelfParam =
-  Attr* ('&' 'lifetime'?)? 'mut'? 'self' (':' ascribed_type:TypeRef)
-
-Param =
-  Attr* Pat (':' ascribed_type:TypeRef)
-| '...'
-
 Path =
   (qualifier:Path '::')? segment:PathSegment
 
@@ -465,13 +473,13 @@ TypeRef =
 | DynTraitType
 
 AssocItem =
-  FnDef
-| TypeAliasDef
+  Fn
+| TypeAlias
 | ConstDef
 | MacroCall
 
 ExternItem =
-  FnDef | StaticDef
+  Fn | StaticDef
 
 AttrInput =
   Literal