trailing commas

specs.md

@@ -92,7 +92,7 @@ GLSL;
 | `:`    | type annotation                      |
 | `=`    | assignment (in typed var decl)       |
 | `;`    | statement terminator                 |
-| `,`    | separator                            |
+| `,`    | separator (trailing commas allowed)   |
 | `.`    | field access / enum literal prefix   |
 | `->`   | return type annotation               |
 | `=>`   | lambda arrow                         |
@@ -244,6 +244,14 @@ v3 := Vec4.{ w=0, x=2, y=3, z=4 };
 z := 5.0;
 w := 6.0;
 v4 := Vec4.{ y=3, x=9, w, z };
+
+// Trailing commas are allowed in all comma-separated lists
+v5 := Vec4.{
+    x = 1.0,
+    y = 2.0,
+    z = 3.0,
+    w = 4.0,
+};
 ```
 
 #### Field Access and Assignment
@@ -1779,7 +1787,7 @@ enum_decl       = IDENT '::' 'enum' '{' (IDENT ';')* '}'
 struct_decl     = IDENT '::' 'struct' '{' struct_member* '}'
 struct_member   = field_group | '#using' IDENT ';'
 field_group     = IDENT (',' IDENT)* ':' type ('=' expr)? ';'
-params          = param (',' param)*
+params          = param (',' param)* ','?
 param           = IDENT ':' type
 block           = '{' stmt* '}'
 stmt            = decl | assignment ';' | multi_assign ';' | return_stmt | defer_stmt | insert_stmt
@@ -1803,7 +1811,7 @@ postfix         = primary ('(' args? ')' | '.' IDENT | '.{' field_init_list '}')
 primary         = INT | HEX_INT | BIN_INT | FLOAT | STRING | BOOL | IDENT | '---'
                 | '.' IDENT | '.' '{' field_init_list '}'
                 | '(' expr ')' | block | '#run' expr
-field_init_list = field_init (',' field_init)*
+field_init_list = field_init (',' field_init)* ','?
 field_init      = IDENT '=' expr | IDENT | expr
 if_expr         = 'if' expr 'then' expr ('else' expr)?
                 | 'if' expr block ('else' block)?
@@ -1812,7 +1820,7 @@ case_arm        = 'case' pattern ':' (stmt* | 'break' ';')
 else_arm        = 'else' ':' stmt*
 pattern         = '.' IDENT | INT | BOOL | IDENT
 lambda          = '(' params? ')' ('->' type)? '=>' expr
-args            = expr (',' expr)*
+args            = expr (',' expr)* ','?
 type            = '$' IDENT | 's32' | 'f32' | 'f64' | 'bool' | 'string'
                 | 'Any' | 'Type' | '..' type | '[' expr ']' type | IDENT
 ```