fn on_missing_expression_key(
tokens: &mut TokenSlice<'_, Token>,
token: &Token,
receiver: &mut dyn EventReceiver,
error: &mut dyn ErrorSink,
)fn on_missing_expression_key(
tokens: &mut TokenSlice<'_, Token>,
token: &Token,
receiver: &mut dyn EventReceiver,
error: &mut dyn ErrorSink,
)