syntax_data: {"ast_node_type":"other","tokens":[{"end":66,"kind":"keyword","start":0,"text":"//"}]}
source_snippet:     // First disallow some configuration given on the command line
context_before: pub fn build_configuration(sess: &Session, mut user_cfg: Cfg) -> Cfg {
context_after:     cfg::disallow_cfgs(sess, &user_cfg);