Macro rustc_ast_passes::feature_gate::gate_feature_fn

macro_rules! gate_feature_fn {
    ($visitor: expr, $has_feature: expr, $span: expr, $name: expr, $explain: expr, $help: expr) => { ... };
    ($visitor: expr, $has_feature: expr, $span: expr, $name: expr, $explain: expr) => { ... };
    (future_incompatible; $visitor: expr, $has_feature: expr, $span: expr, $name: expr, $explain: expr) => { ... };
}