| //! # Feature gating |
| //! |
| //! This module implements the gating necessary for preventing certain compiler |
| //! features from being used by default. This module will crawl a pre-expanded |
| //! AST to ensure that there are no features which are used that are not |
| //! enabled. |
| //! |
| //! Features are enabled in programs via the crate-level attributes of |
| //! `#![feature(...)]` with a comma-separated list of features. |
| //! |
| //! For the purpose of future feature-tracking, once code for detection of feature |
| //! gate usage is added, *do not remove it again* even once the feature |
| //! becomes stable. |
| |
| mod accepted; |
| mod removed; |
| mod active; |
| mod builtin_attrs; |
| mod check; |
| |
| use std::fmt; |
| use crate::{edition::Edition, symbol::Symbol}; |
| use syntax_pos::Span; |
| |
| #[derive(Clone, Copy)] |
| pub enum State { |
| Accepted, |
| Active { set: fn(&mut Features, Span) }, |
| Removed { reason: Option<&'static str> }, |
| Stabilized { reason: Option<&'static str> }, |
| } |
| |
| impl fmt::Debug for State { |
| fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { |
| match self { |
| State::Accepted { .. } => write!(f, "accepted"), |
| State::Active { .. } => write!(f, "active"), |
| State::Removed { .. } => write!(f, "removed"), |
| State::Stabilized { .. } => write!(f, "stabilized"), |
| } |
| } |
| } |
| |
| #[derive(Debug, Clone)] |
| pub struct Feature { |
| state: State, |
| name: Symbol, |
| since: &'static str, |
| issue: Option<u32>, |
| edition: Option<Edition>, |
| description: &'static str, |
| } |
| |
| pub use active::{Features, INCOMPLETE_FEATURES}; |
| pub use builtin_attrs::{ |
| AttributeGate, AttributeType, GatedCfg, |
| BuiltinAttribute, BUILTIN_ATTRIBUTES, BUILTIN_ATTRIBUTE_MAP, |
| deprecated_attributes, is_builtin_attr, is_builtin_attr_name, |
| }; |
| pub use check::{ |
| check_attribute, check_crate, get_features, feature_err, emit_feature_err, |
| Stability, GateIssue, UnstableFeatures, |
| EXPLAIN_STMT_ATTR_SYNTAX, EXPLAIN_UNSIZED_TUPLE_COERCION, |
| }; |