Rename ACTIVE_FEATURES as UNSTABLE_FEATURES.

It's a better name, and lets "active features" refer to the features
that are active in a particular program, due to being declared or
enabled by the edition.

The commit also renames `Features::enabled` as `Features::active` to
match this; I changed my mind and have decided that "active" is a little
better thatn "enabled" for this, particularly because a number of
pre-existing comments use "active" in this way.

Finally, the commit renames `Status::Stable` as `Status::Accepted`, to
match `ACCEPTED_FEATURES`.

compiler/rustc_ast_passes/src/feature_gate.rs

@@ -658,7 +658,7 @@ fn check_incompatible_features(sess: &Session, features: &Features) {
 
     for (f1, f2) in rustc_feature::INCOMPATIBLE_FEATURES
         .iter()
-        .filter(|&&(f1, f2)| features.enabled(f1) && features.enabled(f2))
+        .filter(|&&(f1, f2)| features.active(f1) && features.active(f2))
     {
         if let Some((f1_name, f1_span)) = declared_features.clone().find(|(name, _)| name == f1) {
             if let Some((f2_name, f2_span)) = declared_features.clone().find(|(name, _)| name == f2)

compiler/rustc_const_eval/src/transform/check_consts/check.rs

@@ -323,7 +323,7 @@ impl<'mir, 'tcx> Checker<'mir, 'tcx> {
         let gate = match op.status_in_item(self.ccx) {
             Status::Allowed => return,
 
-            Status::Unstable(gate) if self.tcx.features().enabled(gate) => {
+            Status::Unstable(gate) if self.tcx.features().active(gate) => {
                 let unstable_in_stable = self.ccx.is_const_stable_const_fn()
                     && !super::rustc_allow_const_fn_unstable(self.tcx, self.def_id(), gate);
                 if unstable_in_stable {

compiler/rustc_expand/src/config.rs

@@ -15,7 +15,7 @@ use rustc_attr as attr;
 use rustc_data_structures::flat_map_in_place::FlatMapInPlace;
 use rustc_data_structures::fx::FxHashSet;
 use rustc_feature::Features;
-use rustc_feature::{ACCEPTED_FEATURES, ACTIVE_FEATURES, REMOVED_FEATURES};
+use rustc_feature::{ACCEPTED_FEATURES, REMOVED_FEATURES, UNSTABLE_FEATURES};
 use rustc_parse::validate_attr;
 use rustc_session::parse::feature_err;
 use rustc_session::Session;
@@ -73,7 +73,7 @@ pub fn features(sess: &Session, krate_attrs: &[Attribute]) -> Features {
     // Enable edition-dependent features based on `features_edition`.
     // - E.g. enable `test_2018_feature` if `features_edition` is 2018 or higher
     let mut edition_enabled_features = FxHashSet::default();
-    for f in ACTIVE_FEATURES {
+    for f in UNSTABLE_FEATURES {
         if let Some(edition) = f.feature.edition && edition <= features_edition {
             // FIXME(Manishearth) there is currently no way to set lib features by
             // edition.
@@ -165,7 +165,7 @@ pub fn features(sess: &Session, krate_attrs: &[Attribute]) -> Features {
             }
 
             // If the declared feature is unstable, record it.
-            if let Some(f) = ACTIVE_FEATURES.iter().find(|f| name == f.feature.name) {
+            if let Some(f) = UNSTABLE_FEATURES.iter().find(|f| name == f.feature.name) {
                 (f.set_enabled)(&mut features);
                 features.set_declared_lang_feature(name, mi.span(), None);
                 continue;

compiler/rustc_feature/src/accepted.rs

@@ -7,7 +7,7 @@ macro_rules! declare_features {
     ($(
         $(#[doc = $doc:tt])* (accepted, $feature:ident, $ver:expr, $issue:expr, None),
     )+) => {
-        /// Those language feature has since been Accepted (it was once Active)
+        /// Formerly unstable features that have now been accepted (stabilized).
         pub const ACCEPTED_FEATURES: &[Feature] = &[
             $(Feature {
                 name: sym::$feature,

compiler/rustc_feature/src/lib.rs

@@ -16,9 +16,9 @@
 #![deny(rustc::diagnostic_outside_of_impl)]
 
 mod accepted;
-mod active;
 mod builtin_attrs;
 mod removed;
+mod unstable;
 
 #[cfg(test)]
 mod tests;
@@ -44,9 +44,9 @@ pub enum Stability {
 
 #[derive(Clone, Copy, Debug, Hash)]
 pub enum UnstableFeatures {
-    /// Hard errors for unstable features are active, as on beta/stable channels.
+    /// Disallow use of unstable features, as on beta/stable channels.
     Disallow,
-    /// Allow features to be activated, as on nightly.
+    /// Allow use of unstable features, as on nightly.
     Allow,
     /// Errors are bypassed for bootstrapping. This is required any time
     /// during the build that feature-related lints are set to warn or above
@@ -87,7 +87,7 @@ impl UnstableFeatures {
 
 fn find_lang_feature_issue(feature: Symbol) -> Option<NonZeroU32> {
     // Search in all the feature lists.
-    if let Some(f) = ACTIVE_FEATURES.iter().find(|f| f.feature.name == feature) {
+    if let Some(f) = UNSTABLE_FEATURES.iter().find(|f| f.feature.name == feature) {
         return f.feature.issue;
     }
     if let Some(f) = ACCEPTED_FEATURES.iter().find(|f| f.name == feature) {
@@ -121,11 +121,11 @@ pub fn find_feature_issue(feature: Symbol, issue: GateIssue) -> Option<NonZeroU3
 }
 
 pub use accepted::ACCEPTED_FEATURES;
-pub use active::{Features, ACTIVE_FEATURES, INCOMPATIBLE_FEATURES};
 pub use builtin_attrs::AttributeDuplicates;
 pub use builtin_attrs::{
     deprecated_attributes, find_gated_cfg, is_builtin_attr_name, is_builtin_only_local,
     is_valid_for_get_attr, AttributeGate, AttributeTemplate, AttributeType, BuiltinAttribute,
     GatedCfg, BUILTIN_ATTRIBUTES, BUILTIN_ATTRIBUTE_MAP,
 };
 pub use removed::REMOVED_FEATURES;
+pub use unstable::{Features, INCOMPATIBLE_FEATURES, UNSTABLE_FEATURES};

compiler/rustc_feature/src/removed.rs

@@ -12,7 +12,7 @@ macro_rules! declare_features {
     ($(
         $(#[doc = $doc:tt])* (removed, $feature:ident, $ver:expr, $issue:expr, None, $reason:expr),
     )+) => {
-        /// Represents unstable features which have since been removed (it was once Active)
+        /// Formerly unstable features that have now been removed.
         pub const REMOVED_FEATURES: &[RemovedFeature] = &[
             $(RemovedFeature {
                 feature: Feature {