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Remove rustc_feature::State.

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`State` is used to distinguish active vs accepted vs removed features.
However, these can also be distinguished by their location, in
`ACTIVE_FEATURES`, `ACCEPTED_FEATURES`, and `REMOVED_FEATURES`.

So this commit removes `State` and moves the internals of its variants
next to the `Feature` in each element of `*_FEATURES`, introducing new
types `ActiveFeature` and `RemovedFeature`. (There is no need for
`AcceptedFeature` because `State::Accepted` had no fields.)

This is a tighter type representation, avoids the need for some runtime
checks, and makes the code a bit shorter.
This commit is contained in:
Nicholas Nethercote 2023-10-05 18:59:01 +11:00
parent 64368d0279
commit 41b6899487
5 changed files with 61 additions and 97 deletions
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48
compiler/rustc_expand/src/config.rs
View File

@ -14,12 +14,12 @@ use rustc_ast::{self as ast, AttrStyle, Attribute, HasAttrs, HasTokens, MetaItem
use rustc_attr as attr;
use rustc_data_structures::flat_map_in_place::FlatMapInPlace;
use rustc_data_structures::fx::FxHashSet;
use rustc_feature::{Feature, Features, State as FeatureState};
use rustc_feature::Features;
use rustc_feature::{ACCEPTED_FEATURES, ACTIVE_FEATURES, REMOVED_FEATURES};
use rustc_parse::validate_attr;
use rustc_session::parse::feature_err;
use rustc_session::Session;
use rustc_span::edition::{Edition, ALL_EDITIONS};
use rustc_span::edition::ALL_EDITIONS;
use rustc_span::symbol::{sym, Symbol};
use rustc_span::Span;
use thin_vec::ThinVec;
@ -36,16 +36,6 @@ pub struct StripUnconfigured<'a> {
}
pub fn features(sess: &Session, krate_attrs: &[Attribute]) -> Features {
fn active_features_up_to(edition: Edition) -> impl Iterator<Item = &'static Feature> {
ACTIVE_FEATURES.iter().filter(move |feature| {
if let Some(feature_edition) = feature.edition {
feature_edition <= edition
} else {
false
}
})
}
fn feature_list(attr: &Attribute) -> ThinVec<ast::NestedMetaItem> {
if attr.has_name(sym::feature)
&& let Some(list) = attr.meta_item_list()
@ -83,11 +73,13 @@ 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 feature in active_features_up_to(features_edition) {
// FIXME(Manishearth) there is currently no way to set lib features by
// edition.
edition_enabled_features.insert(feature.name);
feature.set(&mut features);
for f in ACTIVE_FEATURES {
if let Some(edition) = f.feature.edition && edition <= features_edition {
// FIXME(Manishearth) there is currently no way to set lib features by
// edition.
edition_enabled_features.insert(f.feature.name);
(f.set_enabled)(&mut features);
}
}
// Process all features declared in the code.
@ -147,19 +139,17 @@ pub fn features(sess: &Session, krate_attrs: &[Attribute]) -> Features {
}
// If the declared feature has been removed, issue an error.
if let Some(Feature { state, .. }) = REMOVED_FEATURES.iter().find(|f| name == f.name) {
if let FeatureState::Removed { reason } = state {
sess.emit_err(FeatureRemoved {
span: mi.span(),
reason: reason.map(|reason| FeatureRemovedReason { reason }),
});
continue;
}
if let Some(f) = REMOVED_FEATURES.iter().find(|f| name == f.feature.name) {
sess.emit_err(FeatureRemoved {
span: mi.span(),
reason: f.reason.map(|reason| FeatureRemovedReason { reason }),
});
continue;
}
// If the declared feature is stable, record it.
if let Some(Feature { since, .. }) = ACCEPTED_FEATURES.iter().find(|f| name == f.name) {
let since = Some(Symbol::intern(since));
if let Some(f) = ACCEPTED_FEATURES.iter().find(|f| name == f.name) {
let since = Some(Symbol::intern(f.since));
features.set_declared_lang_feature(name, mi.span(), since);
continue;
}
@ -175,8 +165,8 @@ 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.name) {
f.set(&mut features);
if let Some(f) = ACTIVE_FEATURES.iter().find(|f| name == f.feature.name) {
(f.set_enabled)(&mut features);
features.set_declared_lang_feature(name, mi.span(), None);
continue;
}

17
compiler/rustc_feature/src/accepted.rs
View File

@ -1,6 +1,6 @@
//! List of the accepted feature gates.
use super::{to_nonzero, Feature, State};
use super::{to_nonzero, Feature};
use rustc_span::symbol::sym;
macro_rules! declare_features {
@ -9,15 +9,12 @@ macro_rules! declare_features {
)+) => {
/// Those language feature has since been Accepted (it was once Active)
pub const ACCEPTED_FEATURES: &[Feature] = &[
$(
Feature {
state: State::Accepted,
name: sym::$feature,
since: $ver,
issue: to_nonzero($issue),
edition: None,
}
),+
$(Feature {
name: sym::$feature,
since: $ver,
issue: to_nonzero($issue),
edition: None,
}),+
];
}
}

36
compiler/rustc_feature/src/active.rs
View File

@ -1,12 +1,17 @@
//! List of the active feature gates.
use super::{to_nonzero, Feature, State};
use super::{to_nonzero, Feature};
use rustc_data_structures::fx::FxHashSet;
use rustc_span::edition::Edition;
use rustc_span::symbol::{sym, Symbol};
use rustc_span::Span;
pub struct ActiveFeature {
pub feature: Feature,
pub set_enabled: fn(&mut Features),
}
#[derive(PartialEq)]
enum FeatureStatus {
Default,
@ -32,21 +37,18 @@ macro_rules! declare_features {
)+) => {
/// Represents active features that are currently being implemented or
/// currently being considered for addition/removal.
pub const ACTIVE_FEATURES:
&[Feature] =
&[$(
// (sym::$feature, $ver, $issue, $edition, set!($feature))
Feature {
state: State::Active {
// Sets this feature's corresponding bool within `features`.
set: |features| features.$feature = true,
},
pub const ACTIVE_FEATURES: &[ActiveFeature] = &[
$(ActiveFeature {
feature: Feature {
name: sym::$feature,
since: $ver,
issue: to_nonzero($issue),
edition: $edition,
}
),+];
},
// Sets this feature's corresponding bool within `features`.
set_enabled: |features| features.$feature = true,
}),+
];
/// A set of features to be used by later passes.
#[derive(Clone, Default, Debug)]
@ -134,16 +136,6 @@ macro_rules! declare_features {
};
}
impl Feature {
/// Sets this feature in `Features`. Panics if called on a non-active feature.
pub fn set(&self, features: &mut Features) {
match self.state {
State::Active { set } => set(features),
_ => panic!("called `set` on feature `{}` which is not `active`", self.name),
}
}
}
// See https://rustc-dev-guide.rust-lang.org/feature-gates.html#feature-gates for more
// documentation about handling feature gates.
//

38
compiler/rustc_feature/src/lib.rs
View File

@ -24,29 +24,10 @@ mod removed;
mod tests;
use rustc_span::{edition::Edition, symbol::Symbol};
use std::fmt;
use std::num::NonZeroU32;
#[derive(Clone, Copy)]
pub enum State {
Accepted,
Active { set: fn(&mut Features) },
Removed { 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"),
}
}
}
#[derive(Debug, Clone)]
pub struct Feature {
pub state: State,
pub name: Symbol,
pub since: &'static str,
issue: Option<NonZeroU32>,
@ -106,17 +87,16 @@ impl UnstableFeatures {
fn find_lang_feature_issue(feature: Symbol) -> Option<NonZeroU32> {
// Search in all the feature lists.
let found = []
.iter()
.chain(ACTIVE_FEATURES)
.chain(ACCEPTED_FEATURES)
.chain(REMOVED_FEATURES)
.find(|t| t.name == feature);
match found {
Some(found) => found.issue,
None => panic!("feature `{feature}` is not declared anywhere"),
if let Some(f) = ACTIVE_FEATURES.iter().find(|f| f.feature.name == feature) {
return f.feature.issue;
}
if let Some(f) = ACCEPTED_FEATURES.iter().find(|f| f.name == feature) {
return f.issue;
}
if let Some(f) = REMOVED_FEATURES.iter().find(|f| f.feature.name == feature) {
return f.feature.issue;
}
panic!("feature `{feature}` is not declared anywhere");
}
const fn to_nonzero(n: Option<u32>) -> Option<NonZeroU32> {

19
compiler/rustc_feature/src/removed.rs
View File

@ -1,23 +1,28 @@
//! List of the removed feature gates.
use super::{to_nonzero, Feature, State};
use super::{to_nonzero, Feature};
use rustc_span::symbol::sym;
pub struct RemovedFeature {
pub feature: Feature,
pub reason: Option<&'static str>,
}
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)
pub const REMOVED_FEATURES: &[Feature] = &[
$(
Feature {
state: State::Removed { reason: $reason },
pub const REMOVED_FEATURES: &[RemovedFeature] = &[
$(RemovedFeature {
feature: Feature {
name: sym::$feature,
since: $ver,
issue: to_nonzero($issue),
edition: None,
}
),+
},
reason: $reason
}),+
];
};
}