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Auto merge of #53444 - varkor:lib_features-conditional, r=michaelwoerister

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Only fetch lib_features when there are unknown feature attributes

An attempt to win back some of the performance lost in https://github.com/rust-lang/rust/pull/52644#issuecomment-413761127.

cc @nnethercote
This commit is contained in:
bors 2018-08-21 18:16:43 +00:00
commit 2d6d3acf4f
2 changed files with 27 additions and 12 deletions
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7
src/librustc/middle/lib_features.rs
View File

@ -17,7 +17,7 @@
use ty::TyCtxt;
use syntax::symbol::Symbol;
use syntax::ast::{Attribute, MetaItem, MetaItemKind};
use syntax_pos::{Span, DUMMY_SP};
use syntax_pos::Span;
use hir::intravisit::{self, NestedVisitorMap, Visitor};
use rustc_data_structures::fx::{FxHashSet, FxHashMap};
use errors::DiagnosticId;
@ -152,11 +152,6 @@ fn visit_attribute(&mut self, attr: &'tcx Attribute) {
pub fn collect<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>) -> LibFeatures {
let mut collector = LibFeatureCollector::new(tcx);
for &cnum in tcx.crates().iter() {
for &(feature, since) in tcx.defined_lib_features(cnum).iter() {
collector.collect_feature(feature, since, DUMMY_SP);
}
}
intravisit::walk_crate(&mut collector, tcx.hir.krate());
collector.lib_features
}

32
src/librustc/middle/stability.rs
View File

@ -846,14 +846,34 @@ pub fn check_unused_or_stable_features<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>) {
remaining_lib_features.remove(&Symbol::intern("libc"));
remaining_lib_features.remove(&Symbol::intern("test"));
for (feature, stable) in tcx.lib_features().to_vec() {
if let Some(since) = stable {
if let Some(span) = remaining_lib_features.get(&feature) {
// Warn if the user has enabled an already-stable lib feature.
unnecessary_stable_feature_lint(tcx, *span, feature, since);
let check_features =
|remaining_lib_features: &mut FxHashMap<_, _>, defined_features: &Vec<_>| {
for &(feature, since) in defined_features {
if let Some(since) = since {
if let Some(span) = remaining_lib_features.get(&feature) {
// Warn if the user has enabled an already-stable lib feature.
unnecessary_stable_feature_lint(tcx, *span, feature, since);
}
}
remaining_lib_features.remove(&feature);
if remaining_lib_features.is_empty() {
break;
}
}
};
// We always collect the lib features declared in the current crate, even if there are
// no unknown features, because the collection also does feature attribute validation.
let local_defined_features = tcx.lib_features().to_vec();
if !remaining_lib_features.is_empty() {
check_features(&mut remaining_lib_features, &local_defined_features);
for &cnum in &*tcx.crates() {
if remaining_lib_features.is_empty() {
break;
}
check_features(&mut remaining_lib_features, &tcx.defined_lib_features(cnum));
}
remaining_lib_features.remove(&feature);
}
for (feature, span) in remaining_lib_features {