3 files changed, 5 insertions, 41 deletions
diff --git a/src/libsyntax/feature_gate/check.rs b/src/libsyntax/feature_gate/check.rs
index c53f5f41e32..141b324baa8 100644
--- a/src/libsyntax/feature_gate/check.rs
+++ b/src/libsyntax/feature_gate/check.rs
@@ -1,6 +1,6 @@
-use rustc_feature::{ACCEPTED_FEATURES, ACTIVE_FEATURES, Features, Feature, State as FeatureState};
-use rustc_feature::{REMOVED_FEATURES, STABLE_REMOVED_FEATURES};
+use rustc_feature::{ACCEPTED_FEATURES, ACTIVE_FEATURES, REMOVED_FEATURES, STABLE_REMOVED_FEATURES};
 use rustc_feature::{AttributeGate, BUILTIN_ATTRIBUTE_MAP};
+use rustc_feature::{Features, Feature, State as FeatureState, UnstableFeatures};
 
 use crate::ast::{self, AssocTyConstraint, AssocTyConstraintKind, NodeId};
 use crate::ast::{GenericParam, GenericParamKind, PatKind, RangeEnd, VariantData};
@@ -18,8 +18,6 @@ use log::debug;
 
 use rustc_error_codes::*;
 
-
-use std::env;
 use std::num::NonZeroU32;
 
 macro_rules! gate_feature_fn {
@@ -880,40 +878,6 @@ pub fn check_crate(krate: &ast::Crate,
     visit::walk_crate(&mut visitor, krate);
 }
 
-#[derive(Clone, Copy, Hash)]
-pub enum UnstableFeatures {
-    /// Hard errors for unstable features are active, as on beta/stable channels.
-    Disallow,
-    /// Allow features to be activated, 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
-    /// because the build turns on warnings-as-errors and uses lots of unstable
-    /// features. As a result, this is always required for building Rust itself.
-    Cheat
-}
-
-impl UnstableFeatures {
-    pub fn from_environment() -> UnstableFeatures {
-        // `true` if this is a feature-staged build, i.e., on the beta or stable channel.
-        let disable_unstable_features = option_env!("CFG_DISABLE_UNSTABLE_FEATURES").is_some();
-        // `true` if we should enable unstable features for bootstrapping.
-        let bootstrap = env::var("RUSTC_BOOTSTRAP").is_ok();
-        match (disable_unstable_features, bootstrap) {
-            (_, true) => UnstableFeatures::Cheat,
-            (true, _) => UnstableFeatures::Disallow,
-            (false, _) => UnstableFeatures::Allow
-        }
-    }
-
-    pub fn is_nightly_build(&self) -> bool {
-        match *self {
-            UnstableFeatures::Allow | UnstableFeatures::Cheat => true,
-            UnstableFeatures::Disallow => false,
-        }
-    }
-}
-
 fn maybe_stage_features(span_handler: &Handler, krate: &ast::Crate, unstable: UnstableFeatures) {
     if !unstable.is_nightly_build() {
         for attr in krate.attrs.iter().filter(|attr| attr.check_name(sym::feature)) {
diff --git a/src/libsyntax/lib.rs b/src/libsyntax/lib.rs
index fda95374f64..c2d887c9267 100644
--- a/src/libsyntax/lib.rs
+++ b/src/libsyntax/lib.rs
@@ -96,7 +96,7 @@ pub mod feature_gate {
     mod check;
     pub use check::{
         check_crate, check_attribute, get_features, feature_err, emit_feature_err,
-        GateIssue, UnstableFeatures,
+        GateIssue,
     };
 }
 pub mod mut_visit;
diff --git a/src/libsyntax/sess.rs b/src/libsyntax/sess.rs
index 740e9dfe459..aa9217c1b69 100644
--- a/src/libsyntax/sess.rs
+++ b/src/libsyntax/sess.rs
@@ -3,15 +3,15 @@
 
 use crate::ast::{CrateConfig, NodeId};
 use crate::early_buffered_lints::{BufferedEarlyLint, BufferedEarlyLintId};
-use crate::source_map::{SourceMap, FilePathMapping};
-use crate::feature_gate::UnstableFeatures;
 
 use errors::{Applicability, emitter::SilentEmitter, Handler, ColorConfig, DiagnosticBuilder};
 use rustc_data_structures::fx::{FxHashSet, FxHashMap};
 use rustc_data_structures::sync::{Lrc, Lock, Once};
+use rustc_feature::UnstableFeatures;
 use syntax_pos::{Symbol, Span, MultiSpan};
 use syntax_pos::edition::Edition;
 use syntax_pos::hygiene::ExpnId;
+use syntax_pos::source_map::{SourceMap, FilePathMapping};
 
 use std::path::PathBuf;
 use std::str;