13 files changed, 25 insertions, 14 deletions

diff --git a/compiler/rustc_ast/src/lib.rs b/compiler/rustc_ast/src/lib.rs
index 356e9fef439..6414c8e9041 100644
--- a/compiler/rustc_ast/src/lib.rs
+++ b/compiler/rustc_ast/src/lib.rs
@@ -15,7 +15,7 @@
 #![feature(box_patterns)]
 #![feature(if_let_guard)]
 #![feature(let_chains)]
-#![feature(min_specialization)]
+#![cfg_attr(bootstrap, feature(min_specialization))]
 #![feature(negative_impls)]
 #![feature(stmt_expr_attributes)]
 
diff --git a/compiler/rustc_errors/src/lib.rs b/compiler/rustc_errors/src/lib.rs
index 7216fa8f5e4..ab3ad0e9d68 100644
--- a/compiler/rustc_errors/src/lib.rs
+++ b/compiler/rustc_errors/src/lib.rs
@@ -7,6 +7,7 @@
 #![allow(internal_features)]
 #![allow(rustc::diagnostic_outside_of_impl)]
 #![allow(rustc::untranslatable_diagnostic)]
+#![cfg_attr(bootstrap, feature(min_specialization))]
 #![doc(html_root_url = "https://doc.rust-lang.org/nightly/nightly-rustc/")]
 #![doc(rust_logo)]
 #![feature(array_windows)]
@@ -16,7 +17,6 @@
 #![feature(error_reporter)]
 #![feature(extract_if)]
 #![feature(let_chains)]
-#![feature(min_specialization)]
 #![feature(negative_impls)]
 #![feature(never_type)]
 #![feature(rustc_attrs)]
diff --git a/compiler/rustc_hir/src/lib.rs b/compiler/rustc_hir/src/lib.rs
index aff946ac580..9921686ce28 100644
--- a/compiler/rustc_hir/src/lib.rs
+++ b/compiler/rustc_hir/src/lib.rs
@@ -5,7 +5,7 @@
 #![feature(associated_type_defaults)]
 #![feature(closure_track_caller)]
 #![feature(let_chains)]
-#![feature(min_specialization)]
+#![cfg_attr(bootstrap, feature(min_specialization))]
 #![feature(never_type)]
 #![feature(rustc_attrs)]
 #![feature(variant_count)]
diff --git a/compiler/rustc_hir_analysis/src/coherence/mod.rs b/compiler/rustc_hir_analysis/src/coherence/mod.rs
index 8cf1f2c9407..817dab993a3 100644
--- a/compiler/rustc_hir_analysis/src/coherence/mod.rs
+++ b/compiler/rustc_hir_analysis/src/coherence/mod.rs
@@ -10,7 +10,7 @@ use rustc_errors::{codes::*, struct_span_code_err};
 use rustc_hir::def_id::{DefId, LocalDefId};
 use rustc_middle::query::Providers;
 use rustc_middle::ty::{self, TyCtxt, TypeVisitableExt};
-use rustc_span::ErrorGuaranteed;
+use rustc_span::{sym, ErrorGuaranteed};
 use rustc_trait_selection::traits;
 
 mod builtin;
@@ -70,7 +70,11 @@ fn enforce_trait_manually_implementable(
     if let ty::trait_def::TraitSpecializationKind::AlwaysApplicable =
         tcx.trait_def(trait_def_id).specialization_kind
     {
-        if !tcx.features().specialization && !tcx.features().min_specialization {
+        if !tcx.features().specialization
+            && !tcx.features().min_specialization
+            && !impl_header_span.allows_unstable(sym::specialization)
+            && !impl_header_span.allows_unstable(sym::min_specialization)
+        {
             return Err(tcx.dcx().emit_err(errors::SpecializationTrait { span: impl_header_span }));
         }
     }
diff --git a/compiler/rustc_hir_analysis/src/lib.rs b/compiler/rustc_hir_analysis/src/lib.rs
index 883d416ecd1..1aaefc5b520 100644
--- a/compiler/rustc_hir_analysis/src/lib.rs
+++ b/compiler/rustc_hir_analysis/src/lib.rs
@@ -67,7 +67,7 @@ This API is completely unstable and subject to change.
 #![feature(is_sorted)]
 #![feature(iter_intersperse)]
 #![feature(let_chains)]
-#![feature(min_specialization)]
+#![cfg_attr(bootstrap, feature(min_specialization))]
 #![feature(never_type)]
 #![feature(lazy_cell)]
 #![feature(slice_partition_dedup)]
diff --git a/compiler/rustc_hir_typeck/src/lib.rs b/compiler/rustc_hir_typeck/src/lib.rs
index 315dc4330ad..06a14613567 100644
--- a/compiler/rustc_hir_typeck/src/lib.rs
+++ b/compiler/rustc_hir_typeck/src/lib.rs
@@ -5,7 +5,7 @@
 #![feature(try_blocks)]
 #![feature(never_type)]
 #![feature(box_patterns)]
-#![feature(min_specialization)]
+#![cfg_attr(bootstrap, feature(min_specialization))]
 #![feature(control_flow_enum)]
 
 #[macro_use]
diff --git a/compiler/rustc_infer/src/lib.rs b/compiler/rustc_infer/src/lib.rs
index 622cdf0c7b8..97f9a4b291d 100644
--- a/compiler/rustc_infer/src/lib.rs
+++ b/compiler/rustc_infer/src/lib.rs
@@ -24,7 +24,7 @@
 #![feature(let_chains)]
 #![feature(if_let_guard)]
 #![feature(iterator_try_collect)]
-#![feature(min_specialization)]
+#![cfg_attr(bootstrap, feature(min_specialization))]
 #![feature(try_blocks)]
 #![recursion_limit = "512"] // For rustdoc
 
diff --git a/compiler/rustc_mir_build/src/lib.rs b/compiler/rustc_mir_build/src/lib.rs
index 43e44b47e3f..e3f202b7f18 100644
--- a/compiler/rustc_mir_build/src/lib.rs
+++ b/compiler/rustc_mir_build/src/lib.rs
@@ -9,7 +9,7 @@
 #![feature(box_patterns)]
 #![feature(if_let_guard)]
 #![feature(let_chains)]
-#![feature(min_specialization)]
+#![cfg_attr(bootstrap, feature(min_specialization))]
 #![feature(try_blocks)]
 
 #[macro_use]
diff --git a/compiler/rustc_mir_dataflow/src/lib.rs b/compiler/rustc_mir_dataflow/src/lib.rs
index a4b58e5bfc1..f18a2354301 100644
--- a/compiler/rustc_mir_dataflow/src/lib.rs
+++ b/compiler/rustc_mir_dataflow/src/lib.rs
@@ -2,7 +2,7 @@
 #![feature(box_patterns)]
 #![feature(exact_size_is_empty)]
 #![feature(let_chains)]
-#![feature(min_specialization)]
+#![cfg_attr(bootstrap, feature(min_specialization))]
 #![feature(try_blocks)]
 
 #[macro_use]
diff --git a/compiler/rustc_mir_transform/src/lib.rs b/compiler/rustc_mir_transform/src/lib.rs
index 8e5d69605aa..ad0cd4fcff9 100644
--- a/compiler/rustc_mir_transform/src/lib.rs
+++ b/compiler/rustc_mir_transform/src/lib.rs
@@ -8,7 +8,7 @@
 #![feature(is_sorted)]
 #![feature(let_chains)]
 #![feature(map_try_insert)]
-#![feature(min_specialization)]
+#![cfg_attr(bootstrap, feature(min_specialization))]
 #![feature(never_type)]
 #![feature(option_get_or_insert_default)]
 #![feature(round_char_boundary)]
diff --git a/compiler/rustc_target/src/lib.rs b/compiler/rustc_target/src/lib.rs
index b19c5b6f28f..04c5e60aa6b 100644
--- a/compiler/rustc_target/src/lib.rs
+++ b/compiler/rustc_target/src/lib.rs
@@ -14,7 +14,7 @@
 #![feature(exhaustive_patterns)]
 #![feature(iter_intersperse)]
 #![feature(let_chains)]
-#![feature(min_specialization)]
+#![cfg_attr(bootstrap, feature(min_specialization))]
 #![feature(rustc_attrs)]
 #![feature(step_trait)]
 #![allow(internal_features)]
diff --git a/compiler/rustc_trait_selection/src/lib.rs b/compiler/rustc_trait_selection/src/lib.rs
index 053ecfc681c..00a2adccf64 100644
--- a/compiler/rustc_trait_selection/src/lib.rs
+++ b/compiler/rustc_trait_selection/src/lib.rs
@@ -24,7 +24,7 @@
 #![feature(option_take_if)]
 #![feature(never_type)]
 #![feature(type_alias_impl_trait)]
-#![feature(min_specialization)]
+#![cfg_attr(bootstrap, feature(min_specialization))]
 #![recursion_limit = "512"] // For rustdoc
 
 #[macro_use]
diff --git a/tests/ui/specialization/allow_internal_unstable.rs b/tests/ui/specialization/min_specialization/allow_internal_unstable.rs
index 317782b7b72..8f3677d9769 100644
--- a/tests/ui/specialization/allow_internal_unstable.rs
+++ b/tests/ui/specialization/min_specialization/allow_internal_unstable.rs
@@ -5,6 +5,9 @@
 #![allow(internal_features)]
 #![feature(allow_internal_unstable)]
 
+// aux-build:specialization-trait.rs
+extern crate specialization_trait;
+
 #[allow_internal_unstable(min_specialization)]
 macro_rules! test {
     () => {
@@ -12,7 +15,11 @@ macro_rules! test {
         trait Tr {}
         impl<U> Tr for T<U> {}
         impl Tr for T<u8> {}
-    }
+
+        impl<U> specialization_trait::SpecTrait for T<U> {
+            fn method(&self) {}
+        }
+    };
 }
 
 test! {}