Rollup merge of #85850 - bjorn3:less_feature_gates, r=jyn514

Remove unused feature gates

The first commit removes a usage of a feature gate, but I don't expect it to be controversial as the feature gate was only used to workaround a limitation of rust in the past. (closures never being `Clone`)

The second commit uses `#[allow_internal_unstable]` to avoid leaking the `trusted_step` feature gate usage from inside the index newtype macro. It didn't work for the `min_specialization` feature gate though.

The third commit removes (almost) all feature gates from the compiler that weren't used anyway.

Author: JohnTitor

compiler/rustc_ast/src/lib.rs

@@ -12,13 +12,11 @@
 #![feature(box_patterns)]
 #![cfg_attr(bootstrap, feature(const_fn_unsize))]
 #![feature(const_fn_transmute)]
-#![feature(const_panic)]
 #![feature(crate_visibility_modifier)]
 #![feature(iter_zip)]
 #![feature(label_break_value)]
 #![feature(nll)]
 #![feature(min_specialization)]
-#![feature(trusted_step)]
 #![recursion_limit = "256"]
 
 #[macro_use]

compiler/rustc_ast_passes/src/lib.rs

@@ -6,7 +6,6 @@
 
 #![feature(bindings_after_at)]
 #![feature(iter_is_partitioned)]
-#![feature(box_syntax)]
 #![feature(box_patterns)]
 #![recursion_limit = "256"]
 

compiler/rustc_codegen_ssa/src/lib.rs

@@ -1,15 +1,11 @@
 #![doc(html_root_url = "https://doc.rust-lang.org/nightly/nightly-rustc/")]
-#![feature(assert_matches)]
 #![feature(bool_to_option)]
 #![feature(box_patterns)]
-#![feature(drain_filter)]
 #![feature(try_blocks)]
 #![feature(in_band_lifetimes)]
 #![feature(nll)]
 #![feature(associated_type_bounds)]
-#![feature(iter_zip)]
 #![recursion_limit = "256"]
-#![feature(box_syntax)]
 
 //! This crate contains codegen code that is used by all codegen backends (LLVM and others).
 //! The backend-agnostic functions of this crate use functions defined in various traits that

compiler/rustc_data_structures/src/lib.rs

@@ -10,15 +10,12 @@
 #![feature(array_windows)]
 #![feature(control_flow_enum)]
 #![feature(in_band_lifetimes)]
-#![feature(unboxed_closures)]
 #![feature(generator_trait)]
-#![feature(fn_traits)]
 #![feature(min_specialization)]
 #![feature(auto_traits)]
 #![feature(nll)]
 #![feature(allow_internal_unstable)]
 #![feature(hash_raw_entry)]
-#![feature(stmt_expr_attributes)]
 #![feature(core_intrinsics)]
 #![feature(test)]
 #![feature(associated_type_bounds)]

compiler/rustc_data_structures/src/obligation_forest/mod.rs

@@ -597,7 +597,7 @@ impl<O: ForestObligation> ObligationForest<O> {
                 Some(rpos) => {
                     // Cycle detected.
                     processor.process_backedge(
-                        stack[rpos..].iter().map(GetObligation(&self.nodes)),
+                        stack[rpos..].iter().map(|&i| &self.nodes[i].obligation),
                         PhantomData,
                     );
                 }
@@ -705,20 +705,3 @@ impl<O: ForestObligation> ObligationForest<O> {
         });
     }
 }
-
-// I need a Clone closure.
-#[derive(Clone)]
-struct GetObligation<'a, O>(&'a [Node<O>]);
-
-impl<'a, 'b, O> FnOnce<(&'b usize,)> for GetObligation<'a, O> {
-    type Output = &'a O;
-    extern "rust-call" fn call_once(self, args: (&'b usize,)) -> &'a O {
-        &self.0[*args.0].obligation
-    }
-}
-
-impl<'a, 'b, O> FnMut<(&'b usize,)> for GetObligation<'a, O> {
-    extern "rust-call" fn call_mut(&mut self, args: (&'b usize,)) -> &'a O {
-        &self.0[*args.0].obligation
-    }
-}

compiler/rustc_expand/src/lib.rs

@@ -1,4 +1,3 @@
-#![feature(bool_to_option)]
 #![feature(crate_visibility_modifier)]
 #![feature(decl_macro)]
 #![feature(destructuring_assignment)]

compiler/rustc_hir/src/lib.rs

@@ -3,12 +3,10 @@
 //! [rustc dev guide]: https://rustc-dev-guide.rust-lang.org/hir.html
 
 #![feature(crate_visibility_modifier)]
-#![feature(const_panic)]
 #![cfg_attr(bootstrap, feature(extended_key_value_attributes))]
 #![feature(in_band_lifetimes)]
 #![feature(once_cell)]
 #![feature(min_specialization)]
-#![feature(trusted_step)]
 #![recursion_limit = "256"]
 
 #[macro_use]

compiler/rustc_index/src/lib.rs

@@ -1,12 +1,10 @@
 #![feature(allow_internal_unstable)]
 #![feature(bench_black_box)]
-#![feature(const_panic)]
 #![feature(extend_one)]
 #![feature(iter_zip)]
 #![feature(unboxed_closures)]
 #![feature(test)]
 #![feature(fn_traits)]
-#![feature(trusted_step)]
 
 pub mod bit_set;
 pub mod vec;

compiler/rustc_index/src/vec.rs

@@ -65,7 +65,7 @@ impl Idx for u32 {
 /// `u32::MAX`. You can also customize things like the `Debug` impl,
 /// what traits are derived, and so forth via the macro.
 #[macro_export]
-#[allow_internal_unstable(step_trait, rustc_attrs)]
+#[allow_internal_unstable(step_trait, rustc_attrs, trusted_step)]
 macro_rules! newtype_index {
     // ---- public rules ----
 

compiler/rustc_infer/src/lib.rs

@@ -16,14 +16,12 @@
 #![feature(bool_to_option)]
 #![feature(box_patterns)]
 #![feature(box_syntax)]
-#![feature(const_panic)]
 #![feature(extend_one)]
 #![feature(iter_zip)]
 #![feature(never_type)]
 #![feature(in_band_lifetimes)]
 #![feature(control_flow_enum)]
 #![feature(min_specialization)]
-#![feature(trusted_step)]
 #![recursion_limit = "512"] // For rustdoc
 
 #[macro_use]