Rename optin_builtin_traits to auto_traits

They were originally called "opt-in, built-in traits" (OIBITs), but
people realized that the name was too confusing and a mouthful, and so
they were renamed to just "auto traits". The feature flag's name wasn't
updated, though, so that's what this PR does.

There are some other spots in the compiler that still refer to OIBITs,
but I don't think changing those now is worth it since they are internal
and not particularly relevant to this PR.

Also see <https://rust-lang.zulipchat.com/#narrow/stream/131828-t-compiler/topic/opt-in.2C.20built-in.20traits.20(auto.20traits).20feature.20name>.

compiler/rustc_ast_passes/src/feature_gate.rs

@@ -370,7 +370,7 @@ impl<'a> Visitor<'a> for PostExpansionVisitor<'a> {
             ast::ItemKind::Trait(ast::IsAuto::Yes, ..) => {
                 gate_feature_post!(
                     &self,
-                    optin_builtin_traits,
+                    auto_traits,
                     i.span,
                     "auto traits are experimental and possibly buggy"
                 );

compiler/rustc_codegen_cranelift/example/mini_core.rs

@@ -1,6 +1,6 @@
 #![feature(
     no_core, lang_items, intrinsics, unboxed_closures, type_ascription, extern_types,
-    untagged_unions, decl_macro, rustc_attrs, transparent_unions, optin_builtin_traits,
+    untagged_unions, decl_macro, rustc_attrs, transparent_unions, auto_traits,
     thread_local,
 )]
 #![no_core]

compiler/rustc_data_structures/src/lib.rs

@@ -15,7 +15,8 @@
 #![feature(fn_traits)]
 #![feature(int_bits_const)]
 #![feature(min_specialization)]
-#![feature(optin_builtin_traits)]
+#![cfg_attr(bootstrap, feature(optin_builtin_traits))]
+#![cfg_attr(not(bootstrap), feature(auto_traits))]
 #![feature(nll)]
 #![feature(allow_internal_unstable)]
 #![feature(hash_raw_entry)]

compiler/rustc_error_codes/src/error_codes/E0198.md

@@ -16,7 +16,7 @@ unsafe.
 This will compile:
 
 ```ignore (ignore auto_trait future compatibility warning)
-#![feature(optin_builtin_traits)]
+#![feature(auto_traits)]
 
 struct Foo;
 

compiler/rustc_error_codes/src/error_codes/E0321.md

@@ -4,7 +4,7 @@ or enum type.
 Erroneous code example:
 
 ```compile_fail,E0321
-#![feature(optin_builtin_traits)]
+#![feature(auto_traits)]
 
 struct Foo;
 

compiler/rustc_error_codes/src/error_codes/E0567.md

@@ -3,7 +3,7 @@ Generics have been used on an auto trait.
 Erroneous code example:
 
 ```compile_fail,E0567
-#![feature(optin_builtin_traits)]
+#![feature(auto_traits)]
 
 auto trait Generic<T> {} // error!
 # fn main() {}
@@ -16,7 +16,7 @@ parameters.
 To fix this issue, just remove the generics:
 
 ```
-#![feature(optin_builtin_traits)]
+#![feature(auto_traits)]
 
 auto trait Generic {} // ok!
 # fn main() {}

compiler/rustc_error_codes/src/error_codes/E0568.md

@@ -3,7 +3,7 @@ A super trait has been added to an auto trait.
 Erroneous code example:
 
 ```compile_fail,E0568
-#![feature(optin_builtin_traits)]
+#![feature(auto_traits)]
 
 auto trait Bound : Copy {} // error!
 
@@ -18,7 +18,7 @@ all the existing types could implement `Bound` because very few of them have the
 To fix this issue, just remove the super trait:
 
 ```
-#![feature(optin_builtin_traits)]
+#![feature(auto_traits)]
 
 auto trait Bound {} // ok!
 

compiler/rustc_feature/src/active.rs

@@ -149,9 +149,6 @@ declare_features! (
     /// Allows using the `#[linkage = ".."]` attribute.
     (active, linkage, "1.0.0", Some(29603), None),
 
-    /// Allows features specific to OIBIT (auto traits).
-    (active, optin_builtin_traits, "1.0.0", Some(13231), None),
-
     /// Allows using `box` in patterns (RFC 469).
     (active, box_patterns, "1.0.0", Some(29641), None),
 
@@ -215,6 +212,10 @@ declare_features! (
     /// purpose as `#[allow_internal_unstable]`.
     (active, rustc_allow_const_fn_unstable, "1.49.0", Some(69399), None),
 
+    /// Allows features specific to auto traits.
+    /// Renamed from `optin_builtin_traits`.
+    (active, auto_traits, "1.50.0", Some(13231), None),
+
     // no-tracking-issue-end
 
     // -------------------------------------------------------------------------

compiler/rustc_feature/src/removed.rs

@@ -71,6 +71,10 @@ declare_features! (
     /// Allows using custom attributes (RFC 572).
     (removed, custom_attribute, "1.0.0", Some(29642), None,
      Some("removed in favor of `#![register_tool]` and `#![register_attr]`")),
+    /// Allows features specific to OIBIT (now called auto traits).
+    /// Renamed to `auto_traits`.
+    (removed, optin_builtin_traits, "1.0.0", Some(13231), None,
+     Some("renamed to `auto_traits`")),
     (removed, pushpop_unsafe, "1.2.0", None, None, None),
     (removed, needs_allocator, "1.4.0", Some(27389), None,
      Some("subsumed by `#![feature(allocator_internals)]`")),
@@ -113,7 +117,6 @@ declare_features! (
      Some("removed in favor of `#![feature(marker_trait_attr)]`")),
     /// Allows `#[no_debug]`.
     (removed, no_debug, "1.43.0", Some(29721), None, Some("removed due to lack of demand")),
-
     /// Allows comparing raw pointers during const eval.
     (removed, const_compare_raw_pointers, "1.46.0", Some(53020), None,
      Some("cannot be allowed in const eval in any meaningful way")),

compiler/rustc_span/src/symbol.rs

@@ -285,6 +285,7 @@ symbols! {
         attr_literals,
         attributes,
         augmented_assignments,
+        auto_traits,
         automatically_derived,
         avx512_target_feature,
         await_macro,

library/alloc/src/lib.rs

@@ -112,7 +112,8 @@
 #![feature(never_type)]
 #![feature(nll)]
 #![feature(nonnull_slice_from_raw_parts)]
-#![feature(optin_builtin_traits)]
+#![cfg_attr(bootstrap, feature(optin_builtin_traits))]
+#![cfg_attr(not(bootstrap), feature(auto_traits))]
 #![feature(or_patterns)]
 #![feature(pattern)]
 #![feature(ptr_internals)]

library/core/src/lib.rs

@@ -119,7 +119,8 @@
 #![feature(nll)]
 #![feature(exhaustive_patterns)]
 #![feature(no_core)]
-#![feature(optin_builtin_traits)]
+#![cfg_attr(bootstrap, feature(optin_builtin_traits))]
+#![cfg_attr(not(bootstrap), feature(auto_traits))]
 #![feature(or_patterns)]
 #![feature(prelude_import)]
 #![feature(repr_simd, platform_intrinsics)]

library/proc_macro/src/lib.rs

@@ -28,7 +28,8 @@
 #![feature(extern_types)]
 #![feature(in_band_lifetimes)]
 #![feature(negative_impls)]
-#![feature(optin_builtin_traits)]
+#![cfg_attr(bootstrap, feature(optin_builtin_traits))]
+#![cfg_attr(not(bootstrap), feature(auto_traits))]
 #![feature(restricted_std)]
 #![feature(rustc_attrs)]
 #![feature(min_specialization)]

library/rtstartup/rsbegin.rs

@@ -9,10 +9,13 @@
 // headers or footers.
 //
 // Note that the actual module entry point is located in the C runtime startup
-// object (usually called `crtX.o), which then invokes initialization callbacks
+// object (usually called `crtX.o`), which then invokes initialization callbacks
 // of other runtime components (registered via yet another special image section).
 
-#![feature(no_core, lang_items, optin_builtin_traits)]
+#![feature(no_core)]
+#![feature(lang_items)]
+#![cfg_attr(bootstrap, feature(optin_builtin_traits))]
+#![cfg_attr(not(bootstrap), feature(auto_traits))]
 #![crate_type = "rlib"]
 #![no_core]
 #![allow(non_camel_case_types)]

library/rtstartup/rsend.rs

@@ -1,6 +1,9 @@
 // See rsbegin.rs for details.
 
-#![feature(no_core, lang_items, optin_builtin_traits)]
+#![feature(no_core)]
+#![feature(lang_items)]
+#![cfg_attr(bootstrap, feature(optin_builtin_traits))]
+#![cfg_attr(not(bootstrap), feature(auto_traits))]
 #![crate_type = "rlib"]
 #![no_core]
 

library/std/src/lib.rs

@@ -286,7 +286,8 @@
 #![feature(nll)]
 #![feature(nonnull_slice_from_raw_parts)]
 #![feature(once_cell)]
-#![feature(optin_builtin_traits)]
+#![cfg_attr(bootstrap, feature(optin_builtin_traits))]
+#![cfg_attr(not(bootstrap), feature(auto_traits))]
 #![feature(or_patterns)]
 #![feature(panic_info_message)]
 #![feature(panic_internals)]

src/doc/unstable-book/src/language-features/optin-builtin-traits.md → src/doc/unstable-book/src/language-features/auto-traits.md

@@ -1,12 +1,12 @@
-# `optin_builtin_traits`
+# `auto_traits`
 
 The tracking issue for this feature is [#13231] 
 
 [#13231]: https://github.com/rust-lang/rust/issues/13231
 
 ----
 
-The `optin_builtin_traits` feature gate allows you to define auto traits.
+The `auto_traits` feature gate allows you to define auto traits.
 
 Auto traits, like [`Send`] or [`Sync`] in the standard library, are marker traits
 that are automatically implemented for every type, unless the type, or a type it contains, 
@@ -24,7 +24,7 @@ Example:
 
 ```rust
 #![feature(negative_impls)]
-#![feature(optin_builtin_traits)]
+#![feature(auto_traits)]
 
 auto trait Valid {}
 

src/test/pretty/auto-trait.rs

@@ -1,4 +1,4 @@
-#![feature(optin_builtin_traits)]
+#![feature(auto_traits)]
 
 // pp-exact
 

src/test/run-make-fulldeps/simd-ffi/simd.rs

@@ -2,7 +2,7 @@
 #![crate_type = "lib"]
 // we can compile to a variety of platforms, because we don't need
 // cross-compiled standard libraries.
-#![feature(no_core, optin_builtin_traits)]
+#![feature(no_core, auto_traits)]
 #![no_core]
 #![feature(repr_simd, simd_ffi, link_llvm_intrinsics, lang_items, rustc_attrs)]
 

src/test/run-make-fulldeps/target-specs/foo.rs

@@ -1,4 +1,4 @@
-#![feature(lang_items, no_core, optin_builtin_traits)]
+#![feature(lang_items, no_core, auto_traits)]
 #![no_core]
 
 #[lang="copy"]

src/test/rustdoc/auto-traits.rs

@@ -1,6 +1,6 @@
 // aux-build:auto-traits.rs
 
-#![feature(optin_builtin_traits)]
+#![feature(auto_traits)]
 
 #![crate_name = "foo"]
 

src/test/rustdoc/auto_aliases.rs

@@ -1,4 +1,4 @@
-#![feature(optin_builtin_traits)]
+#![feature(auto_traits)]
 
 // @has auto_aliases/trait.Bar.html '//h3[@aliases="auto_aliases::Foo"]' 'impl Bar for Foo'
 pub struct Foo;

src/test/rustdoc/auxiliary/auto-traits.rs

@@ -1,3 +1,3 @@
-#![feature(optin_builtin_traits)]
+#![feature(auto_traits)]
 
 pub unsafe auto trait Bar {}

src/test/rustdoc/auxiliary/rustdoc-default-impl.rs

@@ -1,4 +1,4 @@
-#![feature(optin_builtin_traits)]
+#![feature(auto_traits)]
 
 pub mod bar {
     use std::marker;

src/test/rustdoc/auxiliary/rustdoc-impl-parts-crosscrate.rs

@@ -1,3 +1,3 @@
-#![feature(optin_builtin_traits)]
+#![feature(auto_traits)]
 
 pub auto trait AnOibit {}

src/test/rustdoc/impl-parts.rs

@@ -1,5 +1,5 @@
 #![feature(negative_impls)]
-#![feature(optin_builtin_traits)]
+#![feature(auto_traits)]
 
 pub auto trait AnOibit {}
 

src/test/rustdoc/synthetic_auto/crate-local.rs

@@ -1,4 +1,4 @@
-#![feature(optin_builtin_traits)]
+#![feature(auto_traits)]
 
 pub auto trait Banana {}
 

src/test/ui/async-await/issue-64130-3-other.rs

@@ -1,4 +1,4 @@
-#![feature(optin_builtin_traits)]
+#![feature(auto_traits)]
 #![feature(negative_impls)]
 // edition:2018
 

src/test/ui/auto-traits/auto-trait-validation.rs

@@ -1,4 +1,4 @@
-#![feature(optin_builtin_traits)]
+#![feature(auto_traits)]
 
 auto trait Generic<T> {}
 //~^ auto traits cannot have generic parameters [E0567]

src/test/ui/auto-traits/auto-traits.rs

@@ -1,6 +1,6 @@
 // run-pass
 #![allow(unused_doc_comments)]
-#![feature(optin_builtin_traits)]
+#![feature(auto_traits)]
 #![feature(negative_impls)]
 
 auto trait Auto {}

src/test/ui/auto-traits/issue-23080-2.rs

@@ -1,4 +1,4 @@
-#![feature(optin_builtin_traits)]
+#![feature(auto_traits)]
 #![feature(negative_impls)]
 
 unsafe auto trait Trait {

src/test/ui/auto-traits/issue-23080.rs

@@ -1,4 +1,4 @@
-#![feature(optin_builtin_traits)]
+#![feature(auto_traits)]
 #![feature(negative_impls)]
 
 unsafe auto trait Trait {

src/test/ui/auto-traits/typeck-auto-trait-no-supertraits-2.rs

@@ -1,4 +1,4 @@
-#![feature(optin_builtin_traits)]
+#![feature(auto_traits)]
 #![feature(negative_impls)]
 
 auto trait Magic : Sized where Option<Self> : Magic {} //~ ERROR E0568

src/test/ui/auto-traits/typeck-auto-trait-no-supertraits.rs

@@ -22,7 +22,7 @@
 //    println!("{:?} {:?}", a, b);
 // }
 
-#![feature(optin_builtin_traits)]
+#![feature(auto_traits)]
 #![feature(negative_impls)]
 
 auto trait Magic: Copy {} //~ ERROR E0568

src/test/ui/auto-traits/typeck-default-trait-impl-constituent-types-2.rs

@@ -1,4 +1,4 @@
-#![feature(optin_builtin_traits)]
+#![feature(auto_traits)]
 #![feature(negative_impls)]
 
 auto trait MyTrait {}

src/test/ui/auto-traits/typeck-default-trait-impl-constituent-types.rs

@@ -1,4 +1,4 @@
-#![feature(optin_builtin_traits)]
+#![feature(auto_traits)]
 #![feature(negative_impls)]
 
 auto trait MyTrait {}

src/test/ui/auto-traits/typeck-default-trait-impl-negation.rs

@@ -1,4 +1,4 @@
-#![feature(optin_builtin_traits)]
+#![feature(auto_traits)]
 #![feature(negative_impls)]
 
 auto trait MyTrait {}

src/test/ui/auto-traits/typeck-default-trait-impl-precedence.rs

@@ -3,7 +3,7 @@
 // other words, the auto impl only applies if there are no existing
 // impls whose types unify.
 
-#![feature(optin_builtin_traits)]
+#![feature(auto_traits)]
 #![feature(negative_impls)]
 
 auto trait Defaulted { }

src/test/ui/coherence/coherence-default-trait-impl.rs

@@ -1,4 +1,4 @@
-#![feature(optin_builtin_traits)]
+#![feature(auto_traits)]
 #![feature(negative_impls)]
 
 auto trait MySafeTrait {}

src/test/ui/coherence/coherence-impl-trait-for-marker-trait-negative.rs

@@ -1,4 +1,4 @@
-#![feature(optin_builtin_traits)]
+#![feature(auto_traits)]
 #![feature(negative_impls)]
 
 // Test for issue #56934 - that it is impossible to redundantly

src/test/ui/coherence/coherence-impl-trait-for-marker-trait-positive.rs

@@ -1,4 +1,4 @@
-#![feature(optin_builtin_traits)]
+#![feature(auto_traits)]
 #![feature(negative_impls)]
 
 // Test for issue #56934 - that it is impossible to redundantly

src/test/ui/feature-gates/feature-gate-optin-builtin-traits.rs → src/test/ui/feature-gates/feature-gate-auto-traits.rs

@@ -1,5 +1,5 @@
 // Test that default and negative trait implementations are gated by
-// `optin_builtin_traits` feature gate
+// `auto_traits` feature gate
 
 struct DummyStruct;