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>.

54 files changed, 78 insertions, 62 deletions

diff --git a/compiler/rustc_ast_passes/src/feature_gate.rs b/compiler/rustc_ast_passes/src/feature_gate.rs
index 181783441f3..5b75fbf339b 100644
--- a/compiler/rustc_ast_passes/src/feature_gate.rs
+++ b/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"
                 );
diff --git a/compiler/rustc_codegen_cranelift/example/mini_core.rs b/compiler/rustc_codegen_cranelift/example/mini_core.rs
index ce07fe83df1..10cba992056 100644
--- a/compiler/rustc_codegen_cranelift/example/mini_core.rs
+++ b/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]
diff --git a/compiler/rustc_data_structures/src/lib.rs b/compiler/rustc_data_structures/src/lib.rs
index 01604477c3e..d903a557c7f 100644
--- a/compiler/rustc_data_structures/src/lib.rs
+++ b/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)]
diff --git a/compiler/rustc_error_codes/src/error_codes/E0198.md b/compiler/rustc_error_codes/src/error_codes/E0198.md
index 90f1e542874..1238165cb88 100644
--- a/compiler/rustc_error_codes/src/error_codes/E0198.md
+++ b/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;
 
diff --git a/compiler/rustc_error_codes/src/error_codes/E0321.md b/compiler/rustc_error_codes/src/error_codes/E0321.md
index bfcdabfe9de..bcfc12897c5 100644
--- a/compiler/rustc_error_codes/src/error_codes/E0321.md
+++ b/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;
 
diff --git a/compiler/rustc_error_codes/src/error_codes/E0567.md b/compiler/rustc_error_codes/src/error_codes/E0567.md
index 05cf8fed031..bc13ee4c04c 100644
--- a/compiler/rustc_error_codes/src/error_codes/E0567.md
+++ b/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() {}
diff --git a/compiler/rustc_error_codes/src/error_codes/E0568.md b/compiler/rustc_error_codes/src/error_codes/E0568.md
index a37381f1cbd..17b3f5e31bd 100644
--- a/compiler/rustc_error_codes/src/error_codes/E0568.md
+++ b/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!
 
diff --git a/compiler/rustc_feature/src/active.rs b/compiler/rustc_feature/src/active.rs
index a0355079247..75337634d3f 100644
--- a/compiler/rustc_feature/src/active.rs
+++ b/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
 
     // -------------------------------------------------------------------------
diff --git a/compiler/rustc_feature/src/removed.rs b/compiler/rustc_feature/src/removed.rs
index a480ddc7f34..07bd1602cda 100644
--- a/compiler/rustc_feature/src/removed.rs
+++ b/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")),
diff --git a/compiler/rustc_span/src/symbol.rs b/compiler/rustc_span/src/symbol.rs
index 338ff005995..d5fccdeb189 100644
--- a/compiler/rustc_span/src/symbol.rs
+++ b/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,
diff --git a/library/alloc/src/lib.rs b/library/alloc/src/lib.rs
index dc5db49ee98..3ac34c9ae28 100644
--- a/library/alloc/src/lib.rs
+++ b/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)]
diff --git a/library/core/src/lib.rs b/library/core/src/lib.rs
index 0f91ff418e3..d01cefdcda8 100644
--- a/library/core/src/lib.rs
+++ b/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)]
diff --git a/library/proc_macro/src/lib.rs b/library/proc_macro/src/lib.rs
index 3ba706b09e8..5ca7cbe973f 100644
--- a/library/proc_macro/src/lib.rs
+++ b/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)]
diff --git a/library/rtstartup/rsbegin.rs b/library/rtstartup/rsbegin.rs
index bd1946133e8..b64f13dba4c 100644
--- a/library/rtstartup/rsbegin.rs
+++ b/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)]
diff --git a/library/rtstartup/rsend.rs b/library/rtstartup/rsend.rs
index 333761cd977..18ee7c19ba0 100644
--- a/library/rtstartup/rsend.rs
+++ b/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]
 
diff --git a/library/std/src/lib.rs b/library/std/src/lib.rs
index 3463b8cdf1c..f33804c988a 100644
--- a/library/std/src/lib.rs
+++ b/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)]
diff --git a/src/doc/unstable-book/src/language-features/optin-builtin-traits.md b/src/doc/unstable-book/src/language-features/auto-traits.md
index 6f0f0cfd33e..0ca6dd6670b 100644
--- a/src/doc/unstable-book/src/language-features/optin-builtin-traits.md
+++ b/src/doc/unstable-book/src/language-features/auto-traits.md
@@ -1,4 +1,4 @@
-# `optin_builtin_traits`
+# `auto_traits`
 
 The tracking issue for this feature is [#13231] 
 
@@ -6,7 +6,7 @@ The tracking issue for this feature is [#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 {}
 
diff --git a/src/test/pretty/auto-trait.rs b/src/test/pretty/auto-trait.rs
index 2eb4d3390be..61644e7df09 100644
--- a/src/test/pretty/auto-trait.rs
+++ b/src/test/pretty/auto-trait.rs
@@ -1,4 +1,4 @@
-#![feature(optin_builtin_traits)]
+#![feature(auto_traits)]
 
 // pp-exact
 
diff --git a/src/test/run-make-fulldeps/simd-ffi/simd.rs b/src/test/run-make-fulldeps/simd-ffi/simd.rs
index c63fe4ddce2..717da367fee 100644
--- a/src/test/run-make-fulldeps/simd-ffi/simd.rs
+++ b/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)]
 
diff --git a/src/test/run-make-fulldeps/target-specs/foo.rs b/src/test/run-make-fulldeps/target-specs/foo.rs
index 42130068695..ee443eb0aa3 100644
--- a/src/test/run-make-fulldeps/target-specs/foo.rs
+++ b/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"]
diff --git a/src/test/rustdoc/auto-traits.rs b/src/test/rustdoc/auto-traits.rs
index a1fa611994f..93d4bf2f656 100644
--- a/src/test/rustdoc/auto-traits.rs
+++ b/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"]
 
diff --git a/src/test/rustdoc/auto_aliases.rs b/src/test/rustdoc/auto_aliases.rs
index 7b52a69f560..b8f3527510c 100644
--- a/src/test/rustdoc/auto_aliases.rs
+++ b/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;
diff --git a/src/test/rustdoc/auxiliary/auto-traits.rs b/src/test/rustdoc/auxiliary/auto-traits.rs
index f5221061388..84976c73bee 100644
--- a/src/test/rustdoc/auxiliary/auto-traits.rs
+++ b/src/test/rustdoc/auxiliary/auto-traits.rs
@@ -1,3 +1,3 @@
-#![feature(optin_builtin_traits)]
+#![feature(auto_traits)]
 
 pub unsafe auto trait Bar {}
diff --git a/src/test/rustdoc/auxiliary/rustdoc-default-impl.rs b/src/test/rustdoc/auxiliary/rustdoc-default-impl.rs
index 36e2821c5a8..032db3b25e6 100644
--- a/src/test/rustdoc/auxiliary/rustdoc-default-impl.rs
+++ b/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;
diff --git a/src/test/rustdoc/auxiliary/rustdoc-impl-parts-crosscrate.rs b/src/test/rustdoc/auxiliary/rustdoc-impl-parts-crosscrate.rs
index 869aebc774a..46adf2e6bc0 100644
--- a/src/test/rustdoc/auxiliary/rustdoc-impl-parts-crosscrate.rs
+++ b/src/test/rustdoc/auxiliary/rustdoc-impl-parts-crosscrate.rs
@@ -1,3 +1,3 @@
-#![feature(optin_builtin_traits)]
+#![feature(auto_traits)]
 
 pub auto trait AnOibit {}
diff --git a/src/test/rustdoc/impl-parts.rs b/src/test/rustdoc/impl-parts.rs
index 68baca9a04e..5e9e84a554b 100644
--- a/src/test/rustdoc/impl-parts.rs
+++ b/src/test/rustdoc/impl-parts.rs
@@ -1,5 +1,5 @@
 #![feature(negative_impls)]
-#![feature(optin_builtin_traits)]
+#![feature(auto_traits)]
 
 pub auto trait AnOibit {}
 
diff --git a/src/test/rustdoc/synthetic_auto/crate-local.rs b/src/test/rustdoc/synthetic_auto/crate-local.rs
index 341dd572f81..3346ac05ffe 100644
--- a/src/test/rustdoc/synthetic_auto/crate-local.rs
+++ b/src/test/rustdoc/synthetic_auto/crate-local.rs
@@ -1,4 +1,4 @@
-#![feature(optin_builtin_traits)]
+#![feature(auto_traits)]
 
 pub auto trait Banana {}
 
diff --git a/src/test/ui/async-await/issue-64130-3-other.rs b/src/test/ui/async-await/issue-64130-3-other.rs
index 133152c309a..7f2e3db6d60 100644
--- a/src/test/ui/async-await/issue-64130-3-other.rs
+++ b/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
 
diff --git a/src/test/ui/auto-traits/auto-trait-validation.rs b/src/test/ui/auto-traits/auto-trait-validation.rs
index 34d6c3da00e..a997b044c8f 100644
--- a/src/test/ui/auto-traits/auto-trait-validation.rs
+++ b/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]
diff --git a/src/test/ui/auto-traits/auto-traits.rs b/src/test/ui/auto-traits/auto-traits.rs
index 15fdddc5f3f..567b86c2762 100644
--- a/src/test/ui/auto-traits/auto-traits.rs
+++ b/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 {}
diff --git a/src/test/ui/auto-traits/issue-23080-2.rs b/src/test/ui/auto-traits/issue-23080-2.rs
index 867f24f8cb4..cb4cf6de1ef 100644
--- a/src/test/ui/auto-traits/issue-23080-2.rs
+++ b/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 {
diff --git a/src/test/ui/auto-traits/issue-23080.rs b/src/test/ui/auto-traits/issue-23080.rs
index 035db82ba5d..84e2ce66f9d 100644
--- a/src/test/ui/auto-traits/issue-23080.rs
+++ b/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 {
diff --git a/src/test/ui/auto-traits/typeck-auto-trait-no-supertraits-2.rs b/src/test/ui/auto-traits/typeck-auto-trait-no-supertraits-2.rs
index 8824a6d2767..6cceaf821f6 100644
--- a/src/test/ui/auto-traits/typeck-auto-trait-no-supertraits-2.rs
+++ b/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
diff --git a/src/test/ui/auto-traits/typeck-auto-trait-no-supertraits.rs b/src/test/ui/auto-traits/typeck-auto-trait-no-supertraits.rs
index edbca915124..2a76893febc 100644
--- a/src/test/ui/auto-traits/typeck-auto-trait-no-supertraits.rs
+++ b/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
diff --git a/src/test/ui/auto-traits/typeck-default-trait-impl-constituent-types-2.rs b/src/test/ui/auto-traits/typeck-default-trait-impl-constituent-types-2.rs
index 71ac2b466c1..f2fb67f1108 100644
--- a/src/test/ui/auto-traits/typeck-default-trait-impl-constituent-types-2.rs
+++ b/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 {}
diff --git a/src/test/ui/auto-traits/typeck-default-trait-impl-constituent-types.rs b/src/test/ui/auto-traits/typeck-default-trait-impl-constituent-types.rs
index 6483b9213dc..73ff46d05e4 100644
--- a/src/test/ui/auto-traits/typeck-default-trait-impl-constituent-types.rs
+++ b/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 {}
diff --git a/src/test/ui/auto-traits/typeck-default-trait-impl-negation.rs b/src/test/ui/auto-traits/typeck-default-trait-impl-negation.rs
index 47cab60625d..f7f56f97f61 100644
--- a/src/test/ui/auto-traits/typeck-default-trait-impl-negation.rs
+++ b/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 {}
diff --git a/src/test/ui/auto-traits/typeck-default-trait-impl-precedence.rs b/src/test/ui/auto-traits/typeck-default-trait-impl-precedence.rs
index 614a5ff55b1..2bbe82270bd 100644
--- a/src/test/ui/auto-traits/typeck-default-trait-impl-precedence.rs
+++ b/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 { }
diff --git a/src/test/ui/coherence/coherence-default-trait-impl.rs b/src/test/ui/coherence/coherence-default-trait-impl.rs
index 4115ba34e17..d57fb477754 100644
--- a/src/test/ui/coherence/coherence-default-trait-impl.rs
+++ b/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 {}
diff --git a/src/test/ui/coherence/coherence-impl-trait-for-marker-trait-negative.rs b/src/test/ui/coherence/coherence-impl-trait-for-marker-trait-negative.rs
index a9c8d20a79d..50d9a480ad1 100644
--- a/src/test/ui/coherence/coherence-impl-trait-for-marker-trait-negative.rs
+++ b/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
diff --git a/src/test/ui/coherence/coherence-impl-trait-for-marker-trait-positive.rs b/src/test/ui/coherence/coherence-impl-trait-for-marker-trait-positive.rs
index c565f9c83e8..faac6d983f3 100644
--- a/src/test/ui/coherence/coherence-impl-trait-for-marker-trait-positive.rs
+++ b/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
diff --git a/src/test/ui/feature-gates/feature-gate-optin-builtin-traits.rs b/src/test/ui/feature-gates/feature-gate-auto-traits.rs
index 35c05b75d36..80cfa9cee89 100644
--- a/src/test/ui/feature-gates/feature-gate-optin-builtin-traits.rs
+++ b/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;
 
diff --git a/src/test/ui/feature-gates/feature-gate-optin-builtin-traits.stderr b/src/test/ui/feature-gates/feature-gate-auto-traits.stderr
index 1553d0531dc..e015418161e 100644
--- a/src/test/ui/feature-gates/feature-gate-optin-builtin-traits.stderr
+++ b/src/test/ui/feature-gates/feature-gate-auto-traits.stderr
@@ -1,14 +1,14 @@
 error[E0658]: auto traits are experimental and possibly buggy
-  --> $DIR/feature-gate-optin-builtin-traits.rs:6:1
+  --> $DIR/feature-gate-auto-traits.rs:6:1
    |
 LL | auto trait AutoDummyTrait {}
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    |
    = note: see issue #13231 <https://github.com/rust-lang/rust/issues/13231> for more information
-   = help: add `#![feature(optin_builtin_traits)]` to the crate attributes to enable
+   = help: add `#![feature(auto_traits)]` to the crate attributes to enable
 
 error[E0658]: negative trait bounds are not yet fully implemented; use marker types for now
-  --> $DIR/feature-gate-optin-builtin-traits.rs:9:6
+  --> $DIR/feature-gate-auto-traits.rs:9:6
    |
 LL | impl !AutoDummyTrait for DummyStruct {}
    |      ^^^^^^^^^^^^^^^
diff --git a/src/test/ui/generator/auto-trait-regions.rs b/src/test/ui/generator/auto-trait-regions.rs
index 1e77d8058a7..8f1e4f1b66f 100644
--- a/src/test/ui/generator/auto-trait-regions.rs
+++ b/src/test/ui/generator/auto-trait-regions.rs
@@ -1,5 +1,5 @@
 #![feature(generators)]
-#![feature(optin_builtin_traits)]
+#![feature(auto_traits)]
 #![feature(negative_impls)]
 
 auto trait Foo {}
diff --git a/src/test/ui/issues/issue-29516.rs b/src/test/ui/issues/issue-29516.rs
index 035f904b15b..6779d508dd6 100644
--- a/src/test/ui/issues/issue-29516.rs
+++ b/src/test/ui/issues/issue-29516.rs
@@ -1,5 +1,5 @@
 // check-pass
-#![feature(optin_builtin_traits)]
+#![feature(auto_traits)]
 #![feature(negative_impls)]
 
 auto trait NotSame {}
diff --git a/src/test/ui/never_type/auto-traits.rs b/src/test/ui/never_type/auto-traits.rs
index 84c8db4053e..42ede708e66 100644
--- a/src/test/ui/never_type/auto-traits.rs
+++ b/src/test/ui/never_type/auto-traits.rs
@@ -1,6 +1,6 @@
 // check-pass
 
-#![feature(optin_builtin_traits)]
+#![feature(auto_traits)]
 #![feature(negative_impls)]
 #![feature(never_type)]
 
diff --git a/src/test/ui/parser/trait-object-bad-parens.rs b/src/test/ui/parser/trait-object-bad-parens.rs
index 0a2836d691f..8e267c7448f 100644
--- a/src/test/ui/parser/trait-object-bad-parens.rs
+++ b/src/test/ui/parser/trait-object-bad-parens.rs
@@ -1,4 +1,4 @@
-#![feature(optin_builtin_traits)]
+#![feature(auto_traits)]
 #![feature(negative_impls)]
 #![allow(bare_trait_objects)]
 
diff --git a/src/test/ui/phantom-oibit.rs b/src/test/ui/phantom-oibit.rs
index 04291a70606..14d6f951fa6 100644
--- a/src/test/ui/phantom-oibit.rs
+++ b/src/test/ui/phantom-oibit.rs
@@ -1,7 +1,7 @@
 // Ensure that OIBIT checks `T` when it encounters a `PhantomData<T>` field, instead of checking
 // the `PhantomData<T>` type itself (which almost always implements an auto trait)
 
-#![feature(optin_builtin_traits)]
+#![feature(auto_traits)]
 
 use std::marker::{PhantomData};
 
diff --git a/src/test/ui/privacy/private-in-public-non-principal-2.rs b/src/test/ui/privacy/private-in-public-non-principal-2.rs
index effcb508e27..db451d33429 100644
--- a/src/test/ui/privacy/private-in-public-non-principal-2.rs
+++ b/src/test/ui/privacy/private-in-public-non-principal-2.rs
@@ -1,4 +1,4 @@
-#![feature(optin_builtin_traits)]
+#![feature(auto_traits)]
 #![feature(negative_impls)]
 
 #[allow(private_in_public)]
diff --git a/src/test/ui/privacy/private-in-public-non-principal.rs b/src/test/ui/privacy/private-in-public-non-principal.rs
index aa946f5c0ac..ac1d5a9e6a2 100644
--- a/src/test/ui/privacy/private-in-public-non-principal.rs
+++ b/src/test/ui/privacy/private-in-public-non-principal.rs
@@ -1,4 +1,4 @@
-#![feature(optin_builtin_traits)]
+#![feature(auto_traits)]
 #![feature(negative_impls)]
 
 pub trait PubPrincipal {}
diff --git a/src/test/ui/specialization/specialization-polarity.rs b/src/test/ui/specialization/specialization-polarity.rs
index 17897d8b803..b3cd8255bb9 100644
--- a/src/test/ui/specialization/specialization-polarity.rs
+++ b/src/test/ui/specialization/specialization-polarity.rs
@@ -1,6 +1,6 @@
 // Make sure specialization cannot change impl polarity
 
-#![feature(optin_builtin_traits)]
+#![feature(auto_traits)]
 #![feature(negative_impls)]
 #![feature(specialization)] //~ WARN the feature `specialization` is incomplete
 
diff --git a/src/test/ui/symbol-names/impl1.rs b/src/test/ui/symbol-names/impl1.rs
index 1ada54cc102..05bd98df006 100644
--- a/src/test/ui/symbol-names/impl1.rs
+++ b/src/test/ui/symbol-names/impl1.rs
@@ -6,7 +6,7 @@
 //[legacy]normalize-stderr-32bit: "hee444285569b39c2" -> "SYMBOL_HASH"
 //[legacy]normalize-stderr-64bit: "h310ea0259fc3d32d" -> "SYMBOL_HASH"
 
-#![feature(optin_builtin_traits, rustc_attrs)]
+#![feature(auto_traits, rustc_attrs)]
 #![allow(dead_code)]
 
 mod foo {
diff --git a/src/test/ui/traits/traits-inductive-overflow-supertrait-oibit.rs b/src/test/ui/traits/traits-inductive-overflow-supertrait-oibit.rs
index 571f934fc5b..21f299505cc 100644
--- a/src/test/ui/traits/traits-inductive-overflow-supertrait-oibit.rs
+++ b/src/test/ui/traits/traits-inductive-overflow-supertrait-oibit.rs
@@ -2,7 +2,7 @@
 // a simple OIBIT `..` impl alone still doesn't allow arbitrary bounds
 // to be synthesized.
 
-#![feature(optin_builtin_traits)]
+#![feature(auto_traits)]
 #![feature(negative_impls)]
 
 auto trait Magic: Copy {} //~ ERROR E0568
diff --git a/src/test/ui/typeck/auxiliary/tdticc_coherence_lib.rs b/src/test/ui/typeck/auxiliary/tdticc_coherence_lib.rs
index d00025b7708..ef2cd415fca 100644
--- a/src/test/ui/typeck/auxiliary/tdticc_coherence_lib.rs
+++ b/src/test/ui/typeck/auxiliary/tdticc_coherence_lib.rs
@@ -1,4 +1,4 @@
-#![feature(optin_builtin_traits, core)]
+#![feature(auto_traits, core)]
 #![crate_type = "rlib"]
 
 pub auto trait DefaultedTrait { }