Don't mark `ineffective_unstable_trait_impl` as an internal lint

It's not an internal lint:
- It's not in the rustc::internal lint group
- It's on unconditionally, because it actually lints `staged_api`, not
  the compiler

This fixes a bug where `#[deny(rustc::internal)]` would warn that
`rustc::internal` was an unknown lint.

compiler/rustc_lint_defs/src/builtin.rs

@@ -4,7 +4,7 @@
 //! compiler code, rather than using their own custom pass. Those
 //! lints are all available in `rustc_lint::builtin`.
 
-use crate::{declare_lint, declare_lint_pass, declare_tool_lint};
+use crate::{declare_lint, declare_lint_pass};
 use rustc_span::edition::Edition;
 use rustc_span::symbol::sym;
 
@@ -2825,8 +2825,29 @@ declare_lint! {
     };
 }
 
-declare_tool_lint! {
-    pub rustc::INEFFECTIVE_UNSTABLE_TRAIT_IMPL,
+declare_lint! {
+    /// The `ineffective_unstable_trait_impl` lint detects `#[unstable]` attributes which are not used.
+    ///
+    /// ### Example
+    ///
+    /// ```compile_fail
+    /// #![feature(staged_api)]
+    ///
+    /// #[derive(Clone)]
+    /// #[stable(feature = "x", since = "1")]
+    /// struct S {}
+    ///
+    /// #[unstable(feature = "y", issue = "none")]
+    /// impl Copy for S {}
+    /// ```
+    ///
+    /// {{produces}}
+    ///
+    /// ### Explanation
+    ///
+    /// `staged_api` does not currently support using a stability attribute on `impl` blocks.
+    /// `impl`s are always stable if both the type and trait are stable, and always unstable otherwise.
+    pub INEFFECTIVE_UNSTABLE_TRAIT_IMPL,
     Deny,
     "detects `#[unstable]` on stable trait implementations for stable types"
 }

library/alloc/src/task.rs

@@ -33,7 +33,8 @@ pub trait Wake {
     }
 }
 
-#[allow(rustc::ineffective_unstable_trait_impl)]
+#[cfg_attr(bootstrap, allow(rustc::ineffective_unstable_trait_impl))]
+#[cfg_attr(not(bootstrap), allow(ineffective_unstable_trait_impl))]
 #[unstable(feature = "wake_trait", issue = "69912")]
 impl<W: Wake + Send + Sync + 'static> From<Arc<W>> for Waker {
     fn from(waker: Arc<W>) -> Waker {
@@ -43,7 +44,8 @@ impl<W: Wake + Send + Sync + 'static> From<Arc<W>> for Waker {
     }
 }
 
-#[allow(rustc::ineffective_unstable_trait_impl)]
+#[cfg_attr(bootstrap, allow(rustc::ineffective_unstable_trait_impl))]
+#[cfg_attr(not(bootstrap), allow(ineffective_unstable_trait_impl))]
 #[unstable(feature = "wake_trait", issue = "69912")]
 impl<W: Wake + Send + Sync + 'static> From<Arc<W>> for RawWaker {
     fn from(waker: Arc<W>) -> RawWaker {

src/test/ui/stability-attribute/stability-attribute-trait-impl.rs

@@ -22,7 +22,7 @@ impl StableTrait for UnstableType {}
 impl UnstableTrait for StableType {}
 
 #[unstable(feature = "x", issue = "none")]
-//~^ ERROR an `#[unstable]` annotation here has no effect [rustc::ineffective_unstable_trait_impl]
+//~^ ERROR an `#[unstable]` annotation here has no effect [ineffective_unstable_trait_impl]
 impl StableTrait for StableType {}
 
 fn main() {}

src/test/ui/stability-attribute/stability-attribute-trait-impl.stderr

@@ -4,7 +4,7 @@ error: an `#[unstable]` annotation here has no effect
 LL | #[unstable(feature = "x", issue = "none")]
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    |
-   = note: `#[deny(rustc::ineffective_unstable_trait_impl)]` on by default
+   = note: `#[deny(ineffective_unstable_trait_impl)]` on by default
    = note: see issue #55436 <https://github.com/rust-lang/rust/issues/55436> for more information
 
 error: aborting due to previous error