Auto merge of #67136 - oli-obk:const_stability, r=Centril

Require stable/unstable annotations for the constness of all stable fns with a const modifier

r? @RalfJung @Centril

Every `#[stable]` const fn now needs either a `#[rustc_const_unstable]` attribute or a `#[rustc_const_stable]` attribute. You can't silently stabilize the constness of a function anymore.

22 files changed, 57 insertions, 62 deletions

diff --git a/src/test/ui/consts/auxiliary/promotable_const_fn_lib.rs b/src/test/ui/consts/auxiliary/promotable_const_fn_lib.rs
index e54cbb09804..b1d5440b41a 100644
--- a/src/test/ui/consts/auxiliary/promotable_const_fn_lib.rs
+++ b/src/test/ui/consts/auxiliary/promotable_const_fn_lib.rs
@@ -7,6 +7,7 @@
 
 #[rustc_promotable]
 #[stable(since="1.0.0", feature = "mep")]
+#[rustc_const_stable(since="1.0.0", feature = "mep")]
 #[inline]
 pub const fn foo() -> usize { 22 }
 
@@ -15,6 +16,7 @@ pub struct Foo(usize);
 
 impl Foo {
     #[stable(since="1.0.0", feature = "mep")]
+    #[rustc_const_stable(feature = "mep", since = "1.0.0")]
     #[inline]
     #[rustc_promotable]
     pub const fn foo() -> usize { 22 }
diff --git a/src/test/ui/consts/const-eval/auxiliary/stability.rs b/src/test/ui/consts/const-eval/auxiliary/stability.rs
index 5551d35bcc8..830db55207f 100644
--- a/src/test/ui/consts/const-eval/auxiliary/stability.rs
+++ b/src/test/ui/consts/const-eval/auxiliary/stability.rs
@@ -3,9 +3,9 @@
 #![crate_type="rlib"]
 #![stable(feature = "rust1", since = "1.0.0")]
 
-#![feature(rustc_const_unstable, const_fn)]
+#![feature(const_fn)]
 #![feature(staged_api)]
 
 #[stable(feature = "rust1", since = "1.0.0")]
-#[rustc_const_unstable(feature="foo")]
+#[rustc_const_unstable(feature="foo", issue = "0")]
 pub const fn foo() -> u32 { 42 }
diff --git a/src/test/ui/consts/const-eval/dont_promote_unstable_const_fn.rs b/src/test/ui/consts/const-eval/dont_promote_unstable_const_fn.rs
index 90028690990..c4b89b50bc4 100644
--- a/src/test/ui/consts/const-eval/dont_promote_unstable_const_fn.rs
+++ b/src/test/ui/consts/const-eval/dont_promote_unstable_const_fn.rs
@@ -3,11 +3,11 @@
             we're apparently really bad at it",
             issue = "0")]
 
-#![feature(rustc_const_unstable, const_fn)]
+#![feature(const_fn)]
 #![feature(staged_api)]
 
 #[stable(feature = "rust1", since = "1.0.0")]
-#[rustc_const_unstable(feature="foo")]
+#[rustc_const_unstable(feature="foo", issue = "0")]
 const fn foo() -> u32 { 42 }
 
 fn meh() -> u32 { 42 }
diff --git a/src/test/ui/consts/min_const_fn/allow_const_fn_ptr.rs b/src/test/ui/consts/min_const_fn/allow_const_fn_ptr.rs
index 3992607c387..937aae1a8e3 100644
--- a/src/test/ui/consts/min_const_fn/allow_const_fn_ptr.rs
+++ b/src/test/ui/consts/min_const_fn/allow_const_fn_ptr.rs
@@ -1,10 +1,12 @@
 #![feature(rustc_attrs, staged_api)]
 
 #[stable(feature = "rust1", since = "1.0.0")]
+#[rustc_const_stable(since="1.0.0", feature = "mep")]
 const fn error(_: fn()) {} //~ ERROR function pointers in const fn are unstable
 
 #[stable(feature = "rust1", since = "1.0.0")]
 #[rustc_allow_const_fn_ptr]
+#[rustc_const_stable(since="1.0.0", feature = "mep")]
 const fn compiles(_: fn()) {}
 
 fn main() {}
diff --git a/src/test/ui/consts/min_const_fn/allow_const_fn_ptr.stderr b/src/test/ui/consts/min_const_fn/allow_const_fn_ptr.stderr
index 6228b012dde..0ede4229ade 100644
--- a/src/test/ui/consts/min_const_fn/allow_const_fn_ptr.stderr
+++ b/src/test/ui/consts/min_const_fn/allow_const_fn_ptr.stderr
@@ -1,5 +1,5 @@
 error[E0723]: function pointers in const fn are unstable
-  --> $DIR/allow_const_fn_ptr.rs:4:16
+  --> $DIR/allow_const_fn_ptr.rs:5:16
    |
 LL | const fn error(_: fn()) {}
    |                ^
diff --git a/src/test/ui/consts/min_const_fn/allow_const_fn_ptr_run_pass.rs b/src/test/ui/consts/min_const_fn/allow_const_fn_ptr_run_pass.rs
index 1d8b95ab1a2..7aa9bd7e2dc 100644
--- a/src/test/ui/consts/min_const_fn/allow_const_fn_ptr_run_pass.rs
+++ b/src/test/ui/consts/min_const_fn/allow_const_fn_ptr_run_pass.rs
@@ -5,6 +5,7 @@
 
 #[stable(feature = "rust1", since = "1.0.0")]
 #[rustc_allow_const_fn_ptr]
+#[rustc_const_stable(since="1.0.0", feature = "mep")]
 const fn takes_fn_ptr(_: fn()) {}
 
 const FN: fn() = || ();
diff --git a/src/test/ui/consts/min_const_fn/min_const_fn_libstd_stability.rs b/src/test/ui/consts/min_const_fn/min_const_fn_libstd_stability.rs
index 759d9ab6a40..97e467aece2 100644
--- a/src/test/ui/consts/min_const_fn/min_const_fn_libstd_stability.rs
+++ b/src/test/ui/consts/min_const_fn/min_const_fn_libstd_stability.rs
@@ -3,14 +3,15 @@
             we're apparently really bad at it",
             issue = "0")]
 
-#![feature(rustc_const_unstable, const_fn, foo, foo2)]
+#![feature(const_fn, foo, foo2)]
 #![feature(staged_api)]
 
 #[stable(feature = "rust1", since = "1.0.0")]
-#[rustc_const_unstable(feature="foo")]
+#[rustc_const_unstable(feature="foo", issue = "0")]
 const fn foo() -> u32 { 42 }
 
 #[stable(feature = "rust1", since = "1.0.0")]
+#[rustc_const_stable(feature = "rust1", since = "1.0.0")]
 // can't call non-min_const_fn
 const fn bar() -> u32 { foo() } //~ ERROR can only call other `const fn`
 
@@ -18,10 +19,12 @@ const fn bar() -> u32 { foo() } //~ ERROR can only call other `const fn`
 const fn foo2() -> u32 { 42 }
 
 #[stable(feature = "rust1", since = "1.0.0")]
+#[rustc_const_stable(feature = "rust1", since = "1.0.0")]
 // can't call non-min_const_fn
 const fn bar2() -> u32 { foo2() } //~ ERROR can only call other `const fn`
 
 #[stable(feature = "rust1", since = "1.0.0")]
+#[rustc_const_stable(feature = "rust1", since = "1.0.0")]
 // conformity is required, even with `const_fn` feature gate
 const fn bar3() -> u32 { (5f32 + 6f32) as u32 } //~ ERROR only int, `bool` and `char` operations
 
@@ -30,6 +33,7 @@ const fn bar3() -> u32 { (5f32 + 6f32) as u32 } //~ ERROR only int, `bool` and `
 const fn foo2_gated() -> u32 { 42 }
 
 #[stable(feature = "rust1", since = "1.0.0")]
+#[rustc_const_stable(feature = "rust1", since = "1.0.0")]
 // can't call non-min_const_fn
 const fn bar2_gated() -> u32 { foo2_gated() } //~ ERROR can only call other `const fn`
 
diff --git a/src/test/ui/consts/min_const_fn/min_const_fn_libstd_stability.stderr b/src/test/ui/consts/min_const_fn/min_const_fn_libstd_stability.stderr
index 0af5bdca815..1da9b41aa59 100644
--- a/src/test/ui/consts/min_const_fn/min_const_fn_libstd_stability.stderr
+++ b/src/test/ui/consts/min_const_fn/min_const_fn_libstd_stability.stderr
@@ -1,5 +1,5 @@
 error[E0723]: can only call other `const fn` within a `const fn`, but `const foo` is not stable as `const fn`
-  --> $DIR/min_const_fn_libstd_stability.rs:15:25
+  --> $DIR/min_const_fn_libstd_stability.rs:16:25
    |
 LL | const fn bar() -> u32 { foo() }
    |                         ^^^^^
@@ -8,7 +8,7 @@ LL | const fn bar() -> u32 { foo() }
    = help: add `#![feature(const_fn)]` to the crate attributes to enable
 
 error[E0723]: can only call other `const fn` within a `const fn`, but `const foo2` is not stable as `const fn`
-  --> $DIR/min_const_fn_libstd_stability.rs:22:26
+  --> $DIR/min_const_fn_libstd_stability.rs:24:26
    |
 LL | const fn bar2() -> u32 { foo2() }
    |                          ^^^^^^
@@ -17,7 +17,7 @@ LL | const fn bar2() -> u32 { foo2() }
    = help: add `#![feature(const_fn)]` to the crate attributes to enable
 
 error[E0723]: only int, `bool` and `char` operations are stable in const fn
-  --> $DIR/min_const_fn_libstd_stability.rs:26:26
+  --> $DIR/min_const_fn_libstd_stability.rs:29:26
    |
 LL | const fn bar3() -> u32 { (5f32 + 6f32) as u32 }
    |                          ^^^^^^^^^^^^^
@@ -26,7 +26,7 @@ LL | const fn bar3() -> u32 { (5f32 + 6f32) as u32 }
    = help: add `#![feature(const_fn)]` to the crate attributes to enable
 
 error[E0723]: can only call other `const fn` within a `const fn`, but `const foo2_gated` is not stable as `const fn`
-  --> $DIR/min_const_fn_libstd_stability.rs:34:32
+  --> $DIR/min_const_fn_libstd_stability.rs:38:32
    |
 LL | const fn bar2_gated() -> u32 { foo2_gated() }
    |                                ^^^^^^^^^^^^
diff --git a/src/test/ui/consts/min_const_fn/min_const_unsafe_fn_libstd_stability.rs b/src/test/ui/consts/min_const_fn/min_const_unsafe_fn_libstd_stability.rs
index 64057b012b8..102b3801441 100644
--- a/src/test/ui/consts/min_const_fn/min_const_unsafe_fn_libstd_stability.rs
+++ b/src/test/ui/consts/min_const_fn/min_const_unsafe_fn_libstd_stability.rs
@@ -3,14 +3,15 @@
             we're apparently really bad at it",
             issue = "0")]
 
-#![feature(rustc_const_unstable, const_fn, foo, foo2)]
+#![feature(const_fn, foo, foo2)]
 #![feature(staged_api)]
 
 #[stable(feature = "rust1", since = "1.0.0")]
-#[rustc_const_unstable(feature="foo")]
+#[rustc_const_unstable(feature="foo", issue = "0")]
 const unsafe fn foo() -> u32 { 42 }
 
 #[stable(feature = "rust1", since = "1.0.0")]
+#[rustc_const_stable(feature = "rust1", since = "1.0.0")]
 // can't call non-min_const_fn
 const unsafe fn bar() -> u32 { unsafe { foo() } } //~ ERROR can only call other `const fn`
 
@@ -18,10 +19,12 @@ const unsafe fn bar() -> u32 { unsafe { foo() } } //~ ERROR can only call other
 const unsafe fn foo2() -> u32 { 42 }
 
 #[stable(feature = "rust1", since = "1.0.0")]
+#[rustc_const_stable(feature = "rust1", since = "1.0.0")]
 // can't call non-min_const_fn
 const unsafe fn bar2() -> u32 { unsafe { foo2() } } //~ ERROR can only call other `const fn`
 
 #[stable(feature = "rust1", since = "1.0.0")]
+#[rustc_const_stable(feature = "rust1", since = "1.0.0")]
 // conformity is required, even with `const_fn` feature gate
 const unsafe fn bar3() -> u32 { (5f32 + 6f32) as u32 } //~ ERROR only int, `bool` and `char` op
 
@@ -30,6 +33,7 @@ const unsafe fn bar3() -> u32 { (5f32 + 6f32) as u32 } //~ ERROR only int, `bool
 const unsafe fn foo2_gated() -> u32 { 42 }
 
 #[stable(feature = "rust1", since = "1.0.0")]
+#[rustc_const_stable(feature = "rust1", since = "1.0.0")]
 // can't call non-min_const_fn
 const unsafe fn bar2_gated() -> u32 { unsafe { foo2_gated() } }
 //~^ ERROR can only call other `const fn`
diff --git a/src/test/ui/consts/min_const_fn/min_const_unsafe_fn_libstd_stability.stderr b/src/test/ui/consts/min_const_fn/min_const_unsafe_fn_libstd_stability.stderr
index bc6f8c59606..ae92602d45f 100644
--- a/src/test/ui/consts/min_const_fn/min_const_unsafe_fn_libstd_stability.stderr
+++ b/src/test/ui/consts/min_const_fn/min_const_unsafe_fn_libstd_stability.stderr
@@ -1,5 +1,5 @@
 error[E0723]: can only call other `const fn` within a `const fn`, but `const foo` is not stable as `const fn`
-  --> $DIR/min_const_unsafe_fn_libstd_stability.rs:15:41
+  --> $DIR/min_const_unsafe_fn_libstd_stability.rs:16:41
    |
 LL | const unsafe fn bar() -> u32 { unsafe { foo() } }
    |                                         ^^^^^
@@ -8,7 +8,7 @@ LL | const unsafe fn bar() -> u32 { unsafe { foo() } }
    = help: add `#![feature(const_fn)]` to the crate attributes to enable
 
 error[E0723]: can only call other `const fn` within a `const fn`, but `const foo2` is not stable as `const fn`
-  --> $DIR/min_const_unsafe_fn_libstd_stability.rs:22:42
+  --> $DIR/min_const_unsafe_fn_libstd_stability.rs:24:42
    |
 LL | const unsafe fn bar2() -> u32 { unsafe { foo2() } }
    |                                          ^^^^^^
@@ -17,7 +17,7 @@ LL | const unsafe fn bar2() -> u32 { unsafe { foo2() } }
    = help: add `#![feature(const_fn)]` to the crate attributes to enable
 
 error[E0723]: only int, `bool` and `char` operations are stable in const fn
-  --> $DIR/min_const_unsafe_fn_libstd_stability.rs:26:33
+  --> $DIR/min_const_unsafe_fn_libstd_stability.rs:29:33
    |
 LL | const unsafe fn bar3() -> u32 { (5f32 + 6f32) as u32 }
    |                                 ^^^^^^^^^^^^^
@@ -26,7 +26,7 @@ LL | const unsafe fn bar3() -> u32 { (5f32 + 6f32) as u32 }
    = help: add `#![feature(const_fn)]` to the crate attributes to enable
 
 error[E0723]: can only call other `const fn` within a `const fn`, but `const foo2_gated` is not stable as `const fn`
-  --> $DIR/min_const_unsafe_fn_libstd_stability.rs:34:48
+  --> $DIR/min_const_unsafe_fn_libstd_stability.rs:38:48
    |
 LL | const unsafe fn bar2_gated() -> u32 { unsafe { foo2_gated() } }
    |                                                ^^^^^^^^^^^^
diff --git a/src/test/ui/consts/min_const_fn/min_const_unsafe_fn_libstd_stability2.rs b/src/test/ui/consts/min_const_fn/min_const_unsafe_fn_libstd_stability2.rs
index deb2cb6b619..121177f8366 100644
--- a/src/test/ui/consts/min_const_fn/min_const_unsafe_fn_libstd_stability2.rs
+++ b/src/test/ui/consts/min_const_fn/min_const_unsafe_fn_libstd_stability2.rs
@@ -3,14 +3,15 @@
             we're apparently really bad at it",
             issue = "0")]
 
-#![feature(rustc_const_unstable, const_fn, foo, foo2)]
+#![feature(const_fn, foo, foo2)]
 #![feature(staged_api)]
 
 #[stable(feature = "rust1", since = "1.0.0")]
-#[rustc_const_unstable(feature="foo")]
+#[rustc_const_unstable(feature="foo", issue = "0")]
 const fn foo() -> u32 { 42 }
 
 #[stable(feature = "rust1", since = "1.0.0")]
+#[rustc_const_stable(feature = "rust1", since = "1.0.0")]
 // can't call non-min_const_fn
 const unsafe fn bar() -> u32 { foo() } //~ ERROR can only call other `const fn`
 
@@ -18,6 +19,7 @@ const unsafe fn bar() -> u32 { foo() } //~ ERROR can only call other `const fn`
 const fn foo2() -> u32 { 42 }
 
 #[stable(feature = "rust1", since = "1.0.0")]
+#[rustc_const_stable(feature = "rust1", since = "1.0.0")]
 // can't call non-min_const_fn
 const unsafe fn bar2() -> u32 { foo2() } //~ ERROR can only call other `const fn`
 
@@ -26,6 +28,7 @@ const unsafe fn bar2() -> u32 { foo2() } //~ ERROR can only call other `const fn
 const fn foo2_gated() -> u32 { 42 }
 
 #[stable(feature = "rust1", since = "1.0.0")]
+#[rustc_const_stable(feature = "rust1", since = "1.0.0")]
 // can't call non-min_const_fn
 const unsafe fn bar2_gated() -> u32 { foo2_gated() } //~ ERROR can only call other `const fn`
 
diff --git a/src/test/ui/consts/min_const_fn/min_const_unsafe_fn_libstd_stability2.stderr b/src/test/ui/consts/min_const_fn/min_const_unsafe_fn_libstd_stability2.stderr
index a14fd740c67..a0db74cfad6 100644
--- a/src/test/ui/consts/min_const_fn/min_const_unsafe_fn_libstd_stability2.stderr
+++ b/src/test/ui/consts/min_const_fn/min_const_unsafe_fn_libstd_stability2.stderr
@@ -1,5 +1,5 @@
 error[E0723]: can only call other `const fn` within a `const fn`, but `const foo` is not stable as `const fn`
-  --> $DIR/min_const_unsafe_fn_libstd_stability2.rs:15:32
+  --> $DIR/min_const_unsafe_fn_libstd_stability2.rs:16:32
    |
 LL | const unsafe fn bar() -> u32 { foo() }
    |                                ^^^^^
@@ -8,7 +8,7 @@ LL | const unsafe fn bar() -> u32 { foo() }
    = help: add `#![feature(const_fn)]` to the crate attributes to enable
 
 error[E0723]: can only call other `const fn` within a `const fn`, but `const foo2` is not stable as `const fn`
-  --> $DIR/min_const_unsafe_fn_libstd_stability2.rs:22:33
+  --> $DIR/min_const_unsafe_fn_libstd_stability2.rs:24:33
    |
 LL | const unsafe fn bar2() -> u32 { foo2() }
    |                                 ^^^^^^
@@ -17,7 +17,7 @@ LL | const unsafe fn bar2() -> u32 { foo2() }
    = help: add `#![feature(const_fn)]` to the crate attributes to enable
 
 error[E0723]: can only call other `const fn` within a `const fn`, but `const foo2_gated` is not stable as `const fn`
-  --> $DIR/min_const_unsafe_fn_libstd_stability2.rs:30:39
+  --> $DIR/min_const_unsafe_fn_libstd_stability2.rs:33:39
    |
 LL | const unsafe fn bar2_gated() -> u32 { foo2_gated() }
    |                                       ^^^^^^^^^^^^
diff --git a/src/test/ui/consts/unstable-const-fn-in-libcore.rs b/src/test/ui/consts/unstable-const-fn-in-libcore.rs
index cad1516fc78..655ad7b548a 100644
--- a/src/test/ui/consts/unstable-const-fn-in-libcore.rs
+++ b/src/test/ui/consts/unstable-const-fn-in-libcore.rs
@@ -14,7 +14,7 @@ enum Opt<T> {
 }
 
 impl<T> Opt<T> {
-    #[rustc_const_unstable(feature = "foo")]
+    #[rustc_const_unstable(feature = "foo", issue = "0")]
     #[stable(feature = "rust1", since = "1.0.0")]
     const fn unwrap_or_else<F: FnOnce() -> T>(self, f: F) -> T {
     //~^ ERROR destructors cannot be evaluated at compile-time
diff --git a/src/test/ui/feature-gate/allow-features-empty.rs b/src/test/ui/feature-gate/allow-features-empty.rs
index 641e4b852e7..88a60934927 100644
--- a/src/test/ui/feature-gate/allow-features-empty.rs
+++ b/src/test/ui/feature-gate/allow-features-empty.rs
@@ -1,8 +1,6 @@
 // compile-flags: -Z allow_features=
 // Note: This test uses rustc internal flags because they will never stabilize.
 
-#![feature(rustc_const_unstable)] //~ ERROR
-
 #![feature(lang_items)] //~ ERROR
 
 #![feature(unknown_stdlib_feature)] //~ ERROR
diff --git a/src/test/ui/feature-gate/allow-features-empty.stderr b/src/test/ui/feature-gate/allow-features-empty.stderr
index a87d1058503..f88b3ea0a60 100644
--- a/src/test/ui/feature-gate/allow-features-empty.stderr
+++ b/src/test/ui/feature-gate/allow-features-empty.stderr
@@ -1,21 +1,15 @@
-error[E0725]: the feature `rustc_const_unstable` is not in the list of allowed features
-  --> $DIR/allow-features-empty.rs:4:12
-   |
-LL | #![feature(rustc_const_unstable)]
-   |            ^^^^^^^^^^^^^^^^^^^^
-
 error[E0725]: the feature `lang_items` is not in the list of allowed features
-  --> $DIR/allow-features-empty.rs:6:12
+  --> $DIR/allow-features-empty.rs:4:12
    |
 LL | #![feature(lang_items)]
    |            ^^^^^^^^^^
 
 error[E0725]: the feature `unknown_stdlib_feature` is not in the list of allowed features
-  --> $DIR/allow-features-empty.rs:8:12
+  --> $DIR/allow-features-empty.rs:6:12
    |
 LL | #![feature(unknown_stdlib_feature)]
    |            ^^^^^^^^^^^^^^^^^^^^^^
 
-error: aborting due to 3 previous errors
+error: aborting due to 2 previous errors
 
 For more information about this error, try `rustc --explain E0725`.
diff --git a/src/test/ui/feature-gate/allow-features.rs b/src/test/ui/feature-gate/allow-features.rs
index de69e48a65f..2ce4701a818 100644
--- a/src/test/ui/feature-gate/allow-features.rs
+++ b/src/test/ui/feature-gate/allow-features.rs
@@ -1,8 +1,6 @@
 // compile-flags: -Z allow_features=lang_items
 // Note: This test uses rustc internal flags because they will never stabilize.
 
-#![feature(rustc_const_unstable)] //~ ERROR
-
 #![feature(lang_items)]
 
 #![feature(unknown_stdlib_feature)] //~ ERROR
diff --git a/src/test/ui/feature-gate/allow-features.stderr b/src/test/ui/feature-gate/allow-features.stderr
index 157dddf06ad..9caf48dd138 100644
--- a/src/test/ui/feature-gate/allow-features.stderr
+++ b/src/test/ui/feature-gate/allow-features.stderr
@@ -1,15 +1,9 @@
-error[E0725]: the feature `rustc_const_unstable` is not in the list of allowed features
-  --> $DIR/allow-features.rs:4:12
-   |
-LL | #![feature(rustc_const_unstable)]
-   |            ^^^^^^^^^^^^^^^^^^^^
-
 error[E0725]: the feature `unknown_stdlib_feature` is not in the list of allowed features
-  --> $DIR/allow-features.rs:8:12
+  --> $DIR/allow-features.rs:6:12
    |
 LL | #![feature(unknown_stdlib_feature)]
    |            ^^^^^^^^^^^^^^^^^^^^^^
 
-error: aborting due to 2 previous errors
+error: aborting due to previous error
 
 For more information about this error, try `rustc --explain E0725`.
diff --git a/src/test/ui/feature-gates/feature-gate-rustc_const_unstable.rs b/src/test/ui/feature-gates/feature-gate-rustc_const_unstable.rs
index 6961e68744f..3296a17a0b7 100644
--- a/src/test/ui/feature-gates/feature-gate-rustc_const_unstable.rs
+++ b/src/test/ui/feature-gates/feature-gate-rustc_const_unstable.rs
@@ -1,11 +1,8 @@
 // Test internal const fn feature gate.
 
-#![feature(staged_api)]
 #![feature(const_fn)]
-//#![feature(rustc_const_unstable)]
 
-#[stable(feature="zing", since="1.0.0")]
-#[rustc_const_unstable(feature="fzzzzzt")] //~ERROR internal feature
+#[rustc_const_unstable(feature="fzzzzzt")] //~ stability attributes may not be used outside
 pub const fn bazinga() {}
 
 fn main() {
diff --git a/src/test/ui/feature-gates/feature-gate-rustc_const_unstable.stderr b/src/test/ui/feature-gates/feature-gate-rustc_const_unstable.stderr
index d7b7cf72a26..9df926dcf90 100644
--- a/src/test/ui/feature-gates/feature-gate-rustc_const_unstable.stderr
+++ b/src/test/ui/feature-gates/feature-gate-rustc_const_unstable.stderr
@@ -1,11 +1,9 @@
-error[E0658]: the `#[rustc_const_unstable]` attribute is an internal feature
-  --> $DIR/feature-gate-rustc_const_unstable.rs:8:1
+error[E0734]: stability attributes may not be used outside of the standard library
+  --> $DIR/feature-gate-rustc_const_unstable.rs:5:1
    |
 LL | #[rustc_const_unstable(feature="fzzzzzt")]
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
-   |
-   = help: add `#![feature(rustc_const_unstable)]` to the crate attributes to enable
 
 error: aborting due to previous error
 
-For more information about this error, try `rustc --explain E0658`.
+For more information about this error, try `rustc --explain E0734`.
diff --git a/src/test/ui/invalid_const_promotion.rs b/src/test/ui/invalid_const_promotion.rs
index 91115ef74b8..5d7664cefb3 100644
--- a/src/test/ui/invalid_const_promotion.rs
+++ b/src/test/ui/invalid_const_promotion.rs
@@ -22,6 +22,7 @@ use std::process::{Command, Stdio};
 // of the const fn kicks in, causing a different code path in the
 // compiler to be executed (see PR #66294).
 #[stable(feature = "rustc", since = "1.0.0")]
+#[rustc_const_stable(feature = "rustc", since = "1.0.0")]
 #[rustc_promotable]
 const fn bar(_: bool) -> usize { 0 - 1 }
 
diff --git a/src/test/ui/stability-attribute/stability-attribute-sanity.rs b/src/test/ui/stability-attribute/stability-attribute-sanity.rs
index 38421e2e6ef..2e3d790d2d8 100644
--- a/src/test/ui/stability-attribute/stability-attribute-sanity.rs
+++ b/src/test/ui/stability-attribute/stability-attribute-sanity.rs
@@ -1,6 +1,6 @@
 // Various checks that stability attributes are used correctly, per RFC 507
 
-#![feature(const_fn, staged_api, rustc_const_unstable)]
+#![feature(const_fn, staged_api)]
 
 #![stable(feature = "rust1", since = "1.0.0")]
 
@@ -60,11 +60,10 @@ fn multiple3() { }
 #[stable(feature = "a", since = "b")]
 #[rustc_deprecated(since = "b", reason = "text")]
 #[rustc_deprecated(since = "b", reason = "text")]
-#[rustc_const_unstable(feature = "c")]
-#[rustc_const_unstable(feature = "d")]
+#[rustc_const_unstable(feature = "c", issue = "0")]
+#[rustc_const_unstable(feature = "d", issue = "0")] //~ ERROR multiple stability levels
 pub const fn multiple4() { } //~ ERROR multiple rustc_deprecated attributes [E0540]
 //~^ ERROR Invalid stability or deprecation version found
-//~| ERROR multiple rustc_const_unstable attributes
 
 #[rustc_deprecated(since = "a", reason = "text")]
 fn deprecated_without_unstable_or_stable() { }
diff --git a/src/test/ui/stability-attribute/stability-attribute-sanity.stderr b/src/test/ui/stability-attribute/stability-attribute-sanity.stderr
index 4b7ec821f45..552e078f45f 100644
--- a/src/test/ui/stability-attribute/stability-attribute-sanity.stderr
+++ b/src/test/ui/stability-attribute/stability-attribute-sanity.stderr
@@ -88,11 +88,11 @@ error[E0540]: multiple rustc_deprecated attributes
 LL | pub const fn multiple4() { }
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
-error[E0553]: multiple rustc_const_unstable attributes
-  --> $DIR/stability-attribute-sanity.rs:65:1
+error[E0544]: multiple stability levels
+  --> $DIR/stability-attribute-sanity.rs:64:1
    |
-LL | pub const fn multiple4() { }
-   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+LL | #[rustc_const_unstable(feature = "d", issue = "0")]
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 error: Invalid stability or deprecation version found
   --> $DIR/stability-attribute-sanity.rs:65:1
@@ -101,7 +101,7 @@ LL | pub const fn multiple4() { }
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 error[E0549]: rustc_deprecated attribute must be paired with either stable or unstable attribute
-  --> $DIR/stability-attribute-sanity.rs:70:1
+  --> $DIR/stability-attribute-sanity.rs:69:1
    |
 LL | fn deprecated_without_unstable_or_stable() { }
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^