Rollup merge of #136688 - fee1-dead-contrib:push-nppsusmpokqo, r=compiler-errors

require trait impls to have matching const stabilities as the traits

This resolves https://github.com/rust-lang/project-const-traits/issues/5 by implementing the suggested solution in the given thread

r? ``@RalfJung``
cc ``@rust-lang/project-const-traits``

2 files changed, 100 insertions, 1 deletions

diff --git a/tests/ui/traits/const-traits/staged-api.rs b/tests/ui/traits/const-traits/staged-api.rs
index 9a030dafd6b..8dd7226fc29 100644
--- a/tests/ui/traits/const-traits/staged-api.rs
+++ b/tests/ui/traits/const-traits/staged-api.rs
@@ -85,4 +85,36 @@ const fn implicitly_stable_const_context() {
     //~^ ERROR cannot use `#[feature(const_trait_impl)]`
 }
 
+// check that const stability of impls and traits must match
+#[const_trait]
+#[rustc_const_unstable(feature = "beef", issue = "none")]
+trait U {}
+
+#[const_trait]
+#[rustc_const_stable(since = "0.0.0", feature = "beef2")]
+trait S {}
+
+// implied stable
+impl const U for u8 {}
+//~^ const stability on the impl does not match the const stability on the trait
+
+#[rustc_const_stable(since = "0.0.0", feature = "beef2")]
+impl const U for u16 {}
+//~^ const stability on the impl does not match the const stability on the trait
+//~| trait implementations cannot be const stable yet
+
+#[rustc_const_unstable(feature = "beef", issue = "none")]
+impl const U for u32 {}
+
+// implied stable
+impl const S for u8 {}
+
+#[rustc_const_stable(since = "0.0.0", feature = "beef2")]
+impl const S for u16 {}
+//~^ trait implementations cannot be const stable yet
+
+#[rustc_const_unstable(feature = "beef", issue = "none")]
+impl const S for u32 {}
+//~^ const stability on the impl does not match the const stability on the trait
+
 fn main() {}
diff --git a/tests/ui/traits/const-traits/staged-api.stderr b/tests/ui/traits/const-traits/staged-api.stderr
index a7a7a1ee721..cdf577287ee 100644
--- a/tests/ui/traits/const-traits/staged-api.stderr
+++ b/tests/ui/traits/const-traits/staged-api.stderr
@@ -1,3 +1,70 @@
+error: const stability on the impl does not match the const stability on the trait
+  --> $DIR/staged-api.rs:98:1
+   |
+LL | impl const U for u8 {}
+   | ^^^^^^^^^^^^^^^^^^^^^^
+   |
+note: this impl is (implicitly) stable...
+  --> $DIR/staged-api.rs:98:1
+   |
+LL | impl const U for u8 {}
+   | ^^^^^^^^^^^^^^^^^^^^^^
+note: ...but the trait is unstable
+  --> $DIR/staged-api.rs:91:7
+   |
+LL | trait U {}
+   |       ^
+
+error: trait implementations cannot be const stable yet
+  --> $DIR/staged-api.rs:102:1
+   |
+LL | impl const U for u16 {}
+   | ^^^^^^^^^^^^^^^^^^^^^^^
+   |
+   = note: see issue #67792 <https://github.com/rust-lang/rust/issues/67792> for more information
+
+error: const stability on the impl does not match the const stability on the trait
+  --> $DIR/staged-api.rs:102:1
+   |
+LL | impl const U for u16 {}
+   | ^^^^^^^^^^^^^^^^^^^^^^^
+   |
+note: this impl is (implicitly) stable...
+  --> $DIR/staged-api.rs:102:1
+   |
+LL | impl const U for u16 {}
+   | ^^^^^^^^^^^^^^^^^^^^^^^
+note: ...but the trait is unstable
+  --> $DIR/staged-api.rs:91:7
+   |
+LL | trait U {}
+   |       ^
+
+error: trait implementations cannot be const stable yet
+  --> $DIR/staged-api.rs:113:1
+   |
+LL | impl const S for u16 {}
+   | ^^^^^^^^^^^^^^^^^^^^^^^
+   |
+   = note: see issue #67792 <https://github.com/rust-lang/rust/issues/67792> for more information
+
+error: const stability on the impl does not match the const stability on the trait
+  --> $DIR/staged-api.rs:117:1
+   |
+LL | impl const S for u32 {}
+   | ^^^^^^^^^^^^^^^^^^^^^^^
+   |
+note: this impl is unstable...
+  --> $DIR/staged-api.rs:117:1
+   |
+LL | impl const S for u32 {}
+   | ^^^^^^^^^^^^^^^^^^^^^^^
+note: ...but the trait is stable
+  --> $DIR/staged-api.rs:95:7
+   |
+LL | trait S {}
+   |       ^
+
 error: const function that might be (indirectly) exposed to stable cannot use `#[feature(const_trait_impl)]`
   --> $DIR/staged-api.rs:38:5
    |
@@ -323,5 +390,5 @@ LL + #[rustc_allow_const_fn_unstable(const_trait_impl)]
 LL | const fn implicitly_stable_const_context() {
    |
 
-error: aborting due to 19 previous errors
+error: aborting due to 24 previous errors