Auto merge of #80707 - oli-obk:stability_hole_const_intrinsics, r=RalfJung

Stability oddity with const intrinsics

cc `@RalfJung`

In https://github.com/rust-lang/rust/pull/80699#discussion_r551495670 `@usbalbin` realized we accepted some intrinsics as `const` without a `#[rustc_const_(un)stable]` attribute. I did some digging, and that example works because intrinsics inherit their stability from their parents... including `#[rustc_const_(un)stable]` attributes. While we may want to fix that (not sure, wasn't there just a MCPed PR that caused this on purpose?), we definitely want tests for it, thus this PR adding tests and some fun tracing statements.

4 files changed, 50 insertions, 0 deletions

diff --git a/src/test/ui/consts/intrinsic_without_const_stab.rs b/src/test/ui/consts/intrinsic_without_const_stab.rs
new file mode 100644
index 00000000000..810158a2957
--- /dev/null
+++ b/src/test/ui/consts/intrinsic_without_const_stab.rs
@@ -0,0 +1,17 @@
+#![feature(intrinsics, staged_api, const_intrinsic_copy)]
+#![stable(feature = "core", since = "1.6.0")]
+
+#[stable(feature = "rust1", since = "1.0.0")]
+#[rustc_const_unstable(feature = "const_intrinsic_copy", issue = "80697")]
+#[inline]
+pub const unsafe fn copy<T>(src: *const T, dst: *mut T, count: usize) {
+    // Const stability attributes are not inherited from parent items.
+    extern "rust-intrinsic" {
+        fn copy<T>(src: *const T, dst: *mut T, count: usize);
+    }
+
+    unsafe { copy(src, dst, count) }
+    //~^ ERROR calls in constant functions are limited to constant functions
+}
+
+fn main() {}
diff --git a/src/test/ui/consts/intrinsic_without_const_stab.stderr b/src/test/ui/consts/intrinsic_without_const_stab.stderr
new file mode 100644
index 00000000000..5a42823a605
--- /dev/null
+++ b/src/test/ui/consts/intrinsic_without_const_stab.stderr
@@ -0,0 +1,9 @@
+error[E0015]: calls in constant functions are limited to constant functions, tuple structs and tuple variants
+  --> $DIR/intrinsic_without_const_stab.rs:13:14
+   |
+LL |     unsafe { copy(src, dst, count) }
+   |              ^^^^^^^^^^^^^^^^^^^^^
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0015`.
diff --git a/src/test/ui/consts/intrinsic_without_const_stab_fail.rs b/src/test/ui/consts/intrinsic_without_const_stab_fail.rs
new file mode 100644
index 00000000000..bf2c44169d4
--- /dev/null
+++ b/src/test/ui/consts/intrinsic_without_const_stab_fail.rs
@@ -0,0 +1,15 @@
+#![feature(intrinsics, staged_api, const_intrinsic_copy)]
+#![stable(feature = "core", since = "1.6.0")]
+
+extern "rust-intrinsic" {
+    fn copy<T>(src: *const T, dst: *mut T, count: usize);
+}
+
+#[stable(feature = "rust1", since = "1.0.0")]
+#[rustc_const_unstable(feature = "const_intrinsic_copy", issue = "80697")]
+#[inline]
+pub const unsafe fn stuff<T>(src: *const T, dst: *mut T, count: usize) {
+    unsafe { copy(src, dst, count) } //~ ERROR calls in constant functions are limited
+}
+
+fn main() {}
diff --git a/src/test/ui/consts/intrinsic_without_const_stab_fail.stderr b/src/test/ui/consts/intrinsic_without_const_stab_fail.stderr
new file mode 100644
index 00000000000..d4a2989e785
--- /dev/null
+++ b/src/test/ui/consts/intrinsic_without_const_stab_fail.stderr
@@ -0,0 +1,9 @@
+error[E0015]: calls in constant functions are limited to constant functions, tuple structs and tuple variants
+  --> $DIR/intrinsic_without_const_stab_fail.rs:12:14
+   |
+LL |     unsafe { copy(src, dst, count) }
+   |              ^^^^^^^^^^^^^^^^^^^^^
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0015`.