Restrict const ty's regions to static when putting them in canonical var list

2 files changed, 34 insertions, 0 deletions

diff --git a/tests/ui/coherence/negative-coherence/regions-in-canonical.rs b/tests/ui/coherence/negative-coherence/regions-in-canonical.rs
new file mode 100644
index 00000000000..6c2a11e0135
--- /dev/null
+++ b/tests/ui/coherence/negative-coherence/regions-in-canonical.rs
@@ -0,0 +1,23 @@
+//@ check-pass
+
+#![feature(adt_const_params)]
+//~^ WARN the feature `adt_const_params` is incomplete
+#![feature(with_negative_coherence, negative_impls)]
+
+pub trait A<const K: &'static str> {}
+pub trait C {}
+
+
+struct W<T>(T);
+
+// Negative coherence:
+// Proving `W<!T>: !A<"">` requires proving `CONST alias-eq ""`, which requires proving
+// `CONST normalizes-to (?1c: &str)`. The type's region is uniquified, so it ends up being
+// put in to the canonical vars list with an infer region => ICE.
+impl<T> C for T where T: A<""> {}
+impl<T> C for W<T> {}
+
+impl<T> !A<CONST> for W<T> {}
+const CONST: &str = "";
+
+fn main() {}
diff --git a/tests/ui/coherence/negative-coherence/regions-in-canonical.stderr b/tests/ui/coherence/negative-coherence/regions-in-canonical.stderr
new file mode 100644
index 00000000000..dc8c926f182
--- /dev/null
+++ b/tests/ui/coherence/negative-coherence/regions-in-canonical.stderr
@@ -0,0 +1,11 @@
+warning: the feature `adt_const_params` is incomplete and may not be safe to use and/or cause compiler crashes
+  --> $DIR/regions-in-canonical.rs:3:12
+   |
+LL | #![feature(adt_const_params)]
+   |            ^^^^^^^^^^^^^^^^
+   |
+   = note: see issue #95174 <https://github.com/rust-lang/rust/issues/95174> for more information
+   = note: `#[warn(incomplete_features)]` on by default
+
+warning: 1 warning emitted
+