layout_of: put back not-so-unreachable case

4 files changed, 77 insertions, 0 deletions

diff --git a/tests/ui/layout/gce-rigid-const-in-array-len.rs b/tests/ui/layout/gce-rigid-const-in-array-len.rs
new file mode 100644
index 00000000000..8e57907a2c5
--- /dev/null
+++ b/tests/ui/layout/gce-rigid-const-in-array-len.rs
@@ -0,0 +1,27 @@
+//! With `feature(generic_const_exprs)`, anon consts (e.g. length in array types) will
+//! inherit their parent's predicates. When combined with `feature(trivial_bounds)`, it
+//! is possible to have an unevaluated constant that is rigid, but not generic.
+//!
+//! This is what happens below: `u8: A` does not hold in the global environment, but
+//! with trivial bounds + GCE it it possible that `<u8 as A>::B` can appear in an array
+//! length without causing a compile error. This constant is *rigid* (i.e. it cannot be
+//! normalized further), but it is *not generic* (i.e. it does not depend on any generic
+//! parameters).
+//!
+//! This test ensures that we do not ICE in layout computation when encountering such a
+//! constant.
+
+#![feature(rustc_attrs)]
+#![feature(generic_const_exprs)] //~ WARNING: the feature `generic_const_exprs` is incomplete
+#![feature(trivial_bounds)]
+
+#![crate_type = "lib"]
+
+trait A {
+    const B: usize;
+}
+
+#[rustc_layout(debug)]
+struct S([u8; <u8 as A>::B]) //~ ERROR: the type `[u8; <u8 as A>::B]` has an unknown layout
+where
+    u8: A;
diff --git a/tests/ui/layout/gce-rigid-const-in-array-len.stderr b/tests/ui/layout/gce-rigid-const-in-array-len.stderr
new file mode 100644
index 00000000000..6149debdfe8
--- /dev/null
+++ b/tests/ui/layout/gce-rigid-const-in-array-len.stderr
@@ -0,0 +1,17 @@
+warning: the feature `generic_const_exprs` is incomplete and may not be safe to use and/or cause compiler crashes
+  --> $DIR/gce-rigid-const-in-array-len.rs:15:12
+   |
+LL | #![feature(generic_const_exprs)]
+   |            ^^^^^^^^^^^^^^^^^^^
+   |
+   = note: see issue #76560 <https://github.com/rust-lang/rust/issues/76560> for more information
+   = note: `#[warn(incomplete_features)]` on by default
+
+error: the type `[u8; <u8 as A>::B]` has an unknown layout
+  --> $DIR/gce-rigid-const-in-array-len.rs:25:1
+   |
+LL | struct S([u8; <u8 as A>::B])
+   | ^^^^^^^^
+
+error: aborting due to 1 previous error; 1 warning emitted
+
diff --git a/tests/ui/layout/unconstrained-param-ice-137308.rs b/tests/ui/layout/unconstrained-param-ice-137308.rs
new file mode 100644
index 00000000000..d460fc64f1f
--- /dev/null
+++ b/tests/ui/layout/unconstrained-param-ice-137308.rs
@@ -0,0 +1,18 @@
+//! Regression test for <https://github.com/rust-lang/rust/issues/137308>.
+//!
+//! This used to ICE in layout computation, because `<u8 as A>::B` fails to normalize
+//! due to the unconstrained param on the impl.
+
+#![feature(rustc_attrs)]
+#![crate_type = "lib"]
+
+trait A {
+    const B: usize;
+}
+
+impl<C: ?Sized> A for u8 { //~ ERROR: the type parameter `C` is not constrained
+    const B: usize = 42;
+}
+
+#[rustc_layout(debug)]
+struct S([u8; <u8 as A>::B]); //~ ERROR: the type `[u8; <u8 as A>::B]` has an unknown layout
diff --git a/tests/ui/layout/unconstrained-param-ice-137308.stderr b/tests/ui/layout/unconstrained-param-ice-137308.stderr
new file mode 100644
index 00000000000..03ee941d37e
--- /dev/null
+++ b/tests/ui/layout/unconstrained-param-ice-137308.stderr
@@ -0,0 +1,15 @@
+error[E0207]: the type parameter `C` is not constrained by the impl trait, self type, or predicates
+  --> $DIR/unconstrained-param-ice-137308.rs:13:6
+   |
+LL | impl<C: ?Sized> A for u8 {
+   |      ^ unconstrained type parameter
+
+error: the type `[u8; <u8 as A>::B]` has an unknown layout
+  --> $DIR/unconstrained-param-ice-137308.rs:18:1
+   |
+LL | struct S([u8; <u8 as A>::B]);
+   | ^^^^^^^^
+
+error: aborting due to 2 previous errors
+
+For more information about this error, try `rustc --explain E0207`.