8 files changed, 22 insertions, 19 deletions
diff --git a/library/alloc/src/collections/btree/map/tests.rs b/library/alloc/src/collections/btree/map/tests.rs
index 4c372b1d6..700b1463b 100644
--- a/library/alloc/src/collections/btree/map/tests.rs
+++ b/library/alloc/src/collections/btree/map/tests.rs
@@ -1,12 +1,12 @@
-use super::super::testing::crash_test::{CrashTestDummy, Panic};
-use super::super::testing::ord_chaos::{Cyclic3, Governed, Governor};
-use super::super::testing::rng::DeterministicRng;
 use super::Entry::{Occupied, Vacant};
 use super::*;
 use crate::boxed::Box;
 use crate::fmt::Debug;
 use crate::rc::Rc;
 use crate::string::{String, ToString};
+use crate::testing::crash_test::{CrashTestDummy, Panic};
+use crate::testing::ord_chaos::{Cyclic3, Governed, Governor};
+use crate::testing::rng::DeterministicRng;
 use crate::vec::Vec;
 use std::cmp::Ordering;
 use std::convert::TryFrom;
diff --git a/library/alloc/src/collections/btree/mod.rs b/library/alloc/src/collections/btree/mod.rs
index 9d43ac5c5..7552f2fc0 100644
--- a/library/alloc/src/collections/btree/mod.rs
+++ b/library/alloc/src/collections/btree/mod.rs
@@ -21,6 +21,3 @@ trait Recover<Q: ?Sized> {
     fn take(&mut self, key: &Q) -> Option<Self::Key>;
     fn replace(&mut self, key: Self::Key) -> Option<Self::Key>;
 }
-
-#[cfg(test)]
-mod testing;
diff --git a/library/alloc/src/collections/btree/node.rs b/library/alloc/src/collections/btree/node.rs
index da766b67a..691246644 100644
--- a/library/alloc/src/collections/btree/node.rs
+++ b/library/alloc/src/collections/btree/node.rs
@@ -318,7 +318,10 @@ impl<BorrowType: marker::BorrowType, K, V, Type> NodeRef<BorrowType, K, V, Type>
     pub fn ascend(
         self,
     ) -> Result<Handle<NodeRef<BorrowType, K, V, marker::Internal>, marker::Edge>, Self> {
-        let _ = BorrowType::TRAVERSAL_PERMIT;
+        const {
+            assert!(BorrowType::TRAVERSAL_PERMIT);
+        }
+
         // We need to use raw pointers to nodes because, if BorrowType is marker::ValMut,
         // there might be outstanding mutable references to values that we must not invalidate.
         let leaf_ptr: *const _ = Self::as_leaf_ptr(&self);
@@ -1003,7 +1006,10 @@ impl<BorrowType: marker::BorrowType, K, V>
     /// `edge.descend().ascend().unwrap()` and `node.ascend().unwrap().descend()` should
     /// both, upon success, do nothing.
     pub fn descend(self) -> NodeRef<BorrowType, K, V, marker::LeafOrInternal> {
-        let _ = BorrowType::TRAVERSAL_PERMIT;
+        const {
+            assert!(BorrowType::TRAVERSAL_PERMIT);
+        }
+
         // We need to use raw pointers to nodes because, if BorrowType is
         // marker::ValMut, there might be outstanding mutable references to
         // values that we must not invalidate. There's no worry accessing the
@@ -1666,17 +1672,17 @@ pub mod marker {
     pub struct ValMut<'a>(PhantomData<&'a mut ()>);
 
     pub trait BorrowType {
-        // If node references of this borrow type allow traversing to other
-        // nodes in the tree, this constant can be evaluated. Thus reading it
-        // serves as a compile-time assertion.
-        const TRAVERSAL_PERMIT: () = ();
+        /// If node references of this borrow type allow traversing to other
+        /// nodes in the tree, this constant is set to `true`. It can be used
+        /// for a compile-time assertion.
+        const TRAVERSAL_PERMIT: bool = true;
     }
     impl BorrowType for Owned {
-        // Reject evaluation, because traversal isn't needed. Instead traversal
-        // happens using the result of `borrow_mut`.
-        // By disabling traversal, and only creating new references to roots,
-        // we know that every reference of the `Owned` type is to a root node.
-        const TRAVERSAL_PERMIT: () = panic!();
+        /// Reject traversal, because it isn't needed. Instead traversal
+        /// happens using the result of `borrow_mut`.
+        /// By disabling traversal, and only creating new references to roots,
+        /// we know that every reference of the `Owned` type is to a root node.
+        const TRAVERSAL_PERMIT: bool = false;
     }
     impl BorrowType for Dying {}
     impl<'a> BorrowType for Immut<'a> {}
diff --git a/library/alloc/src/collections/btree/set/tests.rs b/library/alloc/src/collections/btree/set/tests.rs
index 502d3e1d1..7b8d41a60 100644
--- a/library/alloc/src/collections/btree/set/tests.rs
+++ b/library/alloc/src/collections/btree/set/tests.rs
@@ -1,6 +1,6 @@
-use super::super::testing::crash_test::{CrashTestDummy, Panic};
-use super::super::testing::rng::DeterministicRng;
 use super::*;
+use crate::testing::crash_test::{CrashTestDummy, Panic};
+use crate::testing::rng::DeterministicRng;
 use crate::vec::Vec;
 use std::cmp::Ordering;
 use std::hash::{Hash, Hasher};
diff --git a/library/alloc/src/collections/btree/testing/crash_test.rs b/library/alloc/src/testing/crash_test.rs
index bcf5f5f72..bcf5f5f72 100644
--- a/library/alloc/src/collections/btree/testing/crash_test.rs
+++ b/library/alloc/src/testing/crash_test.rs
diff --git a/library/alloc/src/collections/btree/testing/mod.rs b/library/alloc/src/testing/mod.rs
index 7a094f8a5..7a094f8a5 100644
--- a/library/alloc/src/collections/btree/testing/mod.rs
+++ b/library/alloc/src/testing/mod.rs
diff --git a/library/alloc/src/collections/btree/testing/ord_chaos.rs b/library/alloc/src/testing/ord_chaos.rs
index 96ce7c157..96ce7c157 100644
--- a/library/alloc/src/collections/btree/testing/ord_chaos.rs
+++ b/library/alloc/src/testing/ord_chaos.rs
diff --git a/library/alloc/src/collections/btree/testing/rng.rs b/library/alloc/src/testing/rng.rs
index ecf543bee..ecf543bee 100644
--- a/library/alloc/src/collections/btree/testing/rng.rs
+++ b/library/alloc/src/testing/rng.rs