1 files changed, 80 insertions, 0 deletions
diff --git a/compiler/rustc_transmute/src/layout/tree/tests.rs b/compiler/rustc_transmute/src/layout/tree/tests.rs
new file mode 100644
index 000000000..90515e92f
--- /dev/null
+++ b/compiler/rustc_transmute/src/layout/tree/tests.rs
@@ -0,0 +1,80 @@
+use super::Tree;
+
+#[derive(Debug, Hash, Eq, PartialEq, Clone, Copy)]
+pub enum Def {
+    Visible,
+    Invisible,
+}
+
+impl super::Def for Def {}
+
+mod prune {
+    use super::*;
+
+    mod should_simplify {
+        use super::*;
+
+        #[test]
+        fn seq_1() {
+            let layout: Tree<Def, !> = Tree::def(Def::Visible).then(Tree::from_bits(0x00));
+            assert_eq!(layout.prune(&|d| matches!(d, Def::Visible)), Tree::from_bits(0x00));
+        }
+
+        #[test]
+        fn seq_2() {
+            let layout: Tree<Def, !> =
+                Tree::from_bits(0x00).then(Tree::def(Def::Visible)).then(Tree::from_bits(0x01));
+
+            assert_eq!(
+                layout.prune(&|d| matches!(d, Def::Visible)),
+                Tree::from_bits(0x00).then(Tree::from_bits(0x01))
+            );
+        }
+    }
+
+    mod should_reject {
+        use super::*;
+
+        #[test]
+        fn invisible_def() {
+            let layout: Tree<Def, !> = Tree::def(Def::Invisible);
+            assert_eq!(layout.prune(&|d| matches!(d, Def::Visible)), Tree::uninhabited());
+        }
+
+        #[test]
+        fn invisible_def_in_seq_len_2() {
+            let layout: Tree<Def, !> = Tree::def(Def::Visible).then(Tree::def(Def::Invisible));
+            assert_eq!(layout.prune(&|d| matches!(d, Def::Visible)), Tree::uninhabited());
+        }
+
+        #[test]
+        fn invisible_def_in_seq_len_3() {
+            let layout: Tree<Def, !> =
+                Tree::def(Def::Visible).then(Tree::from_bits(0x00)).then(Tree::def(Def::Invisible));
+            assert_eq!(layout.prune(&|d| matches!(d, Def::Visible)), Tree::uninhabited());
+        }
+    }
+
+    mod should_accept {
+        use super::*;
+
+        #[test]
+        fn visible_def() {
+            let layout: Tree<Def, !> = Tree::def(Def::Visible);
+            assert_eq!(layout.prune(&|d| matches!(d, Def::Visible)), Tree::unit());
+        }
+
+        #[test]
+        fn visible_def_in_seq_len_2() {
+            let layout: Tree<Def, !> = Tree::def(Def::Visible).then(Tree::def(Def::Visible));
+            assert_eq!(layout.prune(&|d| matches!(d, Def::Visible)), Tree::unit());
+        }
+
+        #[test]
+        fn visible_def_in_seq_len_3() {
+            let layout: Tree<Def, !> =
+                Tree::def(Def::Visible).then(Tree::from_bits(0x00)).then(Tree::def(Def::Visible));
+            assert_eq!(layout.prune(&|d| matches!(d, Def::Visible)), Tree::from_bits(0x00));
+        }
+    }
+}