1 files changed, 23 insertions, 0 deletions
diff --git a/src/let_else.rs b/src/let_else.rs
new file mode 100644
index 0000000..da17a68
--- /dev/null
+++ b/src/let_else.rs
@@ -0,0 +1,23 @@
+/// Binds the given expression to the given pattern, or else executes
+/// `debug_assert!(false);` with a helpful panic message and returns.
+macro_rules! assume {
+    ($pattern:pat, $value:expr) => {
+        // The expression might change each time it's evaluated, so we
+        // have to bind it so that we can reuse it in the panic message.
+        let _value = $value;
+
+        let $pattern = _value else {
+            debug_assert!(
+                false,
+                "assertion `left matches right` failed:
+ left: {}
+right: {:?}",
+                stringify!($pattern),
+                _value
+            );
+            return;
+        };
+    };
+}
+
+pub(crate) use assume;