diff --git a/src/main.rs b/src/main.rs
index 24d9e75..4ef5371 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -475,6 +475,7 @@ fn could_match(vars: Option<&[Symbol]>, lhs: &Sexp, expr: &Sexp) -> bool {
 
 // type Matches<'src> = HashMap<Symbol, HashSet<&'src Sexp>>;
 
+// TODO: there. can. be. at most. one. match.
 // i'm happy that this is faster, but it might be worth going back to the per-variable thing
 fn matches<'src>(vars: &HashSet<Symbol>, lhs: &Sexp, expr: &'src Sexp) -> HashSet<&'src Sexp> {
     match (lhs, expr) {