Fixed edge case

bvssvni · May 29, 2020 · 34adea3 · 34adea3
1 parent d2866e8
commit 34adea3
Showing 1 changed file with 1 addition and 0 deletions.
diff --git a/src/lib.rs b/src/lib.rs
@@ -816,6 +816,7 @@ impl Context {
     /// This is used on the right side in a reduction rule.
     pub fn substitute(&self, x: &Expr) -> Result<Expr, Error> {
         match x {
+            Sym(RetNegVar(_)) => Err(Error::InvalidComputation),
             Sym(Var(name)) | Sym(ArityVar(name, _)) => {
                 for i in (0..self.vars.len()).rev() {
                     if &self.vars[i].0 == name {