Method is_nat_zero

crates/kernel/src/def_eq.rs:916–922

Check if expression is nat zero (literal 0 or Nat.zero constructor).

(&self, e: &KExpr<M>)

        } else {
          match self.try_get_const(&ctors[0])? {
            Some(KConst::Ctor { fields, .. }) => fields == 0,
            _ => false,
          }
        }
      },
      _ => return Ok(false),
    };
    if !is_unit {
      return Ok(false);
    }