error[E0623]: lifetime mismatch
  --> src/executor.rs:80:48
   |
79 |     fn simple_evaluate_test<'a, 'b>(ctx: &Context<'a>, val: ValueKind<'b>) {
   |                                           -----------       -------------
   |                                           |
   |                                           these two types are declared with different lifetimes...
80 |         let simple_val = Arc::new(simple_value(val.clone()));
   |                                                ^^^^^^^^^^^ ...but data from `ctx` flows into `val` here