Clean up expression sizes, which seems to fix stack blowouts.

src/syntax.rs

@@ -331,8 +331,6 @@ proptest::proptest! {
      #[test]
      fn generated_run_or_overflow(program in Program::arbitrary_with(GenerationEnvironment::new(false))) {
         use crate::eval::{EvalError, PrimOpError};
-        println!("-----------\nprogram:\n{}\n", program);
-        println!("-----------\nresult:\n{:?}\n", program.eval());
         prop_assert!(matches!(program.eval(), Ok(_) | Err(EvalError::PrimOp(PrimOpError::MathFailure(_)))));
      }
 }