import Lean open Lean def c1 : Bool := true unsafe def tst1 : CoreM Unit := do let env ← getEnv; let v := env.evalConst Bool {} `c1; IO.println v /-- info: ok: true -/ #guard_msgs in #eval tst1 -- used to output incorrect value (ok false). Reason: the unboxed value `true` is `1`, but the boxed `false` value is also `1`. def c2 : Bool := false unsafe def tst2 : CoreM Unit := do let env ← getEnv; let v := env.evalConst Bool {} `c2; IO.println v /-- info: ok: false -/ #guard_msgs in #eval tst2 -- used to crash since `0` is not a valid boxed value