mulcommErrorMessage.lean:8:13-13:25: error: type mismatch
  fun a b => ?m a b
has type
  (a : ?m) → (b : ?m a) → ?m a b : Sort (imax ?u ?u ?u)
but is expected to have type
  a✝ * b✝ = b✝ * a✝ : Prop
the following variables have been introduced by the implicit lambda feature
  a✝ : Bool
  b✝ : Bool
you can disable implict lambdas using `@` or writing a lambda expression with `{}` or `[]` binder annotations.
mulcommErrorMessage.lean:11:22-11:25: error: type mismatch
  rfl
has type
  true = true : Prop
but is expected to have type
  true = false : Prop
mulcommErrorMessage.lean:16:3-17:47: error: type mismatch
  fun a b => Bool.casesOn a (?m a b) (?m a b)
has type
  (a b : Bool) → ?m a b a : Sort (imax 1 1 ?u)
but is expected to have type
  a✝ * b✝ = b✝ * a✝ : Prop
the following variables have been introduced by the implicit lambda feature
  a✝ : Bool
  b✝ : Bool
you can disable implict lambdas using `@` or writing a lambda expression with `{}` or `[]` binder annotations.
mulcommErrorMessage.lean:17:27-17:47: error: application type mismatch
  Bool.casesOn a ?m (Bool.casesOn b ?m ?m)
argument
  Bool.casesOn b ?m ?m
has type
  ?m a b b : Sort ?u
but is expected to have type
  ?m a b true : Sort ?u