Set: pp::colors
  Set: pp::unicode
λ x : ?M::0, x
λ x : ?M::0, x
errmsg1.lean:4:10: error: invalid expression, it still contains metavariables after elaboration, metavariable: ?M::0, type:
(Type U)
errmsg1.lean:6:3: error: failed to synthesize metavar, its type is not a proposition, metavariable: ?M::0, type:
A : Type, x : A ⊢ A → A
errmsg1.lean:8:34: error: invalid definition, type still contains metavariables after elaboration, metavariable: ?M::3, type:
(Type U)