constr_tac_errors.lean:3:2: error:invalid 'constructor' tactic, goal is an inductive datatype, but it does not have 1 constructor(s)
proof state:

⊢ ℕ
constr_tac_errors.lean:4:0: error: don't know how to synthesize placeholder

⊢ ℕ
constr_tac_errors.lean:4:0: error: failed to add declaration 'example' to environment, value has metavariables
remark: set 'formatter.hide_full_terms' to false to see the complete term
  ?M_1
constr_tac_errors.lean:12:2: error:invalid 'constructor' tactic, goal is an inductive datatype, but it does not have 2 constructor(s)
proof state:
a b : Prop,
Ha : a,
Hb : b
⊢ a ∧ b
constr_tac_errors.lean:13:0: error: don't know how to synthesize placeholder
a b : Prop
⊢ a → b → a ∧ b
constr_tac_errors.lean:13:0: error: failed to add declaration 'example' to environment, value has metavariables
remark: set 'formatter.hide_full_terms' to false to see the complete term
  ?M_1
constr_tac_errors.lean:18:2: error:invalid 'constructor' tactic, goal is an inductive datatype, but it does not have 2 constructor(s)
proof state:
a b : Prop,
Ha : a,
Hb : b
⊢ a ∧ b
constr_tac_errors.lean:19:0: error: don't know how to synthesize placeholder
a b : Prop
⊢ a → b → a ∧ b
constr_tac_errors.lean:19:0: error: failed to add declaration 'example' to environment, value has metavariables
remark: set 'formatter.hide_full_terms' to false to see the complete term
  ?M_1
constr_tac_errors.lean:31:2: error:invalid 'constructor' tactic, too many arguments have been provided
proof state:
a b : Prop,
Ha : a,
Hb : b
⊢ unit
constr_tac_errors.lean:32:0: error: don't know how to synthesize placeholder
a b : Prop
⊢ a → b → unit
constr_tac_errors.lean:32:0: error: failed to add declaration 'example' to environment, value has metavariables
remark: set 'formatter.hide_full_terms' to false to see the complete term
  ?M_1
constr_tac_errors.lean:39:2: error:invalid 'constructor' tactic, goal is not an inductive datatype
proof state:

⊢ ℕ → ℕ
constr_tac_errors.lean:40:0: error: don't know how to synthesize placeholder

⊢ ℕ → ℕ
constr_tac_errors.lean:40:0: error: failed to add declaration 'example' to environment, value has metavariables
remark: set 'formatter.hide_full_terms' to false to see the complete term
  ?M_1