/-! # Basic section variable tests -/

/-! Directly referenced variables should be included. -/
variable {n : Nat} in
theorem t1 : n = n := by induction n <;> rfl

/-! Variables mentioned only in the body should not be included. -/
variable {n : Nat} in
/-- error: Unknown identifier `n` -/
#guard_msgs in
theorem t2 : ∃ (n : Nat), n = n := by exists n

/-! Variables transitively mentioned should be included. -/
variable {n : Nat} (h : n = n) in
theorem t3 : h = h := rfl

/-! Instance variables mentioning only included variables should be included. -/
variable {α : Type} [ToString α] in
theorem t4 (a : α) : a = a := let _ := toString a; rfl

/-! Instance variables not mentioning only included variables should not be included. -/
variable {α β : Type} [Coe α β] in
/--
error: don't know how to synthesize placeholder
context:
α : Type
a : α
⊢ a = a
-/
#guard_msgs in
theorem t5 (a : α) : a = a := _

/-! Accidentally included variables should be warned for. -/
variable {α : Type} [ToString α] in
/--
warning: automatically included section variable(s) unused in theorem `t6`:
  [ToString α]
consider restructuring your `variable` declarations so that the variables are not in scope or explicitly omit them:
  omit [ToString α] in theorem ...

Note: This linter can be disabled with `set_option linter.unusedSectionVars false`
-/
#guard_msgs in
theorem t6 (a : α) : a = a := rfl

/-! `include` should always include. -/
variable {n : Nat} in
include n in
theorem t7 : ∃ (n : Nat), n = n := by exists n

/-! traversal order bug broke instance inclusion -/
variable {M N : Type} (r : N → N → Prop)
class IsTrans (N : Type) (r : N → N → Prop) : Prop
variable [IsTrans N r] {a b c d : N}
/--
warning: automatically included section variable(s) unused in theorem `act_rel_of_rel_of_act_rel`:
  [IsTrans N r]
consider restructuring your `variable` declarations so that the variables are not in scope or explicitly omit them:
  omit [IsTrans N r] in theorem ...

Note: This linter can be disabled with `set_option linter.unusedSectionVars false`
-/
#guard_msgs in
theorem act_rel_of_rel_of_act_rel (ab : r a b) : r a b := ab

/-! More complex include case, instance should be included via `f`. -/
class EquivLike (F : Type) (α β : Type) : Type
variable {F : Type} [EquivLike F α β] (f : F) in
include f in
theorem MulEquiv.decompositionMonoid (_b : β) : α = α :=
  let _ : EquivLike F α β := inferInstance; let _ := f; rfl
/-- info: MulEquiv.decompositionMonoid {α β F : Type} [EquivLike F α β] (f : F) (_b : β) : α = α -/
#guard_msgs in
#check MulEquiv.decompositionMonoid

section
/-! `omit` -/
variable [ToString α] [ToString β]

/--
error: failed to synthesize instance of type class
  ToString α

Hint: Type class instance resolution failures can be inspected with the `set_option trace.Meta.synthInstance true` command.
-/
#guard_msgs in
omit [ToString α] in
theorem t8 (a : α) (b : β) : True :=
  let _ := toString a; let _ := toString b; trivial

/--
error: failed to synthesize instance of type class
  ToString β

Hint: Type class instance resolution failures can be inspected with the `set_option trace.Meta.synthInstance true` command.
-/
#guard_msgs in
omit [ToString β] in
theorem t9 (a : α) (b : β) : True :=
  let _ := toString a; let _ := toString b; trivial

/--
error: failed to synthesize instance of type class
  ToString α

Hint: Type class instance resolution failures can be inspected with the `set_option trace.Meta.synthInstance true` command.
---
error: failed to synthesize instance of type class
  ToString β

Hint: Type class instance resolution failures can be inspected with the `set_option trace.Meta.synthInstance true` command.
-/
#guard_msgs in
omit [ToString _] in
theorem t10 (a : α) (b : β) : True :=
  let _ := toString a; let _ := toString b; trivial
end

/-! illegal `omit`s -/

/-- error: invalid 'omit', `α` has not been declared in the current scope -/
#guard_msgs in
variable (a : α) in
omit α in
theorem t11 (a : α) : True := trivial

/-- error: cannot omit referenced section variable `α` -/
#guard_msgs in
variable (α : Type) in
omit α in
theorem t12 (a : α) : True := trivial

/-- error: cannot omit referenced section variable `inst✝` -/
#guard_msgs in
variable [ToString α] in
omit [ToString α] in
theorem t13 (a : α) : toString a = toString a := rfl

set_option pp.mvars false in
/--
error: Application type mismatch: The argument
  True
has type
  Prop
of sort `Type` but is expected to have type
  Type _
of sort `Type (_ + 1)` in the application
  ToString True
-/
#guard_msgs in
omit [ToString True]

/-- error: `[ToString Nat]` did not match any variables in the current scope -/
#guard_msgs in
omit [ToString Nat]

/-! `omit` can also be used to revert an `include` -/

variable (α : Type) in
include α in
omit α in
theorem t14 : True := trivial

/--
warning: automatically included section variable(s) unused in theorem `t15`:
  α
consider restructuring your `variable` declarations so that the variables are not in scope or explicitly omit them:
  omit α in theorem ...

Note: This linter can be disabled with `set_option linter.unusedSectionVars false`
-/
#guard_msgs in
variable (α : Type) in
include α in
omit α in
include α in
theorem t15 : True := trivial

/-! But you probably shouldn't use it -/

set_option linter.omit true in
/--
warning: `omit` should be avoided in favor of restructuring your `variable` declarations

Note: This linter can be disabled with `set_option linter.omit false`
-/
#guard_msgs in
variable (α : Type) in
include α in
omit α in
theorem t16 : True := trivial