The nontriviality tactic.

theorem Mathlib.Tactic.Nontriviality.subsingleton_or_nontrivial_elim {p : Prop} {α : Type u} (h₁ : Subsingleton α → p) (h₂ : Nontrivial α → p) : p

def Mathlib.Tactic.Nontriviality.nontrivialityByElim {u : Lean.Level} (α : Q(Type u)) (g : Lean.MVarId) (simpArgs : Array Lean.Syntax) : Lean.MetaM Lean.MVarId

Tries to generate a Nontrivial α instance by performing case analysis on subsingleton_or_nontrivial α, attempting to discharge the subsingleton branch using lemmas with @[nontriviality] attribute, including Subsingleton.le and eq_iff_true_of_subsingleton.

def Mathlib.Tactic.Nontriviality.nontrivialityByAssumption (g : Lean.MVarId) : Lean.MetaM Unit

Tries to generate a Nontrivial α instance using nontrivial_of_ne or nontrivial_of_lt and local hypotheses.

def Mathlib.Tactic.Nontriviality.nontriviality : Lean.ParserDescr

Attempts to generate a Nontrivial α hypothesis.

The tactic first checks to see that there is not already a Nontrivial α instance before trying to synthesize one using other techniques.

If the goal is an (in)equality, the type α is inferred from the goal. Otherwise, the type needs to be specified in the tactic invocation, as nontriviality α.

The nontriviality tactic will first look for strict inequalities amongst the hypotheses, and use these to derive the Nontrivial instance directly.

Otherwise, it will perform a case split on Subsingleton α ∨ Nontrivial α, and attempt to discharge the Subsingleton goal using simp [h₁, h₂, ..., hₙ, nontriviality], where [h₁, h₂, ..., hₙ] is a list of additional simp lemmas that can be passed to nontriviality using the syntax nontriviality α using h₁, h₂, ..., hₙ.

example {R : Type} [OrderedRing R] {a : R} (h : 0 < a) : 0 < a := by
  nontriviality -- There is now a `Nontrivial R` hypothesis available.
  assumption

example {R : Type} [CommRing R] {r s : R} : r * s = s * r := by
  nontriviality -- There is now a `Nontrivial R` hypothesis available.
  apply mul_comm

example {R : Type} [OrderedRing R] {a : R} (h : 0 < a) : (2 : ℕ) ∣ 4 := by
  nontriviality R -- there is now a `Nontrivial R` hypothesis available.
  dec_trivial

def myeq {α : Type} (a b : α) : Prop := a = b

example {α : Type} (a b : α) (h : a = b) : myeq a b := by
  success_if_fail nontriviality α -- Fails
  nontriviality α using myeq -- There is now a `Nontrivial α` hypothesis available
  assumption

def Mathlib.Tactic.Nontriviality.elabNontriviality : Lean.Elab.Tactic.Tactic

Elaborator for the nontriviality tactic.