Lean4
/-- A type endowed with `*` is a left cancel semigroup, if it admits an injective map that
preserves `*` to a left cancel semigroup. See note [reducible non-instances]. -/
@[to_additive /-- A type endowed with `+` is an additive left cancel semigroup, if it admits an
injective map that preserves `+` to an additive left cancel semigroup. -/
]
protected abbrev leftCancelSemigroup [LeftCancelSemigroup M₂] (f : M₁ → M₂) (hf : Injective f)
(mul : ∀ x y, f (x * y) = f x * f y) : LeftCancelSemigroup M₁ :=
{ hf.semigroup f mul, hf.isLeftCancelMul f mul with }