Lean4
/-- An action of `M` on `α` and a function `N → M` induces an action of `N` on `α`. -/
-- See note [reducible non-instances]
-- Since this is reducible, we make sure to go via
-- `SMul.comp.smul` to prevent typeclass inference unfolding too far
@[to_additive /-- An additive action of `M` on `α` and a function `N → M` induces an additive
action of `N` on `α`. -/
]
abbrev comp (g : N → M) : SMul N α where smul := SMul.comp.smul g