Documentation

Synthesize Contravariant (Stock1 F) — the contravariant instance of synthMap1.

The shared engine for the two single-parameter map-like classes over Stock1 F. fmap and contramap differ only in: the order of the two type variables in the method (forall a b vs forall a' a), the direction of the supplied function (a -> b vs a' -> a), and which varMap base case it feeds — so both are this one definition. The non-overridden method ((<$) resp. (>$), both at class-method index 1) comes from the class default; the field walk is the full variance recursion in varMap.

Synthesize Foldable (Stock1 F). foldMap maps the parameter fields and folds H a fields with their own foldMap, combining contributions with (<>) (constant fields contribute nothing); all other Foldable methods come from the class defaults. Nothing for unsupported field shapes.