The normalizeScaleFn function uses nullish coalescing assignment (||=) to add default method implementations. However, this will not add the methods if they already exist but are falsy (like 0, false, ''). Consider using proper existence checks with in operator or checking for undefined specifically to avoid this edge case. For example: if (!('range' in out)) out.range = () => [];

The TransformLike type definition { data: T[] } & Record<string | symbol, any> is less specific than the standard TransformArg<T> type, which properly combines Channels<T> and BaseMarkProps<T>. This looser typing could allow invalid properties to pass through without type checking. Consider using the existing TransformArg<T> type instead, or if you need more flexibility, consider something like { data: T[] } & Partial<Channels<T> & BaseMarkProps<T>> & Record<string | symbol, any> to maintain better type safety while allowing additional properties.

The TransformLike type definition { data: T[] } & Record<string | symbol, any> is less specific than the standard TransformArg<T> type. This looser typing could allow invalid properties to pass through without type checking. Consider using the existing TransformArg<T> type instead, or if you need more flexibility, extend it properly to maintain type safety.

Consider adding step() method to the PlotScaleFunction type definition to avoid the need for this as unknown as ScaleBand cast. The step() method is commonly used with band scales and would make the type more complete. Alternatively, document that this cast is necessary for accessing scale-type-specific methods not included in the broad PlotScaleFunction interface.

Consider adding step(), paddingInner(), paddingOuter(), and other commonly-used band scale methods to the PlotScaleFunction type definition to reduce the need for type casts like this one throughout the codebase.

The BivariantCallback type is defined in both src/lib/types/index.ts and src/lib/types/channel.ts. This duplication should be avoided to maintain a single source of truth. Consider removing this definition from index.ts and importing it from channel.ts instead, or defining it once in a shared location and importing it in both places.

The useScale parameter in resolveStyles has type Record<ScaledChannelName, boolean>, which requires all scaled channel names to be present. However, callers are passing partial objects like { y: true } with an as any cast to work around this. Consider changing the type to Partial<Record<ScaledChannelName, boolean>> to make the API more flexible and eliminate the need for these type casts.