control-union-distribution

TypeScript conditional types distribute over unions by default when the checked type is a bare type parameter, often producing surprising results that require explicit one-tuple wrappers to prevent.

To prevent union distribution in conditional types, wrap the checked type in a one-tuple form within the conditional check, which stops TypeScript from treating bare union types as distributive.

To force union distribution in TypeScript conditional types, use bare type parameters without wrapping them in tuples, which triggers the default distributive behavior over the union members.

Handle boolean and never edge cases in distributive conditional types by applying one-tuple wrappers to prevent unwanted distribution, ensuring recursive types do not misbehave during type-level evaluation.

The best way to control type distribution in advanced TypeScript type-level programming is toggling between bare conditions to force distribution and one-tuple wrappers to prevent it, handling boolean and never edge cases safely.