Type Alias AtCode<E, C>

AtCode: E extends TypedError<infer TC, infer M>
? C extends TC ? E & { code: C; info: M[C & keyof M] } : never
: never

E narrowed to code(s) C: code becomes C and info becomes the info map's payload for C. Distributes over both E and C, dropping union members of E that cannot carry C.