type IsArr<T> = T extends `${string}...${string}` ? true : false
type Extract<T> = T extends `[...${infer F}]` | `...${infer F}` ? F : T

type DynamicRoute<T extends string, _Res extends Record<string, string | string[]> = {}> = T extends `${infer A}[...]${infer B}`
  ? DynamicRoute<`${A}${B}`, _Res & { '...': string }>
  : T extends `${string}]/[...${string}`
    ? never
      : T extends `${infer A}[[${ infer F }]]${ infer B }`
      ? DynamicRoute<`${A}${B}`, _Res & ( Extract<F> extends '' ? {} : { [K in Extract<F>]?: IsArr<F> extends true ? string[] : string } ) >
      : T extends `${infer A}[${ infer F }]${ infer B }`
        ? DynamicRoute<`${A}${B}`, _Res & ( Extract<F> extends '' ? {} : { [K in Extract<F>]: IsArr<F> extends true ? string[] : string } ) >
    : { [K in keyof _Res]: _Res[K] }

Solution by lvjiaxuan #33614

type DynamicRoute<T extends string, L extends string = '', O = {}, Ambiguity extends string = ''>
  = Ambiguity extends '⛔⛔' ? never
  : ExtractNext<T, L> extends [infer L extends string, infer S extends NonEmpty]
    ? S extends `[${infer P extends NonEmpty}]`
      ? P extends `[...${infer G extends NonEmpty}]` ? DynamicRoute<T, L, O & {[K in G]?: string[]}, `${Ambiguity}⛔`>
      : P extends `...${infer G extends NonEmpty}` ? DynamicRoute<T, L, O & {[K in G]: string[]}, `${Ambiguity}⛔`>
      : DynamicRoute<T, L, O & {[K in P]: string}, Ambiguity>
    : DynamicRoute<T, L, O, ''>
  : {[K in keyof O]: O[K]}

type ExtractNext<T extends string, L extends string = ''>
  = T extends `${L}/${infer S extends NonEmpty}/${any}` ? [`${L}/${S}/`, S]
  : T extends `${L}${infer S extends NonEmpty}/${any}` ? [`${L}${S}/`, S]
  : T extends `${L}/${infer S extends NonEmpty}` ? [`${L}/${S}`, S]
  : T extends `${L}${infer S extends NonEmpty}` ? [`${L}${S}`, S]
  : []

type NonEmpty = `${any}${any}`

Playground

Solution by teamchong #33350