From 8627010094eae1122d703b293f5629acf1b3632f Mon Sep 17 00:00:00 2001
From: Yusuke Wada <yusuke@kamawada.com>
Date: Sun, 23 Oct 2022 08:10:00 +0900
Subject: [PATCH] refactor(types): refactor and add tests for checking Types
 (#615)

* refactor(types): refactor and add tests for checking Types

* remove unused

* uncomment

* use `Handler` in validator middleware

* remove unused

* create `src/validator` dir and move some files into it

* add the case that the context is in `validator`

* rename `D` to `S`
---
 deno_dist/compose.ts                          |  14 +-
 deno_dist/context.ts                          |  47 +++----
 deno_dist/hono.ts                             | 122 ++++++++++--------
 .../middleware/serve-static/serve-static.ts   |   7 +-
 deno_dist/middleware/validator/middleware.ts  |  92 +++----------
 deno_dist/request.ts                          |  11 +-
 deno_dist/utils/types.ts                      |   5 +
 deno_dist/{middleware => }/validator/rule.ts  |   0
 .../{middleware => }/validator/sanitizer.ts   |   0
 deno_dist/validator/schema.ts                 |  54 ++++++++
 .../{middleware => }/validator/validator.ts   |   8 +-
 src/compose.ts                                |  14 +-
 src/context.ts                                |  47 +++----
 src/hono.test.ts                              |  66 +++++++++-
 src/hono.ts                                   | 122 ++++++++++--------
 src/middleware/serve-static/serve-static.ts   |   7 +-
 src/middleware/validator/middleware.test.ts   | 116 ++++++++++++++++-
 src/middleware/validator/middleware.ts        |  92 +++----------
 src/request.ts                                |  11 +-
 src/utils/types.ts                            |   5 +
 src/{middleware => }/validator/rule.test.ts   |   0
 src/{middleware => }/validator/rule.ts        |   0
 .../validator/sanitizer.test.ts               |   0
 src/{middleware => }/validator/sanitizer.ts   |   0
 src/validator/schema.ts                       |  54 ++++++++
 .../validator/validator.test.ts               |   2 +-
 src/{middleware => }/validator/validator.ts   |   8 +-
 tsconfig.build.cjs.json                       |   2 +
 tsconfig.build.json                           |   2 +
 tsconfig.json                                 |   4 +-
 30 files changed, 564 insertions(+), 348 deletions(-)
 create mode 100644 deno_dist/utils/types.ts
 rename deno_dist/{middleware => }/validator/rule.ts (100%)
 rename deno_dist/{middleware => }/validator/sanitizer.ts (100%)
 create mode 100644 deno_dist/validator/schema.ts
 rename deno_dist/{middleware => }/validator/validator.ts (98%)
 create mode 100644 src/utils/types.ts
 rename src/{middleware => }/validator/rule.test.ts (100%)
 rename src/{middleware => }/validator/rule.ts (100%)
 rename src/{middleware => }/validator/sanitizer.test.ts (100%)
 rename src/{middleware => }/validator/sanitizer.ts (100%)
 create mode 100644 src/validator/schema.ts
 rename src/{middleware => }/validator/validator.test.ts (99%)
 rename src/{middleware => }/validator/validator.ts (98%)

diff --git a/deno_dist/compose.ts b/deno_dist/compose.ts
index 3ac2c32c..aec2f014 100644
--- a/deno_dist/compose.ts
+++ b/deno_dist/compose.ts
@@ -1,16 +1,22 @@
 import { HonoContext } from './context.ts'
 import type { Environment, NotFoundHandler, ErrorHandler } from './hono.ts'
+import type { Schema } from './validator/schema.ts'
 
 interface ComposeContext {
   finalized: boolean
-  res: any
+  res: unknown
 }
 
 // Based on the code in the MIT licensed `koa-compose` package.
-export const compose = <C extends ComposeContext, E extends Partial<Environment> = Environment>(
+export const compose = <
+  C extends ComposeContext,
+  P extends string = string,
+  E extends Partial<Environment> = Environment,
+  D extends Partial<Schema> = Schema
+>(
   middleware: Function[],
-  onNotFound?: NotFoundHandler<E>,
-  onError?: ErrorHandler<E>
+  onNotFound?: NotFoundHandler<P, E, D>,
+  onError?: ErrorHandler<P, E, D>
 ) => {
   const middlewareLength = middleware.length
   return (context: C, next?: Function) => {
diff --git a/deno_dist/context.ts b/deno_dist/context.ts
index 3c95f282..41d38337 100644
--- a/deno_dist/context.ts
+++ b/deno_dist/context.ts
@@ -1,24 +1,19 @@
-import type {
-  Environment,
-  NotFoundHandler,
-  ContextVariableMap,
-  Bindings,
-  ValidatedData,
-} from './hono.ts'
+import type { Environment, NotFoundHandler, ContextVariableMap, Bindings } from './hono.ts'
 import type { CookieOptions } from './utils/cookie.ts'
 import { serialize } from './utils/cookie.ts'
 import type { StatusCode } from './utils/http-status.ts'
+import type { Schema, SchemaToProp } from './validator/schema.ts'
 
 type HeaderField = [string, string]
 type Headers = Record<string, string | string[]>
 export type Data = string | ArrayBuffer | ReadableStream
 
 export interface Context<
-  RequestParamKeyType extends string = string,
-  E extends Partial<Environment> = any,
-  D extends ValidatedData = ValidatedData
+  P extends string = string,
+  E extends Partial<Environment> = Environment,
+  S extends Partial<Schema> = Schema
 > {
-  req: Request<RequestParamKeyType, D>
+  req: Request<P, SchemaToProp<S>>
   env: E['Bindings']
   event: FetchEvent
   executionCtx: ExecutionContext
@@ -32,7 +27,7 @@ export interface Context<
   set: {
     <Key extends keyof ContextVariableMap>(key: Key, value: ContextVariableMap[Key]): void
     <Key extends keyof E['Variables']>(key: Key, value: E['Variables'][Key]): void
-    (key: string, value: any): void
+    (key: string, value: unknown): void
   }
   get: {
     <Key extends keyof ContextVariableMap>(key: Key): ContextVariableMap[Key]
@@ -51,12 +46,12 @@ export interface Context<
 }
 
 export class HonoContext<
-  RequestParamKeyType extends string = string,
+  P extends string = string,
   E extends Partial<Environment> = Environment,
-  D extends ValidatedData = ValidatedData
-> implements Context<RequestParamKeyType, E, D>
+  S extends Partial<Schema> = Schema
+> implements Context<P, E, S>
 {
-  req: Request<RequestParamKeyType, D>
+  req: Request<P, SchemaToProp<S>>
   env: E['Bindings']
   finalized: boolean
   error: Error | undefined = undefined
@@ -65,19 +60,19 @@ export class HonoContext<
   private _executionCtx: FetchEvent | ExecutionContext | undefined
   private _pretty: boolean = false
   private _prettySpace: number = 2
-  private _map: Record<string, any> | undefined
+  private _map: Record<string, unknown> | undefined
   private _headers: Record<string, string[]> | undefined
   private _res: Response | undefined
-  private notFoundHandler: NotFoundHandler<E>
+  private notFoundHandler: NotFoundHandler<P, E, S>
 
   constructor(
-    req: Request<RequestParamKeyType>,
-    env: E['Bindings'] | undefined = undefined,
+    req: Request<P>,
+    env: E['Bindings'] = {},
     executionCtx: FetchEvent | ExecutionContext | undefined = undefined,
-    notFoundHandler: NotFoundHandler<E> = () => new Response()
+    notFoundHandler: NotFoundHandler<P, E, S> = () => new Response()
   ) {
     this._executionCtx = executionCtx
-    this.req = req as Request<RequestParamKeyType, D>
+    this.req = req as Request<P, SchemaToProp<S>>
     this.env = env || ({} as Bindings)
 
     this.notFoundHandler = notFoundHandler
@@ -142,15 +137,15 @@ export class HonoContext<
 
   set<Key extends keyof ContextVariableMap>(key: Key, value: ContextVariableMap[Key]): void
   set<Key extends keyof E['Variables']>(key: Key, value: E['Variables'][Key]): void
-  set(key: string, value: any): void
-  set(key: string, value: any): void {
+  set(key: string, value: unknown): void
+  set(key: string, value: unknown): void {
     this._map ||= {}
     this._map[key] = value
   }
 
   get<Key extends keyof ContextVariableMap>(key: Key): ContextVariableMap[Key]
   get<Key extends keyof E['Variables']>(key: Key): E['Variables'][Key]
-  get<T = any>(key: string): T
+  get<T>(key: string): T
   get(key: string) {
     if (!this._map) {
       return undefined
@@ -233,6 +228,6 @@ export class HonoContext<
   }
 
   notFound(): Response | Promise<Response> {
-    return this.notFoundHandler(this as any)
+    return this.notFoundHandler(this)
   }
 }
diff --git a/deno_dist/hono.ts b/deno_dist/hono.ts
index ec59003e..470efaa9 100644
--- a/deno_dist/hono.ts
+++ b/deno_dist/hono.ts
@@ -10,6 +10,7 @@ import { SmartRouter } from './router/smart-router/index.ts'
 import { StaticRouter } from './router/static-router/index.ts'
 import { TrieRouter } from './router/trie-router/index.ts'
 import { getPathFromURL, mergePath } from './utils/url.ts'
+import type { Schema } from './validator/schema.ts'
 
 export interface ContextVariableMap {}
 
@@ -20,30 +21,29 @@ export type Environment = {
   Variables: Variables
 }
 
-export type ValidatedData = Record<string, any> // For validated data
-
 export type Handler<
-  RequestParamKeyType extends string = string,
+  P extends string = string,
   E extends Partial<Environment> = Environment,
-  D extends ValidatedData = ValidatedData
-> = (
-  c: Context<RequestParamKeyType, E, D>,
-  next: Next
-) => Response | Promise<Response> | Promise<void> | Promise<Response | undefined | void>
+  S extends Partial<Schema> = Schema
+> = (c: Context<P, E, S>, next: Next) => Response | Promise<Response | undefined | void>
 
-export type MiddlewareHandler = <E extends Partial<Environment> = Environment>(
-  c: Context<string, E>,
-  next: Next
-) => Promise<void> | Promise<Response | undefined>
+export type MiddlewareHandler<
+  P extends string = string,
+  E extends Partial<Environment> = Environment,
+  S extends Partial<Schema> = Schema
+> = (c: Context<P, E, S>, next: Next) => Promise<Response | undefined | void>
 
-export type NotFoundHandler<E extends Partial<Environment> = Environment> = (
-  c: Context<string, E>
-) => Response | Promise<Response>
+export type NotFoundHandler<
+  P extends string = string,
+  E extends Partial<Environment> = Environment,
+  S extends Partial<Schema> = Schema
+> = (c: Context<P, E, S>) => Response | Promise<Response>
 
-export type ErrorHandler<E extends Partial<Environment> = Environment> = (
-  err: Error,
-  c: Context<string, E>
-) => Response
+export type ErrorHandler<
+  P extends string = string,
+  E extends Partial<Environment> = Environment,
+  S extends Partial<Schema> = Schema
+> = (err: Error, c: Context<P, E, S>) => Response
 
 export type Next = () => Promise<void>
 
@@ -60,52 +60,65 @@ type ParamKeys<Path> = Path extends `${infer Component}/${infer Rest}`
   ? ParamKey<Component> | ParamKeys<Rest>
   : ParamKey<Path>
 
-interface HandlerInterface<T extends string, E extends Partial<Environment>, U = Hono<E, T>> {
+interface HandlerInterface<
+  P extends string,
+  E extends Partial<Environment>,
+  S extends Partial<Schema>,
+  U = Hono<E, P, S>
+> {
   // app.get(handler...)
-  <Path extends string, Data extends ValidatedData>(
+  <Path extends string, Data extends Schema>(
     ...handlers: Handler<ParamKeys<Path> extends never ? string : ParamKeys<Path>, E, Data>[]
   ): U
-  (...handlers: Handler<string, E>[]): U
+  (...handlers: Handler<string, E, S>[]): U
+
   // app.get('/', handler, handler...)
-  <Path extends string, Data extends ValidatedData>(
+  <Path extends string, Data extends Partial<Schema> = Schema>(
     path: Path,
     ...handlers: Handler<ParamKeys<Path> extends never ? string : ParamKeys<Path>, E, Data>[]
   ): U
-  (path: string, ...handlers: Handler<string, E>[]): U
+  <Path extends string, Data extends Schema>(path: Path, ...handlers: Handler<string, E, Data>[]): U
+  (path: string, ...handlers: Handler<string, E, S>[]): U
 }
 
 type Methods = typeof METHODS[number] | typeof METHOD_NAME_ALL_LOWERCASE
 
 function defineDynamicClass(): {
-  new <E extends Partial<Environment> = Environment, T extends string = string, U = Hono<E, T>>(): {
-    [K in Methods]: HandlerInterface<T, E, U>
+  new <
+    E extends Partial<Environment> = Environment,
+    P extends string = string,
+    S extends Partial<Schema> = Schema,
+    U = Hono<E, P, S>
+  >(): {
+    [K in Methods]: HandlerInterface<P, E, S, U>
   }
 } {
-  return class {} as any
+  return class {} as never
 }
 
 interface Route<
+  P extends string = string,
   E extends Partial<Environment> = Environment,
-  D extends ValidatedData = ValidatedData
+  S extends Partial<Schema> = Schema
 > {
   path: string
   method: string
-  handler: Handler<string, E, D>
+  handler: Handler<P, E, S>
 }
 
 export class Hono<
   E extends Partial<Environment> = Environment,
   P extends string = '/',
-  D extends ValidatedData = ValidatedData
-> extends defineDynamicClass()<E, P, Hono<E, P, D>> {
-  readonly router: Router<Handler<string, E, D>> = new SmartRouter({
+  S extends Partial<Schema> = Schema
+> extends defineDynamicClass()<E, P, S, Hono<E, P, S>> {
+  readonly router: Router<Handler<P, E, S>> = new SmartRouter({
     routers: [new StaticRouter(), new RegExpRouter(), new TrieRouter()],
   })
   readonly strict: boolean = true // strict routing - default is true
   private _tempPath: string = ''
   private path: string = '/'
 
-  routes: Route<E, D>[] = []
+  routes: Route<P, E, S>[] = []
 
   constructor(init: Partial<Pick<Hono, 'router' | 'strict'>> = {}) {
     super()
@@ -114,18 +127,18 @@ export class Hono<
 
     const allMethods = [...METHODS, METHOD_NAME_ALL_LOWERCASE]
     allMethods.map((method) => {
-      this[method] = <Path extends string = ''>(
-        args1: Path | Handler<ParamKeys<Path>, E, D>,
-        ...args: [Handler<ParamKeys<Path>, E, D>]
+      this[method] = <Path extends string, Env extends Environment, Data extends Schema>(
+        args1: Path | Handler<ParamKeys<Path>, Env, Data>,
+        ...args: [Handler<ParamKeys<Path>, Env, Data>]
       ): this => {
         if (typeof args1 === 'string') {
           this.path = args1
         } else {
-          this.addRoute(method, this.path, args1)
+          this.addRoute(method, this.path, args1 as unknown as Handler<P, E, S>)
         }
         args.map((handler) => {
           if (typeof handler !== 'string') {
-            this.addRoute(method, this.path, handler)
+            this.addRoute(method, this.path, handler as unknown as Handler<P, E, S>)
           }
         })
         return this
@@ -135,17 +148,17 @@ export class Hono<
     Object.assign(this, init)
   }
 
-  private notFoundHandler: NotFoundHandler<E> = (c: Context<string, E>) => {
+  private notFoundHandler: NotFoundHandler<P, E, S> = (c: Context<P, E, S>) => {
     return c.text('404 Not Found', 404)
   }
 
-  private errorHandler: ErrorHandler<E> = (err: Error, c: Context<string, E>) => {
+  private errorHandler: ErrorHandler<P, E, S> = (err: Error, c: Context<P, E, S>) => {
     console.trace(err.message)
     const message = 'Internal Server Error'
     return c.text(message, 500)
   }
 
-  route(path: string, app?: Hono<any>): Hono<E, P, D> {
+  route(path: string, app?: Hono<E, P, S>) {
     this._tempPath = path
     if (app) {
       app.routes.map((r) => {
@@ -153,18 +166,17 @@ export class Hono<
       })
       this._tempPath = ''
     }
-
     return this
   }
 
-  use<Path extends string = string, Data extends ValidatedData = D>(
+  use<Path extends string = string, Data extends Partial<Schema> = Schema>(
     ...middleware: Handler<Path, E, Data>[]
-  ): Hono<E, Path, Data>
-  use<Path extends string = string, Data extends ValidatedData = D>(
+  ): Hono<E, Path, S>
+  use<Path extends string = string, Data extends Partial<Schema> = Schema>(
     arg1: string,
     ...middleware: Handler<Path, E, Data>[]
-  ): Hono<E, Path, D>
-  use(arg1: string | Handler<string, E, D>, ...handlers: Handler<string, E, D>[]): Hono<E, P, D> {
+  ): Hono<E, Path, S>
+  use(arg1: string | Handler<P, E, S>, ...handlers: Handler<P, E, S>[]) {
     if (typeof arg1 === 'string') {
       this.path = arg1
     } else {
@@ -176,23 +188,23 @@ export class Hono<
     return this
   }
 
-  onError(handler: ErrorHandler<E>): Hono<E, P, D> {
+  onError(handler: ErrorHandler<P, E, S>) {
     this.errorHandler = handler
     return this
   }
 
-  notFound(handler: NotFoundHandler<E>): Hono<E, P, D> {
+  notFound(handler: NotFoundHandler<P, E, S>) {
     this.notFoundHandler = handler
     return this
   }
 
-  private addRoute(method: string, path: string, handler: Handler<string, E, D>): void {
+  private addRoute(method: string, path: string, handler: Handler<P, E, S>): void {
     method = method.toUpperCase()
     if (this._tempPath) {
       path = mergePath(this._tempPath, path)
     }
     this.router.add(method, path, handler)
-    const r: Route<E, D> = { path: path, method: method, handler: handler }
+    const r: Route<P, E, S> = { path: path, method: method, handler: handler }
     this.routes.push(r)
   }
 
@@ -200,7 +212,7 @@ export class Hono<
     return this.router.match(method, path)
   }
 
-  private handleError(err: unknown, c: Context) {
+  private handleError(err: unknown, c: Context<P, E, S>) {
     if (err instanceof Error) {
       return this.errorHandler(err, c)
     }
@@ -218,12 +230,12 @@ export class Hono<
     const result = this.matchRoute(method, path)
     request.paramData = result?.params
 
-    const c = new HonoContext<string, E, D>(request, env, eventOrExecutionCtx, this.notFoundHandler)
+    const c = new HonoContext<P, E, S>(request, env, eventOrExecutionCtx, this.notFoundHandler)
 
     // Do not `compose` if it has only one handler
     if (result && result.handlers.length === 1) {
       const handler = result.handlers[0]
-      let res: ReturnType<Handler>
+      let res: ReturnType<Handler<P>>
 
       try {
         res = handler(c, async () => {})
@@ -249,7 +261,7 @@ export class Hono<
     }
 
     const handlers = result ? result.handlers : [this.notFoundHandler]
-    const composed = compose<HonoContext<string, E>, E>(
+    const composed = compose<HonoContext<P, E, S>, P, E, S>(
       handlers,
       this.notFoundHandler,
       this.errorHandler
diff --git a/deno_dist/middleware/serve-static/serve-static.ts b/deno_dist/middleware/serve-static/serve-static.ts
index 51cdcaa1..451921cf 100644
--- a/deno_dist/middleware/serve-static/serve-static.ts
+++ b/deno_dist/middleware/serve-static/serve-static.ts
@@ -1,5 +1,4 @@
-import type { Context } from '../../context.ts'
-import type { Next } from '../../hono.ts'
+import type { MiddlewareHandler } from '../../hono.ts'
 import { getContentFromKVAsset } from '../../utils/cloudflare.ts'
 import { getFilePath } from '../../utils/filepath.ts'
 import { getMimeType } from '../../utils/mime.ts'
@@ -14,8 +13,8 @@ export type ServeStaticOptions = {
 const DEFAULT_DOCUMENT = 'index.html'
 
 // This middleware is available only on Cloudflare Workers.
-export const serveStatic = (options: ServeStaticOptions = { root: '' }) => {
-  return async (c: Context, next: Next) => {
+export const serveStatic = (options: ServeStaticOptions = { root: '' }): MiddlewareHandler => {
+  return async (c, next) => {
     // Do nothing if Response is already set
     if (c.finalized) {
       await next()
diff --git a/deno_dist/middleware/validator/middleware.ts b/deno_dist/middleware/validator/middleware.ts
index a89aa9b9..88cb8eb2 100644
--- a/deno_dist/middleware/validator/middleware.ts
+++ b/deno_dist/middleware/validator/middleware.ts
@@ -1,62 +1,10 @@
 import type { Context } from '../../context.ts'
-import type { Environment, Next, ValidatedData } from '../../hono.ts'
+import type { Environment, MiddlewareHandler } from '../../hono.ts'
 import { getStatusText } from '../../utils/http-status.ts'
 import { mergeObjects } from '../../utils/object.ts'
-import { VBase, Validator, VObjectBase } from './validator.ts'
-import type {
-  VString,
-  VNumber,
-  VBoolean,
-  VObject,
-  VNumberArray,
-  VStringArray,
-  VBooleanArray,
-  ValidateResult,
-  VArray,
-} from './validator.ts'
-
-export type Schema = {
-  [key: string]:
-    | VString
-    | VNumber
-    | VBoolean
-    | VStringArray
-    | VNumberArray
-    | VBooleanArray
-    | Schema
-    | VObject<Schema>
-    | VArray<Schema>
-}
-
-type SchemaToProp<T> = {
-  [K in keyof T]: T[K] extends VNumberArray
-    ? number[]
-    : T[K] extends VBooleanArray
-    ? boolean[]
-    : T[K] extends VStringArray
-    ? string[]
-    : T[K] extends VNumber
-    ? number
-    : T[K] extends VBoolean
-    ? boolean
-    : T[K] extends VString
-    ? string
-    : T[K] extends VObjectBase<Schema>
-    ? T[K]['container'] extends VNumber
-      ? number
-      : T[K]['container'] extends VString
-      ? string
-      : T[K]['container'] extends VBoolean
-      ? boolean
-      : T[K] extends VArray<Schema>
-      ? SchemaToProp<ReadonlyArray<T[K]['container']>>
-      : T[K] extends VObject<Schema>
-      ? SchemaToProp<T[K]['container']>
-      : T[K] extends Schema
-      ? SchemaToProp<T[K]>
-      : never
-    : SchemaToProp<T[K]>
-}
+import type { Schema } from '../../validator/schema.ts'
+import type { ValidateResult } from '../../validator/validator.ts'
+import { Validator, VBase, VObjectBase } from '../../validator/validator.ts'
 
 type ResultSet = {
   hasError: boolean
@@ -64,27 +12,27 @@ type ResultSet = {
   results: ValidateResult[]
 }
 
-type Done<Env extends Partial<Environment>> = (
+type Done<P extends string, E extends Partial<Environment> = Environment> = (
   resultSet: ResultSet,
-  context: Context<string, Env>
+  c: Context<P, E>
 ) => Response | void
 
-type ValidationFunction<T, Env extends Partial<Environment>> = (
-  v: Validator,
-  c: Context<string, Env>
-) => T
+type ValidationFunction<
+  P extends string,
+  E extends Partial<Environment> = Environment,
+  S extends Schema = Schema
+> = (v: Validator, c: Context<P, E>) => S
 
-type MiddlewareHandler<
-  Data extends ValidatedData = ValidatedData,
-  Env extends Partial<Environment> = Environment
-> = (c: Context<string, Env, Data>, next: Next) => Promise<void> | Promise<Response | undefined>
-
-export const validatorMiddleware = <T extends Schema, Env extends Partial<Environment>>(
-  validationFunction: ValidationFunction<T, Env>,
-  options?: { done?: Done<Env> }
+export const validatorMiddleware = <
+  P extends string,
+  E extends Partial<Environment> = Environment,
+  S extends Schema = Schema
+>(
+  validationFunction: ValidationFunction<P, E, S>,
+  options?: { done?: Done<P, E> }
 ) => {
   const v = new Validator()
-  const handler: MiddlewareHandler<SchemaToProp<T>, Env> = async (c, next) => {
+  const handler: MiddlewareHandler<string, E, S> = async (c, next) => {
     const resultSet: ResultSet = {
       hasError: false,
       messages: [],
@@ -98,7 +46,7 @@ export const validatorMiddleware = <T extends Schema, Env extends Partial<Enviro
     for (const [keys, validator] of validatorList) {
       let results: ValidateResult[]
       try {
-        results = await validator.validate(c.req)
+        results = await validator.validate(c.req as Request)
       } catch (e) {
         // Invalid JSON request
         return c.text(getStatusText(400), 400)
diff --git a/deno_dist/request.ts b/deno_dist/request.ts
index 7aa82ed6..9eb3dbf3 100644
--- a/deno_dist/request.ts
+++ b/deno_dist/request.ts
@@ -36,11 +36,12 @@ declare global {
     }
     bodyData?: BodyData
     parseBody<BodyType extends BodyData>(): Promise<BodyType>
+    // eslint-disable-next-line @typescript-eslint/no-explicit-any
     jsonData?: any
-    json<JSONData = any>(): Promise<JSONData>
+    json<JSONData = unknown>(): Promise<Partial<JSONData>>
     data: Data
     valid: {
-      (key: string | string[], value: any): Data
+      (key: string | string[], value: unknown): Data
       (): Data
     }
   }
@@ -132,9 +133,9 @@ export function extendRequestPrototype() {
     return body
   } as InstanceType<typeof Request>['parseBody']
 
-  Request.prototype.json = async function <JSONData>(this: Request): Promise<JSONData> {
+  Request.prototype.json = async function <JSONData = unknown>(this: Request) {
     // Cache the JSON body
-    let jsonData: JSONData
+    let jsonData: Partial<JSONData>
     if (!this.jsonData) {
       jsonData = JSON.parse(await this.text())
       this.jsonData = jsonData
@@ -144,7 +145,7 @@ export function extendRequestPrototype() {
     return jsonData
   } as InstanceType<typeof Request>['jsonData']
 
-  Request.prototype.valid = function (this: Request, keys?: string | string[], value?: any) {
+  Request.prototype.valid = function (this: Request, keys?: string | string[], value?: unknown) {
     if (!this.data) {
       this.data = {}
     }
diff --git a/deno_dist/utils/types.ts b/deno_dist/utils/types.ts
new file mode 100644
index 00000000..a61550ba
--- /dev/null
+++ b/deno_dist/utils/types.ts
@@ -0,0 +1,5 @@
+export type Expect<T extends true> = T
+export type Equal<X, Y> = (<T>() => T extends X ? 1 : 2) extends <T>() => T extends Y ? 1 : 2
+  ? true
+  : false
+export type NotEqual<X, Y> = true extends Equal<X, Y> ? false : true
diff --git a/deno_dist/middleware/validator/rule.ts b/deno_dist/validator/rule.ts
similarity index 100%
rename from deno_dist/middleware/validator/rule.ts
rename to deno_dist/validator/rule.ts
diff --git a/deno_dist/middleware/validator/sanitizer.ts b/deno_dist/validator/sanitizer.ts
similarity index 100%
rename from deno_dist/middleware/validator/sanitizer.ts
rename to deno_dist/validator/sanitizer.ts
diff --git a/deno_dist/validator/schema.ts b/deno_dist/validator/schema.ts
new file mode 100644
index 00000000..3fc024ac
--- /dev/null
+++ b/deno_dist/validator/schema.ts
@@ -0,0 +1,54 @@
+import type {
+  VString,
+  VNumber,
+  VBoolean,
+  VObject,
+  VNumberArray,
+  VStringArray,
+  VBooleanArray,
+  VArray,
+  VObjectBase,
+} from './validator.ts'
+
+export type Schema = {
+  [key: string]:
+    | VString
+    | VNumber
+    | VBoolean
+    | VStringArray
+    | VNumberArray
+    | VBooleanArray
+    | Schema
+    | VObject<Schema>
+    | VArray<Schema>
+}
+
+export type SchemaToProp<T> = {
+  [K in keyof T]: T[K] extends VNumberArray
+    ? number[]
+    : T[K] extends VBooleanArray
+    ? boolean[]
+    : T[K] extends VStringArray
+    ? string[]
+    : T[K] extends VNumber
+    ? number
+    : T[K] extends VBoolean
+    ? boolean
+    : T[K] extends VString
+    ? string
+    : T[K] extends VObjectBase<Schema>
+    ? T[K]['container'] extends VNumber
+      ? number
+      : T[K]['container'] extends VString
+      ? string
+      : T[K]['container'] extends VBoolean
+      ? boolean
+      : T[K] extends VArray<Schema>
+      ? SchemaToProp<ReadonlyArray<T[K]['container']>>
+      : T[K] extends VObject<Schema>
+      ? SchemaToProp<T[K]['container']>
+      : T[K] extends Schema
+      ? SchemaToProp<T[K]>
+      : never
+    : SchemaToProp<T[K]>
+}
diff --git a/deno_dist/middleware/validator/validator.ts b/deno_dist/validator/validator.ts
similarity index 98%
rename from deno_dist/middleware/validator/validator.ts
rename to deno_dist/validator/validator.ts
index 87b69bfa..4268b96d 100644
--- a/deno_dist/middleware/validator/validator.ts
+++ b/deno_dist/validator/validator.ts
@@ -1,8 +1,8 @@
-import { JSONPathCopy } from '../../utils/json.ts'
-import type { JSONObject, JSONPrimitive, JSONArray } from '../../utils/json.ts'
-import type { Schema } from './middleware.ts'
+import { JSONPathCopy } from './../utils/json.ts'
+import type { JSONObject, JSONPrimitive, JSONArray } from './../utils/json.ts'
 import { rule } from './rule.ts'
 import { sanitizer } from './sanitizer.ts'
+import type { Schema } from './schema.ts'
 
 type Target = 'query' | 'header' | 'body' | 'json'
 type Type = JSONPrimitive | JSONObject | JSONArray | File
@@ -209,7 +209,7 @@ export abstract class VBase {
     return this
   }
 
-  validate = async (req: Request): Promise<ValidateResult[]> => {
+  validate = async <R extends Request>(req: R): Promise<ValidateResult[]> => {
     let value: Type = undefined
     let jsonData: JSONObject | undefined = undefined
 
diff --git a/src/compose.ts b/src/compose.ts
index cc037c4a..55b876b5 100644
--- a/src/compose.ts
+++ b/src/compose.ts
@@ -1,16 +1,22 @@
 import { HonoContext } from './context'
 import type { Environment, NotFoundHandler, ErrorHandler } from './hono'
+import type { Schema } from './validator/schema'
 
 interface ComposeContext {
   finalized: boolean
-  res: any
+  res: unknown
 }
 
 // Based on the code in the MIT licensed `koa-compose` package.
-export const compose = <C extends ComposeContext, E extends Partial<Environment> = Environment>(
+export const compose = <
+  C extends ComposeContext,
+  P extends string = string,
+  E extends Partial<Environment> = Environment,
+  D extends Partial<Schema> = Schema
+>(
   middleware: Function[],
-  onNotFound?: NotFoundHandler<E>,
-  onError?: ErrorHandler<E>
+  onNotFound?: NotFoundHandler<P, E, D>,
+  onError?: ErrorHandler<P, E, D>
 ) => {
   const middlewareLength = middleware.length
   return (context: C, next?: Function) => {
diff --git a/src/context.ts b/src/context.ts
index 37a9cd46..bff4d2f0 100644
--- a/src/context.ts
+++ b/src/context.ts
@@ -1,24 +1,19 @@
-import type {
-  Environment,
-  NotFoundHandler,
-  ContextVariableMap,
-  Bindings,
-  ValidatedData,
-} from './hono'
+import type { Environment, NotFoundHandler, ContextVariableMap, Bindings } from './hono'
 import type { CookieOptions } from './utils/cookie'
 import { serialize } from './utils/cookie'
 import type { StatusCode } from './utils/http-status'
+import type { Schema, SchemaToProp } from './validator/schema'
 
 type HeaderField = [string, string]
 type Headers = Record<string, string | string[]>
 export type Data = string | ArrayBuffer | ReadableStream
 
 export interface Context<
-  RequestParamKeyType extends string = string,
-  E extends Partial<Environment> = any,
-  D extends ValidatedData = ValidatedData
+  P extends string = string,
+  E extends Partial<Environment> = Environment,
+  S extends Partial<Schema> = Schema
 > {
-  req: Request<RequestParamKeyType, D>
+  req: Request<P, SchemaToProp<S>>
   env: E['Bindings']
   event: FetchEvent
   executionCtx: ExecutionContext
@@ -32,7 +27,7 @@ export interface Context<
   set: {
     <Key extends keyof ContextVariableMap>(key: Key, value: ContextVariableMap[Key]): void
     <Key extends keyof E['Variables']>(key: Key, value: E['Variables'][Key]): void
-    (key: string, value: any): void
+    (key: string, value: unknown): void
   }
   get: {
     <Key extends keyof ContextVariableMap>(key: Key): ContextVariableMap[Key]
@@ -51,12 +46,12 @@ export interface Context<
 }
 
 export class HonoContext<
-  RequestParamKeyType extends string = string,
+  P extends string = string,
   E extends Partial<Environment> = Environment,
-  D extends ValidatedData = ValidatedData
-> implements Context<RequestParamKeyType, E, D>
+  S extends Partial<Schema> = Schema
+> implements Context<P, E, S>
 {
-  req: Request<RequestParamKeyType, D>
+  req: Request<P, SchemaToProp<S>>
   env: E['Bindings']
   finalized: boolean
   error: Error | undefined = undefined
@@ -65,19 +60,19 @@ export class HonoContext<
   private _executionCtx: FetchEvent | ExecutionContext | undefined
   private _pretty: boolean = false
   private _prettySpace: number = 2
-  private _map: Record<string, any> | undefined
+  private _map: Record<string, unknown> | undefined
   private _headers: Record<string, string[]> | undefined
   private _res: Response | undefined
-  private notFoundHandler: NotFoundHandler<E>
+  private notFoundHandler: NotFoundHandler<P, E, S>
 
   constructor(
-    req: Request<RequestParamKeyType>,
-    env: E['Bindings'] | undefined = undefined,
+    req: Request<P>,
+    env: E['Bindings'] = {},
     executionCtx: FetchEvent | ExecutionContext | undefined = undefined,
-    notFoundHandler: NotFoundHandler<E> = () => new Response()
+    notFoundHandler: NotFoundHandler<P, E, S> = () => new Response()
   ) {
     this._executionCtx = executionCtx
-    this.req = req as Request<RequestParamKeyType, D>
+    this.req = req as Request<P, SchemaToProp<S>>
     this.env = env || ({} as Bindings)
 
     this.notFoundHandler = notFoundHandler
@@ -142,15 +137,15 @@ export class HonoContext<
 
   set<Key extends keyof ContextVariableMap>(key: Key, value: ContextVariableMap[Key]): void
   set<Key extends keyof E['Variables']>(key: Key, value: E['Variables'][Key]): void
-  set(key: string, value: any): void
-  set(key: string, value: any): void {
+  set(key: string, value: unknown): void
+  set(key: string, value: unknown): void {
     this._map ||= {}
     this._map[key] = value
   }
 
   get<Key extends keyof ContextVariableMap>(key: Key): ContextVariableMap[Key]
   get<Key extends keyof E['Variables']>(key: Key): E['Variables'][Key]
-  get<T = any>(key: string): T
+  get<T>(key: string): T
   get(key: string) {
     if (!this._map) {
       return undefined
@@ -233,6 +228,6 @@ export class HonoContext<
   }
 
   notFound(): Response | Promise<Response> {
-    return this.notFoundHandler(this as any)
+    return this.notFoundHandler(this)
   }
 }
diff --git a/src/hono.test.ts b/src/hono.test.ts
index 0bf0615a..a439ba73 100644
--- a/src/hono.test.ts
+++ b/src/hono.test.ts
@@ -1,8 +1,10 @@
+/* eslint-disable @typescript-eslint/no-unused-vars */
 import type { Context } from './context'
-import type { Next } from './hono'
+import type { Handler, Next } from './hono'
 import { Hono } from './hono'
 import { logger } from './middleware/logger'
 import { poweredBy } from './middleware/powered-by'
+import type { Expect, Equal } from './utils/types'
 
 describe('GET Request', () => {
   const app = new Hono()
@@ -1137,3 +1139,65 @@ describe('Count of logger called', () => {
     expect(log).toMatch(/404/)
   })
 })
+
+describe('Context set/get variables', () => {
+  type Variables = {
+    id: number
+    title: string
+  }
+
+  const app = new Hono<{ Variables: Variables }>()
+
+  it('Should set and get variables with correct types', async () => {
+    app.use('*', async (c, next) => {
+      c.set('id', 123)
+      c.set('title', 'Hello')
+      await next()
+    })
+    app.get('/', (c) => {
+      const id = c.get('id')
+      const title = c.get('title')
+      type verifyID = Expect<Equal<typeof id, number>>
+      type verifyTitle = Expect<Equal<typeof title, string>>
+      return c.text(`${id} is ${title}`)
+    })
+    const res = await app.request('http://localhost/')
+    expect(res.status).toBe(200)
+    expect(await res.text()).toBe('123 is Hello')
+  })
+})
+
+describe('Context binding variables', () => {
+  type Bindings = {
+    USER_ID: number
+    USER_NAME: string
+  }
+
+  const app = new Hono<{ Bindings: Bindings }>()
+
+  it('Should get binding variables with correct types', async () => {
+    app.get('/', (c) => {
+      type verifyID = Expect<Equal<typeof c.env.USER_ID, number>>
+      type verifyName = Expect<Equal<typeof c.env.USER_NAME, string>>
+      return c.text('These are verified')
+    })
+    const res = await app.request('http://localhost/')
+    expect(res.status).toBe(200)
+  })
+})
+
+describe('Handler as variables', () => {
+  const app = new Hono()
+
+  it('Should be typed correctly', async () => {
+    const handler: Handler = (c) => {
+      const id = c.req.param('id')
+      return c.text(`Post id is ${id}`)
+    }
+    app.get('/posts/:id', handler)
+
+    const res = await app.request('http://localhost/posts/123')
+    expect(res.status).toBe(200)
+    expect(await res.text()).toBe('Post id is 123')
+  })
+})
diff --git a/src/hono.ts b/src/hono.ts
index ec3541d2..64a0cba7 100644
--- a/src/hono.ts
+++ b/src/hono.ts
@@ -10,6 +10,7 @@ import { SmartRouter } from './router/smart-router'
 import { StaticRouter } from './router/static-router'
 import { TrieRouter } from './router/trie-router'
 import { getPathFromURL, mergePath } from './utils/url'
+import type { Schema } from './validator/schema'
 
 export interface ContextVariableMap {}
 
@@ -20,30 +21,29 @@ export type Environment = {
   Variables: Variables
 }
 
-export type ValidatedData = Record<string, any> // For validated data
-
 export type Handler<
-  RequestParamKeyType extends string = string,
+  P extends string = string,
   E extends Partial<Environment> = Environment,
-  D extends ValidatedData = ValidatedData
-> = (
-  c: Context<RequestParamKeyType, E, D>,
-  next: Next
-) => Response | Promise<Response> | Promise<void> | Promise<Response | undefined | void>
+  S extends Partial<Schema> = Schema
+> = (c: Context<P, E, S>, next: Next) => Response | Promise<Response | undefined | void>
 
-export type MiddlewareHandler = <E extends Partial<Environment> = Environment>(
-  c: Context<string, E>,
-  next: Next
-) => Promise<void> | Promise<Response | undefined>
+export type MiddlewareHandler<
+  P extends string = string,
+  E extends Partial<Environment> = Environment,
+  S extends Partial<Schema> = Schema
+> = (c: Context<P, E, S>, next: Next) => Promise<Response | undefined | void>
 
-export type NotFoundHandler<E extends Partial<Environment> = Environment> = (
-  c: Context<string, E>
-) => Response | Promise<Response>
+export type NotFoundHandler<
+  P extends string = string,
+  E extends Partial<Environment> = Environment,
+  S extends Partial<Schema> = Schema
+> = (c: Context<P, E, S>) => Response | Promise<Response>
 
-export type ErrorHandler<E extends Partial<Environment> = Environment> = (
-  err: Error,
-  c: Context<string, E>
-) => Response
+export type ErrorHandler<
+  P extends string = string,
+  E extends Partial<Environment> = Environment,
+  S extends Partial<Schema> = Schema
+> = (err: Error, c: Context<P, E, S>) => Response
 
 export type Next = () => Promise<void>
 
@@ -60,52 +60,65 @@ type ParamKeys<Path> = Path extends `${infer Component}/${infer Rest}`
   ? ParamKey<Component> | ParamKeys<Rest>
   : ParamKey<Path>
 
-interface HandlerInterface<T extends string, E extends Partial<Environment>, U = Hono<E, T>> {
+interface HandlerInterface<
+  P extends string,
+  E extends Partial<Environment>,
+  S extends Partial<Schema>,
+  U = Hono<E, P, S>
+> {
   // app.get(handler...)
-  <Path extends string, Data extends ValidatedData>(
+  <Path extends string, Data extends Schema>(
     ...handlers: Handler<ParamKeys<Path> extends never ? string : ParamKeys<Path>, E, Data>[]
   ): U
-  (...handlers: Handler<string, E>[]): U
+  (...handlers: Handler<string, E, S>[]): U
+
   // app.get('/', handler, handler...)
-  <Path extends string, Data extends ValidatedData>(
+  <Path extends string, Data extends Partial<Schema> = Schema>(
     path: Path,
     ...handlers: Handler<ParamKeys<Path> extends never ? string : ParamKeys<Path>, E, Data>[]
   ): U
-  (path: string, ...handlers: Handler<string, E>[]): U
+  <Path extends string, Data extends Schema>(path: Path, ...handlers: Handler<string, E, Data>[]): U
+  (path: string, ...handlers: Handler<string, E, S>[]): U
 }
 
 type Methods = typeof METHODS[number] | typeof METHOD_NAME_ALL_LOWERCASE
 
 function defineDynamicClass(): {
-  new <E extends Partial<Environment> = Environment, T extends string = string, U = Hono<E, T>>(): {
-    [K in Methods]: HandlerInterface<T, E, U>
+  new <
+    E extends Partial<Environment> = Environment,
+    P extends string = string,
+    S extends Partial<Schema> = Schema,
+    U = Hono<E, P, S>
+  >(): {
+    [K in Methods]: HandlerInterface<P, E, S, U>
   }
 } {
-  return class {} as any
+  return class {} as never
 }
 
 interface Route<
+  P extends string = string,
   E extends Partial<Environment> = Environment,
-  D extends ValidatedData = ValidatedData
+  S extends Partial<Schema> = Schema
 > {
   path: string
   method: string
-  handler: Handler<string, E, D>
+  handler: Handler<P, E, S>
 }
 
 export class Hono<
   E extends Partial<Environment> = Environment,
   P extends string = '/',
-  D extends ValidatedData = ValidatedData
-> extends defineDynamicClass()<E, P, Hono<E, P, D>> {
-  readonly router: Router<Handler<string, E, D>> = new SmartRouter({
+  S extends Partial<Schema> = Schema
+> extends defineDynamicClass()<E, P, S, Hono<E, P, S>> {
+  readonly router: Router<Handler<P, E, S>> = new SmartRouter({
     routers: [new StaticRouter(), new RegExpRouter(), new TrieRouter()],
   })
   readonly strict: boolean = true // strict routing - default is true
   private _tempPath: string = ''
   private path: string = '/'
 
-  routes: Route<E, D>[] = []
+  routes: Route<P, E, S>[] = []
 
   constructor(init: Partial<Pick<Hono, 'router' | 'strict'>> = {}) {
     super()
@@ -114,18 +127,18 @@ export class Hono<
 
     const allMethods = [...METHODS, METHOD_NAME_ALL_LOWERCASE]
     allMethods.map((method) => {
-      this[method] = <Path extends string = ''>(
-        args1: Path | Handler<ParamKeys<Path>, E, D>,
-        ...args: [Handler<ParamKeys<Path>, E, D>]
+      this[method] = <Path extends string, Env extends Environment, Data extends Schema>(
+        args1: Path | Handler<ParamKeys<Path>, Env, Data>,
+        ...args: [Handler<ParamKeys<Path>, Env, Data>]
       ): this => {
         if (typeof args1 === 'string') {
           this.path = args1
         } else {
-          this.addRoute(method, this.path, args1)
+          this.addRoute(method, this.path, args1 as unknown as Handler<P, E, S>)
         }
         args.map((handler) => {
           if (typeof handler !== 'string') {
-            this.addRoute(method, this.path, handler)
+            this.addRoute(method, this.path, handler as unknown as Handler<P, E, S>)
           }
         })
         return this
@@ -135,17 +148,17 @@ export class Hono<
     Object.assign(this, init)
   }
 
-  private notFoundHandler: NotFoundHandler<E> = (c: Context<string, E>) => {
+  private notFoundHandler: NotFoundHandler<P, E, S> = (c: Context<P, E, S>) => {
     return c.text('404 Not Found', 404)
   }
 
-  private errorHandler: ErrorHandler<E> = (err: Error, c: Context<string, E>) => {
+  private errorHandler: ErrorHandler<P, E, S> = (err: Error, c: Context<P, E, S>) => {
     console.trace(err.message)
     const message = 'Internal Server Error'
     return c.text(message, 500)
   }
 
-  route(path: string, app?: Hono<any>): Hono<E, P, D> {
+  route(path: string, app?: Hono<E, P, S>) {
     this._tempPath = path
     if (app) {
       app.routes.map((r) => {
@@ -153,18 +166,17 @@ export class Hono<
       })
       this._tempPath = ''
     }
-
     return this
   }
 
-  use<Path extends string = string, Data extends ValidatedData = D>(
+  use<Path extends string = string, Data extends Partial<Schema> = Schema>(
     ...middleware: Handler<Path, E, Data>[]
-  ): Hono<E, Path, Data>
-  use<Path extends string = string, Data extends ValidatedData = D>(
+  ): Hono<E, Path, S>
+  use<Path extends string = string, Data extends Partial<Schema> = Schema>(
     arg1: string,
     ...middleware: Handler<Path, E, Data>[]
-  ): Hono<E, Path, D>
-  use(arg1: string | Handler<string, E, D>, ...handlers: Handler<string, E, D>[]): Hono<E, P, D> {
+  ): Hono<E, Path, S>
+  use(arg1: string | Handler<P, E, S>, ...handlers: Handler<P, E, S>[]) {
     if (typeof arg1 === 'string') {
       this.path = arg1
     } else {
@@ -176,23 +188,23 @@ export class Hono<
     return this
   }
 
-  onError(handler: ErrorHandler<E>): Hono<E, P, D> {
+  onError(handler: ErrorHandler<P, E, S>) {
     this.errorHandler = handler
     return this
   }
 
-  notFound(handler: NotFoundHandler<E>): Hono<E, P, D> {
+  notFound(handler: NotFoundHandler<P, E, S>) {
     this.notFoundHandler = handler
     return this
   }
 
-  private addRoute(method: string, path: string, handler: Handler<string, E, D>): void {
+  private addRoute(method: string, path: string, handler: Handler<P, E, S>): void {
     method = method.toUpperCase()
     if (this._tempPath) {
       path = mergePath(this._tempPath, path)
     }
     this.router.add(method, path, handler)
-    const r: Route<E, D> = { path: path, method: method, handler: handler }
+    const r: Route<P, E, S> = { path: path, method: method, handler: handler }
     this.routes.push(r)
   }
 
@@ -200,7 +212,7 @@ export class Hono<
     return this.router.match(method, path)
   }
 
-  private handleError(err: unknown, c: Context) {
+  private handleError(err: unknown, c: Context<P, E, S>) {
     if (err instanceof Error) {
       return this.errorHandler(err, c)
     }
@@ -218,12 +230,12 @@ export class Hono<
     const result = this.matchRoute(method, path)
     request.paramData = result?.params
 
-    const c = new HonoContext<string, E, D>(request, env, eventOrExecutionCtx, this.notFoundHandler)
+    const c = new HonoContext<P, E, S>(request, env, eventOrExecutionCtx, this.notFoundHandler)
 
     // Do not `compose` if it has only one handler
     if (result && result.handlers.length === 1) {
       const handler = result.handlers[0]
-      let res: ReturnType<Handler>
+      let res: ReturnType<Handler<P>>
 
       try {
         res = handler(c, async () => {})
@@ -249,7 +261,7 @@ export class Hono<
     }
 
     const handlers = result ? result.handlers : [this.notFoundHandler]
-    const composed = compose<HonoContext<string, E>, E>(
+    const composed = compose<HonoContext<P, E, S>, P, E, S>(
       handlers,
       this.notFoundHandler,
       this.errorHandler
diff --git a/src/middleware/serve-static/serve-static.ts b/src/middleware/serve-static/serve-static.ts
index 8ef59053..421da36e 100644
--- a/src/middleware/serve-static/serve-static.ts
+++ b/src/middleware/serve-static/serve-static.ts
@@ -1,5 +1,4 @@
-import type { Context } from '../../context'
-import type { Next } from '../../hono'
+import type { MiddlewareHandler } from '../../hono'
 import { getContentFromKVAsset } from '../../utils/cloudflare'
 import { getFilePath } from '../../utils/filepath'
 import { getMimeType } from '../../utils/mime'
@@ -14,8 +13,8 @@ export type ServeStaticOptions = {
 const DEFAULT_DOCUMENT = 'index.html'
 
 // This middleware is available only on Cloudflare Workers.
-export const serveStatic = (options: ServeStaticOptions = { root: '' }) => {
-  return async (c: Context, next: Next) => {
+export const serveStatic = (options: ServeStaticOptions = { root: '' }): MiddlewareHandler => {
+  return async (c, next) => {
     // Do nothing if Response is already set
     if (c.finalized) {
       await next()
diff --git a/src/middleware/validator/middleware.test.ts b/src/middleware/validator/middleware.test.ts
index e089e453..92bc09c8 100644
--- a/src/middleware/validator/middleware.test.ts
+++ b/src/middleware/validator/middleware.test.ts
@@ -1,5 +1,8 @@
+/* eslint-disable @typescript-eslint/no-unused-vars */
 import { Hono } from '../../hono'
 import { getStatusText } from '../../utils/http-status'
+import type { Expect, Equal } from '../../utils/types'
+import type { Schema } from '../../validator/schema'
 import { validator } from './index'
 
 describe('Basic - query', () => {
@@ -102,15 +105,19 @@ describe('Basic - header & custom message', () => {
   })
 })
 
-describe('Basic - JSON', () => {
+describe('Basic - JSON with type check', () => {
   const app = new Hono()
   // JSON
   app.post(
     '/json',
     validator((v) => ({
+      id: v.json('post.author.id').asNumber(),
       name: v.json('post.author.name').isAlpha(),
     })),
     (c) => {
+      const { id, name } = c.req.valid()
+      type verifyID = Expect<Equal<typeof id, number>>
+      type verifyName = Expect<Equal<typeof name, string>>
       return c.text('Valid')
     }
   )
@@ -119,6 +126,7 @@ describe('Basic - JSON', () => {
     const json = {
       post: {
         author: {
+          id: 123,
           name: 'abcdef',
         },
       },
@@ -579,7 +587,7 @@ describe('Structured data', () => {
   })
 })
 
-describe('Array values', () => {
+describe('Array values with type check', () => {
   const app = new Hono()
   app.post(
     '/post',
@@ -591,8 +599,13 @@ describe('Array values', () => {
       },
     })),
     (c) => {
-      const res = c.req.valid()
-      return c.json({ tag1: res.post.tags[0] })
+      const { post } = c.req.valid()
+
+      type verifyTitle = Expect<Equal<typeof post.title, string>>
+      type verifyTags = Expect<Equal<typeof post.tags, string[]>>
+      type verifyIDs = Expect<Equal<typeof post.ids, number[]>>
+
+      return c.json({ tag1: post.tags[0] })
     }
   )
 
@@ -730,3 +743,98 @@ describe('Special case', () => {
     )
   })
 })
+
+describe('Type check in special case', () => {
+  it('Should return 200 response with correct types', async () => {
+    const app = new Hono()
+    app.post(
+      '/posts/:id',
+      validator((v) => ({
+        title: v.body('title').isRequired(),
+      })),
+      (c) => {
+        const res = c.req.valid()
+        const id = c.req.param('id')
+        type verifyTitle = Expect<Equal<typeof res.title, string>>
+        type verifyId = Expect<Equal<typeof id, string>>
+        return c.text(`${id} is ${res.title}`)
+      }
+    )
+    const body = new FormData()
+    body.append('title', 'Hello')
+    const req = new Request('http://localhost/posts/123', {
+      method: 'POST',
+      body: body,
+    })
+    const res = await app.request(req)
+    expect(res.status).toBe(200)
+    expect(await res.text()).toBe('123 is Hello')
+  })
+
+  it('Should return 200 response with correct types - validator and named parameter', async () => {
+    const app = new Hono()
+
+    const vm = validator((v) => ({
+      title: v.body('title').isRequired(),
+    }))
+
+    app.post('/posts', vm, (c) => {
+      const { title } = c.req.valid()
+      type verify = Expect<Equal<typeof title, string>>
+      return c.text(title)
+    })
+
+    app.post('/posts/:id', vm, (c) => {
+      const id = c.req.param('id')
+      const { title } = c.req.valid()
+      type verify = Expect<Equal<typeof title, string>>
+      return c.text(`${id} is ${title}`)
+    })
+
+    const body = new FormData()
+    body.append('title', 'Hello')
+
+    let res = await app.request('http://localhost/posts', {
+      method: 'POST',
+      body: body,
+    })
+    expect(res.status).toBe(200)
+    expect(await res.text()).toBe('Hello')
+    res = await app.request('http://localhost/posts/123?title=foo', {
+      method: 'POST',
+      body: body,
+    })
+    expect(res.status).toBe(200)
+    expect(await res.text()).toBe('123 is Hello')
+  })
+
+  it('Should return 200 response with correct types - Context in validator function', async () => {
+    type Env = { Bindings: { FOO: 'abc' } }
+
+    const app = new Hono<Env>()
+
+    app.get(
+      '/search',
+      validator(
+        (v) => ({
+          foo: v.query('foo'),
+        }),
+        {
+          done: (_, c) => {
+            type verifyBindings = Expect<Equal<typeof c.env.FOO, 'abc'>>
+          },
+        }
+      ),
+      (c) => {
+        const { foo } = c.req.valid()
+        type verifyBindings = Expect<Equal<typeof c.env.FOO, 'abc'>>
+        type verify = Expect<Equal<typeof foo, string>>
+        return c.text(foo)
+      }
+    )
+
+    const res = await app.request('http://localhost/search?foo=bar')
+    expect(res.status).toBe(200)
+    expect(await res.text()).toBe('bar')
+  })
+})
diff --git a/src/middleware/validator/middleware.ts b/src/middleware/validator/middleware.ts
index 621b2682..3c53044d 100644
--- a/src/middleware/validator/middleware.ts
+++ b/src/middleware/validator/middleware.ts
@@ -1,62 +1,10 @@
 import type { Context } from '../../context'
-import type { Environment, Next, ValidatedData } from '../../hono'
+import type { Environment, MiddlewareHandler } from '../../hono'
 import { getStatusText } from '../../utils/http-status'
 import { mergeObjects } from '../../utils/object'
-import { VBase, Validator, VObjectBase } from './validator'
-import type {
-  VString,
-  VNumber,
-  VBoolean,
-  VObject,
-  VNumberArray,
-  VStringArray,
-  VBooleanArray,
-  ValidateResult,
-  VArray,
-} from './validator'
-
-export type Schema = {
-  [key: string]:
-    | VString
-    | VNumber
-    | VBoolean
-    | VStringArray
-    | VNumberArray
-    | VBooleanArray
-    | Schema
-    | VObject<Schema>
-    | VArray<Schema>
-}
-
-type SchemaToProp<T> = {
-  [K in keyof T]: T[K] extends VNumberArray
-    ? number[]
-    : T[K] extends VBooleanArray
-    ? boolean[]
-    : T[K] extends VStringArray
-    ? string[]
-    : T[K] extends VNumber
-    ? number
-    : T[K] extends VBoolean
-    ? boolean
-    : T[K] extends VString
-    ? string
-    : T[K] extends VObjectBase<Schema>
-    ? T[K]['container'] extends VNumber
-      ? number
-      : T[K]['container'] extends VString
-      ? string
-      : T[K]['container'] extends VBoolean
-      ? boolean
-      : T[K] extends VArray<Schema>
-      ? SchemaToProp<ReadonlyArray<T[K]['container']>>
-      : T[K] extends VObject<Schema>
-      ? SchemaToProp<T[K]['container']>
-      : T[K] extends Schema
-      ? SchemaToProp<T[K]>
-      : never
-    : SchemaToProp<T[K]>
-}
+import type { Schema } from '../../validator/schema'
+import type { ValidateResult } from '../../validator/validator'
+import { Validator, VBase, VObjectBase } from '../../validator/validator'
 
 type ResultSet = {
   hasError: boolean
@@ -64,27 +12,27 @@ type ResultSet = {
   results: ValidateResult[]
 }
 
-type Done<Env extends Partial<Environment>> = (
+type Done<P extends string, E extends Partial<Environment> = Environment> = (
   resultSet: ResultSet,
-  context: Context<string, Env>
+  c: Context<P, E>
 ) => Response | void
 
-type ValidationFunction<T, Env extends Partial<Environment>> = (
-  v: Validator,
-  c: Context<string, Env>
-) => T
+type ValidationFunction<
+  P extends string,
+  E extends Partial<Environment> = Environment,
+  S extends Schema = Schema
+> = (v: Validator, c: Context<P, E>) => S
 
-type MiddlewareHandler<
-  Data extends ValidatedData = ValidatedData,
-  Env extends Partial<Environment> = Environment
-> = (c: Context<string, Env, Data>, next: Next) => Promise<void> | Promise<Response | undefined>
-
-export const validatorMiddleware = <T extends Schema, Env extends Partial<Environment>>(
-  validationFunction: ValidationFunction<T, Env>,
-  options?: { done?: Done<Env> }
+export const validatorMiddleware = <
+  P extends string,
+  E extends Partial<Environment> = Environment,
+  S extends Schema = Schema
+>(
+  validationFunction: ValidationFunction<P, E, S>,
+  options?: { done?: Done<P, E> }
 ) => {
   const v = new Validator()
-  const handler: MiddlewareHandler<SchemaToProp<T>, Env> = async (c, next) => {
+  const handler: MiddlewareHandler<string, E, S> = async (c, next) => {
     const resultSet: ResultSet = {
       hasError: false,
       messages: [],
@@ -98,7 +46,7 @@ export const validatorMiddleware = <T extends Schema, Env extends Partial<Enviro
     for (const [keys, validator] of validatorList) {
       let results: ValidateResult[]
       try {
-        results = await validator.validate(c.req)
+        results = await validator.validate(c.req as Request)
       } catch (e) {
         // Invalid JSON request
         return c.text(getStatusText(400), 400)
diff --git a/src/request.ts b/src/request.ts
index 2a7592da..9b6295c3 100644
--- a/src/request.ts
+++ b/src/request.ts
@@ -36,11 +36,12 @@ declare global {
     }
     bodyData?: BodyData
     parseBody<BodyType extends BodyData>(): Promise<BodyType>
+    // eslint-disable-next-line @typescript-eslint/no-explicit-any
     jsonData?: any
-    json<JSONData = any>(): Promise<JSONData>
+    json<JSONData = unknown>(): Promise<Partial<JSONData>>
     data: Data
     valid: {
-      (key: string | string[], value: any): Data
+      (key: string | string[], value: unknown): Data
       (): Data
     }
   }
@@ -132,9 +133,9 @@ export function extendRequestPrototype() {
     return body
   } as InstanceType<typeof Request>['parseBody']
 
-  Request.prototype.json = async function <JSONData>(this: Request): Promise<JSONData> {
+  Request.prototype.json = async function <JSONData = unknown>(this: Request) {
     // Cache the JSON body
-    let jsonData: JSONData
+    let jsonData: Partial<JSONData>
     if (!this.jsonData) {
       jsonData = JSON.parse(await this.text())
       this.jsonData = jsonData
@@ -144,7 +145,7 @@ export function extendRequestPrototype() {
     return jsonData
   } as InstanceType<typeof Request>['jsonData']
 
-  Request.prototype.valid = function (this: Request, keys?: string | string[], value?: any) {
+  Request.prototype.valid = function (this: Request, keys?: string | string[], value?: unknown) {
     if (!this.data) {
       this.data = {}
     }
diff --git a/src/utils/types.ts b/src/utils/types.ts
new file mode 100644
index 00000000..a61550ba
--- /dev/null
+++ b/src/utils/types.ts
@@ -0,0 +1,5 @@
+export type Expect<T extends true> = T
+export type Equal<X, Y> = (<T>() => T extends X ? 1 : 2) extends <T>() => T extends Y ? 1 : 2
+  ? true
+  : false
+export type NotEqual<X, Y> = true extends Equal<X, Y> ? false : true
diff --git a/src/middleware/validator/rule.test.ts b/src/validator/rule.test.ts
similarity index 100%
rename from src/middleware/validator/rule.test.ts
rename to src/validator/rule.test.ts
diff --git a/src/middleware/validator/rule.ts b/src/validator/rule.ts
similarity index 100%
rename from src/middleware/validator/rule.ts
rename to src/validator/rule.ts
diff --git a/src/middleware/validator/sanitizer.test.ts b/src/validator/sanitizer.test.ts
similarity index 100%
rename from src/middleware/validator/sanitizer.test.ts
rename to src/validator/sanitizer.test.ts
diff --git a/src/middleware/validator/sanitizer.ts b/src/validator/sanitizer.ts
similarity index 100%
rename from src/middleware/validator/sanitizer.ts
rename to src/validator/sanitizer.ts
diff --git a/src/validator/schema.ts b/src/validator/schema.ts
new file mode 100644
index 00000000..dbf66f05
--- /dev/null
+++ b/src/validator/schema.ts
@@ -0,0 +1,54 @@
+import type {
+  VString,
+  VNumber,
+  VBoolean,
+  VObject,
+  VNumberArray,
+  VStringArray,
+  VBooleanArray,
+  VArray,
+  VObjectBase,
+} from './validator'
+
+export type Schema = {
+  [key: string]:
+    | VString
+    | VNumber
+    | VBoolean
+    | VStringArray
+    | VNumberArray
+    | VBooleanArray
+    | Schema
+    | VObject<Schema>
+    | VArray<Schema>
+}
+
+export type SchemaToProp<T> = {
+  [K in keyof T]: T[K] extends VNumberArray
+    ? number[]
+    : T[K] extends VBooleanArray
+    ? boolean[]
+    : T[K] extends VStringArray
+    ? string[]
+    : T[K] extends VNumber
+    ? number
+    : T[K] extends VBoolean
+    ? boolean
+    : T[K] extends VString
+    ? string
+    : T[K] extends VObjectBase<Schema>
+    ? T[K]['container'] extends VNumber
+      ? number
+      : T[K]['container'] extends VString
+      ? string
+      : T[K]['container'] extends VBoolean
+      ? boolean
+      : T[K] extends VArray<Schema>
+      ? SchemaToProp<ReadonlyArray<T[K]['container']>>
+      : T[K] extends VObject<Schema>
+      ? SchemaToProp<T[K]['container']>
+      : T[K] extends Schema
+      ? SchemaToProp<T[K]>
+      : never
+    : SchemaToProp<T[K]>
+}
diff --git a/src/middleware/validator/validator.test.ts b/src/validator/validator.test.ts
similarity index 99%
rename from src/middleware/validator/validator.test.ts
rename to src/validator/validator.test.ts
index 273e2c5f..552f0ace 100644
--- a/src/middleware/validator/validator.test.ts
+++ b/src/validator/validator.test.ts
@@ -1,4 +1,4 @@
-import { extendRequestPrototype } from '../../request'
+import { extendRequestPrototype } from '../request'
 import { Validator } from './validator'
 
 extendRequestPrototype()
diff --git a/src/middleware/validator/validator.ts b/src/validator/validator.ts
similarity index 98%
rename from src/middleware/validator/validator.ts
rename to src/validator/validator.ts
index 22d26965..3ab31fc1 100644
--- a/src/middleware/validator/validator.ts
+++ b/src/validator/validator.ts
@@ -1,8 +1,8 @@
-import { JSONPathCopy } from '../../utils/json'
-import type { JSONObject, JSONPrimitive, JSONArray } from '../../utils/json'
-import type { Schema } from './middleware'
+import { JSONPathCopy } from './../utils/json'
+import type { JSONObject, JSONPrimitive, JSONArray } from './../utils/json'
 import { rule } from './rule'
 import { sanitizer } from './sanitizer'
+import type { Schema } from './schema'
 
 type Target = 'query' | 'header' | 'body' | 'json'
 type Type = JSONPrimitive | JSONObject | JSONArray | File
@@ -209,7 +209,7 @@ export abstract class VBase {
     return this
   }
 
-  validate = async (req: Request): Promise<ValidateResult[]> => {
+  validate = async <R extends Request>(req: R): Promise<ValidateResult[]> => {
     let value: Type = undefined
     let jsonData: JSONObject | undefined = undefined
 
diff --git a/tsconfig.build.cjs.json b/tsconfig.build.cjs.json
index 0596a506..12bcc9f2 100644
--- a/tsconfig.build.cjs.json
+++ b/tsconfig.build.cjs.json
@@ -5,6 +5,8 @@
     "declaration": false,
     "rootDir": "./src/",
     "outDir": "./dist/cjs/",
+    "noUnusedLocals": true,
+    "noUnusedParameters": true,
   },
   "include": [
     "src/**/*.ts"
diff --git a/tsconfig.build.json b/tsconfig.build.json
index 40ac3f4c..42eeebfa 100644
--- a/tsconfig.build.json
+++ b/tsconfig.build.json
@@ -4,6 +4,8 @@
     "module": "ES2020",
     "rootDir": "./src/",
     "outDir": "./dist/",
+    "noUnusedLocals": true,
+    "noUnusedParameters": true,
   },
   "include": [
     "src/**/*.ts",
diff --git a/tsconfig.json b/tsconfig.json
index 9be69405..6940f1b9 100644
--- a/tsconfig.json
+++ b/tsconfig.json
@@ -10,8 +10,8 @@
     "skipLibCheck": true,
     "strictPropertyInitialization": true,
     "strictNullChecks": true,
-    "noUnusedLocals": true,
-    "noUnusedParameters": true,
+    "noUnusedLocals": false,
+    "noUnusedParameters": false,
     "types": [
       "jest",
       "node",