From 9cb6b37fa3484eda479f9fb5f9c16757009c841a Mon Sep 17 00:00:00 2001
From: Yusuke Wada <yusuke@kamawada.com>
Date: Wed, 13 Sep 2023 08:57:52 +0900
Subject: [PATCH] fix(types): fix the type error in
 `MiddlewareHandlerInterface` (#1449)

* fix(types): fix the type error in `MiddlewareHandlerInterface`

* denoify
---
 deno_dist/hono-base.ts |  3 ++-
 deno_dist/types.ts     | 11 +++++------
 src/hono-base.ts       |  3 ++-
 src/hono.test.ts       | 11 +++++++++++
 src/types.ts           | 11 +++++------
 5 files changed, 25 insertions(+), 14 deletions(-)

diff --git a/deno_dist/hono-base.ts b/deno_dist/hono-base.ts
index 61996784f..9e2d858cc 100644
--- a/deno_dist/hono-base.ts
+++ b/deno_dist/hono-base.ts
@@ -109,7 +109,8 @@ class Hono<
     }
 
     // Implementation of app.use(...handlers[]) or app.get(path, ...handlers[])
-    this.use = (arg1: string | MiddlewareHandler, ...handlers: MiddlewareHandler[]) => {
+    // eslint-disable-next-line @typescript-eslint/no-explicit-any
+    this.use = (arg1: string | MiddlewareHandler<any>, ...handlers: MiddlewareHandler<any>[]) => {
       if (typeof arg1 === 'string') {
         this.path = arg1
       } else {
diff --git a/deno_dist/types.ts b/deno_dist/types.ts
index 2f77b3286..73edc8241 100644
--- a/deno_dist/types.ts
+++ b/deno_dist/types.ts
@@ -42,7 +42,7 @@ export type Handler<
   R extends HandlerResponse<any> = any
 > = (c: Context<E, P, I>, next: Next) => R
 
-export type MiddlewareHandler<E extends Env = any, P extends string = any, I extends Input = {}> = (
+export type MiddlewareHandler<E extends Env = {}, P extends string = any, I extends Input = {}> = (
   c: Context<E, P, I>,
   next: Next
 ) => Promise<Response | void>
@@ -296,11 +296,10 @@ export interface MiddlewareHandlerInterface<
   //// app.get(...handlers[])
   (...handlers: MiddlewareHandler<E, MergePath<BasePath, ExtractKey<S>>>[]): Hono<E, S, BasePath>
   //// app.get(path, ...handlers[])
-  <P extends string>(path: P, ...handlers: MiddlewareHandler<E, MergePath<BasePath, P>>[]): Hono<
-    E,
-    S,
-    BasePath
-  >
+  <P extends string, E2 extends Env = E>(
+    path: P,
+    ...handlers: MiddlewareHandler<E2, MergePath<BasePath, P>>[]
+  ): Hono<E, S, BasePath>
 }
 
 ////////////////////////////////////////
diff --git a/src/hono-base.ts b/src/hono-base.ts
index 64dd9d875..e4a31b74e 100644
--- a/src/hono-base.ts
+++ b/src/hono-base.ts
@@ -109,7 +109,8 @@ class Hono<
     }
 
     // Implementation of app.use(...handlers[]) or app.get(path, ...handlers[])
-    this.use = (arg1: string | MiddlewareHandler, ...handlers: MiddlewareHandler[]) => {
+    // eslint-disable-next-line @typescript-eslint/no-explicit-any
+    this.use = (arg1: string | MiddlewareHandler<any>, ...handlers: MiddlewareHandler<any>[]) => {
       if (typeof arg1 === 'string') {
         this.path = arg1
       } else {
diff --git a/src/hono.test.ts b/src/hono.test.ts
index e096527b3..1b9a6cc6d 100644
--- a/src/hono.test.ts
+++ b/src/hono.test.ts
@@ -2660,4 +2660,15 @@ describe('c.var - with testing types', () => {
       })
     }).toThrow()
   })
+
+  it('Should not throw a type error', (c) => {
+    const app = new Hono<{
+      Bindings: {
+        TOKEN: string
+      }
+    }>()
+    app.get('/', poweredBy(), async (c) => {
+      type verify = Expect<Equal<string, typeof c.env.TOKEN>>
+    })
+  })
 })
diff --git a/src/types.ts b/src/types.ts
index 17f1cd7c9..4bcc88dea 100644
--- a/src/types.ts
+++ b/src/types.ts
@@ -42,7 +42,7 @@ export type Handler<
   R extends HandlerResponse<any> = any
 > = (c: Context<E, P, I>, next: Next) => R
 
-export type MiddlewareHandler<E extends Env = any, P extends string = any, I extends Input = {}> = (
+export type MiddlewareHandler<E extends Env = {}, P extends string = any, I extends Input = {}> = (
   c: Context<E, P, I>,
   next: Next
 ) => Promise<Response | void>
@@ -296,11 +296,10 @@ export interface MiddlewareHandlerInterface<
   //// app.get(...handlers[])
   (...handlers: MiddlewareHandler<E, MergePath<BasePath, ExtractKey<S>>>[]): Hono<E, S, BasePath>
   //// app.get(path, ...handlers[])
-  <P extends string>(path: P, ...handlers: MiddlewareHandler<E, MergePath<BasePath, P>>[]): Hono<
-    E,
-    S,
-    BasePath
-  >
+  <P extends string, E2 extends Env = E>(
+    path: P,
+    ...handlers: MiddlewareHandler<E2, MergePath<BasePath, P>>[]
+  ): Hono<E, S, BasePath>
 }
 
 ////////////////////////////////////////