RPC output type becomes never when returning an array of interface

[cormojs]

What version of Hono are you using?

4.4.2

What runtime/platform is your app running on?

Bun

What steps can reproduce the bug?

import { Hono } from "hono";
import { hc } from "hono/client";

// common
interface TestInterface {
  test: string
}
const testValue: TestInterface[] = [{ test: 'test' }]

// server

const testApi = new Hono()
  .get(
    '/test',
    async c => {
      return c.json(testValue)
    }
  )

export type Test = typeof testApi

// client
type WrongType = {
  wrong: string
}

const testFunction = (test: WrongType) => {
  console.log(test)
}

const client = hc<Test>('http://localhost')
const resp = await client.test.$get()
const result = await resp.json()

testFunction(testValue) // this case reports an error
testFunction(result)  // this case does not report any errors(type of result is never)

What is the expected behavior?

Type checking should be failed in both case.

What do you see instead?

The latter case does not report any type error.

Additional information

The problems does not reproduce when using type alias instead of interface.

[EdamAme-x]

minimal project
https://www.typescriptlang.org/play/?#code/JYWwDg9gTgLgBAbzgCQgOwnAvnAZlCEOAIgAt0JiBuAKFElkTlIGNs8CiyKB6FgG2ABTNDGo0aPHnBaEQ6OqKFRcAQxZC4AFSEBnGAEklK9ZoQ04cGHpgAuOPqjA0AcxpYastPqs2Aaqr8AK5C9jr6RtYmGgDaALpwALxwMUjW+vYA5OkwmdhxElIOygBuyhJePjkAgmDASXBoQgDuKBQAFACUFnAAdC5CMO09lpk8OZkANCNwqroAnmhsbIkAfIgzllCDQVBoMr0AVrro7TkBwULdlpYelt00QgAeDPAw82Ca4fDJ758QuF8+lqwEK0gEwlEND+mgA6gRXFoPppkuZLM0ES57I5nG4PJ50FUbAAxIJLGDAdANM42ezw9AuJGfTpJdZomSEiD8IS9fgQFw0-TdfGVeAQkQ-ZgsAA831W7UypBgMDAtikfJYgXI+ky3VFcG2ujADVUzVUwDFgglvRyvQAJAMhnrCfBDUF+JLTebXXowEcTmguhIcqTyZTA+dAiEWUUYKRgLoZHNNNtXonVPtlAQoNCSWSWBTTm6PSy4LH44nNbpNAATCB6RoQH2vWZoeZwLPQXRnZFwAEGvTu+AJxpCMpQTpAA

[EdamAme-x]

[EdamAme-x]

[EdamAme-x]

[EdamAme-x]

hono/src/client/types.ts

Line 52 in 0d851b6

type BlankRecordToNever<T> = T extends any

it works.

https://www.typescriptlang.org/play/?#code/C4TwDgpgBAQgNgQwHYGsBKEDGB7ATgEwBVsA5CANwlwB5CA+KAXikKggA9gIl8BnKZCABQUKAH4WbTtz5QkAVzhwRo8XMXLVUAFxQUEENgBmkjlx78kFKitESrlXLZ0sVuhzaGhIsEAHkAIwArLGAmWERUDBwCYjJHagBvBF0ARgBfOi9waBh-YND4qnD4ZHQsPCJSaxpEzOyfPIBBXFwEEBLI8piqopoAbQAiBEGAGihUgF0soA

[EdamAme-x]

cause

hono/src/context.ts

Lines 139 to 143 in 0d851b6

	Simplify<T> extends JSONValue
	? JSONValue extends Simplify<T>
	? never
	: JSONParsed<T>
	: never,

[EdamAme-x]

Simplify is working
https://www.typescriptlang.org/play/?#code/C4TwDgpgBAyglgWzAGzgMxAHgCoD4oC8UA3lANoDSEI240cAdlANbUD2aU2AugFxeVqtSNygBfKADISYgFChIXCAGdgARkKxEKdFmIBDXmrG55dJaoBMm+ElQZMZNQBpLzgMzdTQA

[EdamAme-x]

JSONValue is working
https://www.typescriptlang.org/play/?#code/C4TwDgpgBAyglgWzAGzgMxAHgCoD4oC8UA3lANoDSEI240cAdlANbUD2aU2AugFxeVqtSNygBfKADISYgFChIXCAGdgARkKxEKdFmIBDXmrG55dJaoBMm+ElQZMZNQBpLzgMzdTZxQCkYAPIAcgAKAE6IcMBwAG7QRKoRDADmUAA+UABGbGzIEPpMGQwArgiZEGHpUCXIyFXFDAAmEGiMEI0+0P7BAIJhYfogmgAU3aERCFGx0BljAZkAVhAAxsBVY30DIACUZNydUHOLK2tEpGSsIPyJjMl8h4HjkdFx64+bg2-B80urVWzHP5yBRdR4ANX0yGK8Qe30Ba1m736n0RwXCz2msgOACUVMVkKctHZdI4XFA3FBPPgIAAPYAQJrKWFBCFQ6AAfigGn4liAA

[EdamAme-x]

https://www.typescriptlang.org/play/?#code/C4TwDgpgBAyglgWzAGzgMxAHgCoD4oC8UA3lANoDSEI240cAdlANbUD2aU2AugFxeVqtSNygBfKADISYgFChIXCAGdgARkKxEKdFmIBDXmrG55dJaoBMm+ElQZMZNQBpLzgMzdTZxQCkYAPIAcgAKAE6IcMBwAG7QRKoRDADmUAA+UABGbGzIEPpMGQwArgiZEGHpUCXIyFXFDAAmEGiMEI0+0P7BAIJhYfogmgAU3aERCFGx0BljAZkAVhAAxsBVY30DIACUZNydUHOLK2tEpGSsIPyJjMl8h4HjkdFx64+bg2-B80urVWzHP5yBRdR4ANX0yGK8Qe30Ba1m736n0RwXCz2msgOACUVMVkKctHZdI4XFA3FBPPgIAAPYAQJrKWFBCFQ6AAfigGn4lhxeIJ1iIY1Z0KgtPpjKJOgcTmc5LlVKgnO55KAAhttps://www.typescriptlang.org/play/?#code/C4TwDgpgBAyglgWzAGzgMxAHgCoD4oC8UA3lANoDSEI240cAdlANbUD2aU2AugFxeVqtSNygBfKADISYgFChIXCAGdgARkKxEKdFmIBDXmrG55dJaoBMm+ElQZMZNQBpLzgMzdTZxQCkYAPIAcgAKAE6IcMBwAG7QRKoRDADmUAA+UABGbGzIEPpMGQwArgiZEGHpUCXIyFXFDAAmEGiMEI0+0P7BAIJhYfogmgAU3aERCFGx0BljAZkAVhAAxsBVY30DIACUZNydUHOLK2tEpGSsIPyJjMl8h4HjkdFx64+bg2-B80urVWzHP5yBRdR4ANX0yGK8Qe30Ba1m736n0RwXCz2msgOACUVMVkKctHZdI4XFA3FBPPgIAAPYAQJrKWFBCFQ6AAfigGn4lhxeIJ1iIY1Z0KgtPpjKJOgcTmc5LlVKgnO55KAA

[EdamAme-x]

hmm...
https://www.typescriptlang.org/play/?#code/C4TwDgpgBAyglgWzAGzgMxAHgCoD4oC8UA3lANoDSEI240cAdlANbUD2aU2AugFxeVqtSNygBfKADISYgFChIXCAGdgARkKxEKdFmIBDXmrG55dJaoBMm+ElQZMZNQBpLzgMzdTZxQCkYAPIAcgAKAE6IcMBwAG7QRKoRDADmUAA+UABGbGzIEPpMGQwArgiZEGHpUCXIyFXFDAAmEGiMEI0+0P7BAIJhYfogmgAU3aERCFGx0BljAZkAVhAAxsBVY30DIACUZNydUHOLK2tEpGSsIPyJjMl8h4HjkdFx64+bg2-B80urVWzHP5yBRdR4ANX0yGK8Qe30Ba1m736n0RwXCz2msgOACUVMVkKctHZdI4XFA3FBPPgIAAPYAQJrKWFBCFQ6AAfigGn4lhxeIJ1iIY1Z0KgtPpjKJOgcTmc5LlVKgnO55KxIOZIX0YWU7Rw+CI2DFdIZjSZpGAbDGw22-EYaAqh3EsigSqgw2thHwvm2RolprdPoIXsePxOzpdrt84Zd-DGmu1ut8phjXF9JqZcYmUzi4c52HD-EN4vTUA+WDtDoAqsnXWXMHGtTrGphqzXC2nJQDfsBcyRyBQoIwWOxODxY49402cJQvE6UwwIHEwmrzLjlPjgO5NA2E83ZW4qSvFGuNwAWGzaexYfceWfFyXCyHQ6MRl2cx9sjv+2zS68uA9eC+r5vtUi4VEBwHjmija6jeh7ARG-ALkuEEuny64EgArNu4JPtA97+ucVA0OYQ6XBw5BkhSnj3LK8qUtwggkSIADc4iushDr8MMGgZFuGSWLs3BAA

[EdamAme-x]

If the type is primitive, it seems to be correctly inferred.
https://www.typescriptlang.org/play/?#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-5zNALODF6C6c44uBQsO1uCZxpCUpQTpAA

[EdamAme-x]

https://www.typescriptlang.org/play/?#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-oSICXzXYSyOPWODaTbPnCwBVIel5Crmy9mNxs42Lfbxep9M0kSt9suSLIXxoxqhHtRw-xiKuTXF4d0CATKAIxQO0HTVZwD37Y8GmCCQWzQNpSltCUpQAFmqHI6hsaCmkka94NHdMXRNLtKB3Ii3SXdMfUw7DYMReCSNIncQH-VgmKY18BXfKDvEaOi8O3djaBYgDOCAA

[EdamAme-x]

Simplify<typeof testObjects> extends JSONValue is falsy

[EdamAme-x]

testObject extends JSONObject ? 1 : 2 is falsy (2)
testObject was generated by interface
if it generated by type, the type inference is correct.

https://www.typescriptlang.org/play/?#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-YxgAAFnKTIqksMC6kgkQmgHJN7QNVtSHXPDHVnJN3SlNCPFqCD62gwj6PXVQCPox9eWfUCqPAwRaLXBizRgy1RXggBWZCPWqTiMJ4nCh2Io0TTbIMijg4AADYxIo9CaLhaDlKE4AAHZFG0s8ZJ1WFTIDRSSiAA

[EdamAme-x]

the cause
https://www.typescriptlang.org/play/?#code/JYOwLgpgTgZghgYwgAkgZzMg3sgUMg5OALmQEZcBfXXMATwAcV0wAmZAXm30JPKpr0mqCBgDMnboWQBtANYQ6pDFFABzALqkQAVwC2AI2gDajFACVROgDZgyklsggAPSCAAmaEeOQB+csikrKbClmg2bA6ikS5unt5gEv72QbhAA

[EdamAme-x]

The type in interface is not a subtype of object.

[EdamAme-x]

This is most likely a specification issue.

https://typescript-jp.gitbook.io/deep-dive/type-system/index-signatures