Returned error type from validator is not inferred

[bbozzay]

I'm struggling with type inference when using a validator like zValidator and the RPC approach.

On my server, I have the chained response (like docs recommend) with a simple param validator:

// ...chained
.get('/greet/:person', zValidator("param", z.object({ person: z.literal('john') })), (c) => {
  const person = c.req.param('person');
  return c.json({
    result: `Hello ${person}!`,
  });
})

On my client app when I intentionally pass an invalid param, I get a typechecking error as I would expect:

const re = await api.greet[':person'].$get({
  // ts error: 'bill' is not assignable to type 'john'
  param: { person: 'bill' },
});

The inferred type is the result from a successful response, but the actual response is an error which is not inferred at all even if I try narrowing:

// re.ok === false
const data = await re.json();
if (!re.ok) {
  // Does not infer data.name === 'ZodError', only data.result (which doesn't exist)
...
}

return {
// data.result doesn't exist if there was a Zod validation error, but typescript thinks it does!
  greeting: data.result,
};

I'm just completely stuck on this and could use some insight.