Valid union-of-partials data does not parse even though it conforms to one (or more) of the union members

[brenfwd]

Consider this example:

import { z } from "zod";

const FooASchema = z.object({
  type: z.literal("A"),
  a: z.number(),
});

const FooBSchema = z.object({
  type: z.literal("B"),
  b: z.number(),
});

// const FooSchema = z.union([FooASchema, FooBSchema]);
const PartialFooSchema = z.union([FooASchema.partial(), FooBSchema.partial()]);

const input: unknown = { b: 12 };

const typed = PartialFooSchema.safeParse(input);

console.log("Input:", input);
console.log("Error:", typed.error);
console.log("Data:", typed.data);

Here I would expect that typed.data would be { b: 12 } since input should validate against FooBSchema.partial(). However, the actual behavior is (1) no error; and (2) typed.data is {}.

[brenfwd]