Unexpected assertion fail for union type with optional fields

[nathan-ahn]

📝 Summary

Type equality (assert, is, etc.) with certain union objects with optional fields is parsed as non-equal.

• Typia Version: 5.3.0-dev.20231127-2
• Expected behavior: Typia should select the correct object for matching
• Actual behavior: Typia decides the object does not match the intersection type.

interface A {
	name?: "A";
	someBool: true;
}
interface B {
	name?: "B";
	someBool: boolean | undefined;
}

It seems that Typia only validates that the body matches A and doesn't check whether it matches B. This problem resolves itself if someBool is required as non-undefined, or if name is required.

I believe that A | B (see below) should match given that TypeScript doesn't have any issues with the following:

const body = {
	name: "B",
	someBool: true,
} satisfies A | B;

⏯ Playground Link

💻 Code occuring the bug

import typia from "typia";

interface A {
	name?: "A";
	someBool: true;
}
interface A_NonOptional {
	name: "A";
	someBool: true;
}
interface B {
	name?: "B";
	someBool: boolean | undefined;
}
interface C {
	name?: "C";
	someBool: boolean;
}

// Throws (Incorrect; should match B)
const A_and_B = typia.assert<A | B>({
	name: "B",
	someBool: true,
});

// Doesn't throw (Correct)
const A_NonOptional_and_B = typia.assert<A_NonOptional | B>({
	name: "B",
	someBool: true,
});

// Doesn't throw (Correct)
const A_and_C = typia.assert<A | C>({
	name: "C",
	someBool: true,
});

[samchon]

Succeeded to fix this bug.

Will try to fix #885 bug, but if needs lots of time, then will publish immediately.

Thanks for reporting.