Incorrect Type Inference with unions of schemas

[gcanti]

🐛 Bug report

Reproducible example

import * as S from '@effect/schema/Schema'

declare const s: S.Schema<string> | S.Schema<number>
const x: S.Schema<string | number, string | number> = s // error :)
const y = S.union(s) // no error :(

Current Behavior

Currently, const x generates a type error, correctly indicating the incompatibility between the union type and the expected type. However, const y does not generate any error, allowing the union to be used without any issues.

Expected behavior

The expected behavior is that both const x and const y should generate a type error since s is a union of S.Schema<string> and S.Schema<number>.

Your environment

Software	Version(s)
@effect/schema	0.20.1
TypeScript	5.x