Unhelpful compiler error for `@Flag var _: Bool?` without a default value

[ktoso]

The following should be supported but isn't:

    @Flag(help: "...")
    var writeEmptyFiles: Bool?

The error is

Referencing initializer 'init(name:help:)' on 'Flag' requires the types 'Bool?' and 'Int' be equivalent

It turns out the inversion parameter is required, so the following works:

    @Flag(inversion: .prefixedEnableDisable, help: "")
    var writeEmptyFiles: Bool?

this seems somewhat accidental? Are we just missing an initializer with defaulted inversion?

ArgumentParser version: 0.1.0 or the main branch, for example.
Swift version: swift-driver version: 1.139 Apple Swift version 6.2 (swiftlang-6.3.0.101.15 clang-2100.0.101.15); arm64-apple-macosx26.0

Checklist

• Reproduces on main
• I've searched for existing GitHub issues

Steps to Reproduce

The snippets above are enough to repro

Expected behavior

We should support just @Flag() on optional boolean fields

Actual behavior

fails to compile

[ktoso]

Seems this is just because we don't provide a default, we should add one -- ill follow up on it

[natecook1000]

This functionality is supported, but the overloads we have lead to a bad compiler response. I'm not sure if there's a way to improve it, but something that could point out instead that an initial value is required when the type is Bool? would be great!