Properties that rely on type inference are not exported into Java

[abdulowork]

Reproduction

I am certain Swift Java developers know about this limitation, but I don't see any issues mentioning type inference explicitly. As of 5764bc2a1b706056121109dc0ab14fd3d771cbc5 for the following code:

public class Foo {
    public let a = 1
    public let b: Int = 1
}

only the b property is exported; the property a that doesn't spell out the type explicitly is skipped and I also don't see any mentions of this in the logs of jextract.

[abdulowork]

Perhaps this limitation could be a relevant input for the follow-up work on foreign build systems importing arbitrary Swift code (e.g. as in #486). IIUC it should be possible to bypass this limitation by first producing the .swiftinterface and importing that, since all the types are going to be spelled out, but that in turn is currently limited by #339 and I also remember that @JavaClass-annotated code is currently exported differently from the .swiftinterface since macros are a compile-time feature.

[ktoso]

Yeah we can't handle this unless we first compile and then use swift interfaces as inputs, as you just mentioned.

A quick action to take here though would be to warn when we encounter such properties.

Not currently planning to work on this specific bit, but it could be something to look at in the long term.