[swift-users] Can anyone please explain this behavior?

[Jens Persson]

Did you see the other code examples that came up in that twitter
conversations?
For example:

This worrying little program compiles:
func f() -> Int {
    return a
}
let a = f()


It also compiles if you print(a) at the end, and it will print 0.

If we replace Int with [Int] it will still compile but crash when run.

And also this:

AnotherFile.swift containing:
func f() -> Int {
    return a
}
let a = f()

main.swift containing
print(a)

Compile, run (for eternity, at 0% CPU).

/Jens


On Thu, Sep 22, 2016 at 3:13 AM, Joe Groff <jgroff at apple.com> wrote:

>
> > On Sep 21, 2016, at 2:22 PM, Jens Persson via swift-users <
> swift-users at swift.org> wrote:
> >
> > // This little Swift program compiles (and runs) fine:
> >
> > func foo() -> Int { return a }
> > let a = 1
> > let b = 2
> > print(foo())
> >
> > But if `foo()` returns `b` instead of `a`, I get this compile time error:
> > "Use of unresolved identifier `b`"
>
> This looks like a bug to me (cc-ing Jordan, who's thought about global
> scoping issues more than me). In "script mode", it shouldn't be possible to
> refer to a variable before its initialization is executed. However, the way
> this is currently modeled is…problematic, to say the least, among other
> reasons because script globals are still visible to "library" files in the
> same module.
>
> -Joe
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