Calling global function before declaration

Jens · April 5, 2020, 11:07am

I think this is a bug, here's a reduced example:

// This program compiles and print 0 when run:
print(x) 
let x = 123

// This program compiles and crashes (segmentation fault 11) when run:
print(x) 
let x = [1, 2, 3]

Are you sure that this hasn't always been the case? See for example this old perhaps somewhat related thread:

Can anyone please explain this behavior?

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).

If it the behavior has changed in Swift 5.2, then it seems like more/different bugs have been introduced, since the example in the end of the following old post now compiles (though @jrose says at the end of the post that it is important to make sure it continues to be rejected):