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

[Jens Persson]

// 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`"
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