Why does UnsafeRawPointer show a different result when function signatures differ in Swift?

Question

The code below can be run on Swift Playground:

import UIKit

func aaa(_ key: UnsafeRawPointer!, _ value: Any! = nil) {
    print(key)
}
func bbb(_ key: UnsafeRawPointer!) {
    print(key)
}
class A {
    var key = "aaa"
}
let a = A()
aaa(&a.key)
bbb(&a.key)

Here is the result printed on my mac:

0x00007fff5dce9248
0x00007fff5dce9220

Why are the results of the two prints different? More interestingly, when I change the signature of the bbb function to make it the same as aaa , the result of the two fingerprints is the same. And if I use the global var instead of a.key in these two function calls, the result of the two fingerprints is the same. Does anyone know why this strange behavior happens?

Answer 1

Why are the results of the two prints different?

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class A {
    final var key = "aaa"
}

var a = A()
aaa(&a.key) // 0x0000000100a0abe0
bbb(&a.key) // 0x0000000100a0abe0

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---

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---

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:

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func aaa(_ key: UnsafeMutableRawPointer) {
    print(key)
}

func bbb(_ key: UnsafeMutableRawPointer) {
    print(key)
}

class A {
    var key = "aaa"
}

var a = A()

// will use materializeForSet to get a direct pointer to a.key
aaa(&a.key) // 0x0000000100b00580
bbb(&a.key) // 0x0000000100b00580

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