It it possible to specify a returned non-copyable value as borrowed?

Using Swift
2

i don't have much 'real world' experience with noncopyable types, so i may be off here, but i think if you can tolerate the use of underscored (yet longstanding) stdlib APIs, or experimental features, then this can perhaps be achieved by use of the _read/read coroutine accessor.

e.g. if i modify your code as so:

struct B: ~Copyable {
    
    let stored = A()
    
    var computed: A { 
        _read { yield A() }
    }
    
}

then i get the error:

13 | func hello(b: borrowing B) {
14 |     let y = b.stored // disallowed: 'b' is borrowed and cannot be consumed
15 |     let z = b.computed // allowed
   |               |- error: 'b.computed' is borrowed and cannot be consumed
   |               `- note: consumed here
16 | }
17 |
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