Accessing computed property sometimes causes unexpected consume of borrowed value #73292
Description
Description
I've found two cases of values getting consumed when reading computed properties, and they seem like they're not correct behavior based on my reading of SE-0377 and SE-0390.
- case 1 is a method with a
borrowed some Protoparameter calling a getter on the borrowed value - case 2 is a
borrowingmethod in astruct A<T>that has a stored propertyv: T
Reproduction
Case 1: borrowed parameter with opaque type
struct Example {
protocol Proto {
// doesn't work with { borrowing get } either
var count: Int { get }
}
func takeProto(_ p: borrowing some Proto) -> Int {
p.count
}
}Result is
error: 'p' is borrowed and cannot be consumed
func takeProto(_ p: borrowing some Proto) -> Int {
^
note: consumed here
p.count
^
Interestingly using p: borrowing any Proto leads to a different error. Should I make another issue for this as the error suggests?
error: usage of no-implicit-copy value that the compiler can't verify.
This is a compiler bug. Please file a bug with a small example of the bug
Case 2: borrowing method in a generic struct with stored property of generic type
struct Broken<Base> {
let base: Base
var compd: Int { 666 }
borrowing func doSomething() -> Int { compd }
}error: 'self' is borrowed and cannot be consumed
borrowing func doSomething() -> Int { compd }
^
note: consumed here
borrowing func doSomething() -> Int { compd }
^
Expected behavior
Case 1
Expected no error
Case 2
Expected no error, like in the following cases that compile fine:
class Class<Base> {
let base: Base
var computed: Int { 666 }
borrowing func doSomething() -> Int { computed }
init(base: Base) {
self.base = base
}
}
struct NoProp<Base> {
var computed: Int { 666 }
borrowing func doSomething() -> Int { computed }
}
struct NotGeneric {
var computed: Int { 666 }
borrowing func doSomething() -> Int { computed }
}Environment
swift-driver version: 1.90.11.1 Apple Swift version 5.10 (swiftlang-5.10.0.13 clang-1500.3.9.4)
Target: arm64-apple-macosx14.0