[stdlib] fix UnsafePointer.withMemoryRebound(to:capacity:) argument type. (#4908)
SE-0107 states that UnsafePointer.withMemoryRebound(to:capacity:) should produce
a const UnsafePointer, but the implementation that I committed in Whitney
produces an UnsafeMutablePointer.
As a result Swift 3 accepts code, that we would like to reject:
func takesUInt(_: UnsafeMutablePointer<UInt>) {}
func takesConstUInt(_: UnsafePointer<UInt>) {}
func foo(p: UnsafePointer<Int>) {
p.withMemoryRebound(to: UInt.self, capacity: 1) {
takesUInt($0) // <========= implicitly converts to a mutable pointer
takesConstUInt($0)
}
}
We would like to reject this in favor of:
func takesUInt(_: UnsafeMutablePointer<UInt>) {}
func takesConstUInt(_: UnsafePointer<UInt>) {}
func foo(p: UnsafePointer<Int>) {
p.withMemoryRebound(to: UInt.self, capacity: 1) {
takesUInt(UnsafeMutablePointer(mutating: $0))
takesConstUInt($0)
}
}
This looks to me like an experimental change accidentally creeped onto my branch
and it was hard to spot in .gyb code. I needed to write the unit test
in terms of UnsafeMutablePointer in order to use expectType, so didn't
catch this.
rdar://28409842 UnsafePointer.withMemoryRebound(to:capacity:) incorrectly produces a mutable pointer argument
swift
fe1fd2e4 - [stdlib] fix UnsafePointer.withMemoryRebound(to:capacity:) argument type. (#4908)
