Nitpicking: Shouldn't UnsafeMutablePointer be called UnsafeMutatingPointer?

Evolution Discussion
#1

Instances of UnsafePointer<T> and UnsafeMutablePointer<T> are both mutable (if they are vars), but only the latter is capable of mutating the memory that it points to.

let mp1 = UnsafeMutablePointer<UInt8>.allocate(capacity: 123)
var mp2 = UnsafeMutablePointer<UInt8>.allocate(capacity: 456)

var p = UnsafePointer<UInt8>(mp1)
p = UnsafePointer<UInt8>(mp2) // We can mutate the non-mutable pointer `p`,
mp2 = mp1 // just like we can mutate the mutable pointer `mp2`.

// One thing we cannot mutate is the memory that `p` points to:
// p.pointee = 123 // ERROR: Cannot assign to property: 'pointee' is a get-only property
// So `p` is a non-mutating pointer, not a non-mutable pointer.

// We can mutate the memory that `mp1` points to:
mp1.pointee = 78 // This is ok even though mp1 is a let constant, because
// it is not `mp1` that is mutable, it is the memory that it points to.
// And we cannot mutate `mp1` even though the name of its type is "ā€¦Mutableā€¦":
// mp1 = mp2 // ERROR: Cannot assign to value: 'mp1' is a 'let' constant
// So `mp1` is a mutating pointer, not a mutable pointer.

mp1.deallocate()
p.deallocate()
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#2

You are correct. "Mutable" refers to the memory object not the pointer. If we could go back in time it might be something worth nitpicking.

#3

Can't we rename the types and provide type aliases for old name and deprecate those? Or will it cause to much code churn?

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#4

An API that's been in widespread use across multiple releases shouldn't be changed unless it's causing a real practical problem for developers or future language development. A hypothetical problem of unclear semantics can be solved in the documentation.

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#5

Good catch and +1 from me. Clarity over ā€œthat ship has sailedā€. :slight_smile:

P.S. Personally I think APIs should constantly evolve and improve even if in widespread use. I like how Apple keeps updating Cocoa APIs ā€” deprecating old stuff, improving naming, nesting types, etc.

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