id-as-Any lets you pass Optional to an ObjC API that takes `nonnull id`, and also lets you bridge containers of `Optional` to `NSArray` etc. When this occurs, we can unwrap the value and bridge it so that inhabited optionals still pass into ObjC in the expected way, but we need something to represent `none` other than the `nil` pointer. Cocoa provides `NSNull` as the canonical "null for containers" object, which is the least bad of many possible answers. If we happen to have the rare nested optional `T??`, there is no precedented analog for these in Cocoa, so just generate a unique sentinel object to preserve the `nil`-ness depth so we at least don't lose information round-tripping across the ObjC-Swift bridge.
Making Optional conform to _ObjectiveCBridgeable is more or less enough to make this all work, though there are a few additional edge case things that need to be fixed up. We don't want to accept `AnyObject??` as an @objc-compatible type, so special-case Optional in `getForeignRepresentable`.
Implements SR-0140 (rdar://problem/27905315).
This reduces the amount of SIL generated for Set/Dictionary operations significantly.
The generated code should be mostly the same (modulo different inlining decisions).
This reduces the amount of SIL generated for array operations significantly.
The generated code should be mostly the same (modulo different inlining decisions).
Those builtins are: allocWithTailElems_<n>, getTailAddr and projectTailElems
Also rename the "gep" builtin, which indexes raw bytes, to "gepRaw" and add a new "gep" builtin to index in a typed array.
This affects the computed stride for fixed-sized types in IRGen as well as the stored stride in value witness tables.
The reason is to let comparisons and difference operations work for pointers to zero-sized types.
(Currently this is achieved by using Builtin.strideof_nonzero in MemoryLayout.stride, but this requires a std::max(1, stride) operation after loading the stride)
Things like: PthreadBarriers.swift:114:50: error: cannot convert value of type 'UnsafeMutablePointer<pthread_mutex_t>' (aka 'UnsafeMutablePointer<OpaquePointer>') to expected argument type 'UnsafeMutablePointer<pthread_mutex_t?>' (aka 'UnsafeMutablePointer<Optional<OpaquePointer>>')
on barrier.pointee.mutex . I need to do more research to understand this
The new names are what people generally expect. The old names made more
sense in the old times when the 'Optional.None' case could not be
created with the 'nil' keyword.
SE-0032 did not propose a protocol entry point, only a protocol
extension.
Using a pure protocol extension is the right choice here because a
concrete sequence can't provide a more efficient implementation of this
method than the default one.
