In theory this is a source break if someone had a weird custom
conforming type, but I suspect in practice conformances to
this protocol are never defined.
The reason we want this requirement is that often you will see
code like the following:
protocol Point {
associatedtype Scalar: SIMDScalar
associatedtype Vector: SIMD where Vector.Scalar == Scalar
}
extension Point where Vector == SIMD2<Scalar> { ... }
When `Vector` is equated with `SIMD2<Scalar>`, we get an infinite
sequence of implied same-type requirements:
Vector.MaskStorage == SIMD2<Scalar.MaskScalar>
Vector.MaskStorage.MaskStorage == SIMD2<Scalar.MaskScalar.MaskScalar>
...
The protocol fails to typecheck with an error because the requirement
machine cannot build a rewrite system.
If SIMDScalar requires that MaskScalar.MaskScalar == MaskScalar, then
we instead get
Vector.MaskStorage == SIMD2<Scalar.MaskScalar>
Vector.MaskStorage.MaskStorage == SIMD2<Scalar.MaskScalar>
Vector.MaskStorage.MaskStorage == Vector.MaskStorage
...
Which ties off the recursion.
In theory, a more advanced implementation could represent this kind of
infinite recursion in 'closed form', but we don't have that yet, and I
believe adding this same-type requirement makes sense anyway.
Fixes rdar://problem/95075552.
`Element` is expected to always be `Self`. `RawValue` would be a better choice for the primary type ("option set of UInt32"), but to avoid confusion, it seems better to just omit the declaration, at least for now.
* Implement String.WordView
* Add isWordAligned bit
* Hide WordView for now (also separate Index type)
add bidirectional conformance
Fix tests
* Address comments from Karoy and Michael
* Remove word view, use index methods
* Address Karoy's comments
aaa
If the sequence passed to `Set.intersection` has exactly as many duplicate items as items missing from `self`, then the new implementation in 5.6 will mistakenly return `self` unchanged. (It counts duplicate hits as distinct items in the result.)
rdar://94803458
- the previous docs for assertionFailure implies that it is a nonreturning function, which has always been wrong.
- the example usage previously given for assertionFailure was moved to preconditionFailure, where it is more appropriate.
When we're building static libraries, we don't need to include the
threading objects in both Concurrency and Core, and we also don't need
two copies of the threading library's fatal error handler.
rdar://90776105
Moved all the threading code to one place. Added explicit support for
Darwin, Linux, Pthreads, C11 threads and Win32 threads, including new
implementations of Once for Linux, Pthreads, C11 and Win32.
rdar://90776105
When we're building static libraries, we don't need to include the
threading objects in both Concurrency and Core, and we also don't need
two copies of the threading library's fatal error handler.
rdar://90776105
Moved all the threading code to one place. Added explicit support for
Darwin, Linux, Pthreads, C11 threads and Win32 threads, including new
implementations of Once for Linux, Pthreads, C11 and Win32.
rdar://90776105
