`func type(of:)` is wholly magical, but it does have a signature in the stdlib (mostly for documentation purposes), and it currently requires its input to be copyable and escapable.
`type(of:)` is actually usable on all entities, so it seems desirable to update its signature to reflect this.
Additionally, this seems like a good time to mark its exported symbol obsolete. I don’t expect anyone would ever link to it (unless there is/was a bug), so in theory we could also silently remove it — but explicitly marking it as legacy ABI seems the least risky option.
We cannot currently express its proper lifetime semantics: its result’s lifetime should depend on the intersection of the lifetime of the left argument and the lifetime of the result of the right argument.
`@lifetime(optional, defaultValue.result)` is what we want, but the `.result` part is not currently expressible. (Tying the dependency on the closure argument itself may be a viable option, but we aren’t confident enough to ship it like that yet.)
Introduce a marker protocol SendableMetatype that is used to indicate
when the metatype of a type will conform to Sendable. Specifically,
`T: SendableMetatype` implies `T.Type: Sendable`. When strict
metatype sendability is enabled, metatypes are only sendable when `T:
SendableMetatype`.
All nominal types implicitly conform to `SendableMetatype`, as do the
various builtin types, function types, etc. The `Sendable` marker
protocol now inherits from `SendableMetatype`, so that `T: Sendable`
implies `T.Type: Sendable`.
Thank you Slava for the excellent idea!
We used to treat 'rethrows' like an attribute, printing it as
'@rethrows', which was incorrect. That's fixed now, so update the
API/ABI checker tests to account for that.
A generic signature's `getInnermostGenericParams` will find the generic
parameters in the innermost scope. That's not quite right for printing
inverses, since we don't want to print an inverse for `T` when emitting
the generic signature of `f` below:
```swift
struct S<T: ~Copyable, E> {
func f() where E == Never {}
}
```
Since `f` has its own generic signature, but doesn't define any generic
parameters, it shouldn't have an inverse emitted. The solution here is
to filter inverses by depth of the generic parameter.
We also want to print _all_ of the inverses in other situations, rather
than just the innermost ones. This aids in debugging and other
tools like the API digester.
resolves rdar://130179698
There are conformers to SIMDStorage (like that in the added test case)
which involve an Array (a type that can't conform to BitwiseCopyable).
So lift the constraint on SIMDStorage. This in turn requires lifting
the constraint on SIMD (otherwise, e.g. `SIMD8<Scalar>` would fail to
conform since it has as a member some SIMD8Storage which is only
constrained to conform to `SIMDStorage`; the `SIMD8Storage`
associatedtype also cannot be constrained to `BitwiseCopyable` because
that storage may again not conform as in the test example).
rdar://128661878
Member operators of concrete nominal types must declare at least
one parameter with that type, like
```
struct S {
static func +(lhs: S, rhs: Int) -> S {}
}
```
For protocol member operators, we would look for a parameter of type
`Self`, or an existential type `any P`. While the latter was
consistent with the concrete nominal type case, it was actually
wrong because then the resulting interface type does not give the
type checker any way to bind the `Self` type parameter.
There were two existing test cases that now produce errors, which I
believe is now correct. While this is technically a source break,
because these bogus operators seemingly cannot be witnessed or called,
such a protocol probably had no conforming types.
Fixes https://github.com/apple/swift/issues/73201.
The presence of Copyable/Escapable conformances doesn't affect ABI. Only
their absence in terms of suppressed requirements like `~Copyable` need
to be output for diffing by the APIDigester.
When the BitwiseCopyable experimental feature is enabled, infer types to
conform to `_BitwiseCopyable`. The `_BitwiseCopyable` inference broadly
follows the approach taken to infer `Sendable`.
(1) Special types are conformed:
- function types if trivial
- metatypes
- builtin types if trivial
(2) TheTupleType is conditionally conformed.
(3) Nominal types are conformed if:
- non-public or public+fixed-layout
- enum or struct (non-class)
- every field conforms to _BitwiseCopyable
Additionally, check that nominal types which are explicitly conformed to
`_BitwiseCopyable` satisfy the latter two conditions of (3).
For a public, non-fixed-layout type to conform to `_BitwiseCopyable`,
the user must conform the type explicitly.
Finally, verify that conformances correspond to TypeLowering's notion of
triviality to the appropriate extent:
- if a type isn't trivial, it doesn't conform to `_BitwiseCopyable`
unless it's an archetype
- if a type is trivial, it conforms to `_BitwiseCopyable` unless some
field in its layout doesn't conform to `_BitwiseCopyable`, which is
only permitted under certain circumstances (the type has generic
parameters, the type is public non-fixed-layout, the type is a
reference but has ReferenceStorage::Unmanaged, the type is a
ModuleType, etc.)
There is a small bug fix here in the identification of the catch node,
where the leading `{` of a closure was considered to be "inside" the
closure for code like
{ ... }()
causing us to assume that the call to the closure would catch the error
within the closure.
Other than that, introduce the thrown error type into the type checker's
modeling of `withoutActuallyEscaping(_:do:)`, and mirror that in the
library declaration.
Make `init(catching:)` and `get()` use typed throws. The former infers
the `Failure` type from the closure provided (once full type inference
is in place) and the latter only throws errors of the `Failure` type.
