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.
Functions that are used in public `@inlinable` function bodies can't be marked
`@_spi` nor can they be made obsolete. Also, they must retain `rethrows` so
that use of these entry points from other `rethrows` functions is accepted.
Builds on https://github.com/apple/swift/pull/72365. Once we no longer have to
support pre-`$TypedThrows` compilers, all of this can be reverted.
Part of rdar://125138945
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.
At the type that I introduced type throws into AsyncSequence and its
algorithms, I accidentally dropped a `@preconcurrency` on the ABI
entrypoint, leading to a mangled name change.
Fixes rdar://123639030.
This couples together several changes to move entirely from
`@rethrows` over to typed throws:
* Use the `Failure` type to determine whether an async for-each loop
will throw, rather than depending on rethrows checking
* Introduce a special carve-out for `rethrows` functions that have a
generic requirement on an `AsyncSequence` or `AsyncIteratorProtocol`,
which uses that requirement's `Failure` type as potentially being part
of the thrown error type. This allows existing generic functions like
the following to continue to work:
func f<S: AsyncSequence>(_: S) rethrows
* Switch SIL generation for the async for-each loop from the prior
`next()` over to the typed-throws version `_nextElement`.
* Remove `@rethrows` from `AsyncSequence` and `AsyncIteratorProtocol`
entirely. We are now fully dependent on typed throws.
Introduce a new associated type `Failure` into the two protocols involved
in async sequences, which represents the type thrown when the sequence
fails. Introduce a defaulted `_nextElement()` operations that throws
`Failure` or produces the next element of the sequence. Provide a
default implementation of `_nextElement()` in terms of `next()` that
force-cases the thrown error to the `Failure` type.
Introduce special associated type inference logic for the `Failure`
type of an `AsyncIteratorProtocol` conformance when there is no
specific _nextElement()` witness. This inference logic looks at the
witness for `next()`:
* If `next()` throws nothing, `Failure` is inferred to `Never`.
* If `next()` throws, `Failure` is inferred to `any Error`.
* If `next()` rethrows, `Failure` is inferred to `T.Failure`, where
`T` is the first type parameter with a conformance to either
`AsyncSequence` or `AsyncIteratorProtocol`.
The default implementation and the inference rule, together, allow
existing async sequences to continue working as before, and set us up
for changing the contract of the `async for` loop to use
`_nextIterator()` rather than `next()`.
Give `AsyncSequence` and `AsyncIteratorProtocol` primary associated
types for the element and failure types, which will allow them to be
used more generally with existential and opaque types.
