Move the diagnostic about non-final generic methods in classes up to
the type checker, so that it is available to `-Wwarning
EmbeddedRestrictions` and earlier in the pipeline. The SIL version of
this is still available as a backstop.
Yet another part of rdar://133874555.
Where we have rethrowing versions of functions that have typed-throws
counterparts that are only retained for ABI compatibility, wrap them
in `#if !$Embedded` so they aren't compiled into the Embedded version
of the standard library. This eliminates warnings about this code,
which cannot actually be used with arbitrary errors anyway.
The stdlib is always built with NoncopyableGenerics enabled, so `#if
$NoncopyableGenerics` guards in non-inlinable code are superfluous.
Additionally, the stdlib's interface no longer needs to support compilers
without the feature, so the guards in inlinable code can also be removed.
https://github.com/swiftlang/swift/pull/72612 can be reverted because it is no
longer necessary for the interface of the stdlib to be compatible with
compilers without `$TypedThrows` support.
The standard library's swiftinterface must temporarily remain buildable when
`$TypedThrows` evaluates to false since there are still supported Swift 5.11
compilers that did not have the feature enabled by default. Declarations using
typed throws in their signatures are guarded in printed swiftinterface files
with `#if $TypedThrows` and therefore `@inlinable` code that uses those
declarations must also be conditionalized on `$TypedThrows`.
These class methods are internal, but because they are overridden and are
part of a `@usableFromInline`, `@_fixed_layout` class, we they can't be
moved over to typed throws without breaking ABI. However, they are
only ever called from typed-throws functions, which already need a
do...catch dance to downcast the error itself. Make them `throws`
instead, which is ABI-compatible, but eliminates the need for
do...catch hackery in the function itself.
Replace the hackish use of `@_disfavoredOverload` with the more principled
use of `@_silgen_name` for the entrypoint we are maintaining, then rename
these functions in source to `__rethrows_map` to indicate what they're for.
While here, make them `throws` instead of `rethrows`. The ABI is the
same, and `throws` allows us do avoid to do/catch tricks with rethrows
functions.
Adopt typed throws for the `map` operation to propagate thrown error
types through the `map` API. This is done in a manner that is backward
compatible for almost all cases:
* The new typed-throws entrypoint is `@_alwaysEmitIntoClient` so it
can back-deploy all the way back.
* The old `rethrows` entrypoint is left in place, using
`@usableFromInline` with `internal` so it is part of the ABI but not
the public interface, and `@_disfavoredOverload` so the type checker
avoids it while building the standard library itself. The old
entrypoint is implemented in terms of the new one.
Note that the implementation details for the existential collection
"box" classes rely on method overriding of `_map` operations, and the
types are frozen, so we don't get to change their signatures. However,
these are only implementations, not API: the actual API `map`
functions can be upgraded to typed throws.
Note that this code makes use of a known hole in `rethrows` checking
to allow calling between `rethrows` and typed throws. We'll need to do
something about this for source-compatibility reasons, but I'll follow
up with that separately.
With `NoncopyableGenerics` enabled, we currently lose some ability for
associatedtype inference to find a suitable type witness based on a
value witness. (rdar://118998138)
The stdlib accidentally uses that inference for Sequence.Element,
due to the default witness for `_customContainsEquatableElement`
mentioning `Iterator.Element` whereas the requirement only states
`Element`.
This isn't a "complete" port of the standard library for embedded Swift, but
something that should serve as a starting point for further iterations on the
stdlib.
- General CMake logic for building a library as ".swiftmodule only" (ONLY_SWIFTMODULE).
- CMake logic in stdlib/public/core/CMakeLists.txt to start building the embedded stdlib for a handful of hardcoded target triples.
- Lots of annotations throughout the standard library to make types, functions, protocols unavailable in embedded Swift (@_unavailableInEmbedded).
- Mainly this is about stdlib functionality that relies on existentials, type erasure, metatypes, reflection, string interpolations.
- We rely on function body removal of unavailable functions to eliminate the actual problematic SIL code (existentials).
- Many .swift files are not included in the compilation of embedded stdlib at all, to simplify the scope of the annotations.
- EmbeddedStubs.swift is used to stub out (as unavailable and fatalError'd) the missing functionality.
