Find all the usages of `--enable-experimental-feature` or
`--enable-upcoming-feature` in the tests and replace some of the
`REQUIRES: asserts` to use `REQUIRES: swift-feature-Foo` instead, which
should correctly apply to depending on the asserts/noasserts mode of the
toolchain for each feature.
Remove some comments that talked about enabling asserts since they don't
apply anymore (but I might had miss some).
All this was done with an automated script, so some formatting weirdness
might happen, but I hope I fixed most of those.
There might be some tests that were `REQUIRES: asserts` that might run
in `noasserts` toolchains now. This will normally be because their
feature went from experimental to upcoming/base and the tests were not
updated.
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.)
Besides being an optimization, using memcpy directly rather than a value
witness is required in order to interact with unaligned instances of
such types: the value witness functions expect their arguments to be
aligned.
rdar://96919870
