We introduce a new macro called #SwiftSettings that can be used in conjunction
with a new stdlib type called SwiftSetting to control the default isolation at
the file level. It overrides the current default isolation whether it is the
current nonisolated state or main actor (when -enable-experimental-feature
UnspecifiedMeansMainActorIsolated is set).
If the precondition doesn't hold, we will return a pointer to
some random memory, so it's best to always crash since this
indicates something is seriously wrong.
The `unchecked_ref_cast` is designed to be able to cast between
`Optional<ClassType>` and `ClassType`. We need to handle these cases by
checking if the type is optional and adjust the path accordingly.
When printing diagnostics, category names are printed as [#<category-name>]
at the end of a diagnostic. For all of the category names that are mentioned
in this manner, print "footnotes" at the end of compilation providing
documentation references to each category, e.g.,
[#deprecated]: <http://example.com/deprecated>
[#StrictMemorySafety]: <http://example.com/memory-safety>
Right now, these point into the markdown files in the installed toolchain,
same as the URLs behind references. That is subject to change in the future.
Replace the pair of global actor type/conformance we are passing around with
a general "conformance execution context" that could grow new functionality
over time. Add three external symbols to the runtime:
* swift_conformsToProtocolWithExecutionContext: a conforms-to-protocol check
that also captures the execution context that should be checked before
using the conformance for anything. The only execution context right now
is for an isolated conformance.
* swift_isInConformanceExecutionContext: checks whether the function is
being executed in the given execution context, i.e., running on the
executor for the given global actor.
* swift_ConformanceExecutionContextSize: the size of the conformance
execution context. Client code outside of the Swift runtime can allocate
a pointer-aligned region of memory of this size to use with the runtime
functions above.
In the prior implementation of runtime resolution of isolated conformances,
the runtime had to look in both the protocol conformance descriptor and
in all conditional conformance requirements (recursively) to find any
isolated conformances. If it found one, it had to demangle the global
actor type to metadata. Since swift_conformsToProtocol is a hot path through
the runtime, we can't afford this non-constant-time work in the common
case.
Instead, cache the resolved global actor and witness table as part of the
conformance cache, so that we have access to this information every time
we look up a witness table for a conformance. Propagate this up through
various callers (e.g., generic requirement checking) to the point where
we either stash it in the cache or check it at runtime. This gets us down
to a very quick check (basically, NULL-or-not) for nonisolated conformances,
and just one check for isolated conformances.
Following the approach taken with the concurrency-specific type
descriptors, register a hook function for the "is current global actor"
check used for isolated conformances.
Extend the metadata representation of protocol conformance descriptors
to include information about the global actor to which the conformance is
isolated (when there is one), as well as the conformance of that type to
the GlobalActor protocol. Emit this metadata whenever a conformance is
isolated.
When performing a conforms-to-protocol check at runtime, check whether
the conformance that was found is isolated. If so, extract the serial
executor for the global actor and check whether we are running on that
executor. If not, the conformance fails.
When deserialization a protocol conformance from a binary swiftmodule
file the compiler can encounter inconsistencies caused by stale module
files. Replace the hard crash with a proper error and print the list of
requirements and conformances being compared to stderr for manual
inspection. Recover silently when we can afford to, during indexing or
in LLDB.
Failures in `readNormalProtocolConformanceXRef` are usually caused by a
dependency change without the required rebuild of its dependents.
Display a proper error instead of crashing when encountering such an
issue during normal compilation. Recover silently when we can afford to,
during indexing or in LLDB.
Introduce a new deserialization mode `enableExtendedDeserializationRecovery`
for use when we can afford inconsistent information from a swiftmodule
file. It's enabled automatically in debugger mode, when user errors are
allowed and during index-while-building.
