**Overview**:
This PR introduces the basic infrastructure needed to eventually migrate
derived macros generation from hand-crafted AST nodes to macros. No
conformance have been migrated yet.
**Motivation**:
Derived conformances (e.g. `Equatable`, `Hashable`, `Codable`, ...) are
currently implemented as a special case in the compiler, producing
synthetic AST nodes directly. Migrating this to macros will hopefully
unify the code path with the existing macro expansion infrastructure,
make conformance synthesis easier to extend and test as well as reducing
the amount of special cases in the compiler.
**Changes**:
- New experimental feature flag `DeriveConformancesViaMacros`:
Introduces the flag that will eventually gate the new derived
conformance code paths. It does not control any behaviour for the moment
as none have been migrated yet but this enables future changes to be
built incrementally.
- New GeneratedSourceInfo and SourceFile kinds `SyntheticMacro`:
Introduces new GSI and SourceFile kinds named `SyntheticMacro` to
represent macros synthesized by the compiler. Since macros need a real
buffer to expand, this is the kind of source file and GSI associated
with those buffers.
- Conformance derivation via macros API:
Introduces the `deriveRequirementViaMacro` function that produces the
required witness via macro expansion.
See https://github.com/swiftlang/llvm-project/pull/13124 for
llvm-related changes.
**Next steps**:
- Macros do not contain any semantic information, especially regarding
types. Therefore it is necessary to provide them with type information
as an argument so they can eventually derive the conformances. A
separate PR is being created to generate this type information as
strings containing swift-parsable code for easy parsing on the macro
end.
- Implement derived conformance synthesis for individual protocols using
the new infrastructure, like `Equatable` or `Hashable` for starters.
- Wire the experimental flag to gate the new path once an implementation
exists
---------
Co-authored-by: Hamish Knight <hamish_knight@apple.com>
When a case statement body inside a switch statement is only reachable if a
specific enum element matches the switch subject, the compiler now generates an
availability scope for the case body that matches the availability of the enum
element:
```
@available(macOS 26, *)
func f() -> Int { 0 }
enum E {
@available(macOS 26, *)
case a
}
func multiplex(_ e: E) -> Int {
switch e {
case .a:
return f() // OK, .a is only available in macOS 26
}
}
```
Supporting the same refinement for cases in switch expressions will need to be
handled as a follow-up as it may require changes to the order in which switch
expression case bodies are type checked relative to the case label.
Resolves https://github.com/swiftlang/swift/issues/46662 and rdar://20937722.
When an `if #unavalable` statement also includes a secondary (non-availability)
condition, the availability scope for the else branch should not be refined.
The else branch can be reached because the secondary condition failed, in which
case the availability condition may not hold.
Resolves rdar://165863221.
Extending type-checking to non-public decls triggered new errors when
`-target-min-inlining-version min` is enabled. Ensure these checks are only
applied to explicitly exported decls.
Affected test: test/Concurrency/deinit_isolation_availability.swift
When emitting SIL for `if #available(Swift ..., *)` queries, call the new
`_isSwiftRuntimeVersionAtLeast()` function in the stdlib to check the
condition. To support back deployment, the implementation of
`_isSwiftRuntimeVersionAtLeast()` is `@_alwaysEmitIntoClient` and performs its
comparison against the result of `_SwiftStdlibVersion.current`, which is
pre-existing ABI that the stdlib exposes for querying the Swift runtime
version.
Resolves rdar://162726037.
Add support for the `Swift` availability domain, which represents availability
with respect to the Swift runtime. Use of this domain is restricted by the
experimental feature `SwiftRuntimeAvailability`.
An always enabled availability domain is implicitly available in all contexts,
so uses of declarations that are marked as `@available` in the domain are never
rejected. This is useful for an availability domain representing a feature flag
that has become permanently enabled.
Partially resolves rdar://157593409.
Previously, whether a declaration is unavailable because it is obsolete was
determined based solely on the deployment target and not based on contextual
availability. Taking contextual availability into account makes availability
checking more internally consistent and allows library authors to evolve APIs
by obsoleting the previous declaration while introducing a new declaration in the
same version:
```
@available(macOS, obsoleted: 15)
func foo(_ x: Int) { }
@available(macOS, introduced: 15)
func foo(_ x: Int, y: Int = 0) { }
foo(42) // unambiguous, regardless of contextual version of macOS
```
This change primarily accepts more code that wasn't accepted previously, but it
could also be source breaking for some code that was previously allowed to use
obsoleted declarations in contexts that will always run on OS versions where
the declaration is obsolete. That code was clearly taking advantage of an
availabilty loophole, though, and in practice I don't expect it to be common.
Resolves rdar://144647964.
Get rid of the boolean arguments for unavailability in AvailabilityQuery's
constructors and introduce a `asUnavailable()` modifier that can be used
instead in the contexts where unavailability is relevant.
Use these queries to replace some duplicated code. Also, move the
`attr_inlinable_available.swift` test to the `Availability` sub-directory since
the test has more to do with availability checking than it has to do
specifically with the `@inlinable` attr.
Inverted availability queries were mis-compiled for zippered libraries because
the code that emits calls to `isOSVersionAtLeastOrVariantVersionAtLeast()` was
not updated when the `if #unavailable` syntax was introduced (at that time
support for zippered libraries had not yet been upstreamed). The result of
these calls is now inverted when appropriate.
To make it easier to manage the growing complexity of supporting availability
queries, Sema now models the relevant information about an availability query
with the new `AvailabilityQuery` type. It encapsulates the domain for the
query, the result if it is known at compile time, and the version tuple
arguments to pass to a runtime invocation if applicable.
Resolves rdar://147929876.
Expand the special-cased ASTWalker behavior for folded SequenceExprs
such that we always walk the folded expression when available. This
ensures that we don't attempt to add the same node multiple times
when expanding ASTScopes during pre-checking.
rdar://147751795
Allan Shortlidge
Paul Passeron
Alexis Laferrière
Hamish Knight