Using availability domains, reimplement the algorithm that determines whether a
declaration is unavailable at runtime. The new algorithm takes ABI compatible
platforms into account, ensuring that declarations that are available on iOS do
not get treated as unreachable at runtime when compiling for visionOS.
Resolves rdar://116742214.
When diagnosing a declaration that is more available than its context, to
preserve source compatibility we need to downgrade the diagnostic to a warning
when the outermost declaration is an extension. This logic regressed with
https://github.com/swiftlang/swift/pull/77950 and my earlier attempt to fix
this (https://github.com/swiftlang/swift/pull/78832) misidentified what had
regressed.
Really resolves rdar://143423070.
In https://github.com/swiftlang/swift/pull/78454 queries for the platform
availability of decl were consolidated into
`Decl::getAvailableAttrForPlatformIntroduction()`. In addition to checking the
attributes directly attached to the decl, this method also checks whether the
decl is a member directly contained inside of an extension and checks for
attributes attached to the extension as well. Previously, this logic was only
used for availability checking diagnostics, where special casing extension
members was a requirement. As a result of the consolidation, though, the logic
is now also shared by the query that determines whether to weakly link symbols
associated with a decl. That determination already had its own way of handling
members of extensions but it seemed like consolidating the logic would stil be
a net improvement that would reduce overall complexity.
Unfortunately, the existing approach to getting the availability of the
enclosing extension had a subtle bug for both AccessorDecl and OpaqueTypeDecl.
If an AvailableAttr was not directly attached to the immediate decl, then
`Decl::getAvailableAttrForPlatformIntroduction()` would check if the enclosing
decl context was an extension and look at its attributes as well. For
AccessorDecl and OpaqueTypeDecl, checking the enclosing decl context would
accidentally skip over the VarDecl and AbstractFunctionDecl that are formally
the parents of those decls for the purposes of attribute inheritance. As a
result, the availability of the enclosing property or function could be ignored
if the enclosing extension had explicit availability attributes.
The fix is to use `AvailabilityInference::parentDeclForInferredAvailability()`
instead of `getDeclContext()` when looking for the immediately enclosing
extension.
Resolves rdar://143139472.
Representing introduced, deprecated, and obsoleted versions at rest as optional
version tuples is redundant, since the empty version tuple already represents
"version not present".
NFC.
This request will finish type checking an AvailableAttr by resolving its domain
and then enforcing any restrictions that the domain has on the attribute, like
disallowing version specifications.
This change just introduces the request and plumbs it through. NFC.
Most of the compiler should use SemanticAvailableAttr instead. In contexts like
ASTDumper where a semantic attribute is unavailable use accessors on
AvailableAttr.
NFC.
Now that AvailableAttr has storage for its cached AvailabilityDomain, it's no
longer necessary to store an AvailabilityDomain inline in
SemanticAvailableAttr.
NFC.
It was difficult to preserve the existing, buggy behavior of availability
attribute inference with respect to attributes specifying availability for
non-platform-specific domains. Instead, this change improves attribute merging
by tracking every domain independently, and only merging attributes from the
same domain.
Put AvailabilityRange into its own header with very few dependencies so that it
can be included freely in other headers that need to use it as a complete type.
NFC.
This convenience returns an optional `SemanticAvailableAttr` (since in the
future, lookup of the `AvailabilityDomain` can fail). It replaces
`Decl::getDomainForAvailableAttr()`, since most callers will need to form a
`SemanticAvailableAttr` with the resulting domain anyways.
This new attribute iterator returned from the query makes it simpler to
implement algorithms that need access to both the `AvailableAttr *` and its
corresponding `AvailabilityDomain`. This is also work towards making it
possible to return an optional `AvailabilityDomain` from
`Decl::getDomainForAvailableAttr()`.
This query's functionality was not useful enough to be exposed on `Decl` and
cached in the request evaluator. Instead, just share a local implementation of
it in `TypeCheckAttr.cpp`.
Also remove the underlying `SemanticUnavailableAttrRequest`, which used memory
very inefficiently in order to cache a detailed answer to what was usually a
much simpler question.
The only remaining use of `Decl::getSemanticUnavailableAttr()` that actually
needed to locate the semantic attribute making a declaration unavailable was in
`TypeCheckAttr.cpp`. The implementation of the request could just be used
directly in that one location. The other remaining callers only needed to know
if the decl was unavailable or not, which there are simpler queries for.
# Please enter the commit message for your changes. Lines starting
It replaces `DeclAttr::getUnavailable()` and `AvailableAttr::isUnavailable()`
as the designated way to query for the attribute that makes a decl unavailable.
The renamed decl is now stored exclusively in the split request evaluator
storage, which is more efficient since most availability attributes do not
specify a renamed decl.
