API development sometimes requires a redesign while supporting early
adopters. Currently this is done by adding @_spi(name) to the API but
that requires adding the attribute in import statements as well, causing
manual overhead of adding and then removing when the redesign is done.
This PR introduces a special spi group name '_' and allows an implicit
spi import of a module containing API attributed with '@_spi(_)'
Resolves rdar://109797632
There's no need to check for that here, because we also run
diagnoseDeclRefExportability() on declarations referenced
from inlinable code.
This changes some diagnostics; we now produce the same diagnostic
for references to SPI types in declaration signatures and for
references to non-type SPI declarations in inlinable function bodies.
Also note that the old inlinable reference diagnostic no longer has
to handle the 'public' and 'open' access levels, which previously
happened for '@_spi'; so I changed those entries in the %select to
%error.
Availability checking already knows how to check exportability for
types and conformances referenced from inlinable function signatures
and bodies.
Let's generalize this to work on non-inlinable function signatures
as well, allowing us to get rid of the ExportabilityChecker altogether.
We used to diagnose references to unavailable declarations in
two places:
- inside Exprs, right after type checking the expression
- inside TypeReprs, from resolveType()
In broad terms, resolveType() is called with TypeReprs
stored inside both Stmts and Decls.
To handle the first case, I added a new overload of
diagAvailability() that takes a Stmt, to be called from
typeCheckStmt(). This doesn't actually walk into any Exprs
stored inside the statement; this means it only walks
Patterns and such.
For the second case, a new DeclAvailabilityChecker is
now defined in TypeCheckAccess.cpp. It's structure is
analogous to the other three walkers there:
- AccessControlChecker
- UsableFromInlineChecker
- ExportabilityChecker
The new implementation of availability checking for types
introduces a lot more code than the old online logic
it replaces. However, I hope to consolidate some of the
code duplication among the four checkers that are defined
in TypeCheckAccess.cpp, and do some other cleanups that
will make the benefit of the new approach apparent.
Remove the fast path skipping evaluating SPI groups for non-public
decls. This knowledge is still required to allow the use of SPI types in
the signatures of `@usableFromInline` declarations and in internal
properties of structs in non library evolution compilation.
rdar://68530659
rdar://68527580
