- Don't allow @_inlineable on stored properties; this generates
invalid SIL since clients can't know about stored properties of
resilient types. Accessors for stored properties of non-resilient
types are already @_inlineable anyway.
- Don't allow @_inlineable on declarations that are not public or
@_versioned, since it's simply redundant.
Protocol members can be directly referenced from protocol extensions
and generic functions. Since protocol members do not have accessibility
distinct from the protocol itself, ignore them, since they won't carry
the @_versioned attribute.
While workign on this I uncovered an interesting bug where we allow
members of protocol extensions to be more accessible than the protocol
itself, but then we give the symbols hidden visibility at the SIL level
anyway.
I filed <https://bugs.swift.org/browse/SR-3684> to track this issue.
Piggybacks some resilience diagnostics onto the availability
checking code.
Public and versioned functions with inlineable bodies can only
reference other public and internal entities, since the SIL code
for the function body is serialized and stored as part of the
module.
This includes @_transparent functions, @_inlineable functions,
accessors for @_inlineable storage, @inline(__always) functions,
and in Swift 4 mode, default argument expressions.
The new checks are a source-breaking change, however we don't
guarantee source compatibility for underscored attributes.
The new ABI and tests for the default argument model will come in
subsequent commits.
