When `-unavailable-decl-optimization=stub` is specified, insert a call to
`_diagnoseUnavailableCodeReached()` at the beginning of the function to cause
it to trap if executed at run time.
Part of rdar://107388493
This let the optimizer generate efficient code for generic array loops (note that generic functions are not inlined by default).
Note that the same change is not done for `Array` because this might increase code size due to Array's bridging code.
rdar://108746069
Types that have "value semantics" should not have lexical lifetimes.
Value types are not expected to have custom deinits. Are not expected to
expose unsafe interior pointers. And cannot have weak references because
they are structs. Therefore, deinitialization barriers are irrelevant.
rdar://107076869
The _Copyable constraint was implemented as a marker protocol.
That protocol is part of the KnownProtocol's in the compiler.
When `ASTContext::getProtocol(KnownProtocolKind kind)` tries
to find the ProtocolDecl for Copyable, it will look in the
stdlib module (i.e., Swift module), which is where I initially
planned to put it.
That created problems initially when some regression tests
use `-parse-stdlib` failed to do that protocol lookup, which is
essential for adding the constraint (given the current implementation).
That led to believe we need to pull Copyable out of the stdlib, but that's
wrong. In fact, when building the Swift module itself, we do `-parse-stdlib`
but we also include `-module-name Swift`. This causes the _Copyable protocol
defined in the Stdlib to be correctly discovered while building the stdlib
itself (see the test case in this commit). So, the only downside of
having the Copyable protocol in the Stdlib is that `-parse-stdlib` tests
in the compiler can't use move-only types correctly, as they'll be
allowed in generic contexts. No real program would build like this.
Until I have time to do a further refactoring, this is an acceptable trade-off.
fixes rdar://104898230
Users should not do this:
class C {
func getRetained() {
let unmanaged = Unmanaged.passUnretained(self)
//... maybe some condition
unmanaged.retain()
}
}
But that should be obvious, and apparently this comment doesn't help.
Unmanaged.passRetained was originally implemented as:
- store the passed referenced into an unowned(unsafe) reference
- (the reference will now be released if the store is the last use)
- reload the unowned(unsafe) reference
- retain the reloaded reference
It should be implemented as:
- retain the passed reference
- store the passed reference to an unowned(unsafe) reference
Fixes rdar://105609600
(🔥 non-deterministic miscompile in stdlib's
_StringGuts.populateBreadcrumbs)
