for plain protocol and protocol composition types.
These types should always be wrapped in ExistentialType, but there isn't
sufficient validation of this throughout the compiler yet. Change
the fatal error when the metadata request sees these plain types to an
assert and restore the old type metadata emission path for protocol and
protocol composition types to avoid crashing in those cases.
I wrote out this whole analysis of why different existential types
might have the same logical content, and then I turned around and
immediately uniqued existential shapes purely by logical content
rather than the (generalized) formal type. Oh well. At least it's
not too late to make ABI changes like this.
We now store a reference to a mangling of the generalized formal
type directly in the shape. This type alone is sufficient to unique
the shape:
- By the nature of the generalization algorithm, every type parameter
in the generalization signature should be mentioned in the
generalized formal type in a deterministic order.
- By the nature of the generalization algorithm, every other
requirement in the generalization signature should be implied
by the positions in which generalization type parameters appear
(e.g. because the formal type is C<T> & P, where C constrains
its type parameter for well-formedness).
- The requirement signature and type expression are extracted from
the existential type.
As a result, we no longer rely on computing a unique hash at
compile time.
Storing this separately from the requirement signature potentially
allows runtimes with general shape support to work with future
extensions to existential types even if they cannot demangle the
generalized formal type.
Storing the generalized formal type also allows us to easily and
reliably extract the formal type of the existential. Otherwise,
it's quite a heroic endeavor to match requirements back up with
primary associated types. Doing so would also only allows us to
extract *some* matching formal type, not necessarily the *right*
formal type. So there's some good synergy here.
`readonly` (instead of `readnone`) because we want there to be a memory control
dependence on potential preceeding availability checks.
`willreturn` such that LLVM can remove calls without a use.
Starting with Android 11, AArch64 placed a tag in the top byte of pointers to
allocations, which has been slowly rolling out to more devices and collides
with Swift's tags. Moving these tags to the second byte works around this
problem.
There are three major changes here:
1. The addition of "SILFunctionTypeRepresentation::CXXMethod".
2. C++ methods are imported with their members *last*. Then the arguments are switched when emitting the IR for an application of the function.
3. Clang decls are now marked as foreign witnesses.
These are all steps towards being able to have C++ protocol conformance.
A PackExpansionType is the interface type of the explicit expansion of a
corresponding set of variadic generic parameters.
Pack expansions are spelled as single-element tuples with a single variadic
component in most contexts except functions where they are allowed to appear without parentheses to match normal variadic declaration syntax.
```
func expand<T...>(_ xs: T...) -> (T...)
~~~~ ~~~~~~
```
A pack expansion type comes equipped with a pattern type spelled before
the ellipses - `T` in the examples above. This pattern type is the subject
of the expansion of the pack that is tripped when its variadic generic
parameter is substituted for a `PackType`.
A pack type looks a lot like a tuple in the surface language, except there
is no way for the user to spell a pack. Pack types are created by the solver
when it encounters an apply of a variadic generic function, as in
```
func print<T...>(_ xs: T...) {}
// Creates a pack type <String, Int, String>
print("Macs say Hello in", 42, " different languages")
```
Pack types substituted into the variadic generic arguments of a
PackExpansionType "trip" the pack expansion and cause it to produce a
new pack type with the pack expansion pattern applied.
```
typealias Foo<T...> = (T?...)
Foo<Int, String, Int> // Forces expansion to (Int?, String?, Int?)
```
The new type, called ExistentialType, is not yet used in type resolution.
Later, existential types written with `any` will resolve to this type, and
bare protocol names will resolve to this type depending on context.
The functions in llvm-project `AttributeList` have been
renamed/refactored to help remove uses of `AttributeList::*Index`.
Update to use these new functions where possible. There's one use of
`AttrIndex` remaining as `replaceAttributeTypeAtIndex` still takes the
index and there is no `param` equivalent. We could add one locally, but
presumably that will be added eventually.
One of the places where we ask whether a type's metadata should
be obtained via its mangled name was missing the newer, more
robust checking for minimum deployment target.
When back-deploying, create global-actor-qualified function types via a
separate entrypoint
(`swift_getFunctionTypeMetadataGlobalActorBackDeploy`) in the
compatibility library, which checks whether it is running with a
new-enough runtime to use `swift_getFunctionTypeMetadataGlobalActor`.
Failing that, it calls into a separate copy of the implementation that
exists only in the back-deployed concurrency library.
Fixes rdar://79153988.
Classes using the type-erased Objective-C generics model are represented in parts of IRGen as UnboundGenericTypes, which is a problem because a number of code paths expect all generic types to be bound. Update some of these that are involved in extensions on ObjC generic types.
Isolated parameters are part of function types. Encode them in function
type manglings and metadata, and ensure that they round-trip through
the various mangling and metadata facilities. This nails down the ABI
for isolated parameters.
