Upgrade the old mangling from a list of argument types to a
list of requiremnets. For now, only same-type requirements
may actually be mangled since those are all that are available
to the surface language.
Reconstruction of existential types now consists of demangling (a list of)
base protocol(s), decoding the constraints, and converting the same-type
constraints back into a list of arguments.
rdar://96088707
It used to be an accessor but that is not required because
SILDeclRef controls mangling which is the most imprortant
and could be used to emit the right reference.
If a function's parameter or return types involve nominal types that
have been moved across modules using @_originallyDefinedIn, we must
take care to always mangle the opaque result type's name using the
original module names and not the current module names.
This was a problem with DWARF mangling, which normally disables
@_originallyDefinedIn for other purposes. Make sure to always
temporarily re-enable it when mangling an opaque result type.
Fixes rdar://problem/93822207.
These opened archetypes need to be bound within their context, so any mapping out of
the context will need to be explicit and map to newly-created generic parameters.
The RequirementSignature generalizes the old ArrayRef<Requirement>
which stores the minimal requirements that a conforming type's
witnesses must satisfy, to also record the protocol typealiases
defined in the protocol.
Introduce the `@preconcurrency` attribute name for `@_predatesConcurrency`,
which has been the favored name in the pitch thread so far. Retain the
old name for now to help smooth migration.
Nested archetypes are represented by their base archetype kinds (primary,
opened, or opaque type) with an interface type that is a nested type,
as represented by a DependentMemberType. This provides a more uniform
representation of archetypes throughout the frontend.
The `Qr` mangling is used to refer to the opaque type within the
declaration that produces the opaque type. When there are multiple
opaque types, e.g., due to structural or named opaque result types, it
does not specify which of the opaque type parameters it refers to.
Introduce a new mangling `QR INDEX` for opaque type parameters after
the first, retaining the `Qr` mangling for the first opaque type
parameter. This way, existing (non-structural) uses of opaque result
types retain the same manglings, but uses of structural or named
opaque result types (new features) will have distinct manglings.
Note that this mangling within a declaration is only used for the
declaration itself, and not for references to the opaque type of the
declaration, so there is no impact on the runtime demangler.
mangleOpaqueTypeDecl() used to enable DWARFMangling, which
ignores @_originallyDefinedIn, which would in turn break module
interfaces.
Fixes rdar://problem/86480663.
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.
The refactoring that moved the substitution of the outer environment
into an opaque type archeptype into the generic environment eliminated
the need for the bound signature entirely, so remove it.
We were always mangling based on the last generic parameter, which
makes sense when there is only one opaque result type, but is
incorrect when there are multiple opaque result types, e.g., due to
named or structural opaque result types.
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.
