This commit adds support for range-based for loops using C++ types. It's
currently limited to detecting that `r.begin()` and `r.end()` are
available. We should be able to add full support for methods after #7181
is merged.
Support for ADL is still a work-in-progress, and will be added at a
later time.
---------
Co-authored-by: Richard Smith <richard@metafoo.co.uk>
The removed TODO warned that we'd end up with O(n^2) witness table
entries per specific. This isn't a problem for a single associated
function but will cause issues for larger custom witnesses.
This commit generates at most two `SpecificId`s with an inner `Self`:
one for associated constants and one for associated functions.
---------
Co-authored-by: Dana Jansens <danakj@orodu.net>
When importing a C++ function with an rvalue reference parameter, we
previously produced a Carbon value parameter. This would lead to the
toolchain believing it could pass the address of a non-expiring object
to the function, which would lead to a use-after-move.
Instead, we now map non-const rvalue reference parameters to Carbon
`var` parameters. This forces the object passed into C++ to be unique
and owned by the call. While that's not an exact match for C++ rvalue
reference parameters, given that it provides "always move" not
"conditionally move", it's the closest match we have at the moment.
The existing `GetCoreInterface` has linear-time complexity and adds more
than the search criteria to the `CoreInterfaceCache`. Adding a new field
to `Interface` changes this operation when building packages other than
`Core`, as this should only be set for the core library.
Instead of allowing lower to pick whatever type layout it desires,
compute the layouts of types as part of completing the type, and make
lower build types that match that representation.
For now we assume that all pointers are 64-bit, since we don't have
access to target information. We allow tail padding reuse for structs
and tuple types (and by extension, for classes, since they use structs
as their object representation), but not for arrays.
In order to build matching LLVM types, we create LLVM packed structs
where necessary, and we insert inter-field padding on the end of the
previous field so that GEP indexes still always match Carbon's
ElementIndexes.
We don't yet use the computed alignment much in LLVM IR generation -- in
particular, `alloca`s, `load`s, and `store`s should probably use the
computed type alignment, but don't.
Assisted-by: Gemini via Antigravity
The type must be complete to look for a witness for Destroy. Do this
check through type completion rather than just checking to see if the
ClassInfo says the definition is closed, since completing the type has
side effects (resolves the self specific definition).
Then look for whether the class is abstract through the CompleteTypeInfo
instead of just looking at the inheritance type on ClassInfo, like type
completion does.
Last, FacetTypes are trivially destroyed just like TypeType.
This is only fixing the decision about *whether* to produce a witness.
Implementation of the witness is still a TODO, though where a body is
generated, it should also precisely reflect where one _needs_ to be
generated.
Note the tests:
- toolchain/lower/testdata/function/generic/import_core_witness.carbon
- toolchain/lower/testdata/function/generic/import_unused_def.carbon
These tests can probably be produced _without_ Core.Destroy, but I found
the essence of them while trying to build //examples with Core.Destroy
and a simpler minimization wasn't striking me.
Assisted-by: Google Antigravity with Gemini
---------
Co-authored-by: jonmeow <jperkins@google.com>
Remove special-case handling in conversion logic for C++ enum types,
synthesize a custom witness of `Core.Copy` using the `primitive_copy`
builtin function.
Performing a lookup against `Self` inside the definition of the named
constraint leads to cycles, as described in the document [Self
contradictions in Named
Constraints](https://docs.google.com/document/d/17rn2XmME8o2MM4OJqatSVuMa1iYZ1PAgcNrf0PXR9Q4/edit?tab=t.0).
To prevent those cycles, this change introduces a large refactoring of
impl lookup.
The impl lookup done inside eval is reduced to only performing
monomorphization. That is it:
- Only looks for an provides final witnesses.
- Is not allowed to identify the facet type of the query self.
- Returns either a final witness or None (or an error)
The paths for finding non-final witnesses are now done outside of eval,
directly in the initial `LookupImplWitness()` function. If no final
witness it found through eval, the resulting non-final
`LookupImplWitness` instruction witness is returned. It does not produce
cycles to identify the facet type of query self outside of eval, since
that does not result in repeating the identification when resolving
specifics of the named constraint or require decl.
Move the ArrayStack for Context::require_impls_stack into a new class
which tracks a NamedConstraintId (or InterfaceId) for each frame of
RequireImplsIds, so that in type completion we always can find the
correct frame for a given named constraint which is still being defined,
in order to find the RequireImplsIds in the in-progress definition.
This commit creates an instance for any associated types in an interface
with a custom witness table. This unlocks interfaces designed for C++
interop that rely on arbitrary return types. For example,
`CppUnsafeDeref` becomes usable as of this commit.
This commit may have also implemented support for non-type associated
constants, but since we're lacking a practical test case, they're still
marked as TODO for the time being.
---------
Co-authored-by: Dana Jansens <danakj@orodu.net>
Co-authored-by: Richard Smith <richard@metafoo.co.uk>
We discussed whether associated functions should be processed in a
general manner. Since many associated functions will have some amount of
unique processing, we're probably better off not having a general
utility, and we can return to the original `CoreInterface`, which was
much simpler in design.
This reverts commit 4d0003765d.
Iterators, smart pointers, optional, and expected types depend on
`operator*`. This commit adds `CppUnsafeDeref` as a core interface, with
an associated function, so that the compiler can dereference
user-defined C++ types.
Things not implemented in this commit:
* `operator*` overload resolution
* SemIR lowering
---------
Co-authored-by: Richard Smith <richard@metafoo.co.uk>
Add an `IntFitsIn` interface with a custom witness, such that `T impls
IntFitsIn(U)` if `T` is an integer type all of whose values fit
losslessly into the integer type `U`. Use it to constrain implicit
conversions between integer types.
So far, this has not been extended to the
`CppCompat.[U]{Long32,LongLong64}` types, only to `Core.Int(N)` and
`Core.UInt(N)`.
Assisted-by: Gemini 3 Pro via Antigravity
`LookupCppImpl` is used to find associated functions for a witness. As
some witnesses contain multiple associated functions, we need robust
mechanims for looking up C++ components.
The logic in `LookupCppImpl` is primarily concerned with finding exactly
one C++ declaration at a time. In order to handle witnesses with more
than one associated function, we move the bulk of `LookupCppImpl` to a
new function called `FindCppAssociatedFunction`. This frees up
`CppLookupImpl` to delegate to `FindCppAssociatedFunction` when a
witness has only one associated function, and to functions that are able
to compose multiple associated functions.
---------
Co-authored-by: Geoff Romer <gromer@google.com>
This is iterating on how `Destroy.Op` generates, to start adding body
capabilities. This changes the way the signature is created, and adds a
`CoreWitness` function kind so that mangling can prevent name
collisions. The result is that what _was_ `DestroyOp` is now
`Core.Destroy.Op` or, as can be seen in
toolchain/lower/testdata/interop/cpp/nullptr.carbon,
`_COp.<hash>:core.Destroy.Core` where `:core` is indicating that it's a
core witness (taking a note from `:thunk`).
Assisted-by: Google Antigravity with Gemini 3 Flash
Currently each interface has a `Self` facet internally that becomes a
binding to every entity inside the interface: associated constants,
functions, and require decls. Each of these has to be independently
generic as a result. This makes is challenging in extended name lookup
to move into an extended scope of an interface, as we have a specific
for the interface, but the names within require a different specific
that includes a `Self` facet value.
We generalize this relationship by adding a second generic to Interface,
called `generic_with_self`. When we want to work with entities inside
the interface, we move from the interface-without-specific to the
interface-with-self specific by adding a Self to the specific. This is
done independently of any particular entity inside the Interface, as
those entities are now all members of the interface-with-self generic.
Associated constants no longer need a generic of their own, as they do
not have separate generic bindings. Functions retain a generic, but if
the function has no generic arguments, it will have no bindings of its
own now.
Require decls retain a generic so that their specific can be
instantiated separately from the interface. Requiring the interface to
be complete does not require the types in a require decl to be complete
unless it is modified by `extend`. So we allow them to be completed
later by keeping them in a separate generic.
Named constraints look like interfaces and gain the additional inner
generic-with-self, with the same relationship to require decls.
This removes the need for name lookup to perform Substitution of a Self
facet into the extended scope instruction. Instead, the
`SpecificConstant` instruction inserted by a `require` decl is part of
the interface-with-self generic. When looking through a FacetType for
extended scopes, for each interface, we push the scope with the specific
for the interface-with-self. Then the constant value of the
`SpecificConstant` is correctly modified by the provided self
automatically through applying that specific.
This TODO had been written before C++ types were generating destroy
implementations, which is resolved now.
Assisted-by: Google Antigravity with Gemini 3 Flash
This is related to #6727, but is generally a necessary fix even without
that issue. I'm not adding a specific test of #6727 because it should
also be covered by the tests in #6726.
Assisted-by: Google Antigravity with Gemini 3 Flash
Add a new builtin function `cpp.std.initializer_list.make` that takes an
array and returns a `std::initializer_list`, initialized to refer to
that array. When C++ initialization wants to perform a
`std::initializer_list`-from-array construction, synthesize a
declaration of a matching builtin function and use that to perform the
initialization.
Ideally we would specify this conversion as an impl of `ImplicitAs` in
the prelude instead of hardcoding it in the interop layer, but
unfortunately that's not currently possible, for various reasons -- we
can't make the conversion form-generic, we can't deduce the array length
from the initializer, and we can't deduce against the arguments of
imported C++ class templates yet -- so for now synthesizing a builtin
function on demand is the best we can do.
Assisted-by: Gemini 3 Pro via Antigravity
If an interface contains `require impls`, then implementing the
interface requires each of the `require impls` statements to be true at
the point of the impl definition for the containing interface.
This approach is more robust because there's no intermediate state where
the `ParamPattern` insts have been created, but don't yet have their
final values.
Pursuant to recent decisions on #6124, switch `Destroy` to use a
`CustomWitness` for its implementation. Right now this is manufacturing
no-op implementation functions on each lookup, which obviously isn't
ideal but is intended as a first pass. I'm mostly trying to find the
right balance between updating the approach to reflect new decisions,
while still breaking apart work in a way.
The `CoreInterface` logic is intended to build on `CoreIdentifier`
support. We have a number of additional interfaces that require
specialized logic, and that'll extend pretty far with C++ interop, so it
seemed easiest to have a generic function for it. That's what's
replacing the logic inside C++ interop that was doing string comparisons
(which could have already been moved to `CoreIdentifier`, I just missed
it in my first pass).
This adds `CustomWitness` support because the `Destroy` witnesses can be
imported cross-file. `CustomWitness` was previously only used for C++
types, which don't yet support import, which is why that wasn't
previously an issue. The addition of `query_specific_interface_id` is
similarly needed in order to get correct sorting of witness blocks when
imported.
This PR also removes builtin constraint logic (note this is in a
separate commit to help review; it's not a separate PR because it's
difficult to split apart without tests breaking). This had been made
generic with the expectation that destroy, copy, move, and conversions
would all need related support. Under the new decision, we are not going
to do blanket impls and will instead just manufacture a `CustomWitness`
for everything.
A lot of SemIR fingerprints change, but that's probably because the
addition of `Destroy` on core classes is yielding structural changes.
This delays the conversion of `query_self_const_id` until the actual
witness creation, mainly so that users of `BuildCustomWitness` don't
need to do extra work to ensure `GetFacetAsType` logic is
shared/applied. This is coming up for destroy logic.
We're going to want to track `Destroy` and some other interfaces in ways
similar to what the C++ logic wants. Rather than having both do their
own comparisons with similar values, this tries to centralize logic.
Note the prior
`context.identifiers().Get(interface.name_id.AsIdentifierId())` is also
obsolete due to #6486, this is just replacing it in a single swoop and
avoiding string comparisons as a consequence.
Christopher Di BellaandRichard Smith
Jon Ross-Perkinsandjonmeow
