The SymbolicBindingType refers to the type value that will be
substituted in for the BindSymbolicName, but holds onto the EntityNameId
from the BindSymbolicName instead of (or in addition to, for now) the
instruction.
The EntityNameId will be used to look in the ScopeStack to find the
witnesses either from the BindSymbolicName instruction, or other
instructions that specify `impls` constraints against the EntityName.
This will allow us to have the `T` in `I(T)` resolve to a `.Self`
reference in the type so that we get type equality with the binding's
type: `T:! I(.Self)`.
Previously it performed two kinds of operations, with a boolean
parameter to control whether it would unwrap FacetValue or not. This
made the function hard to explain as "canonicalization".
Now the contract of GetCanonicalFacetOrTypeValue is as follows:
1. For a facet value expression, it returns the canonical value of the
facet value.
2. For a `<facet value> as type` it returns the canonical value of the
`<facet value>`.
3. For other type expressions, it returns the canonical value of the
type.
1 and 2 together collapse together two representations of a facet value
(as a FacetType or as a TypeType) into a single canonical value, which
is important for constant comparison of facet values where the `as type`
is not meant to change the result. This is the case in impl lookups and
`.Self` comparisons.
The step of unwrapping `FacetValue` is only useful in the constant
evaluation of `LookupImplWitness` and is used to collapse *symbolic*
queries on `FacetValue(T)` and on `T` down to a single canonical value,
since they produce the same result later when `T` is replaced with a
facet value or type that can provide a concrete witness. This is now
extensively documented in the constant evaluation of
`LookupImplWitness`.
This change came out of a request/discussion in #6115 (see comment
https://github.com/carbon-language/carbon-lang/pull/6115#discussion_r2383696576).
As proposed in [Carbon: C++ interop for overloaded functions and
function
templates](https://docs.google.com/document/d/1KUxumZtNe3mY3TsjW2s_ZADOlAaFlrtsLKHVILtqIaM/edit?tab=t.0),
Clang is used to perform the overload resolution using C++ rules, when
an overloaded C++ set is called from Carbon. Once a function is
selected, it's converted into a Carbon function and called using the
Carbon rules including argument conversions.
A single non-templated function is treated the same way as an overload
set and the same rules apply for its call.
Template functions are not supported yet.
Demo:
a) Non-templated function calls:
```c++
// --- overloads.h
auto foo(int a, short b) -> void;
auto foo(double a) -> void;
auto foo(int a) -> void;
```
```c++
// overloads.cpp
#include "overloads.h"
#include <cstdio>
auto foo(int a, short b) -> void {
printf("hello from foo_int_short(%d, %d) \n", a, b);
}
auto foo(double a) -> void { printf("hello from foo_double(%f) \n", a); }
auto foo(int a) -> void { printf("hello from foo_int(%d) \n", a); }
```
```c++
library "Main";
import Cpp library "overloads.h";
fn Run() -> i32 {
Cpp.foo(1.1 as f64);
return 0;
}
```
```
$ clang -c overloads.cpp
$ bazel-bin/toolchain/carbon compile main.carbon
$ bazel-bin/toolchain/carbon link overloads.o main.o --output=demo
$ ./demo
hello from foo_double(1.100000)
```
b) Constructors:
```c++
// --- constructor_overloads.h
class C {
public:
C();
C(int a, int b);
};
```
```c++
// constructor_overloads.cpp
#include "constructor_overloads.h"
#include <cstdio>
C::C() { printf("hello from C() \n"); }
C::C(int a, int b) { printf("hello from C(%d, %d) \n", a, b); }
```
```c++
library "Main";
import Cpp library "constructor_overloads.h";
fn Run() -> i32 {
let c1: Cpp.C = Cpp.C.C();
let c2: Cpp.C = Cpp.C.C(1, 2);
return 0;
}
```
```
$ clang -c constructor_overloads.cpp
$ bazel-bin/toolchain/carbon compile main.carbon
$ bazel-bin/toolchain/carbon link constructor_overloads.o main.o \--output=demo
$ ./demo
hello from C()
hello from C(1, 2)
```
Follow-ups:
- `Cpp.foo({})` - proper handling of struct literals as call args.
- Fix access for overloaded sets.
- Fix tests:
- Method calls: `error: missing object argument in method call
[MissingObjectInMethodCall]` in tests.
- Fix `toolchain/check/testdata/interop/cpp/import.carbon` test.
- Fix `enums` support.
- Fix `str` -> `std::string_view` mapping.
Part of #5915
This is a bit of an experiment to see if there's a reasonable way to
write a shared enum type, rather than writing per-case wrappers for
things like `HasTypeQualifiers` or the printing. I think it's a bit
borderline complexity right now, but I'm not sure I can reduce it much
further.
This changes from things like `Internal::EnumClassName##RawEnum` to
`Internal::EnumClassName##Data::RawEnum` so that the enum entries can
have back references to bit shifts without needing to know the
containing type name. Because I'm trying to reduce duplication between
mask and non-mask enums, I did this to non-mask enums too.
This was motivated by #6035 adding another enum mask (which will grow
more entries, and is intended to switch if this is accepted), but I'm
not using that PR as a base here because I didn't want the merge
dependency.
* Treat `MaybeUnformed` and `partial` as qualifiers, like `const`.
* Allow pointer conversions to add qualifiers.
* Allow unsafe pointer conversions to remove qualifiers.
* Allow conversions on non-reference expressions to drop `const`.
* Allow unsafe conversions on any expression to drop `const`.
* Allow unsafe conversions on non-initializing expressions to drop
`partial`. For initializing expressions, we should initialize the
vptr when dropping `partial`; this is not yet supported so we reject.
* Allow conversions on reference expressions to add `MaybeUnformed`.
* Allow unsafe conversions on reference expressions to drop
`MaybeUnformed`. For non-reference expressions, additional work is
required, because the value / initializing representation may not
match between `T` and `MaybeUnformed(T)`, so those are rejected for
now.
Generalize the f64 support to support other sizes. Also provide interop
support for `float`, `_Float16`, and `__float128`.
Also lay some groundwork for non-standard floating-point types, though
we don't have any syntax to name them yet.
This makes all `.Self` references in a facet type canonically the same
(which will remain true iff they refer to the same `Self` type in the
future), removing the need to do more complex comparisons between them
using the EntityName, interface, and index. This allows the comparison
of types containing `.Self` references to be done correctly regardless
of where the `.Self` appears, as such type expressions will all be
canonically equal if they otherwise equal now, regardless of whether
they are written in the context where `.Self` could have seen different
`Self` facet types.
In order to retain access to constraints on a base `.Self` facet type,
in the case of applying `where` to an existing facet type, we:
- Give the base facet type as a `RequirementBaseFacetType` constraint so
that eval of `WhereExpr` can find and copy all the constraints off of
it.
- Introduce eager/early rewrite constraint resolution, which allows a
constraint to eagerly resolve access to earlier rewrite constraints
(`where .A = () and .B = .A` is eagerly transformed into `where .A = ()
and .B = ()`) before the full constraint resolution step. This allows
use of rewrite constraints in larger type expressions, such as `where .A
= () and .B = C(.A)` and `C` will know that the argument is `()`.
Incidentally also supports import of pointers-to-pointers.
Imported const-qualified types aren't especially useful just yet,
because on the Carbon side we don't yet permit conversions from
non-const to const types, so most of the tests still fail, but for
different reasons now.
We eliminate the `FacetAccessWitness` instruction, which would sometimes
immediately evaluate to a concrete `ImplWitness`, and sometimes remain
symbolic. This instruction is now replaced by `LookupImplWitness` in all
cases. To support the same use cases, when it is evaluated,
`LookupImplWitness` will look in the self value if it's a facet value,
and attempt to return a concrete `ImplWitness` from it before looking
for an `impl` statement.
The `LookupImplWitness` instruction's value is now canonical, even when
it evaluates to a symbolic `LookupImplWitness` instruction, by
canonicalizing the self value of the lookup query. This canonicalization
unwraps `FacetAccessType` and `FacetValue` instructions to get to an
underlying canonical facet value. However we must preserve and use the
non-canonical query while evaluating the instruction in order to look
for a concrete `ImplWitness` if the query self value was a concrete
`FacetValue`. The canonicalization ensures that symbolic witnesses
obtained from a facet value are compatible with those obtained from an
impl statement, as long as the self types originate from the same
canonical facet value though they may have been narrowed.
Member access now unconditionally does a `LookupImplWitness()`
operation, instead of only sometimes doing the lookup for a final impl
declaration.
`EvalImplLookupResult` is marked `[[nodiscard]]` so that we don't
construct it and forget to return it. This was a mistake made at one
point during the creation of this PR. And the `has_concrete_value()`
method no longer has a precondition that `has_value()` is true, since we
want to look for a concrete result only in the new use of
`EvalImplLookupResult` returned from lookup into the query self facet
value.
The TODO from `FacetAccessWitness` evaluation is addressed by ensuring
the index of the witness in the `FacetValue` comes from the required
interfaces of the `FacetValue`'s type, and that the type (a `FacetType`)
is the same facet type used in the query to construct the `FacetValue`'s
witness block. This is made possible by eliminating the
`FacetAccessWitness` indirection. The lookup into a `FacetValue` happens
while evaluating `LookupImplWitness` and it does so directly on the self
value. This gives a consistent view of the witness set and the facet
type, as they both come from the same instruction.
All of this with 400 less lines of code. :)
---------
Co-authored-by: josh11b <15258583+josh11b@users.noreply.github.com>
Co-authored-by: Richard Smith <richard@metafoo.co.uk>
We frequently want to operate on singletons. Per discussion, drop
`Singleton` to make the code shorter.
This started off as wanting to write `inst_id.is_error()`, but the
dependency relationship between ids.h and singleton_insts.h would
require some kind of delayed evaluation to allow the implementation to
remain in headers (which I suspect is helpful to have for inlining). I
could have added something like `IsErrorInst`, forward declared in ids.h
and defined in singleton_insts.h (which would always be included by
typed_insts.h), but the template approach felt like a decent balance
between (a) removing the boilerplate `::SingletonInstId`, (b)
understandability, (c) still visually mirroring if we immediately return
a singleton, and (d) flexibility for more than just `ErrorInst`. But TBH
I'd probably still have written `is_error()` if it didn't require
addressing the cross-header cycle.
Then I tried `SemIR::InstId::Is<SemIR::ErrorInst>`, which generally
worked with types but generated the complaint that it didn't shorten
*all* singleton uses. So pulling back on `::Is`, and instead just
dropping `Singleton`.
Use TypeInstId in many more places where the instruction is required
to/known to always be a type value. This should be a somewhat exhaustive
set of places, as it covers all instructions given to
GetTypeIdFromTypeInstId().
The things of interest here are:
- Singleton instructions are always of type TypeType, so they are now
TypeInstIds.
- ErrorInst::SingletonInstId gets upcast to be an InstId because it's
sometimes used to define the type of a variable (as in `auto inst_id =
SemIR::ErrorInst::SingletonInstId;` that may hold other InstIds.
- Parse nodes don't really know about TypeInstId, so NodeStack::Push
needs to do some special casing to avoid CHECK failures when given a
TypeInstId but expecting an InstId. We leave a TODO behind here because
the nodes which are being pushed a TypeInstId should probably be taught
to expect that, but such a change is a bit tricky, so too much for this
PR.
TypeInstId is an InstId whose constant value has a type of TypeType.
This includes:
- Type value instructions, the `ClassType` or `IntLiteralType`
instructions.
- Constraint value instructions, which are the `FacetType` and
`TypeType` instructions, each of which also have type TypeType.
TypeInstId encodes in the type system that it is safe to convert the
instruction's value to a TypeId, and CHECKs at construction that this
invariant is maintained.
---------
Co-authored-by: Richard Smith <richard@metafoo.co.uk>
In preparation for shifting from `TypeId`s potentially representing
attached types to always representing unattached types, using
[terminology suggested on
Discord](https://discord.com/channels/655572317891461132/963846118964350976/1359286326779973712).
This change causes us to track slightly more type spelling information
through SemIR.
One change that has significant impact on the SemIR output is that we
now build a `struct_type` instruction in each class representing the
types of the fields, including the spelling used for those types. This
is now no longer always identical to the corresponding canonical
`struct_type` for the object representation, so it's built separately
and owned by the class.
Also remove `TypeBlock` support entirely, as its only use was
representing `TupleType`s, which now use an `InstBlock`.
This gives a slightly simpler representation for `UnboundElementType`s
in eval blocks, and in principle allows us to preserve the spelling of a
field's type into the `UnboundElementType` and thereby into a field
reference, although as of right now this doesn't affect our diagnostic
output in any way.
During error recovery for a field with a non-concrete type, preserve the
type in the `UnboundElementType` regardless. It's not really problematic
to have a non-concrete type there, and this makes it easier to track the
instruction used to specify the type.
This is a step towards switching symbolic types to always be abstract
during type checking.
For each kind of instruction, specify whether its constant evaluation
needs an `InstId` or not. If it does, ensure that all constant
evaluation of that instruction provides one. Otherwise, allow calling
into the evaluator without providing an `InstId`.
This allows us to reliably use the `InstId` in evaluation steps that
either need a location or need to look at the original operands of the
instruction prior to evaluation, and also to support `TryEvalInst` calls
safely for instructions whose evaluation does not need an `InstId`.
Instead of storing a `TypeId` that always refer to a facet type that
always contains exactly a single interface, store the interface
directly.
Also improve stringification of `LookupImplWitness` and witness access
into it, switching to using newly-added functionality for stringifying
specific interfaces.
Each of these types takes another type as an operand. Instead of storing
that other type as a `TypeId`, store it as an `InstId` so that we can
track how it was written, not only its canonical form.
The canonical constant values of these types continue to store the
canonical constant values of their operands, as normal.
---------
Co-authored-by: Dana Jansens <danakj@orodu.net>
* Add `RequireCompleteFacetType` and `ResolveFacetTypeImplWitness` to
`check::Context`. Goal was to move code from `impl.cpp` (mostly) without
functional changes.
* Complete type information is cached with the facet type, and is stored
in a `complete_facet_types()` table.
* Main functional change is to diagnose attempts to use a rewrite
constraint on an associated function. Some existing diagnostics have
been updated.
* Remove `check::Context::RequireDefinedType`:
* For class types, use `RequireCompleteType`
* For facet types, use `RequireCompleteFacetType`
* Introduce a `SemIR::SpecificInterface` to hold an interface and
specific id pair.
* Keep the specific interface ids in the impl object.
* Avoid some extra copies in `Dump` functions.
* Future work missing from this PR:
* Resolving for member access or actions that require impl lookup.
* Resolving rewrites constraints that refer to non-concrete values.
* Any support for adding implied constraints that result from a `where`
clause (though TODOs have been added).
---------
Co-authored-by: Josh L <josh11b@users.noreply.github.com>
Co-authored-by: Richard Smith <richard@metafoo.co.uk>
Co-authored-by: Dana Jansens <danakj@orodu.net>
This creates a new check/type.h for most logic, and also moves some
functions to TypeStore in sem_ir/type.h. My approach for TypeStore is to
focus on moving the read-only functions there.
Dana Jansens
Ivana Ivanovska
Jon Ross-Perkins
Richard Smith
Geoff Romer
