As part of this, move functions that seem reasonable to make out-of-line
to a separate `_impl.h` header file that is only included where the
explicit instantiation _definition_ is provided.
By using explicit instantiation we can make these templates behave more
like non-template classes in terms of supporting out-of-line definitions
that don't need to be compiled by every translation unit. The set of
eventual instantiations here is fundamentally known, and there tend to
be headers that define a canonical "leaf" type where it makes sense to
trigger the explicit instantiation.
Where we already had a `.cpp` file to put the explicit instantiation
definition, use it. But in some places we didn't have such a `.cpp` file
so this PR adds those.
This also requires that we have precise constraints on APIs that _can't_
be instantiated for specific argument types, as now we don't do this
lazily.
Combined, this appears to reduce the sum of object file sizes in the
`check` directory by almost 40% (122mb -> 74mb) in my measurement.
My actual goal was to improve compile times, but so far I don't have a
great methodology for measuring these... But the object file size
reduction seems to confirm this is a net win and likely represents a
non-trivial improvement in compile time.
Assisted-by: Antigravity with Gemini
The IdTag knows the type of the Id its tagging and the type of the Id
being used as the tag. This prevents mixing up tagged and untagged ids,
and avoids having to work with untyped integers.
Adds an Untagged marker struct that's used as the tag type in IdTag when
no tag is desired.
The complexity of ConstantIds and TypeIds became a bit visible: TypeIds
are concrete ConstantIds. And ConstantIds have two different tagging
schemes, one for concrete and one for symbolic ids. And ConstantIds are
actually re-cast InstIds with the same index. The LoweredTypeStore needs
to work with tagged TypeIds, but the tags actually come from an InstId
store in ConstantValueStore. Now this is expressed in the type system by
getting the tags for TypeIds from the ConstantValueStore.
ValueStores without an TagId type parameter are now visibly untagged.
IdTag is now only default constructible when it does not have a tag,
which means ValueStore is only default constructible when the TagId is
untagged. This forces tagged value stores to be constructed correctly
with a tag at compile time, and untagged ones to be constructed without.
FixedSizeValueStore has overloads for dealing with tagged and untagged
Ids, since it can't default-construct ValueStore for tagged ids, and no
longer requires passing in default-constructed tags when there is no tag
in the ids.
This allows to find the spaceship `operator<=>` when a comparison
operator is not available, and `operator==` when `operator!=` is not
available.
Support added to both lookup and overload resolution, by adding
`OperatorRewriteInfo` and propagating it in `CppOverloadSet`.
In case overload resolution chooses to use an operator which requires
rewriting, we emit a `TODO` since rewriting is not yet supported.
Part of #6170.
This turns out to be quite important, as several important standard
library types (such as `std::string`) have mixed-access overload sets
for their constructors as an implementation detail. The overall approach
here is:
- Use the most permissive access to determine the access of the overload
set itself. This affects whether name lookup finds the member name at
all.
- After overload resolution, re-check the access of the selected member,
if it's protected or private.
---------
Co-authored-by: Dana Jansens <danakj@orodu.net>
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
Chandler Carruth
Dana Jansens
Boaz Brickner
Richard SmithandDana Jansens
Ivana Ivanovska