Files
carbon-lang/toolchain/check/cpp/operators.h
T
Boaz Brickner ef488f00fa Overload resolution for C++ operators (#6092)
Multiple overloads for the same operator are now resolved using overload
resolution.
This change doesn't try to solve all issues with operator lookup.

Moved the operator lookup logic from `import` to `operators` and changed
it to take the args into account.
Use `Sema::LookupOverloadedBinOp()` (with ADL) when looking up operator
functions to create an overload set.

Verified all demos in #6017, #6020 and #6024 still work.

C++ Interop Demo:

```c++
// my_number.h

class MyNumber {
 public:
  explicit MyNumber(int value) : value_(value) {}
  auto value() const -> int { return value_; }

 private:
  int value_;
};

class NotMyNumber {};

auto operator+(MyNumber lhs, MyNumber rhs) -> MyNumber;
auto operator+(NotMyNumber lhs, NotMyNumber rhs) -> NotMyNumber;
```

```c++
// my_number.cpp

#include "my_number.h"

auto operator+(MyNumber lhs, MyNumber rhs) -> MyNumber {
  return MyNumber(lhs.value() + rhs.value());
}

auto operator+(NotMyNumber lhs, NotMyNumber /*rhs*/) -> NotMyNumber {
  return lhs;
}
```

```carbon
// main.carbon

library "Main";

import Core library "io";
import Cpp library "my_number.h";

fn Run() -> i32 {
  // Arithmetic
  var num1: Cpp.MyNumber = Cpp.MyNumber.MyNumber(14);
  var num2: Cpp.MyNumber = Cpp.MyNumber.MyNumber(5);
  Core.Print(num1.value());
  Core.Print(num2.value());
  Core.Print((num1 + num2).value());

  return 0;
}
```

**After this change:**

```shell
$ clang -c my_number.cpp
$ bazel-bin/toolchain/carbon compile main.carbon
$ bazel-bin/toolchain/carbon link my_number.o main.o --output=demo
$ ./demo
14
5
19
```

**Before this change**

```shell
$ bazel-bin/toolchain/carbon compile main.carbon
main.carbon:14:15: error: semantics TODO: `Unsupported: Lookup succeeded but couldn't find a single result; LookupResultKind: 3`
  Core.Print((num1 + num2).value());
              ^~~~~~~~~~~
main.carbon:14:15: note: in `Cpp` operator `AddWith` lookup
  Core.Print((num1 + num2).value());
              ^~~~~~~~~~~
```

Part of https://github.com/carbon-language/carbon-lang/issues/5995.
2025-09-19 16:42:46 +00:00

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828 B
C++

// Part of the Carbon Language project, under the Apache License v2.0 with LLVM
// Exceptions. See /LICENSE for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
#ifndef CARBON_TOOLCHAIN_CHECK_CPP_OPERATORS_H_
#define CARBON_TOOLCHAIN_CHECK_CPP_OPERATORS_H_
#include "toolchain/check/context.h"
#include "toolchain/check/operator.h"
#include "toolchain/sem_ir/ids.h"
namespace Carbon::Check {
// Looks up the given operator in the Clang AST generated when importing C++
// code using argument dependent lookup (ADL) and return overload set
// instruction.
auto LookupCppOperator(Context& context, SemIR::LocId loc_id, Operator op,
llvm::ArrayRef<SemIR::InstId> arg_ids) -> SemIR::InstId;
} // namespace Carbon::Check
#endif // CARBON_TOOLCHAIN_CHECK_CPP_OPERATORS_H_