carbon-lang/toolchain/check/cpp_overload_resolution.h

// 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_OVERLOAD_RESOLUTION_H_
#define CARBON_TOOLCHAIN_CHECK_CPP_OVERLOAD_RESOLUTION_H_

#include "toolchain/check/context.h"
#include "toolchain/sem_ir/ids.h"

namespace Carbon::Check {

// Performs overloading resolution for a call to an overloaded C++ set. A set
// with a single non-templated function goes through the same rules for
// overloading resolution. Uses Clang to find the best viable function for the
// call. Returns the resolved function, or `nullopt` if overload resolution
// failed.
//
// Note on non-overloaded functions: In C++, a single non-templated function is
// also treated as an overloaded set and goes through the overload resolution to
// ensure that the function is viable for the call. This is to make sure that
// calls that have no viable implicit conversion sequence are rejected even when
// an implicit conversion is possible. Keeping the same behavior here for
// consistency and supporting migrations so that the migrated callers from C++
// remain valid.
auto PerformCppOverloadResolution(Context& context, SemIR::LocId loc_id,
                                  SemIR::CppOverloadSetId overload_set_id,
                                  llvm::ArrayRef<SemIR::InstId> arg_ids)
    -> std::optional<SemIR::InstId>;

}  // namespace Carbon::Check

#endif  // CARBON_TOOLCHAIN_CHECK_CPP_OVERLOAD_RESOLUTION_H_