Repository: carbon-language/carbon-lang
File: toolchain/check/import_ref.cpp (C++)

Code before:
        {.ir_id = AddImportIR(context, {.decl_id = SemIR::InstId::None,
                                        .is_export = false,
                                        .sem_ir = cursor_ir}),
         .inst_id = import_ir_inst.inst_id});
  }
}

// NOLINTNEXTLINE(misc-no-recursion)
auto LoadImportRef(Context& context, SemIR::InstId inst_id) -> void {
  auto inst = context.insts().TryGetAs<SemIR::ImportRefUnloaded>(inst_id);
  if (!inst) {
    return;
  }

  auto [indirect_insts, load_type_id] =
      GetInstForLoad(context, inst->import_ir_inst_id);

  // The last indirect instruction is the one to resolve. Pop it here because
  // Resolve will assign the constant.
  auto load_ir_inst = indirect_insts.pop_back_val();
  ImportRefResolver resolver(&context, load_ir_inst.ir_id);
  auto type_id = resolver.ResolveType(load_type_id);
  auto constant_id = resolver.Resolve(load_ir_inst.inst_id);

  // Replace the ImportRefUnloaded instruction with ImportRefLoaded. This
  // doesn't use ReplaceImportedInstAndSetConstantValue because it would trigger
  // TryEvalInst, which we want to avoid with ImportRefs.
  context.sem_ir().insts().Set(
      inst_id,
      SemIR::ImportRefLoaded{.type_id = type_id,
                             .import_ir_inst_id = inst->import_ir_inst_id,
                             .entity_name_id = inst->entity_name_id});

  // Store the constant for both the ImportRefLoaded and indirect instructions.
  context.constant_values().Set(inst_id, constant_id);
  for (const auto& import_ir_inst : indirect_insts) {
    context.import_ir_constant_values()[import_ir_inst.ir_id.index].Set(
        import_ir_inst.inst_id, constant_id);
  }
}

auto ImportImplsFromApiFile(Context& context) -> void {
  SemIR::ImportIRId import_ir_id = SemIR::ImportIRId::ApiForImpl;
  auto& import_ir = context.import_irs().Get(import_ir_id);
  if (!import_ir.sem_ir) {
    return;
  }

  for (auto [impl_id, _] : import_ir.sem_ir->impls().enumerate()) {
    // Resolve the imported impl to a local impl ID.
    ImportImpl(context, import_ir_id, impl_id);

Review comment (suggestion):
With the changes, it looks like you could call `ReplaceImportedInstAndSetConstantValue` with `ConstantId::None` (take this with a grain of salt)

Code after:
auto LoadImportRef(Context& context, SemIR::InstId inst_id) -> void {
  auto inst = context.insts().TryGetAs<SemIR::ImportRefUnloaded>(inst_id);
  if (!inst) {
    return;
  }

  auto [indirect_insts, load_type_id] =
      GetInstForLoad(context, inst->import_ir_inst_id);

  // The last indirect instruction is the one to resolve. Pop it here because
  // Resolve will assign the constant.
  auto load_ir_inst = indirect_insts.pop_back_val();
  ImportRefResolver resolver(&context, load_ir_inst.ir_id);
  auto type_id = resolver.ResolveType(load_type_id);
  auto constant_id = resolver.Resolve(load_ir_inst.inst_id);

  // Replace the ImportRefUnloaded instruction with ImportRefLoaded. This
  // doesn't use ReplacePlaceholderImportedInst because it would trigger
  // TryEvalInst, which we want to avoid with ImportRefs.
  context.sem_ir().insts().Set(
      inst_id,
      SemIR::ImportRefLoaded{.type_id = type_id,
                             .import_ir_inst_id = inst->import_ir_inst_id,
                             .entity_name_id = inst->entity_name_id});

  // Store the constant for both the ImportRefLoaded and indirect instructions.
  context.constant_values().Set(inst_id, constant_id);
  for (const auto& import_ir_inst : indirect_insts) {
    context.import_ir_constant_values()[import_ir_inst.ir_id.index].Set(
        import_ir_inst.inst_id, constant_id);
  }
}

auto ImportImplsFromApiFile(Context& context) -> void {
  SemIR::ImportIRId import_ir_id = SemIR::ImportIRId::ApiForImpl;
  auto& import_ir = context.import_irs().Get(import_ir_id);
  if (!import_ir.sem_ir) {
    return;
  }

  for (auto [impl_id, _] : import_ir.sem_ir->impls().enumerate()) {
    // Resolve the imported impl to a local impl ID.
    ImportImpl(context, import_ir_id, impl_id);
  }
}

auto ImportImpl(Context& context, SemIR::ImportIRId import_ir_id,
                SemIR::ImplId impl_id) -> void {
  ImportRefResolver resolver(&context, import_ir_id);
  resolver.Resolve(context.import_irs()
                       .Get(import_ir_id)