You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: operator_test.go
    path of file: ./repos/expr/test/operator
    
    the code of the file until where you have to start completion: package operator_test

import (
	"fmt"
	"testing"
	"time"

	"github.com/stretchr/testify/assert"
	"github.com/st
    
func TestOperator_Polymorphic(t *testing.T) {
	env := struct {
		Add func(a, b int) int
		Foo Value
		Bar Value
	}{
		Add: func(a, b int) int {
			return a + b
		},
		Foo: Value{1},
		Bar: Value{2},
	}

	program, err := expr.Compile(
		`1 + 2 + (Foo + Bar)`,
		expr.Env(env),
		expr.Operator("+", "Add", "AddValues"),
		expr.Function("AddValues", func(args ...interface{}) (interface{}, error) {
			return args[0].(Value).Int + args[1].(Value).Int, nil
		},
			new(func(_ Value, __ Value) int),
		),
	)
	require.NoError(t, err)

	output, err := expr.Run(program, env)
	require.NoError(t, err)
	require.Equal(t, 6, output)
}