Comparing Uncomparable Types

Why This Happens

Go's == operator works on comparable types: numbers, strings, booleans, pointers, channels, arrays (of comparable types), and structs (with only comparable fields). Slices, maps, and functions are not comparable. Structs containing these types inherit the restriction.

The Problem

type Config struct {
    Ports []int
}

func main() {
    a := Config{Ports: []int{80, 443}}
    b := Config{Ports: []int{80, 443}}
    fmt.Println(a == b) // invalid operation
}

The Fix

import "reflect"

func main() {
    a := Config{Ports: []int{80, 443}}
    b := Config{Ports: []int{80, 443}}
    fmt.Println(reflect.DeepEqual(a, b)) // true
}

Step-by-Step Fix

1. 1

   Identify the uncomparable field

   Check which struct field contains a slice, map, or function that prevents comparison.

2. 2

   Use reflect.DeepEqual

   For quick comparison, use reflect.DeepEqual(a, b). Note it is slower than manual comparison.

3. 3

   Write custom comparison

   For performance-critical code, write a custom Equal method that compares fields individually.