Switch on type vs type assertion

switch_test.go

package typeassertion

import (
	"errors"
	"testing"
)

// go test -bench=. -benchtime 20s
//
// Benchmark_SwitchType		100000000	       483 ns/op
// Benchmark_TypeAssertion	100000000	       442 ns/op

var issues = []interface{}{
	errors.New("an error"),
	0,
	errors.New("an error 0"),
	1,
	errors.New("an error 1"),
	2,
	errors.New("an error 2"),
	3,
	errors.New("an error 3"),
	4,
	-1,
	errors.New("an error 4"),
	5,
	errors.New("an error 5"),
	6,
	errors.New("an error 6"),
	7,
	errors.New("an error 7"),
	8,
	errors.New("an error 8"),
	9,
	errors.New("an error 9"),
}

func Benchmark_SwitchType(b *testing.B) {
	var lastError int

	for i := 0; i < b.N; i++ {
		for j, issue := range issues {
			switch issue.(type) {
			case error:
				lastError = j
			default:
			}
		}
	}
	lastError++
}

func Benchmark_TypeAssertion(b *testing.B) {
	var lastError int

	for i := 0; i < b.N; i++ {
		for j, issue := range issues {
			if _, ok := issue.(error); ok {
				lastError = j
			}
		}
	}
	lastError++
}