Code 3

// This code outputs:
// 0 0 false false
// A bug?

// Note: now both calls to hasBlock at else branch return false, even though such result is not possible due to the if expression.
package main

import (
	"fmt"
)

func hasBlock(x, y int) bool {
	if x < 0 || x >= 1 {
		return false
	}
	return true
}

func main() {
	ok := false

	for x := 0; x < 1; x++ {
		for y := 0; y < 1; y++ {
			if !hasBlock(x - 1, y) {
				ok = true
			} else {
				fmt.Println(x, y, hasBlock(-1, 0), hasBlock(x - 1, y))
			}
		}
	}

	if !ok {
		fmt.Println("A bug?")
	}
}