为什么我的自定义错误类型导致特定模式的错误？ [重复]

I'm struggling with go's receivers and pointers. I found that 4th pattern causes error. Why this pattern causes error and what's the difference? Thanks in advance.

type MyError struct{}

// OK pattern
func (e MyError) Error() string {
    return "something bad happened"
}

func run() error {
    return MyError{}
}

// OK pattern
func (e MyError) Error() string {
    return "something bad happened"
}

func run() error {
    return &MyError{}
}

// OK pattern
func (e *MyError) Error() string {
    return "something bad happened"
}

func run() error {
    return &MyError{}
}

// BAD pattern
func (e *MyError) Error() string {
    return "something bad happened"
}

func run() error {
    return MyError{}
}

</div>

Go will automatically dereference a pointer for you (pattern 2), however it won't automatically reference one for you. See https://golang.org/ref/spec#Method_values for more information.