Open
Description
Comparing two Value type does not do what the user expects. The type is documented as such:
Using == on two Values does not compare the underlying values they represent, but rather the contents of the Value structs. To compare two Values, compare the results of the Interface method.
However, it is still common to see users accidentally make this mistake. What's worse is that it "seems to work", giving a false sense of security.
s1, s2 := "hello", "goodbye"
v1a := reflect.ValueOf(&s1)
v1b := reflect.ValueOf(&s1)
v2 := reflect.ValueOf(&s2)
fmt.Println(v1a == v1a) // Prints true
fmt.Println(v1a == v1b) // Prints true
fmt.Println(v1a == v2) // Prints falseThis is because the Value struct contains a flag field whose value may be different for each Value and is entirely an implementation detail of the reflect package.
Perhaps we should add a uncomparable type to prevent this misuse:
type Value struct {
_ [0]func() // Prevents Value from being comparable and occupies 0 bytes
typ *rtype
ptr unsafe.Pointer
flag
}\cc @ianlancetaylor