Can Go\'s Pointer Receiver Methods Be Called on Non-Pointer Variables?

Calling Methods for Pointer Type *T with Receiver T

The Go programming language specification states that the method set of any type T consists of all methods with receiver type T. However, the method set of the corresponding pointer type T is the set of all methods with receiver T or T (including the method set of T).

This means that we can call methods with a receiver of type *T on a variable of type T, as the compiler implicitly dereferences the variable to call the method.

To verify this concept, consider the following code:

package main

import (
    "fmt"
    "reflect"
)

type User struct{}

func (self *User) SayWat() {
    fmt.Println(self)
    fmt.Println(reflect.TypeOf(self))
    fmt.Println("WAT\n")
}

func main() {
    var user User = User{}

    fmt.Println(reflect.TypeOf(user), "\n")

    user.SayWat()
}

When we run this code, we observe that the SayWat() method can be called on the user variable, even though the method is defined with a pointer receiver. This is because the compiler automatically dereferences the variable for us.

However, it is important to note that we cannot call methods of *T on T directly. For example, the following code will fail with a compiler error:

func main() {
    var user User = User{}

    (&user).SayWat()
}

In this case, the compiler cannot implicitly dereference the variable because the SayWat() method is defined with a pointer receiver. To call the method, we must explicitly dereference the variable with the & operator.

Therefore, although we can call methods with a receiver of type T on a variable of type T, we cannot call methods of T on T directly.

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