How Do `defer` Statements and Named Return Values Interact in Go?

Understanding Defer and Named Return Values in Go

In Go, the defer statement allows functions to execute code after the surrounding function returns. This behavior can be used to modify the named return values of the surrounding function.

Consider the following example:

func c() (i int) {
    defer func() { i++ }()
    return 1
}

This function returns 2, even though the return 1 statement is used. This is because the defer statement pushes a function call onto a stack, which is executed immediately before the surrounding function returns. Therefore, the i statement is executed after the return 1 statement, incrementing the value of i to 2.

Understanding Naked Returns

It's important to clarify that a "naked return" in Go refers to a return statement without any arguments. In such cases, the named return values are returned without being explicitly assigned.

func a() (i int) {
    i = 2
    return
}

This function returns 2, because the naked return statement returns the named return value i, which has been previously assigned to 2.

Combining Defer and Non-Naked Returns

In the example of function c, the defer statement modifies the named return value i after the return 1 statement is executed. This is effectively equivalent to the following code:

func c() (i int) {
    i = 1
    defer func() { i++ }()
}

In this case, the return statement still returns 1, but the defer statement increments the value of i before the function returns.

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