Golang: Scope of multi return values from function

Question

When a function returns more than one variable in Golang, what's the scope of the variables? In the code attached, I can't figure out the scope of b.

package main

import (
    "fmt"
)

func addMulti(x, y int) (int, int) {
    return (x + y), (x * y)
}

func main() {
    //what is the scope of the b variable here?
    a, b := addMulti(1, 2)

    fmt.Printf("%d %d\n", a, b)

    //what is the scope of the b variable here?
    c, b := addMulti(3, 4)

    fmt.Printf("%d %d\n", c, b)

}   

Answer 1

We're not talking about the scope of the return value of a function but rather the scope of the variable you assign the return value to.

The scope of the variable b in your case is the function body, from the point at which you declare it.

At first you do it at this line:

a, b := addMulti(1, 2)

But then you use another Short Variable declaration at this line:

c, b := addMulti(3, 4)

which - since b is already declared - just assigns a new value to it. b will be in scope until the end of your main() function. Quoting from the Go Language Specification:

Unlike regular variable declarations, a short variable declaration may redeclare variables provided they were originally declared earlier in the same block with the same type, and at least one of the non-blank variables is new. As a consequence, redeclaration can only appear in a multi-variable short declaration. Redeclaration does not introduce a new variable; it just assigns a new value to the original.

Answer 2

It's a normal variable inside a block. From the spec :

The scope of a constant or variable identifier declared inside a function begins at the end of the ConstSpec or VarSpec (ShortVarDecl for short variable declarations) and ends at the end of the innermost containing block.

In the second call, you're just reassigning the value of the same b variable. Its scope is the same.

Answer 3

The scope of b variable is main.main() . In second assignment c, b := addMulti(3, 4) you introduce new variable c, and assign variable b introduced in first assignment. If you change second assignment to be a, b := addMulti(3, 4) same as first it want not to compile.