如何使函数支持一两个返回值

Question

in go tutorial following code is often seen:

a := foo()
b, c := foo()

or actually what I see is:

m["Answer"] = 48
a := m["Answer"]
v, ok := m["Answer"]

how many foo() is defined?

Is it two, one with one return type, another with two return type?

Or just one foo() with two return type defined, and somehow magically when only need one return value (a := foo()), another return value is omitted?

I tried

package main

func main() {
    a := foo()
    a = 1
}

func foo() (x, y int) {
    x = 1
    y = 2
    return
}

func foo() (y int) {
    y = 2
    return
}

But I got error message foo redeclared in this block

Answer 1

While some built in operations support both single and multiple return value modes (like reading from a map, type assertions, or using the range keyword in loops), this feature is not available to user defined functions.

If you want two versions of a function with different return values, you will need to give them different names.