A idea: Improve the error check and change it to a language keyword

[ssoor]

We propose a new syntax: !error, specifically designed to eliminate if boilerplate statements that are usually associated with error handling in Go.

func open(filename string) (*file,error) {
    return ..., errors.New("file does not exist")
}

f, err := open(filename)
if err != nil {
	return …, err  // zero values for other results, if any
}

can be simplified to

func open(filename string) *file!error {
    return !errors.New("file does not exist")
}

f, ! := os.Open(filename)

Complete example:

func f(v1 int,v2 int) (int,int)!error {
    if v1 < 0 {
        return !errors.New("error...") // Return a error, other results return the default zero value
    }

    return v1+v2, v1-v2
}

func print1(v1 int,v2 int) !error {
    add, sub, ! := f(v1, v2) // If the error is not empty, it will return the error
    fmt.Println(add, sub)
}


func print2(v1 int,v2 int) !error {
    add, sub, !err := f(v1, v2) // If the error is not empty, it will be assigned to err
    fmt.Println(add, sub)

    if err != nil {
         return !err // return the error
    }

    return !nil
}

func main() { // The method is not allowed to return an error, the error must be assigned to the variable
    !err := print1(-1,1)
    fmt.Println(err) 
    // error...

    !err := print2(-1,1)
    fmt.Println(err)
    // 0 0
    // error...

    !err := print1(1,2)
    fmt.Println(err)
    // 3 -1
   //  nil
}

It borrows ideas from:

• Proposal: A built-in Go error check function, "try" #32437

[andig]

Youll need to fill the language change proposal

[mvdan]

Please note that you should fill https://github.com/golang/proposal/blob/master/go2-language-changes.md when proposing a language change.