Is this supposed to be an error?

[skillian (Sean Killian)]

I’m writing some Go for the first time outside of an IDE and am not getting immediate feedback for my syntax and semantic errors, so after finally attempting a build and going through tens of errors, I hit one that though I understand what it’s telling me, I don’t understand why it’s an error. I put a reproducible scenario together in the playground here.

For those who don’t click, here’s my test function:

func test() error {
	return nil
	fmt.Println("useless")
}

This produces a compile-time error: “missing return at end of function.” Like I said, I understand what this is telling me, but why is this an error? If I instead change the function to:

func test() {
	return
	fmt.Println("useless")
}

There’s no error.

I’ve been skimming through the language specification here but I still can’t yet tell why not having a return statement at the end is an error if the code is unreachable; it doesn’t surprise me considering how strict Go is about unused variables, imports, etc., but is that specified anywhere?

[j-forster (Johann Forster)]

The compiler does not ignore the unreachable code.

func test() error {
	// return nil
	fmt.Println("useless")
}

func test() {
	// return
	fmt.Println("useless")
}

The first function can not be compiled as the function is expected to return an error.
For functions without return values, the return statement is implicit generated if not given.

[skillian (Sean Killian)]

Thanks, @j-forster, after that bit of guidance, I was able to find the relevant part of the spec: https://golang.org/ref/spec#Terminating_statements