Missing return statement in conditional for loop

In PHP, the for loop is a common iteration structure used to repeatedly execute a piece of code. However, sometimes we may forget to add a return statement in a conditional for loop, which will cause the program to fail to return results normally. In this case, PHP editor Yuzai recommends checking the code in time to ensure that appropriate return statements are added to the loop to avoid unexpected errors. This can ensure the reliability and correctness of the code and improve the efficiency and maintainability of the program.

Question content

I noticed that when I write the following code, the compiler generates missing return statements error:

// Similar loops make sense in retry patterns
// but this is just a simple example
func TestMethod() int {
    for i := 0; i < 10; i++ {
        return 0
    }
}

This is when the following compiles without any errors:

func TestMethod() int {
    for {
        return 0
    }
}

The first code is logically and technically fine because it is impossible for the method to fail to return. Is there any reason why the compiler shows this error? Or is it some kind of missing logic or bug?

Workaround

Expanding on @Cerise Limón's comment into an answer, the assertion "the first code... is technically fine" is false.

The Go language specification says this:

andand this:

(emphasis added by me)

Inspecting the code in the first function, we can see that these conditions of the specification are not met:

func TestMethod() int {
    for i:= 0; i < 10; i++ {
        return 0
    }
}

The function has a result parameter (int return value), so it must end with a terminating statement, but the final statement of the function is a for statement with a condition, that is, is not a "termination statement" as defined by the specification.

This may seem strange, but it's actually technically correct.

Reward Material

So why is there no problem with the second function?

func TestMethod() int {
    for {
        return 0
    }
}

In this example, the final statement in the function is for, where is unconditional and , does not reference the break statement of the for loop, which satisfies the language specification definition of the termination statement.

There is logic in the work.

If an unconditional for statement contains break, the loop may terminate, so the function requires a return statement.

If the unconditional for statement does not contain a break (and there is no return statement), the loop will not terminate ( At least not as a result of the normal execution path) requiring a function return value).

It's also worth noting that there is no control flow analysis to determine whether any break statements are reachable; they just need to exist . For example, the following will trigger a "missing return" compilation error even though break is clearly inaccessible:

func foo() int {
    for {
        if false {
            break
        }
        return 0
    }
    // <-- error: missing return
}

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