Incorrect "missing return" error for an edge case

[burak serdar]

This question came up on Stack Overflow today:

The following code is giving a "missing return" error where it shouldn't:

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

Looks like an overlooked case in control flow analysis.

[Axel Wagner]

The "missing return" error is defined in the spec, by requiring a function to end in a terminating statement:

https://go.dev/ref/spec#Terminating_statements

The list is necessarily not complete. So it is necessarily more advisory than anything else. What things to put in is mainly limited by how much complexity it would be to specify it and how important we deem it. Specifying this case seems pretty hard to specify (note that `i` could be modified in the loop body, so this always terminating requires some pretty complex statements about what is or is not in the loop body - in particular, if you want to do it on a purely syntactical level).

It also also can be replaced by `func TestMethod() int { return 0 }`, which is strictly better, more readable code, so I wouldn't even necessarily agree that it's a false-positive error message: You *should* fix that.

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[Dan Kortschak]

The case here is covered by point 5 of the terminating statements
definition. It is a for loop with a loop condition, so it is not a
terminating statement.

[burak serdar]

Thank you both. I should've looked at the spec first.

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