Earlier quoted context omitted.
a, err := f() if err != nil { return } a, err = f() This will compile.
I'm not at all defending the practice. I agree it's very easy to navigate around this. My answer is just the canonical one I've seen over and over again in books about Go.
First, it requires having a variable in the first place, if you call a function for its side-effect and don't remember that it returns an error, Go won't tell you.
Second, Go only errors on dead variables, not dead stores, since conventionally the error variable is "err" you can easily forget to check one of them, and Go won't say anything because the err variable was read in one of the other checks.
It's even worse if you're one of the weirdoes which uses named return variables, because named return variables are always used:
func foo() (v int, err error) {
a, err := bar()
b, err := baz()
v = a + b
return
}
func foo() (v int, err error) {
a, err := bar()
b, err := baz()
return a + b, nil
}