It's more complicated. There is no single correct way to check for errors. Some standard library functions can return data and an error: https://pkg.go.dev/io#Reader
This is true, but it feels like a mistake. It's too late to change now, of course, but I feel like (0, nil) and (!=0, !=nil) should both have been forbidden. The former is "discouraged" now, at least. It does simplify implementations to allow these cases, but it complicates consumers of the interface, and there are far more of the latter than the former.
Comments
It's more complicated. There is no single correct way to check for errors. Some standard library functions can return data and an error: https://pkg.go.dev/io#Reader
This is true, but it feels like a mistake. It's too late to change now, of course, but I feel like (0, nil) and (!=0, !=nil) should both have been forbidden. The former is "discouraged" now, at least. It does simplify implementations to allow these cases, but it complicates consumers of the interface, and there are far more of the latter than the former.