suspect or: role != admin || role != superadmin

[Saied Seghatoleslami]

I have seen a ticket on this topic (or something related to it) on Github but I thought I would ask this community first:

In first instance, I got "suspect or: role != admin || role != superadmin"

In the second instance, it works just fine.  I have verified that role is string type (with %T verb).

since role can be admin, superadmin, or anything else for that matter, why would the first case generate the suspect message, and the second case works fine.

I am running go version go1.13.4 darwin/amd64 on a Mac


First Instance:

const (
 admin      = "admin"
 superadmin = "superadmin"
)

invalidRole := role != admin || role != superadmin

Second instance:

const (
 admin      = "admin"
 superadmin = "superadmin"
)

validRole := role == admin || role == superadmin

[Kurtis Rader]

The inverse of

  validRole := role == admin || role == superadmin

is

  invalidRole := role != admin && role != superadmin

or

  invalidRole := !(role == admin || role == superadmin)

It is not

  invalidRole := role != admin || role != superadmin

Think about it. No matter what value `role` has it has to be unequal to at
least one of those constants and thus that expression is always true.

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Kurtis Rader

Caretaker of the exceptional canines Junior and Hank

[Ian Lance Taylor]

On Mon, May 11, 2020 at 11:53 AM Saied Seghatoleslami
<seghatol...@gmail.com> wrote:
>

> I have seen a ticket on this topic (or something related to it) on Github but I thought I would ask this community first:
>
> In first instance, I got "suspect or: role != admin || role != superadmin"
> In the second instance, it works just fine. I have verified that role is string type (with %T verb).
>
> since role can be admin, superadmin, or anything else for that matter, why would the first case generate the suspect message, and the second case works fine.
>
> I am running go version go1.13.4 darwin/amd64 on a Mac
>
>
> First Instance:
>
> const (
> admin = "admin"
> superadmin = "superadmin"
> )
>
> invalidRole := role != admin || role != superadmin

This sets invalidRole if role != admin or if role != superadmin.
Let's say role is admin. Then role != superadmin is true, so
invalidRole is set to true. Let's say role is superadmin. Then role
!= admin is true, so invalidRole is set to true. Let's say role is
frobozz. Then role != admin is true, so invalidRole is set to true.
In other words, invalidRole is always set to true. This is a "suspect
or".

> Second instance:
>
> const (
> admin = "admin"
> superadmin = "superadmin"
> )
>
> validRole := role == admin || role == superadmin

There is no such confusion here.

Ian

[Saied Seghatoleslami]

Thank you, guys.  I walked myself into a logical trap.  Professor Isapovich is probably turning in his grave and giving me an F in some heavenly grade book.