How to convert string value to custom type in function

Question

I've written a function for role checking:

...
role = "roles/cloudkms.publicKeyViewer"
func checkRole(key, serviceAccount, role string) bool {
...
return policy.HasRole(serviceAccount, role)
}

Then I'm getting the error "cannot use role (type string) as type "cloud.google.com/go/iam".RoleName in argument to policy.HasRole.

What's the right way to convert the role value to custom type?

The library:

// A RoleName is a name representing a collection of permissions.
type RoleName string

// Common role names.
const (
    Owner  RoleName = "roles/owner"
    Editor RoleName = "roles/editor"
    Viewer RoleName = "roles/viewer"
)

const (
    // AllUsers is a special member that denotes all users, even unauthenticated ones.
    AllUsers = "allUsers"

    // AllAuthenticatedUsers is a special member that denotes all authenticated users.
    AllAuthenticatedUsers = "allAuthenticatedUsers"
)


// HasRole reports whether member has role r.
func (p *Policy) HasRole(member string, r RoleName) bool {
    return memberIndex(member, p.binding(r)) >= 0
}

Answer 1

You can use type conversion as the following:

return policy.HasRole(serviceAccount, iam.RoleName(role))

Or simpler by declaring role as iam.RoleName

func checkRole(key, serviceAccount, role iam.RoleName) bool {
...
   return policy.HasRole(serviceAccount, role)
}