Always ignore _ fields

[dsnet]

The _ field in Go is special in that it cannot be read from or written to.
Thus, skip it by default. It is pointless to require the user to use
cmpopts.IgnoreUnexported just for the _ field.

[cybrcodr]

I wasn't aware that it is possible to have blank identifier as a field name. I wonder why the language provides such construct, seems not useful.

[dsnet]

It's useful when dealing with unsafe and you want to explicitly control the memory layout of the struct.

For example:

type Foo struct {
     _ uint64
     v uint64 // lives at offset +8B
}

Or to nest a type to explicitly make the type incomparable:

type Incomparable struct {
    _ [0]func()
   ... // other fields
}

[cybrcodr]

Neat.

I didn't know that _ field will take up space of given type (unless 0).

Good to know of another way to make a struct incomparable apart from embedding a func type.