Fwiw, such a construct is possible today without the bool or resorting to assembly:

	for _, v := range haystack {
		if v == needle {
			goto next
		}
	}
	// Operation when the set lacks the item

next:
	// either way, we continue here

This sort of Pythonic for/else syntax would merely by sugar.

Why not write a contains function, or wait for generics and write a generic contains function?

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Compare #24282

I often find I need the following else for form instead:

if len(values) == 0 {
   ... // print some info
} else for _, v := range values {
   ...
}

Surely, currently we can write it as

if len(values) == 0 {
   ... // print some info
}

for _, v := range values {
   ...
}

But I think the former is more logical (and could be a bit more efficient).

If if-block can follow else, why can't others?

[edit]: a better example for the occasion:

if vs := f(); len(vs) == 0 {
} else {
  for _, v := range vs {
  }
}

// vs.

if vs := f(); len(vs) == 0 {
} else for _, v := range vs {
}

I'm personally just not a fan of for else in python. It's very useful, but it just doesn't read well in my opinion and is often a bit confusing.

Timed out in state WaitingForInfo. Closing.

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While that works in that specific example, the general case is a bit more complicated: https://play.golang.org/p/wMaykOGCfMC

The code requires 2 gotos which cross over each other, which can quickly lead to spaghetti code if there is more code in each section other than a simple fmt.Println. If code blocks and indents were used, it would look a lot better (which is the case for for-else). I however think that for-else doesn't look very good and isn't super intuitive. Maybe there is another word which could be used (fallthrough?), as the concept of for-else is very nice, however it just doesn't seem to lead to readable code. Maybe an entirely new concept could be thought up. Or we could just use a found variable for more complicated cases.

Maybe there is another word which could be used (fallthrough?)

notwithstanding

Looking back at this thread, I'm not sure if anyone's pointed out the precedent of text/template's {{ range }} ... {{ else }} ... {{ end }} ; so there it is fwiw