Comparison of range objects

[laurentlb]

According to the specification:

Range values are comparable: two range values compare equal if they denote the same sequence of integers, even if they were created using different parameters.

The interpreter contains a bug: range(0, 5, 10) == range(0, 5, 11) returns False.
Bazel, Python2, and Python3 return True (Bazel's implementation is not necessarily the best, as it iterates over the values).

[alandonovan]

Well spotted! The fix is that we should only compare the step if len > 1.

func rangeEqual(x, y rangeValue) bool {
	// Two ranges compare equal if they denote the same sequence.
	if x.len != y.len {
		return false // sequences differ in length
	}
	if x.len == 0 {
		return true // both sequences are empty
	}
	if x.start != y.start {
		return false // first element differs
	}
	return x.len == 1 || x.step == y.step
}

testdata/builtins.star

+assert.eq(range(0, 5, 10), range(0, 5, 11))

I won't fix it just yet because I'm hoping to cut over to the new repo any day now.