[SR-3566] Data incorrectly truncates when appending contents of abstract sequences

[phausler]

Previous ID	SR-3566
Radar	rdar://problem/29903374
Original Reporter	@phausler
Type	Bug

Additional Detail from JIRA

Votes	2
Component/s	Foundation
Labels	Bug, Linux, SDKOverlay
Assignee	None
Priority	Medium

md5: 9a2094dad4aa3a32381cf3350604558d

Issue Description:

var d = Data()
d.append(contentsOf: elements)

assert(d[0] == 0x01)
assert(d[1] == 0x01) // fails here because the internal append method incorrectly truncates
assert(d[2] == 0x01)

[Dante-Broggi]

I think this has been fixed. If so, it should be closed.