NSURL(string:relativeTo:) does not properly construct URLs

Number:rdar://31615751 Date Originated:4/13/17
Status:Open Resolved:
Product:Developer Tools Product Version:Xcode 8.2.1
Classification:Serious Bug Reproducible:Always
The last path component of the relative URL is always stripped when using this initializer.

Steps to Reproduce:
1. Launch `swift`
2. > import Foundation
3. > NSURL(string: "foo", relativeTo:URL(string:"http://base.com/foo/bar")!)!.absoluteString

Expected Results:
$R1: String? = "http://base.com/foo/bar/foo"

Actual Results:
$R1: String? = "http://base.com/foo/foo"

Xcode Version 8.2.1 (8C1002)
MacOS 10.12.4 (16E195)

This affects the Objective-C API as well, since it is bridged.




I'd assume this is expected behavior as if I was at http://base.com/foo/bar and navigated to "foo". My resulting destination would be http://base.com/foo/foo

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