[SR-11355] String.range(of...) matches an extra NUL (and returns range outside string boundaries)

[swift-ci]

Previous ID	SR-11355
Radar	None
Original Reporter	yonilevy (JIRA User)
Type	Bug

Environment

• Swift 5

• Xcode 10.3

• MacOS 10.14.6

Additional Detail from JIRA

Votes	1
Component/s	Standard Library
Labels	Bug
Assignee	None
Priority	Medium

md5: 5026fff9c23d99a0d147ad5d53b56b68

Issue Description:

This is pretty self explanatory:

let str = "bar"
if str.range(of: "r\u{0}")!.upperBound > str.endIndex {
    print("Weird!")
}

I'd expect:

1. the `str.range()` to return `nil`
2. `str.range()` to never return a range outside `str` boundaries

[belkadan]

cc @milseman

[YOCKOW]

Interestingly, the result seems to depend on the environment.
Given the modified code:

// SR-11355.swift
import Foundation

let str = "bar"
let range = str.range(of: "r\u{0}")

if range == nil {
  print("Not Found.")
} else {
  if range!.upperBound > str.endIndex {
    print("Weird!")
  } else {
    print("What is found?")
  }
}

You can get

• "Weird!" with playground on macOS.

• "Not Found." with REPL on macOS.

• "Not Found." with `swift SR-11355.swift` on macOS.

• "Not Found." with `swiftc SR-11355.swift && ./SR-11355` on macOS.

• "Weird!" with any tools on Linux.