---

yaml
---
r: 349536
b: refs/heads/master-next
c: 1329d52
h: refs/heads/master

Author: swift-ci

[refs]

@@ -1,6 +1,6 @@
 ---
 refs/heads/master: 3574c513bbc5578dd9346b4ea9ab5995c5927bb5
-refs/heads/master-next: 0fd3e1dfb7f3f131d5d578f6b1e2322c7d4fd768
+refs/heads/master-next: 1329d52a2117d2358bbaac27201cbc0d3ace4c3b
 refs/tags/osx-passed: b6b74147ef8a386f532cf9357a1bde006e552c54
 refs/tags/swift-2.2-SNAPSHOT-2015-12-01-a: 6bb18e013c2284f2b45f5f84f2df2887dc0f7dea
 refs/tags/swift-2.2-SNAPSHOT-2015-12-01-b: 66d897bfcf64a82cb9a87f5e663d889189d06d07

branches/master-next/validation-test/stdlib/String.swift

@@ -220,6 +220,13 @@ StringTests.test("Index/Hashable") {
   expectTrue(t.contains(s.startIndex))
 }
 
+var Swift_5_1_Available: Bool {
+  if #available(macOS 10.15, iOS 13, tvOS 13, watchOS 6, *) {
+    return true
+  }
+  return false
+}
+
 StringTests.test("ForeignIndexes/Valid") {
   // It is actually unclear what the correct behavior is.  This test is just a
   // change detector.
@@ -238,6 +245,10 @@ StringTests.test("ForeignIndexes/Valid") {
     let acceptor = "\u{1f601}\u{1f602}\u{1f603}"
     expectEqual("\u{1f601}", acceptor[donor.startIndex])
 
+    // Scalar alignment fixes and checks were added in 5.1, so we don't get the
+    // expected behavior on prior runtimes.
+    guard Swift_5_1_Available else { return }
+
     // Donor's second index is scalar-aligned in donor, but not acceptor. This
     // will trigger a stdlib assertion.
     let donorSecondIndex = donor.index(after: donor.startIndex)
@@ -257,6 +268,10 @@ StringTests.test("ForeignIndexes/UnexpectedCrash") {
   // Adjust donor.startIndex to ensure it caches a stride
   let start = donor.index(before: donor.index(after: donor.startIndex))
 
+  // Grapheme stride cache under noop scalar alignment was fixed in 5.1, so we
+  // get a different answer prior.
+  guard Swift_5_1_Available else { return }
+
   // `start` has a cached stride greater than 1, so subscript will trigger an
   // assertion when it makes a multi-grapheme-cluster Character.
   if _isStdlibInternalChecksEnabled() {