[stdlib] Add tests for index hashability

Author: natecook1000

validation-test/stdlib/Dictionary.swift

@@ -77,6 +77,13 @@ DictionaryTestSuite.test("sizeof") {
 #endif
 }
 
+DictionaryTestSuite.test("Index.Hashable") {
+  let d = [1: "meow", 2: "meow", 3: "meow"]
+  let e = Dictionary(uniqueKeysWithValues: zip(d.indices, d))
+  expectEqual(d.count, e.count)
+  expectNotNil(e[d.startIndex])
+}
+
 DictionaryTestSuite.test("valueDestruction") {
   var d1 = Dictionary<Int, TestValueTy>()
   for i in 100...110 {

validation-test/stdlib/Set.swift

@@ -331,6 +331,13 @@ SetTestSuite.test("sizeof") {
 #endif
 }
 
+SetTestSuite.test("Index.Hashable") {
+  let s: Set = [1, 2, 3, 4, 5]
+  let t = Set(s.indices)
+  expectEqual(s.count, t.count)
+  expectTrue(t.contains(s.startIndex))
+}
+
 SetTestSuite.test("COW.Smoke") {
   var s1 = Set<TestKeyTy>(minimumCapacity: 10)
   for i in [1010, 2020, 3030]{ s1.insert(TestKeyTy(i)) }

validation-test/stdlib/String.swift

@@ -148,7 +148,7 @@ StringTests.test("unicodeScalars") {
   checkUnicodeScalarViewIteration([ 0x10ffff ], "\u{0010ffff}")
 }
 
-StringTests.test("indexComparability") {
+StringTests.test("Index/Comparable") {
   let empty = ""
   expectTrue(empty.startIndex == empty.endIndex)
   expectFalse(empty.startIndex != empty.endIndex)
@@ -166,6 +166,13 @@ StringTests.test("indexComparability") {
   expectTrue(nonEmpty.startIndex < nonEmpty.endIndex)
 }
 
+StringTests.test("Index/Hashable") {
+  let s = "abcdef"
+  let t = Set(s.indices)
+  expectEqual(s.count, t.count)
+  expectTrue(t.contains(s.startIndex))
+}
+
 StringTests.test("ForeignIndexes/Valid") {
   // It is actually unclear what the correct behavior is.  This test is just a
   // change detector.