[Mirrors] Use tuple labels when forming a mirror for a tuple type.

Fixes rdar://problem/22191852.

Author: DougGregor

stdlib/public/runtime/Reflection.mm

@@ -372,12 +372,30 @@ void swift_TupleMirror_subscript(String *outString,
 
   if (i < 0 || (size_t)i > Tuple->NumElements)
     swift::crash("Swift mirror subscript bounds check failure");
-  
-  // The name is the stringized element number '.0'.
-  char buf[32];
-  snprintf(buf, sizeof(buf), ".%zd", i);
-  new (outString) String(buf, strlen(buf));
-  
+
+  // Determine whether there is a label.
+  bool hasLabel = false;
+  if (const char *labels = Tuple->Labels) {
+    const char *space = strchr(labels, ' ');
+    for (intptr_t j = 0; j != i && space; ++j) {
+      labels = space + 1;
+      space = strchr(labels, ' ');
+    }
+
+    // If we have a label, create it.
+    if (labels && space && labels != space) {
+      new (outString) String(labels, space - labels);
+      hasLabel = true;
+    }
+  }
+
+  if (!hasLabel) {
+    // The name is the stringized element number '.0'.
+    char buf[32];
+    snprintf(buf, sizeof(buf), ".%zd", i);
+    new (outString) String(buf, strlen(buf));
+  }
+
   // Get a Mirror for the nth element.
   auto &elt = Tuple->getElement(i);
   auto bytes = reinterpret_cast<const char*>(value);

test/stdlib/DebuggerSupport.swift

@@ -78,7 +78,8 @@ StringForPrintObjectTests.test("Array") {
 
 StringForPrintObjectTests.test("Dictionary") {
   let printed = _DebuggerSupport.stringForPrintObject([1:2])
-  expectEqual(printed, "▿ 1 element\n  ▿ 0 : 2 elements\n    - .0 : 1\n    - .1 : 2\n")
+  expectEqual("▿ 1 element\n  ▿ 0 : 2 elements\n    - key : 1\n    - value : 2\n",
+              printed)
 }
 
 StringForPrintObjectTests.test("NilOptional") {

test/stdlib/Mirror.swift

@@ -653,10 +653,10 @@ mirrors.test("Addressing") {
   expectEqual(2, m0.descendant(1) as? Int)
   expectEqual(3, m0.descendant(2) as? Int)
 
-  let m1 = Mirror(reflecting: (a: ["one", "two", "three"], b: 4))
+  let m1 = Mirror(reflecting: (a: ["one", "two", "three"], 4))
   let ott0 = m1.descendant(0) as? [String]
   expectNotNil(ott0)
-  let ott1 = m1.descendant(".0") as? [String]
+  let ott1 = m1.descendant("a") as? [String]
   expectNotNil(ott1)
   if ott0 != nil && ott1 != nil {
     expectEqualSequence(ott0!, ott1!)
@@ -666,7 +666,7 @@ mirrors.test("Addressing") {
   expectEqual("one", m1.descendant(0, 0) as? String)
   expectEqual("two", m1.descendant(0, 1) as? String)
   expectEqual("three", m1.descendant(0, 2) as? String)
-  expectEqual("one", m1.descendant(".0", 0) as? String)
+  expectEqual("one", m1.descendant("a", 0) as? String)
 
   struct Zee : CustomReflectable {
     var customMirror: Mirror {
@@ -680,7 +680,7 @@ mirrors.test("Addressing") {
     (a: [], b: Zee())]
 
   let m = Mirror(reflecting: x)
-  let two = m.descendant(0, ".0", 1)
+  let two = m.descendant(0, "a", 1)
   expectEqual("two", two as? String)
   expectEqual(1, m.descendant(1, 1, "bark") as? Int)
   expectEqual(0, m.descendant(1, 1, "bite") as? Int)