[stdlib] Handle some outstanding Dictionary indexing-model FIXMEs/TODOs

stdlib/public/core/HashedCollections.swift.gyb

@@ -454,7 +454,10 @@ public struct Set<Element : Hashable> :
     return _variantStorage.endIndex
   }
 
-  // TODO: swift-3-indexing-model - add docs
+  /// Returns the index after the given one. 
+  ///
+  /// If this is the last valid index, returns endIndex.
+  /// Aborts on endIndex.
   public func index(after i: Index) -> Index {
     return _variantStorage.index(after: i)
   }
@@ -1662,7 +1665,10 @@ public struct Dictionary<Key : Hashable, Value> :
     return _variantStorage.endIndex
   }
 
-  // TODO: swift-3-indexing-model - add docs
+  /// Returns the index after the given one. 
+  ///
+  /// If this is the last valid index, returns endIndex.
+  /// Aborts on endIndex.
   public func index(after i: Index) -> Index {
     return _variantStorage.index(after: i)
   }
@@ -2063,15 +2069,15 @@ extension Dictionary where Key : Equatable, Value : Equatable {
         let (key, value) = lhsNative.assertingGet(index)
         let optRhsValue: AnyObject? =
           rhsCocoa.maybeGet(_bridgeAnythingToObjectiveC(key))
-        // TODO: swift-3-indexing-model: change 'if' into 'guard'.
-        if let rhsValue = optRhsValue {
-          if value == _forceBridgeFromObjectiveC(rhsValue, Value.self) {
-            lhsNative.formIndex(after: &index)
-            continue
-          }
+
+        guard let rhsValue = optRhsValue,
+          value == _forceBridgeFromObjectiveC(rhsValue, Value.self)
+        else {
+          return false
         }
-        index = lhsNative.index(after: index)
-        return false
+
+        lhsNative.formIndex(after: &index)
+        continue
       }
       return true
   #else
@@ -4321,6 +4327,10 @@ internal enum _Variant${Self}Storage<${TypeParametersDecl}> : _HashStorage {
   }
 }
 
+%{
+  compareOperators = ["<", "<=", ">", ">=", "=="]
+}%
+
 @_versioned
 internal struct _Native${Self}Index<${TypeParametersDecl}> : Comparable {
   @_versioned
@@ -4333,24 +4343,19 @@ internal struct _Native${Self}Index<${TypeParametersDecl}> : Comparable {
 }
 
 extension _Native${Self}Index {
-  internal static func == (
-    lhs: _Native${Self}Index<${TypeParameters}>,
-    rhs: _Native${Self}Index<${TypeParameters}>
-  ) -> Bool {
-    // FIXME: assert that lhs and rhs are from the same dictionary.
-    return lhs.offset == rhs.offset
-  }
 
-  internal static func < (
+% for op in compareOperators:
+  internal static func ${op} (
     lhs: _Native${Self}Index<${TypeParameters}>,
     rhs: _Native${Self}Index<${TypeParameters}>
   ) -> Bool {
-    // FIXME: assert that lhs and rhs are from the same dictionary.
-    return lhs.offset < rhs.offset
+    return lhs.offset ${op} rhs.offset
   }
-  // TODO: swift-3-indexing-model: forward all Comparable operations.
+% end
+
 }
 
+
 #if _runtime(_ObjC)
 @_versioned
 internal struct _Cocoa${Self}Index : Comparable {
@@ -4363,19 +4368,16 @@ internal struct _Cocoa${Self}Index : Comparable {
 }
 
 extension _Cocoa${Self}Index {
-  internal static func == (
-    lhs: _Cocoa${Self}Index,
-    rhs: _Cocoa${Self}Index
-  ) -> Bool {
-    return lhs.currentKeyIndex == rhs.currentKeyIndex
-  }
 
-  internal static func < (
+% for op in compareOperators:
+  internal static func ${op} (
     lhs: _Cocoa${Self}Index,
     rhs: _Cocoa${Self}Index
   ) -> Bool {
-    return lhs.currentKeyIndex < rhs.currentKeyIndex
+    return lhs.currentKeyIndex ${op} rhs.currentKeyIndex
   }
+% end
+
 }
 #else
 internal struct _Cocoa${Self}Index {}
@@ -4413,9 +4415,8 @@ elif Self == 'Dictionary':
 ${SubscriptingWithIndexDoc}
 public struct ${Self}Index<${TypeParametersDecl}> :
   Comparable {
-  // FIXME(swift-3-indexing-model): rewrite the fixme to reflect the new index model
   // FIXME(ABI)#34 (Nesting types in generics): `DictionaryIndex` and `SetIndex` should
-  // be nested types.
+  // be nested types (Dictionary.Index and Set.Index).
   // rdar://problem/17002096
 
   // Index for native storage is efficient.  Index for bridged NS${Self} is