swiftlang · slavapestov · Nov 18, 2016 · Nov 18, 2016 · Nov 1, 2016 · Nov 18, 2016
diff --git a/CHANGELOG.md b/CHANGELOG.md
@@ -20,6 +20,26 @@ CHANGELOG
 Swift 3.1
 ---------
 
+* [SR-1446](https://bugs.swift.org/browse/SR-1446)
+
+  Nested types may now appear inside generic types, and nested types may have their own generic parameters:
+
+  ```swift
+  struct OuterNonGeneric {
+      struct InnerGeneric<T> {}
+  }
+
+  struct OuterGeneric<T> {
+      struct InnerNonGeneric {}
+
+      struct InnerGeneric<T> {}
+  }
+
+  extension OuterNonGeneric.InnerGeneric {}
+  extension OuterGeneric.InnerNonGeneric {}
+  extension OuterGeneric.InnerGeneric {}
+  ```
+
 * [SR-1009](https://bugs.swift.org/browse/SR-1009):
 
   Constrained extensions allow same-type constraints between generic parameters and concrete types. This enables you to create extensions, for example, on `Array` with `Int` elements:

diff --git a/include/swift/AST/DiagnosticsSema.def b/include/swift/AST/DiagnosticsSema.def
@@ -1144,15 +1144,6 @@ ERROR(pattern_binds_no_variables,none,
 
 
 // Generic types
-ERROR(unsupported_generic_nested_in_type,none,
-      "generic type %0 cannot be nested in type %1",
-      (Identifier, Identifier))
-ERROR(unsupported_type_nested_in_generic_type,none,
-      "type %0 cannot be nested in generic type %1",
-      (Identifier, Identifier))
-ERROR(unsupported_type_nested_in_generic_extension,none,
-      "type %0 cannot be nested in extension of generic type %1",
-      (Identifier, Identifier))
 ERROR(unsupported_type_nested_in_generic_function,none,
       "type %0 cannot be nested in generic function %1",
       (Identifier, Identifier))

diff --git a/include/swift/Basic/LangOptions.h b/include/swift/Basic/LangOptions.h
@@ -141,9 +141,6 @@ namespace swift {
     /// \brief Enable experimental property behavior feature.
     bool EnableExperimentalPropertyBehaviors = false;
 
-    /// \brief Enable experimental nested generic types feature.
-    bool EnableExperimentalNestedGenericTypes = false;
-
     /// \brief Staging flag for class resilience, which we do not want to enable
     /// fully until more code is in place, to allow the standard library to be
     /// tested with value type resilience only.

diff --git a/include/swift/Option/FrontendOptions.td b/include/swift/Option/FrontendOptions.td
@@ -240,10 +240,6 @@ def enable_experimental_property_behaviors :
   Flag<["-"], "enable-experimental-property-behaviors">,
   HelpText<"Enable experimental property behaviors">;
 
-def enable_experimental_nested_generic_types :
-  Flag<["-"], "enable-experimental-nested-generic-types">,
-  HelpText<"Enable experimental support for nested generic types">;
-
 def disable_availability_checking : Flag<["-"],
   "disable-availability-checking">,
   HelpText<"Disable checking for potentially unavailable APIs">;

diff --git a/lib/Basic/Demangle.cpp b/lib/Basic/Demangle.cpp
@@ -2396,6 +2396,11 @@ class NodePrinter {
     case Node::Kind::VariadicTuple:
       return true;
 
+    case Node::Kind::ProtocolList:
+      if (pointer->getChild(0)->getNumChildren() <= 1)
+        return true;
+      return false;
+
     case Node::Kind::Allocator:
     case Node::Kind::ArgumentTuple:
     case Node::Kind::AssociatedTypeMetadataAccessor:
@@ -2473,7 +2478,6 @@ class NodePrinter {
     case Node::Kind::PrefixOperator:
     case Node::Kind::ProtocolConformance:
     case Node::Kind::ProtocolDescriptor:
-    case Node::Kind::ProtocolList:
     case Node::Kind::ProtocolWitness:
     case Node::Kind::ProtocolWitnessTable:
     case Node::Kind::ProtocolWitnessTableAccessor:
@@ -2686,8 +2690,6 @@ class NodePrinter {
 } // end anonymous namespace
 
 static bool isExistentialType(NodePointer node) {
-  assert(node->getKind() == Node::Kind::Type);
-  node = node->getChild(0);
   return (node->getKind() == Node::Kind::ExistentialMetatype ||
           node->getKind() == Node::Kind::ProtocolList);
 }
@@ -3004,7 +3006,10 @@ void NodePrinter::print(NodePointer pointer, bool asContext, bool suppressType)
       if (!pointer->hasChildren())
         need_parens = true;
       else {
-        Node::Kind child0_kind = pointer->getChild(0)->getChild(0)->getKind();
+        Node::Kind child0_kind = pointer->getChild(0)->getKind();
+        if (child0_kind == Node::Kind::Type)
+          child0_kind = pointer->getChild(0)->getChild(0)->getKind();
+
         if (child0_kind != Node::Kind::VariadicTuple &&
             child0_kind != Node::Kind::NonVariadicTuple)
           need_parens = true;
@@ -3410,8 +3415,13 @@ void NodePrinter::print(NodePointer pointer, bool asContext, bool suppressType)
       Printer << " ";
       Idx++;
     }
-    NodePointer type = pointer->getChild(Idx);
+    NodePointer type = pointer->getChild(Idx)->getChild(0);
+    bool needs_parens = !isSimpleType(type);
+    if (needs_parens)
+      Printer << "(";
     print(type);
+    if (needs_parens)
+      Printer << ")";
     if (isExistentialType(type)) {
       Printer << ".Protocol";
     } else {

diff --git a/lib/Frontend/CompilerInvocation.cpp b/lib/Frontend/CompilerInvocation.cpp
@@ -804,9 +804,6 @@ static bool ParseLangArgs(LangOptions &Opts, ArgList &Args,
   Opts.EnableExperimentalPropertyBehaviors |=
     Args.hasArg(OPT_enable_experimental_property_behaviors);
 
-  Opts.EnableExperimentalNestedGenericTypes |=
-    Args.hasArg(OPT_enable_experimental_nested_generic_types);
-
   Opts.EnableClassResilience |=
     Args.hasArg(OPT_enable_class_resilience);
 

diff --git a/lib/Sema/TypeCheckDecl.cpp b/lib/Sema/TypeCheckDecl.cpp
@@ -3969,33 +3969,6 @@ class DeclChecker : public DeclVisitor<DeclChecker> {
         return true;
       }
 
-      if (!TC.Context.LangOpts.EnableExperimentalNestedGenericTypes) {
-        if (auto parent = dyn_cast<NominalTypeDecl>(DC)) {
-          if (NTD->getGenericParams())
-            TC.diagnose(NTD->getLoc(), diag::unsupported_generic_nested_in_type,
-                        NTD->getName(),
-                        parent->getName());
-          else
-            TC.diagnose(NTD->getLoc(),
-                        diag::unsupported_type_nested_in_generic_type,
-                        NTD->getName(),
-                        parent->getName());
-          NTD->setInvalid();
-          return true;
-        } else if (auto ED = dyn_cast<ExtensionDecl>(DC)) {
-          auto *parent = ED->getAsNominalTypeOrNominalTypeExtensionContext();
-          if (parent == nullptr) {
-            /* Invalid extension -- diagnosed elsewhere */
-            return true;
-          }
-
-          TC.diagnose(NTD->getLoc(),
-                      diag::unsupported_type_nested_in_generic_extension,
-                      NTD->getName(),
-                      parent->getName());
-        }
-      }
-
       if (DC->isLocalContext() && DC->isGenericContext()) {
         // A local generic context is a generic function.
         if (auto AFD = dyn_cast<AbstractFunctionDecl>(DC)) {

diff --git a/stdlib/public/core/HashedCollections.swift.gyb b/stdlib/public/core/HashedCollections.swift.gyb
@@ -451,9 +451,6 @@ public struct Set<Element : Hashable> :
   internal typealias _VariantBuffer = _VariantSetBuffer<Element>
   internal typealias _NativeBuffer = _NativeSetBuffer<Element>
 
-  /// The index type for subscripting the set.
-  public typealias Index = SetIndex<Element>
-
   internal var _variantBuffer: _VariantBuffer
 
   /// Creates a new, empty set with at least the specified number of elements'
@@ -1642,9 +1639,6 @@ public struct Dictionary<Key : Hashable, Value> :
   /// key-value pair.
   public typealias Element = (key: Key, value: Value)
 
-  /// The index type of a dictionary.
-  public typealias Index = DictionaryIndex<Key, Value>
-
   internal var _variantBuffer: _VariantBuffer
 
   /// Creates an empty dictionary.
@@ -4705,6 +4699,7 @@ internal enum ${Self}IndexRepresentation<${TypeParametersDecl}> {
   case _cocoa(_CocoaIndex)
 }
 
+extension ${Self} {
 %{
 if Self == 'Set':
   SubscriptingWithIndexDoc = """\
@@ -4726,12 +4721,7 @@ elif Self == 'Dictionary':
 }%
 
 ${SubscriptingWithIndexDoc}
-public struct ${Self}Index<${TypeParametersDecl}> :
-  Comparable {
-  // FIXME(ABI)#34 (Nesting types in generics): `DictionaryIndex` and `SetIndex` should
-  // be nested types (Dictionary.Index and Set.Index).
-  // rdar://problem/17002096
-
+public struct Index : Comparable {
   // Index for native buffer is efficient.  Index for bridged NS${Self} is
   // not, because neither NSEnumerator nor fast enumeration support moving
   // backwards.  Even if they did, there is another issue: NSEnumerator does
@@ -4750,12 +4740,12 @@ public struct ${Self}Index<${TypeParametersDecl}> :
   internal var _value: ${Self}IndexRepresentation<${TypeParameters}>
 
   @_versioned
-  internal static func _native(_ index: _NativeIndex) -> ${Self}Index {
+  internal static func _native(_ index: _NativeIndex) -> Index {
     return ${Self}Index(_value: ._native(index))
   }
 #if _runtime(_ObjC)
   @_versioned
-  internal static func _cocoa(_ index: _CocoaIndex) -> ${Self}Index {
+  internal static func _cocoa(_ index: _CocoaIndex) -> Index {
     return ${Self}Index(_value: ._cocoa(index))
   }
 #endif
@@ -4789,10 +4779,15 @@ public struct ${Self}Index<${TypeParametersDecl}> :
 #endif
 }
 
-extension ${Self}Index {
+}
+
+public typealias ${Self}Index<${TypeParametersDecl}> =
+    ${Self}<${TypeParameters}>.Index
+
+extension ${Self}.Index {
   public static func == (
-    lhs: ${Self}Index<${TypeParameters}>,
-    rhs: ${Self}Index<${TypeParameters}>
+    lhs: ${Self}<${TypeParameters}>.Index,
+    rhs: ${Self}<${TypeParameters}>.Index
   ) -> Bool {
     if _fastPath(lhs._guaranteedNative) {
       return lhs._nativeIndex == rhs._nativeIndex
@@ -4813,8 +4808,8 @@ extension ${Self}Index {
   }
 
   public static func < (
-    lhs: ${Self}Index<${TypeParameters}>,
-    rhs: ${Self}Index<${TypeParameters}>
+    lhs: ${Self}<${TypeParameters}>.Index,
+    rhs: ${Self}<${TypeParameters}>.Index
   ) -> Bool {
     if _fastPath(lhs._guaranteedNative) {
       return lhs._nativeIndex < rhs._nativeIndex