[Sema] Disallow conditional conformances on objective-c generics.

include/swift/AST/DiagnosticsSema.def

@@ -1426,6 +1426,10 @@ ERROR(objc_runtime_visible_cannot_conform_to_objc_protocol,none,
       "class %0 cannot conform to @objc protocol %1 because "
       "the class is only visible via the Objective-C runtime",
       (Type, Type))
+ERROR(objc_generics_cannot_conditionally_conform,none,
+      "type %0 cannot conditionally conform to protocol %1 because "
+      "the type uses the Objective-C generics model",
+      (Type, Type))
 ERROR(protocol_has_missing_requirements,none,
       "type %0 cannot conform to protocol %1 because it has requirements that "
       "cannot be satisfied", (Type, Type))

include/swift/AST/PrintOptions.h

@@ -16,6 +16,7 @@
 #include "swift/Basic/STLExtras.h"
 #include "swift/AST/AttrKind.h"
 #include "swift/AST/Identifier.h"
+#include "swift/AST/TypeOrExtensionDecl.h"
 #include "llvm/ADT/Optional.h"
 #include <limits.h>
 #include <vector>
@@ -36,32 +37,6 @@ enum DeclAttrKind : unsigned;
 class SynthesizedExtensionAnalyzer;
 struct PrintOptions;
 
-/// \brief Describes either a nominal type declaration or an extension
-/// declaration.
-struct TypeOrExtensionDecl {
-  llvm::PointerUnion<NominalTypeDecl *, ExtensionDecl *> Decl;
-
-  TypeOrExtensionDecl() = default;
-
-  TypeOrExtensionDecl(NominalTypeDecl *D);
-  TypeOrExtensionDecl(ExtensionDecl *D);
-
-  /// \brief Return the contained *Decl as the Decl superclass.
-  class Decl *getAsDecl() const;
-  /// \brief Return the contained *Decl as the DeclContext superclass.
-  DeclContext *getAsDeclContext() const;
-  /// \brief Return the contained NominalTypeDecl or that of the extended type
-  /// in the ExtensionDecl.
-  NominalTypeDecl *getBaseNominal() const;
-
-  /// \brief Is the contained pointer null?
-  bool isNull() const;
-  explicit operator bool() const { return !isNull(); }
-
-  bool operator==(TypeOrExtensionDecl rhs) { return Decl == rhs.Decl; }
-  bool operator!=(TypeOrExtensionDecl rhs) { return Decl != rhs.Decl; }
-  bool operator<(TypeOrExtensionDecl rhs) { return Decl < rhs.Decl; }
-};
 
 /// Necessary information for archetype transformation during printing.
 struct TypeTransformContext {

include/swift/AST/TypeAlignments.h

@@ -37,6 +37,7 @@ namespace swift {
   class ExtensionDecl;
   class GenericEnvironment;
   class GenericTypeParamDecl;
+  class NominalTypeDecl;
   class NormalProtocolConformance;
   class OperatorDecl;
   class Pattern;
@@ -90,6 +91,7 @@ LLVM_DECLARE_TYPE_ALIGNMENT(swift::OperatorDecl, swift::DeclAlignInBits)
 LLVM_DECLARE_TYPE_ALIGNMENT(swift::ProtocolDecl, swift::DeclAlignInBits)
 LLVM_DECLARE_TYPE_ALIGNMENT(swift::TypeDecl, swift::DeclAlignInBits)
 LLVM_DECLARE_TYPE_ALIGNMENT(swift::ValueDecl, swift::DeclAlignInBits)
+LLVM_DECLARE_TYPE_ALIGNMENT(swift::NominalTypeDecl, swift::DeclAlignInBits)
 LLVM_DECLARE_TYPE_ALIGNMENT(swift::ExtensionDecl, swift::DeclAlignInBits)
 
 LLVM_DECLARE_TYPE_ALIGNMENT(swift::TypeBase, swift::TypeAlignInBits)

include/swift/AST/TypeOrExtensionDecl.h

@@ -0,0 +1,56 @@
+//===- TypeOrExtensionDecl.h - Swift Language Declaration ASTs -*- C++ -*-===//
+//
+// This source file is part of the Swift.org open source project
+//
+// Copyright (c) 2014 - 2017 Apple Inc. and the Swift project authors
+// Licensed under Apache License v2.0 with Runtime Library Exception
+//
+// See https://swift.org/LICENSE.txt for license information
+// See https://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
+//
+//===----------------------------------------------------------------------===//
+//
+// This file defines the TypeOrExtensionDecl struct, separately to Decl.h so
+// that this can be included in files that Decl.h includes.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef SWIFT_TYPE_OR_EXTENSION_DECL_H
+#define SWIFT_TYPE_OR_EXTENSION_DECL_H
+
+#include "swift/AST/TypeAlignments.h"
+#include "llvm/ADT/PointerUnion.h"
+
+namespace swift {
+
+/// \brief Describes either a nominal type declaration or an extension
+/// declaration.
+struct TypeOrExtensionDecl {
+  // (The definitions are in Decl.cpp.)
+  llvm::PointerUnion<NominalTypeDecl *, ExtensionDecl *> Decl;
+
+  TypeOrExtensionDecl() = default;
+
+  TypeOrExtensionDecl(NominalTypeDecl *D);
+  TypeOrExtensionDecl(ExtensionDecl *D);
+
+  /// \brief Return the contained *Decl as the Decl superclass.
+  class Decl *getAsDecl() const;
+  /// \brief Return the contained *Decl as the DeclContext superclass.
+  DeclContext *getAsDeclContext() const;
+  /// \brief Return the contained NominalTypeDecl or that of the extended type
+  /// in the ExtensionDecl.
+  NominalTypeDecl *getBaseNominal() const;
+
+  /// \brief Is the contained pointer null?
+  bool isNull() const;
+  explicit operator bool() const { return !isNull(); }
+
+  bool operator==(TypeOrExtensionDecl rhs) { return Decl == rhs.Decl; }
+  bool operator!=(TypeOrExtensionDecl rhs) { return Decl != rhs.Decl; }
+  bool operator<(TypeOrExtensionDecl rhs) { return Decl < rhs.Decl; }
+};
+
+} // end namespace swift
+
+#endif

lib/AST/ASTPrinter.cpp

@@ -63,23 +63,6 @@ void PrintOptions::clearSynthesizedExtension() {
   TransformContext.reset();
 }
 
-TypeOrExtensionDecl::TypeOrExtensionDecl(NominalTypeDecl *D) : Decl(D) {}
-TypeOrExtensionDecl::TypeOrExtensionDecl(ExtensionDecl *D) : Decl(D) {}
-
-Decl *TypeOrExtensionDecl::getAsDecl() const {
-  if (auto NTD = Decl.dyn_cast<NominalTypeDecl *>())
-    return NTD;
-
-  return Decl.get<ExtensionDecl *>();
-}
-DeclContext *TypeOrExtensionDecl::getAsDeclContext() const {
-  return getAsDecl()->getInnermostDeclContext();
-}
-NominalTypeDecl *TypeOrExtensionDecl::getBaseNominal() const {
-  return getAsDeclContext()->getAsNominalTypeOrNominalTypeExtensionContext();
-}
-bool TypeOrExtensionDecl::isNull() const { return Decl.isNull(); }
-
 TypeTransformContext::TypeTransformContext(Type T)
     : BaseType(T.getPointer()) {
   assert(T->mayHaveMembers());

lib/AST/Decl.cpp

@@ -5689,3 +5689,20 @@ UnifiedStatsReporter::getStatsTracer(StringRef EventName, const Decl *D) {
     // Return inert tracer object.
     return FrontendStatsTracer();
 }
+
+TypeOrExtensionDecl::TypeOrExtensionDecl(NominalTypeDecl *D) : Decl(D) {}
+TypeOrExtensionDecl::TypeOrExtensionDecl(ExtensionDecl *D) : Decl(D) {}
+
+Decl *TypeOrExtensionDecl::getAsDecl() const {
+  if (auto NTD = Decl.dyn_cast<NominalTypeDecl *>())
+    return NTD;
+
+  return Decl.get<ExtensionDecl *>();
+}
+DeclContext *TypeOrExtensionDecl::getAsDeclContext() const {
+  return getAsDecl()->getInnermostDeclContext();
+}
+NominalTypeDecl *TypeOrExtensionDecl::getBaseNominal() const {
+  return getAsDeclContext()->getAsNominalTypeOrNominalTypeExtensionContext();
+}
+bool TypeOrExtensionDecl::isNull() const { return Decl.isNull(); }

lib/Sema/TypeCheckProtocol.cpp

@@ -1359,6 +1359,27 @@ checkIndividualConformance(NormalProtocolConformance *conformance,
     }
   }
 
+  // Not every protocol/type is compatible with conditional conformances.
+  if (!conformance->getConditionalRequirements().empty()) {
+    auto nestedType = canT;
+    // Obj-C generics cannot be looked up at runtime, so we don't support
+    // conditional conformances involving them. Check the full stack of nested
+    // types for any obj-c ones.
+    while (nestedType) {
+      if (auto clas = nestedType->getClassOrBoundGenericClass()) {
+        if (clas->usesObjCGenericsModel()) {
+          TC.diagnose(ComplainLoc,
+                      diag::objc_generics_cannot_conditionally_conform, T,
+                      Proto->getDeclaredType());
+          conformance->setInvalid();
+          return conformance;
+        }
+      }
+
+      nestedType = nestedType.getNominalParent();
+    }
+  }
+
   // If the protocol contains missing requirements, it can't be conformed to
   // at all.
   if (Proto->hasMissingRequirements()) {

test/Generics/Inputs/conditional_conformances_objc.h

@@ -0,0 +1,7 @@
+@import Foundation;
+
+@interface ObjC <ObjectType>: NSObject
+@end
+
+@interface ObjC2: NSObject
+@end

test/Generics/conditional_conformances_objc.swift

@@ -0,0 +1,34 @@
+// RUN: %target-typecheck-verify-swift -import-objc-header %S/Inputs/conditional_conformances_objc.h
+
+// REQUIRES: objc_interop
+
+protocol Foo {}
+extension ObjC: Foo where ObjectType == ObjC2 {}
+// expected-error@-1{{type 'ObjC<ObjectType>' cannot conditionally conform to protocol 'Foo' because the type uses the Objective-C generics model}}
+
+protocol Bar {}
+extension ObjC: Bar where ObjectType: Bar {}
+// expected-error@-1{{type 'ObjC<ObjectType>' cannot conditionally conform to protocol 'Bar' because the type uses the Objective-C generics model}}
+
+extension ObjC {
+    struct Struct {
+        enum Enum {}
+    }
+    class Class<T> {}
+}
+
+extension ObjC.Struct: Foo where ObjectType == ObjC2 {}
+// expected-error@-1{{type 'ObjC<ObjectType>.Struct' cannot conditionally conform to protocol 'Foo' because the type uses the Objective-C generics model}}
+extension ObjC.Struct: Bar where ObjectType: Bar {}
+// expected-error@-1{{type 'ObjC<ObjectType>.Struct' cannot conditionally conform to protocol 'Bar' because the type uses the Objective-C generics model}}
+
+extension ObjC.Struct.Enum: Foo where ObjectType == ObjC2 {}
+// expected-error@-1{{type 'ObjC<ObjectType>.Struct.Enum' cannot conditionally conform to protocol 'Foo' because the type uses the Objective-C generics model}}
+extension ObjC.Struct.Enum: Bar where ObjectType: Bar {}
+// expected-error@-1{{type 'ObjC<ObjectType>.Struct.Enum' cannot conditionally conform to protocol 'Bar' because the type uses the Objective-C generics model}}
+
+extension ObjC.Class: Foo where T == ObjC2 {}
+// expected-error@-1{{type 'ObjC<ObjectType>.Class<T>' cannot conditionally conform to protocol 'Foo' because the type uses the Objective-C generics model}}
+extension ObjC.Class: Bar where T: Bar {}
+// expected-error@-1{{type 'ObjC<ObjectType>.Class<T>' cannot conditionally conform to protocol 'Bar' because the type uses the Objective-C generics model}}
+