Merge pull request #71426 from DougGregor/lift-retroactive-objc-bridgeable-conformance

Remove an old restriction on `_ObjectiveCBridgeable` conformances.

Author: DougGregor

include/swift/AST/DiagnosticsSema.def

@@ -6310,10 +6310,6 @@ ERROR(objc_ambiguous_error_convention,none,
 NOTE(objc_ambiguous_error_convention_candidate,none,
      "%0 provides an error argument here", (const ValueDecl *))
 
-ERROR(nonlocal_bridged_to_objc,none,
-      "conformance of %0 to %1 can only be written in module %2",
-      (Identifier, Identifier, Identifier))
-
 ERROR(missing_bridging_function,Fatal,
       "missing '%select{_forceBridgeFromObjectiveC|"
       "_conditionallyBridgeFromObjectiveC}0'", (bool))

lib/Sema/TypeCheckProtocol.cpp

@@ -2389,29 +2389,6 @@ checkIndividualConformance(NormalProtocolConformance *conformance) {
     }
   }
 
-  // Except in specific hardcoded cases for Foundation/Swift
-  // standard library compatibility, an _ObjectiveCBridgeable
-  // conformance must appear in the same module as the definition of
-  // the conforming type.
-  //
-  // Note that we check the module name to smooth over the difference
-  // between an imported Objective-C module and its overlay.
-  if (Proto->isSpecificProtocol(KnownProtocolKind::ObjectiveCBridgeable)) {
-    auto nominal = DC->getSelfNominalTypeDecl();
-    if (!Context.isTypeBridgedInExternalModule(nominal)) {
-      auto clangLoader = Context.getClangModuleLoader();
-      if (nominal->getParentModule() != DC->getParentModule() &&
-          !(clangLoader &&
-            clangLoader->isInOverlayModuleForImportedModule(DC, nominal))) {
-        auto nominalModule = nominal->getParentModule();
-        Context.Diags.diagnose(conformance->getLoc(),
-                               diag::nonlocal_bridged_to_objc,
-                               nominal->getName(), Proto->getName(),
-                               nominalModule->getName());
-      }
-    }
-  }
-
   // Check that T conforms to all inherited protocols.
   for (auto InheritedProto : Proto->getInheritedProtocols()) {
     auto InheritedConformance =

test/Constraints/bridging.swift

@@ -13,9 +13,10 @@ public class BridgedClass : NSObject, NSCopying {
 
 public class BridgedClassSub : BridgedClass { }
 
-// Attempt to bridge to a type from another module. We only allow this for a
-// few specific types, like String.
-extension LazyFilterSequence.Iterator : @retroactive _ObjectiveCBridgeable { // expected-error{{conformance of 'Iterator' to '_ObjectiveCBridgeable' can only be written in module 'Swift'}}
+// Attempt to bridge to a type from another module.
+// We used to work hard to prevent this, but doing so was getting in the
+// way of layering for the swift-foundation project.
+extension LazyFilterSequence.Iterator : @retroactive _ObjectiveCBridgeable {
   public typealias _ObjectiveCType = BridgedClassSub
 
   public func _bridgeToObjectiveC() -> _ObjectiveCType {