Fix MetadataReader handling of @objc protocols in existentials

Author: slavapestov

include/swift/Remote/MetadataReader.h

@@ -498,20 +498,39 @@ class MetadataReader {
 #if SWIFT_OBJC_INTEROP
         // Check whether we have an Objective-C protocol.
         if (ProtocolAddress.isObjC()) {
-          auto MangledNameStr =
+          auto Name =
             readObjCProtocolName(ProtocolAddress.getObjCProtocol());
+          StringRef NameStr(Name);
+
+          // If this is a Swift-defined protocol, demangle it.
+          if (NameStr.startswith("_TtP")) {
+            Demangle::Context DCtx;
+            auto Demangled = DCtx.demangleSymbolAsNode(NameStr);
+            if (!Demangled)
+              return BuiltType();
+
+            // FIXME: This appears in _swift_buildDemanglingForMetadata().
+            while (Demangled->getKind() == Node::Kind::Global ||
+                   Demangled->getKind() == Node::Kind::TypeMangling ||
+                   Demangled->getKind() == Node::Kind::Type ||
+                   Demangled->getKind() == Node::Kind::ProtocolList ||
+                   Demangled->getKind() == Node::Kind::TypeList ||
+                   Demangled->getKind() == Node::Kind::Type) {
+              if (Demangled->getNumChildren() != 1)
+                return BuiltType();
+              Demangled = Demangled->getFirstChild();
+            }
+
+            auto Protocol = Builder.createProtocolDecl(Demangled);
+            if (!Protocol)
+              return BuiltType();
+
+            Protocols.push_back(Protocol);
+            continue;
+          }
 
-          StringRef MangledName =
-            Demangle::dropSwiftManglingPrefix(MangledNameStr);
-
-          Demangle::Context DCtx;
-          auto Demangled = DCtx.demangleTypeAsNode(MangledName);
-          if (!Demangled)
-            return BuiltType();
-
-          // FIXME: Imported protocols?
-
-          auto Protocol = Builder.createProtocolDecl(Demangled);
+          // Otherwise, this is an imported protocol.
+          auto Protocol = Builder.createObjCProtocolDecl(NameStr);
           if (!Protocol)
             return BuiltType();
 
@@ -520,6 +539,7 @@ class MetadataReader {
         }
 #endif
 
+        // Swift-native protocol.
         Demangle::Demangler Dem;
         auto Demangled = readDemanglingForContextDescriptor(
             ProtocolAddress.getSwiftProtocol(), Dem);

test/RemoteAST/objc_classes.swift

@@ -26,3 +26,19 @@ let observer = NSObject()
 a.addObserver(observer, forKeyPath: "property", options: [], context: nil)
 printDynamicType(a)
 // CHECK: A<Int>
+
+// FIXME: The ... & AnyObject is redundant here:
+
+printType(NSFastEnumeration.self)
+// CHECK: NSFastEnumeration & AnyObject
+
+printType(Optional<NSFastEnumeration>.self)
+// CHECK: Optional<NSFastEnumeration & AnyObject>
+
+@objc protocol OurObjCProtocol {}
+
+printType(OurObjCProtocol.self)
+// CHECK: OurObjCProtocol & AnyObject
+
+printType(Optional<OurObjCProtocol>.self)
+// CHECK: Optional<OurObjCProtocol & AnyObject>