[Runtime] Form existential types and existential types based on mangled names.

Introduce basic support for existential types (just Any and AnyObject), so
we can test those, shared/owned parameters, and existential metatypes.

Author: DougGregor

stdlib/public/runtime/MetadataLookup.cpp

@@ -285,15 +285,19 @@ class DecodedMetadataBuilder {
   }
 
   BuiltType createExistentialMetatypeType(BuiltType instance) const {
-    // FIXME: Implement.
-    return BuiltType();
+    return swift_getExistentialMetatypeMetadata(instance);
   }
 
   BuiltType createProtocolCompositionType(ArrayRef<BuiltType> protocols,
                                           bool hasExplicitAnyObject) const {
-    // FIXME: Implement.
-    // NOTE: protocols.back() could be a class type. Clean up this API.
-    return BuiltType();
+    // FIXME: Handle protocols and superclasses.
+    if (!protocols.empty()) return BuiltType();
+
+    auto classConstraint =
+      hasExplicitAnyObject ? ProtocolClassConstraint::Class
+                           : ProtocolClassConstraint::Any;
+    return swift_getExistentialTypeMetadata(classConstraint, nullptr, 0,
+                                            nullptr);
   }
 
   BuiltType createProtocolType(StringRef mangledName, StringRef moduleName,
@@ -305,7 +309,7 @@ class DecodedMetadataBuilder {
 
   BuiltType createGenericTypeParameterType(unsigned depth,
                                            unsigned index) const {
-    // FIXME: Implement.
+    // FIXME: Implement substitution logic here.
     return BuiltType();
   }
 

test/Runtime/demangleToMetadata.swift

@@ -33,6 +33,8 @@ func f2(x: (), y: ()) { }
 
 func f1_variadic(x: ()...) { }
 func f1_inout(x: inout ()) { }
+func f1_shared(x: __shared AnyObject) { }
+func f1_owned(x: __owned AnyObject) { }
 
 func f2_variadic_inout(x: ()..., y: inout ()) { }
 
@@ -59,7 +61,8 @@ DemangleToMetadataTests.test("function types") {
   expectEqual(type(of: f1_inout), _typeByMangledName("yyytzc")!)
 
   // Ownership parameters.
-  // FIXME: Shared/owned
+  expectEqual(type(of: f1_shared), _typeByMangledName("yyyXlhc")!)
+  expectEqual(type(of: f1_owned), _typeByMangledName("yyyXlc")!)
 
   // Mix-and-match.
   expectEqual(type(of: f2_variadic_inout), _typeByMangledName("yyytd_ytztc")!)
@@ -70,5 +73,23 @@ DemangleToMetadataTests.test("metatype types") {
   expectEqual(type(of: type(of: f0)), _typeByMangledName("yycm")!)
 }
 
+func f2_any_anyobject(_: Any, _: AnyObject) { }
+
+DemangleToMetadataTests.test("existential types") {
+  // Any, AnyObject
+  expectEqual(type(of: f2_any_anyobject), _typeByMangledName("yyyp_yXltc")!)
+
+  // FIXME: References to protocols.
+  // FIXME: References to superclass.
+}
+
+DemangleToMetadataTests.test("existential metatype types") {
+  // Any
+  expectEqual(type(of: Any.self), _typeByMangledName("ypm")!)
+
+  // AnyObject
+  expectEqual(type(of: AnyObject.self), _typeByMangledName("yXlm")!)
+}
+
 runAllTests()