Support MetatypeTypeRefs in DemanglingForTypeRef.

Author: adrian-prantl

stdlib/public/Reflection/TypeRef.cpp

@@ -644,7 +644,10 @@ class DemanglingForTypeRef
 
   Demangle::NodePointer visitMetatypeTypeRef(const MetatypeTypeRef *M) {
     auto node = Dem.createNode(Node::Kind::Metatype);
-    assert(!M->wasAbstract() && "not implemented");
+    // FIXME: This is lossy. @objc_metatype is also abstract.
+    auto repr = Dem.createNode(Node::Kind::MetatypeRepresentation,
+                               M->wasAbstract() ? "@thick" : "@thin");
+    node->addChild(repr, Dem);
     node->addChild(visit(M->getInstanceType()), Dem);
     return node;
   }

validation-test/Reflection/existentials.swift

@@ -283,15 +283,15 @@ func getComposition() -> P & Q { return S() }
 reflect(any: getComposition())
 // CHECK-64: Mangled name: $s12existentials1P_AA1Qp
 // CHECK-64: Demangled name: existentials.P & existentials.Q
-// CHECK-32: Mangled name: $s12existentials1PP_AA1QPp
+// CHECK-32: Mangled name: $s12existentials1P_AA1Qp
 // CHECK-32: Demangled name: existentials.P & existentials.Q
 
 // Metatype:
 reflect(any: Int.self)
-// CHECK-64: Mangled name: $sSim
-// CHECK-64: Demangled name: Swift.Int.Type
-// CHECK-32: Mangled name: $sSim
-// CHECK-32: Demangled name: Swift.Int.Type
+// CHECK-64: Mangled name: $sSiXMt
+// CHECK-64: Demangled name: @thin Swift.Int.Type
+// CHECK-32: Mangled name: $sSiXMt
+// CHECK-32: Demangled name: @thin Swift.Int.Type
 
 protocol WithType {
   associatedtype T