Add a mangling for completion block implementation functions.

Author: jckarter

docs/ABI/Mangling.rst

@@ -218,6 +218,8 @@ types where the metadata itself has unknown layout.)
   global ::= global 'Tm'                 // merged function
   global ::= entity                      // some identifiable thing
   global ::= from-type to-type generic-signature? 'TR'  // reabstraction thunk
+  global ::= from-type to-type generic-signature? 'TR'  // reabstraction thunk
+  global ::= impl-function-type 'Tz'     // objc-to-swift-async completion handler block implementation
   global ::= from-type to-type self-type generic-signature? 'Ty'  // reabstraction thunk with dynamic 'Self' capture
   global ::= from-type to-type generic-signature? 'Tr'  // obsolete mangling for reabstraction thunk
   global ::= entity generic-signature? type type* 'TK' // key path getter

include/swift/Demangling/DemangleNodes.def

@@ -159,6 +159,7 @@ CONTEXT_NODE(NativePinningMutableAddressor)
 NODE(NominalTypeDescriptor)
 NODE(NonObjCAttribute)
 NODE(Number)
+NODE(ObjCAsyncCompletionHandlerImpl)
 NODE(ObjCAttribute)
 NODE(ObjCBlock)
 NODE(EscapingObjCBlock)

lib/Demangling/Demangler.cpp

@@ -2244,7 +2244,7 @@ NodePointer Demangler::popProtocolConformance() {
   return Conf;
 }
 
-NodePointer Demangler::demangleThunkOrSpecialization() {
+  NodePointer Demangler::demangleThunkOrSpecialization() {
   switch (char c = nextChar()) {
     case 'c': return createWithChild(Node::Kind::CurryThunk, popNode(isEntity));
     case 'j': return createWithChild(Node::Kind::DispatchThunk, popNode(isEntity));
@@ -2263,6 +2263,10 @@ NodePointer Demangler::demangleThunkOrSpecialization() {
       NodePointer type = popNode(Node::Kind::Type);
       return createWithChild(Node::Kind::CoroutineContinuationPrototype, type);
     }
+    case 'z': {
+      NodePointer implType = popNode(Node::Kind::ImplFunctionType);
+      return createWithChild(Node::Kind::ObjCAsyncCompletionHandlerImpl, implType);
+    }
     case 'V': {
       NodePointer Base = popNode(isEntity);
       NodePointer Derived = popNode(isEntity);

lib/Demangling/NodePrinter.cpp

@@ -439,6 +439,7 @@ class NodePrinter {
     case Node::Kind::NominalTypeDescriptor:
     case Node::Kind::NonObjCAttribute:
     case Node::Kind::Number:
+    case Node::Kind::ObjCAsyncCompletionHandlerImpl:
     case Node::Kind::ObjCAttribute:
     case Node::Kind::ObjCBlock:
     case Node::Kind::ObjCMetadataUpdateFunction:
@@ -2532,6 +2533,10 @@ NodePointer NodePrinter::print(NodePointer Node, bool asPrefixContext) {
       Printer << ')';
     }
     return nullptr;
+  case Node::Kind::ObjCAsyncCompletionHandlerImpl:
+    Printer << "@objc completion handler block implementation for ";
+    print(Node->getChild(0));
+    return nullptr;
   }
   printer_unreachable("bad node kind!");
 }

lib/Demangling/OldRemangler.cpp

@@ -2166,6 +2166,9 @@ void Remangler::mangleGlobalVariableOnceFunction(Node *node) {
 void Remangler::mangleGlobalVariableOnceDeclList(Node *node) {
   unreachable("unsupported");
 }
+void Remangler::mangleObjCAsyncCompletionHandlerImpl(Node *node) {
+  unreachable("unsupported");
+}
 
 void Remangler::mangleCanonicalSpecializedGenericMetaclass(Node *node) {
   Buffer << "MM";

lib/Demangling/Remangler.cpp

@@ -805,6 +805,11 @@ void Remangler::mangleCoroutineContinuationPrototype(Node *node) {
   Buffer << "TC";
 }
 
+void Remangler::mangleObjCAsyncCompletionHandlerImpl(Node *node) {
+  mangleChildNodes(node);
+  Buffer << "Tz";
+}
+
 void Remangler::mangleDeallocator(Node *node) {
   mangleChildNodes(node);
   Buffer << "fD";