[ASTMangler] Add a special entry point for mangling of distributed thunks

Distributed thunks loose all of the marker protocols associated with their
generic parameters.

Author: xedin

include/swift/AST/ASTMangler.h

@@ -186,6 +186,8 @@ class ASTMangler : public Mangler {
                                              Type GlobalActorBound,
                                              ModuleDecl *Module);
 
+  std::string mangleDistributedThunk(const FuncDecl *thunk);
+
   /// Mangle a completion handler block implementation function, used for importing ObjC
   /// APIs as async.
   ///

lib/AST/ASTMangler.cpp

@@ -3457,3 +3457,11 @@ ASTMangler::mangleOpaqueTypeDescriptorRecord(const OpaqueTypeDecl *decl) {
   appendOperator("Ho");
   return finalize();
 }
+
+std::string ASTMangler::mangleDistributedThunk(const FuncDecl *thunk) {
+  // Marker protocols cannot be checked at runtime, so there is no point
+  // in recording them for distributed thunks.
+  llvm::SaveAndRestore<bool> savedAllowMarkerProtocols(AllowMarkerProtocols,
+                                                       false);
+  return mangleEntity(thunk, SymbolKind::DistributedThunk);
+}