[NCGenerics] enable new associated type inference

The experimental-associated-type-inference flag is needed to correctly
build programs when NoncopyableGenerics is enabled.

Author: kavon

lib/Frontend/CompilerInvocation.cpp

@@ -895,8 +895,10 @@ static bool ParseLangArgs(LangOptions &Opts, ArgList &Args,
 
   Opts.enableFeature(Feature::LayoutPrespecialization);
 
-  if (SWIFT_ENABLE_EXPERIMENTAL_NONCOPYABLE_GENERICS)
+  if (SWIFT_ENABLE_EXPERIMENTAL_NONCOPYABLE_GENERICS) {
     Opts.enableFeature(Feature::NoncopyableGenerics);
+    Opts.EnableExperimentalAssociatedTypeInference = true;
+  }
 
   Opts.EnableAppExtensionLibraryRestrictions |= Args.hasArg(OPT_enable_app_extension_library);
   Opts.EnableAppExtensionRestrictions |= Args.hasArg(OPT_enable_app_extension);

stdlib/cmake/modules/SwiftSource.cmake

@@ -609,6 +609,7 @@ function(_compile_swift_files
 
   if(SWIFT_ENABLE_EXPERIMENTAL_NONCOPYABLE_GENERICS)
     list(APPEND swift_flags "-enable-experimental-feature" "NoncopyableGenerics")
+    list(APPEND swift_flags "-Xfrontend" "-enable-experimental-associated-type-inference")
     list(APPEND swift_flags "-Xfrontend" "-disable-round-trip-debug-types") # NOTE: temporary until we fix mangling!
   endif()