Adds support for typing.Literal in type stub generation (#122)

* Adds support for typing.Literal in type stub generation

synchronicity/type_stubs.py

@@ -377,7 +377,11 @@ def _translate_annotation_map_types(
                 return synchronizer._translate_out(type_annotation, interface)
             return type_annotation
 
-        mapped_args = tuple(self._translate_annotation(arg, synchronizer, interface, home_module) for arg in args)
+        if origin == typing.Literal:
+            mapped_args = args
+        else:
+            mapped_args = tuple(self._translate_annotation(arg, synchronizer, interface, home_module) for arg in args)
+
         if interface == Interface.BLOCKING:
             # blocking interface special generic translations:
             if origin == collections.abc.AsyncGenerator:

test/type_stub_test.py

@@ -378,6 +378,14 @@ def foo() -> typing.Callable[..., typing.Any]:
     assert "-> typing.Callable[..., typing.Any]" in src
 
 
+def test_typing_literal():
+    def foo() -> typing.Literal["three", "str"]:
+        ...
+
+    src = _function_source(foo)
+    assert "-> typing.Literal['three', 'str']" in src  # "str" should not be eval:ed in a Literal!
+
+
 def test_overloads_unwrapped_functions():
     with overload_tracking.patched_overload():