resolve ForwardRef on widget.annotation (#66)

* resolve ForwardRef on widget.annotation

* return annotation

magicgui/widgets/_bases.py

@@ -53,6 +53,7 @@ def __init__(
     TYPE_CHECKING,
     Any,
     Callable,
+    ForwardRef,
     List,
     MutableSequence,
     Optional,
@@ -244,6 +245,22 @@ def __init__(
         if not visible:
             self.hide()
 
+    @property
+    def annotation(self):
+        """Return type annotation for the parameter represented by the widget.
+
+        ForwardRefs will be resolve when setting the annotation.
+        """
+        return self._annotation
+
+    @annotation.setter
+    def annotation(self, value):
+        if isinstance(value, ForwardRef):
+            from magicgui.type_map import _evaluate_forwardref
+
+            value = _evaluate_forwardref(value)
+        self._annotation = value
+
     @property
     def param_kind(self) -> inspect._ParameterKind:
         """Return :attr:`inspect.Parameter.kind` represented by this widget.

tests/test_widgets.py

@@ -1,4 +1,5 @@
 import pytest
+from tests import MyInt
 
 from magicgui import magicgui, widgets
 
@@ -33,3 +34,13 @@ def test_delete_widget():
     # they disappear from the layout
     with pytest.raises(ValueError):
         container.index(a)
+
+
+def test_widget_resolves_forward_ref():
+    """The annotation on a widget should always be a resolved type."""
+
+    @magicgui
+    def widget(x: "tests.MyInt"):  # type: ignore  # noqa
+        pass
+
+    assert widget.x.annotation is MyInt