Automatically unquote to offer better support

plum/function.py

@@ -1,12 +1,12 @@
 import inspect
 import logging
-from functools import wraps
 import typing
+from functools import wraps
 
 from .resolvable import Promise
 from .signature import Signature
 from .type import ptype, is_object, VarArgs, deliver_forward_reference
-from .util import check_future_annotations
+from .util import unquote
 
 __all__ = [
     "extract_signature",
@@ -56,6 +56,8 @@ def extract_signature(f, get_type_hints=False):
             function.
     """
     if get_type_hints:
+        # Unquote type hints so that they are resolved to the right types.
+        f.__annotations__ = {k: unquote(v) for k, v in f.__annotations__.items()}
         f.__annotations__ = typing.get_type_hints(f)
 
     # Extract specification.

plum/type.py

@@ -3,7 +3,7 @@
 import logging
 
 from .resolvable import Resolvable, Promise
-from .util import multihash, Comparable
+from .util import multihash, Comparable, unquote
 
 __all__ = [
     "TypeMeta",
@@ -286,9 +286,7 @@ def get_forward_reference(name):
     # The name can possibly be wrapped in an extra set of quotes if the future
     # `annotations` is used and the type is given as a string. E.g., see
     #   https://github.com/wesselb/plum/issues/41
-    # We simply remove any extra quotes.
-    while len(name) >= 2 and name[0] == name[-1] and name[0] in {'"', "'"}:
-        name = name[1:-1]
+    name = unquote(name)
     reference = ForwardReferencedType(name)
     _unresolved_forward_references.append(reference)
     return reference

plum/util.py

@@ -9,6 +9,7 @@
     "get_class",
     "get_context",
     "check_future_annotations",
+    "unquote",
 ]
 
 log = logging.getLogger(__name__)
@@ -129,3 +130,17 @@ def check_future_annotations():
     """
     frame = inspect.currentframe()
     return "annotations" in frame.f_back.f_back.f_globals
+
+
+def unquote(x):
+    """Remove quotes from a string at the outermost level.
+
+    Args:
+        x (str): String to remove quotes from.
+
+    Return:
+        str: `x` but without quotes.
+    """
+    while len(x) >= 2 and x[0] == x[-1] and x[0] in {'"', "'"}:
+        x = x[1:-1]
+    return x

tests/dispatcher/test_future_annotations.py

@@ -14,7 +14,7 @@ def __init__(self, value):
         self.value = value
 
     @dispatch
-    def __add__(self, other: Union[Number, int]) -> Number:
+    def __add__(self, other: Union[Number, int]) -> "Number":
         if isinstance(other, int):
             other_value = other
         else: