Fixed TypeError with a class that inherits from a concrete generic type

Closes #67.

Author: agronholm

CHANGELOG.rst

@@ -1,3 +1,10 @@
+UNRELEASED
+==========
+
+* Fixed ``TypeError`` when formatting annotations from a class that inherits from a concrete
+  generic type (report and tests by bpeake-illuscio)
+
+
 1.5.2
 =====
 

sphinx_autodoc_typehints.py

@@ -119,7 +119,10 @@ def format_annotation(annotation):
         if Generic in annotation_cls.mro():
             params = (getattr(annotation, '__parameters__', None) or
                       getattr(annotation, '__args__', None))
-            extra = '\\[{}]'.format(', '.join(format_annotation(param) for param in params))
+            if params:
+                extra = '\\[{}]'.format(', '.join(format_annotation(param) for param in params))
+            else:
+                extra = ''
 
         return ':py:class:`~{}.{}`{}'.format(annotation.__module__, annotation_cls.__qualname__,
                                              extra)

tests/test_sphinx_autodoc_typehints.py

@@ -21,6 +21,10 @@ class B(Generic[T]):
     pass
 
 
+class C(B[str]):
+    pass
+
+
 class Slotted:
     __slots__ = ()
 
@@ -71,7 +75,8 @@ class Slotted:
     (Pattern[str],                  ':py:class:`~typing.Pattern`\\[:py:class:`str`]'),
     (A,                             ':py:class:`~%s.A`' % __name__),
     (B,                             ':py:class:`~%s.B`\\[\\~T]' % __name__),
-    (B[int],                        ':py:class:`~%s.B`\\[:py:class:`int`]' % __name__)
+    (B[int],                        ':py:class:`~%s.B`\\[:py:class:`int`]' % __name__),
+    (C,                             ':py:class:`~%s.C`' % __name__)
 ])
 def test_format_annotation(annotation, expected_result):
     result = format_annotation(annotation)