Add handling of nested generic callables

Previously tests for these were passing somewhat by accident,
however this commit's parent adds a case which showed that the
handling was missing.

Note that this also relies on the recent fix for nested tuples
which changed the `isinstance` check in `define_generics`.

jedi/inference/gradual/typing.py

@@ -217,9 +217,24 @@ class TypingClassValueWithIndex(_TypingClassMixin, TypingValueWithIndex):
 
         elif annotation_name == 'Callable':
             if len(annotation_generics) == 2:
-                return annotation_generics[1].infer_type_vars(
-                    value_set.execute_annotation(),
-                )
+                if is_class_value:
+                    # This only applies if we are comparing something like
+                    # List[Callable[..., T]] with Iterable[Callable[..., T]].
+                    # First, Jedi tries to match List/Iterable. After that we
+                    # will land here, because is_class_value will be True at
+                    # that point. Obviously we also compare below that both
+                    # sides are `Callable`.
+                    for element in value_set:
+                        element_name = element.py__name__()
+                        if element_name == 'Callable':
+                            merge_type_var_dicts(
+                                type_var_dict,
+                                merge_pairwise_generics(self, element),
+                            )
+                else:
+                    return annotation_generics[1].infer_type_vars(
+                        value_set.execute_annotation(),
+                    )
 
         elif annotation_name == 'Tuple':
             tuple_annotation, = self.execute_annotation()

test/completion/pep0484_generic_mismatches.py

@@ -206,40 +206,36 @@ for a in list_func_t_to_list_t(12):
     a
 
 
-# The following are all actually wrong, however we're mainly testing here that
-# we don't error when processing invalid values, rather than that we get the
-# right output.
-
 x0 = list_func_t_to_list_t(["abc"])[0]
-#? str()
+#?
 x0
 
 x2 = list_func_t_to_list_t([tpl])[0]
-#? tuple()
+#?
 x2
 
 x3 = list_func_t_to_list_t([tpl_typed])[0]
-#? tuple()
+#?
 x3
 
 x4 = list_func_t_to_list_t([collection])[0]
-#? dict()
+#?
 x4
 
 x5 = list_func_t_to_list_t([collection_typed])[0]
-#? dict()
+#?
 x5
 
 x6 = list_func_t_to_list_t([custom_generic])[0]
-#? CustomGeneric()
+#?
 x6
 
 x7 = list_func_t_to_list_t([plain_instance])[0]
-#? PlainClass()
+#?
 x7
 
 for a in list_func_t_to_list_t([12]):
-    #? int()
+    #?
     a