Make nesting of *args/**kwargs possible to understand.

jedi/evaluate/signature.py

@@ -179,13 +179,16 @@ def _process_params(param_names, star_count=3):  # default means both * and **
     for p in param_names:
         if star_count == 1 and p.maybe_positional_argument():
             if p.get_kind() == Parameter.VAR_POSITIONAL:
-                yield p
+                for param_names in _iter_nodes_for_param(p, star_count=1):
+                    for p in param_names:
+                        yield p
+                    break
+                else:
+                    yield p
             else:
                 yield ParamNameFixedKind(p, Parameter.POSITIONAL_ONLY)
         elif star_count == 2 and p.maybe_keyword_argument():
             if p.get_kind() == Parameter.VAR_KEYWORD:
-                yield p
-                continue
                 itered = list(_iter_nodes_for_param(p, star_count=2))
                 if not itered:
                     # We were not able to resolve kwargs.

test/test_evaluate/test_signature.py

@@ -104,6 +104,11 @@ def test_tree_signature(Script, environment, code, expected):
 
         ('combined_lot_of_args(kw, simple4)', '*, b'),
         ('combined_lot_of_args(simple4, kw)', '*, b, c, **kwargs'),
+
+        ('combined_redirect(combined_redirect(simple2, simple4), combined_redirect(kw, simple5))',
+         'x, /, *, y'),
+        ('combined_redirect(combined_redirect(simple4, simple2), combined_redirect(simple5, kw))',
+         'a, b, x: int, /, *, a, b, c, **kwargs'),
     ]
 )
 def test_nested_signatures(Script, environment, combination, expected):
@@ -112,6 +117,7 @@ def test_nested_signatures(Script, environment, combination, expected):
         def simple2(x): ...
         def simple3(a, x: int): ...
         def simple4(a, b, x: int): ...
+        def simple5(y): ...
         def a(a, b, *args): ...
         def kw(a, b, *, c, **kwargs): ...
         def akw(a, b, *args, **kwargs): ...