Issue #15008: Implement PEP 362 "Signature Objects".

Patch by Yury Selivanov.

1 files changed, 922 insertions, 1 deletions

diff --git a/Lib/test/test_inspect.py b/Lib/test/test_inspect.py
index 802e100..53c947f 100644
--- a/Lib/test/test_inspect.py
+++ b/Lib/test/test_inspect.py
@@ -1173,13 +1173,934 @@ class TestGetGeneratorState(unittest.TestCase):
             self.assertIn(name, str(state))
 
 
+class TestSignatureObject(unittest.TestCase):
+    @staticmethod
+    def signature(func):
+        sig = inspect.signature(func)
+        return (tuple((param.name,
+                       (... if param.default is param.empty else param.default),
+                       (... if param.annotation is param.empty
+                                                        else param.annotation),
+                       str(param.kind).lower())
+                                    for param in sig.parameters.values()),
+                (... if sig.return_annotation is sig.empty
+                                            else sig.return_annotation))
+
+    def test_signature_object(self):
+        S = inspect.Signature
+        P = inspect.Parameter
+
+        self.assertEqual(str(S()), '()')
+
+        def test(po, pk, *args, ko, **kwargs):
+            pass
+        sig = inspect.signature(test)
+        po = sig.parameters['po'].replace(kind=P.POSITIONAL_ONLY)
+        pk = sig.parameters['pk']
+        args = sig.parameters['args']
+        ko = sig.parameters['ko']
+        kwargs = sig.parameters['kwargs']
+
+        S((po, pk, args, ko, kwargs))
+
+        with self.assertRaisesRegexp(ValueError, 'wrong parameter order'):
+            S((pk, po, args, ko, kwargs))
+
+        with self.assertRaisesRegexp(ValueError, 'wrong parameter order'):
+            S((po, args, pk, ko, kwargs))
+
+        with self.assertRaisesRegexp(ValueError, 'wrong parameter order'):
+            S((args, po, pk, ko, kwargs))
+
+        with self.assertRaisesRegexp(ValueError, 'wrong parameter order'):
+            S((po, pk, args, kwargs, ko))
+
+        kwargs2 = kwargs.replace(name='args')
+        with self.assertRaisesRegexp(ValueError, 'duplicate parameter name'):
+            S((po, pk, args, kwargs2, ko))
+
+    def test_signature_immutability(self):
+        def test(a):
+            pass
+        sig = inspect.signature(test)
+
+        with self.assertRaises(AttributeError):
+            sig.foo = 'bar'
+
+        with self.assertRaises(TypeError):
+            sig.parameters['a'] = None
+
+    def test_signature_on_noarg(self):
+        def test():
+            pass
+        self.assertEqual(self.signature(test), ((), ...))
+
+    def test_signature_on_wargs(self):
+        def test(a, b:'foo') -> 123:
+            pass
+        self.assertEqual(self.signature(test),
+                         ((('a', ..., ..., "positional_or_keyword"),
+                           ('b', ..., 'foo', "positional_or_keyword")),
+                          123))
+
+    def test_signature_on_wkwonly(self):
+        def test(*, a:float, b:str) -> int:
+            pass
+        self.assertEqual(self.signature(test),
+                         ((('a', ..., float, "keyword_only"),
+                           ('b', ..., str, "keyword_only")),
+                           int))
+
+    def test_signature_on_complex_args(self):
+        def test(a, b:'foo'=10, *args:'bar', spam:'baz', ham=123, **kwargs:int):
+            pass
+        self.assertEqual(self.signature(test),
+                         ((('a', ..., ..., "positional_or_keyword"),
+                           ('b', 10, 'foo', "positional_or_keyword"),
+                           ('args', ..., 'bar', "var_positional"),
+                           ('spam', ..., 'baz', "keyword_only"),
+                           ('ham', 123, ..., "keyword_only"),
+                           ('kwargs', ..., int, "var_keyword")),
+                          ...))
+
+    def test_signature_on_builtin_function(self):
+        with self.assertRaisesRegexp(ValueError, 'not supported by signature'):
+            inspect.signature(type)
+        with self.assertRaisesRegexp(ValueError, 'not supported by signature'):
+            # support for 'wrapper_descriptor'
+            inspect.signature(type.__call__)
+        with self.assertRaisesRegexp(ValueError, 'not supported by signature'):
+            # support for 'method-wrapper'
+            inspect.signature(min.__call__)
+        with self.assertRaisesRegexp(ValueError,
+                                     'no signature found for builtin function'):
+            # support for 'method-wrapper'
+            inspect.signature(min)
+
+    def test_signature_on_non_function(self):
+        with self.assertRaisesRegexp(TypeError, 'is not a callable object'):
+            inspect.signature(42)
+
+        with self.assertRaisesRegexp(TypeError, 'is not a Python function'):
+            inspect.Signature.from_function(42)
+
+    def test_signature_on_method(self):
+        class Test:
+            def foo(self, arg1, arg2=1) -> int:
+                pass
+
+        meth = Test().foo
+
+        self.assertEqual(self.signature(meth),
+                         ((('arg1', ..., ..., "positional_or_keyword"),
+                           ('arg2', 1, ..., "positional_or_keyword")),
+                          int))
+
+    def test_signature_on_classmethod(self):
+        class Test:
+            @classmethod
+            def foo(cls, arg1, *, arg2=1):
+                pass
+
+        meth = Test().foo
+        self.assertEqual(self.signature(meth),
+                         ((('arg1', ..., ..., "positional_or_keyword"),
+                           ('arg2', 1, ..., "keyword_only")),
+                          ...))
+
+        meth = Test.foo
+        self.assertEqual(self.signature(meth),
+                         ((('arg1', ..., ..., "positional_or_keyword"),
+                           ('arg2', 1, ..., "keyword_only")),
+                          ...))
+
+    def test_signature_on_staticmethod(self):
+        class Test:
+            @staticmethod
+            def foo(cls, *, arg):
+                pass
+
+        meth = Test().foo
+        self.assertEqual(self.signature(meth),
+                         ((('cls', ..., ..., "positional_or_keyword"),
+                           ('arg', ..., ..., "keyword_only")),
+                          ...))
+
+        meth = Test.foo
+        self.assertEqual(self.signature(meth),
+                         ((('cls', ..., ..., "positional_or_keyword"),
+                           ('arg', ..., ..., "keyword_only")),
+                          ...))
+
+    def test_signature_on_partial(self):
+        from functools import partial
+
+        def test():
+            pass
+
+        self.assertEqual(self.signature(partial(test)), ((), ...))
+
+        with self.assertRaisesRegexp(ValueError, "has incorrect arguments"):
+            inspect.signature(partial(test, 1))
+
+        with self.assertRaisesRegexp(ValueError, "has incorrect arguments"):
+            inspect.signature(partial(test, a=1))
+
+        def test(a, b, *, c, d):
+            pass
+
+        self.assertEqual(self.signature(partial(test)),
+                         ((('a', ..., ..., "positional_or_keyword"),
+                           ('b', ..., ..., "positional_or_keyword"),
+                           ('c', ..., ..., "keyword_only"),
+                           ('d', ..., ..., "keyword_only")),
+                          ...))
+
+        self.assertEqual(self.signature(partial(test, 1)),
+                         ((('b', ..., ..., "positional_or_keyword"),
+                           ('c', ..., ..., "keyword_only"),
+                           ('d', ..., ..., "keyword_only")),
+                          ...))
+
+        self.assertEqual(self.signature(partial(test, 1, c=2)),
+                         ((('b', ..., ..., "positional_or_keyword"),
+                           ('c', 2, ..., "keyword_only"),
+                           ('d', ..., ..., "keyword_only")),
+                          ...))
+
+        self.assertEqual(self.signature(partial(test, b=1, c=2)),
+                         ((('a', ..., ..., "positional_or_keyword"),
+                           ('b', 1, ..., "positional_or_keyword"),
+                           ('c', 2, ..., "keyword_only"),
+                           ('d', ..., ..., "keyword_only")),
+                          ...))
+
+        self.assertEqual(self.signature(partial(test, 0, b=1, c=2)),
+                         ((('b', 1, ..., "positional_or_keyword"),
+                           ('c', 2, ..., "keyword_only"),
+                           ('d', ..., ..., "keyword_only"),),
+                          ...))
+
+        def test(a, *args, b, **kwargs):
+            pass
+
+        self.assertEqual(self.signature(partial(test, 1)),
+                         ((('args', ..., ..., "var_positional"),
+                           ('b', ..., ..., "keyword_only"),
+                           ('kwargs', ..., ..., "var_keyword")),
+                          ...))
+
+        self.assertEqual(self.signature(partial(test, 1, 2, 3)),
+                         ((('args', ..., ..., "var_positional"),
+                           ('b', ..., ..., "keyword_only"),
+                           ('kwargs', ..., ..., "var_keyword")),
+                          ...))
+
+
+        self.assertEqual(self.signature(partial(test, 1, 2, 3, test=True)),
+                         ((('args', ..., ..., "var_positional"),
+                           ('b', ..., ..., "keyword_only"),
+                           ('kwargs', ..., ..., "var_keyword")),
+                          ...))
+
+        self.assertEqual(self.signature(partial(test, 1, 2, 3, test=1, b=0)),
+                         ((('args', ..., ..., "var_positional"),
+                           ('b', 0, ..., "keyword_only"),
+                           ('kwargs', ..., ..., "var_keyword")),
+                          ...))
+
+        self.assertEqual(self.signature(partial(test, b=0)),
+                         ((('a', ..., ..., "positional_or_keyword"),
+                           ('args', ..., ..., "var_positional"),
+                           ('b', 0, ..., "keyword_only"),
+                           ('kwargs', ..., ..., "var_keyword")),
+                          ...))
+
+        self.assertEqual(self.signature(partial(test, b=0, test=1)),
+                         ((('a', ..., ..., "positional_or_keyword"),
+                           ('args', ..., ..., "var_positional"),
+                           ('b', 0, ..., "keyword_only"),
+                           ('kwargs', ..., ..., "var_keyword")),
+                          ...))
+
+        def test(a, b, c:int) -> 42:
+            pass
+
+        sig = test.__signature__ = inspect.signature(test)
+
+        self.assertEqual(self.signature(partial(partial(test, 1))),
+                         ((('b', ..., ..., "positional_or_keyword"),
+                           ('c', ..., int, "positional_or_keyword")),
+                          42))
+
+        self.assertEqual(self.signature(partial(partial(test, 1), 2)),
+                         ((('c', ..., int, "positional_or_keyword"),),
+                          42))
+
+        psig = inspect.signature(partial(partial(test, 1), 2))
+
+        def foo(a):
+            return a
+        _foo = partial(partial(foo, a=10), a=20)
+        self.assertEqual(self.signature(_foo),
+                         ((('a', 20, ..., "positional_or_keyword"),),
+                          ...))
+        # check that we don't have any side-effects in signature(),
+        # and the partial object is still functioning
+        self.assertEqual(_foo(), 20)
+
+        def foo(a, b, c):
+            return a, b, c
+        _foo = partial(partial(foo, 1, b=20), b=30)
+        self.assertEqual(self.signature(_foo),
+                         ((('b', 30, ..., "positional_or_keyword"),
+                           ('c', ..., ..., "positional_or_keyword")),
+                          ...))
+        self.assertEqual(_foo(c=10), (1, 30, 10))
+        _foo = partial(_foo, 2) # now 'b' has two values -
+                                # positional and keyword
+        with self.assertRaisesRegexp(ValueError, "has incorrect arguments"):
+            inspect.signature(_foo)
+
+        def foo(a, b, c, *, d):
+            return a, b, c, d
+        _foo = partial(partial(foo, d=20, c=20), b=10, d=30)
+        self.assertEqual(self.signature(_foo),
+                         ((('a', ..., ..., "positional_or_keyword"),
+                           ('b', 10, ..., "positional_or_keyword"),
+                           ('c', 20, ..., "positional_or_keyword"),
+                           ('d', 30, ..., "keyword_only")),
+                          ...))
+        ba = inspect.signature(_foo).bind(a=200, b=11)
+        self.assertEqual(_foo(*ba.args, **ba.kwargs), (200, 11, 20, 30))
+
+        def foo(a=1, b=2, c=3):
+            return a, b, c
+        _foo = partial(foo, a=10, c=13)
+        ba = inspect.signature(_foo).bind(11)
+        self.assertEqual(_foo(*ba.args, **ba.kwargs), (11, 2, 13))
+        ba = inspect.signature(_foo).bind(11, 12)
+        self.assertEqual(_foo(*ba.args, **ba.kwargs), (11, 12, 13))
+        ba = inspect.signature(_foo).bind(11, b=12)
+        self.assertEqual(_foo(*ba.args, **ba.kwargs), (11, 12, 13))
+        ba = inspect.signature(_foo).bind(b=12)
+        self.assertEqual(_foo(*ba.args, **ba.kwargs), (10, 12, 13))
+        _foo = partial(_foo, b=10)
+        ba = inspect.signature(_foo).bind(12, 14)
+        self.assertEqual(_foo(*ba.args, **ba.kwargs), (12, 14, 13))
+
+    def test_signature_on_decorated(self):
+        import functools
+
+        def decorator(func):
+            @functools.wraps(func)
+            def wrapper(*args, **kwargs) -> int:
+                return func(*args, **kwargs)
+            return wrapper
+
+        class Foo:
+            @decorator
+            def bar(self, a, b):
+                pass
+
+        self.assertEqual(self.signature(Foo.bar),
+                         ((('self', ..., ..., "positional_or_keyword"),
+                           ('a', ..., ..., "positional_or_keyword"),
+                           ('b', ..., ..., "positional_or_keyword")),
+                          ...))
+
+        self.assertEqual(self.signature(Foo().bar),
+                         ((('a', ..., ..., "positional_or_keyword"),
+                           ('b', ..., ..., "positional_or_keyword")),
+                          ...))
+
+        # Test that we handle method wrappers correctly
+        def decorator(func):
+            @functools.wraps(func)
+            def wrapper(*args, **kwargs) -> int:
+                return func(42, *args, **kwargs)
+            sig = inspect.signature(func)
+            new_params = tuple(sig.parameters.values())[1:]
+            wrapper.__signature__ = sig.replace(parameters=new_params)
+            return wrapper
+
+        class Foo:
+            @decorator
+            def __call__(self, a, b):
+                pass
+
+        self.assertEqual(self.signature(Foo.__call__),
+                         ((('a', ..., ..., "positional_or_keyword"),
+                           ('b', ..., ..., "positional_or_keyword")),
+                          ...))
+
+        self.assertEqual(self.signature(Foo().__call__),
+                         ((('b', ..., ..., "positional_or_keyword"),),
+                          ...))
+
+    def test_signature_on_class(self):
+        class C:
+            def __init__(self, a):
+                pass
+
+        self.assertEqual(self.signature(C),
+                         ((('a', ..., ..., "positional_or_keyword"),),
+                          ...))
+
+        class CM(type):
+            def __call__(cls, a):
+                pass
+        class C(metaclass=CM):
+            def __init__(self, b):
+                pass
+
+        self.assertEqual(self.signature(C),
+                         ((('a', ..., ..., "positional_or_keyword"),),
+                          ...))
+
+        class CM(type):
+            def __new__(mcls, name, bases, dct, *, foo=1):
+                return super().__new__(mcls, name, bases, dct)
+        class C(metaclass=CM):
+            def __init__(self, b):
+                pass
+
+        self.assertEqual(self.signature(C),
+                         ((('b', ..., ..., "positional_or_keyword"),),
+                          ...))
+
+        self.assertEqual(self.signature(CM),
+                         ((('name', ..., ..., "positional_or_keyword"),
+                           ('bases', ..., ..., "positional_or_keyword"),
+                           ('dct', ..., ..., "positional_or_keyword"),
+                           ('foo', 1, ..., "keyword_only")),
+                          ...))
+
+        class CMM(type):
+            def __new__(mcls, name, bases, dct, *, foo=1):
+                return super().__new__(mcls, name, bases, dct)
+            def __call__(cls, nm, bs, dt):
+                return type(nm, bs, dt)
+        class CM(type, metaclass=CMM):
+            def __new__(mcls, name, bases, dct, *, bar=2):
+                return super().__new__(mcls, name, bases, dct)
+        class C(metaclass=CM):
+            def __init__(self, b):
+                pass
+
+        self.assertEqual(self.signature(CMM),
+                         ((('name', ..., ..., "positional_or_keyword"),
+                           ('bases', ..., ..., "positional_or_keyword"),
+                           ('dct', ..., ..., "positional_or_keyword"),
+                           ('foo', 1, ..., "keyword_only")),
+                          ...))
+
+        self.assertEqual(self.signature(CM),
+                         ((('nm', ..., ..., "positional_or_keyword"),
+                           ('bs', ..., ..., "positional_or_keyword"),
+                           ('dt', ..., ..., "positional_or_keyword")),
+                          ...))
+
+        self.assertEqual(self.signature(C),
+                         ((('b', ..., ..., "positional_or_keyword"),),
+                          ...))
+
+        class CM(type):
+            def __init__(cls, name, bases, dct, *, bar=2):
+                return super().__init__(name, bases, dct)
+        class C(metaclass=CM):
+            def __init__(self, b):
+                pass
+
+        self.assertEqual(self.signature(CM),
+                         ((('name', ..., ..., "positional_or_keyword"),
+                           ('bases', ..., ..., "positional_or_keyword"),
+                           ('dct', ..., ..., "positional_or_keyword"),
+                           ('bar', 2, ..., "keyword_only")),
+                          ...))
+
+    def test_signature_on_callable_objects(self):
+        class Foo:
+            def __call__(self, a):
+                pass
+
+        self.assertEqual(self.signature(Foo()),
+                         ((('a', ..., ..., "positional_or_keyword"),),
+                          ...))
+
+        class Spam:
+            pass
+        with self.assertRaisesRegexp(TypeError, "is not a callable object"):
+            inspect.signature(Spam())
+
+        class Bar(Spam, Foo):
+            pass
+
+        self.assertEqual(self.signature(Bar()),
+                         ((('a', ..., ..., "positional_or_keyword"),),
+                          ...))
+
+        class ToFail:
+            __call__ = type
+        with self.assertRaisesRegexp(ValueError, "not supported by signature"):
+            inspect.signature(ToFail())
+
+
+        class Wrapped:
+            pass
+        Wrapped.__wrapped__ = lambda a: None
+        self.assertEqual(self.signature(Wrapped),
+                         ((('a', ..., ..., "positional_or_keyword"),),
+                          ...))
+
+    def test_signature_on_lambdas(self):
+        self.assertEqual(self.signature((lambda a=10: a)),
+                         ((('a', 10, ..., "positional_or_keyword"),),
+                          ...))
+
+    def test_signature_equality(self):
+        def foo(a, *, b:int) -> float: pass
+        self.assertNotEqual(inspect.signature(foo), 42)
+
+        def bar(a, *, b:int) -> float: pass
+        self.assertEqual(inspect.signature(foo), inspect.signature(bar))
+
+        def bar(a, *, b:int) -> int: pass
+        self.assertNotEqual(inspect.signature(foo), inspect.signature(bar))
+
+        def bar(a, *, b:int): pass
+        self.assertNotEqual(inspect.signature(foo), inspect.signature(bar))
+
+        def bar(a, *, b:int=42) -> float: pass
+        self.assertNotEqual(inspect.signature(foo), inspect.signature(bar))
+
+        def bar(a, *, c) -> float: pass
+        self.assertNotEqual(inspect.signature(foo), inspect.signature(bar))
+
+        def bar(a, b:int) -> float: pass
+        self.assertNotEqual(inspect.signature(foo), inspect.signature(bar))
+        def spam(b:int, a) -> float: pass
+        self.assertNotEqual(inspect.signature(spam), inspect.signature(bar))
+
+        def foo(*, a, b, c): pass
+        def bar(*, c, b, a): pass
+        self.assertEqual(inspect.signature(foo), inspect.signature(bar))
+
+        def foo(*, a=1, b, c): pass
+        def bar(*, c, b, a=1): pass
+        self.assertEqual(inspect.signature(foo), inspect.signature(bar))
+
+        def foo(pos, *, a=1, b, c): pass
+        def bar(pos, *, c, b, a=1): pass
+        self.assertEqual(inspect.signature(foo), inspect.signature(bar))
+
+        def foo(pos, *, a, b, c): pass
+        def bar(pos, *, c, b, a=1): pass
+        self.assertNotEqual(inspect.signature(foo), inspect.signature(bar))
+
+        def foo(pos, *args, a=42, b, c, **kwargs:int): pass
+        def bar(pos, *args, c, b, a=42, **kwargs:int): pass
+        self.assertEqual(inspect.signature(foo), inspect.signature(bar))
+
+    def test_signature_unhashable(self):
+        def foo(a): pass
+        sig = inspect.signature(foo)
+        with self.assertRaisesRegexp(TypeError, 'unhashable type'):
+            hash(sig)
+
+    def test_signature_str(self):
+        def foo(a:int=1, *, b, c=None, **kwargs) -> 42:
+            pass
+        self.assertEqual(str(inspect.signature(foo)),
+                         '(a:int=1, *, b, c=None, **kwargs) -> 42')
+
+        def foo(a:int=1, *args, b, c=None, **kwargs) -> 42:
+            pass
+        self.assertEqual(str(inspect.signature(foo)),
+                         '(a:int=1, *args, b, c=None, **kwargs) -> 42')
+
+        def foo():
+            pass
+        self.assertEqual(str(inspect.signature(foo)), '()')
+
+    def test_signature_str_positional_only(self):
+        P = inspect.Parameter
+
+        def test(a_po, *, b, **kwargs):
+            return a_po, kwargs
+
+        sig = inspect.signature(test)
+        new_params = list(sig.parameters.values())
+        new_params[0] = new_params[0].replace(kind=P.POSITIONAL_ONLY)
+        test.__signature__ = sig.replace(parameters=new_params)
+
+        self.assertEqual(str(inspect.signature(test)),
+                         '(<a_po>, *, b, **kwargs)')
+
+        sig = inspect.signature(test)
+        new_params = list(sig.parameters.values())
+        new_params[0] = new_params[0].replace(name=None)
+        test.__signature__ = sig.replace(parameters=new_params)
+        self.assertEqual(str(inspect.signature(test)),
+                         '(<0>, *, b, **kwargs)')
+
+    def test_signature_replace_anno(self):
+        def test() -> 42:
+            pass
+
+        sig = inspect.signature(test)
+        sig = sig.replace(return_annotation=None)
+        self.assertIs(sig.return_annotation, None)
+        sig = sig.replace(return_annotation=sig.empty)
+        self.assertIs(sig.return_annotation, sig.empty)
+        sig = sig.replace(return_annotation=42)
+        self.assertEqual(sig.return_annotation, 42)
+        self.assertEqual(sig, inspect.signature(test))
+
+
+class TestParameterObject(unittest.TestCase):
+    def test_signature_parameter_kinds(self):
+        P = inspect.Parameter
+        self.assertTrue(P.POSITIONAL_ONLY < P.POSITIONAL_OR_KEYWORD < \
+                        P.VAR_POSITIONAL < P.KEYWORD_ONLY < P.VAR_KEYWORD)
+
+        self.assertEqual(str(P.POSITIONAL_ONLY), 'POSITIONAL_ONLY')
+        self.assertTrue('POSITIONAL_ONLY' in repr(P.POSITIONAL_ONLY))
+
+    def test_signature_parameter_object(self):
+        p = inspect.Parameter('foo', default=10,
+                              kind=inspect.Parameter.POSITIONAL_ONLY)
+        self.assertEqual(p.name, 'foo')
+        self.assertEqual(p.default, 10)
+        self.assertIs(p.annotation, p.empty)
+        self.assertEqual(p.kind, inspect.Parameter.POSITIONAL_ONLY)
+
+        with self.assertRaisesRegexp(ValueError, 'invalid value'):
+            inspect.Parameter('foo', default=10, kind='123')
+
+        with self.assertRaisesRegexp(ValueError, 'not a valid parameter name'):
+            inspect.Parameter('1', kind=inspect.Parameter.VAR_KEYWORD)
+
+        with self.assertRaisesRegexp(ValueError,
+                                     'non-positional-only parameter'):
+            inspect.Parameter(None, kind=inspect.Parameter.VAR_KEYWORD)
+
+        with self.assertRaisesRegexp(ValueError, 'cannot have default values'):
+            inspect.Parameter('a', default=42,
+                              kind=inspect.Parameter.VAR_KEYWORD)
+
+        with self.assertRaisesRegexp(ValueError, 'cannot have default values'):
+            inspect.Parameter('a', default=42,
+                              kind=inspect.Parameter.VAR_POSITIONAL)
+
+        p = inspect.Parameter('a', default=42,
+                              kind=inspect.Parameter.POSITIONAL_OR_KEYWORD)
+        with self.assertRaisesRegexp(ValueError, 'cannot have default values'):
+            p.replace(kind=inspect.Parameter.VAR_POSITIONAL)
+
+        self.assertTrue(repr(p).startswith('<Parameter'))
+
+    def test_signature_parameter_equality(self):
+        P = inspect.Parameter
+        p = P('foo', default=42, kind=inspect.Parameter.KEYWORD_ONLY)
+
+        self.assertEqual(p, p)
+        self.assertNotEqual(p, 42)
+
+        self.assertEqual(p, P('foo', default=42,
+                              kind=inspect.Parameter.KEYWORD_ONLY))
+
+    def test_signature_parameter_unhashable(self):
+        p = inspect.Parameter('foo', default=42,
+                              kind=inspect.Parameter.KEYWORD_ONLY)
+
+        with self.assertRaisesRegexp(TypeError, 'unhashable type'):
+            hash(p)
+
+    def test_signature_parameter_replace(self):
+        p = inspect.Parameter('foo', default=42,
+                              kind=inspect.Parameter.KEYWORD_ONLY)
+
+        self.assertIsNot(p, p.replace())
+        self.assertEqual(p, p.replace())
+
+        p2 = p.replace(annotation=1)
+        self.assertEqual(p2.annotation, 1)
+        p2 = p2.replace(annotation=p2.empty)
+        self.assertEqual(p, p2)
+
+        p2 = p2.replace(name='bar')
+        self.assertEqual(p2.name, 'bar')
+        self.assertNotEqual(p2, p)
+
+        with self.assertRaisesRegexp(ValueError, 'not a valid parameter name'):
+            p2 = p2.replace(name=p2.empty)
+
+        p2 = p2.replace(name='foo', default=None)
+        self.assertIs(p2.default, None)
+        self.assertNotEqual(p2, p)
+
+        p2 = p2.replace(name='foo', default=p2.empty)
+        self.assertIs(p2.default, p2.empty)
+
+
+        p2 = p2.replace(default=42, kind=p2.POSITIONAL_OR_KEYWORD)
+        self.assertEqual(p2.kind, p2.POSITIONAL_OR_KEYWORD)
+        self.assertNotEqual(p2, p)
+
+        with self.assertRaisesRegexp(ValueError, 'invalid value for'):
+            p2 = p2.replace(kind=p2.empty)
+
+        p2 = p2.replace(kind=p2.KEYWORD_ONLY)
+        self.assertEqual(p2, p)
+
+    def test_signature_parameter_positional_only(self):
+        p = inspect.Parameter(None, kind=inspect.Parameter.POSITIONAL_ONLY)
+        self.assertEqual(str(p), '<>')
+
+        p = p.replace(name='1')
+        self.assertEqual(str(p), '<1>')
+
+    def test_signature_parameter_immutability(self):
+        p = inspect.Parameter(None, kind=inspect.Parameter.POSITIONAL_ONLY)
+
+        with self.assertRaises(AttributeError):
+            p.foo = 'bar'
+
+        with self.assertRaises(AttributeError):
+            p.kind = 123
+
+
+class TestSignatureBind(unittest.TestCase):
+    @staticmethod
+    def call(func, *args, **kwargs):
+        sig = inspect.signature(func)
+        ba = sig.bind(*args, **kwargs)
+        return func(*ba.args, **ba.kwargs)
+
+    def test_signature_bind_empty(self):
+        def test():
+            return 42
+
+        self.assertEqual(self.call(test), 42)
+        with self.assertRaisesRegexp(TypeError, 'too many positional arguments'):
+            self.call(test, 1)
+        with self.assertRaisesRegexp(TypeError, 'too many positional arguments'):
+            self.call(test, 1, spam=10)
+        with self.assertRaisesRegexp(TypeError, 'too many keyword arguments'):
+            self.call(test, spam=1)
+
+    def test_signature_bind_var(self):
+        def test(*args, **kwargs):
+            return args, kwargs
+
+        self.assertEqual(self.call(test), ((), {}))
+        self.assertEqual(self.call(test, 1), ((1,), {}))
+        self.assertEqual(self.call(test, 1, 2), ((1, 2), {}))
+        self.assertEqual(self.call(test, foo='bar'), ((), {'foo': 'bar'}))
+        self.assertEqual(self.call(test, 1, foo='bar'), ((1,), {'foo': 'bar'}))
+        self.assertEqual(self.call(test, args=10), ((), {'args': 10}))
+        self.assertEqual(self.call(test, 1, 2, foo='bar'),
+                         ((1, 2), {'foo': 'bar'}))
+
+    def test_signature_bind_just_args(self):
+        def test(a, b, c):
+            return a, b, c
+
+        self.assertEqual(self.call(test, 1, 2, 3), (1, 2, 3))
+
+        with self.assertRaisesRegexp(TypeError, 'too many positional arguments'):
+            self.call(test, 1, 2, 3, 4)
+
+        with self.assertRaisesRegexp(TypeError, "'b' parameter lacking default"):
+            self.call(test, 1)
+
+        with self.assertRaisesRegexp(TypeError, "'a' parameter lacking default"):
+            self.call(test)
+
+        def test(a, b, c=10):
+            return a, b, c
+        self.assertEqual(self.call(test, 1, 2, 3), (1, 2, 3))
+        self.assertEqual(self.call(test, 1, 2), (1, 2, 10))
+
+        def test(a=1, b=2, c=3):
+            return a, b, c
+        self.assertEqual(self.call(test, a=10, c=13), (10, 2, 13))
+        self.assertEqual(self.call(test, a=10), (10, 2, 3))
+        self.assertEqual(self.call(test, b=10), (1, 10, 3))
+
+    def test_signature_bind_varargs_order(self):
+        def test(*args):
+            return args
+
+        self.assertEqual(self.call(test), ())
+        self.assertEqual(self.call(test, 1, 2, 3), (1, 2, 3))
+
+    def test_signature_bind_args_and_varargs(self):
+        def test(a, b, c=3, *args):
+            return a, b, c, args
+
+        self.assertEqual(self.call(test, 1, 2, 3, 4, 5), (1, 2, 3, (4, 5)))
+        self.assertEqual(self.call(test, 1, 2), (1, 2, 3, ()))
+        self.assertEqual(self.call(test, b=1, a=2), (2, 1, 3, ()))
+        self.assertEqual(self.call(test, 1, b=2), (1, 2, 3, ()))
+
+        with self.assertRaisesRegexp(TypeError,
+                                     "multiple values for argument 'c'"):
+            self.call(test, 1, 2, 3, c=4)
+
+    def test_signature_bind_just_kwargs(self):
+        def test(**kwargs):
+            return kwargs
+
+        self.assertEqual(self.call(test), {})
+        self.assertEqual(self.call(test, foo='bar', spam='ham'),
+                         {'foo': 'bar', 'spam': 'ham'})
+
+    def test_signature_bind_args_and_kwargs(self):
+        def test(a, b, c=3, **kwargs):
+            return a, b, c, kwargs
+
+        self.assertEqual(self.call(test, 1, 2), (1, 2, 3, {}))
+        self.assertEqual(self.call(test, 1, 2, foo='bar', spam='ham'),
+                         (1, 2, 3, {'foo': 'bar', 'spam': 'ham'}))
+        self.assertEqual(self.call(test, b=2, a=1, foo='bar', spam='ham'),
+                         (1, 2, 3, {'foo': 'bar', 'spam': 'ham'}))
+        self.assertEqual(self.call(test, a=1, b=2, foo='bar', spam='ham'),
+                         (1, 2, 3, {'foo': 'bar', 'spam': 'ham'}))
+        self.assertEqual(self.call(test, 1, b=2, foo='bar', spam='ham'),
+                         (1, 2, 3, {'foo': 'bar', 'spam': 'ham'}))
+        self.assertEqual(self.call(test, 1, b=2, c=4, foo='bar', spam='ham'),
+                         (1, 2, 4, {'foo': 'bar', 'spam': 'ham'}))
+        self.assertEqual(self.call(test, 1, 2, 4, foo='bar'),
+                         (1, 2, 4, {'foo': 'bar'}))
+        self.assertEqual(self.call(test, c=5, a=4, b=3),
+                         (4, 3, 5, {}))
+
+    def test_signature_bind_kwonly(self):
+        def test(*, foo):
+            return foo
+        with self.assertRaisesRegexp(TypeError,
+                                     'too many positional arguments'):
+            self.call(test, 1)
+        self.assertEqual(self.call(test, foo=1), 1)
+
+        def test(a, *, foo=1, bar):
+            return foo
+        with self.assertRaisesRegexp(TypeError,
+                                     "'bar' parameter lacking default value"):
+            self.call(test, 1)
+
+        def test(foo, *, bar):
+            return foo, bar
+        self.assertEqual(self.call(test, 1, bar=2), (1, 2))
+        self.assertEqual(self.call(test, bar=2, foo=1), (1, 2))
+
+        with self.assertRaisesRegexp(TypeError,
+                                     'too many keyword arguments'):
+            self.call(test, bar=2, foo=1, spam=10)
+
+        with self.assertRaisesRegexp(TypeError,
+                                     'too many positional arguments'):
+            self.call(test, 1, 2)
+
+        with self.assertRaisesRegexp(TypeError,
+                                     'too many positional arguments'):
+            self.call(test, 1, 2, bar=2)
+
+        with self.assertRaisesRegexp(TypeError,
+                                     'too many keyword arguments'):
+            self.call(test, 1, bar=2, spam='ham')
+
+        with self.assertRaisesRegexp(TypeError,
+                                     "'bar' parameter lacking default value"):
+            self.call(test, 1)
+
+        def test(foo, *, bar, **bin):
+            return foo, bar, bin
+        self.assertEqual(self.call(test, 1, bar=2), (1, 2, {}))
+        self.assertEqual(self.call(test, foo=1, bar=2), (1, 2, {}))
+        self.assertEqual(self.call(test, 1, bar=2, spam='ham'),
+                         (1, 2, {'spam': 'ham'}))
+        self.assertEqual(self.call(test, spam='ham', foo=1, bar=2),
+                         (1, 2, {'spam': 'ham'}))
+        with self.assertRaisesRegexp(TypeError,
+                                     "'foo' parameter lacking default value"):
+            self.call(test, spam='ham', bar=2)
+        self.assertEqual(self.call(test, 1, bar=2, bin=1, spam=10),
+                         (1, 2, {'bin': 1, 'spam': 10}))
+
+    def test_signature_bind_arguments(self):
+        def test(a, *args, b, z=100, **kwargs):
+            pass
+        sig = inspect.signature(test)
+        ba = sig.bind(10, 20, b=30, c=40, args=50, kwargs=60)
+        # we won't have 'z' argument in the bound arguments object, as we didn't
+        # pass it to the 'bind'
+        self.assertEqual(tuple(ba.arguments.items()),
+                         (('a', 10), ('args', (20,)), ('b', 30),
+                          ('kwargs', {'c': 40, 'args': 50, 'kwargs': 60})))
+        self.assertEqual(ba.kwargs,
+                         {'b': 30, 'c': 40, 'args': 50, 'kwargs': 60})
+        self.assertEqual(ba.args, (10, 20))
+
+    def test_signature_bind_positional_only(self):
+        P = inspect.Parameter
+
+        def test(a_po, b_po, c_po=3, foo=42, *, bar=50, **kwargs):
+            return a_po, b_po, c_po, foo, bar, kwargs
+
+        sig = inspect.signature(test)
+        new_params = collections.OrderedDict(tuple(sig.parameters.items()))
+        for name in ('a_po', 'b_po', 'c_po'):
+            new_params[name] = new_params[name].replace(kind=P.POSITIONAL_ONLY)
+        new_sig = sig.replace(parameters=new_params.values())
+        test.__signature__ = new_sig
+
+        self.assertEqual(self.call(test, 1, 2, 4, 5, bar=6),
+                         (1, 2, 4, 5, 6, {}))
+
+        with self.assertRaisesRegexp(TypeError, "parameter is positional only"):
+            self.call(test, 1, 2, c_po=4)
+
+        with self.assertRaisesRegexp(TypeError, "parameter is positional only"):
+            self.call(test, a_po=1, b_po=2)
+
+
+class TestBoundArguments(unittest.TestCase):
+    def test_signature_bound_arguments_unhashable(self):
+        def foo(a): pass
+        ba = inspect.signature(foo).bind(1)
+
+        with self.assertRaisesRegexp(TypeError, 'unhashable type'):
+            hash(ba)
+
+    def test_signature_bound_arguments_equality(self):
+        def foo(a): pass
+        ba = inspect.signature(foo).bind(1)
+        self.assertEqual(ba, ba)
+
+        ba2 = inspect.signature(foo).bind(1)
+        self.assertEqual(ba, ba2)
+
+        ba3 = inspect.signature(foo).bind(2)
+        self.assertNotEqual(ba, ba3)
+        ba3.arguments['a'] = 1
+        self.assertEqual(ba, ba3)
+
+        def bar(b): pass
+        ba4 = inspect.signature(bar).bind(1)
+        self.assertNotEqual(ba, ba4)
+
+
 def test_main():
     run_unittest(
         TestDecorators, TestRetrievingSourceCode, TestOneliners, TestBuggyCases,
         TestInterpreterStack, TestClassesAndFunctions, TestPredicates,
         TestGetcallargsFunctions, TestGetcallargsMethods,
         TestGetcallargsUnboundMethods, TestGetattrStatic, TestGetGeneratorState,
-        TestNoEOL
+        TestNoEOL, TestSignatureObject, TestSignatureBind, TestParameterObject,
+        TestBoundArguments
     )
 
 if __name__ == "__main__":