Allow default value for memory view (GH-4315)

Closes https://github.com/cython/cython/issues/4313

Cython/Compiler/ExprNodes.py

@@ -13192,6 +13192,9 @@ class CoercionNode(ExprNode):
             code.annotate((file, line, col-1), AnnotationItem(
                 style='coerce', tag='coerce', text='[%s] to [%s]' % (self.arg.type, self.type)))
 
+    def analyse_types(self, env):
+        return self
+
 
 class CoerceToMemViewSliceNode(CoercionNode):
     """

tests/run/cyfunction_defaults.pyx

@@ -308,6 +308,10 @@ cdef class C:
         pass
     cpdef f8(self, a, list s = [15]):
         pass
+    cpdef f9(self, a, int[:] s = None):
+        pass
+    def f10(self, a, /, b=1, *, int[:] c=None):
+        pass
 
 
 def check_defaults_on_methods_for_introspection():
@@ -336,5 +340,12 @@ def check_defaults_on_methods_for_introspection():
     >>> C.f8.__defaults__
     ([15],)
     >>> C.f8.__kwdefaults__
+    >>> C.f9.__defaults__
+    (None,)
+    >>> C.f9.__kwdefaults__
+    >>> C.f10.__defaults__
+    (1,)
+    >>> C.f10.__kwdefaults__
+    {'c': None}
     """
     pass