Set slicing type using continuous information if provided.

        Also visit subnodes as they may contains relevant typing information.

def visit_Slice(self, node):
        """
        Set slicing type using continuous information if provided.

        Also visit subnodes as they may contains relevant typing information.
        """
        self.generic_visit(node)
        if node.step is None or (isinstance(node.step, ast.Num) and
                                 node.step.n == 1):
            self.result[node] = self.builder.NamedType(
                'pythonic::types::contiguous_slice')
        else:
            self.result[node] = self.builder.NamedType(
                'pythonic::types::slice')