Apply traverses a syntax tree recursively, starting with root, and calling pre and post for each node as described below.

Decorations returns information about all the decoration attachment points associated with a node.

Unparen returns e with any enclosing parentheses stripped.

A Cursor describes a node encountered during Apply.

DecorationPoint contains the name of the decoration attachment point and a list of decorations attached there.

An ApplyFunc is invoked by Apply for each node n, even if n is nil, before and/or after the node's children, using a Cursor describing the current node and providing operations on it.