class SyntaxTree::MatchVisitor

would match correctly against the AST.
This visitor transforms the AST into a Ruby pattern matching expression that

def comments(node) 

def comments(node)
  return if node.comments.empty?
  q.nest(0) do
    q.text("comments: [")
    q.indent do
      q.breakable("")
      q.seplist(node.comments) { |comment| visit(comment) }
    end
    q.breakable("")
    q.text("]")
  end
end

def field(name, value) 

def field(name, value)
  q.nest(0) do
    q.text(name)
    q.text(": ")
    visit(value)
  end
end

def initialize(q) 

def initialize(q)
  @q = q
end

def list(name, values) 

def list(name, values)
  q.group do
    q.text(name)
    q.text(": [")
    q.indent do
      q.breakable("")
      q.seplist(values) { |value| visit(value) }
    end
    q.breakable("")
    q.text("]")
  end
end

def node(node, _type) 

def node(node, _type)
  items = []
  q.with_target(items) { yield }
  if items.empty?
    q.text(node.class.name)
    return
  end
  q.group do
    q.text(node.class.name)
    q.text("[")
    q.indent do
      q.breakable("")
      q.seplist(items) { |item| q.target << item }
    end
    q.breakable("")
    q.text("]")
  end
end

def pairs(name, values) 

def pairs(name, values)
  q.group do
    q.text(name)
    q.text(": [")
    q.indent do
      q.breakable("")
      q.seplist(values) do |(key, value)|
        q.group do
          q.text("[")
          q.indent do
            q.breakable("")
            visit(key)
            q.text(",")
            q.breakable
            visit(value || nil)
          end
          q.breakable("")
          q.text("]")
        end
      end
    end
    q.breakable("")
    q.text("]")
  end
end

def text(name, value) 

def text(name, value)
  q.nest(0) do
    q.text(name)
    q.text(": ")
    value.pretty_print(q)
  end
end

def visit(node) 

def visit(node)
  case node
  when Node
    super
  when String
    # pp will split up a string on newlines and concat them together using a
    # "+" operator. This breaks the pattern matching expression. So instead
    # we're going to check here for strings and manually put the entire
    # value into the output buffer.
    q.text(node.inspect)
  else
    node.pretty_print(q)
  end
end