vendored parslet, deemed stable enough and better without dependency

lib/parslet/pattern/binding.rb

@@ -0,0 +1,49 @@
+
+# Used internally for representing a bind placeholder in a Parslet::Transform
+# pattern. This is the superclass for all bindings. 
+#
+# It defines the most permissive kind of bind, the one that matches any subtree
+# whatever it looks like. 
+#
+class Parslet::Pattern::SubtreeBind < Struct.new(:symbol)
+  def variable_name
+    symbol
+  end
+  
+  def inspect
+    "#{bind_type_name}(#{symbol.inspect})"
+  end
+  
+  def can_bind?(subtree)
+    true
+  end
+
+private 
+  def bind_type_name 
+    if md=self.class.name.match(/(\w+)Bind/)
+      md.captures.first.downcase
+    else
+      # This path should never be used, but since this is for inspection only, 
+      # let's not raise.
+      'unknown_bind'
+    end
+  end
+end
+
+# Binds a symbol to a simple subtree, one that is not either a sequence of
+# elements or a collection of attributes. 
+#
+class Parslet::Pattern::SimpleBind < Parslet::Pattern::SubtreeBind
+  def can_bind?(subtree)
+    not [Hash, Array].include?(subtree.class)
+  end
+end
+
+# Binds a symbol to a sequence of simple leafs ([element1, element2, ...])
+#
+class Parslet::Pattern::SequenceBind < Parslet::Pattern::SubtreeBind
+  def can_bind?(subtree)
+    subtree.kind_of?(Array) &&
+      (not subtree.any? { |el| [Hash, Array].include?(el.class) })
+  end
+end