class Opal::Nodes::Args::ExtractBlockarg

InlineArgs rewriter creates it to simplify compilation
This node doesn’t exist in the original AST,
^^^^^^
def m(&block); end
Compiles extraction of the block argument

def compile 

def compile
  scope.uses_block!
  scope.add_arg name
  scope.block_name = name
  scope_name  = scope.identity
  yielder     = scope.block_name
  add_temp "$iter = #{scope_name}.$$p"
  add_temp "#{yielder} = $iter || nil"
  line "if ($iter) #{scope_name}.$$p = null;"
end