Blocks become of class Proc in a useful context ;)

blocks_are_procs.rb

class Proc
  def foobar
    puts "...method on Proc!"
  end  
end  

def block_class &block
  block.call
  block.foobar
  puts block.class.inspect
end  

block_class { puts "I'm a..." }
# I'm a...
# method on Proc!
# Proc

Try this instead:

def foo(&block)
  block.class.name
end

foo { 1 } # => "Proc"

Of course, you can't just assign a block to a variable without a method. But if you have that method return the block, it is a Proc. So how are blocks not of class Proc?

blocks are of type rb_block_t while procs are an rb_proc_t, which, as you can see, contains an rb_block_t.