From: Peter Hickman <peterhickman386@...>
Date: 2011-01-17T20:02:58+09:00
Subject: Re: Obscure syntax error

The format

x ...followed by something else...

means that x is a method and anything that follows it is a parameter.
Since you don't have a method called x you get "undefined method `x'"
just like it says in the error message.

When x is a reference to a variable by itself it just returns its
value, but when you put a parameter after it it looks for a method
called x, because you are passing it a parameter "y" and the only
things you pass parameters to are methods so you get the "undefined
method `x'" message again.

In the final case again you have no method called x and therefore a
parameter, in this case the :y, is unexpected. In that you don't pass
parameters to a variable only to methods.

It's good that you checked it out in all the various implementations
of Ruby but the error message was quite clear, "undefined method `x'"
means that Ruby thinks x should be a method but you don't have a
method x defined.