Cascade implicit block hides missing do syntax errors #179

a
 b
  c
   d
    e

compiles to

var x$, y$, z$, z1$;
x$ = a;
y$ = b;
z$ = c;
z1$ = d;
e;

even though the cascadee isn't used. This hides some typos involving a missing do that were previously caught at compile time, such as:

method
   arg1
   arg2

var x$;
x$ = method;
arg1;
arg2;

and even though this works when run, it hides the fact that |> doesn't actually accept an implicit block:

program = @createProgram! |>
    @attachShader _, vertex-shader
    @attachShader _, fragment-shader
    @linkProgram _
    unless @getProgramParameter _, LINK_STATUS
      throw new Error "couldn't intialize shader program!"
    @useProgram _

var x$, program, _;
x$ = (_ = program = this.createProgram(), this.attachShader(_, vertexShader));
this.attachShader(_, fragmentShader);
this.linkProgram(_);
if (!this.getProgramParameter(_, LINK_STATUS)) {
  throw new Error("couldn't intialize shader program!");
}
this.useProgram(_);

Proposal: cascade blocks in which the cascadee isn't used at least once should be invalid syntax. The error message should be similar to "Unexpected INDENT on line xx:xx, did you forget a 'do' or a cascade usage?"