Compiled code and related error messages

function lenc(m) {
 "compiled";
  var l = m.length(m);
  return l;
}
function len() {
  var m = "123.456";
  console.log(lenc());
}

with len() entered/run in console complains:

 1v80 Copyright 2015 G.Williams
>echo(0);
=undefined
>len()
undefined
=undefined
Uncaught Error: Expecting a function to call, got Number
 at line 3 col 21
  console.log(lenc(m));
                     ^
in function "len" called from line 1 col 5
len()
     ^
> 

I know that it should read var l = m.length; in lenc()... but I got there only after a while when my mind had let go of the deceipt by the error message and I took a closer look at lenc().