title: ANTLR MismatchedTokenException on simple grammar
body: <p>I'm completely new to ANTLR and EBNF grammars to begin with, so this is probably a basic issue I'm simply not understanding.</p>
  
  <p>I have a rule such as:</p>
  
  <pre><code>version_line : WS? 'VERS' WS? '=' WS? '1.0' WS? EOL ;
  WS : ' '+ ;
  EOL : '\r' | '\n' | '\r\n' | '\n\r' ;
  </code></pre>
  
  <p>that matches a statement in my input file that looks like this (with optional whitespace):</p>
  
  <pre><code>VERSION = 1.0
  </code></pre>
  
  <p>With the rule form above, I'm getting a successful match, although I get an exception with this form:</p>
  
  <pre><code>version_line : WS? 'VERS' WS? '=' WS? '1' '.0' WS? EOL ;
  </code></pre>
  
  <p>or this form:</p>
  
  <pre><code>version_line : WS? 'VERS' WS? '=' WS? DIGIT '.0' WS? EOL ;
  DIGIT : '1' ;
  </code></pre>
  
  <p>Why is this different? I discovered this issue when trying to decompose the rule even more, hopefully ending up with something like this:</p>
  
  <pre><code>version_line : WS? 'VERS' WS? '=' WS? DIGIT '.' DIGIT WS? EOL ;
  DIGIT : '0'..'9' ;
  </code></pre>