title: What are the semantics of _internal?
body: <p>I keep seeing references to _internal in examples like the following:</p>
  
  
  
  <pre class="lang-dart prettyprint-override"><code>class Symbol {
      final String name;
      static Map&lt;String, Symbol&gt; _cache;
  
      factory Symbol(String name) {
          if (_cache == null) {
          _cache = {};
       }
  
       if (_cache.containsKey(name)) {
          return _cache[name];
       } else {
          final symbol = new Symbol._internal(name);
          _cache[name] = symbol;
          return symbol;
        }
      }
  
    Symbol._internal(this.name);
  }
  </code></pre>
  
  <p>I've gathered from the code that it's a privately accessible constructor.  The last line <code>Symbol._internal(this.name);</code> seems a bit confusing because it appears to be a statement within the class body and not within a method body, leading me to believe it's actually the internal constructor definition without a method body.</p>
  
  <p>Are my assumptions correct?</p>