private Expression simplifyExpression(Trees.Expression expression) {
      if (expression instanceof ApplyExpression) {
        ImmutableList<Trees.Expression> params = ((ApplyExpression) expression).params();
        if (params.size() == 1) {
          return params.get(0);
        }
      }
      return expression;
    }
Resolve accesors and types on {@link SimpleAccessExpression}, turning it into
{@link BoundAccessExpression}
generator-processor/src/org/immutables/generator/processor/TypeResolver.java