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Note: dartanalyzer and editor also error with this example. I'm guessing the parser implementations currently expect a ')', '}', or ';' after a sequence of cascades.

It is curious that the spec allows a getter in a cascade ("A cascaded method invocation has the form e..suffix where e is an expression and suffix is a sequence of operator, method, getter or setter invocations.") and yet the cascade does not allow the value of the getter to be gotten:

var x = new DateTime.now()..millisecondsSinceEpoch; // x is the DateTime instance.

As far as I can see by looking at the grammar, the parser is correct. I believe that the cascade expression needs to be in parentheses for this to be correct:

  if ((new DateTime.now()..millisecondsSinceEpoch) == 42) {

and even that is suspect, because it means to compare the DateTime with an int. (But perhaps that's really what the test wants to do; I haven't looked at it.)

This comment was originally written by @mhausner

Brian is correct. The grammar is:

equalityExpression:
  relationalExpression (equalityOperator relationalExpression)? | ....

A relationalExpression can't have cascades. So it seems to me that all parsers are correct.

Not a bug.