private AssertStatement ParseAssertStmt() {
Eat(TokenKind.KeywordAssert);
var start = GetStart();
Expression expr = ParseExpression();
Expression message = null;
if (MaybeEat(TokenKind.Comma)) {
message = ParseExpression();
}
AssertStatement ret = new AssertStatement(expr, message);
ret.SetLoc(_globalParent, start, GetEnd());
return ret;
}