I am trying to compile the mongodb fantom driver and I get this compilation error:

===

D:\fan\fantomongo\fan\bson\BsonWriter.fan(48,27): Invalid args writeDateTime(sys::Buf, sys::Str, sys::DateTime), not (sys::Buf, sys::Str, sys::DateTime?) BUILD FAILED 252ms!

===

This is the declaration of writeDateTime:

private static Void writeDateTime(Buf b, Str key, DateTime d)
{
  b.write(Bson.DATE)
  writeCStr(b.out, key)
  b.writeI8(d.toJava())
}

This is where the compilation error happen:

private static Void writeKeyVal(Buf b, Str key, Obj? val)
{
  if (val == null) writeNull(b, key)
  else if (val is Str) writeStr(b, key, val)
  else if (val is Date) writeDateTime(b, key, val as DateTime) // convert to DateTime  //Compoilation Error!!!!
  else if (val is DateTime) writeDateTime(b, key, val)

.....

Does anybody know the story behind the compilation error? The code looks totally fine for me.

Thanks,

sorry,delete this

The following expressions are considered equivalent

obj is Str? => obj is Str
obj as Str => obj as Str?

It's confused.I suggest to forcibly using obj is Str and obj as Str?.

Thanks! That is a really quick reply. I am new to fantom and have thought this is a small community and I would expect to long delay to get a reply at weekend. I guess I am wrong.

I also think this implicit conversion will confuse some beginners of the language. It should at least give some hint at the error messages.

I suspect the error was introduced by issue `http://fantom.org/sidewalk/topic/1127` which made is illegal to use an as expression where a non-nullable was expected. In this case removing the as DateTime should fix the problem (using an implicit cast to DateTime).

It's confused.I suggest to forcibly using obj is Str and obj as Str?.

The expression x as Str evaluates to Str? by definition. It is actually a compile time error to use x as Str?.

I just pushed a changeset that updates this: http://bitbucket.org/liamstask/fantomongo/changeset/733012360ad2

How to implement it by method ,Like this obj.is(DateTime), obj.as(DateTime).it is more pretty

go4,

Implementing it as method is acceptable for as (because you'll get almost the same with safe invoke - foo?.as(Bar#) instead of foo as Bar. However with is it gets more uglier - instead of foo is Bar you'll have to write foo?.is(Bar#) ?: false.

foo?.as(Bar#)

is more pretty than

foo as Bar

? I don't think so.

helium.

foo.as(Bar).isOdd() <=> (foo as Bar).isOdd()

perhaps it's not pretty,but more OO.

I can't find the thread, where jodastephen refers to recent news (Java/Oracle) here, but I suggest fostering and supporting non-relational (or controlled by big entities like Ora, IBM or SAP) databases can only be beneficial to Famtom, too.