Runtime exception if the value of record field is Any or AnyRef about shapeless HOT 7 OPEN

You'll see the same phenomenon with vanilla tagged types, eg.,

scala> import shapeless._
import shapeless._

scala> trait Foo
defined trait Foo

scala> tag[Foo](1)
res0: shapeless.tag.@@[Int,Foo] = 1

scala> tag[Foo](1: Any)
java.lang.ClassCastException: java.lang.Integer cannot be cast to shapeless.tag$Tagged
        at .<init>(<console>:12)
        ...

Is this a showstopper for you, or are you able to make progress by avoiding ascribing Any or AnyRef?

from shapeless.

In sqltyped the following query no longer works:

sql("select name, ? as x from person")

Currently it is typed as (Stuff within curlies are records, not structural types. I'm using that syntax just for readability here):

Any => List[{ name: String, x: Any }]

Any, because we do not know anything about x. That's not a deal breaker though. I can drop support for those queries. It is not very common to just send data to database server only to return it back. Perhaps more common is to execute some function in a database like:

sql("select name, upper(?) as x from person")

Typing at least some of SQL queries like that might succeed. Here we at least know that 'upper' returns VARCHAR.

In general, when using records this may cause some unexpected crashes when scalac infers too general type.

def bar(x: Int) = if (x > 10) 5 else "10"

... then in some other source file etc. ....

"foo" ->> bar(2)
java.lang.ClassCastException: java.lang.String cannot be cast to shapeless.record$KeyTag

Now it is not very easy to figure out the cause of the problem. But I guess this is pretty hard to fix, right?

from shapeless.

I'm afraid so. If you can work around it for now I'll see what I can do for M2.

from shapeless.

Yes, no problem. Thanks!

from shapeless.

Still present in shapeless 2.0.0 and with Scala 2.11.1 ... is this still an issue for you?

from shapeless.

It is still an issue but not a critical one. It is a rather rare corner case.

from shapeless.

Still present in shapeless 2.3.0-SNAPSHOT and with Scala 2.11.7. A fix would most likely involved reverting #20 and that currently breaks records. I'll punt this to 3.0.0.

from shapeless.