Strange compile error: "No given instance of type Queryable[…]" when used with ZIO #92
Description
I've run into a very strange error with ScalaSQL 0.1.20, Scala 3.7.2 and ZIO 2.1.20.
The code looks as follows:
import scalasql.PostgresDialect.*
import scalasql.simple.{*}
import scalasql.*
case class Test(
id: Long,
)
sealed trait Task[+A]
def attemptBlocking[A](block: A): Task[A] = ???
object Test extends SimpleTable[Test]
def persist(db: DbClient): Task[Unit] =
attemptBlocking:
db.transaction: tx =>
val importId = 0L
tx.run:
Test.insert.batched(
_.id,
)(
Seq(importId)*
)https://scastie.scala-lang.org/G70bLQMwTpaRXYRGNeKGng
It yields the following error:
No given instance of type scalasql.core.Queryable[
scalasql.query.InsertColumns[
[T[_$2]] =>> scalasql.namedtuples.SimpleTable.MapOver[Playground.Test, T],
Playground.Test],
R] was found for parameter qr of method run in trait DbApi.
I found:
scalasql.core.Expr.ExprQueryable[E, T²]
But method ExprQueryable in object Expr does not match type scalasql.core.Queryable[
scalasql.query.InsertColumns[
[T[_$2]] =>> scalasql.namedtuples.SimpleTable.MapOver[Playground.Test, T],
Playground.Test],
R]
where: R is a type variable with constraint <: Unit
T is a type variable with constraint <: [_] =>> Any
T² is a type variable
.
Note: a match type could not be fully reduced:
trying to reduce scalasql.namedtuples.SimpleTable.MapOver[Playground.Test, T]
failed since selector T[scalasql.namedtuples.SimpleTable.Internal.Tombstone.type]
does not match case scalasql.namedtuples.SimpleTable.Internal.Tombstone.type => Playground.Test
and cannot be shown to be disjoint from it either.
Therefore, reduction cannot advance to the remaining case
case Any => scalasql.namedtuples.SimpleTable.Record[Playground.Test, T]
It has something to do with the attemptBlocking line and with value-discard. A version without attemptBlocking compiles fine:
https://scastie.scala-lang.org/57yQAWWiROO4eiWteOag7A
As does a version with an explicit () to avoid discarding the Int value returned by tx.run:
https://scastie.scala-lang.org/o52Wxo91SyCyF0nNueXMMA
Interestingly, the same code in Scala 3.6.4 causes a compiler crash.
https://scastie.scala-lang.org/nFgtr2uhSzGgQ7WoAciNQQ
This might mean that there was a crashing bug in 3.6.4 that was then "fixed" in a way that prevents the crash but still doesn't do the right thing.