extension method involving opaque type fails #15255
Description
Compiler version
3.1.2
Minimized code
package fails {
opaque type Fails[V] = V
object Fails:
def lift[V](v: V): Fails[V] = v
extension[V](f: Fails[V])
def value: V = f
// defining this method at same level as opaque type `Fails` will not work
extension[V](v: V)
def asFails: Fails[V] = Fails.lift(v)
}Output
Welcome to Scala 3.1.2 (11.0.15, Java OpenJDK 64-Bit Server VM).
Type in expressions for evaluation. Or try :help.
scala> import coulomb.fails.*
// lifting using "asFails" method yields a strange type with "quantity$package" in it
// the type should be "coulomb.fails.Fails[Int]" - see next example
scala> val f = 7.asFails
val f: coulomb.fails.quantity$package.Fails[Int] = 7
// invoking the "value" method causes a failure
scala> f.value
-- [E008] Not Found Error: -----------------------------------------------------
1 |f.value
|^^^^^^^
|value value is not a member of coulomb.fails.quantity$package.Fails[Int]
1 error found
// lifting this way will work - note the correct type
scala> val f2 = Fails.lift(7)
val f2: coulomb.fails.Fails[Int] = 7
// value method works:
scala> f2.value
val res0: Int = 7Expectation
I would expect both "asFail" and "Fail.lift" to work correctly and "value" method to work correctly
For comparison, defining the external lifter at a different level will work properly:
package works {
opaque type Works[V] = V
object Works:
def lift[V](v: V): Works[V] = v
extension[V](w: Works[V])
def value: V = w
object syntax:
// defining external lift in subobject "syntax" does work
extension[V](v: V)
def asWorks: Works[V] = Works.lift(v)
}Welcome to Scala 3.1.2 (11.0.15, Java OpenJDK 64-Bit Server VM).
Type in expressions for evaluation. Or try :help.
scala> import coulomb.works.*, coulomb.works.syntax.*
scala> val w = 7.asWorks
val w: coulomb.works.Works[Int] = 7
scala> w.value
val res0: Int = 7
scala> val w2 = Works.lift(7)
val w2: coulomb.works.Works[Int] = 7
scala> w2.value
val res1: Int = 7