Closed
Description
Compiler version
3.3.1
Minimized code
trait Animal
class Dog extends Animal
trait Ev[T]
given Ev[Dog] = ???
given Ev[Animal] = ???
given [T: Ev]: Ev[Set[T]] = ???
def f[T: Ev](v: T): Unit = ???
def main =
val s = Set(new Dog)
f(s)
f(Set(new Dog))Output
[error] Ambiguous given instances: both given instance given_Ev_Dog and given instance given_Ev_Animal match type Ev[T] of an implicit parameter of method f
[error] f(Set(new Dog))
[error] ^
Note that the error is from the very last line. The first call f(s) is okay.
From typer:
package <empty> {
trait Animal() extends Object {}
class Dog() extends Object(), Animal {}
trait Ev[T >: Nothing <: Any]() extends Object {
T
}
final lazy module val implicit-variance$package: implicit-variance$package =
new implicit-variance$package()
final module class implicit-variance$package() extends Object() {
this: implicit-variance$package.type =>
final lazy given val given_Ev_Dog: Ev[Dog] = ???
final lazy given val given_Ev_Animal: Ev[Animal] = ???
final given def given_Ev_Set[T >: Nothing <: Any](implicit evidence$1: Ev[T]
): Ev[Set[T]] = ???
def f[T >: Nothing <: Any](v: T)(implicit evidence$2: Ev[T]): Unit = ???
def main:
<error both given instance given_Ev_Dog and given instance given_Ev_Animal match type Ev[T]>
=
{
val s: Set[Dog] = Set.apply[Dog]([new Dog() : Dog]*)
f[Set[Dog]](s)(given_Ev_Set[Dog](given_Ev_Dog))
f[Set[Dog]](Set.apply[Dog]([new Dog() : Dog]*))(
given_Ev_Set[T](
/* ambiguous: both given instance given_Ev_Dog and given instance given_Ev_Animal match type Ev[T] */
summon[Ev[T]]
)
)
}
}
}Expectation
It should compile.