Wrong type inferred with Function1 and type parameter in result type #5413
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This can be reproduced without implicits with object Foo {
type Or[A]
def foo[A](from: A => Or[A]): Any = null
def id[A]: A => A = identity
foo(id)
}where typer produces package <empty> {
final lazy module val Foo: Foo$ = new Foo$()
final module class Foo$() extends Object(), _root_.scala.Serializable {
this: Foo.type =>
type Or[A >: Nothing <: Any] >: Nothing <: Any
def foo[A >: Nothing <: Any](from: Function1[A, Foo.Or[A]]): Any = null
def id[A >: Nothing <: Any]: Function1[A, A] =
{
def $anonfun(x: A): A = identity[A](x)
closure($anonfun)
}
Foo.foo[Foo.Or[_]](Foo.id[Foo.Or[_]])
}
}this issue is that the inferred type Though writing the inferred type explicitly does result in the correct typing error 6 | foo(id[Or[_]])
| ^^^^^^^^^
| Found: Foo.Or[_] => Foo.Or[_]
| Required: Nothing => Foo.Or[A]
|
| where: A is a type variableor -- [E007] Type Mismatch Error: Foo.scala:6:13 ----------------------------------
6 | foo[Or[_]](id)
| ^^
| Found: Nothing => Nothing
| Required: Foo.Or[_] => Foo.Or[Foo.Or[_]]This could be due to a missing constraint while inferring the type of |
nicolasstucki
changed the title
nicolasstucki
changed the title
|
It infers a weird type, which looks nevertheless type correct. This looks more like a problem with -Ycheck to me that it cannot typecheck this corner-case. |
nicolasstucki
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Jun 9, 2020
anatoliykmetyuk
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Jun 11, 2020
Fix #5413: Add regression tests
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This test (loosely based on tests/pos/t2023.scala) normally compiles, but does not pass -Ycheck:all:
Output of
dotc -Ycheck:all Test.scala:The text was updated successfully, but these errors were encountered: