SIP-73 - Adding Flexible Types as Internal Type to Scala 3 Spec #115
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didnt this already ship in Scala 3.5? |
The implementation has been shipped. The core team is asking for a SIP to finalize the tag in TASTy. See the discussion at: scala/scala3#23682 |
noti0na1
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| #### Type Erasure (Extension to §3.8) | ||
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| The erased type of `T?` is the erased type of the underlying type `T`. | ||
| Erasure is extended with: `|T?| = |T|` (i.e., identical to the erasure of its underlying type). |
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What happens if T is Int, or any other really-non-nullable primitive type?
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I have updated the Type Erasure section to explain the choice.
bracevac
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| They may appear in type signatures because of type inference. | ||
| Due to their non-denotable nature, we do not recommend exposing Flexible Types in public APIs or library interfaces. | ||
| We have implemented a mechanism to warn users when Flexible Types are exposed at public (or protected) field or method boundaries. |
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I think it'd be good if the SIP could describe in more detail this warning mechanism and other situations where users might be confronted with flexible types. Ideally with a comparison to how platform types are handled in Kotlin since they have a similar nature and I assume have had time to get a polished user experience.
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(or maybe this comes up in the follow-up explicit nulls SIP, not sure where to draw the line)
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Do we really need flexible types as a separate form of type? I can do this: type Flex[T] >: T | Null <: T
var x: Flex[String] = null
x = "abc"
val y = x.length
val s: String = xThe only error I get is that type Flex has conflicting bounds. If I suppress that error, everything compiles fine. So, can we make do with just defining a type like |
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