Drop @capability annotations #20396
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Drop @capability annotations #20396
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propensive
reviewed
May 13, 2024
| @@ -11,4 +11,6 @@ import annotation.experimental | |||
| * THere, the capture set of any instance of `CanThrow` is assumed to be | |||
| * `{*}`. | |||
| */ | |||
| @experimental final class capability extends StaticAnnotation | |||
| @experimental | |||
| @deprecated("To make a class a capability, let it derive from the `Capability` trait instead") | |||
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Why not phrase this as, ...let it extend the...? derives has an established meaning which isn't what's intended here.
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Summary of changes:
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noti0na1
requested changes
May 22, 2024
| | of an enclosing function literal with expected type () ?->{cap1} I | ||
| -- [E007] Type Mismatch Error: tests/neg-custom-args/captures/byname.scala:4:2 ----------------------------------------- | ||
| 4 | def f() = if cap1 == cap1 then g else g // error | ||
| | ^ | ||
| | Found: (x$0: Int) ->{cap2} Int | ||
| | Required: (x$0: Int) -> Int | ||
| | Found: ((x$0: Int) ->{cap2} Int)^{} |
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Why is there additional empty cs added to the function type?
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A maximal capability is one that derives from `caps.Cap`. Also: drop the given caps.Cap. It's not clear why there needs to be a given for it.
The current handling of class type refinements is unsound. We cannot simply use a variable for the capture set of a class argument. What we need to do instead is treat class arguments as tracked. In this commit we at least allow explicitly declared tracked arguments. This needed two modifications: - Don't additionally add a capture set for tracked arguments - Handle the case where a capture reference is of a singleton type which is another capture reference. As a next step we should treat all class arguments as implicitly tracked.
Replace with references that inherit trait `Capability`.
Drop convention that classes inheriting from universal capturing types are capability classes. Capture sets of parents
are instead ignored.
The convention led to algebraic anomalies. For instance if
class C extends A => B, Serializable
then C <: (A => B) & Serializable, which has an empty capture set. Yet we treat every occurrence of C as
implicitly carrying `cap`.
Only enrich classes with capture refinements for a parameter if the deep capture set of the parameter's type is nonempty.
… adaptation This change lets more ref trees with underlying function types keep their singleton types.
- Avoid creating capture sets of untrackable references - Refine disallowRootCapability to consider only explicit captures
When an expression has a type that derives from caps.Capability, add an explicit capture set. Also: Address other review comments
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noti0na1
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May 28, 2024
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Replace with references that inherit trait
Capability.Also: Handle tracked vals in classes.
As a next step, addCaptureRefinements should use the tracked logic for all capturing parameters. Right now, we create a fresh capture set variable instead, but that is too loose.