Decopose Mutable #24495
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Decopose Mutable #24495
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hamzaremmal
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Nov 20, 2025
hamzaremmal
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Nov 20, 2025
docs/_docs/reference/experimental/capture-checking/mutability.md
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hamzaremmal
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hamzaremmal
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hamzaremmal
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| r | ||
| ``` | ||
| Here, `r` is a fresh reference of type `Ref[String]` that escapes the scope of `withFile`. That's OK only since | ||
| `Ref` is classified as `Unscoped`. Since `Unscoped` is a [classifier](./classifiers.md) it means that `Ref` cannot possibly capture `f`, which as a `File` is not classified as `Unscoped`. So returning a `Ref` |
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Can a scoped capability capture an unscoped capability?
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Does the Ref need to be fresh to be allowed to be captured by the value returned from op?
For example, suppose we changed the signature of withFile to:
def withFile[T](op: (f: File^, r: Ref[String]^) => T): T =Could we then call it with an op whose result type captures r?
bishabosha
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Nov 21, 2025
docs/_docs/reference/experimental/capture-checking/mutability.md
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bishabosha
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Also: drop redundant statement in captureSetImpliedByFields
Still missing: Make Mutable an Unscoped
Fix: the APPLY rule had to be changed so that it does not kick in if the result has Unscoped capabilities. These need to be preserved, we cannot approximate by the (possibly pure) function type.
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First commit: New doc page for decomposed mutables
Todo: