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Add unsafeUnbox as an escape hatch for unboxing * 
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5 files changed

+61
-28
lines changed

5 files changed

+61
-28
lines changed

‎compiler/src/dotty/tools/dotc/cc/CaptureOps.scala

Lines changed: 8 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -96,6 +96,13 @@ extension (tp: Type)
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/** Is the boxedCaptureSet of this type nonempty? */
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def isBoxedCapturing(using Context) = !tp.boxedCaptureSet.isAlwaysEmpty
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/** If this type is a boxed capturing type, its unboxed version */
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def unbox(using Context): Type = tp match
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case tp @ CapturingType(parent, refs) if tp.isBoxed =>
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CapturingType(parent, refs, boxed = false)
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case _ =>
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tp
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/** Map capturing type to their parents. Capturing types accessible
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* via dealising are also stripped.
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*/
@@ -155,6 +162,7 @@ extension (sym: Symbol)
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case _ => false
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containsEnclTypeParam(sym.info.finalResultType)
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&& !sym.allowsRootCapture
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&& sym != defn.Caps_unsafeUnbox
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extension (tp: AnnotatedType)
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/** Is this a boxed capturing type? */

‎compiler/src/dotty/tools/dotc/cc/CheckCaptures.scala

Lines changed: 23 additions & 16 deletions
Original file line numberDiff line numberDiff line change
@@ -333,22 +333,29 @@ class CheckCaptures extends Recheck, SymTransformer:
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*/
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override def recheckApply(tree: Apply, pt: Type)(using Context): Type =
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includeCallCaptures(tree.symbol, tree.srcPos)
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super.recheckApply(tree, pt) match
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case appType @ CapturingType(appType1, refs) =>
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tree.fun match
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case Select(qual, _)
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if !tree.fun.symbol.isConstructor
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&& !qual.tpe.isBoxedCapturing
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&& !tree.args.exists(_.tpe.isBoxedCapturing)
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&& qual.tpe.captureSet.mightSubcapture(refs)
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&& tree.args.forall(_.tpe.captureSet.mightSubcapture(refs))
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=>
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val callCaptures = tree.args.foldLeft(qual.tpe.captureSet)((cs, arg) =>
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cs ++ arg.tpe.captureSet)
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appType.derivedCapturingType(appType1, callCaptures)
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.showing(i"narrow $tree: $appType, refs = $refs, qual = ${qual.tpe.captureSet} --> $result", capt)
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case _ => appType
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case appType => appType
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tree match
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case Apply(fn, arg :: Nil) if fn.symbol == defn.Caps_unsafeUnbox =>
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val argType0 = recheckStart(arg, pt).unbox
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val argType = super.recheckFinish(argType0, arg, pt)
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super.recheckFinish(argType, tree, pt)
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case _ =>
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super.recheckApply(tree, pt) match
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case appType @ CapturingType(appType1, refs) =>
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tree.fun match
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case Select(qual, _)
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if !tree.fun.symbol.isConstructor
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&& !qual.tpe.isBoxedCapturing
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&& !tree.args.exists(_.tpe.isBoxedCapturing)
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&& qual.tpe.captureSet.mightSubcapture(refs)
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&& tree.args.forall(_.tpe.captureSet.mightSubcapture(refs))
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=>
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val callCaptures = tree.args.foldLeft(qual.tpe.captureSet)((cs, arg) =>
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cs ++ arg.tpe.captureSet)
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appType.derivedCapturingType(appType1, callCaptures)
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.showing(i"narrow $tree: $appType, refs = $refs, qual = ${qual.tpe.captureSet} --> $result", capt)
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case _ => appType
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case appType => appType
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end recheckApply
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/** Handle an application of method `sym` with type `mt` to arguments of types `argTypes`.
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* This means:

‎compiler/src/dotty/tools/dotc/core/Definitions.scala

Lines changed: 15 additions & 12 deletions
Original file line numberDiff line numberDiff line change
@@ -943,23 +943,26 @@ class Definitions {
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@tu lazy val RuntimeTuplesModule: Symbol = requiredModule("scala.runtime.Tuples")
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@tu lazy val RuntimeTuplesModuleClass: Symbol = RuntimeTuplesModule.moduleClass
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lazy val RuntimeTuples_consIterator: Symbol = RuntimeTuplesModule.requiredMethod("consIterator")
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lazy val RuntimeTuples_concatIterator: Symbol = RuntimeTuplesModule.requiredMethod("concatIterator")
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lazy val RuntimeTuples_apply: Symbol = RuntimeTuplesModule.requiredMethod("apply")
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lazy val RuntimeTuples_cons: Symbol = RuntimeTuplesModule.requiredMethod("cons")
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lazy val RuntimeTuples_size: Symbol = RuntimeTuplesModule.requiredMethod("size")
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lazy val RuntimeTuples_tail: Symbol = RuntimeTuplesModule.requiredMethod("tail")
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lazy val RuntimeTuples_concat: Symbol = RuntimeTuplesModule.requiredMethod("concat")
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lazy val RuntimeTuples_toArray: Symbol = RuntimeTuplesModule.requiredMethod("toArray")
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lazy val RuntimeTuples_productToArray: Symbol = RuntimeTuplesModule.requiredMethod("productToArray")
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lazy val RuntimeTuples_isInstanceOfTuple: Symbol = RuntimeTuplesModule.requiredMethod("isInstanceOfTuple")
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lazy val RuntimeTuples_isInstanceOfEmptyTuple: Symbol = RuntimeTuplesModule.requiredMethod("isInstanceOfEmptyTuple")
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lazy val RuntimeTuples_isInstanceOfNonEmptyTuple: Symbol = RuntimeTuplesModule.requiredMethod("isInstanceOfNonEmptyTuple")
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@tu lazy val RuntimeTuples_consIterator: Symbol = RuntimeTuplesModule.requiredMethod("consIterator")
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@tu lazy val RuntimeTuples_concatIterator: Symbol = RuntimeTuplesModule.requiredMethod("concatIterator")
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@tu lazy val RuntimeTuples_apply: Symbol = RuntimeTuplesModule.requiredMethod("apply")
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@tu lazy val RuntimeTuples_cons: Symbol = RuntimeTuplesModule.requiredMethod("cons")
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@tu lazy val RuntimeTuples_size: Symbol = RuntimeTuplesModule.requiredMethod("size")
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@tu lazy val RuntimeTuples_tail: Symbol = RuntimeTuplesModule.requiredMethod("tail")
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@tu lazy val RuntimeTuples_concat: Symbol = RuntimeTuplesModule.requiredMethod("concat")
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@tu lazy val RuntimeTuples_toArray: Symbol = RuntimeTuplesModule.requiredMethod("toArray")
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@tu lazy val RuntimeTuples_productToArray: Symbol = RuntimeTuplesModule.requiredMethod("productToArray")
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@tu lazy val RuntimeTuples_isInstanceOfTuple: Symbol = RuntimeTuplesModule.requiredMethod("isInstanceOfTuple")
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@tu lazy val RuntimeTuples_isInstanceOfEmptyTuple: Symbol = RuntimeTuplesModule.requiredMethod("isInstanceOfEmptyTuple")
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@tu lazy val RuntimeTuples_isInstanceOfNonEmptyTuple: Symbol = RuntimeTuplesModule.requiredMethod("isInstanceOfNonEmptyTuple")
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@tu lazy val TupledFunctionTypeRef: TypeRef = requiredClassRef("scala.util.TupledFunction")
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def TupledFunctionClass(using Context): ClassSymbol = TupledFunctionTypeRef.symbol.asClass
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def RuntimeTupleFunctionsModule(using Context): Symbol = requiredModule("scala.runtime.TupledFunctions")
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963+
@tu lazy val CapsModule: Symbol = requiredModule("scala.caps")
964+
@tu lazy val Caps_unsafeUnbox: Symbol = CapsModule.requiredMethod("unsafeUnbox")
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// Annotation base classes
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@tu lazy val AnnotationClass: ClassSymbol = requiredClass("scala.annotation.Annotation")
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@tu lazy val ClassfileAnnotationClass: ClassSymbol = requiredClass("scala.annotation.ClassfileAnnotation")

‎library/src/scala/caps.scala

Lines changed: 11 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,11 @@
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package scala
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import annotation.experimental
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// @experimental , suppress @experimental so we can use in compiler itself
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object caps:
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/** If argument is of type `box cs T`, converts to type `cs T`. This
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* avoids the error that would be raised when unboxing `*`.
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*/
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extension [T](x: T) def unsafeUnbox: T = x

‎tests/pos-custom-args/captures/unsafe-unbox.scala

Lines changed: 4 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,4 @@
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import caps.*
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def test =
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var finalizeActions = collection.mutable.ListBuffer[() => Unit]()
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val action = finalizeActions.remove(0).unsafeUnbox

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