Enable local roots

Author: odersky

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

@@ -17,7 +17,7 @@ import collection.mutable
 private val Captures: Key[CaptureSet] = Key()
 private val BoxedType: Key[BoxedTypeCache] = Key()
 
-private val enableRootMapping = false
+private val enableRootMapping = true
 
 /** Switch whether unpickled function types and byname types should be mapped to
  *  impure types. With the new gradual typing using Fluid capture sets, this should

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

@@ -1075,28 +1075,29 @@ class CheckCaptures extends Recheck, SymTransformer:
         }
         assert(roots.nonEmpty)
         for case root: ClassSymbol <- roots do
-          checkSelfAgainstParents(root, root.baseClasses)
-          val selfType = root.asClass.classInfo.selfType
-          interpolator(startingVariance = -1).traverse(selfType)
-          if !root.isEffectivelySealed  then
-            def matchesExplicitRefsInBaseClass(refs: CaptureSet, cls: ClassSymbol): Boolean =
-              cls.baseClasses.tail.exists { psym =>
-                val selfType = psym.asClass.givenSelfType
-                selfType.exists && selfType.captureSet.elems == refs.elems
-              }
-            selfType match
-              case CapturingType(_, refs: CaptureSet.Var)
-              if !refs.elems.exists(_.isRootCapability) && !matchesExplicitRefsInBaseClass(refs, root) =>
-                // Forbid inferred self types unless they are already implied by an explicit
-                // self type in a parent.
-                report.error(
-                  em"""$root needs an explicitly declared self type since its
-                      |inferred self type $selfType
-                      |is not visible in other compilation units that define subclasses.""",
-                  root.srcPos)
-              case _ =>
-          parentTrees -= root
-          capt.println(i"checked $root with $selfType")
+          inContext(ctx.withOwner(root)):
+            checkSelfAgainstParents(root, root.baseClasses)
+            val selfType = root.asClass.classInfo.selfType
+            interpolator(startingVariance = -1).traverse(selfType)
+            if !root.isEffectivelySealed  then
+              def matchesExplicitRefsInBaseClass(refs: CaptureSet, cls: ClassSymbol): Boolean =
+                cls.baseClasses.tail.exists { psym =>
+                  val selfType = psym.asClass.givenSelfType
+                  selfType.exists && selfType.captureSet.elems == refs.elems
+                }
+              selfType match
+                case CapturingType(_, refs: CaptureSet.Var)
+                if !refs.elems.exists(_.isRootCapability) && !matchesExplicitRefsInBaseClass(refs, root) =>
+                  // Forbid inferred self types unless they are already implied by an explicit
+                  // self type in a parent.
+                  report.error(
+                    em"""$root needs an explicitly declared self type since its
+                        |inferred self type $selfType
+                        |is not visible in other compilation units that define subclasses.""",
+                    root.srcPos)
+                case _ =>
+            parentTrees -= root
+            capt.println(i"checked $root with $selfType")
     end checkSelfTypes
 
     /** Heal ill-formed capture sets in the type parameter.

tests/neg-custom-args/captures/cc-this2.check

@@ -2,5 +2,5 @@
 -- Error: tests/neg-custom-args/captures/cc-this2/D_2.scala:2:6 --------------------------------------------------------
 2 |class D extends C: // error
   |^
-  |reference (caps.cap : caps.Root) is not included in the allowed capture set {} of pure base class class C
+  |reference (cap : caps.Root) is not included in the allowed capture set {} of pure base class class C
 3 |  this: D^ =>

tests/neg-custom-args/captures/cc-this5.check

@@ -1,8 +1,8 @@
 -- Error: tests/neg-custom-args/captures/cc-this5.scala:16:20 ----------------------------------------------------------
 16 |    def f = println(c)  // error
    |                    ^
-   |                    (c : Cap^) cannot be referenced here; it is not included in the allowed capture set {}
-   |                    of the enclosing class A
+   |               (c : Cap^{cap[test]}) cannot be referenced here; it is not included in the allowed capture set {}
+   |               of the enclosing class A
 -- [E007] Type Mismatch Error: tests/neg-custom-args/captures/cc-this5.scala:21:15 -------------------------------------
 21 |    val x: A = this // error
    |               ^^^^

tests/neg-custom-args/captures/eta.check

@@ -8,5 +8,5 @@
 -- Error: tests/neg-custom-args/captures/eta.scala:6:20 ----------------------------------------------------------------
 6 |         bar( () => f )  // error
   |                    ^
-  |                    (f : Proc^) cannot be referenced here; it is not included in the allowed capture set {}
+  |                    (f : () => Unit) cannot be referenced here; it is not included in the allowed capture set {}
   |                    of an enclosing function literal with expected type () -> box () ->? Unit

tests/neg-custom-args/captures/exception-definitions.check

@@ -1,12 +1,12 @@
 -- Error: tests/neg-custom-args/captures/exception-definitions.scala:2:6 -----------------------------------------------
 2 |class Err extends Exception: // error
   |^
-  |reference (caps.cap : caps.Root) is not included in the allowed capture set {} of pure base class class Throwable
+  |reference (cap : caps.Root) is not included in the allowed capture set {} of pure base class class Throwable
 3 |  self: Err^ =>
 -- Error: tests/neg-custom-args/captures/exception-definitions.scala:7:12 ----------------------------------------------
 7 |    val x = c  // error
   |            ^
-  |(c : Any^) cannot be referenced here; it is not included in the allowed capture set {} of pure base class class Throwable
+  |(c : Any^{cap[test]}) cannot be referenced here; it is not included in the allowed capture set {} of pure base class class Throwable
 -- Error: tests/neg-custom-args/captures/exception-definitions.scala:8:8 -----------------------------------------------
 8 |  class Err3(c: Any^) extends Exception // error
   |  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

tests/neg-custom-args/captures/lazylist.check

@@ -8,8 +8,8 @@
 -- [E007] Type Mismatch Error: tests/neg-custom-args/captures/lazylist.scala:35:29 -------------------------------------
 35 |  val ref1c: LazyList[Int] = ref1 // error
    |                             ^^^^
-   |                 Found:    (ref1 : lazylists.LazyCons[Int]{val xs: () ->{cap1} lazylists.LazyList[Int]^}^{cap1})
-   |                 Required: lazylists.LazyList[Int]
+   |  Found:    (ref1 : lazylists.LazyCons[Int]{val xs: () ->{cap1} lazylists.LazyList[Int]^{cap[LazyCons]}}^{cap1})
+   |  Required: lazylists.LazyList[Int]
    |
    | longer explanation available when compiling with `-explain`
 -- [E007] Type Mismatch Error: tests/neg-custom-args/captures/lazylist.scala:37:36 -------------------------------------
@@ -37,6 +37,6 @@
 22 |  def tail: LazyList[Nothing]^ = ???  // error overriding
    |      ^
    |      error overriding method tail in class LazyList of type -> lazylists.LazyList[Nothing];
-   |        method tail of type -> lazylists.LazyList[Nothing]^ has incompatible type
+   |        method tail of type -> lazylists.LazyList[Nothing]^{cap[tail]} has incompatible type
    |
    | longer explanation available when compiling with `-explain`

tests/neg-custom-args/captures/lazylists2.check

@@ -25,11 +25,11 @@
 -- Error: tests/neg-custom-args/captures/lazylists2.scala:40:20 --------------------------------------------------------
 40 |      def head: B = f(xs.head)  // error
    |                    ^
-   |(f : A => B) cannot be referenced here; it is not included in the allowed capture set {xs} of the self type of class Mapped
+   |(f : A ->{cap[map3]} B) cannot be referenced here; it is not included in the allowed capture set {xs} of the self type of class Mapped
 -- Error: tests/neg-custom-args/captures/lazylists2.scala:41:48 --------------------------------------------------------
 41 |      def tail: LazyList[B]^{this}= xs.tail.map(f) // error
    |                                                ^
-   |(f : A => B) cannot be referenced here; it is not included in the allowed capture set {xs} of the self type of class Mapped
+   |(f : A ->{cap[map3]} B) cannot be referenced here; it is not included in the allowed capture set {xs} of the self type of class Mapped
 -- [E007] Type Mismatch Error: tests/neg-custom-args/captures/lazylists2.scala:45:4 ------------------------------------
 45 |    final class Mapped extends LazyList[B]:  // error
    |    ^

tests/neg-custom-args/captures/levels.check

@@ -0,0 +1,8 @@
+-- Error: tests/neg-custom-args/captures/levels.scala:15:11 ------------------------------------------------------------
+15 |    r.setV(g) // error
+   |           ^
+   |           reference (cap3 : CC^) is not included in the allowed capture set ?
+   |           of an enclosing function literal with expected type box (x$0: String) ->? String
+   |
+   |           Note that reference (cap3 : CC^), defined at level 2
+   |           cannot be included in outer capture set ?, defined at level 1 in method test

tests/neg-custom-args/captures/levels.scala

@@ -0,0 +1,33 @@
+class CC
+
+def test(cap1: CC^) =
+
+  class Ref[T](init: T):
+    private var v: T = init
+    def setV(x: T): Unit = v = x
+    def getV: T = v
+
+  val r = Ref((x: String) => x)
+
+  def scope =
+    val cap3: CC^ = ???
+    def g(x: String): String = if cap3 == cap3 then "" else "a"
+    r.setV(g) // error
+  ()
+
+/*
+  Explicit:
+    cap is local root of enclosing method or class, can be overridden by qualifying it.
+    i.e. cap[name]
+
+  On method  instantiation: All uses of cap --> cap of caller
+  On class instantiation: All uses of cap, or local cap of clsss --> cap of caller
+
+  Alternative solution: root variables
+    - track minimal & maximal level
+    - updated via subsumption tests, root added handler for prefix/member
+
+  roots: Implicitly: outer <: inner
+
+  def withFile[T]((local: Root) ?=> op: File^{local}) => T]): T
+*/