Fix isPartOf

This fixes one error in the lists pos test and several spurious errors in neg tests.
There remains an error in lists.scala that has to do with bindings getting lost for
polymorphic closures. This needs to be followd up separately.

Author: odersky

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

@@ -596,7 +596,7 @@ object CaptureSet:
       val find = new TypeAccumulator[Boolean]:
         def apply(b: Boolean, t: Type) =
           b || t.match
-            case CapturingType(p, refs) => (refs eq this) || this(b, p)
+            case CapturingType(p, refs) => (refs eq Var.this) || this(b, p)
             case _ => foldOver(b, t)
       find(false, binder)
 
@@ -618,7 +618,9 @@ object CaptureSet:
         case elem: ParamRef if !this.isInstanceOf[BiMapped] =>
           isPartOf(elem.binder.resType)
           || {
-            capt.println(i"LEVEL ERROR $elem for $this")
+            capt.println(
+              i"""LEVEL ERROR $elem for $this
+                 |elem binder = ${elem.binder}""")
             false
           }
         case ReachCapability(elem1) =>
@@ -796,9 +798,13 @@ object CaptureSet:
       else if accountsFor(elem) then
         CompareResult.OK
       else
-        source.tryInclude(bimap.backward(elem), this)
-          .showing(i"propagating new elem $elem backward from $this to $source = $result", captDebug)
-          .andAlso(addNewElem(elem))
+        try
+          source.tryInclude(bimap.backward(elem), this)
+            .showing(i"propagating new elem $elem backward from $this to $source = $result", captDebug)
+            .andAlso(addNewElem(elem))
+        catch case ex: AssertionError =>
+          println(i"fail while tryInclude $elem of ${elem.getClass} in $this / ${this.summarize}")
+          throw ex
 
     /** For a BiTypeMap, supertypes of the mapped type also constrain
      *  the source via the inverse type mapping and vice versa. That is, if

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

@@ -1259,7 +1259,7 @@ class CheckCaptures extends Recheck, SymTransformer:
                 if other.isRootCapability then ""
                 else " since that capability is not a SharedCapability"
               i"""the existential capture root in ${ex.rootAnnot.originalBinder.resType}
-                |cannot subsume the capability $other$since"""
+                 |cannot subsume the capability $other$since"""
           i"""
              |
              |Note that ${msg.toString}"""

tests/neg-custom-args/captures/curried-closures.scala

@@ -8,7 +8,7 @@ import language.experimental.captureChecking
 
   def map3(f: Int => Int)(xs: List[Int]): List[Int] = xs.map(f)
   private val f2 = map3
-  val fc2: (f: Int => Int) -> List[Int] ->{f} List[Int] = f2 // error (?)
+  val fc2: (f: Int => Int) -> List[Int] ->{f} List[Int] = f2
 
   val f3 = (f: Int => Int) =>
     println(f(3))
@@ -27,7 +27,7 @@ import java.io.*
 def Test4(g: OutputStream^) =
   val xs: List[Int] = ???
   val later = (f: OutputStream^) => (y: Int) => xs.foreach(x => f.write(x + y))
-  val _: (f: OutputStream^) ->{} Int ->{f} Unit = later // error (?)
+  val _: (f: OutputStream^) ->{} Int ->{f} Unit = later
 
   val later2 = () => (y: Int) => xs.foreach(x => g.write(x + y))
   val _: () ->{} Int ->{g} Unit = later2 // error, inferred type is () ->{later2} Int ->{g} Unit

tests/neg-custom-args/captures/heal-tparam-cs.check

@@ -13,32 +13,20 @@
 -- [E007] Type Mismatch Error: tests/neg-custom-args/captures/heal-tparam-cs.scala:15:13 -------------------------------
 15 |    localCap { c =>  // error
    |    ^
-   |    Found:    (x$0: Capp^?) ->? () ->{x$0} Unit
+   |    Found:    (x$0: Capp^) ->? () ->{x$0} Unit
    |    Required: (c: Capp^) -> () ->{localcap} Unit
+   |
+   |    Note that the existential capture root in () => Unit
+   |    cannot subsume the capability x$0.type since that capability is not a SharedCapability
 16 |      (c1: Capp^) => () => { c1.use() }
 17 |    }
    |
    | longer explanation available when compiling with `-explain`
--- [E007] Type Mismatch Error: tests/neg-custom-args/captures/heal-tparam-cs.scala:20:13 -------------------------------
-20 |    localCap { c =>  // error (???) since change to cs mapping
-   |    ^
-   |    Found:    (x$0: Capp^?) ->? () ->{x$0} Unit
-   |    Required: (c: Capp^{io}) -> () ->{io} Unit
-   |
-   |    Note that the existential capture root in () ->? Unit
-   |    cannot subsume the capability <cap of (x$0: Capp^?): () ->{x$0} Unit>
-21 |      (c1: Capp^{io}) => () => { c1.use() }
-22 |    }
-   |
-   | longer explanation available when compiling with `-explain`
 -- [E007] Type Mismatch Error: tests/neg-custom-args/captures/heal-tparam-cs.scala:25:13 -------------------------------
 25 |    localCap { c =>  // error
    |    ^
-   |    Found:    (x$0: Capp^?) ->? () ->{x$0} Unit
+   |    Found:    (x$0: Capp^{io}) ->? () ->{x$0} Unit
    |    Required: (c: Capp^{io}) -> () ->{net} Unit
-   |
-   |    Note that the existential capture root in () ->? Unit
-   |    cannot subsume the capability <cap of (x$0: Capp^?): () ->{x$0} Unit>
 26 |      (c1: Capp^{io}) => () => { c1.use() }
 27 |    }
    |

tests/neg-custom-args/captures/heal-tparam-cs.scala

@@ -17,7 +17,7 @@ def main(io: Capp^, net: Capp^): Unit = {
     }
 
   val test3: (c: Capp^{io}) -> () ->{io} Unit =
-    localCap { c =>  // error (???) since change to cs mapping
+    localCap { c =>
       (c1: Capp^{io}) => () => { c1.use() }
     }
 

tests/pending/pos-custom-args/lists.scala renamed to tests/pos-custom-args/captures/lists.scala

@@ -21,7 +21,9 @@ def map[A, B](f: A => B)(xs: LIST[A]): LIST[B] =
 class Cap extends caps.Capability
 
 def test(c: Cap, d: Cap, e: Cap) =
+
   def f(x: Cap): Unit = if c == x then ()
+
   def g(x: Cap): Unit = if d == x then ()
   val y = f
   val ys = CONS(y, NIL)
@@ -43,7 +45,9 @@ def test(c: Cap, d: Cap, e: Cap) =
   def m2 = [A, B] =>
       (f: A => B) => (xs: LIST[A]) => xs.map(f)
 
-  def m2c: [A, B] -> (f: A => B) -> LIST[A] ->{f} LIST[B] = m2
+//  def m2c: [A, B] -> (f: A => B) -> LIST[A] ->{f} LIST[B] = m2
+//  !!! m2 has a bad type due to spurious level error. Need to follow up and
+//  fix this.
 
   def eff[A](x: A) = if x == e then x else x
 
@@ -87,4 +91,3 @@ def test(c: Cap, d: Cap, e: Cap) =
   val c2c: LIST[Cap ->{d, y} Unit]^{e} = c2
   val c3 = zs.map(eff2[Cap ->{d, y} Unit])
   val c3c: LIST[Cap ->{d, y} Unit]^{e} = c3
-