Also freshen type arguments in parent classes

Author: odersky

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

@@ -167,7 +167,7 @@ class Setup extends PreRecheck, SymTransformer, SetupAPI:
       def mappedInfo =
         if toBeUpdated.contains(sym)
         then symd.info // don't transform symbols that will anyway be updated
-        else transformExplicitType(symd.info, sym, freshen = true)
+        else transformExplicitType(symd.info, sym)
       if Synthetics.needsTransform(symd) then
         Synthetics.transform(symd, mappedInfo)
       else if isPreCC(sym) then
@@ -349,7 +349,7 @@ class Setup extends PreRecheck, SymTransformer, SetupAPI:
    *   5. Schedule deferred well-formed tests for types with retains annotations.
    *   6. Perform normalizeCaptures
    */
-  private def transformExplicitType(tp: Type, sym: Symbol, freshen: Boolean, tptToCheck: Tree = EmptyTree)(using Context): Type =
+  private def transformExplicitType(tp: Type, sym: Symbol, tptToCheck: Tree = EmptyTree)(using Context): Type =
 
     def fail(msg: Message) =
       if !tptToCheck.isEmpty then report.error(msg, tptToCheck.srcPos)
@@ -483,9 +483,7 @@ class Setup extends PreRecheck, SymTransformer, SetupAPI:
     val tp3 =
       if sym.isType then stripImpliedCaptureSet(tp2)
       else tp2
-    if freshen then
-      capToFresh(tp3, Origin.InDecl(sym))
-    else tp3
+    capToFresh(tp3, Origin.InDecl(sym))
   end transformExplicitType
 
   /** Update info of `sym` for CheckCaptures phase only */
@@ -516,7 +514,7 @@ class Setup extends PreRecheck, SymTransformer, SetupAPI:
         var transformed =
           if tree.isInferred
           then transformInferredType(tree.tpe)
-          else transformExplicitType(tree.tpe, sym, freshen = true, tptToCheck = tree)
+          else transformExplicitType(tree.tpe, sym, tptToCheck = tree)
         if boxed then transformed = transformed.boxDeeply
         tree.setNuType(
           if sym.hasAnnotation(defn.UncheckedCapturesAnnot) then makeUnchecked(transformed)

tests/neg-custom-args/captures/hk-param.scala

@@ -1,6 +1,6 @@
 /** Concrete collection type: View */
 trait View[+A] extends Itable[A], ILike[A, [X] =>> View[X]^]: // error
-  override def fromIterable[B](c: Itable[B]^): View[B]^{c} = ???
+  override def fromIterable[B](c: Itable[B]^): View[B]^{c} = ??? // error
 
 trait IPolyTransforms[+A, +C[A]] extends Any:
   def fromIterable[B](coll: Itable[B]^): C[B]

tests/neg-custom-args/captures/unsound-reach-4.check

@@ -12,19 +12,20 @@
    |                             Required: Foo[File^]
    |
    |                             Note that capability cap is not included in capture set {cap²}
-   |                             because cap is not visible from cap² in value backdoor.
+   |                             because cap in class Bar is not visible from cap² in value backdoor.
    |
    |                             where:    ^ and cap² refer to a fresh root capability in the type of value backdoor
-   |                                       cap        is the universal root capability
+   |                                       cap        is a fresh root capability created in class Bar
    |
    | longer explanation available when compiling with `-explain`
 -- [E164] Declaration Error: tests/neg-custom-args/captures/unsound-reach-4.scala:17:6 ---------------------------------
 17 |  def use(consume x: F): File^ = x // error consume override
    |      ^
-   |      error overriding method use in trait Foo of type (x: File^): File^;
-   |        method use of type (@consume x: File^): File^² has incompatible type
+   |      error overriding method use in trait Foo of type (x: File^): File^²;
+   |        method use of type (@consume x: File^): File^³ has incompatible type
    |
    |      where:    ^  refers to the universal root capability
-   |                ^² refers to a root capability associated with the result type of (@consume x: File^): File^²
+   |                ^² refers to a fresh root capability created in class Bar
+   |                ^³ refers to a root capability associated with the result type of (@consume x: File^): File^³
    |
    | longer explanation available when compiling with `-explain`

tests/neg-custom-args/captures/unsound-reach.check

@@ -12,10 +12,10 @@
    |                             Required: Foo[File^]
    |
    |                             Note that capability cap is not included in capture set {cap²}
-   |                             because cap is not visible from cap² in value backdoor.
+   |                             because cap in class Bar is not visible from cap² in value backdoor.
    |
    |                             where:    ^ and cap² refer to a fresh root capability in the type of value backdoor
-   |                                       cap        is the universal root capability
+   |                                       cap        is a fresh root capability created in class Bar
    |
    | longer explanation available when compiling with `-explain`
 -- [E007] Type Mismatch Error: tests/neg-custom-args/captures/unsound-reach.scala:27:32 --------------------------------
@@ -25,9 +25,9 @@
    |                             Required: Foo2[File^]
    |
    |                             Note that capability cap is not included in capture set {cap²}
-   |                             because cap is not visible from cap² in value backdoor.
+   |                             because cap in class Bar2 is not visible from cap² in value backdoor.
    |
    |                             where:    ^ and cap² refer to a fresh root capability in the type of value backdoor
-   |                                       cap        is the universal root capability
+   |                                       cap        is a fresh root capability created in class Bar2
    |
    | longer explanation available when compiling with `-explain`