Make all enums in cc derive CanEqual

Caught one bug in CaptureSet

Author: odersky

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

@@ -925,7 +925,7 @@ object Capabilities:
    *    Unclassified     : No set exists since some parts of tcs are not classified
    *    ClassifiedAs(clss: All parts of tcss are classified with classes in clss
    */
-  enum Classifiers:
+  enum Classifiers derives CanEqual:
     case UnknownClassifier
     case Unclassified
     case ClassifiedAs(clss: List[ClassSymbol])
@@ -966,7 +966,7 @@ object Capabilities:
   /** The place of - and cause for - creating a fresh capability. Used for
    *  error diagnostics
    */
-  enum Origin:
+  enum Origin derives CanEqual:
     case InDecl(sym: Symbol)
     case TypeArg(tp: Type)
     case UnsafeAssumePure

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

@@ -156,7 +156,7 @@ sealed abstract class CaptureSet extends Showable:
    */
   final def maybeExclusive(using Context): Boolean = reporting.trace(i"mabe exclusive $this"):
     if isConst then elems.exists(_.maybeExclusive)
-    else mutability != ReadOnly
+    else mutability != Reader
 
   final def keepAlways: Boolean = this.isInstanceOf[EmptyWithProvenance]
 
@@ -541,7 +541,7 @@ object CaptureSet:
   type Vars = SimpleIdentitySet[Var]
   type Deps = SimpleIdentitySet[CaptureSet]
 
-  enum Mutability:
+  enum Mutability derives CanEqual:
     case Writer, Reader, Ignored
 
     def | (that: Mutability): Mutability =

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

@@ -40,7 +40,7 @@ object CheckCaptures:
   val name: String = "cc"
   val description: String = "capture checking"
 
-  enum EnvKind:
+  enum EnvKind derives CanEqual:
     case Regular        // normal case
     case NestedInOwner  // environment is a temporary one nested in the owner's environment,
                         // and does not have a different actual owner symbol

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

@@ -15,7 +15,7 @@ import typer.ProtoTypes.LhsProto
 object Mutability:
 
   /** Either OK, or a reason why capture set cannot be exclusive */
-  private enum Exclusivity:
+  private enum Exclusivity derives CanEqual:
     case OK
 
     /** Enclosing symbol `sym` is a method of class `cls`, but not an update method */

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

@@ -31,7 +31,7 @@ import Capabilities.*
 object SepCheck:
 
   /** Enumerates kinds of captures encountered so far */
-  enum Captures:
+  enum Captures derives CanEqual:
     case None
     case Explicit   // one or more explicitly declared captures
     case Hidden     // exacttly one hidden captures
@@ -45,7 +45,7 @@ object SepCheck:
   end Captures
 
   /** The role in which a checked type appears, used for composing error messages */
-  enum TypeRole:
+  enum TypeRole derives CanEqual:
     case Result(sym: Symbol, inferred: Boolean)
     case Argument(arg: Tree, meth: Symbol)
     case Qualifier(qual: Tree, meth: Symbol)