Assume special capturing types for eq and ne

They take a `{*} Object` instead of an `Object` parameter.

Author: odersky

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

@@ -31,10 +31,12 @@ object Synthetics:
    *  The types of these symbols are transformed in a special way without
    *  looking at the definitions's RHS
    */
-  def needsTransform(sym: SymDenotation)(using Context): Boolean =
-    isSyntheticCopyMethod(sym)
-    || isSyntheticCompanionMethod(sym, nme.apply, nme.unapply)
-    || isSyntheticCopyDefaultGetterMethod(sym)
+  def needsTransform(symd: SymDenotation)(using Context): Boolean =
+    isSyntheticCopyMethod(symd)
+    || isSyntheticCompanionMethod(symd, nme.apply, nme.unapply)
+    || isSyntheticCopyDefaultGetterMethod(symd)
+    || (symd.symbol eq defn.Object_eq)
+    || (symd.symbol eq defn.Object_ne)
 
   /** Method is excluded from regular capture checking.
    *  Excluded are synthetic class members
@@ -166,7 +168,9 @@ object Synthetics:
       sym.copySymDenotation(info = addUnapplyCaptures(sym.info))
     case nme.apply | nme.copy =>
       sym.copySymDenotation(info = addCaptureDeps(sym.info))
-
+    case n if n == nme.eq || n == nme.ne =>
+      sym.copySymDenotation(info =
+        MethodType(defn.ObjectType.capturing(CaptureSet.universal) :: Nil, defn.BooleanType))
 
   /** If `sym` refers to a synthetic apply, unapply, copy, or copy default getter method
    *  of a case class, transform it back to what it was before the CC phase.
@@ -179,5 +183,7 @@ object Synthetics:
       sym.copySymDenotation(info = dropUnapplyCaptures(sym.info))
     case nme.apply | nme.copy =>
       sym.copySymDenotation(info = dropCaptureDeps(sym.info))
+    case n if n == nme.eq || n == nme.ne =>
+      sym.copySymDenotation(info = defn.methOfAnyRef(defn.BooleanType))
 
 end Synthetics