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diff --git a/src/dotty/tools/dotc/transform/ResolveSuper.scala b/src/dotty/tools/dotc/transform/ResolveSuper.scala
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+++ b/src/dotty/tools/dotc/transform/ResolveSuper.scala
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+package dotty.tools.dotc
+package transform
+
+import core._
+import TreeTransforms._
+import Contexts.Context
+import Flags._
+import SymUtils._
+import Symbols._
+import SymDenotations._
+import Types._
+import Decorators._
+import DenotTransformers._
+import StdNames._
+import NameOps._
+import ast.Trees._
+import util.Positions._
+import Names._
+import collection.mutable
+
+/** This phase adds super accessors and method overrides where
+ *  linearization differs from Java's rule for default methods in interfaces.
+ *  In particular:
+ *
+ *        For every trait M directly implemented by the class (see SymUtils.mixin), in
+ *        reverse linearization order, add the following definitions to C:
+ *
+ *          3.1 (done in `superAccessors`) For every superAccessor
+ *              `<mods> def super$f[Ts](ps1)...(psN): U` in M:
+ *
+ *                <mods> def super$f[Ts](ps1)...(psN): U = super[S].f[Ts](ps1)...(psN)
+ *
+ *              where `S` is the superclass of `M` in the linearization of `C`.
+ *
+ *          3.2 (done in `methodOverrides`) For every method
+ *              `<mods> def f[Ts](ps1)...(psN): U` in M` that needs to be disambiguated:
+ *
+ *                <mods> def f[Ts](ps1)...(psN): U = super[M].f[Ts](ps1)...(psN)
+ *
+ *        A method in M needs to be disambiguated if it is concrete, not overridden in C,
+ *        and if it overrides another concrete method.
+ *
+ *  This is the first part of what was the mixin phase. It is complemented by
+ *  Mixin, which runs after erasure.
+ */
+class ResolveSuper extends MiniPhaseTransform with IdentityDenotTransformer { thisTransform =>
+  import ast.tpd._
+
+  override def phaseName: String = "resolveSuper"
+
+  override def treeTransformPhase = thisTransform.next
+
+  override def transformTemplate(impl: Template)(implicit ctx: Context, info: TransformerInfo) = {
+    val cls = impl.symbol.owner.asClass
+    val ops = new MixinOps(cls, thisTransform)
+    import ops._
+
+    /** Returns the symbol that is accessed by a super-accessor in a mixin composition.
+     *
+     *  @param base       The class in which everything is mixed together
+     *  @param member     The symbol statically referred to by the superaccessor in the trait
+     */
+    def rebindSuper(base: Symbol, acc: Symbol): Symbol = {
+      var bcs = cls.info.baseClasses.dropWhile(acc.owner != _).tail
+      var sym: Symbol = NoSymbol
+      val SuperAccessorName(memberName) = acc.name: Name // dotty deviation: ": Name" needed otherwise pattern type is neither a subtype nor a supertype of selector type
+      ctx.debuglog(i"starting rebindsuper from $cls of ${acc.showLocated}: ${acc.info} in $bcs, name = $memberName")
+      while (bcs.nonEmpty && sym == NoSymbol) {
+        val other = bcs.head.info.nonPrivateDecl(memberName)
+        if (ctx.settings.debug.value)
+          ctx.log(i"rebindsuper ${bcs.head} $other deferred = ${other.symbol.is(Deferred)}")
+        sym = other.matchingDenotation(cls.thisType, cls.thisType.memberInfo(acc)).symbol
+        bcs = bcs.tail
+      }
+      assert(sym.exists)
+      sym
+    }
+
+    def superAccessors(mixin: ClassSymbol): List[Tree] =
+      for (superAcc <- mixin.decls.filter(_ is SuperAccessor).toList)
+        yield polyDefDef(implementation(superAcc.asTerm), forwarder(rebindSuper(cls, superAcc)))
+
+    def methodOverrides(mixin: ClassSymbol): List[Tree] = {
+      def isOverridden(meth: Symbol) = meth.overridingSymbol(cls).is(Method, butNot = Deferred)
+      def needsDisambiguation(meth: Symbol): Boolean =
+        meth.is(Method, butNot = PrivateOrDeferred) &&
+          !isOverridden(meth) &&
+          !meth.allOverriddenSymbols.forall(_ is Deferred)
+      for (meth <- mixin.decls.toList if needsDisambiguation(meth))
+        yield polyDefDef(implementation(meth.asTerm), forwarder(meth))
+    }
+
+    val overrides = mixins.flatMap(mixin => superAccessors(mixin) ::: methodOverrides(mixin))
+
+    cpy.Template(impl)(body = overrides ::: impl.body)
+  }
+  private val PrivateOrDeferred = Private | Deferred
+}