Generate super accessor for traits

Otherwise, we will need to support trees like
`C.this.$outer.super[D]` as in Scala 2,
which complicates invariants about super.

Author: liufengyun

compiler/src/dotty/tools/dotc/transform/ResolveSuper.scala

@@ -9,6 +9,8 @@ import SymUtils._
 import Symbols._
 import Decorators._
 import DenotTransformers._
+import Names._
+import StdNames._
 import NameOps._
 import NameKinds._
 import ResolveSuper._
@@ -79,10 +81,20 @@ object ResolveSuper {
   def rebindSuper(base: Symbol, acc: Symbol)(using Context): Symbol = {
     var bcs = base.info.baseClasses.dropWhile(acc.owner != _).tail
     var sym: Symbol = NoSymbol
-    val SuperAccessorName(memberName) = acc.name.unexpandedName
+
+    var mix: Name = nme.EMPTY
+    val memberName = acc.name.unexpandedName match
+      case SuperAccessorName(ExpandPrefixName(name, mixName)) =>
+        mix = mixName.toTypeName
+        name
+      case SuperAccessorName(name) =>
+        name
+
     report.debuglog(i"starting rebindsuper from $base of ${acc.showLocated}: ${acc.info} in $bcs, name = $memberName")
+
     while (bcs.nonEmpty && sym == NoSymbol) {
       val other = bcs.head.info.nonPrivateDecl(memberName)
+        .filterWithPredicate(denot => mix.isEmpty || denot.symbol.owner.name == mix)
         .matchingDenotation(base.thisType, base.thisType.memberInfo(acc))
       report.debuglog(i"rebindsuper ${bcs.head} $other deferred = ${other.symbol.is(Deferred)}")
       if other.exists && !other.symbol.is(Deferred) then

compiler/src/dotty/tools/dotc/transform/SuperAccessors.scala

@@ -5,13 +5,13 @@ import dotty.tools.dotc.ast.{Trees, tpd}
 import scala.collection.mutable
 import ValueClasses.isMethodWithExtension
 import core._
-import Contexts._, Flags._, Symbols._, NameOps._, Trees._, Types.SuperType
+import Contexts._, Flags._, Symbols._, Names._, StdNames._, NameOps._, Trees._
 import TypeUtils._, SymUtils._
 import DenotTransformers.DenotTransformer
 import Symbols._
 import util.Spans._
 import Decorators._
-import NameKinds.SuperAccessorName
+import NameKinds.{ SuperAccessorName, ExpandPrefixName }
 
 /** This class adds super accessors for all super calls that either
  *  appear in a trait or have as a target a member of some outer class.
@@ -62,11 +62,12 @@ class SuperAccessors(thisPhase: DenotTransformer) {
   private val accDefs = newMutableSymbolMap[mutable.ListBuffer[Tree]]
 
   /** A super accessor call corresponding to `sel` */
-  private def superAccessorCall(sel: Select)(using Context) = {
+  private def superAccessorCall(sel: Select, mixName: Name = nme.EMPTY)(using Context) = {
     val Select(qual, name) = sel
     val sym = sel.symbol
     val clazz = qual.symbol.asClass
-    var superName = SuperAccessorName(name.asTermName)
+    val preName = if (mixName.isEmpty) name.toTermName else ExpandPrefixName(name.toTermName, mixName.toTermName)
+    var superName = SuperAccessorName(preName)
     if (clazz.is(Trait)) superName = superName.expandedName(clazz)
     val superInfo = sel.tpe.widenSingleton.ensureMethodic
 
@@ -147,19 +148,14 @@ class SuperAccessors(thisPhase: DenotTransformer) {
         }
     }
 
-    def mixIsTrait = sup.tpe match {
-      case SuperType(thisTpe, superTpe) => superTpe.typeSymbol.is(Trait)
-    }
-
     val needAccessor = name.isTermName && {
       mix.name.isEmpty && (clazz.is(Trait) || clazz != currentClass || !validCurrentClass) ||
       // SI-8803. If we access super[A] from an inner class (!= currentClass) or closure (validCurrentClass),
-      // where A is the superclass we need an accessor. If A is a parent trait we don't: in this case mixin
-      // will re-route the super call directly to the impl class (it's statically known).
-      !mix.name.isEmpty && (clazz != currentClass || !validCurrentClass) && !mixIsTrait
+      // where A is the superclass we need an accessor.
+      !mix.name.isEmpty && (clazz != currentClass || !validCurrentClass)
     }
 
-    if (needAccessor) atPhase(thisPhase.next)(superAccessorCall(sel))
+    if (needAccessor) atPhase(thisPhase.next)(superAccessorCall(sel, mix.name))
     else sel
   }
 

tests/run/t10290.scala

@@ -21,8 +21,8 @@ object Test {
   def main(args : Array[String]) : Unit = {
     val b = new B
     val c = new b.C
-    assert(c.t1 == "A1")
-    assert(c.t2 == "A2")
-    assert(c.t3 == "B")
+    assert(c.t1 == "A1", c.t1)
+    assert(c.t2 == "A2", c.t2)
+    assert(c.t3 == "B", c.t3)
   }
 }