Merge pull request #3242 from retronym/ticket/8046

SI-8046 BaseTypeSeq fixes with aliases

2 files changed, 14 insertions, 4 deletions

diff --git a/src/reflect/scala/reflect/internal/BaseTypeSeqs.scala b/src/reflect/scala/reflect/internal/BaseTypeSeqs.scala
index 19c67879f5..0ca8611719 100644
--- a/src/reflect/scala/reflect/internal/BaseTypeSeqs.scala
+++ b/src/reflect/scala/reflect/internal/BaseTypeSeqs.scala
@@ -166,9 +166,10 @@ trait BaseTypeSeqs {
       val index = new Array[Int](nparents)
       var i = 0
       for (p <- parents) {
+        val parentBts = p.dealias.baseTypeSeq // dealias need for SI-8046.
         pbtss(i) =
-          if (p.baseTypeSeq eq undetBaseTypeSeq) AnyClass.info.baseTypeSeq
-          else p.baseTypeSeq
+          if (parentBts eq undetBaseTypeSeq) AnyClass.info.baseTypeSeq
+          else parentBts
         index(i) = 0
         i += 1
       }
diff --git a/src/reflect/scala/reflect/internal/Types.scala b/src/reflect/scala/reflect/internal/Types.scala
index d8bbd981b9..e9230aceee 100644
--- a/src/reflect/scala/reflect/internal/Types.scala
+++ b/src/reflect/scala/reflect/internal/Types.scala
@@ -1998,7 +1998,9 @@ trait Types
       if (sym.typeParams.size != args.size)
         devWarning(s"$this.transform($tp), but tparams.isEmpty and args=$args")
 
-      asSeenFromOwner(tp).instantiateTypeParams(sym.typeParams, args)
+      val GenPolyType(tparams, result) = asSeenFromOwner(tp)
+      assert((tparams eq Nil) || tparams == sym.typeParams, (tparams, sym.typeParams))
+      result.instantiateTypeParams(sym.typeParams, args)
     }
 
     // note: does not go through typeRef. There's no need to because
@@ -2308,7 +2310,14 @@ trait Types
       }
       thisInfo.decls
     }
-    protected[Types] def baseTypeSeqImpl: BaseTypeSeq = sym.info.baseTypeSeq map transform
+    protected[Types] def baseTypeSeqImpl: BaseTypeSeq =
+      if (sym.info.baseTypeSeq exists (_.typeSymbolDirect.isAbstractType))
+        // SI-8046 base type sequence might have more elements in a subclass, we can't map it element wise.
+        transform(sym.info).baseTypeSeq
+      else
+        // Optimization: no abstract types, we can compute the BTS of this TypeRef as an element-wise map
+        //               of the BTS of the referenced symbol.
+        sym.info.baseTypeSeq map transform
 
     override def baseTypeSeq: BaseTypeSeq = {
       val cache = baseTypeSeqCache