Always compute asSeenFroms on opaque companion members

For a member of an opaque companion C, it makes a difference whether
the prefix is C or C.this - opaque aliases are visible for C.this but
not for C. So we can never omit an asSeenFrom on these members.

Author: odersky

compiler/src/dotty/tools/dotc/core/SymDenotations.scala

@@ -762,9 +762,10 @@ object SymDenotations {
      */
     def membersNeedAsSeenFrom(pre: Type)(implicit ctx: Context): Boolean =
       !(  this.isTerm
-       || this.isStaticOwner
+       || this.isStaticOwner && !this.isOpaqueCompanion
        || ctx.erasedTypes
-       || (pre eq NoPrefix) || (pre eq thisType)
+       || (pre eq NoPrefix)
+       || (pre eq thisType)
        )
 
     /** Is this symbol concrete, or that symbol deferred? */

compiler/src/dotty/tools/dotc/core/TypeOps.scala

@@ -53,7 +53,7 @@ trait TypeOps { this: Context => // TODO: Make standalone object.
         tp match {
           case tp: NamedType =>
             val sym = tp.symbol
-            if (sym.isStatic || (tp.prefix `eq` NoPrefix)) tp
+            if (sym.isStatic && !sym.maybeOwner.isOpaqueCompanion || (tp.prefix `eq` NoPrefix)) tp
             else derivedSelect(tp, atVariance(variance max 0)(this(tp.prefix)))
           case tp: ThisType =>
             toPrefix(pre, cls, tp.cls)