SI-8046 Only use fast TypeRef#baseTypeSeq with concrete base types

We can only compute the base type sequence (BTS) of a `TypeRef` by
element-wise transforming the BTS of the referenced symbol if
there are no abstract types in its BTS type symbols.

In the now-working test case, `pos/t8046.scala`, the difference
between the old and new calculation of the BTS is:

    this                 = Three.this.Alias[Int]
    sym.info.baseTypeSeq = BTS(One.this.Op[A],Any)
    mapped BTS           = BTS(Three.this.Op[Int],Any)
    full BTS             = BTS(Three.this.Op[Int],Int => Int,Object,Any)

The change to account for PolyType in ArgsTypeRef#transform is now
needed to avoid the full BTS of:

    BTS(Three.this.Op[A],A => A,Object,Any)

Interestingly, everything actually works without that change.

1 files changed, 0 insertions, 19 deletions

diff --git a/test/pending/pos/t8046c.scala b/test/pending/pos/t8046c.scala
deleted file mode 100644
index 9a8616828d..0000000000
--- a/test/pending/pos/t8046c.scala
+++ /dev/null
@@ -1,19 +0,0 @@
-trait One {
-  type Op[A]
-  type Alias[A] = Op[A]
-}
-
-trait Three extends One {
-  trait Op[A] extends (A => A)
- 
-  def f1(f: Op[Int])            = f(5)
-  def f2(f: Alias[Int])         = f(5)
-  def f3[T <: Op[Int]](f: T)    = f(5)
-  def f4[T <: Alias[Int]](f: T) = f(5)
-  // ./a.scala:12: error: type mismatch;
-  //  found   : Int(5)
-  //  required: T1
-  //   def f4[T <: Alias[Int]](f: T) = f(5)
-  //                                     ^
-}
-