SI-9114 Fix crasher in pattern matcher with type aliases

When determining whether or not a pattern match requires an equality
check of the outer instance of a type in addition to a type test,
`needsOuterTest` determines if the intersection of the selector and
the pattern types could be populated. Both type arrive at
`isPopulated` dealised.

However, `isPopulated` recurs when it encounters an existential,
and, as seen in thest case, a failure to dealias the quantified
type can lead to an assertion failure as we try to relate a
typeref to an alias and a typeref to a class.

See also SI-7214, which added deliasing of the pattern type
before calling `isPopulated`.

1 files changed, 1 insertions, 1 deletions

diff --git a/src/reflect/scala/reflect/internal/Types.scala b/src/reflect/scala/reflect/internal/Types.scala
index 92df4ba3af..28b16eeb1a 100644
--- a/src/reflect/scala/reflect/internal/Types.scala
+++ b/src/reflect/scala/reflect/internal/Types.scala
@@ -3891,7 +3891,7 @@ trait Types
    *        any corresponding non-variant type arguments of bt1 and bt2 are the same
    */
   def isPopulated(tp1: Type, tp2: Type): Boolean = {
-    def isConsistent(tp1: Type, tp2: Type): Boolean = (tp1, tp2) match {
+    def isConsistent(tp1: Type, tp2: Type): Boolean = (tp1.dealias, tp2.dealias) match {
       case (TypeRef(pre1, sym1, args1), TypeRef(pre2, sym2, args2)) =>
         assert(sym1 == sym2, (sym1, sym2))
         (    pre1 =:= pre2