Pattern-bound type refs should have Case flag set

Fixes #6157.

Author: milessabin

compiler/src/dotty/tools/dotc/core/tasty/TreeUnpickler.scala

@@ -513,7 +513,7 @@ class TreeUnpickler(reader: TastyReader,
         def complete(denot: SymDenotation)(implicit ctx: Context) =
           denot.info = typeReader.readType()
       }
-      val sym = ctx.newSymbol(ctx.owner, name, EmptyFlags, completer, coord = coordAt(start))
+      val sym = ctx.newSymbol(ctx.owner, name, Flags.Case, completer, coord = coordAt(start))
       registerSym(start, sym)
       sym
     }

tests/pos/inline-match-separate/inline-match-separate_1.scala

@@ -0,0 +1,6 @@
+object Utils {
+  class Box[T]
+  inline def foo[T](t: T) <: Any = inline t match {
+    case _: Box[a] => scala.compiletime.constValue[a]
+  }
+}

tests/pos/inline-match-separate/inline-match-separate_2.scala

@@ -0,0 +1,5 @@
+import Utils._
+
+object Test {
+  val a = foo(new Box["a"])
+}