Work around scala/scala3#19237

It does not seem that the upstream issue will be fixed any time
soon due to binary compatibility concerns. Nevertheless, it makes
no sense, and it is not possible possible to create a *value* of
a "package type".

Therefore, we work around the issue by tolerating a `PackageRef`
as the type of a PARAM of an inline accessor method. We replace it
by `Nothing`, which matches the fact that no value can be created
for it.

Note that the *signature* and therefore the *signed name* of such
a method will be different from what dotc computes, so it will
still be semantically broken.

tasty-query/shared/src/main/scala/tastyquery/reader/tasties/TreeUnpickler.scala

@@ -759,10 +759,19 @@ private[tasties] class TreeUnpickler private (
       else if tag == VALDEF then Some(readTermOrUninitialized())
       else Some(readTerm)
     readAnnotationsInModifiers(symbol, end)
+
     tag match {
       case VALDEF | PARAM =>
-        symbol.withDeclaredType(tpt.toType)
+        val tpe: Type = tpt.toPrefix match
+          case tpe: Type =>
+            tpe
+          case packageRef: PackageRef =>
+            // Work around https://github.com/lampepfl/dotty/issues/19237
+            if tag == PARAM && symbol.owner.name.isInstanceOf[InlineAccessorName] then rctx.NothingType
+            else throw TastyFormatException(s"unexpected type $packageRef for $symbol in $posErrorMsg")
+        symbol.withDeclaredType(tpe)
         definingTree(symbol, ValDef(name, tpt, rhs, symbol)(spn))
+
       case DEFDEF =>
         val normalizedParams =
           if name == nme.Constructor then normalizeCtorParamClauses(params)