Don't simplify lubs when unpickling Ifs

I was not able to find out why that's the case, but the original test case with the import in the function body requires that if's are _not_ simplified by Unpickler. The interaction with lubs and unsafenulls seems to be very tricky. Anyway, we now have two versions of all test cases, with local as well as globak unsafe nulls.

Author: odersky

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

@@ -1236,13 +1236,12 @@ class TreeUnpickler(reader: TastyReader,
  val expansion = exprReader.readTerm() // need bindings in scope, so needs to be read before
  Inlined(call, bindings, expansion)
  case IF =>
- simplifyLub(
- if (nextByte == INLINE) {
- readByte()
- InlineIf(readTerm(), readTerm(), readTerm())
- }
- else
- If(readTerm(), readTerm(), readTerm()))
+ if (nextByte == INLINE) {
+ readByte()
+ InlineIf(readTerm(), readTerm(), readTerm())
+ }
+ else
+ If(readTerm(), readTerm(), readTerm())
  case LAMBDA =>
  val meth = readTerm()
  val tpt = ifBefore(end)(readTpt(), EmptyTree)

tests/pos/i15097.scala

@@ -1,13 +1,30 @@
-import scala.language.unsafeNulls
-class C {
+class C:
  def g: String | Null = ???
 
  def f =
+ import scala.language.unsafeNulls
  try g catch case _ => ""
 
- def f2 = if ??? then g else ""
+ def f2 =
+ import scala.language.unsafeNulls
+ if ??? then g else ""
 
- def f3 = (??? : Boolean) match
+ def f3 =
+ (??? : Boolean) match
+ case true => g
+ case _ => ""
+
+class C2:
+ import scala.language.unsafeNulls
+ def g: String | Null = ???
+
+ def f =
+ try g catch case _ => ""
+
+ def f2 =
+ if ??? then g else ""
+
+ def f3 =
+ (??? : Boolean) match
  case true => g
  case _ => ""
-}