Fix tests in Ycheck

Author: noti0na1

compiler/src/dotty/tools/dotc/transform/patmat/Space.scala

@@ -323,12 +323,6 @@ class SpaceEngine(using Context) extends SpaceLogic {
 
   private val constantNullType     = ConstantType(Constant(null))
 
-  /** Does the given tree stand for the literal `null`? */
-  def isNullLit(tree: Tree): Boolean = tree match {
-    case Literal(Constant(null)) => true
-    case _ => false
-  }
-
   override def intersectUnrelatedAtomicTypes(tp1: Type, tp2: Type): Space = trace(s"atomic intersection: ${AndType(tp1, tp2).show}", debug) {
     // Precondition: !isSubType(tp1, tp2) && !isSubType(tp2, tp1).
     if !ctx.mode.is(Mode.SafeNulls) && (tp1.isNullType || tp2.isNullType) then

compiler/src/dotty/tools/dotc/typer/Typer.scala

@@ -1581,7 +1581,7 @@ class Typer extends Namer
             result
         }
     }
-    if Nullables.unsafeNullsEnabled then
+    if Nullables.unsafeNullsEnabled && ctx.phase == Phases.typerPhase then
       tree1.putAttachment(Nullables.UnsafeNullsMatch, ())
     tree1
 

compiler/test/dotty/tools/dotc/CompilationTests.scala

@@ -322,6 +322,7 @@ class CompilationTests {
     aggregateTests(
       compileFilesInDir("tests/explicit-nulls/pos", explicitNullsOptions),
       compileFilesInDir("tests/explicit-nulls/pos-separate", explicitNullsOptions),
+      compileFilesInDir("tests/explicit-nulls/pos-patmat", explicitNullsOptions and "-Xfatal-warnings"),
       compileFilesInDir("tests/explicit-nulls/unsafe-common", explicitNullsOptions and "-language:unsafeNulls"),
     )
   }.checkCompile()