Raw FIR: swap branches in when for elvis and bang-bang

compiler/fir/psi2fir/src/org/jetbrains/kotlin/fir/builder/ConversionUtils.kt

@@ -188,18 +188,15 @@ internal fun FirExpression.generateNotNullOrOther(
     ).apply {
         branches += FirWhenBranchImpl(
             session, psi,
-            FirOperatorCallImpl(session, psi, FirOperation.NOT_EQ).apply {
+            FirOperatorCallImpl(session, psi, FirOperation.EQ).apply {
                 arguments += subjectExpression
                 arguments += FirConstExpressionImpl(session, psi, IrConstKind.Null, null)
             },
-            FirSingleExpressionBlock(
-                session,
-                generateAccessExpression(session, psi, subjectName)
-            )
+            FirSingleExpressionBlock(session, other)
         )
         branches += FirWhenBranchImpl(
             session, other.psi, FirElseIfTrueCondition(session, psi),
-            FirSingleExpressionBlock(session, other)
+            FirSingleExpressionBlock(session, generateAccessExpression(session, psi, subjectName))
         )
     }
 }

compiler/fir/psi2fir/testData/rawBuilder/expressions/nullability.txt

@@ -1,22 +1,22 @@
 FILE: nullability.kt
     public? final? fun orFourtyTwo(arg: Int?): <implicit> {
         ^orFourtyTwo when (lval <elvis>: <implicit> = arg#) {
-            !=($subj$, Null(null)) ->  {
-                <elvis>#
+            ==($subj$, Null(null)) ->  {
+                Int(42)
             }
             else ->  {
-                Int(42)
+                <elvis>#
             }
         }
 
     }
     public? final? fun bang(arg: Int?): <implicit> {
         ^bang when (lval <bangbang>: <implicit> = arg#) {
-            !=($subj$, Null(null)) ->  {
-                <bangbang>#
+            ==($subj$, Null(null)) ->  {
+                throw KotlinNullPointerException#()
             }
             else ->  {
-                throw KotlinNullPointerException#()
+                <bangbang>#
             }
         }