[FIR] Track inc and dec operator calls in preliminary loop visitor, ^KT-44879 Fixed

compiler/fir/resolve/src/org/jetbrains/kotlin/fir/resolve/dfa/PreliminaryLoopVisitor.kt

@@ -5,6 +5,7 @@
 
 package org.jetbrains.kotlin.fir.resolve.dfa
 
+import org.jetbrains.kotlin.KtFakeSourceElementKind
 import org.jetbrains.kotlin.fir.FirElement
 import org.jetbrains.kotlin.fir.declarations.*
 import org.jetbrains.kotlin.fir.expressions.*
@@ -41,6 +42,8 @@ class PreliminaryLoopVisitor {
         }
 
         override fun visitVariableAssignment(variableAssignment: FirVariableAssignment, data: FirStatement?) {
+            if (variableAssignment.source?.kind == KtFakeSourceElementKind.DesugaredIncrementOrDecrement) return
+
             val reference = variableAssignment.lValue as? FirNamedReference
             if (reference != null) {
                 requireNotNull(data)

compiler/testData/diagnostics/tests/smartCasts/variables/varNotChangedInLoop.fir.kt

@@ -2,7 +2,7 @@ public fun foo() {
     var i: Any = 1
     if (i is Int) {
         while (i != 10) {
-            i<!UNRESOLVED_REFERENCE!>++<!>
+            i++
         }
     }
 }

compiler/testData/diagnostics/tests/smartCasts/varnotnull/varNotChangedInLoop.fir.kt

@@ -2,7 +2,7 @@ public fun foo() {
     var i: Int? = 1
     if (i != null) {
         while (i != 10) {
-            i<!UNSAFE_CALL!>++<!>
+            i++
         }
     }
 }