[FIR] Property accessors are not part of class initialization

When checking for class val property reassignment diagnostic, property
initializers should be treated as part of the class initialization.
However, property accessors should not. Previously, only the property
itself was checked for both of these situations and resulted in not
reporting diagnostic within property accessors.

#KT-59744 Fixed

compiler/fir/analysis-tests/testData/resolve/cfa/reassignOfNonLocalProperty_initializedProperties.fir.txt

@@ -28,6 +28,33 @@ FILE: reassignOfNonLocalProperty_initializedProperties.kt
         )
             public get(): R|kotlin/String|
 
+        public final var b: R|kotlin/String| = String(hello)
+            public get(): R|kotlin/String| {
+                this@R|/Some|.R|/Some.x| = String(error)
+                this@R|/Some|.R|/y| = String(error)
+                R|/z| = String(error)
+                ^ this@R|/Some|.F|/Some.b|
+            }
+            public set(value: R|kotlin/String|): R|kotlin/Unit| {
+                this@R|/Some|.R|/Some.x| = R|<local>/value|
+                this@R|/Some|.R|/y| = R|<local>/value|
+                R|/z| = R|<local>/value|
+                this@R|/Some|.F|/Some.b| = R|<local>/value|
+            }
+
+        public final var c: R|kotlin/String|
+            public get(): R|kotlin/String| {
+                this@R|/Some|.R|/Some.x| = String(error)
+                this@R|/Some|.R|/y| = String(error)
+                R|/z| = String(error)
+                ^ String(hello)
+            }
+            public set(value: R|kotlin/String|): R|kotlin/Unit| {
+                this@R|/Some|.R|/Some.x| = R|<local>/value|
+                this@R|/Some|.R|/y| = R|<local>/value|
+                R|/z| = R|<local>/value|
+            }
+
         public final fun test_1(): R|kotlin/Unit| {
             this@R|/Some|.R|/Some.x| = String(error)
             this@R|/Some|.R|/y| = String(error)

compiler/fir/analysis-tests/testData/resolve/cfa/reassignOfNonLocalProperty_initializedProperties.kt

@@ -1,4 +1,4 @@
-// ISSUE: KT-55493
+// ISSUE: KT-55493, KT-59744
 // WITH_STDLIB
 
 val z: String = "ok"
@@ -22,6 +22,33 @@ class Some {
         "hello"
     }
 
+    var b: String = "hello"
+        get() {
+            <!VAL_REASSIGNMENT!>x<!> = "error"
+            <!VAL_REASSIGNMENT!>y<!> = "error"
+            <!VAL_REASSIGNMENT!>z<!> = "error"
+            return field
+        }
+        set(value) {
+            <!VAL_REASSIGNMENT!>x<!> = value
+            <!VAL_REASSIGNMENT!>y<!> = value
+            <!VAL_REASSIGNMENT!>z<!> = value
+            field = value
+        }
+
+    var c: String
+        get() {
+            <!VAL_REASSIGNMENT!>x<!> = "error"
+            <!VAL_REASSIGNMENT!>y<!> = "error"
+            <!VAL_REASSIGNMENT!>z<!> = "error"
+            return "hello"
+        }
+        set(value) {
+            <!VAL_REASSIGNMENT!>x<!> = value
+            <!VAL_REASSIGNMENT!>y<!> = value
+            <!VAL_REASSIGNMENT!>z<!> = value
+        }
+
     fun test_1() {
         <!VAL_REASSIGNMENT!>x<!> = "error"
         <!VAL_REASSIGNMENT!>y<!> = "error"

compiler/fir/checkers/src/org/jetbrains/kotlin/fir/analysis/checkers/expression/FirReassignmentAndInvisibleSetterChecker.kt

@@ -148,18 +148,29 @@ object FirReassignmentAndInvisibleSetterChecker : FirVariableAssignmentChecker()
 
     private fun isInOwnersInitializer(receiver: FirExpression, context: CheckerContext): Boolean {
         val uninitializedThisSymbol = (receiver as? FirThisReceiverExpression)?.calleeReference?.boundSymbol ?: return false
-        var foundInitializer = false
-        for ((i, declaration) in context.containingDeclarations.withIndex()) {
-            if (declaration is FirClass) {
-                foundInitializer = if (context.containingDeclarations.getOrNull(i + 1)?.evaluatedInPlace == false) {
-                    // In member function of a class, assume all outer classes are already initialized
-                    // by the time this function is called.
-                    false
-                } else {
-                    foundInitializer || declaration.symbol == uninitializedThisSymbol
+        val containingDeclarations = context.containingDeclarations
+
+        val index = containingDeclarations.indexOfFirst { it is FirClass && it.symbol == uninitializedThisSymbol }
+        if (index == -1) return false
+
+        for (i in index until containingDeclarations.size) {
+            if (containingDeclarations[i] is FirClass) {
+                // Properties need special consideration as some parts are evaluated in-place (initializers) and others are not (accessors).
+                // So it is not enough to just check the FirProperty - which is treated as in-place - but the following declaration needs to
+                // be checked if and only if it is a property accessor.
+                val container = when (val next = containingDeclarations.getOrNull(i + 1)) {
+                    is FirProperty -> containingDeclarations.getOrNull(i + 2)?.takeIf { it is FirPropertyAccessor } ?: next
+                    else -> next
+                }
+
+                // In member function of a class, assume all outer classes are already initialized
+                // by the time this function is called.
+                if (container?.evaluatedInPlace == false) {
+                    return false
                 }
             }
         }
-        return foundInitializer
+
+        return true
     }
 }