[FE 1.0] Don't report UNUSED_* warnings on local properties with delegate

^KT-25527 Fixed

analysis/low-level-api-fir/tests/org/jetbrains/kotlin/analysis/low/level/api/fir/diagnostic/compiler/based/DiagnosisCompilerTestFE10TestdataTestGenerated.java

@@ -5944,6 +5944,12 @@ public class DiagnosisCompilerTestFE10TestdataTestGenerated extends AbstractDiag
                 runTest("compiler/testData/diagnostics/tests/controlFlowAnalysis/unresolvedReference.kt");
             }
 
+            @Test
+            @TestMetadata("unusedPropertyWithCustomAccessors.kt")
+            public void testUnusedPropertyWithCustomAccessors() throws Exception {
+                runTest("compiler/testData/diagnostics/tests/controlFlowAnalysis/unusedPropertyWithCustomAccessors.kt");
+            }
+
             @Test
             @TestMetadata("useUninitializedInLambda.kt")
             public void testUseUninitializedInLambda() throws Exception {

compiler/fir/analysis-tests/tests-gen/org/jetbrains/kotlin/test/runners/FirOldFrontendDiagnosticsTestGenerated.java

@@ -5944,6 +5944,12 @@ public class FirOldFrontendDiagnosticsTestGenerated extends AbstractFirDiagnosti
                 runTest("compiler/testData/diagnostics/tests/controlFlowAnalysis/unresolvedReference.kt");
             }
 
+            @Test
+            @TestMetadata("unusedPropertyWithCustomAccessors.kt")
+            public void testUnusedPropertyWithCustomAccessors() throws Exception {
+                runTest("compiler/testData/diagnostics/tests/controlFlowAnalysis/unusedPropertyWithCustomAccessors.kt");
+            }
+
             @Test
             @TestMetadata("useUninitializedInLambda.kt")
             public void testUseUninitializedInLambda() throws Exception {

compiler/fir/analysis-tests/tests-gen/org/jetbrains/kotlin/test/runners/FirOldFrontendDiagnosticsWithLightTreeTestGenerated.java

@@ -5944,6 +5944,12 @@ public class FirOldFrontendDiagnosticsWithLightTreeTestGenerated extends Abstrac
                 runTest("compiler/testData/diagnostics/tests/controlFlowAnalysis/unresolvedReference.kt");
             }
 
+            @Test
+            @TestMetadata("unusedPropertyWithCustomAccessors.kt")
+            public void testUnusedPropertyWithCustomAccessors() throws Exception {
+                runTest("compiler/testData/diagnostics/tests/controlFlowAnalysis/unusedPropertyWithCustomAccessors.kt");
+            }
+
             @Test
             @TestMetadata("useUninitializedInLambda.kt")
             public void testUseUninitializedInLambda() throws Exception {

compiler/frontend/cfg/src/org/jetbrains/kotlin/cfg/ControlFlowInformationProviderImpl.kt

@@ -676,7 +676,9 @@ class ControlFlowInformationProviderImpl private constructor(
             when (expressionInQuestion) {
                 is KtBinaryExpression -> if (expressionInQuestion.operationToken === KtTokens.EQ) {
                     expressionInQuestion.right?.let {
-                        report(Errors.UNUSED_VALUE.on(expressionInQuestion, it, variableDescriptor), ctxt)
+                        if (!variableDescriptor.isLocalVariableWithDelegate) {
+                            report(Errors.UNUSED_VALUE.on(expressionInQuestion, it, variableDescriptor), ctxt)
+                        }
                     }
                 }
                 is KtPostfixExpression -> {
@@ -689,6 +691,9 @@ class ControlFlowInformationProviderImpl private constructor(
         }
     }
 
+    private val VariableDescriptor.isLocalVariableWithDelegate: Boolean
+        get() = this is LocalVariableDescriptor && this.isDelegated
+
     private fun processUnusedDeclaration(
         element: KtNamedDeclaration,
         variableDescriptor: VariableDescriptor,
@@ -710,7 +715,9 @@ class ControlFlowInformationProviderImpl private constructor(
                     processUnusedParameter(ctxt, element, variableDescriptor)
             }
         } else if (variableUseState === ONLY_WRITTEN_NEVER_READ && KtPsiUtil.isRemovableVariableDeclaration(element)) {
-            report(Errors.ASSIGNED_BUT_NEVER_ACCESSED_VARIABLE.on(element, variableDescriptor), ctxt)
+            if (!variableDescriptor.isLocalVariableWithDelegate) {
+                report(Errors.ASSIGNED_BUT_NEVER_ACCESSED_VARIABLE.on(element, variableDescriptor), ctxt)
+            }
         } else if (variableUseState === WRITTEN_AFTER_READ && element is KtVariableDeclaration) {
             when (element) {
                 is KtProperty ->

compiler/testData/diagnostics/tests/controlFlowAnalysis/unusedPropertyWithCustomAccessors.fir.kt

@@ -0,0 +1,40 @@
+// ISSUE: KT-25527
+
+import kotlin.reflect.KProperty
+
+fun test_1(delegate: Delegate) {
+    var p1 by delegate
+    p1 = 10
+
+    var p2 by delegate
+    p2++
+
+    var p3 by delegate
+    ++p3
+}
+
+fun test_2() {
+    var p1 = 0
+    p1 = 10
+
+    var p2: Int
+    p2 = 10
+
+    var p3 = 1
+    p3++
+
+    var p4 = 1
+    ++p4
+}
+
+class Delegate {
+    var prop: Int = 0
+
+    operator fun getValue(thisRef: Any?, property: KProperty<*>): Int {
+        return prop
+    }
+
+    operator fun setValue(thisRef: Any?, property: KProperty<*>, value: Int) {
+        prop = value
+    }
+}

compiler/testData/diagnostics/tests/controlFlowAnalysis/unusedPropertyWithCustomAccessors.kt

@@ -0,0 +1,40 @@
+// ISSUE: KT-25527
+
+import kotlin.reflect.KProperty
+
+fun test_1(delegate: Delegate) {
+    var p1 by delegate
+    p1 = 10
+
+    var p2 by delegate
+    <!UNUSED_CHANGED_VALUE!>p2++<!>
+
+    var p3 by delegate
+    ++p3
+}
+
+fun test_2() {
+    var <!ASSIGNED_BUT_NEVER_ACCESSED_VARIABLE!>p1<!> = 0
+    <!UNUSED_VALUE!>p1 =<!> 10
+
+    var <!ASSIGNED_BUT_NEVER_ACCESSED_VARIABLE!>p2<!>: Int
+    <!UNUSED_VALUE!>p2 =<!> 10
+
+    var p3 = 1
+    <!UNUSED_CHANGED_VALUE!>p3++<!>
+
+    var p4 = 1
+    ++p4
+}
+
+class Delegate {
+    var prop: Int = 0
+
+    operator fun getValue(thisRef: Any?, property: KProperty<*>): Int {
+        return prop
+    }
+
+    operator fun setValue(thisRef: Any?, property: KProperty<*>, value: Int) {
+        prop = value
+    }
+}

compiler/testData/diagnostics/tests/controlFlowAnalysis/unusedPropertyWithCustomAccessors.txt

@@ -0,0 +1,14 @@
+package
+
+public fun test_1(/*0*/ delegate: Delegate): kotlin.Unit
+public fun test_2(): kotlin.Unit
+
+public final class Delegate {
+    public constructor Delegate()
+    public final var prop: kotlin.Int
+    public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public final operator fun getValue(/*0*/ thisRef: kotlin.Any?, /*1*/ property: kotlin.reflect.KProperty<*>): kotlin.Int
+    public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    public final operator fun setValue(/*0*/ thisRef: kotlin.Any?, /*1*/ property: kotlin.reflect.KProperty<*>, /*2*/ value: kotlin.Int): kotlin.Unit
+    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+}

compiler/tests-common-new/tests-gen/org/jetbrains/kotlin/test/runners/DiagnosticTestGenerated.java

@@ -5950,6 +5950,12 @@ public class DiagnosticTestGenerated extends AbstractDiagnosticTest {
                 runTest("compiler/testData/diagnostics/tests/controlFlowAnalysis/unresolvedReference.kt");
             }
 
+            @Test
+            @TestMetadata("unusedPropertyWithCustomAccessors.kt")
+            public void testUnusedPropertyWithCustomAccessors() throws Exception {
+                runTest("compiler/testData/diagnostics/tests/controlFlowAnalysis/unusedPropertyWithCustomAccessors.kt");
+            }
+
             @Test
             @TestMetadata("useUninitializedInLambda.kt")
             public void testUseUninitializedInLambda() throws Exception {