[FIR] Ignore nullability in the definition of "identity-less"

The definition of a "builtin" already
ignores nullability.

`Int? === String?` must trigger a
diagnostic by design.

compiler/fir/analysis-tests/testData/resolve/smartcasts/nullability.kt

@@ -123,7 +123,7 @@ fun test_10(a: Int?, b: Int?) {
     }
     b<!UNSAFE_CALL!>.<!>inc()
 
-    if (a === b) {
+    if (<!FORBIDDEN_IDENTITY_EQUALS_WARNING!>a === b<!>) {
         b<!UNSAFE_CALL!>.<!>inc()
     }
     b<!UNSAFE_CALL!>.<!>inc()
@@ -133,7 +133,7 @@ fun test_10(a: Int?, b: Int?) {
     }
     b<!UNSAFE_CALL!>.<!>inc()
 
-    if (b === a) {
+    if (<!FORBIDDEN_IDENTITY_EQUALS_WARNING!>b === a<!>) {
         b<!UNSAFE_CALL!>.<!>inc()
     }
     b<!UNSAFE_CALL!>.<!>inc()

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

@@ -121,15 +121,15 @@ object FirEqualityCompatibilityChecker : FirEqualityOperatorCallChecker() {
         // we only need to check if one is related
         // to the other
 
-        fun TypeInfo.isSubtypeOf(other: TypeInfo) =
-            notNullType.isSubtypeOf(other.notNullType, context.session)
-
         return when {
             l.type.isNothingOrNullableNothing || r.type.isNothingOrNullableNothing -> false
-            else -> !l.isSubtypeOf(r) && !r.isSubtypeOf(l)
+            else -> !l.isSubtypeOf(r, context) && !r.isSubtypeOf(l, context)
         }
     }
 
+    private fun TypeInfo.isSubtypeOf(other: TypeInfo, context: CheckerContext) =
+        notNullType.isSubtypeOf(other.notNullType, context.session)
+
     private enum class Applicability {
         APPLICABLE,
         GENERALLY_INAPPLICABLE,
@@ -153,12 +153,13 @@ object FirEqualityCompatibilityChecker : FirEqualityOperatorCallChecker() {
         forceWarning: Boolean,
         context: CheckerContext,
     ): KtDiagnosticFactory2<ConeKotlinType, ConeKotlinType> {
-        val areBothPrimitives = l.isPrimitive && r.isPrimitive
+        val areBothPrimitives = l.isNotNullPrimitive && r.isNotNullPrimitive
         val areSameTypes = l.type.classId == r.type.classId
         val shouldProperlyReportError = context.languageVersionSettings.supportsFeature(LanguageFeature.ReportErrorsForComparisonOperators)
 
         // In this case K1 reports nothing
-        val shouldRelaxDiagnostic = (l.type.isNullableNothing || r.type.isNullableNothing) && !shouldProperlyReportError
+        val shouldRelaxDiagnostic = (l.isPrimitive || r.isPrimitive) && (l.isSubtypeOf(r, context) || r.isSubtypeOf(l, context))
+                && !shouldProperlyReportError
 
         return when {
             // See: KT-28252
@@ -174,7 +175,7 @@ object FirEqualityCompatibilityChecker : FirEqualityOperatorCallChecker() {
         isPrimitiveWithNonPrimitiveSupertype(l, r, session) || isPrimitiveWithNonPrimitiveSupertype(r, l, session)
 
     private fun isPrimitiveWithNonPrimitiveSupertype(l: TypeInfo, r: TypeInfo, session: FirSession) =
-        l.isPrimitive && !r.isPrimitive && l.type.isSubtypeOf(r.type, session)
+        l.isNotNullPrimitive && !r.isNotNullPrimitive && l.type.isSubtypeOf(r.type, session)
 
     private fun getSourceLessInapplicabilityDiagnostic(forceWarning: Boolean) = when {
         forceWarning -> FirErrors.INCOMPATIBLE_TYPES_WARNING
@@ -298,7 +299,9 @@ private val TypeInfo.enforcesEmptyIntersection get() = isFinalClass && !isEnumCl
 
 private val TypeInfo.isNullableEnum get() = isEnumClass && type.isNullable
 
-private val TypeInfo.isIdentityLess get() = isPrimitive || !type.isNullable && isValueClass
+private val TypeInfo.isIdentityLess get() = isPrimitive || isValueClass
+
+private val TypeInfo.isNotNullPrimitive get() = isPrimitive && !type.isNullable
 
 private val FirClassSymbol<*>.isFinalClass get() = isClass && isFinal
 
@@ -315,7 +318,7 @@ private fun ConeKotlinType.toTypeInfo(session: FirSession): TypeInfo {
         type, notNullType,
         isFinalClass = bounds.any { it.toClassSymbol(session)?.isFinalClass == true },
         isEnumClass = bounds.any { it.toClassSymbol(session)?.isEnumClass == true },
-        isPrimitive = bounds.any { it.isPrimitive },
+        isPrimitive = bounds.any { it.isPrimitiveOrNullablePrimitive },
         isBuiltin = bounds.any { it.toClassSymbol(session)?.isBuiltin == true },
         isValueClass = bounds.any { it.toClassSymbol(session)?.isInline == true },
         isLiterallyTypeParameter = this.lowerBoundIfFlexible() is ConeTypeParameterType,

compiler/testData/diagnostics/tests/BinaryCallsOnNullableValues.fir.kt

@@ -15,8 +15,8 @@ fun f(): Unit {
 
     <!EQUALITY_NOT_APPLICABLE!>A() == 1<!>
 
-    <!EQUALITY_NOT_APPLICABLE!>x === "1"<!>
+    <!FORBIDDEN_IDENTITY_EQUALS!>x === "1"<!>
-    <!EQUALITY_NOT_APPLICABLE!>x !== "1"<!>
+    <!FORBIDDEN_IDENTITY_EQUALS!>x !== "1"<!>
 
     <!IMPLICIT_BOXING_IN_IDENTITY_EQUALS!>x === 1<!>
     <!IMPLICIT_BOXING_IN_IDENTITY_EQUALS!>x !== 1<!>

compiler/testData/diagnostics/tests/inference/builderInference/stubTypes/memberScope.fir.kt

@@ -54,7 +54,7 @@ fun test() {
         x?.<!NONE_APPLICABLE!>equals<!>(1)
 
         if (get() == null) {}
-        if (get() === null) {}
+        if (<!FORBIDDEN_IDENTITY_EQUALS_WARNING!>get() === null<!>) {}
 
         if (x != null) {
             x<!UNNECESSARY_SAFE_CALL!>?.<!>hashCode()
@@ -113,7 +113,7 @@ fun test() {
         emit(1)
         emit(null)
         val x = get()
-        if (x === null) {
+        if (<!FORBIDDEN_IDENTITY_EQUALS_WARNING!>x === null<!>) {
             x.hashCode()
         }
 
@@ -123,7 +123,7 @@ fun test() {
         emit(1)
         emit(null)
         val x = get()
-        if (x === null) {
+        if (<!FORBIDDEN_IDENTITY_EQUALS_WARNING!>x === null<!>) {
             x.equals("")
         }
 
@@ -133,7 +133,7 @@ fun test() {
         emit(1)
         emit(null)
         val x = get()
-        if (x === null) {
+        if (<!FORBIDDEN_IDENTITY_EQUALS_WARNING!>x === null<!>) {
             x<!UNSAFE_CALL!>.<!>toString("")
         }
 
@@ -143,7 +143,7 @@ fun test() {
         emit(1)
         emit(null)
         val x = get()
-        if (x === null) {
+        if (<!FORBIDDEN_IDENTITY_EQUALS_WARNING!>x === null<!>) {
             x<!UNSAFE_CALL!>.<!>test()
         }
 
@@ -170,7 +170,7 @@ fun test() {
         x?.<!NONE_APPLICABLE!>equals<!>(1)
 
         if (get() == null) {}
-        if (get() === null) {}
+        if (<!FORBIDDEN_IDENTITY_EQUALS_WARNING!>get() === null<!>) {}
 
         if (x == null) {
             x?.hashCode()
@@ -188,19 +188,19 @@ fun test() {
             x.test2()
         }
 
-        if (x === null) {
+        if (<!FORBIDDEN_IDENTITY_EQUALS_WARNING!>x === null<!>) {
             x?.hashCode()
         }
 
-        if (x === null) {
+        if (<!FORBIDDEN_IDENTITY_EQUALS_WARNING!>x === null<!>) {
             x?.<!NONE_APPLICABLE!>equals<!>(1)
         }
 
-        if (x === null) {
+        if (<!FORBIDDEN_IDENTITY_EQUALS_WARNING!>x === null<!>) {
             x?.test2()
         }
 
-        if (x === null) {
+        if (<!FORBIDDEN_IDENTITY_EQUALS_WARNING!>x === null<!>) {
             x.test2()
         }
 
@@ -247,7 +247,7 @@ fun test() {
         emit(1)
         emit(null)
         val x = get()
-        if (x === null) {
+        if (<!FORBIDDEN_IDENTITY_EQUALS_WARNING!>x === null<!>) {
             x.equals("")
         }
 
@@ -257,7 +257,7 @@ fun test() {
         emit(1)
         emit(null)
         val x = get()
-        if (x === null) {
+        if (<!FORBIDDEN_IDENTITY_EQUALS_WARNING!>x === null<!>) {
             x.hashCode()
         }
         ""
@@ -266,7 +266,7 @@ fun test() {
         emit(1)
         emit(null)
         val x = get()
-        if (x === null) {
+        if (<!FORBIDDEN_IDENTITY_EQUALS_WARNING!>x === null<!>) {
             x.toString()
         }
         ""
@@ -275,7 +275,7 @@ fun test() {
         emit(1)
         emit(null)
         val x = get()
-        if (x === null) {
+        if (<!FORBIDDEN_IDENTITY_EQUALS_WARNING!>x === null<!>) {
             x<!UNSAFE_CALL!>.<!>test()
         }
         ""
@@ -300,7 +300,7 @@ fun test() {
         x?.<!NONE_APPLICABLE!>equals<!>(1)
 
         if (get() == null) {}
-        if (get() === null) {}
+        if (<!FORBIDDEN_IDENTITY_EQUALS_WARNING!>get() === null<!>) {}
 
         if (x == null) {
             x?.hashCode()

compiler/testData/diagnostics/tests/inlineClasses/identityComparisonWithInlineClasses.fir.kt

@@ -9,7 +9,7 @@ fun test(f1: Foo, f2: Foo, b1: Bar, fn1: Foo?, fn2: Foo?) {
     val a2 = <!FORBIDDEN_IDENTITY_EQUALS!>f1 === f1<!>
     val a3 = <!FORBIDDEN_IDENTITY_EQUALS!>f1 === b1<!> || <!FORBIDDEN_IDENTITY_EQUALS!>f1 !== b1<!>
 
-    val c1 = fn1 === fn2 || fn1 !== fn2
+    val c1 = <!FORBIDDEN_IDENTITY_EQUALS!>fn1 === fn2<!> || <!FORBIDDEN_IDENTITY_EQUALS!>fn1 !== fn2<!>
     val c2 = <!FORBIDDEN_IDENTITY_EQUALS!>f1 === fn1<!> || <!FORBIDDEN_IDENTITY_EQUALS!>f1 !== fn1<!>
     val c3 = <!FORBIDDEN_IDENTITY_EQUALS!>b1 === fn1<!> || <!FORBIDDEN_IDENTITY_EQUALS!>b1 !== fn1<!>
 
@@ -17,6 +17,6 @@ fun test(f1: Foo, f2: Foo, b1: Bar, fn1: Foo?, fn2: Foo?) {
 
     val d1 = <!FORBIDDEN_IDENTITY_EQUALS!>any === f1<!> || <!FORBIDDEN_IDENTITY_EQUALS!>any !== f1<!>
     val d2 = <!FORBIDDEN_IDENTITY_EQUALS!>f1 === any<!> || <!FORBIDDEN_IDENTITY_EQUALS!>f1 !== any<!>
-    val d3 = any === fn1 || any !== fn1
+    val d3 = <!FORBIDDEN_IDENTITY_EQUALS!>any === fn1<!> || <!FORBIDDEN_IDENTITY_EQUALS!>any !== fn1<!>
-    val d4 = fn1 === any || fn1 !== any
+    val d4 = <!FORBIDDEN_IDENTITY_EQUALS!>fn1 === any<!> || <!FORBIDDEN_IDENTITY_EQUALS!>fn1 !== any<!>
 }

compiler/testData/diagnostics/tests/valueClasses/identityComparisonWithValueClasses.fir.kt

@@ -17,7 +17,7 @@ fun test(f1: Foo, f2: Foo, b1: Bar, fn1: Foo?, fn2: Foo?) {
     val a2 = <!FORBIDDEN_IDENTITY_EQUALS!>f1 === f1<!>
     val a3 = <!FORBIDDEN_IDENTITY_EQUALS!>f1 === b1<!> || <!FORBIDDEN_IDENTITY_EQUALS!>f1 !== b1<!>
 
-    val c1 = fn1 === fn2 || fn1 !== fn2
+    val c1 = <!FORBIDDEN_IDENTITY_EQUALS!>fn1 === fn2<!> || <!FORBIDDEN_IDENTITY_EQUALS!>fn1 !== fn2<!>
     val c2 = <!FORBIDDEN_IDENTITY_EQUALS!>f1 === fn1<!> || <!FORBIDDEN_IDENTITY_EQUALS!>f1 !== fn1<!>
     val c3 = <!FORBIDDEN_IDENTITY_EQUALS!>b1 === fn1<!> || <!FORBIDDEN_IDENTITY_EQUALS!>b1 !== fn1<!>
 
@@ -25,6 +25,6 @@ fun test(f1: Foo, f2: Foo, b1: Bar, fn1: Foo?, fn2: Foo?) {
 
     val d1 = <!FORBIDDEN_IDENTITY_EQUALS!>any === f1<!> || <!FORBIDDEN_IDENTITY_EQUALS!>any !== f1<!>
     val d2 = <!FORBIDDEN_IDENTITY_EQUALS!>f1 === any<!> || <!FORBIDDEN_IDENTITY_EQUALS!>f1 !== any<!>
-    val d3 = any === fn1 || any !== fn1
+    val d3 = <!FORBIDDEN_IDENTITY_EQUALS!>any === fn1<!> || <!FORBIDDEN_IDENTITY_EQUALS!>any !== fn1<!>
-    val d4 = fn1 === any || fn1 !== any
+    val d4 = <!FORBIDDEN_IDENTITY_EQUALS!>fn1 === any<!> || <!FORBIDDEN_IDENTITY_EQUALS!>fn1 !== any<!>
 }

compiler/testData/diagnostics/testsWithStdLib/equalityCompatibilityCommonCases.fir.kt

@@ -75,24 +75,24 @@ fun incompatibleEnumComparisonSmartCast(c: Any?, e: Any?) {
 
 fun incompatibleIdentityRegardlessNullability(a: Int?, b: String?) {
     <!EQUALITY_NOT_APPLICABLE!>a == b<!>
-    a === b
+    <!FORBIDDEN_IDENTITY_EQUALS!>a === b<!>
 }
 
 fun incompatibleIdentityRegardlessNullabilitySmartCast(a: Any?, b: Any?) {
     if (a is Int? && b is String?) {
         <!EQUALITY_NOT_APPLICABLE_WARNING!>a == b<!>
-        a === b
+        <!FORBIDDEN_IDENTITY_EQUALS_WARNING!>a === b<!>
     }
 }
 
 fun incompatibleIdentityRegardlessNullabilityWithValueClasses(c: C?, d: D?) {
     c == d
-    c === d
+    <!FORBIDDEN_IDENTITY_EQUALS!>c === d<!>
 }
 
 fun incompatibleIdentityRegardlessNullabilityWithValueClassesSmartCast(c: Any?, d: Any?) {
     if (c is C? && d is D?) {
         c == d
-        c === d
+        <!FORBIDDEN_IDENTITY_EQUALS_WARNING!>c === d<!>
     }
 }

compiler/tests-spec/testData/diagnostics/notLinked/dfa/neg/1.fir.kt

@@ -122,7 +122,7 @@ fun case_9(x: TypealiasNullableString<!REDUNDANT_NULLABLE!>?<!>) {
 fun case_10() {
     val a = Class()
 
-    if (a.prop_4 === null || <!USELESS_IS_CHECK!>true is Boolean<!>) {
+    if (<!FORBIDDEN_IDENTITY_EQUALS_WARNING!>a.prop_4 === null<!> || <!USELESS_IS_CHECK!>true is Boolean<!>) {
         if (<!FORBIDDEN_IDENTITY_EQUALS_WARNING, SENSELESS_COMPARISON!>a.prop_4 != null !== null<!>) {
             a.prop_4
             a.prop_4<!UNSAFE_CALL!>.<!>equals(null)

compiler/tests-spec/testData/diagnostics/notLinked/dfa/neg/15.fir.kt

@@ -21,7 +21,7 @@ fun case_1() {
  */
 fun case_2() {
     var x: Boolean? = true
-    if (x !== null && try { x = null; true } catch (e: Exception) { false }) {
+    if (<!FORBIDDEN_IDENTITY_EQUALS_WARNING!>x !== null<!> && try { x = null; true } catch (e: Exception) { false }) {
         <!DEBUG_INFO_EXPRESSION_TYPE("kotlin.Boolean?")!>x<!>
         <!DEBUG_INFO_EXPRESSION_TYPE("kotlin.Boolean?")!>x<!><!UNSAFE_CALL!>.<!>not()
     }

compiler/tests-spec/testData/diagnostics/notLinked/dfa/pos/1.fir.kt

@@ -173,7 +173,7 @@ fun case_9(x: TypealiasNullableString?) {
 fun case_10() {
     val a = Class()
 
-    if (a.prop_4 === null || true) {
+    if (<!FORBIDDEN_IDENTITY_EQUALS_WARNING!>a.prop_4 === null<!> || true) {
         if (a.prop_4 != null) {
             a.prop_4
             a.prop_4.equals(null)
@@ -419,7 +419,7 @@ fun case_20(b: Boolean) {
 
 // TESTCASE NUMBER: 21
 fun case_21() {
-    if (EnumClassWithNullableProperty.B.prop_1 !== null) {
+    if (<!FORBIDDEN_IDENTITY_EQUALS_WARNING!>EnumClassWithNullableProperty.B.prop_1 !== null<!>) {
         EnumClassWithNullableProperty.B.prop_1
         EnumClassWithNullableProperty.B.prop_1.equals(null)
         EnumClassWithNullableProperty.B.prop_1.propT
@@ -451,7 +451,7 @@ fun case_22(a: (() -> Unit)?) {
 
 // TESTCASE NUMBER: 23
 fun case_23(a: ((Float) -> Int?)?, b: Float?) {
-    if (a != null && b !== null) {
+    if (a != null && <!FORBIDDEN_IDENTITY_EQUALS_WARNING!>b !== null<!>) {
         val x = <!DEBUG_INFO_EXPRESSION_TYPE("kotlin.Int?")!>a(<!DEBUG_INFO_EXPRESSION_TYPE("kotlin.Float? & kotlin.Float")!>b<!>)<!>
         if (x != null) {
             <!DEBUG_INFO_EXPRESSION_TYPE("kotlin.Int? & kotlin.Int")!>x<!>
@@ -1535,36 +1535,36 @@ open class Case29(a: Int?, val b: Float?, private val c: Unit?, protected val d:
 }
 
 fun case_29(a: Case29) {
-    if (a.x !== null) a.x.equals(null)
+    if (<!FORBIDDEN_IDENTITY_EQUALS_WARNING!>a.x !== null<!>) a.x.equals(null)
-    if (a.x !== null) a.x.propT
+    if (<!FORBIDDEN_IDENTITY_EQUALS_WARNING!>a.x !== null<!>) a.x.propT
-    if (a.x !== null) a.x.propAny
+    if (<!FORBIDDEN_IDENTITY_EQUALS_WARNING!>a.x !== null<!>) a.x.propAny
-    if (a.x !== null) a.x.propNullableT
+    if (<!FORBIDDEN_IDENTITY_EQUALS_WARNING!>a.x !== null<!>) a.x.propNullableT
-    if (a.x !== null) a.x.propNullableAny
+    if (<!FORBIDDEN_IDENTITY_EQUALS_WARNING!>a.x !== null<!>) a.x.propNullableAny
-    if (a.x !== null) a.x.funT()
+    if (<!FORBIDDEN_IDENTITY_EQUALS_WARNING!>a.x !== null<!>) a.x.funT()
-    if (a.x !== null) a.x.funAny()
+    if (<!FORBIDDEN_IDENTITY_EQUALS_WARNING!>a.x !== null<!>) a.x.funAny()
-    if (a.x !== null) a.x.funNullableT()
+    if (<!FORBIDDEN_IDENTITY_EQUALS_WARNING!>a.x !== null<!>) a.x.funNullableT()
-    if (a.x !== null) a.x.funNullableAny()
+    if (<!FORBIDDEN_IDENTITY_EQUALS_WARNING!>a.x !== null<!>) a.x.funNullableAny()
-    if (a.x !== null) a.x
+    if (<!FORBIDDEN_IDENTITY_EQUALS_WARNING!>a.x !== null<!>) a.x
-    if (a.b !== null) a.b.equals(null)
+    if (<!FORBIDDEN_IDENTITY_EQUALS_WARNING!>a.b !== null<!>) a.b.equals(null)
-    if (a.b !== null) a.b.propT
+    if (<!FORBIDDEN_IDENTITY_EQUALS_WARNING!>a.b !== null<!>) a.b.propT
-    if (a.b !== null) a.b.propAny
+    if (<!FORBIDDEN_IDENTITY_EQUALS_WARNING!>a.b !== null<!>) a.b.propAny
-    if (a.b !== null) a.b.propNullableT
+    if (<!FORBIDDEN_IDENTITY_EQUALS_WARNING!>a.b !== null<!>) a.b.propNullableT
-    if (a.b !== null) a.b.propNullableAny
+    if (<!FORBIDDEN_IDENTITY_EQUALS_WARNING!>a.b !== null<!>) a.b.propNullableAny
-    if (a.b !== null) a.b.funT()
+    if (<!FORBIDDEN_IDENTITY_EQUALS_WARNING!>a.b !== null<!>) a.b.funT()
-    if (a.b !== null) a.b.funAny()
+    if (<!FORBIDDEN_IDENTITY_EQUALS_WARNING!>a.b !== null<!>) a.b.funAny()
-    if (a.b !== null) a.b.funNullableT()
+    if (<!FORBIDDEN_IDENTITY_EQUALS_WARNING!>a.b !== null<!>) a.b.funNullableT()
-    if (a.b !== null) a.b.funNullableAny()
+    if (<!FORBIDDEN_IDENTITY_EQUALS_WARNING!>a.b !== null<!>) a.b.funNullableAny()
-    if (a.b !== null) a.b
+    if (<!FORBIDDEN_IDENTITY_EQUALS_WARNING!>a.b !== null<!>) a.b
-    if (a.e !== null) a.e.equals(null)
+    if (<!FORBIDDEN_IDENTITY_EQUALS_WARNING!>a.e !== null<!>) a.e.equals(null)
-    if (a.e !== null) a.e.propT
+    if (<!FORBIDDEN_IDENTITY_EQUALS_WARNING!>a.e !== null<!>) a.e.propT
-    if (a.e !== null) a.e.propAny
+    if (<!FORBIDDEN_IDENTITY_EQUALS_WARNING!>a.e !== null<!>) a.e.propAny
-    if (a.e !== null) a.e.propNullableT
+    if (<!FORBIDDEN_IDENTITY_EQUALS_WARNING!>a.e !== null<!>) a.e.propNullableT
-    if (a.e !== null) a.e.propNullableAny
+    if (<!FORBIDDEN_IDENTITY_EQUALS_WARNING!>a.e !== null<!>) a.e.propNullableAny
-    if (a.e !== null) a.e.funT()
+    if (<!FORBIDDEN_IDENTITY_EQUALS_WARNING!>a.e !== null<!>) a.e.funT()
-    if (a.e !== null) a.e.funAny()
+    if (<!FORBIDDEN_IDENTITY_EQUALS_WARNING!>a.e !== null<!>) a.e.funAny()
-    if (a.e !== null) a.e.funNullableT()
+    if (<!FORBIDDEN_IDENTITY_EQUALS_WARNING!>a.e !== null<!>) a.e.funNullableT()
-    if (a.e !== null) a.e.funNullableAny()
+    if (<!FORBIDDEN_IDENTITY_EQUALS_WARNING!>a.e !== null<!>) a.e.funNullableAny()
-    if (a.e !== null) a.e
+    if (<!FORBIDDEN_IDENTITY_EQUALS_WARNING!>a.e !== null<!>) a.e
     if (a.f !== null) a.f.equals(null)
     if (a.f !== null) a.f.propT
     if (a.f !== null) a.f.propAny
@@ -2579,36 +2579,36 @@ sealed class Case30(a: Int?, val b: Float?, private val c: Unit?, protected val
 }
 
 fun case_30(a: Case30) {
-    if (a.x !== null) a.x.equals(null)
+    if (<!FORBIDDEN_IDENTITY_EQUALS_WARNING!>a.x !== null<!>) a.x.equals(null)
-    if (a.x !== null) a.x.propT
+    if (<!FORBIDDEN_IDENTITY_EQUALS_WARNING!>a.x !== null<!>) a.x.propT
-    if (a.x !== null) a.x.propAny
+    if (<!FORBIDDEN_IDENTITY_EQUALS_WARNING!>a.x !== null<!>) a.x.propAny
-    if (a.x !== null) a.x.propNullableT
+    if (<!FORBIDDEN_IDENTITY_EQUALS_WARNING!>a.x !== null<!>) a.x.propNullableT
-    if (a.x !== null) a.x.propNullableAny
+    if (<!FORBIDDEN_IDENTITY_EQUALS_WARNING!>a.x !== null<!>) a.x.propNullableAny
-    if (a.x !== null) a.x.funT()
+    if (<!FORBIDDEN_IDENTITY_EQUALS_WARNING!>a.x !== null<!>) a.x.funT()
-    if (a.x !== null) a.x.funAny()
+    if (<!FORBIDDEN_IDENTITY_EQUALS_WARNING!>a.x !== null<!>) a.x.funAny()
-    if (a.x !== null) a.x.funNullableT()
+    if (<!FORBIDDEN_IDENTITY_EQUALS_WARNING!>a.x !== null<!>) a.x.funNullableT()
-    if (a.x !== null) a.x.funNullableAny()
+    if (<!FORBIDDEN_IDENTITY_EQUALS_WARNING!>a.x !== null<!>) a.x.funNullableAny()
-    if (a.x !== null) a.x
+    if (<!FORBIDDEN_IDENTITY_EQUALS_WARNING!>a.x !== null<!>) a.x
-    if (a.b !== null) a.b.equals(null)
+    if (<!FORBIDDEN_IDENTITY_EQUALS_WARNING!>a.b !== null<!>) a.b.equals(null)
-    if (a.b !== null) a.b.propT
+    if (<!FORBIDDEN_IDENTITY_EQUALS_WARNING!>a.b !== null<!>) a.b.propT
-    if (a.b !== null) a.b.propAny
+    if (<!FORBIDDEN_IDENTITY_EQUALS_WARNING!>a.b !== null<!>) a.b.propAny
-    if (a.b !== null) a.b.propNullableT
+    if (<!FORBIDDEN_IDENTITY_EQUALS_WARNING!>a.b !== null<!>) a.b.propNullableT
-    if (a.b !== null) a.b.propNullableAny
+    if (<!FORBIDDEN_IDENTITY_EQUALS_WARNING!>a.b !== null<!>) a.b.propNullableAny
-    if (a.b !== null) a.b.funT()
+    if (<!FORBIDDEN_IDENTITY_EQUALS_WARNING!>a.b !== null<!>) a.b.funT()
-    if (a.b !== null) a.b.funAny()
+    if (<!FORBIDDEN_IDENTITY_EQUALS_WARNING!>a.b !== null<!>) a.b.funAny()
-    if (a.b !== null) a.b.funNullableT()
+    if (<!FORBIDDEN_IDENTITY_EQUALS_WARNING!>a.b !== null<!>) a.b.funNullableT()
-    if (a.b !== null) a.b.funNullableAny()
+    if (<!FORBIDDEN_IDENTITY_EQUALS_WARNING!>a.b !== null<!>) a.b.funNullableAny()
-    if (a.b !== null) a.b
+    if (<!FORBIDDEN_IDENTITY_EQUALS_WARNING!>a.b !== null<!>) a.b
-    if (a.e !== null) a.e.equals(null)
+    if (<!FORBIDDEN_IDENTITY_EQUALS_WARNING!>a.e !== null<!>) a.e.equals(null)
-    if (a.e !== null) a.e.propT
+    if (<!FORBIDDEN_IDENTITY_EQUALS_WARNING!>a.e !== null<!>) a.e.propT
-    if (a.e !== null) a.e.propAny
+    if (<!FORBIDDEN_IDENTITY_EQUALS_WARNING!>a.e !== null<!>) a.e.propAny
-    if (a.e !== null) a.e.propNullableT
+    if (<!FORBIDDEN_IDENTITY_EQUALS_WARNING!>a.e !== null<!>) a.e.propNullableT
-    if (a.e !== null) a.e.propNullableAny
+    if (<!FORBIDDEN_IDENTITY_EQUALS_WARNING!>a.e !== null<!>) a.e.propNullableAny
-    if (a.e !== null) a.e.funT()
+    if (<!FORBIDDEN_IDENTITY_EQUALS_WARNING!>a.e !== null<!>) a.e.funT()
-    if (a.e !== null) a.e.funAny()
+    if (<!FORBIDDEN_IDENTITY_EQUALS_WARNING!>a.e !== null<!>) a.e.funAny()
-    if (a.e !== null) a.e.funNullableT()
+    if (<!FORBIDDEN_IDENTITY_EQUALS_WARNING!>a.e !== null<!>) a.e.funNullableT()
-    if (a.e !== null) a.e.funNullableAny()
+    if (<!FORBIDDEN_IDENTITY_EQUALS_WARNING!>a.e !== null<!>) a.e.funNullableAny()
-    if (a.e !== null) a.e
+    if (<!FORBIDDEN_IDENTITY_EQUALS_WARNING!>a.e !== null<!>) a.e
     if (a.f !== null) a.f.equals(null)
     if (a.f !== null) a.f.propT
     if (a.f !== null) a.f.propAny
@@ -3624,36 +3624,36 @@ enum class Case31(a: Int?, val b: Float?, private val c: Unit?, protected val d:
 }
 
 fun case_31(a: Case31) {
-    if (a.x !== null) a.x.equals(null)
+    if (<!FORBIDDEN_IDENTITY_EQUALS_WARNING!>a.x !== null<!>) a.x.equals(null)
-    if (a.x !== null) a.x.propT
+    if (<!FORBIDDEN_IDENTITY_EQUALS_WARNING!>a.x !== null<!>) a.x.propT
-    if (a.x !== null) a.x.propAny
+    if (<!FORBIDDEN_IDENTITY_EQUALS_WARNING!>a.x !== null<!>) a.x.propAny
-    if (a.x !== null) a.x.propNullableT
+    if (<!FORBIDDEN_IDENTITY_EQUALS_WARNING!>a.x !== null<!>) a.x.propNullableT
-    if (a.x !== null) a.x.propNullableAny
+    if (<!FORBIDDEN_IDENTITY_EQUALS_WARNING!>a.x !== null<!>) a.x.propNullableAny
-    if (a.x !== null) a.x.funT()
+    if (<!FORBIDDEN_IDENTITY_EQUALS_WARNING!>a.x !== null<!>) a.x.funT()
-    if (a.x !== null) a.x.funAny()
+    if (<!FORBIDDEN_IDENTITY_EQUALS_WARNING!>a.x !== null<!>) a.x.funAny()
-    if (a.x !== null) a.x.funNullableT()
+    if (<!FORBIDDEN_IDENTITY_EQUALS_WARNING!>a.x !== null<!>) a.x.funNullableT()
-    if (a.x !== null) a.x.funNullableAny()
+    if (<!FORBIDDEN_IDENTITY_EQUALS_WARNING!>a.x !== null<!>) a.x.funNullableAny()
-    if (a.x !== null) a.x
+    if (<!FORBIDDEN_IDENTITY_EQUALS_WARNING!>a.x !== null<!>) a.x
-    if (a.b !== null) a.b.equals(null)
+    if (<!FORBIDDEN_IDENTITY_EQUALS_WARNING!>a.b !== null<!>) a.b.equals(null)
-    if (a.b !== null) a.b.propT
+    if (<!FORBIDDEN_IDENTITY_EQUALS_WARNING!>a.b !== null<!>) a.b.propT
-    if (a.b !== null) a.b.propAny
+    if (<!FORBIDDEN_IDENTITY_EQUALS_WARNING!>a.b !== null<!>) a.b.propAny
-    if (a.b !== null) a.b.propNullableT
+    if (<!FORBIDDEN_IDENTITY_EQUALS_WARNING!>a.b !== null<!>) a.b.propNullableT
-    if (a.b !== null) a.b.propNullableAny
+    if (<!FORBIDDEN_IDENTITY_EQUALS_WARNING!>a.b !== null<!>) a.b.propNullableAny
-    if (a.b !== null) a.b.funT()
+    if (<!FORBIDDEN_IDENTITY_EQUALS_WARNING!>a.b !== null<!>) a.b.funT()
-    if (a.b !== null) a.b.funAny()
+    if (<!FORBIDDEN_IDENTITY_EQUALS_WARNING!>a.b !== null<!>) a.b.funAny()
-    if (a.b !== null) a.b.funNullableT()
+    if (<!FORBIDDEN_IDENTITY_EQUALS_WARNING!>a.b !== null<!>) a.b.funNullableT()
-    if (a.b !== null) a.b.funNullableAny()
+    if (<!FORBIDDEN_IDENTITY_EQUALS_WARNING!>a.b !== null<!>) a.b.funNullableAny()
-    if (a.b !== null) a.b
+    if (<!FORBIDDEN_IDENTITY_EQUALS_WARNING!>a.b !== null<!>) a.b
-    if (a.e !== null) a.e.equals(null)
+    if (<!FORBIDDEN_IDENTITY_EQUALS_WARNING!>a.e !== null<!>) a.e.equals(null)
-    if (a.e !== null) a.e.propT
+    if (<!FORBIDDEN_IDENTITY_EQUALS_WARNING!>a.e !== null<!>) a.e.propT
-    if (a.e !== null) a.e.propAny
+    if (<!FORBIDDEN_IDENTITY_EQUALS_WARNING!>a.e !== null<!>) a.e.propAny
-    if (a.e !== null) a.e.propNullableT
+    if (<!FORBIDDEN_IDENTITY_EQUALS_WARNING!>a.e !== null<!>) a.e.propNullableT
-    if (a.e !== null) a.e.propNullableAny
+    if (<!FORBIDDEN_IDENTITY_EQUALS_WARNING!>a.e !== null<!>) a.e.propNullableAny
-    if (a.e !== null) a.e.funT()
+    if (<!FORBIDDEN_IDENTITY_EQUALS_WARNING!>a.e !== null<!>) a.e.funT()
-    if (a.e !== null) a.e.funAny()
+    if (<!FORBIDDEN_IDENTITY_EQUALS_WARNING!>a.e !== null<!>) a.e.funAny()
-    if (a.e !== null) a.e.funNullableT()
+    if (<!FORBIDDEN_IDENTITY_EQUALS_WARNING!>a.e !== null<!>) a.e.funNullableT()
-    if (a.e !== null) a.e.funNullableAny()
+    if (<!FORBIDDEN_IDENTITY_EQUALS_WARNING!>a.e !== null<!>) a.e.funNullableAny()
-    if (a.e !== null) a.e
+    if (<!FORBIDDEN_IDENTITY_EQUALS_WARNING!>a.e !== null<!>) a.e
     if (a.f !== null) a.f.equals(null)
     if (a.f !== null) a.f.propT
     if (a.f !== null) a.f.propAny

compiler/tests-spec/testData/diagnostics/notLinked/dfa/pos/16.fir.kt

@@ -114,7 +114,7 @@ fun case_9(x: String?) {
 
 // TESTCASE NUMBER: 10
 fun case_10(x: Float?) {
-    if (true && true && true && x !== null) else return
+    if (true && true && true && <!FORBIDDEN_IDENTITY_EQUALS_WARNING!>x !== null<!>) else return
     <!DEBUG_INFO_EXPRESSION_TYPE("kotlin.Float? & kotlin.Float")!>x<!>
     <!DEBUG_INFO_EXPRESSION_TYPE("kotlin.Float? & kotlin.Float")!>x<!>.equals(null)
     <!DEBUG_INFO_EXPRESSION_TYPE("kotlin.Float? & kotlin.Float")!>x<!>.propT
@@ -465,7 +465,7 @@ fun case_33(x: Any?) {
 // TESTCASE NUMBER: 34
 fun case_34(x: Float?) {
     (l@ {
-        if (true && true && true && x !== null) else return@l
+        if (true && true && true && <!FORBIDDEN_IDENTITY_EQUALS_WARNING!>x !== null<!>) else return@l
         <!DEBUG_INFO_EXPRESSION_TYPE("kotlin.Float? & kotlin.Float")!>x<!>
         <!DEBUG_INFO_EXPRESSION_TYPE("kotlin.Float? & kotlin.Float")!>x<!>.equals(null)
         <!DEBUG_INFO_EXPRESSION_TYPE("kotlin.Float? & kotlin.Float")!>x<!>.propT
@@ -477,7 +477,7 @@ fun case_34(x: Float?) {
         <!DEBUG_INFO_EXPRESSION_TYPE("kotlin.Float? & kotlin.Float")!>x<!>.funNullableT()
         <!DEBUG_INFO_EXPRESSION_TYPE("kotlin.Float? & kotlin.Float")!>x<!>.funNullableAny()
     }).equals(l@ {
-        if (true && true && true && x !== null) else return@l
+        if (true && true && true && <!FORBIDDEN_IDENTITY_EQUALS_WARNING!>x !== null<!>) else return@l
         <!DEBUG_INFO_EXPRESSION_TYPE("kotlin.Float? & kotlin.Float")!>x<!>
         <!DEBUG_INFO_EXPRESSION_TYPE("kotlin.Float? & kotlin.Float")!>x<!>.equals(null)
         <!DEBUG_INFO_EXPRESSION_TYPE("kotlin.Float? & kotlin.Float")!>x<!>.propT

compiler/tests-spec/testData/diagnostics/notLinked/dfa/pos/17.fir.kt

@@ -113,7 +113,7 @@ fun case_9(x: String?) {
 
 // TESTCASE NUMBER: 10
 fun case_10(x: Float?) {
-    if (true && true && true && x !== null) else throw Exception()
+    if (true && true && true && <!FORBIDDEN_IDENTITY_EQUALS_WARNING!>x !== null<!>) else throw Exception()
     <!DEBUG_INFO_EXPRESSION_TYPE("kotlin.Float? & kotlin.Float")!>x<!>
     <!DEBUG_INFO_EXPRESSION_TYPE("kotlin.Float? & kotlin.Float")!>x<!>.equals(null)
     <!DEBUG_INFO_EXPRESSION_TYPE("kotlin.Float? & kotlin.Float")!>x<!>.propT

compiler/tests-spec/testData/diagnostics/notLinked/dfa/pos/18.fir.kt

@@ -124,7 +124,7 @@ fun case_9(list: List<Int?>) {
 // TESTCASE NUMBER: 10
 fun case_10(x: Float?) {
     while (false) {
-        if (true && true && true && x !== null) else break
+        if (true && true && true && <!FORBIDDEN_IDENTITY_EQUALS_WARNING!>x !== null<!>) else break
         <!DEBUG_INFO_EXPRESSION_TYPE("kotlin.Float?")!>x<!>
         <!DEBUG_INFO_EXPRESSION_TYPE("kotlin.Float?")!>x<!><!UNSAFE_CALL!>.<!>equals(null)
         <!DEBUG_INFO_EXPRESSION_TYPE("kotlin.Float?")!>x<!>.propT
@@ -158,7 +158,7 @@ fun case_11(x: Out<*>?, list: List<Int>) {
 // TESTCASE NUMBER: 12
 fun case_12(list: List<Int?>) {
     for (element in list) {
-        if (element === null) continue
+        if (<!FORBIDDEN_IDENTITY_EQUALS_WARNING!>element === null<!>) continue
         <!DEBUG_INFO_EXPRESSION_TYPE("kotlin.Int? & kotlin.Int")!>element<!>
         <!DEBUG_INFO_EXPRESSION_TYPE("kotlin.Int? & kotlin.Int")!>element<!>.inv()
     }
@@ -213,7 +213,7 @@ fun case_15(map: MutableMap<Int?, Int?>, y: Nothing?) {
 // TESTCASE NUMBER: 16
 fun case_16(map: Map<Int?, Int?>) {
     for ((k, v) in map) {
-        if (k !== implicitNullableNothingProperty && v !== implicitNullableNothingProperty) else { continue }
+        if (<!FORBIDDEN_IDENTITY_EQUALS_WARNING!>k !== implicitNullableNothingProperty<!> && <!FORBIDDEN_IDENTITY_EQUALS_WARNING!>v !== implicitNullableNothingProperty<!>) else { continue }
         <!DEBUG_INFO_EXPRESSION_TYPE("kotlin.Int? & kotlin.Int")!>k<!>
         <!DEBUG_INFO_EXPRESSION_TYPE("kotlin.Int? & kotlin.Int")!>k<!>.inv()
         <!DEBUG_INFO_EXPRESSION_TYPE("kotlin.Int? & kotlin.Int")!>v<!>

compiler/tests-spec/testData/diagnostics/notLinked/dfa/pos/28.fir.kt

@@ -59,7 +59,7 @@ fun case_7(x: DeepObject.A.B.C.D.E.F.G.J?) {
 
 // TESTCASE NUMBER: 8
 fun case_8(x: Any?) {
-    if (x?.equals(10) === null) else {
+    if (<!FORBIDDEN_IDENTITY_EQUALS_WARNING!>x?.equals(10) === null<!>) else {
         <!DEBUG_INFO_EXPRESSION_TYPE("kotlin.Any? & kotlin.Any")!>x<!>
         <!DEBUG_INFO_EXPRESSION_TYPE("kotlin.Any? & kotlin.Any")!>x<!>.equals(10)
     }
@@ -67,7 +67,7 @@ fun case_8(x: Any?) {
 
 // TESTCASE NUMBER: 9
 fun case_9(x: Any?) {
-    if (x?.equals(10) !== null) {
+    if (<!FORBIDDEN_IDENTITY_EQUALS_WARNING!>x?.equals(10) !== null<!>) {
         <!DEBUG_INFO_EXPRESSION_TYPE("kotlin.Any? & kotlin.Any")!>x<!>
         <!DEBUG_INFO_EXPRESSION_TYPE("kotlin.Any? & kotlin.Any")!>x<!>.equals(10)
     }
@@ -117,7 +117,7 @@ inline fun <reified T>case_13(x: Any?) {
 
 // TESTCASE NUMBER: 14
 inline fun <reified T>case_14(x: Any?) {
-    if (x?.equals(10) === null) else {
+    if (<!FORBIDDEN_IDENTITY_EQUALS_WARNING!>x?.equals(10) === null<!>) else {
         <!DEBUG_INFO_EXPRESSION_TYPE("kotlin.Any? & kotlin.Any")!>x<!>
         <!DEBUG_INFO_EXPRESSION_TYPE("kotlin.Any? & kotlin.Any")!>x<!>.equals(10)
     }
@@ -125,7 +125,7 @@ inline fun <reified T>case_14(x: Any?) {
 
 // TESTCASE NUMBER: 15
 inline fun <reified T>case_15(x: Any?) {
-    if (x?.equals(10) !== null) {
+    if (<!FORBIDDEN_IDENTITY_EQUALS_WARNING!>x?.equals(10) !== null<!>) {
         <!DEBUG_INFO_EXPRESSION_TYPE("kotlin.Any? & kotlin.Any")!>x<!>
         <!DEBUG_INFO_EXPRESSION_TYPE("kotlin.Any? & kotlin.Any")!>x<!>.equals(10)
     }
@@ -137,7 +137,7 @@ inline fun <reified T>case_15(x: Any?) {
  * ISSUES: KT-30369, KT-28262
  */
 inline fun <reified T>case_16(x: Any?) {
-    if (x?.equals(10) === null == true) else {
+    if (<!FORBIDDEN_IDENTITY_EQUALS_WARNING!>x?.equals(10) === null<!> == true) else {
         <!DEBUG_INFO_EXPRESSION_TYPE("kotlin.Any? & kotlin.Any")!>x<!>
         <!DEBUG_INFO_EXPRESSION_TYPE("kotlin.Any? & kotlin.Any")!>x<!>.equals(10)
     }
@@ -149,7 +149,7 @@ inline fun <reified T>case_16(x: Any?) {
  * ISSUES: KT-30369, KT-28262
  */
 inline fun <reified T>case_17(x: Any?) {
-    if (x?.equals(10) !== null == true) {
+    if (<!FORBIDDEN_IDENTITY_EQUALS_WARNING!>x?.equals(10) !== null<!> == true) {
         <!DEBUG_INFO_EXPRESSION_TYPE("kotlin.Any? & kotlin.Any")!>x<!>
         <!DEBUG_INFO_EXPRESSION_TYPE("kotlin.Any? & kotlin.Any")!>x<!>.equals(10)
     }
@@ -161,7 +161,7 @@ inline fun <reified T>case_17(x: Any?) {
  * ISSUES: KT-30369, KT-28262, KT-29878
  */
 inline fun <reified T>case_18(x: Any?) {
-    if (<!DEPRECATED_IDENTITY_EQUALS!>x?.equals(10) === null === true<!>) else {
+    if (<!DEPRECATED_IDENTITY_EQUALS!><!FORBIDDEN_IDENTITY_EQUALS_WARNING!>x?.equals(10) === null<!> === true<!>) else {
         <!DEBUG_INFO_EXPRESSION_TYPE("kotlin.Any? & kotlin.Any")!>x<!>
         <!DEBUG_INFO_EXPRESSION_TYPE("kotlin.Any? & kotlin.Any")!>x<!>.equals(10)
     }
@@ -173,7 +173,7 @@ inline fun <reified T>case_18(x: Any?) {
  * ISSUES: KT-30369, KT-28262, KT-29878
  */
 inline fun <reified T>case_19(x: Any?) {
-    if (<!DEPRECATED_IDENTITY_EQUALS!>x?.equals(10) !== null === true<!>) {
+    if (<!DEPRECATED_IDENTITY_EQUALS!><!FORBIDDEN_IDENTITY_EQUALS_WARNING!>x?.equals(10) !== null<!> === true<!>) {
         <!DEBUG_INFO_EXPRESSION_TYPE("kotlin.Any? & kotlin.Any")!>x<!>
         <!DEBUG_INFO_EXPRESSION_TYPE("kotlin.Any? & kotlin.Any")!>x<!>.equals(10)
     }
@@ -185,7 +185,7 @@ inline fun <reified T>case_19(x: Any?) {
  * ISSUES: KT-30369, KT-28262, KT-29878
  */
 inline fun <reified T>case_20(x: Any?) {
-    if (<!DEPRECATED_IDENTITY_EQUALS!>x?.equals(10) === null !== false<!>) else {
+    if (<!DEPRECATED_IDENTITY_EQUALS!><!FORBIDDEN_IDENTITY_EQUALS_WARNING!>x?.equals(10) === null<!> !== false<!>) else {
         <!DEBUG_INFO_EXPRESSION_TYPE("kotlin.Any? & kotlin.Any")!>x<!>
         <!DEBUG_INFO_EXPRESSION_TYPE("kotlin.Any? & kotlin.Any")!>x<!>.equals(10)
     }
@@ -197,7 +197,7 @@ inline fun <reified T>case_20(x: Any?) {
  * ISSUES: KT-30369, KT-28262, KT-29878
  */
 inline fun <reified T>case_21(x: Any?) {
-    if (<!DEPRECATED_IDENTITY_EQUALS!>x?.equals(10) !== null !== false<!>) {
+    if (<!DEPRECATED_IDENTITY_EQUALS!><!FORBIDDEN_IDENTITY_EQUALS_WARNING!>x?.equals(10) !== null<!> !== false<!>) {
         <!DEBUG_INFO_EXPRESSION_TYPE("kotlin.Any? & kotlin.Any")!>x<!>
         <!DEBUG_INFO_EXPRESSION_TYPE("kotlin.Any? & kotlin.Any")!>x<!>.equals(10)
     }
@@ -209,7 +209,7 @@ inline fun <reified T>case_21(x: Any?) {
  * ISSUES: KT-30369, KT-28262, KT-29878
  */
 inline fun <reified T>case_22(x: Any?) {
-    if (<!DEPRECATED_IDENTITY_EQUALS!>x?.equals(10) !== null !== true<!>) else {
+    if (<!DEPRECATED_IDENTITY_EQUALS!><!FORBIDDEN_IDENTITY_EQUALS_WARNING!>x?.equals(10) !== null<!> !== true<!>) else {
         <!DEBUG_INFO_EXPRESSION_TYPE("kotlin.Any? & kotlin.Any")!>x<!>
         <!DEBUG_INFO_EXPRESSION_TYPE("kotlin.Any? & kotlin.Any")!>x<!>.equals(10)
     }
@@ -221,7 +221,7 @@ inline fun <reified T>case_22(x: Any?) {
  * ISSUES: KT-30369, KT-28262, KT-29878
  */
 inline fun <reified T>case_23(x: Any?) {
-    if (<!DEPRECATED_IDENTITY_EQUALS!>x?.equals(10) === null === false<!>) {
+    if (<!DEPRECATED_IDENTITY_EQUALS!><!FORBIDDEN_IDENTITY_EQUALS_WARNING!>x?.equals(10) === null<!> === false<!>) {
         <!DEBUG_INFO_EXPRESSION_TYPE("kotlin.Any? & kotlin.Any")!>x<!>
         <!DEBUG_INFO_EXPRESSION_TYPE("kotlin.Any? & kotlin.Any")!>x<!>.equals(10)
     }
@@ -233,7 +233,7 @@ inline fun <reified T>case_23(x: Any?) {
  * ISSUES: KT-30369, KT-28262
  */
 inline fun <reified T>case_24(x: Any?) {
-    if (x?.equals(10) !== null != true) else {
+    if (<!FORBIDDEN_IDENTITY_EQUALS_WARNING!>x?.equals(10) !== null<!> != true) else {
         <!DEBUG_INFO_EXPRESSION_TYPE("kotlin.Any? & kotlin.Any")!>x<!>
         <!DEBUG_INFO_EXPRESSION_TYPE("kotlin.Any? & kotlin.Any")!>x<!>.equals(10)
     }
@@ -245,7 +245,7 @@ inline fun <reified T>case_24(x: Any?) {
  * ISSUES: KT-30369, KT-28262
  */
 inline fun <reified T>case_25(x: Any?) {
-    if (x?.equals(10) === null == false) {
+    if (<!FORBIDDEN_IDENTITY_EQUALS_WARNING!>x?.equals(10) === null<!> == false) {
         <!DEBUG_INFO_EXPRESSION_TYPE("kotlin.Any? & kotlin.Any")!>x<!>
         <!DEBUG_INFO_EXPRESSION_TYPE("kotlin.Any? & kotlin.Any")!>x<!>.equals(10)
     }

compiler/tests-spec/testData/diagnostics/notLinked/dfa/pos/3.fir.kt

@@ -187,7 +187,7 @@ fun case_16() {
 }
 
 // TESTCASE NUMBER: 17
-val case_17 = <!DEBUG_INFO_EXPRESSION_TYPE("kotlin.Int?")!>if (nullableIntProperty !== null) 0 else {
+val case_17 = <!DEBUG_INFO_EXPRESSION_TYPE("kotlin.Int?")!>if (<!FORBIDDEN_IDENTITY_EQUALS_WARNING!>nullableIntProperty !== null<!>) 0 else {
     <!DEBUG_INFO_EXPRESSION_TYPE("kotlin.Int? & kotlin.Nothing?")!>nullableIntProperty<!>
 }<!>
 
@@ -297,7 +297,7 @@ fun case_25(b: Boolean) {
 }
 
 // TESTCASE NUMBER: 26
-fun case_26(a: Int?, b: Int? = if (a !== null) 0 else <!DEBUG_INFO_EXPRESSION_TYPE("kotlin.Int? & kotlin.Nothing?")!>a<!>) {
+fun case_26(a: Int?, b: Int? = if (<!FORBIDDEN_IDENTITY_EQUALS_WARNING!>a !== null<!>) 0 else <!DEBUG_INFO_EXPRESSION_TYPE("kotlin.Int? & kotlin.Nothing?")!>a<!>) {
     <!DEBUG_INFO_EXPRESSION_TYPE("kotlin.Int?")!>a<!>
     <!DEBUG_INFO_EXPRESSION_TYPE("kotlin.Int?")!>b<!>
 }

compiler/tests-spec/testData/diagnostics/notLinked/dfa/pos/39.fir.kt

@@ -19,7 +19,7 @@ fun case_1(x: Number?) {
 fun case_2(x: Number) {
     val y: Int? = null
 
-    if (x === y) {
+    if (<!FORBIDDEN_IDENTITY_EQUALS_WARNING!>x === y<!>) {
         <!DEBUG_INFO_EXPRESSION_TYPE("kotlin.Number & kotlin.Int")!>x<!>
         <!DEBUG_INFO_EXPRESSION_TYPE("kotlin.Number & kotlin.Int")!>x<!>.inv()
     }
@@ -29,7 +29,7 @@ fun case_2(x: Number) {
 fun case_3(x: Number) {
     var y: Int? = null
 
-    if (x === y) {
+    if (<!FORBIDDEN_IDENTITY_EQUALS_WARNING!>x === y<!>) {
         <!DEBUG_INFO_EXPRESSION_TYPE("kotlin.Number & kotlin.Int")!>x<!>
         <!DEBUG_INFO_EXPRESSION_TYPE("kotlin.Number & kotlin.Int")!>x<!>.inv()
     }

compiler/tests-spec/testData/diagnostics/notLinked/dfa/pos/5.fir.kt

@@ -351,7 +351,7 @@ fun case_15(x: Any?) {
 }
 
 // TESTCASE NUMBER: 16
-fun case_16(a: Any?, b: Int = if (a is Number? && a is Int? && a !== null) <!DEBUG_INFO_EXPRESSION_TYPE("kotlin.Any? & kotlin.Int")!>a<!> else 0) {
+fun case_16(a: Any?, b: Int = if (a is Number? && a is Int? && <!FORBIDDEN_IDENTITY_EQUALS_WARNING!>a !== null<!>) <!DEBUG_INFO_EXPRESSION_TYPE("kotlin.Any? & kotlin.Int")!>a<!> else 0) {
     <!DEBUG_INFO_EXPRESSION_TYPE("kotlin.Any?")!>a<!>
     <!DEBUG_INFO_EXPRESSION_TYPE("kotlin.Int")!>b<!>
     <!DEBUG_INFO_EXPRESSION_TYPE("kotlin.Int")!>b<!>.equals(null)

compiler/tests-spec/testData/diagnostics/notLinked/dfa/pos/6.fir.kt

@@ -175,7 +175,7 @@ fun case_10() {
     val a = Class()
     val b = null
 
-    if (a.prop_4 === b || true) {
+    if (<!FORBIDDEN_IDENTITY_EQUALS_WARNING!>a.prop_4 === b<!> || true) {
         if (a.prop_4 != null) {
             a.prop_4
             a.prop_4.equals(null)
@@ -307,7 +307,7 @@ fun case_16() {
 }
 
 // TESTCASE NUMBER: 17
-val case_17 = if (nullableIntProperty === implicitNullableNothingProperty) 0 else {
+val case_17 = if (<!FORBIDDEN_IDENTITY_EQUALS_WARNING!>nullableIntProperty === implicitNullableNothingProperty<!>) 0 else {
     <!DEBUG_INFO_EXPRESSION_TYPE("kotlin.Int? & kotlin.Int")!>nullableIntProperty<!>
     <!DEBUG_INFO_EXPRESSION_TYPE("kotlin.Int? & kotlin.Int")!>nullableIntProperty<!>.equals(null)
     <!DEBUG_INFO_EXPRESSION_TYPE("kotlin.Int? & kotlin.Int")!>nullableIntProperty<!>.propT
@@ -405,7 +405,7 @@ fun case_20(x: Boolean, y: Nothing?) {
 
 // TESTCASE NUMBER: 21
 fun case_21() {
-    if (EnumClassWithNullableProperty.A.prop_1 !== implicitNullableNothingProperty) {
+    if (<!FORBIDDEN_IDENTITY_EQUALS_WARNING!>EnumClassWithNullableProperty.A.prop_1 !== implicitNullableNothingProperty<!>) {
         EnumClassWithNullableProperty.A.prop_1
         EnumClassWithNullableProperty.A.prop_1.equals(null)
         EnumClassWithNullableProperty.A.prop_1.propT
@@ -437,9 +437,9 @@ fun case_22(a: (() -> Unit)?) {
 
 // TESTCASE NUMBER: 23
 fun case_23(a: ((Float) -> Int?)?, b: Float?, z: Nothing?) {
-    if (a != z && b !== z && <!FORBIDDEN_IDENTITY_EQUALS_WARNING, SENSELESS_COMPARISON!>b !== z<!>) {
+    if (a != z && <!FORBIDDEN_IDENTITY_EQUALS_WARNING!>b !== z<!> && <!FORBIDDEN_IDENTITY_EQUALS_WARNING, SENSELESS_COMPARISON!>b !== z<!>) {
         val x = <!DEBUG_INFO_EXPRESSION_TYPE("kotlin.Int?")!>a(<!DEBUG_INFO_EXPRESSION_TYPE("kotlin.Float? & kotlin.Float")!>b<!>)<!>
-        if (x != z || <!SENSELESS_COMPARISON!>x !== implicitNullableNothingProperty<!>) {
+        if (x != z || <!FORBIDDEN_IDENTITY_EQUALS_WARNING, SENSELESS_COMPARISON!>x !== implicitNullableNothingProperty<!>) {
             <!DEBUG_INFO_EXPRESSION_TYPE("kotlin.Int?")!>x<!>
             <!DEBUG_INFO_EXPRESSION_TYPE("kotlin.Int?")!>x<!><!UNSAFE_CALL!>.<!>equals(null)
             <!DEBUG_INFO_EXPRESSION_TYPE("kotlin.Int?")!>x<!>.propT
@@ -512,7 +512,7 @@ fun case_26(a: ((Float) -> Int?)?, b: Float?) {
 
     if (a != z == true && b != implicitNullableNothingProperty == true) {
         val x = <!DEBUG_INFO_EXPRESSION_TYPE("kotlin.Int?")!>a(<!DEBUG_INFO_EXPRESSION_TYPE("kotlin.Float? & kotlin.Float")!>b<!>)<!>
-        if (x != implicitNullableNothingProperty == true || <!SENSELESS_COMPARISON!>z !== x<!>) {
+        if (x != implicitNullableNothingProperty == true || <!FORBIDDEN_IDENTITY_EQUALS_WARNING, SENSELESS_COMPARISON!>z !== x<!>) {
             <!DEBUG_INFO_EXPRESSION_TYPE("kotlin.Int? & kotlin.Int")!>x<!>
             <!DEBUG_INFO_EXPRESSION_TYPE("kotlin.Int? & kotlin.Int")!>x<!>.equals(null)
             <!DEBUG_INFO_EXPRESSION_TYPE("kotlin.Int? & kotlin.Int")!>x<!>.propT
@@ -613,7 +613,7 @@ fun case_30(a: ((Float) -> Int?)?, b: Float?) {
 
 // TESTCASE NUMBER: 31
 fun case_31(z1: Boolean?, z: Nothing?) {
-    if (false || EnumClassWithNullableProperty.A.prop_1 != z && z1 !== z && z1) {
+    if (false || EnumClassWithNullableProperty.A.prop_1 != z && <!FORBIDDEN_IDENTITY_EQUALS_WARNING!>z1 !== z<!> && z1) {
         EnumClassWithNullableProperty.A.prop_1
         EnumClassWithNullableProperty.A.prop_1<!UNSAFE_CALL!>.<!>equals(null)
         EnumClassWithNullableProperty.A.prop_1.propT
@@ -652,7 +652,7 @@ fun case_33(a: ((Float) -> Int?)?, b: Float?, c: Boolean?) {
 
     } else {
         val x = <!DEBUG_INFO_EXPRESSION_TYPE("kotlin.Int?")!><!UNSAFE_IMPLICIT_INVOKE_CALL!>a<!>(<!DEBUG_INFO_EXPRESSION_TYPE("kotlin.Float? & kotlin.Float")!>b<!>)<!>
-        if (x == z == true && <!SENSELESS_COMPARISON!>x === z<!> || (c != z && !c)) {
+        if (x == z == true && <!FORBIDDEN_IDENTITY_EQUALS_WARNING, SENSELESS_COMPARISON!>x === z<!> || (c != z && !c)) {
 
         } else {
             <!DEBUG_INFO_EXPRESSION_TYPE("kotlin.Int?")!>x<!>
@@ -917,7 +917,7 @@ fun case_51() {
 }
 
 // TESTCASE NUMBER: 52
-val case_52 = if (nullableIntProperty !== nullableNothingProperty && <!SENSELESS_COMPARISON!>nullableNothingProperty != nullableIntProperty<!>) 0 else {
+val case_52 = if (<!FORBIDDEN_IDENTITY_EQUALS_WARNING!>nullableIntProperty !== nullableNothingProperty<!> && <!SENSELESS_COMPARISON!>nullableNothingProperty != nullableIntProperty<!>) 0 else {
     <!DEBUG_INFO_EXPRESSION_TYPE("kotlin.Int?")!>nullableIntProperty<!>
     <!DEBUG_INFO_EXPRESSION_TYPE("kotlin.Int?")!>nullableIntProperty<!>.hashCode()
 }
@@ -1003,7 +1003,7 @@ fun case_57(a: (() -> Unit)) {
  * UNEXPECTED BEHAVIOUR
  */
 fun case_58(a: ((Float) -> Int?)?, b: Float?, z: Nothing?) {
-    if (a === z && b == z || z == a && z === b) {
+    if (a === z && b == z || z == a && <!FORBIDDEN_IDENTITY_EQUALS_WARNING!>z === b<!>) {
         <!DEBUG_INFO_EXPRESSION_TYPE("kotlin.Function1<kotlin.Float, kotlin.Int?>?")!>a<!>
         <!DEBUG_INFO_EXPRESSION_TYPE("kotlin.Float?")!>b<!>
         if (a != z) {

compiler/tests-spec/testData/diagnostics/notLinked/dfa/pos/7.fir.kt

@@ -168,7 +168,7 @@ fun case_9(x: TypealiasNullableString<!REDUNDANT_NULLABLE!>?<!>) {
 fun case_10() {
     val a = Class()
 
-    if (a.prop_4 === null || <!FORBIDDEN_IDENTITY_EQUALS_WARNING, SENSELESS_COMPARISON!>a.prop_4 === null<!> || true) {
+    if (<!FORBIDDEN_IDENTITY_EQUALS_WARNING!>a.prop_4 === null<!> || <!FORBIDDEN_IDENTITY_EQUALS_WARNING, SENSELESS_COMPARISON!>a.prop_4 === null<!> || true) {
         if (a.prop_4 != null) {
             a.prop_4
             a.prop_4.equals(null)
@@ -388,7 +388,7 @@ fun case_20(b: Boolean) {
 // TESTCASE NUMBER: 21
 fun case_21() {
     val y = null
-    if (EnumClassWithNullableProperty.A.prop_1 !== null && <!SENSELESS_COMPARISON!>y != EnumClassWithNullableProperty.A.prop_1<!>) {
+    if (<!FORBIDDEN_IDENTITY_EQUALS_WARNING!>EnumClassWithNullableProperty.A.prop_1 !== null<!> && <!SENSELESS_COMPARISON!>y != EnumClassWithNullableProperty.A.prop_1<!>) {
         EnumClassWithNullableProperty.A.prop_1
         EnumClassWithNullableProperty.A.prop_1.equals(null)
         EnumClassWithNullableProperty.A.prop_1.propT
@@ -421,9 +421,9 @@ fun case_22(a: (() -> Unit)?) {
 
 // TESTCASE NUMBER: 23
 fun case_23(a: ((Float) -> Int?)?, b: Float?, c: Nothing?) {
-    if (a != null && b !== null || a != c && b !== c) {
+    if (a != null && <!FORBIDDEN_IDENTITY_EQUALS_WARNING!>b !== null<!> || a != c && <!FORBIDDEN_IDENTITY_EQUALS_WARNING!>b !== c<!>) {
         val x = <!DEBUG_INFO_EXPRESSION_TYPE("kotlin.Int?")!>a(<!DEBUG_INFO_EXPRESSION_TYPE("kotlin.Float? & kotlin.Float")!>b<!>)<!>
-        if (x != null || <!SENSELESS_COMPARISON!>c !== x<!>) {
+        if (x != null || <!FORBIDDEN_IDENTITY_EQUALS_WARNING, SENSELESS_COMPARISON!>c !== x<!>) {
             <!DEBUG_INFO_EXPRESSION_TYPE("kotlin.Int? & kotlin.Int")!>x<!>
             <!DEBUG_INFO_EXPRESSION_TYPE("kotlin.Int? & kotlin.Int")!>x<!>.equals(null)
             <!DEBUG_INFO_EXPRESSION_TYPE("kotlin.Int? & kotlin.Int")!>x<!>.propT
@@ -533,7 +533,7 @@ fun case_27(y: Nothing?) {
 
 //TESTCASE NUMBER: 28
 fun case_28(a: DeepObject.A.B.C.D.E.F.G.J?) =
-    if (a != null == true == false == false == false == true == false == true == false == false == true == true && a.x !== nullableNothingProperty) {
+    if (a != null == true == false == false == false == true == false == true == false == false == true == true && <!FORBIDDEN_IDENTITY_EQUALS_WARNING!>a.x !== nullableNothingProperty<!>) {
         <!DEBUG_INFO_EXPRESSION_TYPE("DeepObject.A.B.C.D.E.F.G.J? & DeepObject.A.B.C.D.E.F.G.J")!>a<!>.x
         <!DEBUG_INFO_EXPRESSION_TYPE("DeepObject.A.B.C.D.E.F.G.J? & DeepObject.A.B.C.D.E.F.G.J")!>a<!>.equals(null)
         <!DEBUG_INFO_EXPRESSION_TYPE("DeepObject.A.B.C.D.E.F.G.J? & DeepObject.A.B.C.D.E.F.G.J")!>a<!>.propT
@@ -547,13 +547,13 @@ fun case_28(a: DeepObject.A.B.C.D.E.F.G.J?) =
     } else -1
 
 // TESTCASE NUMBER: 29
-fun case_29(a: Int?, b: Nothing?, c: Int = if (a === b) 0 else a) {
+fun case_29(a: Int?, b: Nothing?, c: Int = if (<!FORBIDDEN_IDENTITY_EQUALS_WARNING!>a === b<!>) 0 else a) {
     <!DEBUG_INFO_EXPRESSION_TYPE("kotlin.Int?")!>a<!>
     <!DEBUG_INFO_EXPRESSION_TYPE("kotlin.Nothing?")!>b<!>
 }
 
 // TESTCASE NUMBER: 30
-fun case_30(a: Int?, b: Nothing?, c: Int = if (a === b || <!SENSELESS_COMPARISON!>a == null<!>) 0 else a) {
+fun case_30(a: Int?, b: Nothing?, c: Int = if (<!FORBIDDEN_IDENTITY_EQUALS_WARNING!>a === b<!> || <!SENSELESS_COMPARISON!>a == null<!>) 0 else a) {
     <!DEBUG_INFO_EXPRESSION_TYPE("kotlin.Int?")!>a<!>
     <!DEBUG_INFO_EXPRESSION_TYPE("kotlin.Nothing?")!>b<!>
 }