Fix exception on 'equals()' returning 'Nothing' in inline class

^KT-54401: Fixed

compiler/ir/backend.jvm/lower/src/org/jetbrains/kotlin/backend/jvm/lower/JvmInlineClassLowering.kt

@@ -486,7 +486,7 @@ private class JvmInlineClassLowering(context: JvmBackendContext) : JvmValueClass
         val type = left.type.unboxInlineClass()
 
         val typedEqualsStaticReplacement = findStaticReplacementForTypedEquals(valueClass)
-        val untypedEquals = valueClass.functions.single { overridesEqualsFromAny(it) }
+        val untypedEquals = valueClass.functions.single { it.overridesEqualsFromAny }
 
         function.body = context.createIrBuilder(valueClass.symbol).run {
             irExprBody(
@@ -515,13 +515,6 @@ private class JvmInlineClassLowering(context: JvmBackendContext) : JvmValueClass
         valueClass.declarations += function
     }
 
-    private fun overridesEqualsFromAny(irFunction: IrFunction): Boolean {
-        return irFunction.run {
-            name == EQUALS && returnType.isBoolean() && valueParameters.size == 1
-                    && valueParameters[0].type.isNullableAny() && contextReceiverParametersCount == 0 && extensionReceiverParameter == null
-        }
-    }
-
     private fun findStaticReplacementForTypedEquals(valueClass: IrClass): IrFunction? {
         fun isTypedEquals(irFunction: IrFunction): Boolean {
             return irFunction.run {

compiler/ir/ir.tree/src/org/jetbrains/kotlin/ir/util/IrUtils.kt

@@ -1304,3 +1304,7 @@ fun IrBuiltIns.getKFunctionType(returnType: IrType, parameterTypes: List<IrType>
 
 fun IdSignature?.isComposite(): Boolean =
     this is IdSignature.CompositeSignature
+
+val IrFunction.overridesEqualsFromAny
+    get() = name == OperatorNameConventions.EQUALS && valueParameters.size == 1 && valueParameters[0].type.isNullableAny()
+            && contextReceiverParametersCount == 0 && extensionReceiverParameter == null

compiler/testData/codegen/box/inlineClasses/inlineClassEqualsOverride.kt

@@ -28,6 +28,11 @@ value class IC3(val value: Int) {
 
 }
 
+OPTIONAL_JVM_INLINE_ANNOTATION
+value class IC4(val value: Int) {
+    override fun equals(other: Any?) = TODO()
+}
+
 fun box() =
     if (IC1(1.0) == IC1(1.05) && IC1(1.0) != IC1(1.2)
         && IC2(5) == IC2(6) && IC2(5) != IC2(7)