KT-53465, KT-53677 Get rid of unnecessary checkcasts to array of reified type

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

@@ -19,6 +19,7 @@ import org.jetbrains.kotlin.backend.jvm.JvmLoweredDeclarationOrigin
 import org.jetbrains.kotlin.backend.jvm.ir.*
 import org.jetbrains.kotlin.backend.jvm.unboxInlineClass
 import org.jetbrains.kotlin.descriptors.DescriptorVisibilities
+import org.jetbrains.kotlin.ir.IrBuiltIns
 import org.jetbrains.kotlin.ir.IrElement
 import org.jetbrains.kotlin.ir.IrStatement
 import org.jetbrains.kotlin.ir.UNDEFINED_OFFSET
@@ -36,6 +37,9 @@ import org.jetbrains.kotlin.ir.visitors.IrElementVisitorVoid
 import org.jetbrains.kotlin.ir.visitors.acceptChildrenVoid
 import org.jetbrains.kotlin.ir.visitors.acceptVoid
 import org.jetbrains.kotlin.name.Name
+import org.jetbrains.kotlin.types.Variance
+import org.jetbrains.kotlin.types.checker.SimpleClassicTypeSystemContext.getArgument
+import org.jetbrains.kotlin.types.checker.SimpleClassicTypeSystemContext.isTypeVariableType
 import org.jetbrains.kotlin.utils.addToStdlib.safeAs
 import org.jetbrains.org.objectweb.asm.Handle
 import org.jetbrains.org.objectweb.asm.Opcodes
@@ -88,6 +92,8 @@ private class TypeOperatorLowering(private val backendContext: JvmBackendContext
                 builder.irAs(argument, type)
             argument.type.isInlineClassType() && argument.type.isSubtypeOfClass(type.erasedUpperBound.symbol) ->
                 argument
+            isCompatibleArrayType(argument.type, type) ->
+                argument
             type.isNullable() || argument.isDefinitelyNotNull() ->
                 builder.irAs(argument, type)
             else -> {
@@ -121,6 +127,22 @@ private class TypeOperatorLowering(private val backendContext: JvmBackendContext
             }
         }
 
+    private fun isCompatibleArrayType(actualType: IrType, expectedType: IrType): Boolean {
+        var actual = actualType
+        var expected = expectedType
+        while ((actual.isArray() || actual.isNullableArray()) && (expected.isArray() || expected.isNullableArray())) {
+            actual = actual.getArrayElementLowerType()
+            expected = expected.getArrayElementLowerType()
+        }
+        if (actual == actualType || expected == expectedType) return false
+        return actual.isSubtypeOfClass(expected.erasedUpperBound.symbol)
+    }
+
+    private fun IrType.getArrayElementLowerType(): IrType =
+        if (isBoxedArray && this is IrSimpleType && (arguments.singleOrNull() as? IrTypeProjection)?.variance == Variance.IN_VARIANCE)
+            backendContext.irBuiltIns.anyNType
+        else getArrayElementType(backendContext.irBuiltIns)
+
     // TODO extract null check elimination on IR somewhere?
     private fun IrExpression.isDefinitelyNotNull(): Boolean =
         when (this) {