JVM IR: do not try to optimize casts in TypeOperatorLowering

In case the cast value is used as a receiver to a private method call,
the cast is actually necessary, see KT-48927. Also, this optimization
has backfired once already (see kt48659_identityEqualsWithCastToAny.kt).
It seems that the best way to optimize these casts is not to generate
them in the first place, and/or use bytecode postprocessing.

Apparently the only kind of casts which need to be eliminated are those
which occur on an inline class to its supertype. Otherwise the
unsafe-coerce intrinsic is inserted at the incorrect place, and several
tests fail (uncastInlineClassToAnyAndBack.kt, genericOverride.kt,
classGenericOverride.kt).

 #KT-48927 Fixed

compiler/fir/fir2ir/tests-gen/org/jetbrains/kotlin/test/runners/codegen/FirBlackBoxCodegenTestGenerated.java

@@ -4340,6 +4340,12 @@ public class FirBlackBoxCodegenTestGenerated extends AbstractFirBlackBoxCodegenT
             runTest("compiler/testData/codegen/box/casts/kt22714.kt");
         }
 
+        @Test
+        @TestMetadata("kt48927_privateMethodOnDerivedCastToBase.kt")
+        public void testKt48927_privateMethodOnDerivedCastToBase() throws Exception {
+            runTest("compiler/testData/codegen/box/casts/kt48927_privateMethodOnDerivedCastToBase.kt");
+        }
+
         @Test
         @TestMetadata("lambdaToUnitCast.kt")
         public void testLambdaToUnitCast() throws Exception {
@@ -19905,6 +19911,12 @@ public class FirBlackBoxCodegenTestGenerated extends AbstractFirBlackBoxCodegenT
                 runTest("compiler/testData/codegen/box/inlineClasses/boxReturnValueOnOverride/relatedReturnTypes2b.kt");
             }
 
+            @Test
+            @TestMetadata("uncastInlineClassToAnyAndBack.kt")
+            public void testUncastInlineClassToAnyAndBack() throws Exception {
+                runTest("compiler/testData/codegen/box/inlineClasses/boxReturnValueOnOverride/uncastInlineClassToAnyAndBack.kt");
+            }
+
             @Test
             @TestMetadata("unrelatedGenerics.kt")
             public void testUnrelatedGenerics() throws Exception {

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

@@ -93,8 +93,7 @@ private class TypeOperatorLowering(private val context: JvmBackendContext) : Fil
                     )
                 }
             }
-        // Do not optimize casts for values of primitive types because it can affect their identity and thus change behavior.
-        !argument.type.isPrimitiveType() && argument.type.isSubtypeOfClass(type.erasedUpperBound.symbol) ->
+        argument.type.isInlineClassType() && argument.type.isSubtypeOfClass(type.erasedUpperBound.symbol) ->
             argument
         else ->
             builder.irAs(argument, type)

compiler/testData/codegen/box/casts/kt48927_privateMethodOnDerivedCastToBase.kt

@@ -0,0 +1,9 @@
+abstract class Base {
+    private fun test(): String = "OK"
+
+    fun test(d: Derived): String = (d as Base).test()
+}
+
+class Derived : Base()
+
+fun box(): String = Derived().test(Derived())

compiler/testData/codegen/box/inlineClasses/boxReturnValueOnOverride/uncastInlineClassToAnyAndBack.kt

@@ -0,0 +1,14 @@
+inline class X(val x: Any)
+
+interface IFoo<T> {
+    fun foo(): T
+}
+
+class TestX : IFoo<X> {
+    override fun foo(): X = X("OK")
+}
+
+fun box(): String {
+    val t: IFoo<X> = TestX()
+    return ((t.foo() as Any) as X).x.toString()
+}

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

@@ -4268,6 +4268,12 @@ public class BlackBoxCodegenTestGenerated extends AbstractBlackBoxCodegenTest {
             runTest("compiler/testData/codegen/box/casts/kt22714.kt");
         }
 
+        @Test
+        @TestMetadata("kt48927_privateMethodOnDerivedCastToBase.kt")
+        public void testKt48927_privateMethodOnDerivedCastToBase() throws Exception {
+            runTest("compiler/testData/codegen/box/casts/kt48927_privateMethodOnDerivedCastToBase.kt");
+        }
+
         @Test
         @TestMetadata("lambdaToUnitCast.kt")
         public void testLambdaToUnitCast() throws Exception {
@@ -19773,6 +19779,12 @@ public class BlackBoxCodegenTestGenerated extends AbstractBlackBoxCodegenTest {
                 runTest("compiler/testData/codegen/box/inlineClasses/boxReturnValueOnOverride/relatedReturnTypes2b.kt");
             }
 
+            @Test
+            @TestMetadata("uncastInlineClassToAnyAndBack.kt")
+            public void testUncastInlineClassToAnyAndBack() throws Exception {
+                runTest("compiler/testData/codegen/box/inlineClasses/boxReturnValueOnOverride/uncastInlineClassToAnyAndBack.kt");
+            }
+
             @Test
             @TestMetadata("unrelatedGenerics.kt")
             public void testUnrelatedGenerics() throws Exception {

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

@@ -4340,6 +4340,12 @@ public class IrBlackBoxCodegenTestGenerated extends AbstractIrBlackBoxCodegenTes
             runTest("compiler/testData/codegen/box/casts/kt22714.kt");
         }
 
+        @Test
+        @TestMetadata("kt48927_privateMethodOnDerivedCastToBase.kt")
+        public void testKt48927_privateMethodOnDerivedCastToBase() throws Exception {
+            runTest("compiler/testData/codegen/box/casts/kt48927_privateMethodOnDerivedCastToBase.kt");
+        }
+
         @Test
         @TestMetadata("lambdaToUnitCast.kt")
         public void testLambdaToUnitCast() throws Exception {
@@ -19905,6 +19911,12 @@ public class IrBlackBoxCodegenTestGenerated extends AbstractIrBlackBoxCodegenTes
                 runTest("compiler/testData/codegen/box/inlineClasses/boxReturnValueOnOverride/relatedReturnTypes2b.kt");
             }
 
+            @Test
+            @TestMetadata("uncastInlineClassToAnyAndBack.kt")
+            public void testUncastInlineClassToAnyAndBack() throws Exception {
+                runTest("compiler/testData/codegen/box/inlineClasses/boxReturnValueOnOverride/uncastInlineClassToAnyAndBack.kt");
+            }
+
             @Test
             @TestMetadata("unrelatedGenerics.kt")
             public void testUnrelatedGenerics() throws Exception {

compiler/tests-gen/org/jetbrains/kotlin/codegen/LightAnalysisModeTestGenerated.java

@@ -3729,6 +3729,11 @@ public class LightAnalysisModeTestGenerated extends AbstractLightAnalysisModeTes
             runTest("compiler/testData/codegen/box/casts/kt22714.kt");
         }
 
+        @TestMetadata("kt48927_privateMethodOnDerivedCastToBase.kt")
+        public void testKt48927_privateMethodOnDerivedCastToBase() throws Exception {
+            runTest("compiler/testData/codegen/box/casts/kt48927_privateMethodOnDerivedCastToBase.kt");
+        }
+
         @TestMetadata("lambdaToUnitCast.kt")
         public void testLambdaToUnitCast() throws Exception {
             runTest("compiler/testData/codegen/box/casts/lambdaToUnitCast.kt");
@@ -16415,6 +16420,11 @@ public class LightAnalysisModeTestGenerated extends AbstractLightAnalysisModeTes
                 runTest("compiler/testData/codegen/box/inlineClasses/boxReturnValueOnOverride/relatedReturnTypes2b.kt");
             }
 
+            @TestMetadata("uncastInlineClassToAnyAndBack.kt")
+            public void testUncastInlineClassToAnyAndBack() throws Exception {
+                runTest("compiler/testData/codegen/box/inlineClasses/boxReturnValueOnOverride/uncastInlineClassToAnyAndBack.kt");
+            }
+
             @TestMetadata("unrelatedGenerics.kt")
             public void testUnrelatedGenerics() throws Exception {
                 runTest("compiler/testData/codegen/box/inlineClasses/boxReturnValueOnOverride/unrelatedGenerics.kt");

js/js.tests/tests-gen/org/jetbrains/kotlin/js/test/es6/semantics/IrJsCodegenBoxES6TestGenerated.java

@@ -2844,6 +2844,11 @@ public class IrJsCodegenBoxES6TestGenerated extends AbstractIrJsCodegenBoxES6Tes
             runTest("compiler/testData/codegen/box/casts/kt22714.kt");
         }
 
+        @TestMetadata("kt48927_privateMethodOnDerivedCastToBase.kt")
+        public void testKt48927_privateMethodOnDerivedCastToBase() throws Exception {
+            runTest("compiler/testData/codegen/box/casts/kt48927_privateMethodOnDerivedCastToBase.kt");
+        }
+
         @TestMetadata("lambdaToUnitCast.kt")
         public void testLambdaToUnitCast() throws Exception {
             runTest("compiler/testData/codegen/box/casts/lambdaToUnitCast.kt");
@@ -14399,6 +14404,11 @@ public class IrJsCodegenBoxES6TestGenerated extends AbstractIrJsCodegenBoxES6Tes
                 runTest("compiler/testData/codegen/box/inlineClasses/boxReturnValueOnOverride/relatedReturnTypes2b.kt");
             }
 
+            @TestMetadata("uncastInlineClassToAnyAndBack.kt")
+            public void testUncastInlineClassToAnyAndBack() throws Exception {
+                runTest("compiler/testData/codegen/box/inlineClasses/boxReturnValueOnOverride/uncastInlineClassToAnyAndBack.kt");
+            }
+
             @TestMetadata("unrelatedGenerics.kt")
             public void testUnrelatedGenerics() throws Exception {
                 runTest("compiler/testData/codegen/box/inlineClasses/boxReturnValueOnOverride/unrelatedGenerics.kt");

js/js.tests/tests-gen/org/jetbrains/kotlin/js/test/ir/semantics/IrJsCodegenBoxTestGenerated.java

@@ -2844,6 +2844,11 @@ public class IrJsCodegenBoxTestGenerated extends AbstractIrJsCodegenBoxTest {
             runTest("compiler/testData/codegen/box/casts/kt22714.kt");
         }
 
+        @TestMetadata("kt48927_privateMethodOnDerivedCastToBase.kt")
+        public void testKt48927_privateMethodOnDerivedCastToBase() throws Exception {
+            runTest("compiler/testData/codegen/box/casts/kt48927_privateMethodOnDerivedCastToBase.kt");
+        }
+
         @TestMetadata("lambdaToUnitCast.kt")
         public void testLambdaToUnitCast() throws Exception {
             runTest("compiler/testData/codegen/box/casts/lambdaToUnitCast.kt");
@@ -13805,6 +13810,11 @@ public class IrJsCodegenBoxTestGenerated extends AbstractIrJsCodegenBoxTest {
                 runTest("compiler/testData/codegen/box/inlineClasses/boxReturnValueOnOverride/relatedReturnTypes2b.kt");
             }
 
+            @TestMetadata("uncastInlineClassToAnyAndBack.kt")
+            public void testUncastInlineClassToAnyAndBack() throws Exception {
+                runTest("compiler/testData/codegen/box/inlineClasses/boxReturnValueOnOverride/uncastInlineClassToAnyAndBack.kt");
+            }
+
             @TestMetadata("unrelatedGenerics.kt")
             public void testUnrelatedGenerics() throws Exception {
                 runTest("compiler/testData/codegen/box/inlineClasses/boxReturnValueOnOverride/unrelatedGenerics.kt");

js/js.tests/tests-gen/org/jetbrains/kotlin/js/test/semantics/JsCodegenBoxTestGenerated.java

@@ -2809,6 +2809,11 @@ public class JsCodegenBoxTestGenerated extends AbstractJsCodegenBoxTest {
             runTest("compiler/testData/codegen/box/casts/kt22714.kt");
         }
 
+        @TestMetadata("kt48927_privateMethodOnDerivedCastToBase.kt")
+        public void testKt48927_privateMethodOnDerivedCastToBase() throws Exception {
+            runTest("compiler/testData/codegen/box/casts/kt48927_privateMethodOnDerivedCastToBase.kt");
+        }
+
         @TestMetadata("lambdaToUnitCast.kt")
         public void testLambdaToUnitCast() throws Exception {
             runTest("compiler/testData/codegen/box/casts/lambdaToUnitCast.kt");
@@ -13835,6 +13840,11 @@ public class JsCodegenBoxTestGenerated extends AbstractJsCodegenBoxTest {
                 runTest("compiler/testData/codegen/box/inlineClasses/boxReturnValueOnOverride/relatedReturnTypes2b.kt");
             }
 
+            @TestMetadata("uncastInlineClassToAnyAndBack.kt")
+            public void testUncastInlineClassToAnyAndBack() throws Exception {
+                runTest("compiler/testData/codegen/box/inlineClasses/boxReturnValueOnOverride/uncastInlineClassToAnyAndBack.kt");
+            }
+
             @TestMetadata("unrelatedGenerics.kt")
             public void testUnrelatedGenerics() throws Exception {
                 runTest("compiler/testData/codegen/box/inlineClasses/boxReturnValueOnOverride/unrelatedGenerics.kt");

js/js.tests/tests-gen/org/jetbrains/kotlin/js/test/wasm/semantics/IrCodegenBoxWasmTestGenerated.java

@@ -2349,6 +2349,11 @@ public class IrCodegenBoxWasmTestGenerated extends AbstractIrCodegenBoxWasmTest
             runTest("compiler/testData/codegen/box/casts/kt22714.kt");
         }
 
+        @TestMetadata("kt48927_privateMethodOnDerivedCastToBase.kt")
+        public void testKt48927_privateMethodOnDerivedCastToBase() throws Exception {
+            runTest("compiler/testData/codegen/box/casts/kt48927_privateMethodOnDerivedCastToBase.kt");
+        }
+
         @TestMetadata("lambdaToUnitCast.kt")
         public void testLambdaToUnitCast() throws Exception {
             runTest("compiler/testData/codegen/box/casts/lambdaToUnitCast.kt");
@@ -8684,6 +8689,11 @@ public class IrCodegenBoxWasmTestGenerated extends AbstractIrCodegenBoxWasmTest
                 runTest("compiler/testData/codegen/box/inlineClasses/boxReturnValueOnOverride/relatedReturnTypes2b.kt");
             }
 
+            @TestMetadata("uncastInlineClassToAnyAndBack.kt")
+            public void testUncastInlineClassToAnyAndBack() throws Exception {
+                runTest("compiler/testData/codegen/box/inlineClasses/boxReturnValueOnOverride/uncastInlineClassToAnyAndBack.kt");
+            }
+
             @TestMetadata("unrelatedGenerics.kt")
             public void testUnrelatedGenerics() throws Exception {
                 runTest("compiler/testData/codegen/box/inlineClasses/boxReturnValueOnOverride/unrelatedGenerics.kt");