JVM: consider casts of null to be redundant

These should only have ever been necessary for field type inference in
coroutines, which should have been fixed by 0fc676a20c.

Unlike 903a5d69a4, this time the change is in an optimization pass.
Advantage: optimization passes have a closer to the JVM view of the
bytecode, which makes this change significantly more likely to be correct.
Disadvantage: technically we don't really guarantee optimization passes
other than FixStack will run at all. For KT-54581 this is 100% fine
since the problem itself is caused by redundant checkcast elimination in
the first place (otherwise there would've been a redundant cast to
String), but for KT-53146 this means the fix is somewhat incidental and
not necessarily guaranteed.

^KT-53146 Fixed
^KT-54581 Fixed

compiler/backend/src/org/jetbrains/kotlin/codegen/optimization/RedundantCheckCastElimination.kt

@@ -20,6 +20,7 @@ import org.jetbrains.kotlin.codegen.inline.ReifiedTypeInliner
 import org.jetbrains.kotlin.codegen.optimization.common.FastMethodAnalyzer
 import org.jetbrains.kotlin.codegen.optimization.common.InstructionLivenessAnalyzer
 import org.jetbrains.kotlin.codegen.optimization.common.OptimizationBasicInterpreter
+import org.jetbrains.kotlin.codegen.optimization.common.StrictBasicValue
 import org.jetbrains.kotlin.codegen.optimization.fixStack.top
 import org.jetbrains.kotlin.codegen.optimization.transformer.MethodTransformer
 import org.jetbrains.org.objectweb.asm.Opcodes
@@ -52,13 +53,12 @@ class RedundantCheckCastEliminationMethodTransformer : MethodTransformer() {
 
         val frames = FastMethodAnalyzer(internalClassName, methodNode, interpreter, pruneExceptionEdges = true).analyze()
         for (i in insns.indices) {
-            val valueType = frames[i]?.top()?.type ?: continue
             val insn = insns[i]
-
             if (insn.opcode == Opcodes.CHECKCAST) {
+                val value = frames[i]?.top() ?: continue
                 val typeInsn = insn as TypeInsnNode
                 val insnType = Type.getObjectType(typeInsn.desc)
-                if (!isTrivialSubtype(insnType, valueType)) continue
+                if (value !== StrictBasicValue.NULL_VALUE && !isTrivialSubtype(insnType, value.type)) continue
 
                 //Keep casts to multiarray types cause dex doesn't recognize ANEWARRAY [Ljava/lang/Object; as Object [][], but Object [] type
                 //It's not clear is it bug in dex or not and maybe best to distinguish such types from MULTINEWARRRAY ones in method analyzer

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

@@ -4787,6 +4787,12 @@ public class FirBlackBoxCodegenTestGenerated extends AbstractFirBlackBoxCodegenT
             runTest("compiler/testData/codegen/box/casts/kt50577.kt");
         }
 
+        @Test
+        @TestMetadata("kt53146.kt")
+        public void testKt53146() throws Exception {
+            runTest("compiler/testData/codegen/box/casts/kt53146.kt");
+        }
+
         @Test
         @TestMetadata("kt53677.kt")
         public void testKt53677() throws Exception {
@@ -4799,6 +4805,12 @@ public class FirBlackBoxCodegenTestGenerated extends AbstractFirBlackBoxCodegenT
             runTest("compiler/testData/codegen/box/casts/kt54318.kt");
         }
 
+        @Test
+        @TestMetadata("kt54581.kt")
+        public void testKt54581() throws Exception {
+            runTest("compiler/testData/codegen/box/casts/kt54581.kt");
+        }
+
         @Test
         @TestMetadata("lambdaToUnitCast.kt")
         public void testLambdaToUnitCast() throws Exception {

compiler/testData/codegen/box/casts/kt53146.kt

@@ -0,0 +1,18 @@
+// TARGET_BACKEND: JVM_IR
+// WITH_STDLIB
+// FULL_JDK
+// CHECK_BYTECODE_TEXT
+
+class A
+
+fun box(): String {
+    val a = try {
+        A()
+    } catch (e: NoClassDefFoundError) {
+        null
+    }
+
+    return "OK"
+}
+
+// 0 CHECKCAST

compiler/testData/codegen/box/casts/kt54581.kt

@@ -0,0 +1,17 @@
+// TARGET_BACKEND: JVM
+
+fun box(): String {
+    val k = tryOrNull { "K" }
+    return "O$k"
+}
+
+private inline fun <T> tryOrNull(action: () -> T): T? =
+    try {
+        action()
+    } catch (e: Throwable) {
+        when {
+            else -> {
+                null
+            }
+        }
+    }

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

@@ -4673,6 +4673,12 @@ public class BlackBoxCodegenTestGenerated extends AbstractBlackBoxCodegenTest {
             runTest("compiler/testData/codegen/box/casts/kt50577.kt");
         }
 
+        @Test
+        @TestMetadata("kt54581.kt")
+        public void testKt54581() throws Exception {
+            runTest("compiler/testData/codegen/box/casts/kt54581.kt");
+        }
+
         @Test
         @TestMetadata("lambdaToUnitCast.kt")
         public void testLambdaToUnitCast() throws Exception {

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

@@ -4787,6 +4787,12 @@ public class IrBlackBoxCodegenTestGenerated extends AbstractIrBlackBoxCodegenTes
             runTest("compiler/testData/codegen/box/casts/kt50577.kt");
         }
 
+        @Test
+        @TestMetadata("kt53146.kt")
+        public void testKt53146() throws Exception {
+            runTest("compiler/testData/codegen/box/casts/kt53146.kt");
+        }
+
         @Test
         @TestMetadata("kt53677.kt")
         public void testKt53677() throws Exception {
@@ -4799,6 +4805,12 @@ public class IrBlackBoxCodegenTestGenerated extends AbstractIrBlackBoxCodegenTes
             runTest("compiler/testData/codegen/box/casts/kt54318.kt");
         }
 
+        @Test
+        @TestMetadata("kt54581.kt")
+        public void testKt54581() throws Exception {
+            runTest("compiler/testData/codegen/box/casts/kt54581.kt");
+        }
+
         @Test
         @TestMetadata("lambdaToUnitCast.kt")
         public void testLambdaToUnitCast() throws Exception {

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

@@ -4076,6 +4076,11 @@ public class LightAnalysisModeTestGenerated extends AbstractLightAnalysisModeTes
             runTest("compiler/testData/codegen/box/casts/kt50577.kt");
         }
 
+        @TestMetadata("kt54581.kt")
+        public void testKt54581() throws Exception {
+            runTest("compiler/testData/codegen/box/casts/kt54581.kt");
+        }
+
         @TestMetadata("lambdaToUnitCast.kt")
         public void testLambdaToUnitCast() throws Exception {
             runTest("compiler/testData/codegen/box/casts/lambdaToUnitCast.kt");