JVM IR: Don't generate null checks on value parameters of private operator functions

The null check on the extension receiver of private operator functions
is a special case and doesn't extend to value parameters.

compiler/fir/fir2ir/tests/org/jetbrains/kotlin/codegen/ir/FirBlackBoxCodegenTestGenerated.java

@@ -16119,6 +16119,11 @@ public class FirBlackBoxCodegenTestGenerated extends AbstractFirBlackBoxCodegenT
                 runTest("compiler/testData/codegen/box/javaInterop/notNullAssertions/paramAssertionMessage.kt");
             }
 
+            @TestMetadata("privateOperatorParameterAssertions.kt")
+            public void testPrivateOperatorParameterAssertions() throws Exception {
+                runTest("compiler/testData/codegen/box/javaInterop/notNullAssertions/privateOperatorParameterAssertions.kt");
+            }
+
             @TestMetadata("staticCallErrorMessage.kt")
             public void testStaticCallErrorMessage() throws Exception {
                 runTest("compiler/testData/codegen/box/javaInterop/notNullAssertions/staticCallErrorMessage.kt");

compiler/ir/backend.jvm/src/org/jetbrains/kotlin/backend/jvm/codegen/ExpressionCodegen.kt

@@ -305,7 +305,12 @@ class ExpressionCodegen(
             return
 
         irFunction.extensionReceiverParameter?.let { generateNonNullAssertion(it) }
-        irFunction.valueParameters.forEach(::generateNonNullAssertion)
+
+        // Private operator functions don't have null checks on value parameters,
+        // see `DescriptorAsmUtil.genNotNullAssertionsForParameters`.
+        if (!DescriptorVisibilities.isPrivate(irFunction.visibility) || irFunction !is IrSimpleFunction || !irFunction.isOperator) {
+            irFunction.valueParameters.forEach(::generateNonNullAssertion)
+        }
     }
 
     private fun generateNonNullAssertion(param: IrValueParameter) {

compiler/testData/codegen/box/javaInterop/notNullAssertions/privateOperatorParameterAssertions.kt

@@ -0,0 +1,62 @@
+// TARGET_BACKEND: JVM
+// WITH_REFLECT
+
+var result: String? = "fail"
+
+class X
+
+class A {
+    // There should be a null check on the extension receiver of private
+    // operator functions, but no null checks on all other arguments.
+
+    private operator fun X.get(name: String) = "$name$result"
+
+    private operator fun X.set(name: String, v: String) {
+        result = v
+    }
+
+    private fun getMethod(name: String) =
+        A::class.java.getDeclaredMethods().first { it.name == name }
+
+    fun test(): String {
+        val setter = getMethod("set")
+        try {
+            setter.invoke(this, X(), null, null)
+        } catch (e: Throwable) {
+            return "Fail 1"
+        }
+
+        try {
+            setter.invoke(this, null, null, null)
+            return "Fail 2"
+        } catch (e: Throwable) {
+            // expected
+            if (e.cause !is NullPointerException) {
+                return "Fail 3"
+            }
+        }
+
+        val getter = getMethod("get")
+        val s = try {
+            getter.invoke(this, X(), null) as String
+        } catch (e: Throwable) {
+            return "Fail 4"
+        }
+
+        try {
+            getter.invoke(this, null, null)
+            return "Fail 5"
+        } catch (e: Throwable) {
+            // expected
+            if (e.cause !is NullPointerException) {
+                return "Fail 6"
+            }
+        }
+
+        return if (s == "nullnull") "OK" else "Fail 7"
+    }
+}
+
+fun box(): String {
+    return A().test()
+}

compiler/tests/org/jetbrains/kotlin/codegen/BlackBoxCodegenTestGenerated.java

@@ -17519,6 +17519,11 @@ public class BlackBoxCodegenTestGenerated extends AbstractBlackBoxCodegenTest {
                 runTest("compiler/testData/codegen/box/javaInterop/notNullAssertions/paramAssertionMessage.kt");
             }
 
+            @TestMetadata("privateOperatorParameterAssertions.kt")
+            public void testPrivateOperatorParameterAssertions() throws Exception {
+                runTest("compiler/testData/codegen/box/javaInterop/notNullAssertions/privateOperatorParameterAssertions.kt");
+            }
+
             @TestMetadata("staticCallErrorMessage.kt")
             public void testStaticCallErrorMessage() throws Exception {
                 runTest("compiler/testData/codegen/box/javaInterop/notNullAssertions/staticCallErrorMessage.kt");

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

@@ -17519,6 +17519,11 @@ public class LightAnalysisModeTestGenerated extends AbstractLightAnalysisModeTes
                 runTest("compiler/testData/codegen/box/javaInterop/notNullAssertions/paramAssertionMessage.kt");
             }
 
+            @TestMetadata("privateOperatorParameterAssertions.kt")
+            public void testPrivateOperatorParameterAssertions() throws Exception {
+                runTest("compiler/testData/codegen/box/javaInterop/notNullAssertions/privateOperatorParameterAssertions.kt");
+            }
+
             @TestMetadata("staticCallErrorMessage.kt")
             public void testStaticCallErrorMessage() throws Exception {
                 runTest("compiler/testData/codegen/box/javaInterop/notNullAssertions/staticCallErrorMessage.kt");

compiler/tests/org/jetbrains/kotlin/codegen/ir/IrBlackBoxCodegenTestGenerated.java

@@ -16119,6 +16119,11 @@ public class IrBlackBoxCodegenTestGenerated extends AbstractIrBlackBoxCodegenTes
                 runTest("compiler/testData/codegen/box/javaInterop/notNullAssertions/paramAssertionMessage.kt");
             }
 
+            @TestMetadata("privateOperatorParameterAssertions.kt")
+            public void testPrivateOperatorParameterAssertions() throws Exception {
+                runTest("compiler/testData/codegen/box/javaInterop/notNullAssertions/privateOperatorParameterAssertions.kt");
+            }
+
             @TestMetadata("staticCallErrorMessage.kt")
             public void testStaticCallErrorMessage() throws Exception {
                 runTest("compiler/testData/codegen/box/javaInterop/notNullAssertions/staticCallErrorMessage.kt");