JVM: do not put public field access into a single expression block

It affects the `is IrGetField` check in
TypeOperatorLowering.computeNotNullAssertionText, which leads to missing
NPE messages when accessing backing fields of public properties.

 #KT-64615

analysis/low-level-api-fir/tests/org/jetbrains/kotlin/analysis/low/level/api/fir/diagnostic/compiler/based/LLFirBlackBoxCodegenBasedTestGenerated.java

@@ -31436,6 +31436,12 @@ public class LLFirBlackBoxCodegenBasedTestGenerated extends AbstractLLFirBlackBo
                     KtTestUtil.assertAllTestsPresentByMetadataWithExcluded(this.getClass(), new File("compiler/testData/codegen/box/javaInterop/notNullAssertions/expressionAssertionMessages"), Pattern.compile("^(.+)\\.kt$"), null, true);
                 }
 
+                @Test
+                @TestMetadata("backingField.kt")
+                public void testBackingField() throws Exception {
+                    runTest("compiler/testData/codegen/box/javaInterop/notNullAssertions/expressionAssertionMessages/backingField.kt");
+                }
+
                 @Test
                 @TestMetadata("field_after.kt")
                 public void testField_after() throws Exception {

analysis/low-level-api-fir/tests/org/jetbrains/kotlin/analysis/low/level/api/fir/diagnostic/compiler/based/LLFirReversedBlackBoxCodegenBasedTestGenerated.java

@@ -31436,6 +31436,12 @@ public class LLFirReversedBlackBoxCodegenBasedTestGenerated extends AbstractLLFi
                     KtTestUtil.assertAllTestsPresentByMetadataWithExcluded(this.getClass(), new File("compiler/testData/codegen/box/javaInterop/notNullAssertions/expressionAssertionMessages"), Pattern.compile("^(.+)\\.kt$"), null, true);
                 }
 
+                @Test
+                @TestMetadata("backingField.kt")
+                public void testBackingField() throws Exception {
+                    runTest("compiler/testData/codegen/box/javaInterop/notNullAssertions/expressionAssertionMessages/backingField.kt");
+                }
+
                 @Test
                 @TestMetadata("field_after.kt")
                 public void testField_after() throws Exception {

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

@@ -31045,6 +31045,12 @@ public class FirLightTreeBlackBoxCodegenTestGenerated extends AbstractFirLightTr
                     KtTestUtil.assertAllTestsPresentByMetadataWithExcluded(this.getClass(), new File("compiler/testData/codegen/box/javaInterop/notNullAssertions/expressionAssertionMessages"), Pattern.compile("^(.+)\\.kt$"), null, TargetBackend.JVM_IR, true);
                 }
 
+                @Test
+                @TestMetadata("backingField.kt")
+                public void testBackingField() throws Exception {
+                    runTest("compiler/testData/codegen/box/javaInterop/notNullAssertions/expressionAssertionMessages/backingField.kt");
+                }
+
                 @Test
                 @TestMetadata("field_after.kt")
                 public void testField_after() throws Exception {

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

@@ -31045,6 +31045,12 @@ public class FirLightTreeBlackBoxCodegenWithIrFakeOverrideGeneratorTestGenerated
                     KtTestUtil.assertAllTestsPresentByMetadataWithExcluded(this.getClass(), new File("compiler/testData/codegen/box/javaInterop/notNullAssertions/expressionAssertionMessages"), Pattern.compile("^(.+)\\.kt$"), null, TargetBackend.JVM_IR, true);
                 }
 
+                @Test
+                @TestMetadata("backingField.kt")
+                public void testBackingField() throws Exception {
+                    runTest("compiler/testData/codegen/box/javaInterop/notNullAssertions/expressionAssertionMessages/backingField.kt");
+                }
+
                 @Test
                 @TestMetadata("field_after.kt")
                 public void testField_after() throws Exception {

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

@@ -31045,6 +31045,12 @@ public class FirPsiBlackBoxCodegenTestGenerated extends AbstractFirPsiBlackBoxCo
                     KtTestUtil.assertAllTestsPresentByMetadataWithExcluded(this.getClass(), new File("compiler/testData/codegen/box/javaInterop/notNullAssertions/expressionAssertionMessages"), Pattern.compile("^(.+)\\.kt$"), null, TargetBackend.JVM_IR, true);
                 }
 
+                @Test
+                @TestMetadata("backingField.kt")
+                public void testBackingField() throws Exception {
+                    runTest("compiler/testData/codegen/box/javaInterop/notNullAssertions/expressionAssertionMessages/backingField.kt");
+                }
+
                 @Test
                 @TestMetadata("field_after.kt")
                 public void testField_after() throws Exception {

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

@@ -136,9 +136,12 @@ class JvmOptimizationLowering(val context: JvmBackendContext) : FileLoweringPass
                 } else {
                     +irGetField(receiver.takeUnless { backingField.isStatic }, backingField)
                 }
-            }
+            }.unwrapSingleExpressionBlock()
         }
 
+        private fun IrExpression.unwrapSingleExpressionBlock(): IrExpression =
+            (this as? IrBlock)?.statements?.singleOrNull() as? IrExpression ?: this
+
         override fun visitWhen(expression: IrWhen, data: IrDeclaration?): IrExpression {
             val isCompilerGenerated = expression.origin == null
             expression.transformChildren(this, data)

compiler/testData/codegen/box/javaInterop/notNullAssertions/expressionAssertionMessages/backingField.kt

@@ -0,0 +1,29 @@
+// !LANGUAGE: +NoSourceCodeInNotNullAssertionExceptions
+// TARGET_BACKEND: JVM
+// FILE: test.kt
+
+val publicProperty = J().s()
+private val privateProperty = J().s()
+
+fun f(x: String) = "Fail 1"
+
+fun box(): String {
+    try {
+        f(publicProperty)
+    } catch (e: NullPointerException) {
+        if (e.message != "publicProperty must not be null") return "Fail 2: ${e.message}"
+    }
+
+    try {
+        f(privateProperty)
+    } catch (e: NullPointerException) {
+        if (e.message != "privateProperty must not be null") return "Fail 3: ${e.message}"
+    }
+
+    return "OK"
+}
+
+// FILE: J.java
+public class J {
+    public final String s() { return null; }
+}

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

@@ -31045,6 +31045,12 @@ public class JvmAbiConsistencyTestBoxGenerated extends AbstractJvmAbiConsistency
                     KtTestUtil.assertAllTestsPresentByMetadataWithExcluded(this.getClass(), new File("compiler/testData/codegen/box/javaInterop/notNullAssertions/expressionAssertionMessages"), Pattern.compile("^(.+)\\.kt$"), null, TargetBackend.JVM_IR, true);
                 }
 
+                @Test
+                @TestMetadata("backingField.kt")
+                public void testBackingField() throws Exception {
+                    runTest("compiler/testData/codegen/box/javaInterop/notNullAssertions/expressionAssertionMessages/backingField.kt");
+                }
+
                 @Test
                 @TestMetadata("field_after.kt")
                 public void testField_after() throws Exception {

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

@@ -29323,6 +29323,12 @@ public class BlackBoxCodegenTestGenerated extends AbstractBlackBoxCodegenTest {
                     KtTestUtil.assertAllTestsPresentByMetadataWithExcluded(this.getClass(), new File("compiler/testData/codegen/box/javaInterop/notNullAssertions/expressionAssertionMessages"), Pattern.compile("^(.+)\\.kt$"), null, TargetBackend.JVM, true);
                 }
 
+                @Test
+                @TestMetadata("backingField.kt")
+                public void testBackingField() throws Exception {
+                    runTest("compiler/testData/codegen/box/javaInterop/notNullAssertions/expressionAssertionMessages/backingField.kt");
+                }
+
                 @Test
                 @TestMetadata("field_after.kt")
                 public void testField_after() throws Exception {

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

@@ -31045,6 +31045,12 @@ public class IrBlackBoxCodegenTestGenerated extends AbstractIrBlackBoxCodegenTes
                     KtTestUtil.assertAllTestsPresentByMetadataWithExcluded(this.getClass(), new File("compiler/testData/codegen/box/javaInterop/notNullAssertions/expressionAssertionMessages"), Pattern.compile("^(.+)\\.kt$"), null, TargetBackend.JVM_IR, true);
                 }
 
+                @Test
+                @TestMetadata("backingField.kt")
+                public void testBackingField() throws Exception {
+                    runTest("compiler/testData/codegen/box/javaInterop/notNullAssertions/expressionAssertionMessages/backingField.kt");
+                }
+
                 @Test
                 @TestMetadata("field_after.kt")
                 public void testField_after() throws Exception {

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

@@ -31045,6 +31045,12 @@ public class IrBlackBoxCodegenWithIrInlinerTestGenerated extends AbstractIrBlack
                     KtTestUtil.assertAllTestsPresentByMetadataWithExcluded(this.getClass(), new File("compiler/testData/codegen/box/javaInterop/notNullAssertions/expressionAssertionMessages"), Pattern.compile("^(.+)\\.kt$"), null, TargetBackend.JVM_IR, true);
                 }
 
+                @Test
+                @TestMetadata("backingField.kt")
+                public void testBackingField() throws Exception {
+                    runTest("compiler/testData/codegen/box/javaInterop/notNullAssertions/expressionAssertionMessages/backingField.kt");
+                }
+
                 @Test
                 @TestMetadata("field_after.kt")
                 public void testField_after() throws Exception {

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

@@ -26297,6 +26297,11 @@ public class LightAnalysisModeTestGenerated extends AbstractLightAnalysisModeTes
                     KtTestUtil.assertAllTestsPresentByMetadataWithExcluded(this.getClass(), new File("compiler/testData/codegen/box/javaInterop/notNullAssertions/expressionAssertionMessages"), Pattern.compile("^(.+)\\.kt$"), null, TargetBackend.JVM_IR, true);
                 }
 
+                @TestMetadata("backingField.kt")
+                public void testBackingField() throws Exception {
+                    runTest("compiler/testData/codegen/box/javaInterop/notNullAssertions/expressionAssertionMessages/backingField.kt");
+                }
+
                 @TestMetadata("field_after.kt")
                 public void testField_after() throws Exception {
                     runTest("compiler/testData/codegen/box/javaInterop/notNullAssertions/expressionAssertionMessages/field_after.kt");