Psi2ir: do not generate default accessor body for expect properties

Because generateDefaultGetterBody/generateDefaultSetterBody reference
the property's backing field, which in case of extension properties
leads to an error "Unbound symbols not allowed" because extension
property cannot have a backing field.

In some way, this check is similar to the `isExpect` check in
`generatePrimaryConstructor`.

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

@@ -24540,6 +24540,12 @@ public class FirBlackBoxCodegenTestGenerated extends AbstractFirBlackBoxCodegenT
             runTest("compiler/testData/codegen/box/multiplatform/expectClassInJvmMultifileFacade.kt");
         }
 
+        @Test
+        @TestMetadata("expectProperty.kt")
+        public void testExpectProperty() throws Exception {
+            runTest("compiler/testData/codegen/box/multiplatform/expectProperty.kt");
+        }
+
         @Test
         @TestMetadata("noArgActualConstructor.kt")
         public void testNoArgActualConstructor() throws Exception {

compiler/ir/ir.psi2ir/src/org/jetbrains/kotlin/psi2ir/generators/FunctionGenerator.kt

@@ -21,7 +21,6 @@ import org.jetbrains.kotlin.ir.expressions.impl.IrSetFieldImpl
 import org.jetbrains.kotlin.ir.types.impl.IrUninitializedType
 import org.jetbrains.kotlin.ir.util.declareSimpleFunctionWithOverrides
 import org.jetbrains.kotlin.name.Name
-import org.jetbrains.kotlin.name.Name.isValidIdentifier
 import org.jetbrains.kotlin.psi.*
 import org.jetbrains.kotlin.psi.psiUtil.pureEndOffset
 import org.jetbrains.kotlin.psi.psiUtil.pureStartOffset
@@ -137,8 +136,8 @@ class FunctionGenerator(declarationGenerator: DeclarationGenerator) : Declaratio
     private fun generateDefaultAccessorBody(
         accessor: PropertyAccessorDescriptor,
         irAccessor: IrSimpleFunction
-    ) =
-        if (accessor.modality == Modality.ABSTRACT)
+    ): IrBlockBody? =
+        if (accessor.modality == Modality.ABSTRACT || accessor.correspondingProperty.isExpect)
             null
         else
             when (accessor) {

compiler/testData/codegen/box/multiplatform/expectProperty.kt

@@ -0,0 +1,26 @@
+// !LANGUAGE: +MultiPlatformProjects
+// FILE: common.kt
+
+package test
+
+expect val v: String
+
+expect val Char.extensionVal: String
+
+expect var String.extensionVar: Char
+
+// FILE: jvm.kt
+
+package test
+
+actual val v: String = ""
+
+actual val Char.extensionVal: String
+    get() = toString()
+
+actual var String.extensionVar: Char
+    get() = this[0]
+    set(value) {}
+
+fun box(): String =
+    v + 'O'.extensionVal + "K".extensionVar

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

@@ -24540,6 +24540,12 @@ public class BlackBoxCodegenTestGenerated extends AbstractBlackBoxCodegenTest {
             runTest("compiler/testData/codegen/box/multiplatform/expectClassInJvmMultifileFacade.kt");
         }
 
+        @Test
+        @TestMetadata("expectProperty.kt")
+        public void testExpectProperty() throws Exception {
+            runTest("compiler/testData/codegen/box/multiplatform/expectProperty.kt");
+        }
+
         @Test
         @TestMetadata("noArgActualConstructor.kt")
         public void testNoArgActualConstructor() throws Exception {

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

@@ -24540,6 +24540,12 @@ public class IrBlackBoxCodegenTestGenerated extends AbstractIrBlackBoxCodegenTes
             runTest("compiler/testData/codegen/box/multiplatform/expectClassInJvmMultifileFacade.kt");
         }
 
+        @Test
+        @TestMetadata("expectProperty.kt")
+        public void testExpectProperty() throws Exception {
+            runTest("compiler/testData/codegen/box/multiplatform/expectProperty.kt");
+        }
+
         @Test
         @TestMetadata("noArgActualConstructor.kt")
         public void testNoArgActualConstructor() throws Exception {

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

@@ -20804,6 +20804,11 @@ public class LightAnalysisModeTestGenerated extends AbstractLightAnalysisModeTes
             runTest("compiler/testData/codegen/box/multiplatform/expectClassInJvmMultifileFacade.kt");
         }
 
+        @TestMetadata("expectProperty.kt")
+        public void testExpectProperty() throws Exception {
+            runTest("compiler/testData/codegen/box/multiplatform/expectProperty.kt");
+        }
+
         @TestMetadata("noArgActualConstructor.kt")
         public void testNoArgActualConstructor() throws Exception {
             runTest("compiler/testData/codegen/box/multiplatform/noArgActualConstructor.kt");