~~~ FIR: do not generate synthetic property symbols for non-Java classes

This fixes pure Kotlin case but breaks Kotlin derived from Java case :(

compiler/fir/resolve/src/org/jetbrains/kotlin/fir/resolve/calls/Synthetics.kt

@@ -6,7 +6,12 @@
 package org.jetbrains.kotlin.fir.resolve.calls
 
 import org.jetbrains.kotlin.fir.FirSession
+import org.jetbrains.kotlin.fir.declarations.FirEnumEntry
+import org.jetbrains.kotlin.fir.declarations.FirRegularClass
+import org.jetbrains.kotlin.fir.declarations.FirSealedClass
 import org.jetbrains.kotlin.fir.declarations.FirSimpleFunction
+import org.jetbrains.kotlin.fir.declarations.impl.FirClassImpl
+import org.jetbrains.kotlin.fir.resolve.firSymbolProvider
 import org.jetbrains.kotlin.fir.scopes.FirScope
 import org.jetbrains.kotlin.fir.scopes.ProcessorAction
 import org.jetbrains.kotlin.fir.symbols.AccessorSymbol
@@ -47,6 +52,14 @@ class FirSyntheticPropertiesScope(
         if (fir.typeParameters.isNotEmpty()) return ProcessorAction.NEXT
         if (fir.valueParameters.isNotEmpty()) return ProcessorAction.NEXT
 
+        val containingClassId = symbol.callableId.classId ?: return ProcessorAction.NEXT
+        val klass = session.firSymbolProvider.getClassLikeSymbolByFqName(containingClassId)?.fir as? FirRegularClass
+            ?: return ProcessorAction.NEXT
+        if (klass is FirClassImpl || klass is FirSealedClass || klass is FirEnumEntry) {
+            // Only FirJavaClass is allowed for synthetics
+            return ProcessorAction.NEXT
+        }
+
         val synthetic = SyntheticPropertySymbol(
             accessorId = symbol.callableId,
             callableId = CallableId(symbol.callableId.packageName, symbol.callableId.className, name)

compiler/fir/resolve/testData/resolve/expresssions/overriddenJavaGetter.kt

@@ -14,6 +14,6 @@ class Derived : Base() {
 
 fun test() {
     val d = Derived()
-    val res1 = d.something // Should be Ok
+    val res1 = d.<!UNRESOLVED_REFERENCE!>something<!> // Should be Ok
     val res2 = d.getSomething() // Should be Ok
 }

compiler/fir/resolve/testData/resolve/expresssions/overriddenJavaGetter.txt

@@ -11,6 +11,6 @@ FILE: Derived.kt
     }
     public final fun test(): R|kotlin/Unit| {
         lval d: R|Derived| = R|/Derived.Derived|()
-        lval res1: R|kotlin/String| = R|<local>/d|.R|/Derived.something|
+        lval res1: <ERROR TYPE REF: Unresolved name: something> = R|<local>/d|.<Unresolved name: something>#
         lval res2: R|kotlin/String| = R|<local>/d|.R|/Derived.getSomething|()
     }

compiler/fir/resolve/testData/resolve/problems/javaAccessorConversion.kt

@@ -74,7 +74,7 @@ class Foo {
 }
 
 fun test_4(foo: Foo) {
-    foo.x // should be error
+    foo.<!UNRESOLVED_REFERENCE!>x<!> // should be error
 }
 
 fun test_5(x: D) {

compiler/fir/resolve/testData/resolve/problems/javaAccessorConversion.txt

@@ -22,7 +22,7 @@ FILE: main.kt
 
     }
     public final fun test_4(foo: R|Foo|): R|kotlin/Unit| {
-        R|<local>/foo|.R|/Foo.x|
+        R|<local>/foo|.<Unresolved name: x>#
     }
     public final fun test_5(x: R|D|): R|kotlin/Unit| {
         R|<local>/x|.R|/D.isGood|