[FIR] Make SyntheticPropertySymbol derived from FirAccessorSymbol

compiler/fir/java/src/org/jetbrains/kotlin/fir/java/scopes/JavaClassEnhancementScope.kt

@@ -106,12 +106,12 @@ class JavaClassEnhancementScope(
                 return symbol
             }
             is FirSyntheticProperty -> {
-                original as FirAccessorSymbol
+                val accessorSymbol = firElement.symbol
                 val enhancedFunctionSymbol = enhanceMethod(
-                    firElement.getter.delegate, original.accessorId, original.accessorId.callableName
+                    firElement.getter.delegate, accessorSymbol.accessorId, accessorSymbol.accessorId.callableName
                 )
                 val enhancedProperty = FirSyntheticProperty(
-                    session, name, FirAccessorSymbol(original.callableId, original.accessorId),
+                    session, name, FirAccessorSymbol(accessorSymbol.callableId, accessorSymbol.accessorId),
                     enhancedFunctionSymbol.fir as FirSimpleFunction
                 )
                 return enhancedProperty.symbol

compiler/fir/java/src/org/jetbrains/kotlin/fir/java/scopes/JavaClassUseSiteMemberScope.kt

@@ -49,7 +49,7 @@ class JavaClassUseSiteMemberScope(
         syntheticPropertyName: Name,
         overrideCandidates: MutableSet<FirCallableSymbol<*>>,
         isGetter: Boolean
-    ): FirPropertySymbol? {
+    ): FirAccessorSymbol? {
         if (functionSymbol !is FirNamedFunctionSymbol) {
             return null
         }

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

@@ -10,7 +10,6 @@ import org.jetbrains.kotlin.fir.declarations.FirSimpleFunction
 import org.jetbrains.kotlin.fir.declarations.isStatic
 import org.jetbrains.kotlin.fir.declarations.synthetic.FirSyntheticProperty
 import org.jetbrains.kotlin.fir.scopes.FirScope
-import org.jetbrains.kotlin.fir.symbols.AccessorSymbol
 import org.jetbrains.kotlin.fir.symbols.CallableId
 import org.jetbrains.kotlin.fir.symbols.StandardClassIds
 import org.jetbrains.kotlin.fir.symbols.SyntheticSymbol
@@ -25,7 +24,7 @@ import org.jetbrains.kotlin.util.capitalizeDecapitalize.capitalizeFirstWord
 class SyntheticPropertySymbol(
     callableId: CallableId,
     override val accessorId: CallableId
-) : FirPropertySymbol(callableId), AccessorSymbol, SyntheticSymbol
+) : FirAccessorSymbol(callableId, accessorId), SyntheticSymbol
 
 class FirSyntheticFunctionSymbol(
     callableId: CallableId

compiler/fir/resolve/src/org/jetbrains/kotlin/fir/scopes/impl/FirClassSubstitutionScope.kt

@@ -68,9 +68,7 @@ class FirClassSubstitutionScope(
                     processor(field)
                 }
                 is FirAccessorSymbol -> {
-                    val accessor = fakeOverrideAccessors.getOrPut(original) {
+                    val accessor = fakeOverrideAccessors.getOrPut(original) { createFakeOverrideAccessor(original) }
-                        createFakeOverrideAccessor(original) as FirAccessorSymbol
-                    }
                     processor(accessor)
                 }
                 else -> {
@@ -197,7 +195,7 @@ class FirClassSubstitutionScope(
         return createFakeOverrideField(session, member, original, newReturnType)
     }
 
-    private fun createFakeOverrideAccessor(original: FirAccessorSymbol): FirPropertySymbol {
+    private fun createFakeOverrideAccessor(original: FirAccessorSymbol): FirAccessorSymbol {
         val member = original.fir as FirSyntheticProperty
 
         val returnType = typeCalculator.tryCalculateReturnType(member).type
@@ -330,7 +328,7 @@ class FirClassSubstitutionScope(
             baseSymbol: FirAccessorSymbol,
             newReturnType: ConeKotlinType? = null,
             newParameterTypes: List<ConeKotlinType?>? = null
-        ): FirPropertySymbol {
+        ): FirAccessorSymbol {
             val functionSymbol = FirNamedFunctionSymbol(baseSymbol.accessorId)
             val function = createFakeOverrideFunction(
                 functionSymbol, session, baseProperty.getter.delegate, null, newReturnType, newParameterTypes

compiler/fir/tree/src/org/jetbrains/kotlin/fir/declarations/synthetic/FirSyntheticProperty.kt

@@ -13,9 +13,9 @@ import org.jetbrains.kotlin.fir.expressions.FirAnnotationCall
 import org.jetbrains.kotlin.fir.expressions.FirExpression
 import org.jetbrains.kotlin.fir.references.FirControlFlowGraphReference
 import org.jetbrains.kotlin.fir.references.impl.FirEmptyControlFlowGraphReference
+import org.jetbrains.kotlin.fir.symbols.impl.FirAccessorSymbol
 import org.jetbrains.kotlin.fir.symbols.impl.FirBackingFieldSymbol
 import org.jetbrains.kotlin.fir.symbols.impl.FirDelegateFieldSymbol
-import org.jetbrains.kotlin.fir.symbols.impl.FirPropertySymbol
 import org.jetbrains.kotlin.fir.types.FirTypeRef
 import org.jetbrains.kotlin.fir.visitors.FirTransformer
 import org.jetbrains.kotlin.fir.visitors.FirVisitor
@@ -27,7 +27,7 @@ class FirSyntheticProperty(
     override val returnTypeRef: FirTypeRef,
     override val name: Name,
     override val isVar: Boolean,
-    override val symbol: FirPropertySymbol,
+    override val symbol: FirAccessorSymbol,
     override val status: FirDeclarationStatus,
     override val resolvePhase: FirResolvePhase,
     override val getter: FirSyntheticPropertyAccessor,
@@ -40,7 +40,7 @@ class FirSyntheticProperty(
     constructor(
         session: FirSession,
         name: Name,
-        symbol: FirPropertySymbol,
+        symbol: FirAccessorSymbol,
         delegateGetter: FirSimpleFunction
     ) : this(
         session, delegateGetter.returnTypeRef, name, false, symbol,

compiler/fir/tree/src/org/jetbrains/kotlin/fir/symbols/impl/FirFunctionSymbol.kt

@@ -33,7 +33,7 @@ class FirConstructorSymbol(
     override val overriddenSymbol: FirConstructorSymbol? = null
 ) : FirFunctionSymbol<FirConstructor>(callableId)
 
-class FirAccessorSymbol(
+open class FirAccessorSymbol(
     callableId: CallableId,
     override val accessorId: CallableId
 ) : FirPropertySymbol(callableId), AccessorSymbol