diff --git a/compiler/fir/resolve/src/org/jetbrains/kotlin/fir/resolve/FirQualifierResolver.kt b/compiler/fir/resolve/src/org/jetbrains/kotlin/fir/resolve/FirQualifierResolver.kt
index b2f99870133..d0f970a6400 100644
--- a/compiler/fir/resolve/src/org/jetbrains/kotlin/fir/resolve/FirQualifierResolver.kt
+++ b/compiler/fir/resolve/src/org/jetbrains/kotlin/fir/resolve/FirQualifierResolver.kt
@@ -10,7 +10,7 @@ import org.jetbrains.kotlin.fir.symbols.impl.FirClassifierSymbol
 import org.jetbrains.kotlin.fir.types.FirQualifierPart
 import org.jetbrains.kotlin.name.ClassId
 
-interface FirQualifierResolver : FirSessionComponent {
-    fun resolveSymbolWithPrefix(parts: List<FirQualifierPart>, prefix: ClassId): FirClassifierSymbol<*>?
-    fun resolveSymbol(parts: List<FirQualifierPart>): FirClassifierSymbol<*>?
+abstract class FirQualifierResolver : FirSessionComponent {
+    abstract fun resolveSymbolWithPrefix(parts: List<FirQualifierPart>, prefix: ClassId): FirClassifierSymbol<*>?
+    abstract fun resolveSymbol(parts: List<FirQualifierPart>): FirClassifierSymbol<*>?
 }
diff --git a/compiler/fir/resolve/src/org/jetbrains/kotlin/fir/resolve/FirTypeResolver.kt b/compiler/fir/resolve/src/org/jetbrains/kotlin/fir/resolve/FirTypeResolver.kt
index dfa9af7ab94..60f5054d3d2 100644
--- a/compiler/fir/resolve/src/org/jetbrains/kotlin/fir/resolve/FirTypeResolver.kt
+++ b/compiler/fir/resolve/src/org/jetbrains/kotlin/fir/resolve/FirTypeResolver.kt
@@ -6,12 +6,10 @@
 package org.jetbrains.kotlin.fir.resolve
 
 import org.jetbrains.kotlin.fir.FirSessionComponent
-import org.jetbrains.kotlin.fir.resolve.substitution.ConeSubstitutor
 import org.jetbrains.kotlin.fir.scopes.FirScope
-import org.jetbrains.kotlin.fir.symbols.impl.FirClassifierSymbol
 import org.jetbrains.kotlin.fir.types.ConeKotlinType
 import org.jetbrains.kotlin.fir.types.FirTypeRef
 
-interface FirTypeResolver : FirSessionComponent {
-    fun resolveType(typeRef: FirTypeRef, scope: FirScope, areBareTypesAllowed: Boolean): ConeKotlinType
+abstract class FirTypeResolver : FirSessionComponent {
+    abstract fun resolveType(typeRef: FirTypeRef, scope: FirScope, areBareTypesAllowed: Boolean): ConeKotlinType
 }
diff --git a/compiler/fir/resolve/src/org/jetbrains/kotlin/fir/resolve/providers/impl/FirQualifierResolverImpl.kt b/compiler/fir/resolve/src/org/jetbrains/kotlin/fir/resolve/providers/impl/FirQualifierResolverImpl.kt
index cddc21ab77d..97371be5e00 100644
--- a/compiler/fir/resolve/src/org/jetbrains/kotlin/fir/resolve/providers/impl/FirQualifierResolverImpl.kt
+++ b/compiler/fir/resolve/src/org/jetbrains/kotlin/fir/resolve/providers/impl/FirQualifierResolverImpl.kt
@@ -13,7 +13,7 @@ import org.jetbrains.kotlin.fir.types.FirQualifierPart
 import org.jetbrains.kotlin.name.ClassId
 import org.jetbrains.kotlin.name.FqName
 
-class FirQualifierResolverImpl(val session: FirSession) : FirQualifierResolver {
+class FirQualifierResolverImpl(val session: FirSession) : FirQualifierResolver() {
 
     override fun resolveSymbolWithPrefix(parts: List<FirQualifierPart>, prefix: ClassId): FirClassifierSymbol<*>? {
         val symbolProvider = session.firSymbolProvider
diff --git a/compiler/fir/resolve/src/org/jetbrains/kotlin/fir/resolve/providers/impl/FirTypeResolverImpl.kt b/compiler/fir/resolve/src/org/jetbrains/kotlin/fir/resolve/providers/impl/FirTypeResolverImpl.kt
index 0a220ec30d9..ff4a1571c4c 100644
--- a/compiler/fir/resolve/src/org/jetbrains/kotlin/fir/resolve/providers/impl/FirTypeResolverImpl.kt
+++ b/compiler/fir/resolve/src/org/jetbrains/kotlin/fir/resolve/providers/impl/FirTypeResolverImpl.kt
@@ -26,7 +26,7 @@ import org.jetbrains.kotlin.fir.types.impl.ConeTypeParameterTypeImpl
 import org.jetbrains.kotlin.fir.types.impl.FirImplicitBuiltinTypeRef
 import org.jetbrains.kotlin.name.ClassId
 
-class FirTypeResolverImpl(private val session: FirSession) : FirTypeResolver {
+class FirTypeResolverImpl(private val session: FirSession) : FirTypeResolver() {
 
     private val symbolProvider by lazy {
         session.firSymbolProvider