diff --git a/compiler/fir/fir2ir/src/org/jetbrains/kotlin/fir/backend/generators/DelegatedMemberGenerator.kt b/compiler/fir/fir2ir/src/org/jetbrains/kotlin/fir/backend/generators/DelegatedMemberGenerator.kt
index 550909136b8..16e65d121e8 100644
--- a/compiler/fir/fir2ir/src/org/jetbrains/kotlin/fir/backend/generators/DelegatedMemberGenerator.kt
+++ b/compiler/fir/fir2ir/src/org/jetbrains/kotlin/fir/backend/generators/DelegatedMemberGenerator.kt
@@ -25,21 +25,24 @@ import org.jetbrains.kotlin.fir.symbols.impl.FirVariableSymbol
 import org.jetbrains.kotlin.ir.declarations.*
 import org.jetbrains.kotlin.ir.declarations.impl.IrFunctionImpl
 import org.jetbrains.kotlin.ir.declarations.impl.IrPropertyImpl
+import org.jetbrains.kotlin.ir.declarations.impl.IrTypeParameterImpl
 import org.jetbrains.kotlin.ir.declarations.impl.IrValueParameterImpl
 import org.jetbrains.kotlin.ir.descriptors.WrappedPropertyDescriptor
 import org.jetbrains.kotlin.ir.descriptors.WrappedSimpleFunctionDescriptor
+import org.jetbrains.kotlin.ir.descriptors.WrappedTypeParameterDescriptor
 import org.jetbrains.kotlin.ir.descriptors.WrappedValueParameterDescriptor
 import org.jetbrains.kotlin.ir.expressions.impl.*
-import org.jetbrains.kotlin.ir.types.classOrNull
+import org.jetbrains.kotlin.ir.symbols.IrTypeParameterSymbol
+import org.jetbrains.kotlin.ir.types.*
 import org.jetbrains.kotlin.ir.types.impl.IrSimpleTypeImpl
-import org.jetbrains.kotlin.ir.types.isNothing
-import org.jetbrains.kotlin.ir.types.isUnit
+import org.jetbrains.kotlin.ir.types.impl.makeTypeProjection
 import org.jetbrains.kotlin.ir.util.classId
 import org.jetbrains.kotlin.ir.util.defaultType
 import org.jetbrains.kotlin.ir.util.hasAnnotation
 import org.jetbrains.kotlin.ir.util.isFakeOverride
 import org.jetbrains.kotlin.name.FqName
 import org.jetbrains.kotlin.name.Name
+import org.jetbrains.kotlin.types.Variance
 
 /**
  * A generator for delegated members from implementation by delegation.
@@ -105,6 +108,12 @@ internal class DelegatedMemberGenerator(
         val descriptor = WrappedSimpleFunctionDescriptor()
         val origin = IrDeclarationOrigin.DELEGATED_MEMBER
         val modality = if (superFunction.modality == Modality.ABSTRACT) Modality.OPEN else superFunction.modality
+        // TODO: external classes, as the type parameters are converted using deserialized descriptors when used inside the classes.
+        val addTypeSubstitution = irField.type.classOrNull?.owner?.origin?.let {
+            it != IrDeclarationOrigin.IR_EXTERNAL_DECLARATION_STUB
+                    && it != IrDeclarationOrigin.IR_EXTERNAL_JAVA_DECLARATION_STUB
+        } == true
+        lateinit var irTypeSubstitutor: IrTypeSubstitutor
         val delegateFunction = symbolTable.declareSimpleFunction(descriptor) { symbol ->
             IrFunctionImpl(
                 startOffset,
@@ -127,15 +136,48 @@ internal class DelegatedMemberGenerator(
                 this.parent = subClass
                 overriddenSymbols = listOf(superFunction.symbol)
                 dispatchReceiverParameter = declareThisReceiverParameter(symbolTable, subClass.defaultType, origin)
-                // TODO: type parameters from superFunctions and type substitution when super interface types are generic
+                if (addTypeSubstitution) {
+                    val substParameters = mutableListOf<IrTypeParameterSymbol>()
+                    val substArguments = mutableListOf<IrTypeArgument>()
+                    initializeTypeSubstitution(substParameters, substArguments, irField.type)
+                    superFunction.typeParameters.forEach { typeParameter ->
+                        val parameterDescriptor = WrappedTypeParameterDescriptor()
+                        typeParameters += symbolTable.declareScopedTypeParameter(
+                            startOffset, endOffset, origin, parameterDescriptor
+                        ) { symbol ->
+                            IrTypeParameterImpl(
+                                startOffset,
+                                endOffset,
+                                origin,
+                                symbol,
+                                typeParameter.name,
+                                typeParameter.index,
+                                typeParameter.isReified,
+                                typeParameter.variance
+                            ).also {
+                                parameterDescriptor.bind(it)
+                                it.parent = this
+                                substParameters.add(typeParameter.symbol)
+                                substArguments.add(
+                                    makeTypeProjection(
+                                        variance = Variance.INVARIANT,
+                                        type = IrSimpleTypeImpl(it.symbol, false, emptyList(), emptyList())
+                                    )
+                                )
+                            }
+                        }
+                    }
+                    irTypeSubstitutor = IrTypeSubstitutor(substParameters, substArguments, irBuiltIns)
+                }
                 superFunction.valueParameters.forEach { valueParameter ->
                     val parameterDescriptor = WrappedValueParameterDescriptor()
+                    val substedType = if (addTypeSubstitution) irTypeSubstitutor.substitute(valueParameter.type) else valueParameter.type
                     valueParameters += symbolTable.declareValueParameter(
-                        startOffset, endOffset, origin, parameterDescriptor, valueParameter.type
+                        startOffset, endOffset, origin, parameterDescriptor, substedType
                     ) { symbol ->
                         IrValueParameterImpl(
                             startOffset, endOffset, origin, symbol,
-                            valueParameter.name, valueParameter.index, valueParameter.type,
+                            valueParameter.name, valueParameter.index, substedType,
                             null, valueParameter.isCrossinline, valueParameter.isNoinline
                         ).also {
                             parameterDescriptor.bind(it)
@@ -177,7 +219,7 @@ internal class DelegatedMemberGenerator(
         val irCall = IrCallImpl(
             startOffset,
             endOffset,
-            superFunction.returnType,
+            if (addTypeSubstitution) irTypeSubstitutor.substitute(superFunction.returnType) else superFunction.returnType,
             superFunction.symbol,
             superFunction.typeParameters.size,
             superFunction.valueParameters.size
@@ -211,6 +253,20 @@ internal class DelegatedMemberGenerator(
         return delegateFunction
     }
 
+    private fun initializeTypeSubstitution(
+        typeParameters: MutableList<IrTypeParameterSymbol>,
+        typeArguments: MutableList<IrTypeArgument>,
+        type: IrType
+    ) {
+        if (type is IrSimpleTypeImpl && type.arguments.isNotEmpty()) {
+            val classTypeParameters = type.classOrNull?.owner?.typeParameters
+            if (classTypeParameters?.size == type.arguments.size) {
+                typeParameters.addAll(classTypeParameters.map { it.symbol })
+                typeArguments.addAll(type.arguments)
+            }
+        }
+    }
+
     private fun generateDelegatedProperty(
         subClass: IrClass,
         irField: IrField,
diff --git a/compiler/testData/codegen/box/classes/delegationGenericArg.kt b/compiler/testData/codegen/box/classes/delegationGenericArg.kt
index 86ab6a11cc7..f298e834f79 100644
--- a/compiler/testData/codegen/box/classes/delegationGenericArg.kt
+++ b/compiler/testData/codegen/box/classes/delegationGenericArg.kt
@@ -1,4 +1,3 @@
-// IGNORE_BACKEND_FIR: JVM_IR
 interface A<T> {
     fun foo(t: T): String
 }
diff --git a/compiler/testData/codegen/box/classes/delegationGenericArgUpperBound.kt b/compiler/testData/codegen/box/classes/delegationGenericArgUpperBound.kt
index 577edda2528..72e541b7f3b 100644
--- a/compiler/testData/codegen/box/classes/delegationGenericArgUpperBound.kt
+++ b/compiler/testData/codegen/box/classes/delegationGenericArgUpperBound.kt
@@ -1,4 +1,3 @@
-// IGNORE_BACKEND_FIR: JVM_IR
 interface A<T: Number> {
     fun foo(t: T): String
 }
diff --git a/compiler/testData/codegen/box/classes/delegationGenericLongArg.kt b/compiler/testData/codegen/box/classes/delegationGenericLongArg.kt
index 9ea8e639590..8bd117f9fa1 100644
--- a/compiler/testData/codegen/box/classes/delegationGenericLongArg.kt
+++ b/compiler/testData/codegen/box/classes/delegationGenericLongArg.kt
@@ -1,4 +1,3 @@
-// IGNORE_BACKEND_FIR: JVM_IR
 interface A<T, U> {
     fun foo(t: T, u: U): String
 }
diff --git a/compiler/testData/ir/irText/classes/delegatedGenericImplementation.fir.txt b/compiler/testData/ir/irText/classes/delegatedGenericImplementation.fir.txt
index a8d21428d01..007a5c5ca47 100644
--- a/compiler/testData/ir/irText/classes/delegatedGenericImplementation.fir.txt
+++ b/compiler/testData/ir/irText/classes/delegatedGenericImplementation.fir.txt
@@ -49,55 +49,59 @@ FILE fqName:<root> fileName:/delegatedGenericImplementation.kt
         SET_FIELD 'FIELD DELEGATE name:$$delegate_0 type:<root>.IBase<E of <root>.Test1> visibility:local [final]' type=kotlin.Unit origin=EQ
           receiver: GET_VAR '<this>: <root>.Test1<E of <root>.Test1> declared in <root>.Test1' type=<root>.Test1<E of <root>.Test1> origin=null
           value: GET_VAR 'i: <root>.IBase<E of <root>.Test1> declared in <root>.Test1.<init>' type=<root>.IBase<E of <root>.Test1> origin=null
-    FUN DELEGATED_MEMBER name:foo visibility:public modality:OPEN <> ($this:<root>.Test1<E of <root>.Test1>, a:A of <root>.IBase, b:B of <root>.IBase.foo) returnType:kotlin.Unit
+    FUN DELEGATED_MEMBER name:foo visibility:public modality:OPEN <B> ($this:<root>.Test1<E of <root>.Test1>, a:E of <root>.Test1, b:B of <root>.Test1.foo) returnType:kotlin.Unit
       overridden:
         public abstract fun foo <B> (a: A of <root>.IBase, b: B of <root>.IBase.foo): kotlin.Unit declared in <root>.IBase
+      TYPE_PARAMETER DELEGATED_MEMBER name:B index:0 variance: superTypes:[]
       $this: VALUE_PARAMETER DELEGATED_MEMBER name:<this> type:<root>.Test1<E of <root>.Test1>
-      VALUE_PARAMETER DELEGATED_MEMBER name:a index:0 type:A of <root>.IBase
-      VALUE_PARAMETER DELEGATED_MEMBER name:b index:1 type:B of <root>.IBase.foo
+      VALUE_PARAMETER DELEGATED_MEMBER name:a index:0 type:E of <root>.Test1
+      VALUE_PARAMETER DELEGATED_MEMBER name:b index:1 type:B of <root>.Test1.foo
       BLOCK_BODY
         CALL 'public abstract fun foo <B> (a: A of <root>.IBase, b: B of <root>.IBase.foo): kotlin.Unit declared in <root>.IBase' type=kotlin.Unit origin=null
           <B>: <none>
           $this: GET_FIELD 'FIELD DELEGATE name:$$delegate_0 type:<root>.IBase<E of <root>.Test1> visibility:local [final]' type=<root>.IBase<E of <root>.Test1> origin=null
             receiver: GET_VAR '<this>: <root>.Test1<E of <root>.Test1> declared in <root>.Test1.foo' type=<root>.Test1<E of <root>.Test1> origin=null
-          a: GET_VAR 'a: A of <root>.IBase declared in <root>.Test1.foo' type=A of <root>.IBase origin=null
-          b: GET_VAR 'b: B of <root>.IBase.foo declared in <root>.Test1.foo' type=B of <root>.IBase.foo origin=null
+          a: GET_VAR 'a: E of <root>.Test1 declared in <root>.Test1.foo' type=E of <root>.Test1 origin=null
+          b: GET_VAR 'b: B of <root>.Test1.foo declared in <root>.Test1.foo' type=B of <root>.Test1.foo origin=null
     PROPERTY DELEGATED_MEMBER name:id visibility:public modality:OPEN [val]
-      FUN DELEGATED_MEMBER name:<get-id> visibility:public modality:OPEN <> ($this:<root>.Test1<E of <root>.Test1>) returnType:kotlin.collections.Map<A of <root>.IBase, C of <root>.IBase.<get-id>>?
+      FUN DELEGATED_MEMBER name:<get-id> visibility:public modality:OPEN <C> ($this:<root>.Test1<E of <root>.Test1>) returnType:kotlin.collections.Map<A of <root>.IBase, C of <root>.IBase.<get-id>>?
         correspondingProperty: PROPERTY DELEGATED_MEMBER name:id visibility:public modality:OPEN [val]
         overridden:
           public abstract fun <get-id> <C> (): kotlin.collections.Map<A of <root>.IBase, C of <root>.IBase.<get-id>>? declared in <root>.IBase
+        TYPE_PARAMETER DELEGATED_MEMBER name:C index:0 variance: superTypes:[]
         $this: VALUE_PARAMETER DELEGATED_MEMBER name:<this> type:<root>.Test1<E of <root>.Test1>
         BLOCK_BODY
-          RETURN type=kotlin.Nothing from='public open fun <get-id> (): kotlin.collections.Map<A of <root>.IBase, C of <root>.IBase.<get-id>>? declared in <root>.Test1'
-            CALL 'public abstract fun <get-id> <C> (): kotlin.collections.Map<A of <root>.IBase, C of <root>.IBase.<get-id>>? declared in <root>.IBase' type=kotlin.collections.Map<A of <root>.IBase, C of <root>.IBase.<get-id>>? origin=null
+          RETURN type=kotlin.Nothing from='public open fun <get-id> <C> (): kotlin.collections.Map<A of <root>.IBase, C of <root>.IBase.<get-id>>? declared in <root>.Test1'
+            CALL 'public abstract fun <get-id> <C> (): kotlin.collections.Map<A of <root>.IBase, C of <root>.IBase.<get-id>>? declared in <root>.IBase' type=kotlin.collections.Map<E of <root>.Test1, C of <root>.Test1.<get-id>>? origin=null
               <C>: <none>
               $this: GET_FIELD 'FIELD DELEGATE name:$$delegate_0 type:<root>.IBase<E of <root>.Test1> visibility:local [final]' type=<root>.IBase<E of <root>.Test1> origin=null
                 receiver: GET_VAR '<this>: <root>.Test1<E of <root>.Test1> declared in <root>.Test1.<get-id>' type=<root>.Test1<E of <root>.Test1> origin=null
     PROPERTY DELEGATED_MEMBER name:x visibility:public modality:OPEN [var]
-      FUN DELEGATED_MEMBER name:<get-x> visibility:public modality:OPEN <> ($this:<root>.Test1<E of <root>.Test1>) returnType:D of <root>.IBase.<get-x>?
+      FUN DELEGATED_MEMBER name:<get-x> visibility:public modality:OPEN <D> ($this:<root>.Test1<E of <root>.Test1>) returnType:D of <root>.IBase.<get-x>?
         correspondingProperty: PROPERTY DELEGATED_MEMBER name:x visibility:public modality:OPEN [var]
         overridden:
           public abstract fun <get-x> <D> (): D of <root>.IBase.<get-x>? declared in <root>.IBase
+        TYPE_PARAMETER DELEGATED_MEMBER name:D index:0 variance: superTypes:[]
         $this: VALUE_PARAMETER DELEGATED_MEMBER name:<this> type:<root>.Test1<E of <root>.Test1>
         BLOCK_BODY
-          RETURN type=kotlin.Nothing from='public open fun <get-x> (): D of <root>.IBase.<get-x>? declared in <root>.Test1'
-            CALL 'public abstract fun <get-x> <D> (): D of <root>.IBase.<get-x>? declared in <root>.IBase' type=D of <root>.IBase.<get-x>? origin=null
+          RETURN type=kotlin.Nothing from='public open fun <get-x> <D> (): D of <root>.IBase.<get-x>? declared in <root>.Test1'
+            CALL 'public abstract fun <get-x> <D> (): D of <root>.IBase.<get-x>? declared in <root>.IBase' type=D of <root>.Test1.<get-x>? origin=null
               <D>: <none>
               $this: GET_FIELD 'FIELD DELEGATE name:$$delegate_0 type:<root>.IBase<E of <root>.Test1> visibility:local [final]' type=<root>.IBase<E of <root>.Test1> origin=null
                 receiver: GET_VAR '<this>: <root>.Test1<E of <root>.Test1> declared in <root>.Test1.<get-x>' type=<root>.Test1<E of <root>.Test1> origin=null
-      FUN DELEGATED_MEMBER name:<set-x> visibility:public modality:OPEN <> ($this:<root>.Test1<E of <root>.Test1>, <set-?>:D of <root>.IBase.<set-x>?) returnType:kotlin.Unit
+      FUN DELEGATED_MEMBER name:<set-x> visibility:public modality:OPEN <D> ($this:<root>.Test1<E of <root>.Test1>, <set-?>:D of <root>.Test1.<set-x>?) returnType:kotlin.Unit
         correspondingProperty: PROPERTY DELEGATED_MEMBER name:x visibility:public modality:OPEN [var]
         overridden:
           public abstract fun <set-x> <D> (<set-?>: D of <root>.IBase.<set-x>?): kotlin.Unit declared in <root>.IBase
+        TYPE_PARAMETER DELEGATED_MEMBER name:D index:0 variance: superTypes:[]
         $this: VALUE_PARAMETER DELEGATED_MEMBER name:<this> type:<root>.Test1<E of <root>.Test1>
-        VALUE_PARAMETER DELEGATED_MEMBER name:<set-?> index:0 type:D of <root>.IBase.<set-x>?
+        VALUE_PARAMETER DELEGATED_MEMBER name:<set-?> index:0 type:D of <root>.Test1.<set-x>?
         BLOCK_BODY
           CALL 'public abstract fun <set-x> <D> (<set-?>: D of <root>.IBase.<set-x>?): kotlin.Unit declared in <root>.IBase' type=kotlin.Unit origin=null
             <D>: <none>
             $this: GET_FIELD 'FIELD DELEGATE name:$$delegate_0 type:<root>.IBase<E of <root>.Test1> visibility:local [final]' type=<root>.IBase<E of <root>.Test1> origin=null
               receiver: GET_VAR '<this>: <root>.Test1<E of <root>.Test1> declared in <root>.Test1.<set-x>' type=<root>.Test1<E of <root>.Test1> origin=null
-            <set-?>: GET_VAR '<set-?>: D of <root>.IBase.<set-x>? declared in <root>.Test1.<set-x>' type=D of <root>.IBase.<set-x>? origin=null
+            <set-?>: GET_VAR '<set-?>: D of <root>.Test1.<set-x>? declared in <root>.Test1.<set-x>' type=D of <root>.Test1.<set-x>? origin=null
     FIELD DELEGATE name:$$delegate_0 type:<root>.IBase<E of <root>.Test1> visibility:local [final]
     FUN FAKE_OVERRIDE name:equals visibility:public modality:OPEN <> ($this:kotlin.Any, other:kotlin.Any?) returnType:kotlin.Boolean [fake_override,operator]
       overridden:
@@ -141,55 +145,59 @@ FILE fqName:<root> fileName:/delegatedGenericImplementation.kt
           SET_FIELD 'FIELD PROPERTY_BACKING_FIELD name:j type:<root>.IBase<kotlin.String> visibility:private' type=kotlin.Unit origin=null
             receiver: GET_VAR '<this>: <root>.Test2 declared in <root>.Test2.<set-j>' type=<root>.Test2 origin=null
             value: GET_VAR '<set-?>: <root>.IBase<kotlin.String> declared in <root>.Test2.<set-j>' type=<root>.IBase<kotlin.String> origin=null
-    FUN DELEGATED_MEMBER name:foo visibility:public modality:OPEN <> ($this:<root>.Test2, a:A of <root>.IBase, b:B of <root>.IBase.foo) returnType:kotlin.Unit
+    FUN DELEGATED_MEMBER name:foo visibility:public modality:OPEN <B> ($this:<root>.Test2, a:kotlin.String, b:B of <root>.Test2.foo) returnType:kotlin.Unit
       overridden:
         public abstract fun foo <B> (a: A of <root>.IBase, b: B of <root>.IBase.foo): kotlin.Unit declared in <root>.IBase
+      TYPE_PARAMETER DELEGATED_MEMBER name:B index:0 variance: superTypes:[]
       $this: VALUE_PARAMETER DELEGATED_MEMBER name:<this> type:<root>.Test2
-      VALUE_PARAMETER DELEGATED_MEMBER name:a index:0 type:A of <root>.IBase
-      VALUE_PARAMETER DELEGATED_MEMBER name:b index:1 type:B of <root>.IBase.foo
+      VALUE_PARAMETER DELEGATED_MEMBER name:a index:0 type:kotlin.String
+      VALUE_PARAMETER DELEGATED_MEMBER name:b index:1 type:B of <root>.Test2.foo
       BLOCK_BODY
         CALL 'public abstract fun foo <B> (a: A of <root>.IBase, b: B of <root>.IBase.foo): kotlin.Unit declared in <root>.IBase' type=kotlin.Unit origin=null
           <B>: <none>
           $this: GET_FIELD 'FIELD DELEGATE name:$$delegate_0 type:<root>.IBase<kotlin.String> visibility:local [final]' type=<root>.IBase<kotlin.String> origin=null
             receiver: GET_VAR '<this>: <root>.Test2 declared in <root>.Test2.foo' type=<root>.Test2 origin=null
-          a: GET_VAR 'a: A of <root>.IBase declared in <root>.Test2.foo' type=A of <root>.IBase origin=null
-          b: GET_VAR 'b: B of <root>.IBase.foo declared in <root>.Test2.foo' type=B of <root>.IBase.foo origin=null
+          a: GET_VAR 'a: kotlin.String declared in <root>.Test2.foo' type=kotlin.String origin=null
+          b: GET_VAR 'b: B of <root>.Test2.foo declared in <root>.Test2.foo' type=B of <root>.Test2.foo origin=null
     PROPERTY DELEGATED_MEMBER name:id visibility:public modality:OPEN [val]
-      FUN DELEGATED_MEMBER name:<get-id> visibility:public modality:OPEN <> ($this:<root>.Test2) returnType:kotlin.collections.Map<A of <root>.IBase, C of <root>.IBase.<get-id>>?
+      FUN DELEGATED_MEMBER name:<get-id> visibility:public modality:OPEN <C> ($this:<root>.Test2) returnType:kotlin.collections.Map<A of <root>.IBase, C of <root>.IBase.<get-id>>?
         correspondingProperty: PROPERTY DELEGATED_MEMBER name:id visibility:public modality:OPEN [val]
         overridden:
           public abstract fun <get-id> <C> (): kotlin.collections.Map<A of <root>.IBase, C of <root>.IBase.<get-id>>? declared in <root>.IBase
+        TYPE_PARAMETER DELEGATED_MEMBER name:C index:0 variance: superTypes:[]
         $this: VALUE_PARAMETER DELEGATED_MEMBER name:<this> type:<root>.Test2
         BLOCK_BODY
-          RETURN type=kotlin.Nothing from='public open fun <get-id> (): kotlin.collections.Map<A of <root>.IBase, C of <root>.IBase.<get-id>>? declared in <root>.Test2'
-            CALL 'public abstract fun <get-id> <C> (): kotlin.collections.Map<A of <root>.IBase, C of <root>.IBase.<get-id>>? declared in <root>.IBase' type=kotlin.collections.Map<A of <root>.IBase, C of <root>.IBase.<get-id>>? origin=null
+          RETURN type=kotlin.Nothing from='public open fun <get-id> <C> (): kotlin.collections.Map<A of <root>.IBase, C of <root>.IBase.<get-id>>? declared in <root>.Test2'
+            CALL 'public abstract fun <get-id> <C> (): kotlin.collections.Map<A of <root>.IBase, C of <root>.IBase.<get-id>>? declared in <root>.IBase' type=kotlin.collections.Map<kotlin.String, C of <root>.Test2.<get-id>>? origin=null
               <C>: <none>
               $this: GET_FIELD 'FIELD DELEGATE name:$$delegate_0 type:<root>.IBase<kotlin.String> visibility:local [final]' type=<root>.IBase<kotlin.String> origin=null
                 receiver: GET_VAR '<this>: <root>.Test2 declared in <root>.Test2.<get-id>' type=<root>.Test2 origin=null
     PROPERTY DELEGATED_MEMBER name:x visibility:public modality:OPEN [var]
-      FUN DELEGATED_MEMBER name:<get-x> visibility:public modality:OPEN <> ($this:<root>.Test2) returnType:D of <root>.IBase.<get-x>?
+      FUN DELEGATED_MEMBER name:<get-x> visibility:public modality:OPEN <D> ($this:<root>.Test2) returnType:D of <root>.IBase.<get-x>?
         correspondingProperty: PROPERTY DELEGATED_MEMBER name:x visibility:public modality:OPEN [var]
         overridden:
           public abstract fun <get-x> <D> (): D of <root>.IBase.<get-x>? declared in <root>.IBase
+        TYPE_PARAMETER DELEGATED_MEMBER name:D index:0 variance: superTypes:[]
         $this: VALUE_PARAMETER DELEGATED_MEMBER name:<this> type:<root>.Test2
         BLOCK_BODY
-          RETURN type=kotlin.Nothing from='public open fun <get-x> (): D of <root>.IBase.<get-x>? declared in <root>.Test2'
-            CALL 'public abstract fun <get-x> <D> (): D of <root>.IBase.<get-x>? declared in <root>.IBase' type=D of <root>.IBase.<get-x>? origin=null
+          RETURN type=kotlin.Nothing from='public open fun <get-x> <D> (): D of <root>.IBase.<get-x>? declared in <root>.Test2'
+            CALL 'public abstract fun <get-x> <D> (): D of <root>.IBase.<get-x>? declared in <root>.IBase' type=D of <root>.Test2.<get-x>? origin=null
               <D>: <none>
               $this: GET_FIELD 'FIELD DELEGATE name:$$delegate_0 type:<root>.IBase<kotlin.String> visibility:local [final]' type=<root>.IBase<kotlin.String> origin=null
                 receiver: GET_VAR '<this>: <root>.Test2 declared in <root>.Test2.<get-x>' type=<root>.Test2 origin=null
-      FUN DELEGATED_MEMBER name:<set-x> visibility:public modality:OPEN <> ($this:<root>.Test2, <set-?>:D of <root>.IBase.<set-x>?) returnType:kotlin.Unit
+      FUN DELEGATED_MEMBER name:<set-x> visibility:public modality:OPEN <D> ($this:<root>.Test2, <set-?>:D of <root>.Test2.<set-x>?) returnType:kotlin.Unit
         correspondingProperty: PROPERTY DELEGATED_MEMBER name:x visibility:public modality:OPEN [var]
         overridden:
           public abstract fun <set-x> <D> (<set-?>: D of <root>.IBase.<set-x>?): kotlin.Unit declared in <root>.IBase
+        TYPE_PARAMETER DELEGATED_MEMBER name:D index:0 variance: superTypes:[]
         $this: VALUE_PARAMETER DELEGATED_MEMBER name:<this> type:<root>.Test2
-        VALUE_PARAMETER DELEGATED_MEMBER name:<set-?> index:0 type:D of <root>.IBase.<set-x>?
+        VALUE_PARAMETER DELEGATED_MEMBER name:<set-?> index:0 type:D of <root>.Test2.<set-x>?
         BLOCK_BODY
           CALL 'public abstract fun <set-x> <D> (<set-?>: D of <root>.IBase.<set-x>?): kotlin.Unit declared in <root>.IBase' type=kotlin.Unit origin=null
             <D>: <none>
             $this: GET_FIELD 'FIELD DELEGATE name:$$delegate_0 type:<root>.IBase<kotlin.String> visibility:local [final]' type=<root>.IBase<kotlin.String> origin=null
               receiver: GET_VAR '<this>: <root>.Test2 declared in <root>.Test2.<set-x>' type=<root>.Test2 origin=null
-            <set-?>: GET_VAR '<set-?>: D of <root>.IBase.<set-x>? declared in <root>.Test2.<set-x>' type=D of <root>.IBase.<set-x>? origin=null
+            <set-?>: GET_VAR '<set-?>: D of <root>.Test2.<set-x>? declared in <root>.Test2.<set-x>' type=D of <root>.Test2.<set-x>? origin=null
     FIELD DELEGATE name:$$delegate_0 type:<root>.IBase<kotlin.String> visibility:local [final]
     FUN FAKE_OVERRIDE name:equals visibility:public modality:OPEN <> ($this:kotlin.Any, other:kotlin.Any?) returnType:kotlin.Boolean [fake_override,operator]
       overridden:
diff --git a/compiler/testData/ir/irText/declarations/kt35550.fir.txt b/compiler/testData/ir/irText/declarations/kt35550.fir.txt
index 8fb040c1089..d1c633ffb45 100644
--- a/compiler/testData/ir/irText/declarations/kt35550.fir.txt
+++ b/compiler/testData/ir/irText/declarations/kt35550.fir.txt
@@ -34,14 +34,15 @@ FILE fqName:<root> fileName:/kt35550.kt
           receiver: GET_VAR '<this>: <root>.A declared in <root>.A' type=<root>.A origin=null
           value: GET_VAR 'i: <root>.I declared in <root>.A.<init>' type=<root>.I origin=null
     PROPERTY DELEGATED_MEMBER name:id visibility:public modality:OPEN [val]
-      FUN DELEGATED_MEMBER name:<get-id> visibility:public modality:OPEN <> ($this:<root>.A) returnType:T of <root>.I.<get-id>
+      FUN DELEGATED_MEMBER name:<get-id> visibility:public modality:OPEN <T> ($this:<root>.A) returnType:T of <root>.I.<get-id>
         correspondingProperty: PROPERTY DELEGATED_MEMBER name:id visibility:public modality:OPEN [val]
         overridden:
           public open fun <get-id> <T> (): T of <root>.I.<get-id> declared in <root>.I
+        TYPE_PARAMETER DELEGATED_MEMBER name:T index:0 variance: superTypes:[]
         $this: VALUE_PARAMETER DELEGATED_MEMBER name:<this> type:<root>.A
         BLOCK_BODY
-          RETURN type=kotlin.Nothing from='public open fun <get-id> (): T of <root>.I.<get-id> declared in <root>.A'
-            CALL 'public open fun <get-id> <T> (): T of <root>.I.<get-id> declared in <root>.I' type=T of <root>.I.<get-id> origin=null
+          RETURN type=kotlin.Nothing from='public open fun <get-id> <T> (): T of <root>.I.<get-id> declared in <root>.A'
+            CALL 'public open fun <get-id> <T> (): T of <root>.I.<get-id> declared in <root>.I' type=T of <root>.A.<get-id> origin=null
               <T>: <none>
               $this: GET_FIELD 'FIELD DELEGATE name:$$delegate_0 type:<root>.I visibility:local [final]' type=<root>.I origin=null
                 receiver: GET_VAR '<this>: <root>.A declared in <root>.A.<get-id>' type=<root>.A origin=null
diff --git a/compiler/testData/ir/irText/declarations/parameters/delegatedMembers.fir.txt b/compiler/testData/ir/irText/declarations/parameters/delegatedMembers.fir.txt
index 853e4d287c0..d2cc97ac35d 100644
--- a/compiler/testData/ir/irText/declarations/parameters/delegatedMembers.fir.txt
+++ b/compiler/testData/ir/irText/declarations/parameters/delegatedMembers.fir.txt
@@ -59,19 +59,20 @@ FILE fqName:<root> fileName:/delegatedMembers.kt
             CALL 'public abstract fun <get-bar> (): kotlin.Int declared in <root>.IBase' type=kotlin.Int origin=null
               $this: GET_FIELD 'FIELD DELEGATE name:$$delegate_0 type:<root>.IBase<TT of <root>.Test> visibility:local [final]' type=<root>.IBase<TT of <root>.Test> origin=null
                 receiver: GET_VAR '<this>: <root>.Test<TT of <root>.Test> declared in <root>.Test.<get-bar>' type=<root>.Test<TT of <root>.Test> origin=null
-    FUN DELEGATED_MEMBER name:qux visibility:public modality:OPEN <> ($this:<root>.Test<TT of <root>.Test>, t:T of <root>.IBase, x:X of <root>.IBase.qux) returnType:kotlin.Unit
+    FUN DELEGATED_MEMBER name:qux visibility:public modality:OPEN <X> ($this:<root>.Test<TT of <root>.Test>, t:TT of <root>.Test, x:X of <root>.Test.qux) returnType:kotlin.Unit
       overridden:
         public abstract fun qux <X> (t: T of <root>.IBase, x: X of <root>.IBase.qux): kotlin.Unit declared in <root>.IBase
+      TYPE_PARAMETER DELEGATED_MEMBER name:X index:0 variance: superTypes:[]
       $this: VALUE_PARAMETER DELEGATED_MEMBER name:<this> type:<root>.Test<TT of <root>.Test>
-      VALUE_PARAMETER DELEGATED_MEMBER name:t index:0 type:T of <root>.IBase
-      VALUE_PARAMETER DELEGATED_MEMBER name:x index:1 type:X of <root>.IBase.qux
+      VALUE_PARAMETER DELEGATED_MEMBER name:t index:0 type:TT of <root>.Test
+      VALUE_PARAMETER DELEGATED_MEMBER name:x index:1 type:X of <root>.Test.qux
       BLOCK_BODY
         CALL 'public abstract fun qux <X> (t: T of <root>.IBase, x: X of <root>.IBase.qux): kotlin.Unit declared in <root>.IBase' type=kotlin.Unit origin=null
           <X>: <none>
           $this: GET_FIELD 'FIELD DELEGATE name:$$delegate_0 type:<root>.IBase<TT of <root>.Test> visibility:local [final]' type=<root>.IBase<TT of <root>.Test> origin=null
             receiver: GET_VAR '<this>: <root>.Test<TT of <root>.Test> declared in <root>.Test.qux' type=<root>.Test<TT of <root>.Test> origin=null
-          t: GET_VAR 't: T of <root>.IBase declared in <root>.Test.qux' type=T of <root>.IBase origin=null
-          x: GET_VAR 'x: X of <root>.IBase.qux declared in <root>.Test.qux' type=X of <root>.IBase.qux origin=null
+          t: GET_VAR 't: TT of <root>.Test declared in <root>.Test.qux' type=TT of <root>.Test origin=null
+          x: GET_VAR 'x: X of <root>.Test.qux declared in <root>.Test.qux' type=X of <root>.Test.qux origin=null
     FIELD DELEGATE name:$$delegate_0 type:<root>.IBase<TT of <root>.Test> visibility:local [final]
     FUN FAKE_OVERRIDE name:equals visibility:public modality:OPEN <> ($this:kotlin.Any, other:kotlin.Any?) returnType:kotlin.Boolean [fake_override,operator]
       overridden: