[FIR] KT-56612: Fully-expand types when casting bare types

^KT-56612 Fixed

Merge-request: KT-MR-8849
Merged-by: Nikolay Lunyak <Nikolay.Lunyak@jetbrains.com>

compiler/fir/providers/src/org/jetbrains/kotlin/fir/types/TypeUnification.kt

@@ -6,6 +6,7 @@
 package org.jetbrains.kotlin.fir.types
 
 import org.jetbrains.kotlin.fir.FirSession
+import org.jetbrains.kotlin.fir.resolve.fullyExpandedType
 import org.jetbrains.kotlin.fir.symbols.impl.FirTypeParameterSymbol
 import org.jetbrains.kotlin.types.AbstractTypeChecker
 import org.jetbrains.kotlin.types.model.KotlinTypeMarker
@@ -22,8 +23,8 @@ fun FirSession.doUnify(
     targetTypeParameters: Set<FirTypeParameterSymbol>,
     result: MutableMap<FirTypeParameterSymbol, ConeTypeProjection>,
 ): Boolean {
-    val originalType = originalTypeProjection.type?.lowerBoundIfFlexible()
-    val typeWithParameters = typeWithParametersProjection.type
+    val originalType = originalTypeProjection.type?.lowerBoundIfFlexible()?.fullyExpandedType(this)
+    val typeWithParameters = typeWithParametersProjection.type?.lowerBoundIfFlexible()?.fullyExpandedType(this)
 
     if (originalType is ConeIntersectionType) {
         val intersectionResult = mutableMapOf<FirTypeParameterSymbol, ConeTypeProjection>()
@@ -68,14 +69,6 @@ fun FirSession.doUnify(
         return true
     }
 
-    if (typeWithParameters is ConeFlexibleType) {
-        return doUnify(
-            originalTypeProjection,
-            typeWithParametersProjection.replaceType(typeWithParameters.lowerBound),
-            targetTypeParameters, result,
-        )
-    }
-
     if (typeWithParameters is ConeDefinitelyNotNullType) {
         return doUnify(
             originalTypeProjection,