[FIR] Support of intersection types in bareTypes.doUnify ^KT-48832 Fixed

compiler/fir/analysis-tests/testData/resolve/types/castToBareType.fir.txt

@@ -16,6 +16,6 @@ FILE: castToBareType.kt
     public final fun foo(firAdaptee: R|FirFunction<*>|): R|kotlin/Unit| {
     }
     public final fun test(symbol: R|AbstractFirBasedSymbol<*>|): R|kotlin/Unit| {
-        lval firAdaptee: R|FirFunction<out it(FirSymbolOwner<out it(FirSymbolOwner<out it(FirSymbolOwner<out it(FirSymbolOwner<out kotlin/Any?> & FirDeclaration)> & FirDeclaration)> & FirDeclaration)> & FirDeclaration)>| = (R|<local>/symbol|.R|SubstitutionOverride</AbstractFirBasedSymbol.fir: R|CapturedType(*)|>| as R|FirFunction<out it(FirSymbolOwner<out it(FirSymbolOwner<out it(FirSymbolOwner<out it(FirSymbolOwner<out kotlin/Any?> & FirDeclaration)> & FirDeclaration)> & FirDeclaration)> & FirDeclaration)>|)
+        lval firAdaptee: R|FirFunction<FirSymbolOwner<out it(FirSymbolOwner<out it(FirSymbolOwner<out it(FirSymbolOwner<out kotlin/Any?> & FirDeclaration)> & FirDeclaration)> & FirDeclaration)>>| = (R|<local>/symbol|.R|SubstitutionOverride</AbstractFirBasedSymbol.fir: R|CapturedType(*)|>| as R|FirFunction<FirSymbolOwner<out it(FirSymbolOwner<out it(FirSymbolOwner<out it(FirSymbolOwner<out kotlin/Any?> & FirDeclaration)> & FirDeclaration)> & FirDeclaration)>>|)
         R|/foo|(R|<local>/firAdaptee|)
     }

compiler/fir/analysis-tests/testData/resolve/types/castToBareType.kt

@@ -12,6 +12,6 @@ interface AbstractFirBasedSymbol<E> where E : FirSymbolOwner<E>, E : FirDeclarat
 fun foo(firAdaptee: FirFunction<*>) {}
 
 fun test(symbol: AbstractFirBasedSymbol<*>) {
-    val firAdaptee = symbol.fir <!UNCHECKED_CAST!>as FirFunction<!>  // TODO: KT-48832
+    val firAdaptee = symbol.fir as FirFunction
     foo(firAdaptee)
 }

compiler/fir/resolve/src/org/jetbrains/kotlin/fir/resolve/transformers/body/resolve/bareTypes.kt

@@ -16,6 +16,7 @@ import org.jetbrains.kotlin.fir.resolve.fullyExpandedType
 import org.jetbrains.kotlin.fir.resolve.toSymbol
 import org.jetbrains.kotlin.fir.types.*
 import org.jetbrains.kotlin.types.AbstractTypeChecker
+import org.jetbrains.kotlin.types.model.KotlinTypeMarker
 
 fun BodyResolveComponents.computeRepresentativeTypeForBareType(type: ConeClassLikeType, originalType: ConeKotlinType): ConeKotlinType? {
     originalType.lowerBoundIfFlexible().fullyExpandedType(session).let {
@@ -90,6 +91,28 @@ private fun BodyResolveComponents.doUnify(
     val originalType = originalTypeProjection.type
     val typeWithParameters = typeWithParametersProjection.type
 
+    if (originalType is ConeIntersectionType) {
+        val intersectionResult = mutableMapOf<FirTypeParameterRef, ConeTypeProjection>()
+        for (intersectedType in originalType.intersectedTypes) {
+            val localResult = mutableMapOf<FirTypeParameterRef, ConeTypeProjection>()
+            if (!doUnify(intersectedType, typeWithParametersProjection, targetTypeParameters, localResult)) return false
+            for ((typeParameter, typeProjection) in localResult) {
+                val existingTypeProjection = intersectionResult[typeParameter]
+                if (existingTypeProjection == null
+                    || (typeProjection is KotlinTypeMarker &&
+                            existingTypeProjection is KotlinTypeMarker &&
+                            AbstractTypeChecker.isSubtypeOf(session.typeContext, typeProjection, existingTypeProjection))
+                ) {
+                    intersectionResult[typeParameter] = typeProjection
+                }
+            }
+        }
+        for ((key, value) in intersectionResult) {
+            result[key] = value
+        }
+        return true
+    }
+
     // in Foo ~ in X  =>  Foo ~ X
     if (originalTypeProjection.kind == typeWithParametersProjection.kind &&
         originalTypeProjection.kind != ProjectionKind.INVARIANT && originalTypeProjection.kind != ProjectionKind.STAR) {