FIR: approximate intersections in public position properly

#KT-48166 Fixed

compiler/fir/analysis-tests/testData/resolveWithStdlib/intellij/ParentOfType.fir.txt

@@ -0,0 +1,6 @@
+FILE: ParentOfType.kt
+    public final fun <T : R|kotlin/Number|> R|kotlin/Any|.parentOfTypes(vararg classes: R|kotlin/Array<out kotlin/reflect/KClass<out T>>|): R|T?| {
+        throw R|java/lang/IllegalStateException.IllegalStateException|()
+    }
+    public final val some: R|kotlin/Number?| = String(123).R|/parentOfTypes|<R|it(kotlin/Number & kotlin/Comparable<*>)|>(vararg(<getClass>(Q|kotlin/Int|), <getClass>(Q|kotlin/Double|)))
+        public get(): R|kotlin/Number?|

compiler/fir/analysis-tests/testData/resolveWithStdlib/intellij/ParentOfType.kt

@@ -0,0 +1,7 @@
+import kotlin.reflect.KClass
+
+fun <T : Number> Any.parentOfTypes(vararg classes: KClass<out T>): T? {
+    throw IllegalStateException()
+}
+
+val some = "123".parentOfTypes(Int::class, Double::class)

compiler/fir/analysis-tests/tests-gen/org/jetbrains/kotlin/test/runners/FirDiagnosticTestGenerated.java

@@ -5051,6 +5051,12 @@ public class FirDiagnosticTestGenerated extends AbstractFirDiagnosticTest {
                 runTest("compiler/fir/analysis-tests/testData/resolveWithStdlib/intellij/IntersectionWithJavaString.kt");
             }
 
+            @Test
+            @TestMetadata("ParentOfType.kt")
+            public void testParentOfType() throws Exception {
+                runTest("compiler/fir/analysis-tests/testData/resolveWithStdlib/intellij/ParentOfType.kt");
+            }
+
             @Test
             @TestMetadata("PersistentStateComponent.kt")
             public void testPersistentStateComponent() throws Exception {

compiler/fir/analysis-tests/tests-gen/org/jetbrains/kotlin/test/runners/FirDiagnosticsWithLightTreeTestGenerated.java

@@ -5051,6 +5051,12 @@ public class FirDiagnosticsWithLightTreeTestGenerated extends AbstractFirDiagnos
                 runTest("compiler/fir/analysis-tests/testData/resolveWithStdlib/intellij/IntersectionWithJavaString.kt");
             }
 
+            @Test
+            @TestMetadata("ParentOfType.kt")
+            public void testParentOfType() throws Exception {
+                runTest("compiler/fir/analysis-tests/testData/resolveWithStdlib/intellij/ParentOfType.kt");
+            }
+
             @Test
             @TestMetadata("PersistentStateComponent.kt")
             public void testPersistentStateComponent() throws Exception {

compiler/fir/cones/src/org/jetbrains/kotlin/fir/types/ConeTypes.kt

@@ -278,7 +278,7 @@ fun ConeIntersectionType.withAlternative(alternativeType: ConeKotlinType): ConeI
 }
 
 fun ConeIntersectionType.mapTypes(func: (ConeKotlinType) -> ConeKotlinType): ConeIntersectionType {
-    return ConeIntersectionType(intersectedTypes.map(func))
+    return ConeIntersectionType(intersectedTypes.map(func), alternativeType?.let(func))
 }
 
 class ConeStubType(val variable: ConeTypeVariable, override val nullability: ConeNullability) : StubTypeMarker, ConeSimpleKotlinType() {

compiler/fir/resolve/src/org/jetbrains/kotlin/fir/types/TypeUtils.kt

@@ -283,12 +283,15 @@ fun FirTypeRef.withReplacedConeType(
 fun FirTypeRef.approximated(
     typeApproximator: ConeTypeApproximator,
     toSuper: Boolean,
-    conf: TypeApproximatorConfiguration = TypeApproximatorConfiguration.PublicDeclaration
 ): FirTypeRef {
+    val alternativeType = (coneType as? ConeIntersectionType)?.alternativeType ?: coneType
+    if (alternativeType !== coneType && !alternativeType.requiresApproximationInPublicPosition()) {
+        return withReplacedConeType(alternativeType)
+    }
     val approximatedType = if (toSuper)
-        typeApproximator.approximateToSuperType(coneType, conf)
+        typeApproximator.approximateToSuperType(alternativeType, TypeApproximatorConfiguration.PublicDeclaration)
     else
-        typeApproximator.approximateToSubType(coneType, conf)
+        typeApproximator.approximateToSubType(alternativeType, TypeApproximatorConfiguration.PublicDeclaration)
     return withReplacedConeType(approximatedType)
 }
 

idea/idea-frontend-fir/idea-fir-low-level-api/tests/org/jetbrains/kotlin/idea/fir/low/level/api/diagnostic/compiler/based/DiagnosisCompilerFirTestdataTestGenerated.java

@@ -5051,6 +5051,12 @@ public class DiagnosisCompilerFirTestdataTestGenerated extends AbstractDiagnosis
                 runTest("compiler/fir/analysis-tests/testData/resolveWithStdlib/intellij/IntersectionWithJavaString.kt");
             }
 
+            @Test
+            @TestMetadata("ParentOfType.kt")
+            public void testParentOfType() throws Exception {
+                runTest("compiler/fir/analysis-tests/testData/resolveWithStdlib/intellij/ParentOfType.kt");
+            }
+
             @Test
             @TestMetadata("PersistentStateComponent.kt")
             public void testPersistentStateComponent() throws Exception {