[FIR] Support flexible types and star projections in exposed visibility declaration checker

#KT-62925

compiler/fir/checkers/src/org/jetbrains/kotlin/fir/analysis/checkers/declaration/FirExposedVisibilityDeclarationChecker.kt

@@ -218,9 +218,17 @@ object FirExposedVisibilityDeclarationChecker : FirBasicDeclarationChecker() {
 
     private fun ConeKotlinType.findVisibilityExposure(
         context: CheckerContext,
-        base: EffectiveVisibility
+        base: EffectiveVisibility,
+        visitedTypes: MutableSet<ConeKotlinType> = mutableSetOf(),
     ): Pair<FirBasedSymbol<*>, EffectiveVisibility>? {
-        val type = this as? ConeClassLikeType ?: return null
+        if (!visitedTypes.add(this)) return null
+
+        val type = when (this) {
+            is ConeClassLikeType -> this
+            is ConeFlexibleType -> lowerBound as? ConeClassLikeType ?: return null
+            else -> return null
+        }
+
         val classSymbol = type.fullyExpandedType(context.session).lookupTag.toSymbol(context.session) ?: return null
 
         val effectiveVisibility = when (classSymbol) {
@@ -239,9 +247,14 @@ object FirExposedVisibilityDeclarationChecker : FirBasicDeclarationChecker() {
             }
         }
 
-        for (it in type.typeArguments) {
-            (it as? ConeClassLikeType)?.findVisibilityExposure(context, base)?.let {
-                return it
+        for ((index, it) in type.typeArguments.withIndex()) {
+            when (it) {
+                is ConeClassLikeType -> it.findVisibilityExposure(context, base, visitedTypes)?.let { return it }
+                is ConeStarProjection -> type.toRegularClassSymbol(context.session)
+                    ?.typeParameterSymbols?.getOrNull(index)
+                    ?.resolvedBounds?.firstNotNullOfOrNull { it.type.findVisibilityExposure(context, base, visitedTypes) }
+                    ?.let { return it }
+                else -> {}
             }
         }
 

compiler/testData/diagnostics/tests/exposed/packagePrivate.fir.kt

@@ -19,9 +19,9 @@ class His {
     // Ok: internal vs package-private in same package
     internal fun internal() = My.foo()
     // Error: protected vs package-private
-    protected fun protected() = My.foo()
+    protected fun <!EXPOSED_FUNCTION_RETURN_TYPE!>protected<!>() = My.foo()
     // Error: public vs package-private
-    fun public() = My.foo()
+    fun <!EXPOSED_FUNCTION_RETURN_TYPE!>public<!>() = My.foo()
 }
 
 // FILE: other/Your.kt

compiler/testData/diagnostics/tests/exposed/typeArgs.fir.kt

@@ -13,5 +13,5 @@ interface Generic<E: <!EXPOSED_TYPE_PARAMETER_BOUND!>My<!>>
 
 interface Our {
     // invalid, Generic<My> is effectively internal
-    fun foo(): Generic<*>
-}
+    fun <!EXPOSED_FUNCTION_RETURN_TYPE!>foo<!>(): Generic<*>
+}