ConeSimpleKotlinType: introduce & use unwrapDefinitelyNotNull

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

@@ -14,7 +14,6 @@ import org.jetbrains.kotlin.fir.resolve.diagnostics.ConeCyclicTypeBound
 import org.jetbrains.kotlin.fir.symbols.impl.FirTypeParameterSymbol
 import org.jetbrains.kotlin.fir.types.*
 import org.jetbrains.kotlin.name.Name
-import org.jetbrains.kotlin.utils.addToStdlib.safeAs
 
 object FirCyclicTypeBoundsChecker : FirBasicDeclarationChecker() {
 
@@ -77,5 +76,6 @@ object FirCyclicTypeBoundsChecker : FirBasicDeclarationChecker() {
     private fun extractTypeParamNames(ref: FirTypeRef): Set<Name> =
         ref.unwrapBound().mapNotNull { extractTypeParamName(it.coneType) }.toSet()
 
-    private fun extractTypeParamName(type: ConeKotlinType): Name? = type.safeAs<ConeTypeParameterType>()?.lookupTag?.name
+    private fun extractTypeParamName(type: ConeKotlinType): Name? =
+        (type.lowerBoundIfFlexible().unwrapDefinitelyNotNull() as? ConeTypeParameterType)?.lookupTag?.name
 }

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

@@ -24,12 +24,14 @@ object FirTopLevelTypeAliasChecker : FirTypeAliasChecker() {
         }
 
         fun containsTypeParameter(type: ConeKotlinType): Boolean {
-            if (type is ConeTypeParameterType) {
+            val unwrapped = type.lowerBoundIfFlexible().unwrapDefinitelyNotNull()
+
+            if (unwrapped is ConeTypeParameterType) {
                 return true
             }
 
-            if (type is ConeClassLikeType && type.lookupTag.toSymbol(context.session) is FirTypeAliasSymbol) {
+            if (unwrapped is ConeClassLikeType && unwrapped.lookupTag.toSymbol(context.session) is FirTypeAliasSymbol) {
-                for (typeArgument in type.typeArguments) {
+                for (typeArgument in unwrapped.typeArguments) {
                     val typeArgumentType = (typeArgument as? ConeKotlinType) ?: (typeArgument as? ConeKotlinTypeProjection)?.type
                     if (typeArgumentType != null && containsTypeParameter(typeArgumentType)) {
                         return true

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

@@ -175,6 +175,13 @@ fun ConeKotlinType.lowerBoundIfFlexible(): ConeSimpleKotlinType {
     }
 }
 
+fun ConeSimpleKotlinType.unwrapDefinitelyNotNull(): ConeSimpleKotlinType {
+    return when (this) {
+        is ConeDefinitelyNotNullType -> original
+        else -> this
+    }
+}
+
 class ConeCapturedTypeConstructor(
     val projection: ConeTypeProjection,
     var supertypes: List<ConeKotlinType>? = null,