[FIR] Fix lower bound of flexible type variable not becoming DNN in warning-severity case

The bug was introduced as part of the implementation for Java
nullability warnings.

#KT-58933 Fixed

compiler/fir/java/src/org/jetbrains/kotlin/fir/java/enhancement/javaTypeUtils.kt

@@ -12,6 +12,7 @@ import org.jetbrains.kotlin.fir.symbols.ConeClassifierLookupTag
 import org.jetbrains.kotlin.fir.types.*
 import org.jetbrains.kotlin.load.java.typeEnhancement.*
 import org.jetbrains.kotlin.name.ClassId
+import org.jetbrains.kotlin.utils.addToStdlib.applyIf
 
 internal fun ConeKotlinType.enhance(session: FirSession, qualifiers: IndexedJavaTypeQualifiers): ConeKotlinType? =
     enhanceConeKotlinType(session, qualifiers, 0, mutableListOf<Int>().apply { computeSubtreeSizes(this) })
@@ -115,6 +116,10 @@ private fun ConeSimpleKotlinType.enhanceInflexibleType(
             enhancedTag.constructType(typeArguments, isNullable, newAttributes)
         } else {
             this.withAttributes(newAttributes)
+        }.applyIf(isFromDefinitelyNotNullType) {
+            // If the original type was DNN, we need to wrap the result in a DNN type because `this` is the non-DNN part of the original.
+            // In the non-warning case, this happens in the nested call and so `enhanced` is already DNN.
+            ConeDefinitelyNotNullType.create(this, session.typeContext)
         }
     } else {
         enhanced

compiler/testData/diagnostics/foreignAnnotationsTests/java8Tests/jspecify/warnMode/UnannotatedWildcard.fir.kt

@@ -1,17 +0,0 @@
-// JSPECIFY_STATE: warn
-// FILE: J1.java
-import org.jspecify.annotations.*;
-
-@NullMarked
-public interface J1<T extends @Nullable Object> {
-    T foo();
-}
-
-// FILE: J2.java
-public interface J2 {
-    J1<?> bar();
-}
-
-// FILE: main.kt
-// jspecify_nullness_mismatch
-fun baz(j2: J2): Any = <!NULLABILITY_MISMATCH_BASED_ON_JAVA_ANNOTATIONS!>j2.bar().foo()<!> // Any..Any?

compiler/testData/diagnostics/foreignAnnotationsTests/java8Tests/jspecify/warnMode/UnannotatedWildcard.kt

@@ -1,3 +1,4 @@
+// FIR_IDENTICAL
 // JSPECIFY_STATE: warn
 // FILE: J1.java
 import org.jspecify.annotations.*;

compiler/testData/diagnostics/foreignAnnotationsTests/java8Tests/jspecifyOld/warnMode/UnannotatedWildcard.fir.kt

@@ -1,16 +0,0 @@
-// JSPECIFY_STATE: warn
-// FILE: J1.java
-import org.jspecify.nullness.*;
-
-@NullMarked
-public interface J1<T extends @Nullable Object> {
-    T foo();
-}
-
-// FILE: J2.java
-public interface J2 {
-    J1<?> bar();
-}
-
-// FILE: main.kt
-fun baz(j2: J2): Any = <!NULLABILITY_MISMATCH_BASED_ON_JAVA_ANNOTATIONS!>j2.bar().foo()<!> // Any..Any?

compiler/testData/diagnostics/foreignAnnotationsTests/java8Tests/jspecifyOld/warnMode/UnannotatedWildcard.kt

@@ -1,3 +1,4 @@
+// FIR_IDENTICAL
 // JSPECIFY_STATE: warn
 // FILE: J1.java
 import org.jspecify.nullness.*;

compiler/testData/diagnostics/foreignAnnotationsTests/tests/jsr305/nullabilityWarnings/override.fir.kt

@@ -62,3 +62,23 @@ abstract class A<T> : Provider<T> {
     <!WRONG_NULLABILITY_FOR_JAVA_OVERRIDE!>override<!> fun getSet(x: T): T = x
     <!NOTHING_TO_OVERRIDE!>override<!> fun getSetNullable(x: T): T = x
 }
+
+abstract class B<T> : Provider<T> {
+    override fun get(): T & Any = null!!
+    override fun getNullable(): T? = null!!
+    override fun set(x: T & Any) {} // False positive in K1
+    override fun setNullable(x: T?) {}
+
+    override fun getSet(x: T & Any): T & Any = x // False positive in K1
+    override fun getSetNullable(x: T?): T? = x
+}
+
+abstract class C<T> : Provider<T> {
+    <!WRONG_NULLABILITY_FOR_JAVA_OVERRIDE!>override<!> fun getSet(x: T): T & Any = x!! // Missing warning in K1, K2 get's this right
+    <!NOTHING_TO_OVERRIDE!>override<!> fun getSetNullable(x: T): T? = x
+}
+
+abstract class D<T> : Provider<T> {
+    <!WRONG_NULLABILITY_FOR_JAVA_OVERRIDE!>override<!> fun getSet(x: T & Any): T = x<!UNNECESSARY_NOT_NULL_ASSERTION!>!!<!> // False positive in K1
+    override fun getSetNullable(x: T?): T = x!!
+}

compiler/testData/diagnostics/foreignAnnotationsTests/tests/jsr305/nullabilityWarnings/override.kt

@@ -62,3 +62,23 @@ abstract class A<T> : Provider<T> {
     <!WRONG_NULLABILITY_FOR_JAVA_OVERRIDE!>override<!> fun getSet(x: T): T = x
     <!NOTHING_TO_OVERRIDE!>override<!> fun getSetNullable(x: T): T = x
 }
+
+abstract class B<T> : Provider<T> {
+    override fun get(): T & Any = null!!
+    override fun getNullable(): T? = null!!
+    <!NOTHING_TO_OVERRIDE!>override<!> fun set(x: T & Any) {} // False positive in K1
+    override fun setNullable(x: T?) {}
+
+    <!NOTHING_TO_OVERRIDE!>override<!> fun getSet(x: T & Any): T & Any = x // False positive in K1
+    override fun getSetNullable(x: T?): T? = x
+}
+
+abstract class C<T> : Provider<T> {
+    override fun getSet(x: T): T & Any = x!! // Missing warning in K1, K2 get's this right
+    <!NOTHING_TO_OVERRIDE!>override<!> fun getSetNullable(x: T): T? = x
+}
+
+abstract class D<T> : Provider<T> {
+    <!NOTHING_TO_OVERRIDE!>override<!> fun getSet(x: T & Any): T = x<!UNNECESSARY_NOT_NULL_ASSERTION!>!!<!> // False positive in K1
+    override fun getSetNullable(x: T?): T = x!!
+}