FIR: Respect nullability when substituting stub types

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

@@ -4973,6 +4973,12 @@ public class DiagnosisCompilerFirTestdataTestGenerated extends AbstractDiagnosis
                 runTest("compiler/fir/analysis-tests/testData/resolveWithStdlib/delegates/kt41917.kt");
             }
 
+            @Test
+            @TestMetadata("nullableTypeDelegate.kt")
+            public void testNullableTypeDelegate() throws Exception {
+                runTest("compiler/fir/analysis-tests/testData/resolveWithStdlib/delegates/nullableTypeDelegate.kt");
+            }
+
             @Test
             @TestMetadata("propertyWithFunctionalType.kt")
             public void testPropertyWithFunctionalType() throws Exception {

compiler/fir/analysis-tests/testData/resolveWithStdlib/delegates/nullableTypeDelegate.fir.txt

@@ -0,0 +1,32 @@
+FILE: nullableTypeDelegate.kt
+    public abstract interface ReadWriteProperty<R, T> : R|kotlin/Any| {
+        public abstract operator fun getValue(thisRef: R|R|, prop: R|kotlin/Any|): R|T|
+
+        public abstract operator fun setValue(thisRef: R|R|, prop: R|kotlin/Any|, value: R|T|): R|kotlin/Unit|
+
+    }
+    public abstract interface Delegate<R, T> : R|ReadWriteProperty<R, T>| {
+    }
+    public abstract interface DatabaseEntity : R|kotlin/Any| {
+    }
+    public final fun <Self : R|DatabaseEntity|, Target : R|DatabaseEntity|> R|Self|.directed(clazz: R|java/lang/Class<Target>|): R|Delegate<Self, Target?>| {
+        ^directed Null(null)!!
+    }
+    public final class MyClassSome : R|DatabaseEntity| {
+        public constructor(): R|MyClassSome| {
+            super<R|kotlin/Any|>()
+        }
+
+        public final var other: R|MyClassSome?|by this@R|/MyClassSome|.R|/directed|<R|MyClassSome|, R|MyClassSome|>(<getClass>(Q|MyClassSome|).R|kotlin/jvm/java|<R|MyClassSome|>)
+            public get(): R|MyClassSome?| {
+                ^ this@R|/MyClassSome|.D|/MyClassSome.other|.R|SubstitutionOverride</Delegate.getValue: R|Stub (builder inference): TypeVariable(_Target)?|>|(this@R|/MyClassSome|, ::R|/MyClassSome.other|)
+            }
+            public set(<set-?>: R|MyClassSome?|): R|kotlin/Unit| {
+                this@R|/MyClassSome|.D|/MyClassSome.other|.R|SubstitutionOverride</Delegate.setValue: R|kotlin/Unit|>|(this@R|/MyClassSome|, ::R|/MyClassSome.other|, R|<local>/other|)
+            }
+
+        public final fun set(link: R|MyClassSome?|): R|kotlin/Unit| {
+            this@R|/MyClassSome|.R|/MyClassSome.other| = R|<local>/link|
+        }
+
+    }

compiler/fir/analysis-tests/testData/resolveWithStdlib/delegates/nullableTypeDelegate.kt

@@ -0,0 +1,20 @@
+interface ReadWriteProperty<R, T> {
+    operator fun getValue(thisRef: R, prop: Any): T
+    operator fun setValue(thisRef: R, prop: Any, value: T)
+}
+
+
+interface Delegate<R, T> : ReadWriteProperty<R, T>
+
+interface DatabaseEntity
+
+
+fun <Self : DatabaseEntity, Target : DatabaseEntity> Self.directed(clazz: Class<Target>):
+        Delegate<Self, Target?> = null!!
+
+class MyClassSome : DatabaseEntity {
+    var other by directed(MyClassSome::class.java)
+    fun set(link: MyClassSome?) {
+        other = link
+    }
+}

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

@@ -4973,6 +4973,12 @@ public class FirDiagnosticTestGenerated extends AbstractFirDiagnosticTest {
                 runTest("compiler/fir/analysis-tests/testData/resolveWithStdlib/delegates/kt41917.kt");
             }
 
+            @Test
+            @TestMetadata("nullableTypeDelegate.kt")
+            public void testNullableTypeDelegate() throws Exception {
+                runTest("compiler/fir/analysis-tests/testData/resolveWithStdlib/delegates/nullableTypeDelegate.kt");
+            }
+
             @Test
             @TestMetadata("propertyWithFunctionalType.kt")
             public void testPropertyWithFunctionalType() throws Exception {

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

@@ -4973,6 +4973,12 @@ public class FirDiagnosticsWithLightTreeTestGenerated extends AbstractFirDiagnos
                 runTest("compiler/fir/analysis-tests/testData/resolveWithStdlib/delegates/kt41917.kt");
             }
 
+            @Test
+            @TestMetadata("nullableTypeDelegate.kt")
+            public void testNullableTypeDelegate() throws Exception {
+                runTest("compiler/fir/analysis-tests/testData/resolveWithStdlib/delegates/nullableTypeDelegate.kt");
+            }
+
             @Test
             @TestMetadata("propertyWithFunctionalType.kt")
             public void testPropertyWithFunctionalType() throws Exception {

compiler/fir/resolve/src/org/jetbrains/kotlin/fir/resolve/inference/FirDelegatedPropertyInferenceSession.kt

@@ -116,7 +116,7 @@ class FirDelegatedPropertyInferenceSession(
         return object : AbstractConeSubstitutor(typeContext) {
             override fun substituteType(type: ConeKotlinType): ConeKotlinType? {
                 if (type !is ConeStubType) return null
-                return bindings[type.constructor]
+                return bindings[type.constructor].updateNullabilityIfNeeded(type)
             }
         }
     }