NI: discard def not null types if they appear in return positions, in inv or in variance

^KT-37343 Fixed

core/descriptors/src/org/jetbrains/kotlin/types/SpecialTypes.kt

@@ -21,6 +21,7 @@ import org.jetbrains.kotlin.descriptors.annotations.Annotations
 import org.jetbrains.kotlin.resolve.scopes.MemberScope
 import org.jetbrains.kotlin.storage.StorageManager
 import org.jetbrains.kotlin.types.checker.KotlinTypeRefiner
+import org.jetbrains.kotlin.types.checker.NewCapturedType
 import org.jetbrains.kotlin.types.checker.NewTypeVariableConstructor
 import org.jetbrains.kotlin.types.checker.NullabilityChecker
 import org.jetbrains.kotlin.types.model.DefinitelyNotNullTypeMarker
@@ -150,6 +151,9 @@ fun SimpleType.makeSimpleTypeDefinitelyNotNullOrNotNull(): SimpleType =
         ?: makeIntersectionTypeDefinitelyNotNullOrNotNull()
         ?: makeNullableAsSpecified(false)
 
+fun NewCapturedType.withNotNullProjection() =
+    NewCapturedType(captureStatus, constructor, lowerType, annotations, isMarkedNullable, isProjectionNotNull = true)
+
 fun UnwrappedType.makeDefinitelyNotNullOrNotNull(): UnwrappedType =
     DefinitelyNotNullType.makeDefinitelyNotNull(this)
         ?: makeIntersectionTypeDefinitelyNotNullOrNotNull()

core/descriptors/src/org/jetbrains/kotlin/types/checker/ClassicTypeSystemContext.kt

@@ -405,6 +405,17 @@ interface ClassicTypeSystemContext : TypeSystemInferenceExtensionContext, TypeSy
         return this.constructor.projection
     }
 
+    override fun CapturedTypeMarker.withNotNullProjection(): KotlinTypeMarker {
+        require(this is NewCapturedType, this::errorMessage)
+
+        return NewCapturedType(captureStatus, constructor, lowerType, annotations, isMarkedNullable, isProjectionNotNull = true)
+    }
+
+    override fun CapturedTypeMarker.isProjectionNotNull(): Boolean {
+        require(this is NewCapturedType, this::errorMessage)
+        return this.isProjectionNotNull
+    }
+
     override fun CapturedTypeMarker.typeParameter(): TypeParameterMarker? {
         require(this is NewCapturedType, this::errorMessage)
         return this.constructor.typeParameter

core/descriptors/src/org/jetbrains/kotlin/types/checker/IntersectionType.kt

@@ -94,7 +94,9 @@ object TypeIntersector {
          * and other types is captured types or type parameters without not-null upper bound. Example: `String? & T` such types we should leave as is.
          */
         val correctNullability = inputTypes.mapTo(LinkedHashSet()) {
-            if (resultNullability == ResultNullability.NOT_NULL) it.makeSimpleTypeDefinitelyNotNullOrNotNull() else it
+            if (resultNullability == ResultNullability.NOT_NULL) {
+                (if (it is NewCapturedType) it.withNotNullProjection() else it).makeSimpleTypeDefinitelyNotNullOrNotNull()
+            } else it
         }
 
         return intersectTypesWithoutIntersectionType(correctNullability)

core/descriptors/src/org/jetbrains/kotlin/types/checker/NewCapturedType.kt

@@ -110,7 +110,8 @@ class NewCapturedType(
     override val constructor: NewCapturedTypeConstructor,
     val lowerType: UnwrappedType?, // todo check lower type for nullable captured types
     override val annotations: Annotations = Annotations.EMPTY,
-    override val isMarkedNullable: Boolean = false
+    override val isMarkedNullable: Boolean = false,
+    val isProjectionNotNull: Boolean = false
 ) : SimpleType(), CapturedTypeMarker {
     internal constructor(
         captureStatus: CaptureStatus, lowerType: UnwrappedType?, projection: TypeProjection, typeParameter: TypeParameterDescriptor

core/type-system/src/org/jetbrains/kotlin/types/AbstractTypeChecker.kt

@@ -508,6 +508,9 @@ object AbstractNullabilityChecker {
         // i.e. subType is definitely not null
         if (subType.isDefinitelyNotNullType()) return true
 
+        // i.e. subType is captured type, projection of which is marked not-null
+        if (subType is CapturedTypeMarker && subType.isProjectionNotNull()) return true
+
         // i.e. subType is not-nullable
         if (hasNotNullSupertype(subType, SupertypesPolicy.LowerIfFlexible)) return true
 

core/type-system/src/org/jetbrains/kotlin/types/model/TypeSystemContext.kt

@@ -154,6 +154,7 @@ interface TypeSystemInferenceExtensionContext : TypeSystemContext, TypeSystemBui
 
     fun CapturedTypeMarker.typeConstructorProjection(): TypeArgumentMarker
     fun CapturedTypeMarker.typeParameter(): TypeParameterMarker?
+    fun CapturedTypeMarker.withNotNullProjection(): KotlinTypeMarker
 
     fun DefinitelyNotNullTypeMarker.original(): SimpleTypeMarker
 
@@ -200,6 +201,7 @@ interface TypeSystemContext : TypeSystemOptimizationContext {
 
     fun CapturedTypeMarker.typeConstructor(): CapturedTypeConstructorMarker
     fun CapturedTypeMarker.captureStatus(): CaptureStatus
+    fun CapturedTypeMarker.isProjectionNotNull(): Boolean
     fun CapturedTypeConstructorMarker.projection(): TypeArgumentMarker
 
     fun KotlinTypeMarker.argumentsCount(): Int