[NI] Discard DefNotNull types inside invariant positions

#KT-30297 Fixed
 #KT-32168 Fixed
 #KT-27722 Fixed (actually, it was fixed with addition of DefNotNullTypes, and now test was added to save this behavior)
 #KT-32345 Fixed

compiler/resolution/src/org/jetbrains/kotlin/resolve/calls/inference/InferenceUtils.kt

@@ -73,7 +73,7 @@ fun CallableDescriptor.substitute(substitutor: NewTypeSubstitutor): CallableDesc
     return substitute(TypeSubstitutor.create(wrappedSubstitution))
 }
 
-fun CallableDescriptor.substituteAndApproximateCapturedTypes(
+fun CallableDescriptor.substituteAndApproximateTypes(
     substitutor: NewTypeSubstitutor,
     typeApproximator: TypeApproximator
 ): CallableDescriptor {
@@ -82,8 +82,10 @@ fun CallableDescriptor.substituteAndApproximateCapturedTypes(
 
         override fun prepareTopLevelType(topLevelType: KotlinType, position: Variance) =
             substitutor.safeSubstitute(topLevelType.unwrap()).let { substitutedType ->
-                typeApproximator.approximateToSuperType(substitutedType, TypeApproximatorConfiguration.CapturedAndIntegerLiteralsTypesApproximation)
-                    ?: substitutedType
+                typeApproximator.approximateToSuperType(
+                    substitutedType,
+                    TypeApproximatorConfiguration.FinalApproximationAfterResolutionAndInference
+                ) ?: substitutedType
             }
     }
 

compiler/resolution/src/org/jetbrains/kotlin/types/TypeApproximator.kt

@@ -41,6 +41,7 @@ open class TypeApproximatorConfiguration {
     open val errorType get() = false
     open val integerLiteralType: Boolean = false // IntegerLiteralTypeConstructor
     open val definitelyNotNullType get() = true
+    open val definitelyNotNullTypeInInvariantPosition get() = true
     open val intersection: IntersectionStrategy = TO_COMMON_SUPERTYPE
 
     open val typeVariable: (TypeVariableTypeConstructorMarker) -> Boolean = { false }
@@ -88,6 +89,12 @@ open class TypeApproximatorConfiguration {
         override val integerLiteralType: Boolean get() = true
     }
 
+    object FinalApproximationAfterResolutionAndInference :
+        TypeApproximatorConfiguration.AbstractCapturedTypesApproximation(FROM_EXPRESSION) {
+        override val integerLiteralType: Boolean get() = true
+        override val definitelyNotNullTypeInInvariantPosition: Boolean get() = false
+    }
+
     object IntegerLiteralsTypesApproximation : TypeApproximatorConfiguration.AllFlexibleSameValue() {
         override val integerLiteralType: Boolean get() = true
         override val allFlexible: Boolean get() = true
@@ -468,8 +475,17 @@ abstract class AbstractTypeApproximator(val ctx: TypeSystemInferenceExtensionCon
 
             if (argument.isStarProjection()) continue
 
-            val argumentType = argument.getType()
-            when (val effectiveVariance = AbstractTypeChecker.effectiveVariance(parameter.getVariance(), argument.getVariance())) {
+            val effectiveVariance = AbstractTypeChecker.effectiveVariance(parameter.getVariance(), argument.getVariance())
+            if (effectiveVariance == TypeVariance.INV) {
+                val argumentType = argument.getType()
+                if (argumentType is DefinitelyNotNullTypeMarker && !conf.definitelyNotNullTypeInInvariantPosition) {
+                    newArguments[index] = argumentType.original().withNullability(false).asTypeArgument()
+                }
+            }
+
+            val argumentType = newArguments[index]?.getType() ?: argument.getType()
+
+            when (effectiveVariance) {
                 null -> {
                     return if (conf.errorType) {
                         createErrorType(