diff --git a/analysis/analysis-api-fir/src/org/jetbrains/kotlin/analysis/api/fir/diagnostics/KtFirDataClassConverters.kt b/analysis/analysis-api-fir/src/org/jetbrains/kotlin/analysis/api/fir/diagnostics/KtFirDataClassConverters.kt
index e16ebb9daf9..87ff8d91a40 100644
--- a/analysis/analysis-api-fir/src/org/jetbrains/kotlin/analysis/api/fir/diagnostics/KtFirDataClassConverters.kt
+++ b/analysis/analysis-api-fir/src/org/jetbrains/kotlin/analysis/api/fir/diagnostics/KtFirDataClassConverters.kt
@@ -1891,6 +1891,12 @@ internal val KT_DIAGNOSTIC_CONVERTER = KtDiagnosticConverterBuilder.buildConvert
             token,
         )
     }
+    add(FirErrors.REDUNDANT_NULLABLE) { firDiagnostic ->
+        RedundantNullableImpl(
+            firDiagnostic as KtPsiDiagnostic,
+            token,
+        )
+    }
     add(FirErrors.EXTENSION_IN_CLASS_REFERENCE_NOT_ALLOWED) { firDiagnostic ->
         ExtensionInClassReferenceNotAllowedImpl(
             firSymbolBuilder.callableBuilder.buildCallableSymbol(firDiagnostic.a.fir),
diff --git a/analysis/analysis-api-fir/src/org/jetbrains/kotlin/analysis/api/fir/diagnostics/KtFirDiagnostics.kt b/analysis/analysis-api-fir/src/org/jetbrains/kotlin/analysis/api/fir/diagnostics/KtFirDiagnostics.kt
index d8e9f15a2da..c7c55a90953 100644
--- a/analysis/analysis-api-fir/src/org/jetbrains/kotlin/analysis/api/fir/diagnostics/KtFirDiagnostics.kt
+++ b/analysis/analysis-api-fir/src/org/jetbrains/kotlin/analysis/api/fir/diagnostics/KtFirDiagnostics.kt
@@ -1348,6 +1348,10 @@ sealed class KtFirDiagnostic<PSI : PsiElement> : KtDiagnosticWithPsi<PSI> {
         abstract val isCastToNotNull: Boolean
     }
 
+    abstract class RedundantNullable : KtFirDiagnostic<KtTypeReference>() {
+        override val diagnosticClass get() = RedundantNullable::class
+    }
+
     abstract class ExtensionInClassReferenceNotAllowed : KtFirDiagnostic<KtExpression>() {
         override val diagnosticClass get() = ExtensionInClassReferenceNotAllowed::class
         abstract val referencedDeclaration: KtCallableSymbol
diff --git a/analysis/analysis-api-fir/src/org/jetbrains/kotlin/analysis/api/fir/diagnostics/KtFirDiagnosticsImpl.kt b/analysis/analysis-api-fir/src/org/jetbrains/kotlin/analysis/api/fir/diagnostics/KtFirDiagnosticsImpl.kt
index e2299dd3cc0..ee202db804a 100644
--- a/analysis/analysis-api-fir/src/org/jetbrains/kotlin/analysis/api/fir/diagnostics/KtFirDiagnosticsImpl.kt
+++ b/analysis/analysis-api-fir/src/org/jetbrains/kotlin/analysis/api/fir/diagnostics/KtFirDiagnosticsImpl.kt
@@ -1617,6 +1617,11 @@ internal class SmartcastImpossibleImpl(
     override val token: ValidityToken,
 ) : KtFirDiagnostic.SmartcastImpossible(), KtAbstractFirDiagnostic<KtExpression>
 
+internal class RedundantNullableImpl(
+    override val firDiagnostic: KtPsiDiagnostic,
+    override val token: ValidityToken,
+) : KtFirDiagnostic.RedundantNullable(), KtAbstractFirDiagnostic<KtTypeReference>
+
 internal class ExtensionInClassReferenceNotAllowedImpl(
     override val referencedDeclaration: KtCallableSymbol,
     override val firDiagnostic: KtPsiDiagnostic,
diff --git a/analysis/low-level-api-fir/src/org/jetbrains/kotlin/analysis/low/level/api/fir/diagnostics/AbstractFirIdeDiagnosticsCollector.kt b/analysis/low-level-api-fir/src/org/jetbrains/kotlin/analysis/low/level/api/fir/diagnostics/AbstractFirIdeDiagnosticsCollector.kt
index 143212a8a2d..bc73d7e5527 100644
--- a/analysis/low-level-api-fir/src/org/jetbrains/kotlin/analysis/low/level/api/fir/diagnostics/AbstractFirIdeDiagnosticsCollector.kt
+++ b/analysis/low-level-api-fir/src/org/jetbrains/kotlin/analysis/low/level/api/fir/diagnostics/AbstractFirIdeDiagnosticsCollector.kt
@@ -90,7 +90,7 @@ private object CheckersFactory {
     }
 
     private fun createTypeCheckers(useExtendedCheckers: Boolean): TypeCheckers? =
-        if (useExtendedCheckers) null else CommonTypeCheckers
+        if (useExtendedCheckers) ExtendedTypeCheckers else CommonTypeCheckers
 
 
     @OptIn(ExperimentalStdlibApi::class)
diff --git a/compiler/fir/checkers/checkers-component-generator/src/org/jetbrains/kotlin/fir/checkers/generator/diagnostics/FirDiagnosticsList.kt b/compiler/fir/checkers/checkers-component-generator/src/org/jetbrains/kotlin/fir/checkers/generator/diagnostics/FirDiagnosticsList.kt
index c9d2a37db83..122894963e6 100644
--- a/compiler/fir/checkers/checkers-component-generator/src/org/jetbrains/kotlin/fir/checkers/generator/diagnostics/FirDiagnosticsList.kt
+++ b/compiler/fir/checkers/checkers-component-generator/src/org/jetbrains/kotlin/fir/checkers/generator/diagnostics/FirDiagnosticsList.kt
@@ -655,6 +655,8 @@ object DIAGNOSTICS_LIST : DiagnosticList("FirErrors") {
             parameter<String>("description")
             parameter<Boolean>("isCastToNotNull")
         }
+
+        val REDUNDANT_NULLABLE by warning<KtTypeReference>(PositioningStrategy.REDUNDANT_NULLABLE)
     }
 
     val REFLECTION by object : DiagnosticGroup("Reflection") {
diff --git a/compiler/fir/checkers/checkers-component-generator/src/org/jetbrains/kotlin/fir/checkers/generator/diagnostics/model/RegularDiagnosticData.kt b/compiler/fir/checkers/checkers-component-generator/src/org/jetbrains/kotlin/fir/checkers/generator/diagnostics/model/RegularDiagnosticData.kt
index 2b14b83b2d8..be7002dc3bd 100644
--- a/compiler/fir/checkers/checkers-component-generator/src/org/jetbrains/kotlin/fir/checkers/generator/diagnostics/model/RegularDiagnosticData.kt
+++ b/compiler/fir/checkers/checkers-component-generator/src/org/jetbrains/kotlin/fir/checkers/generator/diagnostics/model/RegularDiagnosticData.kt
@@ -111,6 +111,7 @@ enum class PositioningStrategy(private val strategy: String? = null) {
     PROPERTY_DELEGATE,
     IMPORT_ALIAS,
     DECLARATION_START_TO_NAME,
+    REDUNDANT_NULLABLE,
 
     ;
 
diff --git a/compiler/fir/checkers/gen/org/jetbrains/kotlin/fir/analysis/diagnostics/FirErrors.kt b/compiler/fir/checkers/gen/org/jetbrains/kotlin/fir/analysis/diagnostics/FirErrors.kt
index 2b887a671ef..e3c8290a804 100644
--- a/compiler/fir/checkers/gen/org/jetbrains/kotlin/fir/analysis/diagnostics/FirErrors.kt
+++ b/compiler/fir/checkers/gen/org/jetbrains/kotlin/fir/analysis/diagnostics/FirErrors.kt
@@ -395,6 +395,7 @@ object FirErrors {
     val TYPE_VARIANCE_CONFLICT by error4<PsiElement, FirTypeParameterSymbol, Variance, Variance, ConeKotlinType>(SourceElementPositioningStrategies.DECLARATION_SIGNATURE_OR_DEFAULT)
     val TYPE_VARIANCE_CONFLICT_IN_EXPANDED_TYPE by error4<PsiElement, FirTypeParameterSymbol, Variance, Variance, ConeKotlinType>(SourceElementPositioningStrategies.DECLARATION_SIGNATURE_OR_DEFAULT)
     val SMARTCAST_IMPOSSIBLE by error4<KtExpression, ConeKotlinType, FirExpression, String, Boolean>()
+    val REDUNDANT_NULLABLE by warning0<KtTypeReference>(SourceElementPositioningStrategies.REDUNDANT_NULLABLE)
 
     // Reflection
     val EXTENSION_IN_CLASS_REFERENCE_NOT_ALLOWED by error1<KtExpression, FirCallableSymbol<*>>(SourceElementPositioningStrategies.REFERENCE_BY_QUALIFIED)
diff --git a/compiler/fir/checkers/src/org/jetbrains/kotlin/fir/analysis/checkers/CommonTypeCheckers.kt b/compiler/fir/checkers/src/org/jetbrains/kotlin/fir/analysis/checkers/CommonTypeCheckers.kt
index f80c9f491ae..89f57b4b203 100644
--- a/compiler/fir/checkers/src/org/jetbrains/kotlin/fir/analysis/checkers/CommonTypeCheckers.kt
+++ b/compiler/fir/checkers/src/org/jetbrains/kotlin/fir/analysis/checkers/CommonTypeCheckers.kt
@@ -12,6 +12,6 @@ object CommonTypeCheckers : TypeCheckers() {
         FirTypeAnnotationChecker,
         FirSuspendModifierChecker,
         FirDeprecatedTypeChecker,
-        FirOptInUsageTypeRefChecker,
+        FirOptInUsageTypeRefChecker
     )
 }
diff --git a/compiler/fir/checkers/src/org/jetbrains/kotlin/fir/analysis/checkers/ExtendedTypeCheckers.kt b/compiler/fir/checkers/src/org/jetbrains/kotlin/fir/analysis/checkers/ExtendedTypeCheckers.kt
new file mode 100644
index 00000000000..ab2587e463e
--- /dev/null
+++ b/compiler/fir/checkers/src/org/jetbrains/kotlin/fir/analysis/checkers/ExtendedTypeCheckers.kt
@@ -0,0 +1,15 @@
+/*
+ * Copyright 2010-2021 JetBrains s.r.o. and Kotlin Programming Language contributors.
+ * Use of this source code is governed by the Apache 2.0 license that can be found in the license/LICENSE.txt file.
+ */
+
+package org.jetbrains.kotlin.fir.analysis.checkers
+
+import org.jetbrains.kotlin.fir.analysis.checkers.extended.RedundantNullableChecker
+import org.jetbrains.kotlin.fir.analysis.checkers.type.*
+
+object ExtendedTypeCheckers : TypeCheckers() {
+    override val typeRefCheckers: Set<FirTypeRefChecker> = setOf(
+        RedundantNullableChecker
+    )
+}
\ No newline at end of file
diff --git a/compiler/fir/checkers/src/org/jetbrains/kotlin/fir/analysis/checkers/SourceNavigator.kt b/compiler/fir/checkers/src/org/jetbrains/kotlin/fir/analysis/checkers/SourceNavigator.kt
index 4defdb5bcf3..847742c4582 100644
--- a/compiler/fir/checkers/src/org/jetbrains/kotlin/fir/analysis/checkers/SourceNavigator.kt
+++ b/compiler/fir/checkers/src/org/jetbrains/kotlin/fir/analysis/checkers/SourceNavigator.kt
@@ -6,13 +6,11 @@
 package org.jetbrains.kotlin.fir.analysis.checkers
 
 import com.intellij.lang.LighterASTNode
+import com.intellij.openapi.util.Ref
 import com.intellij.psi.PsiElement
 import com.intellij.psi.PsiNameIdentifierOwner
 import com.intellij.psi.impl.source.tree.LeafPsiElement
-import org.jetbrains.kotlin.KtLightSourceElement
-import org.jetbrains.kotlin.KtPsiSourceElement
-import org.jetbrains.kotlin.KtSourceElement
-import org.jetbrains.kotlin.KtNodeTypes
+import org.jetbrains.kotlin.*
 import org.jetbrains.kotlin.fir.FirElement
 import org.jetbrains.kotlin.diagnostics.getAncestors
 import org.jetbrains.kotlin.diagnostics.nameIdentifier
@@ -40,6 +38,8 @@ interface SourceNavigator {
 
     fun FirValueParameterSymbol.isCatchElementParameter(): Boolean
 
+    fun FirTypeRef.isRedundantNullable(): Boolean
+
     companion object {
 
         private val lightTreeInstance = LightTreeSourceNavigator()
@@ -90,6 +90,19 @@ open class LightTreeSourceNavigator : SourceNavigator {
         return source?.getParentOfParent()?.tokenType == KtNodeTypes.CATCH
     }
 
+    override fun FirTypeRef.isRedundantNullable(): Boolean {
+        val source = source ?: return false
+        val ref = Ref<Array<LighterASTNode?>>()
+        val firstChild = getNullableChild(source, source.lighterASTNode, ref) ?: return false
+        return getNullableChild(source, firstChild, ref) != null
+    }
+
+    private fun getNullableChild(source: KtSourceElement, node: LighterASTNode, ref: Ref<Array<LighterASTNode?>>): LighterASTNode? {
+        source.treeStructure.getChildren(node, ref)
+        val firstChild = ref.get().firstOrNull() ?: return null
+        return if (firstChild.tokenType != KtNodeTypes.NULLABLE_TYPE) null else firstChild
+    }
+
     private fun KtSourceElement?.getParentOfParent(): LighterASTNode? {
         val source = this ?: return null
         var parent = source.treeStructure.getParent(source.lighterASTNode)
@@ -131,4 +144,11 @@ object PsiSourceNavigator : LightTreeSourceNavigator() {
     override fun FirValueParameterSymbol.isCatchElementParameter(): Boolean {
         return source?.psi<PsiElement>()?.parent?.parent is KtCatchClause
     }
+
+    override fun FirTypeRef.isRedundantNullable(): Boolean {
+        val source = source ?: return false
+        val typeReference = (source.psi as? KtTypeReference) ?: return false
+        val typeElement = typeReference.typeElement as? KtNullableType ?: return false
+        return typeElement.innerType is KtNullableType
+    }
 }
diff --git a/compiler/fir/checkers/src/org/jetbrains/kotlin/fir/analysis/checkers/extended/RedundantNullableChecker.kt b/compiler/fir/checkers/src/org/jetbrains/kotlin/fir/analysis/checkers/extended/RedundantNullableChecker.kt
new file mode 100644
index 00000000000..2824c1c6b2c
--- /dev/null
+++ b/compiler/fir/checkers/src/org/jetbrains/kotlin/fir/analysis/checkers/extended/RedundantNullableChecker.kt
@@ -0,0 +1,41 @@
+/*
+ * Copyright 2010-2021 JetBrains s.r.o. and Kotlin Programming Language contributors.
+ * Use of this source code is governed by the Apache 2.0 license that can be found in the license/LICENSE.txt file.
+ */
+
+package org.jetbrains.kotlin.fir.analysis.checkers.extended
+
+import org.jetbrains.kotlin.diagnostics.DiagnosticReporter
+import org.jetbrains.kotlin.diagnostics.reportOn
+import org.jetbrains.kotlin.fir.analysis.checkers.SourceNavigator
+import org.jetbrains.kotlin.fir.analysis.checkers.context.CheckerContext
+import org.jetbrains.kotlin.fir.analysis.checkers.toClassLikeSymbol
+import org.jetbrains.kotlin.fir.analysis.checkers.type.FirTypeRefChecker
+import org.jetbrains.kotlin.fir.analysis.diagnostics.FirErrors.REDUNDANT_NULLABLE
+import org.jetbrains.kotlin.fir.symbols.impl.FirTypeAliasSymbol
+import org.jetbrains.kotlin.fir.types.*
+
+object RedundantNullableChecker : FirTypeRefChecker() {
+    override fun check(typeRef: FirTypeRef, context: CheckerContext, reporter: DiagnosticReporter) {
+        if (typeRef !is FirResolvedTypeRef || typeRef.isMarkedNullable != true) return
+
+        var symbol = typeRef.toClassLikeSymbol(context.session)
+        if (symbol is FirTypeAliasSymbol) {
+            while (symbol is FirTypeAliasSymbol) {
+                val resolvedExpandedTypeRef = symbol.resolvedExpandedTypeRef
+                if (resolvedExpandedTypeRef.type.isMarkedNullable) {
+                    reporter.reportOn(typeRef.source, REDUNDANT_NULLABLE, context)
+                    break
+                } else {
+                    symbol = resolvedExpandedTypeRef.toClassLikeSymbol(context.session)
+                }
+            }
+        } else {
+            with(SourceNavigator.forElement(typeRef)) {
+                if (typeRef.isRedundantNullable()) {
+                    reporter.reportOn(typeRef.source, REDUNDANT_NULLABLE, context)
+                }
+            }
+        }
+    }
+}
\ No newline at end of file
diff --git a/compiler/fir/checkers/src/org/jetbrains/kotlin/fir/analysis/diagnostics/FirErrorsDefaultMessages.kt b/compiler/fir/checkers/src/org/jetbrains/kotlin/fir/analysis/diagnostics/FirErrorsDefaultMessages.kt
index c9af9e0891b..dac657f1adc 100644
--- a/compiler/fir/checkers/src/org/jetbrains/kotlin/fir/analysis/diagnostics/FirErrorsDefaultMessages.kt
+++ b/compiler/fir/checkers/src/org/jetbrains/kotlin/fir/analysis/diagnostics/FirErrorsDefaultMessages.kt
@@ -236,14 +236,7 @@ import org.jetbrains.kotlin.fir.analysis.diagnostics.FirErrors.INFIX_MODIFIER_RE
 import org.jetbrains.kotlin.fir.analysis.diagnostics.FirErrors.INITIALIZATION_BEFORE_DECLARATION
 import org.jetbrains.kotlin.fir.analysis.diagnostics.FirErrors.INITIALIZER_REQUIRED_FOR_DESTRUCTURING_DECLARATION
 import org.jetbrains.kotlin.fir.analysis.diagnostics.FirErrors.INITIALIZER_TYPE_MISMATCH
-import org.jetbrains.kotlin.fir.analysis.diagnostics.FirErrors.VALUE_CLASS_CANNOT_BE_RECURSIVE
-import org.jetbrains.kotlin.fir.analysis.diagnostics.FirErrors.VALUE_CLASS_CANNOT_EXTEND_CLASSES
-import org.jetbrains.kotlin.fir.analysis.diagnostics.FirErrors.VALUE_CLASS_CANNOT_IMPLEMENT_INTERFACE_BY_DELEGATION
-import org.jetbrains.kotlin.fir.analysis.diagnostics.FirErrors.VALUE_CLASS_CONSTRUCTOR_NOT_FINAL_READ_ONLY_PARAMETER
 import org.jetbrains.kotlin.fir.analysis.diagnostics.FirErrors.INLINE_CLASS_CONSTRUCTOR_WRONG_PARAMETERS_SIZE
-import org.jetbrains.kotlin.fir.analysis.diagnostics.FirErrors.VALUE_CLASS_HAS_INAPPLICABLE_PARAMETER_TYPE
-import org.jetbrains.kotlin.fir.analysis.diagnostics.FirErrors.VALUE_CLASS_NOT_FINAL
-import org.jetbrains.kotlin.fir.analysis.diagnostics.FirErrors.VALUE_CLASS_NOT_TOP_LEVEL
 import org.jetbrains.kotlin.fir.analysis.diagnostics.FirErrors.INLINE_PROPERTY_WITH_BACKING_FIELD
 import org.jetbrains.kotlin.fir.analysis.diagnostics.FirErrors.INLINE_SUSPEND_FUNCTION_TYPE_UNSUPPORTED
 import org.jetbrains.kotlin.fir.analysis.diagnostics.FirErrors.INNER_CLASS_INSIDE_VALUE_CLASS
@@ -394,6 +387,7 @@ import org.jetbrains.kotlin.fir.analysis.diagnostics.FirErrors.REDUNDANT_LABEL_W
 import org.jetbrains.kotlin.fir.analysis.diagnostics.FirErrors.REDUNDANT_MODALITY_MODIFIER
 import org.jetbrains.kotlin.fir.analysis.diagnostics.FirErrors.REDUNDANT_MODIFIER
 import org.jetbrains.kotlin.fir.analysis.diagnostics.FirErrors.REDUNDANT_MODIFIER_FOR_TARGET
+import org.jetbrains.kotlin.fir.analysis.diagnostics.FirErrors.REDUNDANT_NULLABLE
 import org.jetbrains.kotlin.fir.analysis.diagnostics.FirErrors.REDUNDANT_OPEN_IN_INTERFACE
 import org.jetbrains.kotlin.fir.analysis.diagnostics.FirErrors.REDUNDANT_PROJECTION
 import org.jetbrains.kotlin.fir.analysis.diagnostics.FirErrors.REDUNDANT_RETURN_UNIT_TYPE
@@ -501,6 +495,13 @@ import org.jetbrains.kotlin.fir.analysis.diagnostics.FirErrors.USELESS_ELVIS_RIG
 import org.jetbrains.kotlin.fir.analysis.diagnostics.FirErrors.USELESS_IS_CHECK
 import org.jetbrains.kotlin.fir.analysis.diagnostics.FirErrors.USELESS_VARARG_ON_PARAMETER
 import org.jetbrains.kotlin.fir.analysis.diagnostics.FirErrors.VALUE_CLASS_CANNOT_BE_CLONEABLE
+import org.jetbrains.kotlin.fir.analysis.diagnostics.FirErrors.VALUE_CLASS_CANNOT_BE_RECURSIVE
+import org.jetbrains.kotlin.fir.analysis.diagnostics.FirErrors.VALUE_CLASS_CANNOT_EXTEND_CLASSES
+import org.jetbrains.kotlin.fir.analysis.diagnostics.FirErrors.VALUE_CLASS_CANNOT_IMPLEMENT_INTERFACE_BY_DELEGATION
+import org.jetbrains.kotlin.fir.analysis.diagnostics.FirErrors.VALUE_CLASS_CONSTRUCTOR_NOT_FINAL_READ_ONLY_PARAMETER
+import org.jetbrains.kotlin.fir.analysis.diagnostics.FirErrors.VALUE_CLASS_HAS_INAPPLICABLE_PARAMETER_TYPE
+import org.jetbrains.kotlin.fir.analysis.diagnostics.FirErrors.VALUE_CLASS_NOT_FINAL
+import org.jetbrains.kotlin.fir.analysis.diagnostics.FirErrors.VALUE_CLASS_NOT_TOP_LEVEL
 import org.jetbrains.kotlin.fir.analysis.diagnostics.FirErrors.VALUE_PARAMETER_WITH_NO_TYPE_ANNOTATION
 import org.jetbrains.kotlin.fir.analysis.diagnostics.FirErrors.VAL_OR_VAR_ON_CATCH_PARAMETER
 import org.jetbrains.kotlin.fir.analysis.diagnostics.FirErrors.VAL_OR_VAR_ON_FUN_PARAMETER
@@ -622,6 +623,7 @@ object FirErrorsDefaultMessages : BaseDiagnosticRendererFactory() {
         map.put(SUPERTYPE_IS_EXTENSION_FUNCTION_TYPE, "Extension function type is not allowed as supertypes")
         map.put(SINGLETON_IN_SUPERTYPE, "Cannot inherit from a singleton")
         map.put(NULLABLE_SUPERTYPE, "A supertype cannot be nullable")
+        map.put(REDUNDANT_NULLABLE, "Redundant '?'")
         map.put(MANY_CLASSES_IN_SUPERTYPE_LIST, "Only one class may appear in a supertype list")
         map.put(SUPERTYPE_APPEARS_TWICE, "A supertype appears twice")
         map.put(CLASS_IN_SUPERTYPE_FOR_ENUM, "Enum class cannot inherit from classes")
diff --git a/compiler/fir/entrypoint/src/org/jetbrains/kotlin/fir/checkers/CheckersContainers.kt b/compiler/fir/entrypoint/src/org/jetbrains/kotlin/fir/checkers/CheckersContainers.kt
index 34416431ab7..571c168a12b 100644
--- a/compiler/fir/entrypoint/src/org/jetbrains/kotlin/fir/checkers/CheckersContainers.kt
+++ b/compiler/fir/entrypoint/src/org/jetbrains/kotlin/fir/checkers/CheckersContainers.kt
@@ -19,6 +19,7 @@ fun FirSessionFactory.FirSessionConfigurator.registerCommonCheckers() {
 fun FirSessionFactory.FirSessionConfigurator.registerExtendedCommonCheckers() {
     useCheckers(ExtendedExpressionCheckers)
     useCheckers(ExtendedDeclarationCheckers)
+    useCheckers(ExtendedTypeCheckers)
 }
 
 fun FirSessionFactory.FirSessionConfigurator.registerJvmCheckers() {
diff --git a/compiler/fir/tree/src/org/jetbrains/kotlin/fir/types/FirTypeUtils.kt b/compiler/fir/tree/src/org/jetbrains/kotlin/fir/types/FirTypeUtils.kt
index 02a0b376f4d..3370a93f2ab 100644
--- a/compiler/fir/tree/src/org/jetbrains/kotlin/fir/types/FirTypeUtils.kt
+++ b/compiler/fir/tree/src/org/jetbrains/kotlin/fir/types/FirTypeUtils.kt
@@ -62,20 +62,20 @@ fun FirExpression.isStableSmartcast(): Boolean {
     return this is FirExpressionWithSmartcast && this.isStable
 }
 
-private val FirTypeRef.classLikeTypeOrNull: ConeClassLikeType?
+private val FirTypeRef.lookupTagBasedOrNull: ConeLookupTagBasedType?
     get() = when (this) {
         is FirImplicitBuiltinTypeRef -> type
-        is FirResolvedTypeRef -> type as? ConeClassLikeType
+        is FirResolvedTypeRef -> type as? ConeLookupTagBasedType
         else -> null
     }
 
 private fun FirTypeRef.isBuiltinType(classId: ClassId, isNullable: Boolean): Boolean {
-    val type = this.classLikeTypeOrNull ?: return false
-    return type.lookupTag.classId == classId && type.isNullable == isNullable
+    val type = this.lookupTagBasedOrNull ?: return false
+    return (type as? ConeClassLikeType)?.lookupTag?.classId == classId && type.isNullable == isNullable
 }
 
 val FirTypeRef.isMarkedNullable: Boolean?
-    get() = classLikeTypeOrNull?.isMarkedNullable
+    get() = if (this is FirTypeRefWithNullability) this.isMarkedNullable else lookupTagBasedOrNull?.isMarkedNullable
 
 val FirFunctionTypeRef.parametersCount: Int
     get() = if (receiverTypeRef != null)
diff --git a/compiler/frontend.common-psi/src/org/jetbrains/kotlin/diagnostics/LightTreePositioningStrategies.kt b/compiler/frontend.common-psi/src/org/jetbrains/kotlin/diagnostics/LightTreePositioningStrategies.kt
index 9067d3da625..b8d1a430eb3 100644
--- a/compiler/frontend.common-psi/src/org/jetbrains/kotlin/diagnostics/LightTreePositioningStrategies.kt
+++ b/compiler/frontend.common-psi/src/org/jetbrains/kotlin/diagnostics/LightTreePositioningStrategies.kt
@@ -14,7 +14,6 @@ import com.intellij.util.diff.FlyweightCapableTreeStructure
 import org.jetbrains.kotlin.KtNodeType
 import org.jetbrains.kotlin.KtNodeTypes
 import org.jetbrains.kotlin.KtSourceElement
-import org.jetbrains.kotlin.diagnostics.PositioningStrategies
 import org.jetbrains.kotlin.lexer.KtTokens
 import org.jetbrains.kotlin.lexer.KtTokens.MODALITY_MODIFIERS
 import org.jetbrains.kotlin.lexer.KtTokens.VISIBILITY_MODIFIERS
@@ -827,6 +826,40 @@ object LightTreePositioningStrategies {
         }
     }
 
+    val REDUNDANT_NULLABLE: LightTreePositioningStrategy = object : LightTreePositioningStrategy() {
+        override fun mark(
+            node: LighterASTNode,
+            startOffset: Int,
+            endOffset: Int,
+            tree: FlyweightCapableTreeStructure<LighterASTNode>
+        ): List<TextRange> {
+            val ref = Ref<Array<LighterASTNode?>>()
+            var child: LighterASTNode? = node
+            var lastQuest: LighterASTNode? = null
+            var prevQuest: LighterASTNode? = null
+            var quest: LighterASTNode? = null
+            while (child != null) {
+                child = getNullableChild(tree, child, ref)
+                prevQuest = quest
+                quest = ref.get().elementAtOrNull(1)
+                if (lastQuest == null) {
+                    lastQuest = quest
+                }
+            }
+            return markRange(prevQuest ?: lastQuest ?: node, lastQuest ?: node, startOffset, endOffset, tree, node)
+        }
+
+        private fun getNullableChild(
+            tree: FlyweightCapableTreeStructure<LighterASTNode>,
+            node: LighterASTNode,
+            ref: Ref<Array<LighterASTNode?>>
+        ): LighterASTNode? {
+            tree.getChildren(node, ref)
+            val firstChild = ref.get().firstOrNull() ?: return null
+            return if (firstChild.tokenType != KtNodeTypes.NULLABLE_TYPE) null else firstChild
+        }
+    }
+
     val QUESTION_MARK_BY_TYPE: LightTreePositioningStrategy = object : LightTreePositioningStrategy() {
         override fun mark(
             node: LighterASTNode,
@@ -1154,6 +1187,7 @@ private fun FlyweightCapableTreeStructure<LighterASTNode>.referenceExpression(
     }
     return result
 }
+
 fun FlyweightCapableTreeStructure<LighterASTNode>.unwrapParenthesesLabelsAndAnnotations(node: LighterASTNode): LighterASTNode {
     var unwrapped = node
     while (true) {
diff --git a/compiler/frontend.common-psi/src/org/jetbrains/kotlin/diagnostics/PositioningStrategies.kt b/compiler/frontend.common-psi/src/org/jetbrains/kotlin/diagnostics/PositioningStrategies.kt
index 267a6061a4e..eaeb59a11b6 100644
--- a/compiler/frontend.common-psi/src/org/jetbrains/kotlin/diagnostics/PositioningStrategies.kt
+++ b/compiler/frontend.common-psi/src/org/jetbrains/kotlin/diagnostics/PositioningStrategies.kt
@@ -5,6 +5,7 @@
 
 package org.jetbrains.kotlin.diagnostics
 
+import com.intellij.lang.ASTNode
 import com.intellij.openapi.util.TextRange
 import com.intellij.psi.*
 import com.intellij.psi.tree.TokenSet
@@ -549,6 +550,30 @@ object PositioningStrategies {
             }
     }
 
+    @JvmField
+    val REDUNDANT_NULLABLE: PositioningStrategy<KtTypeReference> = object : PositioningStrategy<KtTypeReference>() {
+        override fun mark(element: KtTypeReference): List<TextRange> {
+            var typeElement = element.typeElement
+            var question: ASTNode? = null
+            var prevQuestion: ASTNode? = null
+            var lastQuestion: ASTNode? = null
+            while (typeElement is KtNullableType) {
+                prevQuestion = question
+                question = typeElement.questionMarkNode
+                if (lastQuestion == null) {
+                    lastQuestion = question
+                }
+                typeElement = typeElement.innerType
+            }
+
+            if (lastQuestion != null) {
+                return markRange((prevQuestion ?: lastQuestion).psi, lastQuestion.psi)
+            }
+
+            return super.mark(element)
+        }
+    }
+
     @JvmField
     val NULLABLE_TYPE: PositioningStrategy<KtNullableType> = object : PositioningStrategy<KtNullableType>() {
         override fun mark(element: KtNullableType): List<TextRange> {
diff --git a/compiler/frontend.common-psi/src/org/jetbrains/kotlin/diagnostics/SourceElementPositioningStrategies.kt b/compiler/frontend.common-psi/src/org/jetbrains/kotlin/diagnostics/SourceElementPositioningStrategies.kt
index 435cf8a8c82..85c60306e1c 100644
--- a/compiler/frontend.common-psi/src/org/jetbrains/kotlin/diagnostics/SourceElementPositioningStrategies.kt
+++ b/compiler/frontend.common-psi/src/org/jetbrains/kotlin/diagnostics/SourceElementPositioningStrategies.kt
@@ -248,6 +248,11 @@ object SourceElementPositioningStrategies {
         PositioningStrategies.NAME_IDENTIFIER
     )
 
+    val REDUNDANT_NULLABLE = SourceElementPositioningStrategy(
+        LightTreePositioningStrategies.REDUNDANT_NULLABLE,
+        PositioningStrategies.REDUNDANT_NULLABLE
+    )
+
     val QUESTION_MARK_BY_TYPE = SourceElementPositioningStrategy(
         LightTreePositioningStrategies.QUESTION_MARK_BY_TYPE,
         PositioningStrategies.QUESTION_MARK_BY_TYPE
diff --git a/compiler/testData/diagnostics/tests/ProjectionsInSupertypes.fir.kt b/compiler/testData/diagnostics/tests/ProjectionsInSupertypes.fir.kt
index f956ad2959f..dacb92af749 100644
--- a/compiler/testData/diagnostics/tests/ProjectionsInSupertypes.fir.kt
+++ b/compiler/testData/diagnostics/tests/ProjectionsInSupertypes.fir.kt
@@ -1,6 +1,7 @@
+// WITH_EXTENDED_CHECKERS
 interface A<T> {}
 interface B<T> {}
 interface C<T> {}
 interface D<T> {}
 
-interface Test : A<<!PROJECTION_IN_IMMEDIATE_ARGUMENT_TO_SUPERTYPE!>in<!> Int>, B<<!PROJECTION_IN_IMMEDIATE_ARGUMENT_TO_SUPERTYPE!>out<!> Int>, C<<!PROJECTION_IN_IMMEDIATE_ARGUMENT_TO_SUPERTYPE!>*<!>>??<!NULLABLE_SUPERTYPE!>?<!>, D<Int> {}
+interface Test : A<<!PROJECTION_IN_IMMEDIATE_ARGUMENT_TO_SUPERTYPE!>in<!> Int>, B<<!PROJECTION_IN_IMMEDIATE_ARGUMENT_TO_SUPERTYPE!>out<!> Int>, C<<!PROJECTION_IN_IMMEDIATE_ARGUMENT_TO_SUPERTYPE!>*<!>>?<!REDUNDANT_NULLABLE!>?<!NULLABLE_SUPERTYPE!>?<!><!>, D<Int> {}
diff --git a/compiler/testData/diagnostics/tests/cast/bare/RedundantNullable.fir.kt b/compiler/testData/diagnostics/tests/cast/bare/RedundantNullable.fir.kt
deleted file mode 100644
index 5fd96375718..00000000000
--- a/compiler/testData/diagnostics/tests/cast/bare/RedundantNullable.fir.kt
+++ /dev/null
@@ -1,4 +0,0 @@
-interface B<T>
-class G<T>: B<T>
-
-fun f(b: B<String>?) = b is G??
\ No newline at end of file
diff --git a/compiler/testData/diagnostics/tests/cast/bare/RedundantNullable.kt b/compiler/testData/diagnostics/tests/cast/bare/RedundantNullable.kt
index 4e526bada9b..116b7b48489 100644
--- a/compiler/testData/diagnostics/tests/cast/bare/RedundantNullable.kt
+++ b/compiler/testData/diagnostics/tests/cast/bare/RedundantNullable.kt
@@ -1,3 +1,5 @@
+// FIR_IDENTICAL
+// WITH_EXTENDED_CHECKERS
 interface B<T>
 class G<T>: B<T>
 
diff --git a/compiler/testData/diagnostics/tests/nullableTypes/baseWithNullableUpperBound.fir.kt b/compiler/testData/diagnostics/tests/nullableTypes/baseWithNullableUpperBound.fir.kt
deleted file mode 100644
index 1ae495cde52..00000000000
--- a/compiler/testData/diagnostics/tests/nullableTypes/baseWithNullableUpperBound.fir.kt
+++ /dev/null
@@ -1,13 +0,0 @@
-fun <NN: Any, NNN: NN> nonMisleadingNullable(
-        nn: NN?,
-        nnn: NNN?
-) {}
-
-fun <T, N: T, INDIRECT: N> misleadingNullableSimple(
-        t: T?,
-        t2: T?,
-        n: N?,
-        ind: INDIRECT?
-) {}
-
-fun <T> interactionWithRedundant(t: T??) {}
\ No newline at end of file
diff --git a/compiler/testData/diagnostics/tests/nullableTypes/baseWithNullableUpperBound.kt b/compiler/testData/diagnostics/tests/nullableTypes/baseWithNullableUpperBound.kt
index 2963bb3245d..6c76edae3f3 100644
--- a/compiler/testData/diagnostics/tests/nullableTypes/baseWithNullableUpperBound.kt
+++ b/compiler/testData/diagnostics/tests/nullableTypes/baseWithNullableUpperBound.kt
@@ -1,3 +1,5 @@
+// FIR_IDENTICAL
+// WITH_EXTENDED_CHECKERS
 fun <NN: Any, NNN: NN> nonMisleadingNullable(
         nn: NN?,
         nnn: NNN?
diff --git a/compiler/testData/diagnostics/tests/nullableTypes/redundantNullable.fir.kt b/compiler/testData/diagnostics/tests/nullableTypes/redundantNullable.fir.kt
index 509d372da7f..cd719de5d5a 100644
--- a/compiler/testData/diagnostics/tests/nullableTypes/redundantNullable.fir.kt
+++ b/compiler/testData/diagnostics/tests/nullableTypes/redundantNullable.fir.kt
@@ -1,9 +1,10 @@
+// WITH_EXTENDED_CHECKERS
 class Generic<T>
 
 fun redundantNullable(
-        i: Int??,
-        three: Int???,
-        gOut: Generic<Int>??,
-        gIn: Generic<Int??>
+        i: Int?<!REDUNDANT_NULLABLE!>?<!>,
+        three: Int?<!REDUNDANT_NULLABLE!>??<!>,
+        gOut: Generic<Int>?<!REDUNDANT_NULLABLE!>?<!>,
+        gIn: Generic<Int?<!REDUNDANT_NULLABLE!>?<!>>
 ) {
 }
\ No newline at end of file
diff --git a/compiler/testData/diagnostics/tests/nullableTypes/redundantNullableInSupertype.fir.kt b/compiler/testData/diagnostics/tests/nullableTypes/redundantNullableInSupertype.fir.kt
index c227badcfe7..4bcbfe054d6 100644
--- a/compiler/testData/diagnostics/tests/nullableTypes/redundantNullableInSupertype.fir.kt
+++ b/compiler/testData/diagnostics/tests/nullableTypes/redundantNullableInSupertype.fir.kt
@@ -1,9 +1,10 @@
+// WITH_EXTENDED_CHECKERS
 interface A
-interface X: A?<!NULLABLE_SUPERTYPE!>?<!> {
+interface X: A?<!NULLABLE_SUPERTYPE, REDUNDANT_NULLABLE!>?<!> {
 
 }
 
 fun <T> interaction(t: T) {
     if (t == null) {}
 
-}
\ No newline at end of file
+}
diff --git a/compiler/testData/diagnostics/tests/typealias/kt15734.fir.kt b/compiler/testData/diagnostics/tests/typealias/kt15734.fir.kt
deleted file mode 100644
index 4f4b986100a..00000000000
--- a/compiler/testData/diagnostics/tests/typealias/kt15734.fir.kt
+++ /dev/null
@@ -1,19 +0,0 @@
-@Target(AnnotationTarget.TYPE)
-annotation class Ann
-
-typealias TString = String
-
-typealias TNString = TString?
-
-typealias TNAString = @Ann TString?
-
-val test1: TNString = TODO()
-val test2: TNAString = TODO()
-val test3: List<TNString> = TODO()
-val test4: List<TNAString> = TODO()
-val test5: List<TNString?> = TODO()
-val test6: () -> List<TNString> = TODO()
-
-fun test(x: TNString) {
-    x<!UNSAFE_CALL!>.<!>hashCode()
-}
diff --git a/compiler/testData/diagnostics/tests/typealias/kt15734.kt b/compiler/testData/diagnostics/tests/typealias/kt15734.kt
index 74de957e9cc..0cf7b30e1cc 100644
--- a/compiler/testData/diagnostics/tests/typealias/kt15734.kt
+++ b/compiler/testData/diagnostics/tests/typealias/kt15734.kt
@@ -1,3 +1,5 @@
+// FIR_IDENTICAL
+// WITH_EXTENDED_CHECKERS
 @Target(AnnotationTarget.TYPE)
 annotation class Ann
 
diff --git a/compiler/tests-spec/testData/diagnostics/notLinked/dfa/neg/1.fir.kt b/compiler/tests-spec/testData/diagnostics/notLinked/dfa/neg/1.fir.kt
index 428c2b20023..1bb1e638156 100644
--- a/compiler/tests-spec/testData/diagnostics/notLinked/dfa/neg/1.fir.kt
+++ b/compiler/tests-spec/testData/diagnostics/notLinked/dfa/neg/1.fir.kt
@@ -1,6 +1,7 @@
 // !LANGUAGE: +NewInference
-// !DIAGNOSTICS: -UNUSED_EXPRESSION
+// !DIAGNOSTICS: -UNUSED_EXPRESSION -UNUSED_VARIABLE
 // SKIP_TXT
+// WITH_EXTENDED_CHECKERS
 
 // TESTCASE NUMBER: 1
 fun case_1(x: Any?) {
@@ -108,7 +109,7 @@ fun case_8(x: TypealiasNullableString) {
 }
 
 // TESTCASE NUMBER: 9
-fun case_9(x: TypealiasNullableString?) {
+fun case_9(x: TypealiasNullableString<!REDUNDANT_NULLABLE!>?<!>) {
     if (<!SENSELESS_COMPARISON!>x === null === null<!>) {
 
     } else if (<!USELESS_IS_CHECK!>false is Boolean<!>) {
@@ -138,7 +139,7 @@ fun case_10() {
 }
 
 // TESTCASE NUMBER: 11
-fun case_11(x: TypealiasNullableStringIndirect?, y: TypealiasNullableStringIndirect) {
+fun case_11(x: TypealiasNullableStringIndirect<!REDUNDANT_NULLABLE!>?<!>, y: TypealiasNullableStringIndirect) {
     val t: TypealiasNullableStringIndirect = null
 
     if (<!EQUALITY_NOT_APPLICABLE!>x == null is Boolean<!>) {
diff --git a/compiler/tests-spec/testData/diagnostics/notLinked/dfa/neg/3.fir.kt b/compiler/tests-spec/testData/diagnostics/notLinked/dfa/neg/3.fir.kt
index 29fbca7e1d6..ec3aad782b7 100644
--- a/compiler/tests-spec/testData/diagnostics/notLinked/dfa/neg/3.fir.kt
+++ b/compiler/tests-spec/testData/diagnostics/notLinked/dfa/neg/3.fir.kt
@@ -1,6 +1,7 @@
 // !LANGUAGE: +NewInference
-// !DIAGNOSTICS: -UNUSED_EXPRESSION
+// !DIAGNOSTICS: -UNUSED_EXPRESSION -UNREACHABLE_CODE
 // SKIP_TXT
+// WITH_EXTENDED_CHECKERS
 
 // TESTCASE NUMBER: 1
 fun case_1(x: Nothing?) {
@@ -68,7 +69,7 @@ fun case_8(x: Nothing?) {
 
 // TESTCASE NUMBER: 9
 fun case_9(x: Nothing?) {
-    if (!!(<!USELESS_IS_CHECK!>x !is TypealiasNullableStringIndirect?<!>)) else {
+    if (!!(<!USELESS_IS_CHECK!>x !is TypealiasNullableStringIndirect<!REDUNDANT_NULLABLE!>?<!><!>)) else {
         <!DEBUG_INFO_EXPRESSION_TYPE("kotlin.Nothing?")!>x<!>
         <!DEBUG_INFO_EXPRESSION_TYPE("kotlin.Nothing?")!>x<!>?.<!UNRESOLVED_REFERENCE!>length<!>
     }
diff --git a/compiler/tests-spec/testData/diagnostics/notLinked/dfa/neg/6.fir.kt b/compiler/tests-spec/testData/diagnostics/notLinked/dfa/neg/6.fir.kt
index 21c3b6ef2d7..cd02158b2a5 100644
--- a/compiler/tests-spec/testData/diagnostics/notLinked/dfa/neg/6.fir.kt
+++ b/compiler/tests-spec/testData/diagnostics/notLinked/dfa/neg/6.fir.kt
@@ -1,6 +1,7 @@
 // !LANGUAGE: +NewInference
 // !DIAGNOSTICS: -UNUSED_EXPRESSION
 // SKIP_TXT
+// WITH_EXTENDED_CHECKERS
 
 // TESTCASE NUMBER: 1
 fun case_1(x: Any?) {
@@ -70,8 +71,8 @@ fun case_8(x: Any?) {
 
 // TESTCASE NUMBER: 9
 fun case_9(x: Any?) {
-    if (!!!(x !is TypealiasNullableStringIndirect?)) else {
-        if (!(x !is TypealiasNullableStringIndirect?)) else {
+    if (!!!(x !is TypealiasNullableStringIndirect<!REDUNDANT_NULLABLE!>?<!>)) else {
+        if (!(x !is TypealiasNullableStringIndirect<!REDUNDANT_NULLABLE!>?<!>)) else {
             <!DEBUG_INFO_EXPRESSION_TYPE("kotlin.Any?")!>x<!>
             <!DEBUG_INFO_EXPRESSION_TYPE("kotlin.Any?")!>x<!>?.<!UNRESOLVED_REFERENCE!>get<!>(0)
         }
diff --git a/compiler/tests-spec/testData/diagnostics/notLinked/dfa/pos/1.fir.kt b/compiler/tests-spec/testData/diagnostics/notLinked/dfa/pos/1.fir.kt
index a998c86a7e3..2a9abd746f8 100644
--- a/compiler/tests-spec/testData/diagnostics/notLinked/dfa/pos/1.fir.kt
+++ b/compiler/tests-spec/testData/diagnostics/notLinked/dfa/pos/1.fir.kt
@@ -1,6 +1,7 @@
 // !LANGUAGE: +NewInference
 // !DIAGNOSTICS: -UNUSED_EXPRESSION
 // SKIP_TXT
+// TODO: https://youtrack.jetbrains.com/issue/KT-49862
 
 /*
  * KOTLIN DIAGNOSTICS NOT LINKED SPEC TEST (POSITIVE)
diff --git a/compiler/tests-spec/testData/diagnostics/notLinked/dfa/pos/19.fir.kt b/compiler/tests-spec/testData/diagnostics/notLinked/dfa/pos/19.fir.kt
index 843dd80e246..35a9c2640f8 100644
--- a/compiler/tests-spec/testData/diagnostics/notLinked/dfa/pos/19.fir.kt
+++ b/compiler/tests-spec/testData/diagnostics/notLinked/dfa/pos/19.fir.kt
@@ -1,6 +1,7 @@
 // !LANGUAGE: +NewInference
 // !DIAGNOSTICS: -UNUSED_EXPRESSION
 // SKIP_TXT
+// WITH_EXTENDED_CHECKERS
 
 // TESTCASE NUMBER: 1
 fun case_1(x: Any?) {
@@ -68,7 +69,7 @@ fun case_8(x: Any?) {
 
 // TESTCASE NUMBER: 9
 fun case_9(x: Any?) {
-    if (!!(x !is TypealiasNullableStringIndirect?)) else {
+    if (!!(x !is TypealiasNullableStringIndirect<!REDUNDANT_NULLABLE!>?<!>)) else {
         <!DEBUG_INFO_EXPRESSION_TYPE("kotlin.Any? & TypealiasNullableStringIndirect?")!>x<!>
         <!DEBUG_INFO_EXPRESSION_TYPE("kotlin.Any? & TypealiasNullableStringIndirect?")!>x<!>?.get(0)
     }
diff --git a/compiler/tests-spec/testData/diagnostics/notLinked/dfa/pos/20.fir.kt b/compiler/tests-spec/testData/diagnostics/notLinked/dfa/pos/20.fir.kt
index cb180f380c0..9ca2c17f53e 100644
--- a/compiler/tests-spec/testData/diagnostics/notLinked/dfa/pos/20.fir.kt
+++ b/compiler/tests-spec/testData/diagnostics/notLinked/dfa/pos/20.fir.kt
@@ -1,6 +1,7 @@
 // !LANGUAGE: +NewInference
 // !DIAGNOSTICS: -UNUSED_EXPRESSION
 // SKIP_TXT
+// WITH_EXTENDED_CHECKERS
 
 // TESTCASE NUMBER: 1
 fun case_1(x: Any?) {
@@ -80,7 +81,7 @@ fun case_8(x: Any?) {
  * ISSUES: KT-28329
  */
 fun case_9(x: Any?) {
-    if (true && true && !!(x !is TypealiasNullableStringIndirect?) && true && true && true && true) else {
+    if (true && true && !!(x !is TypealiasNullableStringIndirect<!REDUNDANT_NULLABLE!>?<!>) && true && true && true && true) else {
         <!DEBUG_INFO_EXPRESSION_TYPE("kotlin.Any?")!>x<!>
         <!DEBUG_INFO_EXPRESSION_TYPE("kotlin.Any?")!>x<!>?.<!UNRESOLVED_REFERENCE!>get<!>(0)
     }
diff --git a/compiler/tests-spec/testData/diagnostics/notLinked/dfa/pos/21.fir.kt b/compiler/tests-spec/testData/diagnostics/notLinked/dfa/pos/21.fir.kt
index ba97a374d81..c3c827abd37 100644
--- a/compiler/tests-spec/testData/diagnostics/notLinked/dfa/pos/21.fir.kt
+++ b/compiler/tests-spec/testData/diagnostics/notLinked/dfa/pos/21.fir.kt
@@ -1,6 +1,7 @@
 // !LANGUAGE: +NewInference
 // !DIAGNOSTICS: -UNUSED_EXPRESSION
 // SKIP_TXT
+// WITH_EXTENDED_CHECKERS
 
 // TESTCASE NUMBER: 1
 fun case_1(x: Any?) {
@@ -84,7 +85,7 @@ fun case_8(x: Any?) {
  * ISSUES: KT-28329
  */
 fun case_9(x: Any?) {
-    if (!!(x !is TypealiasNullableStringIndirect?) !== false === true) else {
+    if (!!(x !is TypealiasNullableStringIndirect<!REDUNDANT_NULLABLE!>?<!>) !== false === true) else {
         <!DEBUG_INFO_EXPRESSION_TYPE("kotlin.Any? & TypealiasNullableStringIndirect?")!>x<!>
         <!DEBUG_INFO_EXPRESSION_TYPE("kotlin.Any? & TypealiasNullableStringIndirect?")!>x<!>?.get(0)
     }
diff --git a/compiler/tests-spec/testData/diagnostics/notLinked/dfa/pos/22.fir.kt b/compiler/tests-spec/testData/diagnostics/notLinked/dfa/pos/22.fir.kt
index 55bad8b0f55..e88a7290a60 100644
--- a/compiler/tests-spec/testData/diagnostics/notLinked/dfa/pos/22.fir.kt
+++ b/compiler/tests-spec/testData/diagnostics/notLinked/dfa/pos/22.fir.kt
@@ -1,6 +1,7 @@
 // !LANGUAGE: +NewInference
 // !DIAGNOSTICS: -UNUSED_EXPRESSION
 // SKIP_TXT
+// WITH_EXTENDED_CHECKERS
 
 // TESTCASE NUMBER: 1
 fun case_1(x: Any?) {
@@ -84,8 +85,8 @@ fun case_8(x: Any?) {
 
 // TESTCASE NUMBER: 9
 fun case_9(x: Any?) {
-    if (!!!(x !is TypealiasNullableStringIndirect?)) else {
-        if (!!(x !is TypealiasNullableStringIndirect?)) else {
+    if (!!!(x !is TypealiasNullableStringIndirect<!REDUNDANT_NULLABLE!>?<!>)) else {
+        if (!!(x !is TypealiasNullableStringIndirect<!REDUNDANT_NULLABLE!>?<!>)) else {
             <!DEBUG_INFO_EXPRESSION_TYPE("kotlin.Any? & TypealiasNullableStringIndirect?")!>x<!>
             <!DEBUG_INFO_EXPRESSION_TYPE("kotlin.Any? & TypealiasNullableStringIndirect?")!>x<!>?.get(0)
         }
diff --git a/compiler/tests-spec/testData/diagnostics/notLinked/dfa/pos/3.fir.kt b/compiler/tests-spec/testData/diagnostics/notLinked/dfa/pos/3.fir.kt
index f2cde2ca2cd..9b12e7cf7ff 100644
--- a/compiler/tests-spec/testData/diagnostics/notLinked/dfa/pos/3.fir.kt
+++ b/compiler/tests-spec/testData/diagnostics/notLinked/dfa/pos/3.fir.kt
@@ -1,6 +1,7 @@
 // !LANGUAGE: +NewInference
-// !DIAGNOSTICS: -UNUSED_EXPRESSION
+// !DIAGNOSTICS: -UNUSED_EXPRESSION -UNUSED_VARIABLE
 // SKIP_TXT
+// WITH_EXTENDED_CHECKERS
 
 // FILE: other_package.kt
 
@@ -76,7 +77,7 @@ fun case_8(x: TypealiasNullableString) {
  * UNEXPECTED BEHAVIOUR
  * ISSUES: KT-28329
  */
-fun case_9(x: TypealiasNullableString?) {
+fun case_9(x: TypealiasNullableString<!REDUNDANT_NULLABLE!>?<!>) {
     if (true && true && true && true && x !== null) {
 
     } else if (false) {
@@ -96,7 +97,7 @@ fun case_10() {
 }
 
 // TESTCASE NUMBER: 11
-fun case_11(x: TypealiasNullableString?, y: TypealiasNullableString) {
+fun case_11(x: TypealiasNullableString<!REDUNDANT_NULLABLE!>?<!>, y: TypealiasNullableString) {
     val z: TypealiasNullableString = null
 
     if (x != null) {
diff --git a/compiler/tests-spec/testData/diagnostics/notLinked/dfa/pos/6.fir.kt b/compiler/tests-spec/testData/diagnostics/notLinked/dfa/pos/6.fir.kt
index 34217d16672..dbaa694dcef 100644
--- a/compiler/tests-spec/testData/diagnostics/notLinked/dfa/pos/6.fir.kt
+++ b/compiler/tests-spec/testData/diagnostics/notLinked/dfa/pos/6.fir.kt
@@ -1,7 +1,8 @@
 // FIR_IGNORE
 // !LANGUAGE: +NewInference
-// !DIAGNOSTICS: -UNUSED_EXPRESSION
+// !DIAGNOSTICS: -UNUSED_EXPRESSION -UNUSED_VARIABLE -UNREACHABLE_CODE -CAN_BE_VAL
 // SKIP_TXT
+// WITH_EXTENDED_CHECKERS
 
 // FILE: other_types.kt
 
@@ -153,7 +154,7 @@ fun case_8(x: TypealiasNullableString) {
 }
 
 // TESTCASE NUMBER: 9
-fun case_9(x: TypealiasNullableString?, y: Nothing?) {
+fun case_9(x: TypealiasNullableString<!REDUNDANT_NULLABLE!>?<!>, y: Nothing?) {
     if (x === y) {
 
     } else if (false) {
@@ -192,7 +193,7 @@ fun case_10() {
 }
 
 // TESTCASE NUMBER: 11
-fun case_11(x: TypealiasNullableString?, y: TypealiasNullableString) {
+fun case_11(x: TypealiasNullableString<!REDUNDANT_NULLABLE!>?<!>, y: TypealiasNullableString) {
     val z = null
     val u: TypealiasNullableString = null
     val v = null
@@ -253,7 +254,7 @@ fun case_13(x: EmptyClass12_48?, z: Nothing?) =
 
 // TESTCASE NUMBER: 14
 class Case14 {
-    val x: TypealiasNullableString?
+    val x: TypealiasNullableString<!REDUNDANT_NULLABLE!>?<!>
     init {
         x = TypealiasNullableString()
     }
@@ -800,7 +801,7 @@ fun case_43(x: TypealiasNullableString) {
  * UNEXPECTED BEHAVIOUR
  * ISSUES: KT-28329
  */
-fun case_44(x: TypealiasNullableString?, z1: Nothing?) {
+fun case_44(x: TypealiasNullableString<!REDUNDANT_NULLABLE!>?<!>, z1: Nothing?) {
     if (true && true && true && true && x !== z1) {
 
     } else if (false) {
@@ -831,7 +832,7 @@ fun case_45() {
 }
 
 // TESTCASE NUMBER: 46
-fun case_46(x: TypealiasNullableString?, y: TypealiasNullableString) {
+fun case_46(x: TypealiasNullableString<!REDUNDANT_NULLABLE!>?<!>, y: TypealiasNullableString) {
     val t: TypealiasNullableString = null
     var z: Nothing? = null
 
@@ -879,7 +880,7 @@ fun case_48(x: EmptyClass12_48?, z: Nothing?) =
 
 // TESTCASE NUMBER: 49
 class Case49 {
-    val x: TypealiasNullableString?
+    val x: TypealiasNullableString<!REDUNDANT_NULLABLE!>?<!>
     init {
         x = TypealiasNullableString()
     }
diff --git a/compiler/tests-spec/testData/diagnostics/notLinked/dfa/pos/7.fir.kt b/compiler/tests-spec/testData/diagnostics/notLinked/dfa/pos/7.fir.kt
index 0fb144585f9..fbf882919f7 100644
--- a/compiler/tests-spec/testData/diagnostics/notLinked/dfa/pos/7.fir.kt
+++ b/compiler/tests-spec/testData/diagnostics/notLinked/dfa/pos/7.fir.kt
@@ -1,6 +1,7 @@
 // !LANGUAGE: +NewInference
-// !DIAGNOSTICS: -UNUSED_EXPRESSION
+// !DIAGNOSTICS: -UNUSED_EXPRESSION -UNUSED_VARIABLE -UNREACHABLE_CODE -CAN_BE_VAL
 // SKIP_TXT
+// WITH_EXTENDED_CHECKERS
 
 // FILE: other_package.kt
 
@@ -146,7 +147,7 @@ fun case_8(x: TypealiasString) {
 }
 
 // TESTCASE NUMBER: 9
-fun case_9(x: TypealiasNullableString?) {
+fun case_9(x: TypealiasNullableString<!REDUNDANT_NULLABLE!>?<!>) {
     if (x === null && <!SENSELESS_COMPARISON!>x === null<!> || <!SENSELESS_COMPARISON!>x === null<!>) {
 
     } else if (<!SENSELESS_COMPARISON!>x === null<!> || <!SENSELESS_COMPARISON!>x === null<!>) {
@@ -185,7 +186,7 @@ fun case_10() {
 }
 
 // TESTCASE NUMBER: 11
-fun case_11(x: TypealiasNullableString?, y: TypealiasNullableString) {
+fun case_11(x: TypealiasNullableString<!REDUNDANT_NULLABLE!>?<!>, y: TypealiasNullableString) {
     val t: TypealiasNullableString = null
 
     if (x == null) {