diff --git a/compiler/frontend/src/org/jetbrains/kotlin/diagnostics/Errors.java b/compiler/frontend/src/org/jetbrains/kotlin/diagnostics/Errors.java
index 09c51ce0fee..a20ebdf8df2 100644
--- a/compiler/frontend/src/org/jetbrains/kotlin/diagnostics/Errors.java
+++ b/compiler/frontend/src/org/jetbrains/kotlin/diagnostics/Errors.java
@@ -80,6 +80,13 @@ public interface Errors {
     DiagnosticFactory1<PsiElement, String> PACKAGE_OR_CLASSIFIER_REDECLARATION =
             DiagnosticFactory1.create(ERROR, FOR_REDECLARATION);
 
+    DiagnosticFactory1<KtDeclaration, CallableMemberDescriptor> EXTENSION_SHADOWED_BY_MEMBER =
+            DiagnosticFactory1.create(WARNING, FOR_REDECLARATION);
+    DiagnosticFactory1<KtDeclaration, ConstructorDescriptor> EXTENSION_FUNCTION_SHADOWED_BY_INNER_CLASS_CONSTRUCTOR =
+            DiagnosticFactory1.create(WARNING, FOR_REDECLARATION);
+    DiagnosticFactory2<KtDeclaration, PropertyDescriptor, FunctionDescriptor> EXTENSION_FUNCTION_SHADOWED_BY_MEMBER_PROPERTY_WITH_INVOKE =
+            DiagnosticFactory2.create(WARNING, FOR_REDECLARATION);
+
     DiagnosticFactory1<KtReferenceExpression, KtReferenceExpression> UNRESOLVED_REFERENCE =
             DiagnosticFactory1.create(ERROR, FOR_UNRESOLVED_REFERENCE);
 
diff --git a/compiler/frontend/src/org/jetbrains/kotlin/diagnostics/rendering/DefaultErrorMessages.java b/compiler/frontend/src/org/jetbrains/kotlin/diagnostics/rendering/DefaultErrorMessages.java
index 1b608538b64..ae79a11a113 100644
--- a/compiler/frontend/src/org/jetbrains/kotlin/diagnostics/rendering/DefaultErrorMessages.java
+++ b/compiler/frontend/src/org/jetbrains/kotlin/diagnostics/rendering/DefaultErrorMessages.java
@@ -114,6 +114,12 @@ public class DefaultErrorMessages {
         MAP.put(EXPOSED_SUPER_INTERFACE, "''{0}'' sub-interface exposes its ''{2}'' supertype{1}", TO_STRING, TO_STRING, TO_STRING);
         MAP.put(EXPOSED_TYPEALIAS_EXPANDED_TYPE, "''{0}'' typealias exposes ''{2}'' in expanded type{1}", TO_STRING, TO_STRING, TO_STRING);
 
+        MAP.put(EXTENSION_SHADOWED_BY_MEMBER, "Extension is shadowed by a member: {0}", COMPACT_WITH_MODIFIERS);
+        MAP.put(EXTENSION_FUNCTION_SHADOWED_BY_INNER_CLASS_CONSTRUCTOR,
+                "Extension function is shadowed by an inner class constructor: {0}", COMPACT_WITH_MODIFIERS);
+        MAP.put(EXTENSION_FUNCTION_SHADOWED_BY_MEMBER_PROPERTY_WITH_INVOKE,
+                "Extension function is shadowed by a member property ''{0}'' with {1}", NAME, COMPACT_WITH_MODIFIERS);
+
         MAP.put(INACCESSIBLE_TYPE, "Type {0} is inaccessible in this context due to: {1}", RENDER_TYPE, commaSeparated(FQ_NAMES_IN_TYPES));
 
         MAP.put(REDECLARATION, "Conflicting declarations: {0}", commaSeparated(COMPACT_WITH_MODIFIERS));
diff --git a/compiler/frontend/src/org/jetbrains/kotlin/resolve/DeclarationResolver.kt b/compiler/frontend/src/org/jetbrains/kotlin/resolve/DeclarationResolver.kt
index acd84bcff27..ebe4d729529 100644
--- a/compiler/frontend/src/org/jetbrains/kotlin/resolve/DeclarationResolver.kt
+++ b/compiler/frontend/src/org/jetbrains/kotlin/resolve/DeclarationResolver.kt
@@ -80,7 +80,7 @@ class DeclarationResolver(
 
             // TODO: report error on header class and impl val, or vice versa
             val (header, impl) =
-                    getTopLevelDescriptorsByFqName(topLevelDescriptorProvider, fqName, NoLookupLocation.WHEN_CHECK_REDECLARATIONS)
+                    getTopLevelDescriptorsByFqName(topLevelDescriptorProvider, fqName, NoLookupLocation.WHEN_CHECK_DECLARATION_CONFLICTS)
                     .partition { it is MemberDescriptor && it.isHeader }
 
             for (descriptors in listOf(header, impl)) {
diff --git a/compiler/frontend/src/org/jetbrains/kotlin/resolve/DeclarationsChecker.kt b/compiler/frontend/src/org/jetbrains/kotlin/resolve/DeclarationsChecker.kt
index e16479a39f9..e6815327a82 100644
--- a/compiler/frontend/src/org/jetbrains/kotlin/resolve/DeclarationsChecker.kt
+++ b/compiler/frontend/src/org/jetbrains/kotlin/resolve/DeclarationsChecker.kt
@@ -33,6 +33,7 @@ import org.jetbrains.kotlin.psi.psiUtil.visibilityModifier
 import org.jetbrains.kotlin.resolve.BindingContext.*
 import org.jetbrains.kotlin.resolve.DescriptorUtils.classCanHaveAbstractMembers
 import org.jetbrains.kotlin.resolve.DescriptorUtils.classCanHaveOpenMembers
+import org.jetbrains.kotlin.resolve.calls.results.TypeSpecificityComparator
 import org.jetbrains.kotlin.resolve.source.KotlinSourceElement
 import org.jetbrains.kotlin.types.*
 import org.jetbrains.kotlin.types.checker.KotlinTypeChecker
@@ -45,10 +46,11 @@ internal class DeclarationsCheckerBuilder(
         private val originalModifiersChecker: ModifiersChecker,
         private val annotationChecker: AnnotationChecker,
         private val identifierChecker: IdentifierChecker,
-        private val languageVersionSettings: LanguageVersionSettings
+        private val languageVersionSettings: LanguageVersionSettings,
+        private val typeSpecificityComparator: TypeSpecificityComparator
 ) {
     fun withTrace(trace: BindingTrace) =
-            DeclarationsChecker(descriptorResolver, originalModifiersChecker, annotationChecker, identifierChecker, trace, languageVersionSettings)
+            DeclarationsChecker(descriptorResolver, originalModifiersChecker, annotationChecker, identifierChecker, trace, languageVersionSettings, typeSpecificityComparator)
 }
 
 class DeclarationsChecker(
@@ -57,13 +59,16 @@ class DeclarationsChecker(
         private val annotationChecker: AnnotationChecker,
         private val identifierChecker: IdentifierChecker,
         private val trace: BindingTrace,
-        private val languageVersionSettings: LanguageVersionSettings
+        private val languageVersionSettings: LanguageVersionSettings,
+        typeSpecificityComparator: TypeSpecificityComparator
 ) {
 
     private val modifiersChecker = modifiersChecker.withTrace(trace)
 
     private val exposedChecker = ExposedVisibilityChecker(trace)
 
+    private val shadowedExtensionChecker = ShadowedExtensionChecker(typeSpecificityComparator, trace)
+
     fun process(bodiesResolveContext: BodiesResolveContext) {
         for (file in bodiesResolveContext.files) {
             checkModifiersAndAnnotationsInPackageDirective(file)
@@ -524,6 +529,7 @@ class DeclarationsChecker(
         checkAccessors(property, propertyDescriptor)
         checkTypeParameterConstraints(property)
         exposedChecker.checkProperty(property, propertyDescriptor)
+        shadowedExtensionChecker.checkDeclaration(property, propertyDescriptor)
         checkPropertyTypeParametersAreUsedInReceiverType(propertyDescriptor)
         checkImplicitCallableType(property, propertyDescriptor)
     }
@@ -766,6 +772,8 @@ class DeclarationsChecker(
         if (functionDescriptor.isHeader) {
             checkHeaderFunction(function)
         }
+
+        shadowedExtensionChecker.checkDeclaration(function, functionDescriptor)
     }
 
     private fun checkHeaderFunction(function: KtNamedFunction) {
diff --git a/compiler/frontend/src/org/jetbrains/kotlin/resolve/OverloadChecker.kt b/compiler/frontend/src/org/jetbrains/kotlin/resolve/OverloadChecker.kt
index e69a8738b54..a8c414bfeb8 100644
--- a/compiler/frontend/src/org/jetbrains/kotlin/resolve/OverloadChecker.kt
+++ b/compiler/frontend/src/org/jetbrains/kotlin/resolve/OverloadChecker.kt
@@ -16,25 +16,22 @@
 
 package org.jetbrains.kotlin.resolve
 
-import com.intellij.util.containers.MultiMap
 import org.jetbrains.kotlin.descriptors.*
-import org.jetbrains.kotlin.incremental.components.NoLookupLocation
-import org.jetbrains.kotlin.name.FqNameUnsafe
-import org.jetbrains.kotlin.name.Name
 import org.jetbrains.kotlin.resolve.calls.inference.ConstraintSystemBuilderImpl
 import org.jetbrains.kotlin.resolve.calls.results.FlatSignature
 import org.jetbrains.kotlin.resolve.calls.results.SpecificityComparisonCallbacks
 import org.jetbrains.kotlin.resolve.calls.results.TypeSpecificityComparator
 import org.jetbrains.kotlin.resolve.calls.results.isSignatureNotLessSpecific
-import org.jetbrains.kotlin.resolve.calls.tower.getTypeAliasConstructors
 import org.jetbrains.kotlin.resolve.descriptorUtil.hasLowPriorityInOverloadResolution
-import org.jetbrains.kotlin.resolve.descriptorUtil.varargParameterPosition
 import org.jetbrains.kotlin.resolve.descriptorUtil.isExtensionProperty
-import org.jetbrains.kotlin.resolve.scopes.MemberScope
+import org.jetbrains.kotlin.resolve.descriptorUtil.varargParameterPosition
 import org.jetbrains.kotlin.types.ErrorUtils
 import org.jetbrains.kotlin.types.KotlinType
-import org.jetbrains.kotlin.utils.singletonOrEmptyList
-import java.util.*
+
+object OverloadabilitySpecificityCallbacks : SpecificityComparisonCallbacks {
+    override fun isNonSubtypeNotLessSpecific(specific: KotlinType, general: KotlinType): Boolean =
+            false
+}
 
 class OverloadChecker(val specificityComparator: TypeSpecificityComparator) {
     /**
@@ -50,11 +47,6 @@ class OverloadChecker(val specificityComparator: TypeSpecificityComparator) {
         return checkOverloadability(a, b)
     }
 
-    private object OverloadabilitySpecificityCallbacks : SpecificityComparisonCallbacks {
-        override fun isNonSubtypeNotLessSpecific(specific: KotlinType, general: KotlinType): Boolean =
-                false
-    }
-
     private fun checkOverloadability(a: CallableDescriptor, b: CallableDescriptor): Boolean {
         if (a.hasLowPriorityInOverloadResolution() != b.hasLowPriorityInOverloadResolution()) return true
 
@@ -69,7 +61,7 @@ class OverloadChecker(val specificityComparator: TypeSpecificityComparator) {
         val aSignature = FlatSignature.createFromCallableDescriptor(a)
         val bSignature = FlatSignature.createFromCallableDescriptor(b)
 
-        val aIsNotLessSpecificThanB = ConstraintSystemBuilderImpl.forSpecificity().isSignatureNotLessSpecific (aSignature, bSignature, OverloadabilitySpecificityCallbacks, specificityComparator)
+        val aIsNotLessSpecificThanB = ConstraintSystemBuilderImpl.forSpecificity().isSignatureNotLessSpecific(aSignature, bSignature, OverloadabilitySpecificityCallbacks, specificityComparator)
         val bIsNotLessSpecificThanA = ConstraintSystemBuilderImpl.forSpecificity().isSignatureNotLessSpecific(bSignature, aSignature, OverloadabilitySpecificityCallbacks, specificityComparator)
 
         return !(aIsNotLessSpecificThanB && bIsNotLessSpecificThanA)
diff --git a/compiler/frontend/src/org/jetbrains/kotlin/resolve/OverloadResolver.kt b/compiler/frontend/src/org/jetbrains/kotlin/resolve/OverloadResolver.kt
index 443c3c4e291..d33bcb3a087 100644
--- a/compiler/frontend/src/org/jetbrains/kotlin/resolve/OverloadResolver.kt
+++ b/compiler/frontend/src/org/jetbrains/kotlin/resolve/OverloadResolver.kt
@@ -96,8 +96,8 @@ class OverloadResolver(
                 overloadFilter
         ) {
             scope, name ->
-            val functions = scope.getContributedFunctions(name, NoLookupLocation.WHEN_CHECK_REDECLARATIONS)
-            val classifier = scope.getContributedClassifier(name, NoLookupLocation.WHEN_CHECK_REDECLARATIONS)
+            val functions = scope.getContributedFunctions(name, NoLookupLocation.WHEN_CHECK_DECLARATION_CONFLICTS)
+            val classifier = scope.getContributedClassifier(name, NoLookupLocation.WHEN_CHECK_DECLARATION_CONFLICTS)
             when (classifier) {
                 is ClassDescriptor ->
                     if (!classifier.kind.isSingleton)
@@ -113,8 +113,8 @@ class OverloadResolver(
 
         collectModulePackageMembersWithSameName(packageMembersByName, c.properties.values, overloadFilter) {
             scope, name ->
-            val variables = scope.getContributedVariables(name, NoLookupLocation.WHEN_CHECK_REDECLARATIONS)
-            val classifier = scope.getContributedClassifier(name, NoLookupLocation.WHEN_CHECK_REDECLARATIONS)
+            val variables = scope.getContributedVariables(name, NoLookupLocation.WHEN_CHECK_DECLARATION_CONFLICTS)
+            val classifier = scope.getContributedClassifier(name, NoLookupLocation.WHEN_CHECK_DECLARATION_CONFLICTS)
             variables + classifier.singletonOrEmptyList()
         }
 
diff --git a/compiler/frontend/src/org/jetbrains/kotlin/resolve/ShadowedExtensionChecker.kt b/compiler/frontend/src/org/jetbrains/kotlin/resolve/ShadowedExtensionChecker.kt
new file mode 100644
index 00000000000..b9776c593b1
--- /dev/null
+++ b/compiler/frontend/src/org/jetbrains/kotlin/resolve/ShadowedExtensionChecker.kt
@@ -0,0 +1,122 @@
+/*
+ * Copyright 2010-2017 JetBrains s.r.o.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.jetbrains.kotlin.resolve
+
+import org.jetbrains.kotlin.descriptors.*
+import org.jetbrains.kotlin.diagnostics.DiagnosticSink
+import org.jetbrains.kotlin.diagnostics.Errors
+import org.jetbrains.kotlin.incremental.components.NoLookupLocation
+import org.jetbrains.kotlin.psi.KtDeclaration
+import org.jetbrains.kotlin.resolve.calls.inference.ConstraintSystemBuilderImpl
+import org.jetbrains.kotlin.resolve.calls.results.FlatSignature
+import org.jetbrains.kotlin.resolve.calls.results.TypeSpecificityComparator
+import org.jetbrains.kotlin.resolve.calls.results.isSignatureNotLessSpecific
+import org.jetbrains.kotlin.resolve.descriptorUtil.hasHidesMembersAnnotation
+import org.jetbrains.kotlin.resolve.descriptorUtil.isExtension
+import org.jetbrains.kotlin.resolve.descriptorUtil.varargParameterPosition
+import org.jetbrains.kotlin.util.OperatorNameConventions
+
+class ShadowedExtensionChecker(val typeSpecificityComparator: TypeSpecificityComparator, val trace: DiagnosticSink) {
+    fun checkDeclaration(declaration: KtDeclaration, descriptor: DeclarationDescriptor) {
+        if (declaration.name == null) return
+        if (descriptor !is CallableMemberDescriptor) return
+        if (descriptor.hasHidesMembersAnnotation()) return
+        val extensionReceiverType = descriptor.extensionReceiverParameter?.type ?: return
+        if (extensionReceiverType.isError) return
+        if (extensionReceiverType.isMarkedNullable) return
+
+        when (descriptor) {
+            is FunctionDescriptor ->
+                checkShadowedExtensionFunction(declaration, descriptor, trace)
+            is PropertyDescriptor ->
+                checkShadowedExtensionProperty(declaration, descriptor, trace)
+        }
+    }
+
+    private fun checkShadowedExtensionFunction(declaration: KtDeclaration, extensionFunction: FunctionDescriptor, trace: DiagnosticSink) {
+        val memberScope = extensionFunction.extensionReceiverParameter?.type?.memberScope ?: return
+
+        for (memberFunction in memberScope.getContributedFunctions(extensionFunction.name, NoLookupLocation.WHEN_CHECK_DECLARATION_CONFLICTS)) {
+            if (memberFunction.isPublic() && isExtensionFunctionShadowedByMemberFunction(extensionFunction, memberFunction)) {
+                trace.report(Errors.EXTENSION_SHADOWED_BY_MEMBER.on(declaration, memberFunction))
+                return
+            }
+        }
+
+        val nestedClass = memberScope.getContributedClassifier(extensionFunction.name, NoLookupLocation.WHEN_CHECK_DECLARATION_CONFLICTS)
+        if (nestedClass is ClassDescriptor && nestedClass.isInner && nestedClass.isPublic()) {
+            for (constructor in nestedClass.constructors) {
+                if (constructor.isPublic() && isExtensionFunctionShadowedByMemberFunction(extensionFunction, constructor)) {
+                    trace.report(Errors.EXTENSION_FUNCTION_SHADOWED_BY_INNER_CLASS_CONSTRUCTOR.on(declaration, constructor))
+                    return
+                }
+            }
+        }
+
+        for (memberProperty in memberScope.getContributedVariables(extensionFunction.name, NoLookupLocation.WHEN_CHECK_DECLARATION_CONFLICTS)) {
+            if (!memberProperty.isPublic()) continue
+
+            val invokeOperator = getInvokeOperatorShadowingExtensionFunction(extensionFunction, memberProperty)
+            if (invokeOperator != null) {
+                trace.report(Errors.EXTENSION_FUNCTION_SHADOWED_BY_MEMBER_PROPERTY_WITH_INVOKE.on(declaration, memberProperty, invokeOperator))
+                return
+            }
+        }
+    }
+
+    private fun DeclarationDescriptorWithVisibility.isPublic() =
+            visibility.normalize() == Visibilities.PUBLIC
+
+    private fun isExtensionFunctionShadowedByMemberFunction(extension: FunctionDescriptor, member: FunctionDescriptor): Boolean {
+        // Permissive check:
+        //      (1) functions should have same number of arguments;
+        //      (2) varargs should be in the same positions;
+        //      (3) extension signature should be not less specific than member signature.
+        // (1) & (2) are required so that we can match signatures easily.
+
+        if (extension.valueParameters.size != member.valueParameters.size) return false
+        if (extension.varargParameterPosition() != member.varargParameterPosition()) return false
+        if (extension.isOperator && !member.isOperator) return false
+
+        val extensionSignature = FlatSignature.createForPossiblyShadowedExtension(extension)
+        val memberSignature = FlatSignature.createFromCallableDescriptor(member)
+        return isSignatureNotLessSpecific(extensionSignature, memberSignature)
+    }
+
+    private fun getInvokeOperatorShadowingExtensionFunction(extension: FunctionDescriptor, member: PropertyDescriptor): FunctionDescriptor? =
+            member.type.memberScope.getContributedFunctions(OperatorNameConventions.INVOKE, NoLookupLocation.WHEN_CHECK_DECLARATION_CONFLICTS)
+                    .firstOrNull { it.isPublic() && it.isOperator && isExtensionFunctionShadowedByMemberFunction(extension, it) }
+
+    private fun isSignatureNotLessSpecific(extensionSignature: FlatSignature<FunctionDescriptor>, memberSignature: FlatSignature<FunctionDescriptor>): Boolean =
+            ConstraintSystemBuilderImpl.forSpecificity().isSignatureNotLessSpecific(
+                    extensionSignature,
+                    memberSignature,
+                    OverloadabilitySpecificityCallbacks,
+                    typeSpecificityComparator
+            )
+
+    private fun checkShadowedExtensionProperty(declaration: KtDeclaration, extensionProperty: PropertyDescriptor, trace: DiagnosticSink) {
+        val memberScope = extensionProperty.extensionReceiverParameter?.type?.memberScope ?: return
+
+        memberScope.getContributedVariables(extensionProperty.name, NoLookupLocation.WHEN_CHECK_DECLARATION_CONFLICTS)
+                .firstOrNull { it.isPublic() && !it.isExtension }
+                ?.let { memberProperty ->
+                    trace.report(Errors.EXTENSION_SHADOWED_BY_MEMBER.on(declaration, memberProperty))
+                }
+    }
+
+}
\ No newline at end of file
diff --git a/compiler/frontend/src/org/jetbrains/kotlin/resolve/scopes/LocalRedeclarationChecker.kt b/compiler/frontend/src/org/jetbrains/kotlin/resolve/scopes/LocalRedeclarationChecker.kt
index 02c50423539..20af1e574d0 100644
--- a/compiler/frontend/src/org/jetbrains/kotlin/resolve/scopes/LocalRedeclarationChecker.kt
+++ b/compiler/frontend/src/org/jetbrains/kotlin/resolve/scopes/LocalRedeclarationChecker.kt
@@ -32,7 +32,7 @@ import org.jetbrains.kotlin.resolve.OverloadChecker
 abstract class AbstractLocalRedeclarationChecker(val overloadChecker: OverloadChecker) : LocalRedeclarationChecker {
     override fun checkBeforeAddingToScope(scope: LexicalScope, newDescriptor: DeclarationDescriptor) {
         val name = newDescriptor.name
-        val location = NoLookupLocation.WHEN_CHECK_REDECLARATIONS
+        val location = NoLookupLocation.WHEN_CHECK_DECLARATION_CONFLICTS
         when (newDescriptor) {
             is ClassifierDescriptor, is VariableDescriptor -> {
                 val otherDescriptor = scope.getContributedClassifier(name, location)
diff --git a/compiler/resolution/src/org/jetbrains/kotlin/resolve/calls/results/FlatSignature.kt b/compiler/resolution/src/org/jetbrains/kotlin/resolve/calls/results/FlatSignature.kt
index ec366fc04ed..d858cd5f650 100644
--- a/compiler/resolution/src/org/jetbrains/kotlin/resolve/calls/results/FlatSignature.kt
+++ b/compiler/resolution/src/org/jetbrains/kotlin/resolve/calls/results/FlatSignature.kt
@@ -21,6 +21,7 @@ import org.jetbrains.kotlin.descriptors.MemberDescriptor
 import org.jetbrains.kotlin.descriptors.TypeParameterDescriptor
 import org.jetbrains.kotlin.descriptors.ValueParameterDescriptor
 import org.jetbrains.kotlin.descriptors.synthetic.SyntheticMemberDescriptor
+import org.jetbrains.kotlin.resolve.descriptorUtil.hasDefaultValue
 import org.jetbrains.kotlin.types.*
 import org.jetbrains.kotlin.types.checker.KotlinTypeChecker
 import org.jetbrains.kotlin.utils.singletonOrEmptyList
@@ -75,6 +76,17 @@ class FlatSignature<out T> private constructor(
         ): FlatSignature<D> =
                 create(descriptor, descriptor, numDefaults = 0, parameterTypes = descriptor.valueParameters.map { it.argumentValueType })
 
+        fun <D : CallableDescriptor> createForPossiblyShadowedExtension(descriptor: D): FlatSignature<D> =
+                FlatSignature(descriptor,
+                              descriptor.typeParameters,
+                              valueParameterTypes = descriptor.valueParameters.map { it.argumentValueType },
+                              hasExtensionReceiver = false,
+                              hasVarargs = descriptor.valueParameters.any { it.varargElementType != null },
+                              numDefaults = descriptor.valueParameters.count { it.hasDefaultValue() },
+                              isHeader = descriptor is MemberDescriptor && descriptor.isHeader,
+                              isSyntheticMember = descriptor is SyntheticMemberDescriptor<*>
+                )
+
         val ValueParameterDescriptor.argumentValueType get() = varargElementType ?: type
     }
 }
diff --git a/compiler/testData/diagnostics/tests/OperatorChecks.kt b/compiler/testData/diagnostics/tests/OperatorChecks.kt
index 3e7b299ec59..01cbaefd66b 100644
--- a/compiler/testData/diagnostics/tests/OperatorChecks.kt
+++ b/compiler/testData/diagnostics/tests/OperatorChecks.kt
@@ -1,3 +1,5 @@
+// !DIAGNOSTICS: -EXTENSION_SHADOWED_BY_MEMBER
+
 import kotlin.reflect.KProperty
 
 interface Example {
diff --git a/compiler/testData/diagnostics/tests/callableReference/emptyLhs.kt b/compiler/testData/diagnostics/tests/callableReference/emptyLhs.kt
index d814b08aceb..7a22a2cd1b9 100644
--- a/compiler/testData/diagnostics/tests/callableReference/emptyLhs.kt
+++ b/compiler/testData/diagnostics/tests/callableReference/emptyLhs.kt
@@ -1,4 +1,4 @@
-// !DIAGNOSTICS: -UNUSED_EXPRESSION
+// !DIAGNOSTICS: -UNUSED_EXPRESSION, -EXTENSION_SHADOWED_BY_MEMBER
 
 val topLevelVal = 1
 fun topLevelFun() = 2
diff --git a/compiler/testData/diagnostics/tests/callableReference/function/noAmbiguityMemberVsExtension.kt b/compiler/testData/diagnostics/tests/callableReference/function/noAmbiguityMemberVsExtension.kt
index f8cbe71c6b2..d84c9cc1ce1 100644
--- a/compiler/testData/diagnostics/tests/callableReference/function/noAmbiguityMemberVsExtension.kt
+++ b/compiler/testData/diagnostics/tests/callableReference/function/noAmbiguityMemberVsExtension.kt
@@ -6,7 +6,7 @@ class A {
     fun foo() = 42
 }
 
-fun A.foo() {}
+fun A.<!EXTENSION_SHADOWED_BY_MEMBER!>foo<!>() {}
 
 fun main() {
     val x = A::foo
diff --git a/compiler/testData/diagnostics/tests/callableReference/resolve/withExtFun.kt b/compiler/testData/diagnostics/tests/callableReference/resolve/withExtFun.kt
index 5a52d59c4d3..cfe695bb2a9 100644
--- a/compiler/testData/diagnostics/tests/callableReference/resolve/withExtFun.kt
+++ b/compiler/testData/diagnostics/tests/callableReference/resolve/withExtFun.kt
@@ -1,4 +1,4 @@
-// !DIAGNOSTICS: -UNUSED_PARAMETER
+// !DIAGNOSTICS: -UNUSED_PARAMETER, -EXTENSION_SHADOWED_BY_MEMBER
 
 import kotlin.reflect.*
 
diff --git a/compiler/testData/diagnostics/tests/dataFlowInfoTraversal/BinaryExpressionIdentifier.kt b/compiler/testData/diagnostics/tests/dataFlowInfoTraversal/BinaryExpressionIdentifier.kt
index 8d07b8b532a..8edf3e80777 100644
--- a/compiler/testData/diagnostics/tests/dataFlowInfoTraversal/BinaryExpressionIdentifier.kt
+++ b/compiler/testData/diagnostics/tests/dataFlowInfoTraversal/BinaryExpressionIdentifier.kt
@@ -1,6 +1,6 @@
 // !CHECK_TYPE
 
-infix fun Int.compareTo(<!UNUSED_PARAMETER!>o<!>: Int) = 0
+infix fun Int.<!EXTENSION_SHADOWED_BY_MEMBER!>compareTo<!>(<!UNUSED_PARAMETER!>o<!>: Int) = 0
 
 fun foo(a: Number): Int {
     val result = (a as Int) compareTo <!DEBUG_INFO_SMARTCAST!>a<!>
diff --git a/compiler/testData/diagnostics/tests/declarationChecks/localDeclarationModifiers.kt b/compiler/testData/diagnostics/tests/declarationChecks/localDeclarationModifiers.kt
index 563d53a17da..d816dd7182f 100644
--- a/compiler/testData/diagnostics/tests/declarationChecks/localDeclarationModifiers.kt
+++ b/compiler/testData/diagnostics/tests/declarationChecks/localDeclarationModifiers.kt
@@ -7,6 +7,6 @@ class T {
 fun foo() {
     <!WRONG_MODIFIER_TARGET!>public<!> val <!UNUSED_VARIABLE!>i<!> = 11
     <!WRONG_MODIFIER_TARGET!>abstract<!> val <!VARIABLE_WITH_NO_TYPE_NO_INITIALIZER, UNUSED_VARIABLE!>j<!>
-    <!WRONG_MODIFIER_TARGET!>override<!> fun T.baz() = 2
+    <!WRONG_MODIFIER_TARGET!>override<!> fun T.<!EXTENSION_SHADOWED_BY_MEMBER!>baz<!>() = 2
     <!WRONG_MODIFIER_TARGET!>private<!> fun bar() = 2
 }
\ No newline at end of file
diff --git a/compiler/testData/diagnostics/tests/declarationChecks/localFunctionNoInheritVisibility.kt b/compiler/testData/diagnostics/tests/declarationChecks/localFunctionNoInheritVisibility.kt
index 44a5b20249e..859148ef51b 100644
--- a/compiler/testData/diagnostics/tests/declarationChecks/localFunctionNoInheritVisibility.kt
+++ b/compiler/testData/diagnostics/tests/declarationChecks/localFunctionNoInheritVisibility.kt
@@ -7,7 +7,7 @@ class T {
 <!WRONG_MODIFIER_TARGET!>override<!> fun zzz() {}
 
 fun foo(t: T) {
-    <!WRONG_MODIFIER_TARGET!>override<!> fun T.baz() = 2
+    <!WRONG_MODIFIER_TARGET!>override<!> fun T.<!EXTENSION_SHADOWED_BY_MEMBER!>baz<!>() = 2
 
     // was "Visibility is unknown yet exception"
     t.baz()
diff --git a/compiler/testData/diagnostics/tests/extensions/ExtensionFunctions.kt b/compiler/testData/diagnostics/tests/extensions/ExtensionFunctions.kt
index c11724ad947..718d0585865 100644
--- a/compiler/testData/diagnostics/tests/extensions/ExtensionFunctions.kt
+++ b/compiler/testData/diagnostics/tests/extensions/ExtensionFunctions.kt
@@ -51,7 +51,7 @@ import outer.*
           val foo : Int = 0
         }
 
-        fun Any.equals(<!UNUSED_PARAMETER!>other<!> : Any?) : Boolean = true
+        fun Any.<!EXTENSION_SHADOWED_BY_MEMBER!>equals<!>(<!UNUSED_PARAMETER!>other<!> : Any?) : Boolean = true
         fun Any?.equals1(<!UNUSED_PARAMETER!>other<!> : Any?) : Boolean = true
         fun Any.equals2(<!UNUSED_PARAMETER!>other<!> : Any?) : Boolean = true
 
diff --git a/compiler/testData/diagnostics/tests/extensions/ExtensionsCalledOnSuper.kt b/compiler/testData/diagnostics/tests/extensions/ExtensionsCalledOnSuper.kt
index 16744a9ad03..220d2cbeb2a 100644
--- a/compiler/testData/diagnostics/tests/extensions/ExtensionsCalledOnSuper.kt
+++ b/compiler/testData/diagnostics/tests/extensions/ExtensionsCalledOnSuper.kt
@@ -6,12 +6,12 @@ interface T {
 
 fun T.bar() {}
 
-fun T.buzz() {}
+fun T.<!EXTENSION_SHADOWED_BY_MEMBER!>buzz<!>() {}
 fun T.buzz1() {}
 
 class C : T {
     fun test() {
-        fun T.buzz() {}
+        fun T.<!EXTENSION_SHADOWED_BY_MEMBER!>buzz<!>() {}
         fun T.buzz1() {}
         super.foo() // OK
         <!SUPER_CANT_BE_EXTENSION_RECEIVER!>super<!>.bar() // Error
diff --git a/compiler/testData/diagnostics/tests/inference/nestedCalls/binaryExpressions.kt b/compiler/testData/diagnostics/tests/inference/nestedCalls/binaryExpressions.kt
index 596a86607ea..279645dd144 100644
--- a/compiler/testData/diagnostics/tests/inference/nestedCalls/binaryExpressions.kt
+++ b/compiler/testData/diagnostics/tests/inference/nestedCalls/binaryExpressions.kt
@@ -41,7 +41,7 @@ fun test2(z: Z) {
 }
 
 //'equals' operation
-fun Z.equals(any: Any): Int { use(any); return 1 }
+fun Z.<!EXTENSION_SHADOWED_BY_MEMBER!>equals<!>(any: Any): Int { use(any); return 1 }
 
 fun test3(z: Z) {
     z == <!TYPE_INFERENCE_NO_INFORMATION_FOR_PARAMETER!>newA<!>()
diff --git a/compiler/testData/diagnostics/tests/inference/regressions/kt2179.kt b/compiler/testData/diagnostics/tests/inference/regressions/kt2179.kt
index b19c3e751d1..6101e0ebdc4 100644
--- a/compiler/testData/diagnostics/tests/inference/regressions/kt2179.kt
+++ b/compiler/testData/diagnostics/tests/inference/regressions/kt2179.kt
@@ -42,5 +42,5 @@ fun <T, C: MutableCollection<in T>> Array<T>.toCollection(result: C) : C {
     return result
 }
 
-val Collection<*>.size : Int
+val Collection<*>.<!EXTENSION_SHADOWED_BY_MEMBER!>size<!> : Int
     get() = size
diff --git a/compiler/testData/diagnostics/tests/modifiers/operatorInfix/MemberFunctions.kt b/compiler/testData/diagnostics/tests/modifiers/operatorInfix/MemberFunctions.kt
index 82811b756f2..118c18e1137 100644
--- a/compiler/testData/diagnostics/tests/modifiers/operatorInfix/MemberFunctions.kt
+++ b/compiler/testData/diagnostics/tests/modifiers/operatorInfix/MemberFunctions.kt
@@ -1,4 +1,4 @@
-// !DIAGNOSTICS: -UNUSED_PARAMETER
+// !DIAGNOSTICS: -UNUSED_PARAMETER, -EXTENSION_SHADOWED_BY_MEMBER
 
 class Example {
     operator infix fun plus(other: Example) = 0
diff --git a/compiler/testData/diagnostics/tests/modifiers/operatorInfix/Simple.kt b/compiler/testData/diagnostics/tests/modifiers/operatorInfix/Simple.kt
index 3d0a15c26c5..b58a31a2e03 100644
--- a/compiler/testData/diagnostics/tests/modifiers/operatorInfix/Simple.kt
+++ b/compiler/testData/diagnostics/tests/modifiers/operatorInfix/Simple.kt
@@ -1,4 +1,4 @@
-// !DIAGNOSTICS: -UNUSED_PARAMETER
+// !DIAGNOSTICS: -UNUSED_PARAMETER, -EXTENSION_SHADOWED_BY_MEMBER
 
 open class Example {
     fun invoke() = 0
diff --git a/compiler/testData/diagnostics/tests/operatorRem/modWithRemAssign.kt b/compiler/testData/diagnostics/tests/operatorRem/modWithRemAssign.kt
index 5b69f5d996f..c190b101aec 100644
--- a/compiler/testData/diagnostics/tests/operatorRem/modWithRemAssign.kt
+++ b/compiler/testData/diagnostics/tests/operatorRem/modWithRemAssign.kt
@@ -1,4 +1,4 @@
-// !DIAGNOSTICS: -UNUSED_PARAMETER
+// !DIAGNOSTICS: -UNUSED_PARAMETER, -EXTENSION_SHADOWED_BY_MEMBER
 
 class ModAndRemAssign {
     <!DEPRECATED_BINARY_MOD!>operator<!> fun mod(x: Int) = ModAndRemAssign()
diff --git a/compiler/testData/diagnostics/tests/operatorRem/noOperatorRemFeature.kt b/compiler/testData/diagnostics/tests/operatorRem/noOperatorRemFeature.kt
index 9c9582086ab..c100ee377f1 100644
--- a/compiler/testData/diagnostics/tests/operatorRem/noOperatorRemFeature.kt
+++ b/compiler/testData/diagnostics/tests/operatorRem/noOperatorRemFeature.kt
@@ -1,5 +1,5 @@
 // !LANGUAGE: -OperatorRem
-// !DIAGNOSTICS: -UNUSED_PARAMETER, -UNUSED_VARIABLE
+// !DIAGNOSTICS: -UNUSED_PARAMETER, -UNUSED_VARIABLE, -EXTENSION_SHADOWED_BY_MEMBER
 
 class Foo {
     <!UNSUPPORTED_FEATURE!>operator<!> fun rem(x: Int): Foo = Foo()
diff --git a/compiler/testData/diagnostics/tests/operatorRem/numberRemConversions.kt b/compiler/testData/diagnostics/tests/operatorRem/numberRemConversions.kt
index 9ba8553cda5..8a4f61dc926 100644
--- a/compiler/testData/diagnostics/tests/operatorRem/numberRemConversions.kt
+++ b/compiler/testData/diagnostics/tests/operatorRem/numberRemConversions.kt
@@ -12,4 +12,4 @@ fun test() {
     fooShort(1 % 1)
 }
 
-public operator fun Int.rem(other: Int): Int = 0
\ No newline at end of file
+public operator fun Int.<!EXTENSION_SHADOWED_BY_MEMBER!>rem<!>(other: Int): Int = 0
\ No newline at end of file
diff --git a/compiler/testData/diagnostics/tests/operatorRem/remWithModAndModAssign.kt b/compiler/testData/diagnostics/tests/operatorRem/remWithModAndModAssign.kt
index a4550801ae3..c401be2e4a7 100644
--- a/compiler/testData/diagnostics/tests/operatorRem/remWithModAndModAssign.kt
+++ b/compiler/testData/diagnostics/tests/operatorRem/remWithModAndModAssign.kt
@@ -1,4 +1,4 @@
-// !DIAGNOSTICS: -UNUSED_PARAMETER
+// !DIAGNOSTICS: -UNUSED_PARAMETER, -EXTENSION_SHADOWED_BY_MEMBER
 
 class ModAndRemAssign {
     <!DEPRECATED_BINARY_MOD!>operator<!> fun mod(x: Int) = ModAndRemAssign()
diff --git a/compiler/testData/diagnostics/tests/redeclarations/shadowedExtension/extensionFunShadowedByInnerClassConstructor.kt b/compiler/testData/diagnostics/tests/redeclarations/shadowedExtension/extensionFunShadowedByInnerClassConstructor.kt
new file mode 100644
index 00000000000..729b0ca5e3c
--- /dev/null
+++ b/compiler/testData/diagnostics/tests/redeclarations/shadowedExtension/extensionFunShadowedByInnerClassConstructor.kt
@@ -0,0 +1,31 @@
+// !DIAGNOSTICS: -UNUSED_PARAMETER
+
+class Outer {
+    inner class Test1
+    inner class Test2(val x: Int)
+    inner class Test3(val x: Any)
+    inner class Test4<T>(val x: T)
+    inner class Test5(val x: Int) {
+        constructor() : this(0)
+        private constructor(z: String) : this(z.length)
+    }
+
+    class TestNested
+
+    internal class TestInternal
+    protected class TestProtected
+    private class TestPrivate
+}
+
+fun Outer.<!EXTENSION_FUNCTION_SHADOWED_BY_INNER_CLASS_CONSTRUCTOR!>Test1<!>() {}
+fun Outer.<!EXTENSION_FUNCTION_SHADOWED_BY_INNER_CLASS_CONSTRUCTOR!>Test2<!>(x: Int) {}
+fun Outer.<!EXTENSION_FUNCTION_SHADOWED_BY_INNER_CLASS_CONSTRUCTOR!>Test3<!>(x: String) {}
+fun <T> Outer.Test3(x: T) {}
+fun <T : Number> Outer.<!EXTENSION_FUNCTION_SHADOWED_BY_INNER_CLASS_CONSTRUCTOR!>Test4<!>(x: T) {}
+fun Outer.<!EXTENSION_FUNCTION_SHADOWED_BY_INNER_CLASS_CONSTRUCTOR!>Test5<!>() {}
+fun Outer.Test5(z: String) {}
+
+fun Outer.TestNested() {}
+fun Outer.TestInternal() {}
+fun Outer.TestProtected() {}
+fun Outer.TestPrivate() {}
\ No newline at end of file
diff --git a/compiler/testData/diagnostics/tests/redeclarations/shadowedExtension/extensionFunShadowedByInnerClassConstructor.txt b/compiler/testData/diagnostics/tests/redeclarations/shadowedExtension/extensionFunShadowedByInnerClassConstructor.txt
new file mode 100644
index 00000000000..1e5eaebda8d
--- /dev/null
+++ b/compiler/testData/diagnostics/tests/redeclarations/shadowedExtension/extensionFunShadowedByInnerClassConstructor.txt
@@ -0,0 +1,89 @@
+package
+
+public fun Outer.Test1(): kotlin.Unit
+public fun Outer.Test2(/*0*/ x: kotlin.Int): kotlin.Unit
+public fun </*0*/ T> Outer.Test3(/*0*/ x: T): kotlin.Unit
+public fun Outer.Test3(/*0*/ x: kotlin.String): kotlin.Unit
+public fun </*0*/ T : kotlin.Number> Outer.Test4(/*0*/ x: T): kotlin.Unit
+public fun Outer.Test5(): kotlin.Unit
+public fun Outer.Test5(/*0*/ z: kotlin.String): kotlin.Unit
+public fun Outer.TestInternal(): kotlin.Unit
+public fun Outer.TestNested(): kotlin.Unit
+public fun Outer.TestPrivate(): kotlin.Unit
+public fun Outer.TestProtected(): kotlin.Unit
+
+public final class Outer {
+    public constructor Outer()
+    public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+
+    public final inner class Test1 {
+        public constructor Test1()
+        public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+        public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+        public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+    }
+
+    public final inner class Test2 {
+        public constructor Test2(/*0*/ x: kotlin.Int)
+        public final val x: kotlin.Int
+        public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+        public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+        public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+    }
+
+    public final inner class Test3 {
+        public constructor Test3(/*0*/ x: kotlin.Any)
+        public final val x: kotlin.Any
+        public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+        public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+        public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+    }
+
+    public final inner class Test4</*0*/ T> {
+        public constructor Test4</*0*/ T>(/*0*/ x: T)
+        public final val x: T
+        public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+        public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+        public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+    }
+
+    public final inner class Test5 {
+        public constructor Test5()
+        public constructor Test5(/*0*/ x: kotlin.Int)
+        private constructor Test5(/*0*/ z: kotlin.String)
+        public final val x: kotlin.Int
+        public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+        public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+        public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+    }
+
+    internal final class TestInternal {
+        public constructor TestInternal()
+        public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+        public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+        public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+    }
+
+    public final class TestNested {
+        public constructor TestNested()
+        public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+        public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+        public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+    }
+
+    private final class TestPrivate {
+        public constructor TestPrivate()
+        public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+        public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+        public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+    }
+
+    protected final class TestProtected {
+        public constructor TestProtected()
+        public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+        public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+        public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+    }
+}
diff --git a/compiler/testData/diagnostics/tests/redeclarations/shadowedExtension/extensionFunShadowedByMemberFun.kt b/compiler/testData/diagnostics/tests/redeclarations/shadowedExtension/extensionFunShadowedByMemberFun.kt
new file mode 100644
index 00000000000..f7766e89acd
--- /dev/null
+++ b/compiler/testData/diagnostics/tests/redeclarations/shadowedExtension/extensionFunShadowedByMemberFun.kt
@@ -0,0 +1,32 @@
+// !DIAGNOSTICS: -UNUSED_PARAMETER
+
+interface Test1 {
+    fun test1() {}
+}
+fun Test1.<!EXTENSION_SHADOWED_BY_MEMBER!>test1<!>() {}
+
+interface Test2 {
+    fun test2(x: String) {}
+}
+fun Test2.test2(x: Any) {}
+
+interface Test3 {
+    fun test3(x: Any) {}
+}
+fun Test3.<!EXTENSION_SHADOWED_BY_MEMBER!>test3<!>(x: String) {}
+fun <T : Any?> Test3.test3(x: T) {}
+
+interface Test4 {
+    fun <T> test4(x: T) {}
+}
+fun Test4.<!EXTENSION_SHADOWED_BY_MEMBER!>test4<!>(x: String) {}
+
+interface Test5 {
+    fun <T> test5(x: T) {}
+}
+fun <T : Number> Test5.<!EXTENSION_SHADOWED_BY_MEMBER!>test5<!>(x: T) {}
+
+interface Test6 {
+    fun <T : List<Any>> test6(x: T) {}
+}
+fun <T : Set<Any>> Test6.test6(x: T) {}
diff --git a/compiler/testData/diagnostics/tests/redeclarations/shadowedExtension/extensionFunShadowedByMemberFun.txt b/compiler/testData/diagnostics/tests/redeclarations/shadowedExtension/extensionFunShadowedByMemberFun.txt
new file mode 100644
index 00000000000..11e3edfdb15
--- /dev/null
+++ b/compiler/testData/diagnostics/tests/redeclarations/shadowedExtension/extensionFunShadowedByMemberFun.txt
@@ -0,0 +1,51 @@
+package
+
+public fun Test1.test1(): kotlin.Unit
+public fun Test2.test2(/*0*/ x: kotlin.Any): kotlin.Unit
+public fun </*0*/ T> Test3.test3(/*0*/ x: T): kotlin.Unit
+public fun Test3.test3(/*0*/ x: kotlin.String): kotlin.Unit
+public fun Test4.test4(/*0*/ x: kotlin.String): kotlin.Unit
+public fun </*0*/ T : kotlin.Number> Test5.test5(/*0*/ x: T): kotlin.Unit
+public fun </*0*/ T : kotlin.collections.Set<kotlin.Any>> Test6.test6(/*0*/ x: T): kotlin.Unit
+
+public interface Test1 {
+    public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    public open fun test1(): kotlin.Unit
+    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+}
+
+public interface Test2 {
+    public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    public open fun test2(/*0*/ x: kotlin.String): kotlin.Unit
+    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+}
+
+public interface Test3 {
+    public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    public open fun test3(/*0*/ x: kotlin.Any): kotlin.Unit
+    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+}
+
+public interface Test4 {
+    public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    public open fun </*0*/ T> test4(/*0*/ x: T): kotlin.Unit
+    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+}
+
+public interface Test5 {
+    public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    public open fun </*0*/ T> test5(/*0*/ x: T): kotlin.Unit
+    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+}
+
+public interface Test6 {
+    public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    public open fun </*0*/ T : kotlin.collections.List<kotlin.Any>> test6(/*0*/ x: T): kotlin.Unit
+    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+}
diff --git a/compiler/testData/diagnostics/tests/redeclarations/shadowedExtension/extensionFunShadowedByMemberPropertyWithInvoke.kt b/compiler/testData/diagnostics/tests/redeclarations/shadowedExtension/extensionFunShadowedByMemberPropertyWithInvoke.kt
new file mode 100644
index 00000000000..19a73c38b11
--- /dev/null
+++ b/compiler/testData/diagnostics/tests/redeclarations/shadowedExtension/extensionFunShadowedByMemberPropertyWithInvoke.kt
@@ -0,0 +1,18 @@
+// !DIAGNOSTICS: -UNUSED_PARAMETER
+
+interface WithInvoke {
+    operator fun invoke()
+    operator fun invoke(s: String)
+    operator fun <T> invoke(x: T, y: Int)
+    fun invoke(i: Int)
+}
+
+interface Test1 {
+    val test1: WithInvoke
+}
+
+fun Test1.<!EXTENSION_FUNCTION_SHADOWED_BY_MEMBER_PROPERTY_WITH_INVOKE!>test1<!>() {}
+fun Test1.<!EXTENSION_FUNCTION_SHADOWED_BY_MEMBER_PROPERTY_WITH_INVOKE!>test1<!>(s: String) {}
+fun Test1.test1(i: Int) {}
+fun Test1.<!EXTENSION_FUNCTION_SHADOWED_BY_MEMBER_PROPERTY_WITH_INVOKE!>test1<!>(x: Any, y: Int) {}
+fun <T : Number> Test1.<!EXTENSION_FUNCTION_SHADOWED_BY_MEMBER_PROPERTY_WITH_INVOKE!>test1<!>(x: T, y: Int) {}
\ No newline at end of file
diff --git a/compiler/testData/diagnostics/tests/redeclarations/shadowedExtension/extensionFunShadowedByMemberPropertyWithInvoke.txt b/compiler/testData/diagnostics/tests/redeclarations/shadowedExtension/extensionFunShadowedByMemberPropertyWithInvoke.txt
new file mode 100644
index 00000000000..6f8a7d6427c
--- /dev/null
+++ b/compiler/testData/diagnostics/tests/redeclarations/shadowedExtension/extensionFunShadowedByMemberPropertyWithInvoke.txt
@@ -0,0 +1,24 @@
+package
+
+public fun Test1.test1(): kotlin.Unit
+public fun </*0*/ T : kotlin.Number> Test1.test1(/*0*/ x: T, /*1*/ y: kotlin.Int): kotlin.Unit
+public fun Test1.test1(/*0*/ x: kotlin.Any, /*1*/ y: kotlin.Int): kotlin.Unit
+public fun Test1.test1(/*0*/ i: kotlin.Int): kotlin.Unit
+public fun Test1.test1(/*0*/ s: kotlin.String): kotlin.Unit
+
+public interface Test1 {
+    public abstract val test1: WithInvoke
+    public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+}
+
+public interface WithInvoke {
+    public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    public abstract operator fun invoke(): kotlin.Unit
+    public abstract operator fun </*0*/ T> invoke(/*0*/ x: T, /*1*/ y: kotlin.Int): kotlin.Unit
+    public abstract fun invoke(/*0*/ i: kotlin.Int): kotlin.Unit
+    public abstract operator fun invoke(/*0*/ s: kotlin.String): kotlin.Unit
+    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+}
diff --git a/compiler/testData/diagnostics/tests/redeclarations/shadowedExtension/extensionFunShadowedBySynthesizedMemberFun.kt b/compiler/testData/diagnostics/tests/redeclarations/shadowedExtension/extensionFunShadowedBySynthesizedMemberFun.kt
new file mode 100644
index 00000000000..ef71eb1d6e8
--- /dev/null
+++ b/compiler/testData/diagnostics/tests/redeclarations/shadowedExtension/extensionFunShadowedBySynthesizedMemberFun.kt
@@ -0,0 +1,5 @@
+// !DIAGNOSTICS: -UNUSED_PARAMETER
+
+data class DataClass(val x: Int)
+
+fun DataClass.<!EXTENSION_SHADOWED_BY_MEMBER!>component1<!>() = 42
\ No newline at end of file
diff --git a/compiler/testData/diagnostics/tests/redeclarations/shadowedExtension/extensionFunShadowedBySynthesizedMemberFun.txt b/compiler/testData/diagnostics/tests/redeclarations/shadowedExtension/extensionFunShadowedBySynthesizedMemberFun.txt
new file mode 100644
index 00000000000..da55395761a
--- /dev/null
+++ b/compiler/testData/diagnostics/tests/redeclarations/shadowedExtension/extensionFunShadowedBySynthesizedMemberFun.txt
@@ -0,0 +1,13 @@
+package
+
+public fun DataClass.component1(): kotlin.Int
+
+public final data class DataClass {
+    public constructor DataClass(/*0*/ x: kotlin.Int)
+    public final val x: kotlin.Int
+    public final operator /*synthesized*/ fun component1(): kotlin.Int
+    public final /*synthesized*/ fun copy(/*0*/ x: kotlin.Int = ...): DataClass
+    public open override /*1*/ /*synthesized*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public open override /*1*/ /*synthesized*/ fun hashCode(): kotlin.Int
+    public open override /*1*/ /*synthesized*/ fun toString(): kotlin.String
+}
diff --git a/compiler/testData/diagnostics/tests/redeclarations/shadowedExtension/extensionFunVsMemberExtensionFun.kt b/compiler/testData/diagnostics/tests/redeclarations/shadowedExtension/extensionFunVsMemberExtensionFun.kt
new file mode 100644
index 00000000000..8298c498e70
--- /dev/null
+++ b/compiler/testData/diagnostics/tests/redeclarations/shadowedExtension/extensionFunVsMemberExtensionFun.kt
@@ -0,0 +1,5 @@
+class C {
+    fun Int.foo() {}
+}
+
+fun C.foo() {}
\ No newline at end of file
diff --git a/compiler/testData/diagnostics/tests/redeclarations/shadowedExtension/extensionFunVsMemberExtensionFun.txt b/compiler/testData/diagnostics/tests/redeclarations/shadowedExtension/extensionFunVsMemberExtensionFun.txt
new file mode 100644
index 00000000000..92274f01030
--- /dev/null
+++ b/compiler/testData/diagnostics/tests/redeclarations/shadowedExtension/extensionFunVsMemberExtensionFun.txt
@@ -0,0 +1,11 @@
+package
+
+public fun C.foo(): kotlin.Unit
+
+public final class C {
+    public constructor C()
+    public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+    public final fun kotlin.Int.foo(): kotlin.Unit
+}
diff --git a/compiler/testData/diagnostics/tests/redeclarations/shadowedExtension/extensionOnErrorType.kt b/compiler/testData/diagnostics/tests/redeclarations/shadowedExtension/extensionOnErrorType.kt
new file mode 100644
index 00000000000..03781e5adfa
--- /dev/null
+++ b/compiler/testData/diagnostics/tests/redeclarations/shadowedExtension/extensionOnErrorType.kt
@@ -0,0 +1,7 @@
+interface G<T> {
+    fun foo()
+    val bar: Int
+}
+
+fun <!WRONG_NUMBER_OF_TYPE_ARGUMENTS!>G<!>.foo() {}
+val <!WRONG_NUMBER_OF_TYPE_ARGUMENTS!>G<!>.bar: Int get() = 42
\ No newline at end of file
diff --git a/compiler/testData/diagnostics/tests/redeclarations/shadowedExtension/extensionOnErrorType.txt b/compiler/testData/diagnostics/tests/redeclarations/shadowedExtension/extensionOnErrorType.txt
new file mode 100644
index 00000000000..928eb2ecdbb
--- /dev/null
+++ b/compiler/testData/diagnostics/tests/redeclarations/shadowedExtension/extensionOnErrorType.txt
@@ -0,0 +1,12 @@
+package
+
+public val [ERROR : G].bar: kotlin.Int
+public fun [ERROR : G].foo(): kotlin.Unit
+
+public interface G</*0*/ T> {
+    public abstract val bar: kotlin.Int
+    public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public abstract fun foo(): kotlin.Unit
+    public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+}
diff --git a/compiler/testData/diagnostics/tests/redeclarations/shadowedExtension/extensionOnNullableReceiver.kt b/compiler/testData/diagnostics/tests/redeclarations/shadowedExtension/extensionOnNullableReceiver.kt
new file mode 100644
index 00000000000..796aee5f4e0
--- /dev/null
+++ b/compiler/testData/diagnostics/tests/redeclarations/shadowedExtension/extensionOnNullableReceiver.kt
@@ -0,0 +1,7 @@
+interface Test {
+    fun foo()
+    val bar: Int
+}
+
+fun Test?.foo() {}
+val Test?.bar: Int get() = 42
\ No newline at end of file
diff --git a/compiler/testData/diagnostics/tests/redeclarations/shadowedExtension/extensionOnNullableReceiver.txt b/compiler/testData/diagnostics/tests/redeclarations/shadowedExtension/extensionOnNullableReceiver.txt
new file mode 100644
index 00000000000..d645ba7f493
--- /dev/null
+++ b/compiler/testData/diagnostics/tests/redeclarations/shadowedExtension/extensionOnNullableReceiver.txt
@@ -0,0 +1,12 @@
+package
+
+public val Test?.bar: kotlin.Int
+public fun Test?.foo(): kotlin.Unit
+
+public interface Test {
+    public abstract val bar: kotlin.Int
+    public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public abstract fun foo(): kotlin.Unit
+    public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+}
diff --git a/compiler/testData/diagnostics/tests/redeclarations/shadowedExtension/extensionPropertyShadowedByMemberProperty.kt b/compiler/testData/diagnostics/tests/redeclarations/shadowedExtension/extensionPropertyShadowedByMemberProperty.kt
new file mode 100644
index 00000000000..06089846990
--- /dev/null
+++ b/compiler/testData/diagnostics/tests/redeclarations/shadowedExtension/extensionPropertyShadowedByMemberProperty.kt
@@ -0,0 +1,22 @@
+// !DIAGNOSTICS: -UNUSED_PARAMETER
+
+interface Test1 {
+    val test1: Int
+}
+val Test1.<!EXTENSION_SHADOWED_BY_MEMBER!>test1<!>: Int get() = 42
+
+interface Test2 {
+    var test2: Int
+}
+val Test2.<!EXTENSION_SHADOWED_BY_MEMBER!>test2<!>: Int get() = 42
+
+interface Test3 {
+    val test3: Int
+}
+var Test3.<!EXTENSION_SHADOWED_BY_MEMBER!>test3<!>: Int get() = 42; set(v) {}
+
+interface Test4 {
+    val test4: Int
+}
+var Test4.<!EXTENSION_SHADOWED_BY_MEMBER!>test4<!>: Int get() = 42; set(v) {}
+
diff --git a/compiler/testData/diagnostics/tests/redeclarations/shadowedExtension/extensionPropertyShadowedByMemberProperty.txt b/compiler/testData/diagnostics/tests/redeclarations/shadowedExtension/extensionPropertyShadowedByMemberProperty.txt
new file mode 100644
index 00000000000..802e57b47fd
--- /dev/null
+++ b/compiler/testData/diagnostics/tests/redeclarations/shadowedExtension/extensionPropertyShadowedByMemberProperty.txt
@@ -0,0 +1,34 @@
+package
+
+public val Test1.test1: kotlin.Int
+public val Test2.test2: kotlin.Int
+public var Test3.test3: kotlin.Int
+public var Test4.test4: kotlin.Int
+
+public interface Test1 {
+    public abstract val test1: kotlin.Int
+    public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+}
+
+public interface Test2 {
+    public abstract var test2: kotlin.Int
+    public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+}
+
+public interface Test3 {
+    public abstract val test3: kotlin.Int
+    public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+}
+
+public interface Test4 {
+    public abstract val test4: kotlin.Int
+    public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+}
diff --git a/compiler/testData/diagnostics/tests/redeclarations/shadowedExtension/extensionShadowedByDelegatedMember.kt b/compiler/testData/diagnostics/tests/redeclarations/shadowedExtension/extensionShadowedByDelegatedMember.kt
new file mode 100644
index 00000000000..20e7c710b6f
--- /dev/null
+++ b/compiler/testData/diagnostics/tests/redeclarations/shadowedExtension/extensionShadowedByDelegatedMember.kt
@@ -0,0 +1,16 @@
+// !DIAGNOSTICS: -UNUSED_PARAMETER
+
+interface IBase {
+    fun foo()
+    val bar: Int
+}
+
+object Impl : IBase {
+    override fun foo() {}
+    override val bar: Int get() = 42
+}
+
+object Test : IBase by Impl
+
+fun Test.<!EXTENSION_SHADOWED_BY_MEMBER!>foo<!>() {}
+val Test.<!EXTENSION_SHADOWED_BY_MEMBER!>bar<!>: Int get() = 42
\ No newline at end of file
diff --git a/compiler/testData/diagnostics/tests/redeclarations/shadowedExtension/extensionShadowedByDelegatedMember.txt b/compiler/testData/diagnostics/tests/redeclarations/shadowedExtension/extensionShadowedByDelegatedMember.txt
new file mode 100644
index 00000000000..24c4c3120ad
--- /dev/null
+++ b/compiler/testData/diagnostics/tests/redeclarations/shadowedExtension/extensionShadowedByDelegatedMember.txt
@@ -0,0 +1,30 @@
+package
+
+public val Test.bar: kotlin.Int
+public fun Test.foo(): kotlin.Unit
+
+public interface IBase {
+    public abstract val bar: kotlin.Int
+    public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public abstract fun foo(): kotlin.Unit
+    public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+}
+
+public object Impl : IBase {
+    private constructor Impl()
+    public open override /*1*/ val bar: kotlin.Int
+    public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public open override /*1*/ fun foo(): kotlin.Unit
+    public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+}
+
+public object Test : IBase {
+    private constructor Test()
+    public open override /*1*/ /*delegation*/ val bar: kotlin.Int
+    public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public open override /*1*/ /*delegation*/ fun foo(): kotlin.Unit
+    public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+}
diff --git a/compiler/testData/diagnostics/tests/redeclarations/shadowedExtension/extensionVsNonPublicMember.kt b/compiler/testData/diagnostics/tests/redeclarations/shadowedExtension/extensionVsNonPublicMember.kt
new file mode 100644
index 00000000000..7587fc5e14a
--- /dev/null
+++ b/compiler/testData/diagnostics/tests/redeclarations/shadowedExtension/extensionVsNonPublicMember.kt
@@ -0,0 +1,47 @@
+class WithPublicInvoke {
+    public operator fun invoke() {}
+}
+
+class WithInternalInvoke {
+    internal operator fun invoke() {}
+}
+
+class WithProtectedInvoke {
+    protected operator fun invoke() {}
+}
+
+class WithPrivateInvoke {
+    private operator fun invoke() {}
+}
+
+class Test {
+    public fun publicFoo() {}
+    internal fun internalFoo() {}
+    protected fun protectedFoo() {}
+    private fun privateFoo() {}
+
+    public val publicVal = 42
+    internal val internalVal = 42
+    protected val protectedVal = 42
+    private val privateVal = 42
+
+    public val withPublicInvoke = WithPublicInvoke()
+    public val withInternalInvoke = WithInternalInvoke()
+    public val withProtectedInvoke = WithProtectedInvoke()
+    public val withPrivateInvoke = WithPrivateInvoke()
+}
+
+private fun Test.<!EXTENSION_SHADOWED_BY_MEMBER!>publicFoo<!>() {}
+fun Test.internalFoo() {}
+fun Test.protectedFoo() {}
+fun Test.privateFoo() {}
+
+val Test.<!EXTENSION_SHADOWED_BY_MEMBER!>publicVal<!>: Int get() = 42
+val Test.internalVal: Int get() = 42
+val Test.protectedVal: Int get() = 42
+val Test.privateVal: Int get() = 42
+
+fun Test.<!EXTENSION_FUNCTION_SHADOWED_BY_MEMBER_PROPERTY_WITH_INVOKE!>withPublicInvoke<!>() {}
+fun Test.wihtInternalInvoke() {}
+fun Test.withProtectedInvoke() {}
+fun Test.withPrivateInvoke() {}
\ No newline at end of file
diff --git a/compiler/testData/diagnostics/tests/redeclarations/shadowedExtension/extensionVsNonPublicMember.txt b/compiler/testData/diagnostics/tests/redeclarations/shadowedExtension/extensionVsNonPublicMember.txt
new file mode 100644
index 00000000000..c31cc957efb
--- /dev/null
+++ b/compiler/testData/diagnostics/tests/redeclarations/shadowedExtension/extensionVsNonPublicMember.txt
@@ -0,0 +1,65 @@
+package
+
+public val Test.internalVal: kotlin.Int
+public val Test.privateVal: kotlin.Int
+public val Test.protectedVal: kotlin.Int
+public val Test.publicVal: kotlin.Int
+public fun Test.internalFoo(): kotlin.Unit
+public fun Test.privateFoo(): kotlin.Unit
+public fun Test.protectedFoo(): kotlin.Unit
+private fun Test.publicFoo(): kotlin.Unit
+public fun Test.wihtInternalInvoke(): kotlin.Unit
+public fun Test.withPrivateInvoke(): kotlin.Unit
+public fun Test.withProtectedInvoke(): kotlin.Unit
+public fun Test.withPublicInvoke(): kotlin.Unit
+
+public final class Test {
+    public constructor Test()
+    internal final val internalVal: kotlin.Int = 42
+    private final val privateVal: kotlin.Int = 42
+    protected final val protectedVal: kotlin.Int = 42
+    public final val publicVal: kotlin.Int = 42
+    public final val withInternalInvoke: WithInternalInvoke
+    public final val withPrivateInvoke: WithPrivateInvoke
+    public final val withProtectedInvoke: WithProtectedInvoke
+    public final val withPublicInvoke: WithPublicInvoke
+    public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    internal final fun internalFoo(): kotlin.Unit
+    private final fun privateFoo(): kotlin.Unit
+    protected final fun protectedFoo(): kotlin.Unit
+    public final fun publicFoo(): kotlin.Unit
+    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+}
+
+public final class WithInternalInvoke {
+    public constructor WithInternalInvoke()
+    public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    internal final operator fun invoke(): kotlin.Unit
+    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+}
+
+public final class WithPrivateInvoke {
+    public constructor WithPrivateInvoke()
+    public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    private final operator fun invoke(): kotlin.Unit
+    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+}
+
+public final class WithProtectedInvoke {
+    public constructor WithProtectedInvoke()
+    public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    protected final operator fun invoke(): kotlin.Unit
+    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+}
+
+public final class WithPublicInvoke {
+    public constructor WithPublicInvoke()
+    public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    public final operator fun invoke(): kotlin.Unit
+    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+}
diff --git a/compiler/testData/diagnostics/tests/redeclarations/shadowedExtension/localExtensionShadowedByMember.kt b/compiler/testData/diagnostics/tests/redeclarations/shadowedExtension/localExtensionShadowedByMember.kt
new file mode 100644
index 00000000000..9c20634ca52
--- /dev/null
+++ b/compiler/testData/diagnostics/tests/redeclarations/shadowedExtension/localExtensionShadowedByMember.kt
@@ -0,0 +1,7 @@
+interface IFoo {
+    fun foo()
+}
+
+fun outer() {
+    fun IFoo.<!EXTENSION_SHADOWED_BY_MEMBER!>foo<!>() {}
+}
\ No newline at end of file
diff --git a/compiler/testData/diagnostics/tests/redeclarations/shadowedExtension/localExtensionShadowedByMember.txt b/compiler/testData/diagnostics/tests/redeclarations/shadowedExtension/localExtensionShadowedByMember.txt
new file mode 100644
index 00000000000..97403713b3c
--- /dev/null
+++ b/compiler/testData/diagnostics/tests/redeclarations/shadowedExtension/localExtensionShadowedByMember.txt
@@ -0,0 +1,10 @@
+package
+
+public fun outer(): kotlin.Unit
+
+public interface IFoo {
+    public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public abstract fun foo(): kotlin.Unit
+    public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+}
diff --git a/compiler/testData/diagnostics/tests/redeclarations/shadowedExtension/memberExtensionShadowedByMember.kt b/compiler/testData/diagnostics/tests/redeclarations/shadowedExtension/memberExtensionShadowedByMember.kt
new file mode 100644
index 00000000000..8b3f7bc34ca
--- /dev/null
+++ b/compiler/testData/diagnostics/tests/redeclarations/shadowedExtension/memberExtensionShadowedByMember.kt
@@ -0,0 +1,9 @@
+interface IFooBar {
+    fun foo()
+    val bar: Int
+}
+
+class Host {
+    fun IFooBar.<!EXTENSION_SHADOWED_BY_MEMBER!>foo<!>() {}
+    val IFooBar.<!EXTENSION_SHADOWED_BY_MEMBER!>bar<!>: Int get() = 42
+}
\ No newline at end of file
diff --git a/compiler/testData/diagnostics/tests/redeclarations/shadowedExtension/memberExtensionShadowedByMember.txt b/compiler/testData/diagnostics/tests/redeclarations/shadowedExtension/memberExtensionShadowedByMember.txt
new file mode 100644
index 00000000000..4fb827193e1
--- /dev/null
+++ b/compiler/testData/diagnostics/tests/redeclarations/shadowedExtension/memberExtensionShadowedByMember.txt
@@ -0,0 +1,18 @@
+package
+
+public final class Host {
+    public constructor Host()
+    public final val IFooBar.bar: kotlin.Int
+    public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+    public final fun IFooBar.foo(): kotlin.Unit
+}
+
+public interface IFooBar {
+    public abstract val bar: kotlin.Int
+    public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public abstract fun foo(): kotlin.Unit
+    public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+}
diff --git a/compiler/testData/diagnostics/tests/redeclarations/shadowedExtension/operatorExtensionVsNonOperatorMember.kt b/compiler/testData/diagnostics/tests/redeclarations/shadowedExtension/operatorExtensionVsNonOperatorMember.kt
new file mode 100644
index 00000000000..35e3f25596d
--- /dev/null
+++ b/compiler/testData/diagnostics/tests/redeclarations/shadowedExtension/operatorExtensionVsNonOperatorMember.kt
@@ -0,0 +1,5 @@
+interface Test {
+    fun invoke()
+}
+
+operator fun Test.invoke() {}
\ No newline at end of file
diff --git a/compiler/testData/diagnostics/tests/redeclarations/shadowedExtension/operatorExtensionVsNonOperatorMember.txt b/compiler/testData/diagnostics/tests/redeclarations/shadowedExtension/operatorExtensionVsNonOperatorMember.txt
new file mode 100644
index 00000000000..c77f47e570b
--- /dev/null
+++ b/compiler/testData/diagnostics/tests/redeclarations/shadowedExtension/operatorExtensionVsNonOperatorMember.txt
@@ -0,0 +1,10 @@
+package
+
+public operator fun Test.invoke(): kotlin.Unit
+
+public interface Test {
+    public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    public abstract fun invoke(): kotlin.Unit
+    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+}
diff --git a/compiler/testData/diagnostics/tests/regressions/Jet69.kt b/compiler/testData/diagnostics/tests/regressions/Jet69.kt
index 604c731552a..85a6bf396dc 100644
--- a/compiler/testData/diagnostics/tests/regressions/Jet69.kt
+++ b/compiler/testData/diagnostics/tests/regressions/Jet69.kt
@@ -2,7 +2,7 @@ class Command() {}
 
 fun parse(<!UNUSED_PARAMETER!>cmd<!>: String): Command? { return null  }
 
-fun Any.equals(other : Any?) : Boolean = this === other
+fun Any.<!EXTENSION_SHADOWED_BY_MEMBER!>equals<!>(other : Any?) : Boolean = this === other
 
 fun main(args: Array<String>) {
     val command = parse("")
diff --git a/compiler/testData/diagnostics/tests/regressions/SpecififcityByReceiver.kt b/compiler/testData/diagnostics/tests/regressions/SpecififcityByReceiver.kt
index 0885069eb25..782de6062e9 100644
--- a/compiler/testData/diagnostics/tests/regressions/SpecififcityByReceiver.kt
+++ b/compiler/testData/diagnostics/tests/regressions/SpecififcityByReceiver.kt
@@ -1,4 +1,4 @@
-fun Any.equals(<!UNUSED_PARAMETER!>other<!> : Any?) : Boolean = true
+fun Any.<!EXTENSION_SHADOWED_BY_MEMBER!>equals<!>(<!UNUSED_PARAMETER!>other<!> : Any?) : Boolean = true
 
 fun main(args: Array<String>) {
 
diff --git a/compiler/testData/diagnostics/tests/resolve/priority/memberVsLocalExt.kt b/compiler/testData/diagnostics/tests/resolve/priority/memberVsLocalExt.kt
index 4142abaa394..68d46307516 100644
--- a/compiler/testData/diagnostics/tests/resolve/priority/memberVsLocalExt.kt
+++ b/compiler/testData/diagnostics/tests/resolve/priority/memberVsLocalExt.kt
@@ -7,7 +7,7 @@ class A {
 
 
 fun test(a: A) {
-    fun A.foo() = 4
+    fun A.<!EXTENSION_SHADOWED_BY_MEMBER!>foo<!>() = 4
 
     a.foo() checkType { _<A>() }
 
diff --git a/compiler/testData/diagnostics/tests/resolve/priority/synthesizedMembersVsExtension.kt b/compiler/testData/diagnostics/tests/resolve/priority/synthesizedMembersVsExtension.kt
index 1780db676c2..814df1d81a3 100644
--- a/compiler/testData/diagnostics/tests/resolve/priority/synthesizedMembersVsExtension.kt
+++ b/compiler/testData/diagnostics/tests/resolve/priority/synthesizedMembersVsExtension.kt
@@ -2,7 +2,7 @@
 
 data class A(val foo: Int)
 
-operator fun A.component1(): String = ""
+operator fun A.<!EXTENSION_SHADOWED_BY_MEMBER!>component1<!>(): String = ""
 
 fun test(a: A) {
     val (b) = a
diff --git a/compiler/testData/diagnostics/testsWithJava8/targetedBuiltIns/unsupportedFeature.kt b/compiler/testData/diagnostics/testsWithJava8/targetedBuiltIns/unsupportedFeature.kt
index 8b8b0735f9b..2d37d90c86c 100644
--- a/compiler/testData/diagnostics/testsWithJava8/targetedBuiltIns/unsupportedFeature.kt
+++ b/compiler/testData/diagnostics/testsWithJava8/targetedBuiltIns/unsupportedFeature.kt
@@ -12,7 +12,7 @@ class A1 : java.util.ArrayList<String>() {
 
 class B : <!DEPRECATION_ERROR!>Throwable<!>("", null, false, false)
 
-fun Throwable.fillInStackTrace() = 1
+fun Throwable.<!EXTENSION_SHADOWED_BY_MEMBER!>fillInStackTrace<!>() = 1
 
 fun foo(x: List<String>, y: Throwable) {
     x.<!DEPRECATION_ERROR!>stream<!>()
diff --git a/compiler/tests/org/jetbrains/kotlin/checkers/DiagnosticsTestGenerated.java b/compiler/tests/org/jetbrains/kotlin/checkers/DiagnosticsTestGenerated.java
index 5ee8127c51c..e5c589f3ede 100644
--- a/compiler/tests/org/jetbrains/kotlin/checkers/DiagnosticsTestGenerated.java
+++ b/compiler/tests/org/jetbrains/kotlin/checkers/DiagnosticsTestGenerated.java
@@ -15885,6 +15885,93 @@ public class DiagnosticsTestGenerated extends AbstractDiagnosticsTest {
                 String fileName = KotlinTestUtils.navigationMetadata("compiler/testData/diagnostics/tests/redeclarations/typeParameterWithTwoBounds.kt");
                 doTest(fileName);
             }
+
+            @TestMetadata("compiler/testData/diagnostics/tests/redeclarations/shadowedExtension")
+            @TestDataPath("$PROJECT_ROOT")
+            @RunWith(JUnit3RunnerWithInners.class)
+            public static class ShadowedExtension extends AbstractDiagnosticsTest {
+                public void testAllFilesPresentInShadowedExtension() throws Exception {
+                    KotlinTestUtils.assertAllTestsPresentByMetadata(this.getClass(), new File("compiler/testData/diagnostics/tests/redeclarations/shadowedExtension"), Pattern.compile("^(.+)\\.kt$"), TargetBackend.ANY, true);
+                }
+
+                @TestMetadata("extensionFunShadowedByInnerClassConstructor.kt")
+                public void testExtensionFunShadowedByInnerClassConstructor() throws Exception {
+                    String fileName = KotlinTestUtils.navigationMetadata("compiler/testData/diagnostics/tests/redeclarations/shadowedExtension/extensionFunShadowedByInnerClassConstructor.kt");
+                    doTest(fileName);
+                }
+
+                @TestMetadata("extensionFunShadowedByMemberFun.kt")
+                public void testExtensionFunShadowedByMemberFun() throws Exception {
+                    String fileName = KotlinTestUtils.navigationMetadata("compiler/testData/diagnostics/tests/redeclarations/shadowedExtension/extensionFunShadowedByMemberFun.kt");
+                    doTest(fileName);
+                }
+
+                @TestMetadata("extensionFunShadowedByMemberPropertyWithInvoke.kt")
+                public void testExtensionFunShadowedByMemberPropertyWithInvoke() throws Exception {
+                    String fileName = KotlinTestUtils.navigationMetadata("compiler/testData/diagnostics/tests/redeclarations/shadowedExtension/extensionFunShadowedByMemberPropertyWithInvoke.kt");
+                    doTest(fileName);
+                }
+
+                @TestMetadata("extensionFunShadowedBySynthesizedMemberFun.kt")
+                public void testExtensionFunShadowedBySynthesizedMemberFun() throws Exception {
+                    String fileName = KotlinTestUtils.navigationMetadata("compiler/testData/diagnostics/tests/redeclarations/shadowedExtension/extensionFunShadowedBySynthesizedMemberFun.kt");
+                    doTest(fileName);
+                }
+
+                @TestMetadata("extensionFunVsMemberExtensionFun.kt")
+                public void testExtensionFunVsMemberExtensionFun() throws Exception {
+                    String fileName = KotlinTestUtils.navigationMetadata("compiler/testData/diagnostics/tests/redeclarations/shadowedExtension/extensionFunVsMemberExtensionFun.kt");
+                    doTest(fileName);
+                }
+
+                @TestMetadata("extensionOnErrorType.kt")
+                public void testExtensionOnErrorType() throws Exception {
+                    String fileName = KotlinTestUtils.navigationMetadata("compiler/testData/diagnostics/tests/redeclarations/shadowedExtension/extensionOnErrorType.kt");
+                    doTest(fileName);
+                }
+
+                @TestMetadata("extensionOnNullableReceiver.kt")
+                public void testExtensionOnNullableReceiver() throws Exception {
+                    String fileName = KotlinTestUtils.navigationMetadata("compiler/testData/diagnostics/tests/redeclarations/shadowedExtension/extensionOnNullableReceiver.kt");
+                    doTest(fileName);
+                }
+
+                @TestMetadata("extensionPropertyShadowedByMemberProperty.kt")
+                public void testExtensionPropertyShadowedByMemberProperty() throws Exception {
+                    String fileName = KotlinTestUtils.navigationMetadata("compiler/testData/diagnostics/tests/redeclarations/shadowedExtension/extensionPropertyShadowedByMemberProperty.kt");
+                    doTest(fileName);
+                }
+
+                @TestMetadata("extensionShadowedByDelegatedMember.kt")
+                public void testExtensionShadowedByDelegatedMember() throws Exception {
+                    String fileName = KotlinTestUtils.navigationMetadata("compiler/testData/diagnostics/tests/redeclarations/shadowedExtension/extensionShadowedByDelegatedMember.kt");
+                    doTest(fileName);
+                }
+
+                @TestMetadata("extensionVsNonPublicMember.kt")
+                public void testExtensionVsNonPublicMember() throws Exception {
+                    String fileName = KotlinTestUtils.navigationMetadata("compiler/testData/diagnostics/tests/redeclarations/shadowedExtension/extensionVsNonPublicMember.kt");
+                    doTest(fileName);
+                }
+
+                @TestMetadata("localExtensionShadowedByMember.kt")
+                public void testLocalExtensionShadowedByMember() throws Exception {
+                    String fileName = KotlinTestUtils.navigationMetadata("compiler/testData/diagnostics/tests/redeclarations/shadowedExtension/localExtensionShadowedByMember.kt");
+                    doTest(fileName);
+                }
+
+                @TestMetadata("memberExtensionShadowedByMember.kt")
+                public void testMemberExtensionShadowedByMember() throws Exception {
+                    String fileName = KotlinTestUtils.navigationMetadata("compiler/testData/diagnostics/tests/redeclarations/shadowedExtension/memberExtensionShadowedByMember.kt");
+                    doTest(fileName);
+                }
+
+                @TestMetadata("operatorExtensionVsNonOperatorMember.kt")
+                public void testOperatorExtensionVsNonOperatorMember() throws Exception {
+                    String fileName = KotlinTestUtils.navigationMetadata("compiler/testData/diagnostics/tests/redeclarations/shadowedExtension/operatorExtensionVsNonOperatorMember.kt");
+                    doTest(fileName);
+                }
+            }
         }
 
         @TestMetadata("compiler/testData/diagnostics/tests/reflection")
diff --git a/core/descriptors/src/org/jetbrains/kotlin/incremental/components/LookupLocation.kt b/core/descriptors/src/org/jetbrains/kotlin/incremental/components/LookupLocation.kt
index a4daebdb4f1..a1b830fa371 100644
--- a/core/descriptors/src/org/jetbrains/kotlin/incremental/components/LookupLocation.kt
+++ b/core/descriptors/src/org/jetbrains/kotlin/incremental/components/LookupLocation.kt
@@ -40,7 +40,7 @@ enum class NoLookupLocation : LookupLocation {
     FROM_BACKEND,
     FROM_TEST,
     FROM_BUILTINS,
-    WHEN_CHECK_REDECLARATIONS,
+    WHEN_CHECK_DECLARATION_CONFLICTS,
     WHEN_CHECK_OVERRIDES,
     FOR_SCRIPT,
     FROM_REFLECTION,
diff --git a/idea/testData/checker/ExtensionFunctions.kt b/idea/testData/checker/ExtensionFunctions.kt
index 281d5fbb510..ad332cce69c 100644
--- a/idea/testData/checker/ExtensionFunctions.kt
+++ b/idea/testData/checker/ExtensionFunctions.kt
@@ -46,7 +46,7 @@ fun Int.foo() = this
           val foo : Int = 0
         }
 
-        <error>operator</error> fun Any.equals(<warning>other</warning> : Any?) : Boolean = true
+        <error>operator</error> fun Any.<warning>equals</warning>(<warning>other</warning> : Any?) : Boolean = true
         fun Any?.equals1(<warning>other</warning> : Any?) : Boolean = true
         fun Any.equals2(<warning>other</warning> : Any?) : Boolean = true
 
diff --git a/idea/testData/checker/regression/Jet69.kt b/idea/testData/checker/regression/Jet69.kt
index 2768b807251..a83894fbebe 100644
--- a/idea/testData/checker/regression/Jet69.kt
+++ b/idea/testData/checker/regression/Jet69.kt
@@ -2,7 +2,7 @@ class Command() {}
 
 fun parse(<warning>cmd</warning>: String): Command? { return null  }
 
-fun Any.equals(other : Any?) : Boolean = this === other
+fun Any.<warning>equals</warning>(other : Any?) : Boolean = this === other
 
 fun main(args: Array<String>) {
     val command = parse("")
diff --git a/idea/testData/checker/regression/SpecififcityByReceiver.kt b/idea/testData/checker/regression/SpecififcityByReceiver.kt
index 67d6776baba..5e1c2d4e331 100644
--- a/idea/testData/checker/regression/SpecififcityByReceiver.kt
+++ b/idea/testData/checker/regression/SpecififcityByReceiver.kt
@@ -1,4 +1,4 @@
-fun Any.equals(<warning>other</warning> : Any?) : Boolean = true
+fun Any.<warning>equals</warning>(<warning>other</warning> : Any?) : Boolean = true
 
 fun main(args: Array<String>) {