diff --git a/eval4j/src/org/jetbrains/eval4j/interpreter.kt b/eval4j/src/org/jetbrains/eval4j/interpreter.kt
index ad9bdd3c1d9..68863f8ad60 100644
--- a/eval4j/src/org/jetbrains/eval4j/interpreter.kt
+++ b/eval4j/src/org/jetbrains/eval4j/interpreter.kt
@@ -16,23 +16,16 @@
 
 package org.jetbrains.eval4j
 
-import org.jetbrains.org.objectweb.asm.tree.analysis.*
 import org.jetbrains.org.objectweb.asm.Handle
 import org.jetbrains.org.objectweb.asm.Opcodes.*
 import org.jetbrains.org.objectweb.asm.Type
-import org.jetbrains.org.objectweb.asm.tree.AbstractInsnNode
-import org.jetbrains.org.objectweb.asm.tree.FieldInsnNode
-import org.jetbrains.org.objectweb.asm.tree.IntInsnNode
-import org.jetbrains.org.objectweb.asm.tree.LdcInsnNode
-import org.jetbrains.org.objectweb.asm.tree.MethodInsnNode
-import org.jetbrains.org.objectweb.asm.tree.MultiANewArrayInsnNode
-import org.jetbrains.org.objectweb.asm.tree.TypeInsnNode
-import org.jetbrains.org.objectweb.asm.tree.JumpInsnNode
-import org.jetbrains.org.objectweb.asm.tree.IincInsnNode
+import org.jetbrains.org.objectweb.asm.tree.*
+import org.jetbrains.org.objectweb.asm.tree.analysis.AnalyzerException
+import org.jetbrains.org.objectweb.asm.tree.analysis.Interpreter
 
 class UnsupportedByteCodeException(message: String) : RuntimeException(message)
 
-public trait Eval {
+public interface Eval {
     public fun loadClass(classType: Type): Value
     public fun loadString(str: String): Value
     public fun newInstance(classType: Type): Value
@@ -97,7 +90,7 @@ class SingleInstructionInterpreter(private val eval: Eval) : Interpreter<Value>(
                     is Double -> double(cst)
                     is String -> eval.loadString(cst)
                     is Type -> {
-                        val sort = (cst as Type).getSort()
+                        val sort = cst.getSort()
                         when (sort) {
                             Type.OBJECT, Type.ARRAY -> eval.loadClass(cst)
                             Type.METHOD -> throw UnsupportedByteCodeException("Mothod handles are not supported")
diff --git a/eval4j/src/org/jetbrains/eval4j/interpreterLoop.kt b/eval4j/src/org/jetbrains/eval4j/interpreterLoop.kt
index 04451edaf53..233f8390ef2 100644
--- a/eval4j/src/org/jetbrains/eval4j/interpreterLoop.kt
+++ b/eval4j/src/org/jetbrains/eval4j/interpreterLoop.kt
@@ -24,7 +24,7 @@ import org.jetbrains.org.objectweb.asm.tree.analysis.Frame
 import org.jetbrains.org.objectweb.asm.util.Printer
 import java.util.ArrayList
 
-public trait InterpreterResult {
+public interface InterpreterResult {
     override fun toString(): String
 }
 
@@ -46,7 +46,7 @@ public class AbnormalTermination(public val message: String): InterpreterResult
     override fun toString(): String = "Terminated abnormally: $message"
 }
 
-public trait InterpretationEventHandler {
+public interface InterpretationEventHandler {
     object NONE : InterpretationEventHandler {
         override fun instructionProcessed(insn: AbstractInsnNode): InterpreterResult? = null
         override fun exceptionThrown(currentState: Frame<Value>, currentInsn: AbstractInsnNode, exception: Value): InterpreterResult? = null
@@ -80,7 +80,7 @@ public fun interpreterLoop(
     val firstInsn = m.instructions.getFirst()
     if (firstInsn == null) throw IllegalArgumentException("Empty method")
 
-    var currentInsn = firstInsn!!
+    var currentInsn = firstInsn
 
     fun goto(nextInsn: AbstractInsnNode?) {
         if (nextInsn == null) throw IllegalArgumentException("Instruction flow ended with no RETURN")
diff --git a/eval4j/src/org/jetbrains/eval4j/values.kt b/eval4j/src/org/jetbrains/eval4j/values.kt
index f7b79d68c35..dab6f43fe83 100644
--- a/eval4j/src/org/jetbrains/eval4j/values.kt
+++ b/eval4j/src/org/jetbrains/eval4j/values.kt
@@ -19,7 +19,7 @@ package org.jetbrains.eval4j
 import org.jetbrains.org.objectweb.asm.Type
 import org.jetbrains.org.objectweb.asm.tree.LabelNode
 
-public trait Value : org.jetbrains.org.objectweb.asm.tree.analysis.Value {
+public interface Value : org.jetbrains.org.objectweb.asm.tree.analysis.Value {
     public val asmType: Type
     public val valid: Boolean
     override fun getSize(): Int = asmType.getSize()
diff --git a/idea/ide-common/src/org/jetbrains/kotlin/idea/util/implicitReceiversUtils.kt b/idea/ide-common/src/org/jetbrains/kotlin/idea/util/implicitReceiversUtils.kt
index acf277e9f3b..4f6bdb4b995 100644
--- a/idea/ide-common/src/org/jetbrains/kotlin/idea/util/implicitReceiversUtils.kt
+++ b/idea/ide-common/src/org/jetbrains/kotlin/idea/util/implicitReceiversUtils.kt
@@ -53,7 +53,7 @@ public fun JetScope.getImplicitReceiversWithInstanceToExpression(): Map<Receiver
         val classDescriptor = current as? ClassDescriptor
         if (classDescriptor != null && !classDescriptor.isInner() && !DescriptorUtils.isLocal(classDescriptor)) break
 
-        current = current!!.getContainingDeclaration()
+        current = current.getContainingDeclaration()
     }
 
     val result = LinkedHashMap<ReceiverParameterDescriptor, ReceiverExpressionFactory?>()
diff --git a/idea/ide-common/src/org/jetbrains/kotlin/resolve/lazy/ProbablyNothingCallableNames.kt b/idea/ide-common/src/org/jetbrains/kotlin/resolve/lazy/ProbablyNothingCallableNames.kt
index e00bd451044..1b4df3ebdc1 100644
--- a/idea/ide-common/src/org/jetbrains/kotlin/resolve/lazy/ProbablyNothingCallableNames.kt
+++ b/idea/ide-common/src/org/jetbrains/kotlin/resolve/lazy/ProbablyNothingCallableNames.kt
@@ -16,7 +16,7 @@
 
 package org.jetbrains.kotlin.resolve.lazy
 
-public trait ProbablyNothingCallableNames {
+public interface ProbablyNothingCallableNames {
     public fun functionNames(): Collection<String>
     public fun propertyNames(): Collection<String>
 }
diff --git a/idea/idea-analysis/src/org/jetbrains/kotlin/idea/caches/resolve/KotlinResolveCache.kt b/idea/idea-analysis/src/org/jetbrains/kotlin/idea/caches/resolve/KotlinResolveCache.kt
index bea4defa543..26e696631cf 100644
--- a/idea/idea-analysis/src/org/jetbrains/kotlin/idea/caches/resolve/KotlinResolveCache.kt
+++ b/idea/idea-analysis/src/org/jetbrains/kotlin/idea/caches/resolve/KotlinResolveCache.kt
@@ -21,7 +21,6 @@ import com.intellij.openapi.project.DumbService
 import com.intellij.openapi.project.IndexNotReadyException
 import com.intellij.openapi.project.Project
 import com.intellij.psi.PsiElement
-import com.intellij.psi.PsiFile
 import com.intellij.psi.util.CachedValueProvider
 import com.intellij.psi.util.CachedValuesManager
 import com.intellij.psi.util.PsiModificationTracker
@@ -42,17 +41,12 @@ import org.jetbrains.kotlin.idea.project.TargetPlatform
 import org.jetbrains.kotlin.idea.project.TargetPlatformDetector
 import org.jetbrains.kotlin.psi.*
 import org.jetbrains.kotlin.resolve.*
-import org.jetbrains.kotlin.resolve.bindingContextUtil.getDataFlowInfo
-import org.jetbrains.kotlin.resolve.calls.smartcasts.DataFlowInfo
 import org.jetbrains.kotlin.resolve.lazy.BodyResolveMode
-import org.jetbrains.kotlin.resolve.lazy.descriptors.LazyClassDescriptor
-import org.jetbrains.kotlin.resolve.scopes.ChainedScope
-import org.jetbrains.kotlin.resolve.scopes.JetScope
 import org.jetbrains.kotlin.resolve.util.getScopeAndDataFlowForAnalyzeFragment
 import org.jetbrains.kotlin.types.TypeUtils
 import java.util.HashMap
 
-public trait CacheExtension<T> {
+public interface CacheExtension<T> {
     public val platform: TargetPlatform
     public fun getData(resolverProvider: ModuleResolverProvider): T
 }
@@ -129,8 +123,8 @@ private class PerFileAnalysisCache(val file: JetFile, val resolveSession: Resolv
                 descendantsOfCurrent.clear()
             }
 
-            descendantsOfCurrent.add(current!!)
-            current = current!!.getParent()
+            descendantsOfCurrent.add(current)
+            current = current.getParent()
         }
 
         cache.keySet().removeAll(toRemove)
diff --git a/idea/idea-analysis/src/org/jetbrains/kotlin/idea/caches/resolve/ModuleDependencyMapper.kt b/idea/idea-analysis/src/org/jetbrains/kotlin/idea/caches/resolve/ModuleDependencyMapper.kt
index 2c8295abc5b..1e4f214af81 100644
--- a/idea/idea-analysis/src/org/jetbrains/kotlin/idea/caches/resolve/ModuleDependencyMapper.kt
+++ b/idea/idea-analysis/src/org/jetbrains/kotlin/idea/caches/resolve/ModuleDependencyMapper.kt
@@ -111,7 +111,7 @@ private fun collectAllModuleInfosFromIdeaModel(project: Project): List<IdeaModul
     return collectAllModuleInfos
 }
 
-trait ModuleResolverProvider {
+interface ModuleResolverProvider {
     val exceptionTracker: ExceptionTracker
     fun resolverByModule(module: IdeaModuleInfo): ResolverForModule = resolverForProject.resolverForModule(module)
 
diff --git a/idea/idea-analysis/src/org/jetbrains/kotlin/idea/caches/resolve/ResolutionFacade.kt b/idea/idea-analysis/src/org/jetbrains/kotlin/idea/caches/resolve/ResolutionFacade.kt
index 042ef007f69..8552943d200 100644
--- a/idea/idea-analysis/src/org/jetbrains/kotlin/idea/caches/resolve/ResolutionFacade.kt
+++ b/idea/idea-analysis/src/org/jetbrains/kotlin/idea/caches/resolve/ResolutionFacade.kt
@@ -28,7 +28,7 @@ import org.jetbrains.kotlin.resolve.BindingContext
 import org.jetbrains.kotlin.resolve.lazy.BodyResolveMode
 import org.jetbrains.kotlin.resolve.scopes.JetScope
 
-public trait ResolutionFacade {
+public interface ResolutionFacade {
 
     public fun analyze(element: JetElement, bodyResolveMode: BodyResolveMode = BodyResolveMode.FULL): BindingContext
 
diff --git a/idea/idea-analysis/src/org/jetbrains/kotlin/idea/caches/resolve/cacheUtils.kt b/idea/idea-analysis/src/org/jetbrains/kotlin/idea/caches/resolve/cacheUtils.kt
index 8cad566f8f5..c3abb8e7231 100644
--- a/idea/idea-analysis/src/org/jetbrains/kotlin/idea/caches/resolve/cacheUtils.kt
+++ b/idea/idea-analysis/src/org/jetbrains/kotlin/idea/caches/resolve/cacheUtils.kt
@@ -28,7 +28,7 @@ class SynchronizedCachedValue<V>(project: Project, provider: () -> CachedValuePr
 
     public fun getValue(): V {
         return synchronized(cachedValue) {
-            cachedValue.getValue() as V
+            cachedValue.getValue()
         }
     }
 }
diff --git a/idea/idea-analysis/src/org/jetbrains/kotlin/idea/codeInsight/shorten/shortenWaitingSet.kt b/idea/idea-analysis/src/org/jetbrains/kotlin/idea/codeInsight/shorten/shortenWaitingSet.kt
index dff45f60ff3..ab5c5a24626 100644
--- a/idea/idea-analysis/src/org/jetbrains/kotlin/idea/codeInsight/shorten/shortenWaitingSet.kt
+++ b/idea/idea-analysis/src/org/jetbrains/kotlin/idea/codeInsight/shorten/shortenWaitingSet.kt
@@ -59,7 +59,7 @@ private fun Project.getOrCreateElementsToShorten(): MutableSet<ShorteningRequest
         elementsToShorten = elements
     }
 
-    return elements!!
+    return elements
 }
 
 public fun JetElement.addToShorteningWaitSet(options: Options = Options.DEFAULT) {
diff --git a/idea/idea-analysis/src/org/jetbrains/kotlin/idea/decompiler/KotlinClsFileBase.kt b/idea/idea-analysis/src/org/jetbrains/kotlin/idea/decompiler/KotlinClsFileBase.kt
index 7f1f500dd35..f1ab8003f33 100644
--- a/idea/idea-analysis/src/org/jetbrains/kotlin/idea/decompiler/KotlinClsFileBase.kt
+++ b/idea/idea-analysis/src/org/jetbrains/kotlin/idea/decompiler/KotlinClsFileBase.kt
@@ -17,10 +17,8 @@
 package org.jetbrains.kotlin.idea.decompiler
 
 import com.intellij.openapi.util.TextRange
-import com.intellij.psi.FileViewProvider
 import com.intellij.psi.util.PsiTreeUtil
 import org.jetbrains.annotations.TestOnly
-import org.jetbrains.kotlin.descriptors.CallableDescriptor
 import org.jetbrains.kotlin.descriptors.ConstructorDescriptor
 import org.jetbrains.kotlin.descriptors.DeclarationDescriptor
 import org.jetbrains.kotlin.descriptors.ValueParameterDescriptor
@@ -39,7 +37,7 @@ public abstract class KotlinClsFileBase(val provider: KotlinClassFileViewProvide
         val original = descriptor.getOriginal()
 
         if (original is ValueParameterDescriptor) {
-            val callable = original.getContainingDeclaration() as? CallableDescriptor ?: return null
+            val callable = original.getContainingDeclaration()
             val callableDeclaration = getDeclarationForDescriptor(callable) as? JetCallableDeclaration ?: return null
             return callableDeclaration.getValueParameters()[original.getIndex()]
         }
diff --git a/idea/idea-analysis/src/org/jetbrains/kotlin/idea/decompiler/stubBuilder/ClassClsStubBuilder.kt b/idea/idea-analysis/src/org/jetbrains/kotlin/idea/decompiler/stubBuilder/ClassClsStubBuilder.kt
index a68424c06a1..9a1abf5eed5 100644
--- a/idea/idea-analysis/src/org/jetbrains/kotlin/idea/decompiler/stubBuilder/ClassClsStubBuilder.kt
+++ b/idea/idea-analysis/src/org/jetbrains/kotlin/idea/decompiler/stubBuilder/ClassClsStubBuilder.kt
@@ -107,7 +107,7 @@ private class ClassClsStubBuilder(
         val superTypeRefs = supertypeIds.filterNot {
             //TODO: filtering function types should go away
             KotlinBuiltIns.isNumberedFunctionClassFqName(it.asSingleFqName().toUnsafe())
-        }.map { it.getShortClassName().ref()!! }.toTypedArray()
+        }.map { it.getShortClassName().ref() }.toTypedArray()
         return when (classKind) {
             ProtoBuf.Class.Kind.OBJECT, ProtoBuf.Class.Kind.CLASS_OBJECT -> {
                 KotlinObjectStubImpl(
diff --git a/idea/idea-analysis/src/org/jetbrains/kotlin/idea/decompiler/stubBuilder/ClsStubBuilderContext.kt b/idea/idea-analysis/src/org/jetbrains/kotlin/idea/decompiler/stubBuilder/ClsStubBuilderContext.kt
index 69dde295f70..1d19cf14dce 100644
--- a/idea/idea-analysis/src/org/jetbrains/kotlin/idea/decompiler/stubBuilder/ClsStubBuilderContext.kt
+++ b/idea/idea-analysis/src/org/jetbrains/kotlin/idea/decompiler/stubBuilder/ClsStubBuilderContext.kt
@@ -23,12 +23,11 @@ import org.jetbrains.kotlin.name.ClassId
 import org.jetbrains.kotlin.name.FqName
 import org.jetbrains.kotlin.name.Name
 import org.jetbrains.kotlin.serialization.ProtoBuf
+import org.jetbrains.kotlin.serialization.deserialization.AnnotationAndConstantLoader
 import org.jetbrains.kotlin.serialization.deserialization.ClassDataFinder
 import org.jetbrains.kotlin.serialization.deserialization.ErrorReporter
 import org.jetbrains.kotlin.serialization.deserialization.NameResolver
 import org.jetbrains.kotlin.storage.LockBasedStorageManager
-import org.jetbrains.kotlin.load.kotlin.KotlinJvmBinaryClass
-import org.jetbrains.kotlin.serialization.deserialization.AnnotationAndConstantLoader
 
 class ClsStubBuilderComponents(
         val classDataFinder: ClassDataFinder,
@@ -42,7 +41,7 @@ class ClsStubBuilderComponents(
     }
 }
 
-trait TypeParameters {
+interface TypeParameters {
     fun get(id: Int): Name
 
     fun child(nameResolver: NameResolver, innerTypeParameters: List<ProtoBuf.TypeParameter>)
diff --git a/idea/idea-analysis/src/org/jetbrains/kotlin/idea/decompiler/stubBuilder/TypeClsStubBuilder.kt b/idea/idea-analysis/src/org/jetbrains/kotlin/idea/decompiler/stubBuilder/TypeClsStubBuilder.kt
index 61cc3156c56..66ae2034b30 100644
--- a/idea/idea-analysis/src/org/jetbrains/kotlin/idea/decompiler/stubBuilder/TypeClsStubBuilder.kt
+++ b/idea/idea-analysis/src/org/jetbrains/kotlin/idea/decompiler/stubBuilder/TypeClsStubBuilder.kt
@@ -216,7 +216,7 @@ class TypeClsStubBuilder(private val c: ClsStubBuilderContext) {
         val typeConstraintListStub = KotlinPlaceHolderStubImpl<JetTypeConstraintList>(parent, JetStubElementTypes.TYPE_CONSTRAINT_LIST)
         for ((name, type) in protosForTypeConstraintList) {
             val typeConstraintStub = KotlinPlaceHolderStubImpl<JetTypeConstraint>(typeConstraintListStub, JetStubElementTypes.TYPE_CONSTRAINT)
-            KotlinNameReferenceExpressionStubImpl(typeConstraintStub, name.ref()!!)
+            KotlinNameReferenceExpressionStubImpl(typeConstraintStub, name.ref())
             createTypeReferenceStub(typeConstraintStub, type)
         }
     }
diff --git a/idea/idea-analysis/src/org/jetbrains/kotlin/idea/decompiler/textBuilder/ResolverForDecompiler.kt b/idea/idea-analysis/src/org/jetbrains/kotlin/idea/decompiler/textBuilder/ResolverForDecompiler.kt
index 94a2068b2c3..6299d4a1df5 100644
--- a/idea/idea-analysis/src/org/jetbrains/kotlin/idea/decompiler/textBuilder/ResolverForDecompiler.kt
+++ b/idea/idea-analysis/src/org/jetbrains/kotlin/idea/decompiler/textBuilder/ResolverForDecompiler.kt
@@ -21,7 +21,7 @@ import org.jetbrains.kotlin.descriptors.ClassDescriptor
 import org.jetbrains.kotlin.descriptors.DeclarationDescriptor
 import org.jetbrains.kotlin.name.ClassId
 
-public trait ResolverForDecompiler {
+public interface ResolverForDecompiler {
     public fun resolveTopLevelClass(classId: ClassId): ClassDescriptor?
 
     public fun resolveDeclarationsInPackage(packageFqName: FqName): Collection<DeclarationDescriptor>
diff --git a/idea/idea-analysis/src/org/jetbrains/kotlin/idea/highlighter/HtmlTabledDescriptorRenderer.java b/idea/idea-analysis/src/org/jetbrains/kotlin/idea/highlighter/HtmlTabledDescriptorRenderer.java
index 01c97d182ec..53f9e76fe82 100644
--- a/idea/idea-analysis/src/org/jetbrains/kotlin/idea/highlighter/HtmlTabledDescriptorRenderer.java
+++ b/idea/idea-analysis/src/org/jetbrains/kotlin/idea/highlighter/HtmlTabledDescriptorRenderer.java
@@ -173,7 +173,7 @@ public class HtmlTabledDescriptorRenderer extends TabledDescriptorRenderer {
 
         @Override
         public void appendAfterValueParameter(@NotNull ValueParameterDescriptor parameter, @NotNull StringBuilder builder) {
-            boolean last = ((FunctionDescriptor) parameter.getContainingDeclaration()).getValueParameters().size() - 1 == parameter.getIndex();
+            boolean last = parameter.getContainingDeclaration().getValueParameters().size() - 1 == parameter.getIndex();
             if (!last) {
                 builder.append(",");
             }
diff --git a/idea/idea-analysis/src/org/jetbrains/kotlin/idea/highlighter/KotlinSuppressableWarningProblemGroup.kt b/idea/idea-analysis/src/org/jetbrains/kotlin/idea/highlighter/KotlinSuppressableWarningProblemGroup.kt
index 041030aff2c..4988b5af9cc 100644
--- a/idea/idea-analysis/src/org/jetbrains/kotlin/idea/highlighter/KotlinSuppressableWarningProblemGroup.kt
+++ b/idea/idea-analysis/src/org/jetbrains/kotlin/idea/highlighter/KotlinSuppressableWarningProblemGroup.kt
@@ -16,16 +16,16 @@
 
 package org.jetbrains.kotlin.idea.highlighter
 
+import com.intellij.codeInspection.SuppressIntentionAction
 import com.intellij.codeInspection.SuppressableProblemGroup
 import com.intellij.psi.PsiElement
-import com.intellij.codeInspection.SuppressIntentionAction
+import org.jetbrains.kotlin.diagnostics.DiagnosticFactory
 import org.jetbrains.kotlin.diagnostics.Severity
-import java.util.Collections
+import org.jetbrains.kotlin.idea.quickfix.AnnotationHostKind
 import org.jetbrains.kotlin.idea.quickfix.KotlinSuppressIntentionAction
 import org.jetbrains.kotlin.psi.*
-import org.jetbrains.kotlin.idea.quickfix.AnnotationHostKind
-import org.jetbrains.kotlin.diagnostics.DiagnosticFactory
 import org.jetbrains.kotlin.psi.psiUtil.getStrictParentOfType
+import java.util.Collections
 
 class KotlinSuppressableWarningProblemGroup(
         private val diagnosticFactory: DiagnosticFactory<*>
@@ -55,7 +55,7 @@ fun createSuppressWarningActions(element: PsiElement, diagnosticFactory: Diagnos
     var suppressAtStatementAllowed = true
     while (current != null) {
         if (current is JetDeclaration) {
-            val declaration = current as JetDeclaration
+            val declaration = current
             val kind = DeclarationKindDetector.detect(declaration)
             if (kind != null) {
                 actions.add(KotlinSuppressIntentionAction(declaration, diagnosticFactory, kind))
@@ -64,15 +64,14 @@ fun createSuppressWarningActions(element: PsiElement, diagnosticFactory: Diagnos
         }
         else if (current is JetExpression && suppressAtStatementAllowed) {
             // Add suppress action at first statement
-            if ((current as PsiElement).getParent() is JetBlockExpression) {
-                val expression = current as JetExpression
-                actions.add(KotlinSuppressIntentionAction(expression, diagnosticFactory,
+            if (current.getParent() is JetBlockExpression) {
+                actions.add(KotlinSuppressIntentionAction(current, diagnosticFactory,
                                                           AnnotationHostKind("statement", "", true)))
                 suppressAtStatementAllowed = false
             }
         }
 
-        current = current?.getParent()
+        current = current.getParent()
     }
     return actions
 }
diff --git a/idea/idea-analysis/src/org/jetbrains/kotlin/idea/search/declarationsSearch/declarationSearchUtil.kt b/idea/idea-analysis/src/org/jetbrains/kotlin/idea/search/declarationsSearch/declarationSearchUtil.kt
index 6788d61c831..89ca829738d 100644
--- a/idea/idea-analysis/src/org/jetbrains/kotlin/idea/search/declarationsSearch/declarationSearchUtil.kt
+++ b/idea/idea-analysis/src/org/jetbrains/kotlin/idea/search/declarationsSearch/declarationSearchUtil.kt
@@ -29,12 +29,12 @@ import java.util.HashSet
 import com.intellij.openapi.progress.ProgressIndicatorProvider
 import org.jetbrains.kotlin.psi.psiUtil.contains
 
-trait DeclarationSearchRequest<in T> {
+interface DeclarationSearchRequest<in T> {
     val project: Project
     val searchScope: SearchScope
 }
 
-public trait SearchRequestWithElement<T : PsiElement> : DeclarationSearchRequest<T> {
+public interface SearchRequestWithElement<T : PsiElement> : DeclarationSearchRequest<T> {
     val originalElement: T
     override val project: Project get() = originalElement.getProject()
 }
@@ -65,7 +65,7 @@ public class HierarchySearchRequest<T: PsiElement> (
             HierarchySearchRequest(newOriginalElement, searchScope, searchDeeply)
 }
 
-trait HierarchyTraverser<T> {
+interface HierarchyTraverser<T> {
     protected fun nextElements(current: T): Iterable<T>
     protected fun shouldDescend(element: T): Boolean
 
diff --git a/idea/idea-analysis/src/org/jetbrains/kotlin/idea/search/usagesSearch/searchHelpers.kt b/idea/idea-analysis/src/org/jetbrains/kotlin/idea/search/usagesSearch/searchHelpers.kt
index dc4439c4ec4..e215a6c39bd 100644
--- a/idea/idea-analysis/src/org/jetbrains/kotlin/idea/search/usagesSearch/searchHelpers.kt
+++ b/idea/idea-analysis/src/org/jetbrains/kotlin/idea/search/usagesSearch/searchHelpers.kt
@@ -16,29 +16,29 @@
 
 package org.jetbrains.kotlin.idea.search.usagesSearch
 
-import com.intellij.psi.PsiReference
-import org.jetbrains.kotlin.idea.search.usagesSearch.*
-import org.jetbrains.kotlin.idea.search.usagesSearch.UsagesSearchFilter.*
-import java.util.Collections
-import java.util.ArrayList
 import com.intellij.psi.PsiNamedElement
+import com.intellij.psi.PsiReference
 import com.intellij.util.Processor
+import com.intellij.util.containers.ContainerUtil
 import org.jetbrains.kotlin.asJava.LightClassUtil
 import org.jetbrains.kotlin.asJava.LightClassUtil.PropertyAccessorsPsiMethods
-import org.jetbrains.kotlin.psi.psiUtil.*
-import org.jetbrains.kotlin.name.Name
-import org.jetbrains.kotlin.lexer.JetSingleValueToken
-import org.jetbrains.kotlin.resolve.BindingContext
 import org.jetbrains.kotlin.descriptors.ValueParameterDescriptor
-import org.jetbrains.kotlin.lexer.JetTokens
-import org.jetbrains.kotlin.idea.references.*
-import com.intellij.util.containers.ContainerUtil
 import org.jetbrains.kotlin.idea.caches.resolve.analyze
-import org.jetbrains.kotlin.idea.caches.resolve.analyzeFully
+import org.jetbrains.kotlin.idea.references.matchesTarget
+import org.jetbrains.kotlin.idea.search.usagesSearch.UsagesSearchFilter.False
+import org.jetbrains.kotlin.idea.search.usagesSearch.UsagesSearchFilter.True
+import org.jetbrains.kotlin.lexer.JetSingleValueToken
+import org.jetbrains.kotlin.lexer.JetTokens
+import org.jetbrains.kotlin.name.Name
 import org.jetbrains.kotlin.psi.*
-import org.jetbrains.kotlin.resolve.calls.callUtil.getResolvedCall
+import org.jetbrains.kotlin.psi.psiUtil.effectiveDeclarations
+import org.jetbrains.kotlin.psi.psiUtil.getNonStrictParentOfType
+import org.jetbrains.kotlin.psi.psiUtil.getStrictParentOfType
+import org.jetbrains.kotlin.resolve.BindingContext
 import org.jetbrains.kotlin.resolve.scopes.receivers.ClassReceiver
 import org.jetbrains.kotlin.utils.addToStdlib.singletonOrEmptyList
+import java.util.ArrayList
+import java.util.Collections
 
 val isTargetUsage = (PsiReference::matchesTarget).searchFilter
 
@@ -130,7 +130,7 @@ public abstract class UsagesSearchHelper<T : PsiNamedElement> {
 
 val isNotImportUsage = !((PsiReference::isImportUsage).searchFilter)
 
-trait ImportAwareSearchHelper {
+interface ImportAwareSearchHelper {
     public val skipImports: Boolean
 
     protected val isFilteredImport: UsagesSearchFilter
@@ -206,7 +206,7 @@ class ClassDeclarationsUsagesSearchHelper(
 
 val isOverrideUsage = (PsiReference::isCallableOverrideUsage).searchFilter
 
-trait OverrideSearchHelper {
+interface OverrideSearchHelper {
     public val selfUsages: Boolean
     public val overrideUsages: Boolean
 
diff --git a/idea/idea-analysis/src/org/jetbrains/kotlin/idea/search/usagesSearch/usagesSearch.kt b/idea/idea-analysis/src/org/jetbrains/kotlin/idea/search/usagesSearch/usagesSearch.kt
index e7431fc9b94..02e034d2e5f 100644
--- a/idea/idea-analysis/src/org/jetbrains/kotlin/idea/search/usagesSearch/usagesSearch.kt
+++ b/idea/idea-analysis/src/org/jetbrains/kotlin/idea/search/usagesSearch/usagesSearch.kt
@@ -88,7 +88,7 @@ public data class UsagesSearchTarget<out T : PsiElement>(
         get() = if (restrictByTargetScope) scope and element.effectiveScope else scope
 }
 
-public trait UsagesSearchFilter {
+public interface UsagesSearchFilter {
     object False: UsagesSearchFilter {
         override fun accepts(ref: PsiReference, item: UsagesSearchRequestItem): Boolean = false
     }
diff --git a/idea/idea-analysis/src/org/jetbrains/kotlin/plugin/references/SimpleNameReferenceExtension.kt b/idea/idea-analysis/src/org/jetbrains/kotlin/plugin/references/SimpleNameReferenceExtension.kt
index 00ddf46edf1..94b1739602a 100644
--- a/idea/idea-analysis/src/org/jetbrains/kotlin/plugin/references/SimpleNameReferenceExtension.kt
+++ b/idea/idea-analysis/src/org/jetbrains/kotlin/plugin/references/SimpleNameReferenceExtension.kt
@@ -21,7 +21,7 @@ import org.jetbrains.kotlin.idea.references.JetSimpleNameReference
 import com.intellij.psi.PsiElement
 import org.jetbrains.kotlin.psi.JetPsiFactory
 
-public trait SimpleNameReferenceExtension {
+public interface SimpleNameReferenceExtension {
     companion object {
         public val EP_NAME: ExtensionPointName<SimpleNameReferenceExtension> = ExtensionPointName.create("org.jetbrains.kotlin.simpleNameReferenceExtension")!!
     }