code cleanup: core modules

core/descriptor.loader.java/src/org/jetbrains/kotlin/load/java/components/SamConversionResolver.kt

@@ -24,7 +24,7 @@ import org.jetbrains.kotlin.name.Name
 import org.jetbrains.kotlin.resolve.scopes.JetScope
 import org.jetbrains.kotlin.types.JetType
 
-public trait SamConversionResolver {
+public interface SamConversionResolver {
     public companion object EMPTY : SamConversionResolver {
         override fun <D : FunctionDescriptor> resolveSamAdapter(original: D) = null
         override fun resolveSamConstructor(name: Name, scope: JetScope) = null

core/descriptor.loader.java/src/org/jetbrains/kotlin/load/java/lazy/ModuleClassResolver.kt

@@ -23,7 +23,7 @@ import org.jetbrains.kotlin.descriptors.ClassDescriptor
 import kotlin.properties.Delegates
 import javax.inject.Inject
 
-public trait ModuleClassResolver {
+public interface ModuleClassResolver {
     public fun resolveClass(javaClass: JavaClass): ClassDescriptor?
 }
 

core/descriptor.loader.java/src/org/jetbrains/kotlin/load/java/lazy/descriptors/LazyJavaPackageFragment.kt

@@ -16,16 +16,15 @@
 
 package org.jetbrains.kotlin.load.java.lazy.descriptors
 
+import org.jetbrains.kotlin.descriptors.impl.PackageFragmentDescriptorImpl
 import org.jetbrains.kotlin.load.java.lazy.LazyJavaResolverContext
 import org.jetbrains.kotlin.load.java.structure.JavaPackage
-import org.jetbrains.kotlin.descriptors.impl.PackageFragmentDescriptorImpl
-import kotlin.properties.Delegates
 
 class LazyJavaPackageFragment(
         private val c: LazyJavaResolverContext,
         private val jPackage: JavaPackage
 ) : PackageFragmentDescriptorImpl(c.module, jPackage.getFqName()) {
-    private val scope by Delegates.lazy { LazyPackageFragmentScopeForJavaPackage(c, jPackage, this) }
+    private val scope by lazy { LazyPackageFragmentScopeForJavaPackage(c, jPackage, this) }
 
     override fun getMemberScope() = scope
 

core/descriptor.loader.java/src/org/jetbrains/kotlin/load/java/lazy/descriptors/MemberIndex.kt

@@ -22,7 +22,7 @@ import org.jetbrains.kotlin.load.java.components.DescriptorResolverUtils
 import org.jetbrains.kotlin.utils.valuesToMap
 import java.util.HashSet
 
-trait MemberIndex {
+interface MemberIndex {
     fun findMethodsByName(name: Name): Collection<JavaMethod>
     fun getMethodNames(nameFilter: (Name) -> Boolean): Collection<Name>
 

core/descriptor.loader.java/src/org/jetbrains/kotlin/load/java/lazy/resolvers.kt

@@ -29,11 +29,11 @@ import org.jetbrains.kotlin.name.ClassId
 import org.jetbrains.kotlin.utils.mapToIndex
 
 //TODO: (module refactoring) usages of this interface should be replaced by ModuleClassResolver
-trait LazyJavaClassResolver {
+interface LazyJavaClassResolver {
     fun resolveClass(javaClass: JavaClass): ClassDescriptor?
 }
 
-trait TypeParameterResolver {
+interface TypeParameterResolver {
     object EMPTY : TypeParameterResolver {
         override fun resolveTypeParameter(javaTypeParameter: JavaTypeParameter): TypeParameterDescriptor? = null
     }

core/descriptor.loader.java/src/org/jetbrains/kotlin/load/java/lazy/types/LazyJavaTypeResolver.kt

@@ -347,7 +347,7 @@ class LazyJavaTypeResolver(
 
 }
 
-trait JavaTypeAttributes {
+interface JavaTypeAttributes {
     val howThisTypeIsUsed: TypeUsage
     val howThisTypeIsUsedAccordingToAnnotations: TypeUsage
     val isMarkedNotNull: Boolean

core/descriptor.loader.java/src/org/jetbrains/kotlin/load/java/sources/JavaSourceElementFactory.kt

@@ -19,10 +19,10 @@ package org.jetbrains.kotlin.load.java.sources
 import org.jetbrains.kotlin.load.java.structure.JavaElement
 import org.jetbrains.kotlin.descriptors.SourceElement
 
-public trait JavaSourceElementFactory {
+public interface JavaSourceElementFactory {
     public fun source(javaElement: JavaElement): JavaSourceElement
 }
 
-public trait JavaSourceElement: SourceElement {
+public interface JavaSourceElement: SourceElement {
     public val javaElement: JavaElement
 }

core/descriptor.loader.java/src/org/jetbrains/kotlin/load/java/structure/JavaPackage.kt

@@ -19,7 +19,7 @@ package org.jetbrains.kotlin.load.java.structure
 import org.jetbrains.kotlin.name.FqName
 import org.jetbrains.kotlin.name.Name
 
-public trait JavaPackage : JavaElement {
+public interface JavaPackage : JavaElement {
     public fun getClasses(nameFilter: (Name) -> Boolean): Collection<JavaClass>
 
     public fun getSubPackages(): Collection<JavaPackage>

core/descriptor.loader.java/src/org/jetbrains/kotlin/load/java/structure/annotationArguments.kt

@@ -18,26 +18,26 @@ package org.jetbrains.kotlin.load.java.structure
 
 import org.jetbrains.kotlin.name.Name
 
-public trait JavaAnnotationArgument {
+public interface JavaAnnotationArgument {
     public val name: Name?
 }
 
-public trait JavaLiteralAnnotationArgument : JavaAnnotationArgument {
+public interface JavaLiteralAnnotationArgument : JavaAnnotationArgument {
     public val value: Any?
 }
 
-public trait JavaArrayAnnotationArgument : JavaAnnotationArgument {
+public interface JavaArrayAnnotationArgument : JavaAnnotationArgument {
     public fun getElements(): List<JavaAnnotationArgument>
 }
 
-public trait JavaEnumValueAnnotationArgument : JavaAnnotationArgument {
+public interface JavaEnumValueAnnotationArgument : JavaAnnotationArgument {
     public fun resolve(): JavaField?
 }
 
-public trait JavaClassObjectAnnotationArgument : JavaAnnotationArgument {
+public interface JavaClassObjectAnnotationArgument : JavaAnnotationArgument {
     public fun getReferencedType(): JavaType
 }
 
-public trait JavaAnnotationAsAnnotationArgument : JavaAnnotationArgument {
+public interface JavaAnnotationAsAnnotationArgument : JavaAnnotationArgument {
     public fun getAnnotation(): JavaAnnotation
 }

core/descriptor.loader.java/src/org/jetbrains/kotlin/load/kotlin/KotlinClassFinder.kt

@@ -19,7 +19,7 @@ package org.jetbrains.kotlin.load.kotlin
 import org.jetbrains.kotlin.load.java.structure.JavaClass
 import org.jetbrains.kotlin.name.ClassId
 
-public trait KotlinClassFinder {
+public interface KotlinClassFinder {
     public fun findKotlinClass(classId: ClassId): KotlinJvmBinaryClass?
 
     public fun findKotlinClass(javaClass: JavaClass): KotlinJvmBinaryClass?

core/descriptors.runtime/src/org/jetbrains/kotlin/load/java/structure/reflect/ReflectJavaAnnotationOwner.kt

@@ -20,7 +20,7 @@ import org.jetbrains.kotlin.load.java.structure.JavaAnnotationOwner
 import org.jetbrains.kotlin.name.FqName
 import java.lang.reflect.AnnotatedElement
 
-public trait ReflectJavaAnnotationOwner : JavaAnnotationOwner {
+public interface ReflectJavaAnnotationOwner : JavaAnnotationOwner {
     val element: AnnotatedElement
 
     override fun getAnnotations() = getAnnotations(element.getDeclaredAnnotations())

core/descriptors.runtime/src/org/jetbrains/kotlin/load/java/structure/reflect/ReflectJavaModifierListOwner.kt

@@ -21,7 +21,7 @@ import org.jetbrains.kotlin.load.java.JavaVisibilities
 import org.jetbrains.kotlin.load.java.structure.JavaModifierListOwner
 import java.lang.reflect.Modifier
 
-public trait ReflectJavaModifierListOwner : JavaModifierListOwner {
+public interface ReflectJavaModifierListOwner : JavaModifierListOwner {
     /* protected // KT-3029 */ val modifiers: Int
 
     override fun isAbstract() = Modifier.isAbstract(modifiers)

core/descriptors/src/org/jetbrains/kotlin/descriptors/ModuleDescriptor.kt

@@ -23,7 +23,7 @@ import org.jetbrains.kotlin.platform.PlatformToKotlinClassMap
 import org.jetbrains.kotlin.resolve.ImportPath
 import org.jetbrains.kotlin.types.TypeSubstitutor
 
-public trait ModuleDescriptor : DeclarationDescriptor, ModuleParameters {
+public interface ModuleDescriptor : DeclarationDescriptor, ModuleParameters {
     override fun getContainingDeclaration(): DeclarationDescriptor? = null
 
     public val builtIns: KotlinBuiltIns
@@ -43,7 +43,7 @@ public trait ModuleDescriptor : DeclarationDescriptor, ModuleParameters {
     public fun getSubPackagesOf(fqName: FqName, nameFilter: (Name) -> Boolean): Collection<FqName>
 }
 
-trait ModuleParameters {
+interface ModuleParameters {
     public val defaultImports: List<ImportPath>
     public val platformToKotlinClassMap: PlatformToKotlinClassMap
 

core/descriptors/src/org/jetbrains/kotlin/descriptors/PackageFragmentDescriptor.kt

@@ -19,7 +19,7 @@ package org.jetbrains.kotlin.descriptors
 import org.jetbrains.kotlin.name.FqName
 import org.jetbrains.kotlin.resolve.scopes.JetScope
 
-public trait PackageFragmentDescriptor : ClassOrPackageFragmentDescriptor {
+public interface PackageFragmentDescriptor : ClassOrPackageFragmentDescriptor {
 
     override fun getContainingDeclaration(): ModuleDescriptor
 

core/descriptors/src/org/jetbrains/kotlin/descriptors/PackageFragmentProvider.kt

@@ -19,7 +19,7 @@ package org.jetbrains.kotlin.descriptors
 import org.jetbrains.kotlin.name.FqName
 import org.jetbrains.kotlin.name.Name
 
-public trait PackageFragmentProvider {
+public interface PackageFragmentProvider {
     public fun getPackageFragments(fqName: FqName): List<PackageFragmentDescriptor>
 
     public fun getSubPackagesOf(fqName: FqName, nameFilter: (Name) -> Boolean): Collection<FqName>

core/descriptors/src/org/jetbrains/kotlin/descriptors/annotations/Annotations.kt

@@ -19,7 +19,7 @@ package org.jetbrains.kotlin.descriptors.annotations
 import org.jetbrains.kotlin.name.FqName
 import org.jetbrains.kotlin.resolve.DescriptorUtils
 
-public trait Annotations : Iterable<AnnotationDescriptor> {
+public interface Annotations : Iterable<AnnotationDescriptor> {
 
     public fun isEmpty(): Boolean
 
@@ -54,7 +54,7 @@ class FilteredAnnotations(
             if (fqNameFilter(fqName)) delegate.findExternalAnnotation(fqName)
             else null
 
-    override fun iterator() = delegate.sequence()
+    override fun iterator() = delegate.asSequence()
             .filter { annotation ->
                 val descriptor = annotation.getType().getConstructor().getDeclarationDescriptor()
                 descriptor != null && DescriptorUtils.getFqName(descriptor).let { fqName ->

core/descriptors/src/org/jetbrains/kotlin/descriptors/impl/ModuleDescriptorImpl.kt

@@ -27,7 +27,6 @@ import org.jetbrains.kotlin.name.Name
 import org.jetbrains.kotlin.storage.StorageManager
 import org.jetbrains.kotlin.utils.sure
 import java.util.LinkedHashSet
-import kotlin.properties.Delegates
 
 public class ModuleDescriptorImpl(
         moduleName: Name,
@@ -56,7 +55,7 @@ public class ModuleDescriptorImpl(
         return packageFragmentProvider.getSubPackagesOf(fqName, nameFilter)
     }
 
-    private val packageFragmentProviderForWholeModuleWithDependencies by Delegates.lazy {
+    private val packageFragmentProviderForWholeModuleWithDependencies by lazy {
         val moduleDependencies = dependencies.sure { "Dependencies of module $id were not set before querying module content" }
         val dependenciesDescriptors = moduleDependencies.descriptors
         assert(this in dependenciesDescriptors) { "Module ${id} is not contained in his own dependencies, this is probably a misconfiguration" }

core/descriptors/src/org/jetbrains/kotlin/descriptors/impl/PackageFragmentDescriptorImpl.kt

@@ -29,7 +29,7 @@ public abstract class PackageFragmentDescriptorImpl(
     override fun substitute(substitutor: TypeSubstitutor): DeclarationDescriptor? = this
 
     override fun <R, D> accept(visitor: DeclarationDescriptorVisitor<R, D>, data: D): R =
-            visitor.visitPackageFragmentDescriptor(this, data) as R
+            visitor.visitPackageFragmentDescriptor(this, data)
 
     override fun getContainingDeclaration(): ModuleDescriptor {
         return super<DeclarationDescriptorNonRootImpl>.getContainingDeclaration() as ModuleDescriptor

core/descriptors/src/org/jetbrains/kotlin/resolve/DescriptorUtils.kt

@@ -82,7 +82,7 @@ public val DeclarationDescriptorWithVisibility.isEffectivelyPublicApi: Boolean
         var parent: DeclarationDescriptorWithVisibility? = this
 
         while (parent != null) {
-            if (!parent!!.getVisibility().isPublicAPI()) return false
+            if (!parent.getVisibility().isPublicAPI()) return false
 
             parent = DescriptorUtils.getParentOfType(parent, javaClass<DeclarationDescriptorWithVisibility>())
         }

core/descriptors/src/org/jetbrains/kotlin/resolve/calls/inference/ConstraintPosition.kt

@@ -39,7 +39,7 @@ public enum class ConstraintPositionKind {
     }
 }
 
-public trait ConstraintPosition {
+public interface ConstraintPosition {
     val kind: ConstraintPositionKind
 
     fun isStrong(): Boolean = kind != TYPE_BOUND_POSITION

core/descriptors/src/org/jetbrains/kotlin/resolve/calls/inference/ConstraintSystem.kt

@@ -22,7 +22,7 @@ import org.jetbrains.kotlin.types.JetType
 import org.jetbrains.kotlin.types.TypeSubstitutor
 import org.jetbrains.kotlin.types.Variance
 
-public trait ConstraintSystem {
+public interface ConstraintSystem {
 
     /**
      * Registers variables in a constraint system.

core/descriptors/src/org/jetbrains/kotlin/resolve/calls/inference/ConstraintSystemStatus.kt

@@ -18,7 +18,7 @@ package org.jetbrains.kotlin.resolve.calls.inference
 
 import org.jetbrains.kotlin.resolve.calls.inference.constraintPosition.ConstraintPositionKind
 
-public trait ConstraintSystemStatus {
+public interface ConstraintSystemStatus {
     /**
      * Returns <tt>true</tt> if constraint system has a solution (has no contradiction and has enough information to infer each registered type variable).
      */

core/descriptors/src/org/jetbrains/kotlin/resolve/calls/inference/TypeBounds.kt

@@ -25,7 +25,7 @@ import org.jetbrains.kotlin.resolve.calls.inference.constraintPosition.Constrain
 import org.jetbrains.kotlin.types.JetType
 import org.jetbrains.kotlin.types.Variance
 
-public trait TypeBounds {
+public interface TypeBounds {
     public val varianceOfPosition: Variance
 
     public val typeVariable: TypeParameterDescriptor

core/descriptors/src/org/jetbrains/kotlin/resolve/scopes/JetScope.kt

@@ -23,7 +23,7 @@ import org.jetbrains.kotlin.utils.Printer
 import org.jetbrains.kotlin.utils.toReadOnlyList
 import java.lang.reflect.Modifier
 
-public trait JetScope {
+public interface JetScope {
 
     public fun getClassifier(name: Name): ClassifierDescriptor?
 
@@ -201,7 +201,7 @@ public class DescriptorKindFilter(
     }
 }
 
-public trait DescriptorKindExclude {
+public interface DescriptorKindExclude {
     public fun excludes(descriptor: DeclarationDescriptor): Boolean
 
     public val fullyExcludedDescriptorKinds: Int

core/descriptors/src/org/jetbrains/kotlin/resolve/scopes/StaticScopeForKotlinClass.kt

@@ -16,21 +16,21 @@
 
 package org.jetbrains.kotlin.resolve.scopes
 
-import org.jetbrains.kotlin.descriptors.*
+import org.jetbrains.kotlin.descriptors.ClassDescriptor
+import org.jetbrains.kotlin.descriptors.ClassKind
+import org.jetbrains.kotlin.descriptors.FunctionDescriptor
 import org.jetbrains.kotlin.name.Name
 import org.jetbrains.kotlin.resolve.DescriptorFactory.createEnumValueOfMethod
 import org.jetbrains.kotlin.resolve.DescriptorFactory.createEnumValuesMethod
-import org.jetbrains.kotlin.types.JetType
 import org.jetbrains.kotlin.utils.Printer
 import java.util.ArrayList
-import kotlin.properties.Delegates
 
 public class StaticScopeForKotlinClass(
         private val containingClass: ClassDescriptor
 ) : JetScopeImpl() {
     override fun getClassifier(name: Name) = null // TODO
 
-    private val functions: List<FunctionDescriptor> by Delegates.lazy {
+    private val functions: List<FunctionDescriptor> by lazy {
         if (containingClass.getKind() != ClassKind.ENUM_CLASS) {
             listOf<FunctionDescriptor>()
         }

core/descriptors/src/org/jetbrains/kotlin/resolve/scopes/SubstitutingScope.kt

@@ -25,13 +25,12 @@ import org.jetbrains.kotlin.types.TypeSubstitutor
 import org.jetbrains.kotlin.utils.Printer
 import org.jetbrains.kotlin.utils.newHashSetWithExpectedSize
 import java.util.HashMap
-import kotlin.properties.Delegates
 
 public class SubstitutingScope(private val workerScope: JetScope, private val substitutor: TypeSubstitutor) : JetScope {
 
     private var substitutedDescriptors: MutableMap<DeclarationDescriptor, DeclarationDescriptor?>? = null
 
-    private val _allDescriptors by Delegates.lazy { substitute(workerScope.getDescriptors()) }
+    private val _allDescriptors by lazy { substitute(workerScope.getDescriptors()) }
 
     private fun <D : DeclarationDescriptor> substitute(descriptor: D?): D? {
         if (descriptor == null) return null

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

@@ -16,8 +16,8 @@
 
 package org.jetbrains.kotlin.types
 
-import kotlin.properties.*
+import org.jetbrains.kotlin.descriptors.ClassDescriptor
-import org.jetbrains.kotlin.descriptors.*
+import org.jetbrains.kotlin.descriptors.TypeParameterDescriptor
 
 class StarProjectionImpl(
         private val typeParameter: TypeParameterDescriptor
@@ -27,7 +27,7 @@ class StarProjectionImpl(
     override fun getProjectionKind() = Variance.OUT_VARIANCE
 
     // No synchronization here: there's no problem in accidentally computing this twice
-    private val _type: JetType by Delegates.lazy {
+    private val _type: JetType by lazy {
         typeParameter.starProjectionType()
     }
 

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

@@ -18,9 +18,9 @@ package org.jetbrains.kotlin.types
 
 import org.jetbrains.kotlin.descriptors.TypeParameterDescriptor
 
-public trait TypeCapability
+public interface TypeCapability
 
-public trait Specificity : TypeCapability {
+public interface Specificity : TypeCapability {
 
     public enum class Relation {
         LESS_SPECIFIC,
@@ -40,7 +40,7 @@ fun oneMoreSpecificThanAnother(a: JetType, b: JetType) =
 // To facilitate laziness, any JetType implementation may inherit from this trait,
 // even if it turns out that the type an instance represents is not actually a type variable
 // (i.e. it is not derived from a type parameter), see isTypeVariable
-public trait CustomTypeVariable : TypeCapability {
+public interface CustomTypeVariable : TypeCapability {
     public val isTypeVariable: Boolean
 
     // If typeParameterDescriptor != null <=> isTypeVariable == true, this is not a type variable
@@ -56,7 +56,7 @@ public fun JetType.getCustomTypeVariable(): CustomTypeVariable? =
             if (it.isTypeVariable) it else null
         }
 
-public trait SubtypingRepresentatives : TypeCapability {
+public interface SubtypingRepresentatives : TypeCapability {
     public val subTypeRepresentative: JetType
     public val superTypeRepresentative: JetType
 

core/descriptors/src/org/jetbrains/kotlin/types/error/MissingDependencyErrorClass.kt

@@ -19,6 +19,6 @@ package org.jetbrains.kotlin.types.error
 import org.jetbrains.kotlin.name.FqName
 
 // marker for DescriptorRenderer to treat specially in decompiler mode
-public trait MissingDependencyErrorClass {
+public interface MissingDependencyErrorClass {
     public val fullFqName: FqName
 }

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

@@ -21,7 +21,7 @@ import org.jetbrains.kotlin.name.FqName
 import org.jetbrains.kotlin.types.checker.JetTypeChecker
 import kotlin.platform.platformStatic
 
-public trait FlexibleTypeCapabilities {
+public interface FlexibleTypeCapabilities {
     fun <T: TypeCapability> getCapability(capabilityClass: Class<T>, jetType: JetType, flexibility: Flexibility): T?
     val id: String
 
@@ -31,7 +31,7 @@ public trait FlexibleTypeCapabilities {
     }
 }
 
-public trait Flexibility : TypeCapability, SubtypingRepresentatives {
+public interface Flexibility : TypeCapability, SubtypingRepresentatives {
     companion object {
         // This is a "magic" classifier: when type resolver sees it in the code, e.g. ft<Foo, Foo?>, instead of creating a normal type,
         // it creates a flexible type, e.g. (Foo..Foo?).
@@ -100,12 +100,12 @@ fun Collection<TypeProjection>.singleBestRepresentative(): TypeProjection? {
 public fun JetType.lowerIfFlexible(): JetType = if (this.isFlexible()) this.flexibility().lowerBound else this
 public fun JetType.upperIfFlexible(): JetType = if (this.isFlexible()) this.flexibility().upperBound else this
 
-public trait NullAwareness : TypeCapability {
+public interface NullAwareness : TypeCapability {
     public fun makeNullableAsSpecified(nullable: Boolean): JetType
     public fun computeIsNullable(): Boolean
 }
 
-trait FlexibleTypeDelegation : TypeCapability {
+interface FlexibleTypeDelegation : TypeCapability {
     public val delegateType: JetType
 }
 

core/deserialization/src/org/jetbrains/kotlin/serialization/deserialization/FlexibleTypeCapabilitiesDeserializer.kt

@@ -19,7 +19,7 @@ package org.jetbrains.kotlin.serialization.deserialization
 import org.jetbrains.kotlin.types.DynamicTypeCapabilities
 import org.jetbrains.kotlin.types.FlexibleTypeCapabilities
 
-trait FlexibleTypeCapabilitiesDeserializer {
+interface FlexibleTypeCapabilitiesDeserializer {
     object ThrowException : FlexibleTypeCapabilitiesDeserializer {
         override fun capabilitiesById(id: String): FlexibleTypeCapabilities? {
             throw IllegalArgumentException("Capabilities not found by ThrowException manager: $id")

core/deserialization/src/org/jetbrains/kotlin/serialization/deserialization/LocalClassResolver.kt

@@ -19,6 +19,6 @@ package org.jetbrains.kotlin.serialization.deserialization
 import org.jetbrains.kotlin.descriptors.ClassDescriptor
 import org.jetbrains.kotlin.name.ClassId
 
-public trait LocalClassResolver {
+public interface LocalClassResolver {
     public fun resolveLocalClass(classId: ClassId): ClassDescriptor?
 }

core/deserialization/src/org/jetbrains/kotlin/serialization/deserialization/descriptors/DeserializedCallableMemberDescriptor.kt

@@ -20,7 +20,7 @@ import org.jetbrains.kotlin.serialization.ProtoBuf
 import org.jetbrains.kotlin.serialization.deserialization.NameResolver
 import org.jetbrains.kotlin.descriptors.CallableMemberDescriptor
 
-public trait DeserializedCallableMemberDescriptor: CallableMemberDescriptor {
+public interface DeserializedCallableMemberDescriptor: CallableMemberDescriptor {
     public val proto: ProtoBuf.Callable
     public val nameResolver: NameResolver
 }

core/deserialization/src/org/jetbrains/kotlin/serialization/deserialization/descriptors/DeserializedMemberScope.kt

@@ -69,7 +69,7 @@ public abstract class DeserializedMemberScope protected constructor(
                 protos = ArrayList(1)
                 map.put(key, protos)
             }
-            protos!!.add(memberProto)
+            protos.add(memberProto)
         }
         return map
     }

core/deserialization/src/org/jetbrains/kotlin/serialization/deserialization/findClassInModule.kt

@@ -23,7 +23,7 @@ import org.jetbrains.kotlin.descriptors.ModuleDescriptor
 import org.jetbrains.kotlin.name.ClassId
 
 public fun ModuleDescriptor.findClassAcrossModuleDependencies(classId: ClassId): ClassDescriptor? {
-    val packageViewDescriptor = getPackage(classId.getPackageFqName()) ?: return null
+    val packageViewDescriptor = getPackage(classId.getPackageFqName())
     val segments = classId.getRelativeClassName().pathSegments()
     val topLevelClass = packageViewDescriptor.memberScope.getClassifier(segments.first()) as? ClassDescriptor ?: return null
     var result = topLevelClass

core/util.runtime/src/org/jetbrains/kotlin/storage/StorageManager.kt

@@ -18,7 +18,7 @@ package org.jetbrains.kotlin.storage
 
 import java.util.concurrent.ConcurrentMap
 
-public trait StorageManager {
+public interface StorageManager {
     /**
      * Given a function compute: K -> V create a memoized version of it that computes a value only once for each key
      * @param compute the function to be memoized

core/util.runtime/src/org/jetbrains/kotlin/storage/storage.kt

@@ -16,19 +16,19 @@
 
 package org.jetbrains.kotlin.storage
 
-public trait MemoizedFunctionToNotNull<P, R : Any> : Function1<P, R> {
+public interface MemoizedFunctionToNotNull<P, R : Any> : Function1<P, R> {
     public fun isComputed(key: P): Boolean
 }
 
-public trait MemoizedFunctionToNullable<P, R : Any> : Function1<P, R?> {
+public interface MemoizedFunctionToNullable<P, R : Any> : Function1<P, R?> {
     public fun isComputed(key: P): Boolean
 }
 
-public trait NotNullLazyValue<T : Any> : Function0<T> {
+public interface NotNullLazyValue<T : Any> : Function0<T> {
     public fun isComputed(): Boolean
 }
 
-public trait NullableLazyValue<T : Any> : Function0<T?> {
+public interface NullableLazyValue<T : Any> : Function0<T?> {
     public fun isComputed(): Boolean
 }