Optimize scopes handling inside ChainedMemberScope

compiler/frontend/src/org/jetbrains/kotlin/resolve/scopes/receivers/Qualifier.kt

@@ -30,7 +30,6 @@ import org.jetbrains.kotlin.resolve.scopes.MemberScope
 import org.jetbrains.kotlin.resolve.scopes.MemberScopeImpl
 import org.jetbrains.kotlin.types.KotlinType
 import org.jetbrains.kotlin.utils.Printer
-import java.util.*
 
 interface Qualifier : QualifierReceiver {
     val referenceExpression: KtSimpleNameExpression
@@ -72,17 +71,13 @@ class ClassQualifier(
     }
 
     override val staticScope: MemberScope
-        get() {
-            val scopes = ArrayList<MemberScope>(2)
-
-            scopes.add(descriptor.staticScope)
-
-            if (descriptor.kind != ClassKind.ENUM_ENTRY) {
-                scopes.add(descriptor.unsubstitutedInnerClassesScope)
-            }
-
-            return ChainedMemberScope("Static scope for ${descriptor.name} as class or object", scopes)
-        }
+        get() =
+            if (descriptor.kind == ClassKind.ENUM_ENTRY) descriptor.staticScope
+            else ChainedMemberScope.create(
+                "Static scope for ${descriptor.name} as class or object",
+                descriptor.staticScope,
+                descriptor.unsubstitutedInnerClassesScope
+            )
 
     override fun toString() = "Class{$descriptor}"
 }
@@ -100,9 +95,10 @@ class TypeAliasQualifier(
     override val staticScope: MemberScope
         get() = when {
             DescriptorUtils.isEnumClass(classDescriptor) ->
-                ChainedMemberScope(
+                ChainedMemberScope.create(
                     "Static scope for typealias ${descriptor.name}",
-                    listOf(classDescriptor.staticScope, EnumEntriesScope())
+                    classDescriptor.staticScope,
+                    EnumEntriesScope()
                 )
             else ->
                 classDescriptor.staticScope

core/descriptors.runtime/tests/org/jetbrains/kotlin/jvm/runtime/AbstractJvmRuntimeDescriptorLoaderTest.kt

@@ -198,7 +198,7 @@ abstract class AbstractJvmRuntimeDescriptorLoaderTest : TestCaseWithTmpdir() {
             val list = ArrayList<MemberScope>(packageScopes.size + 1)
             list.add(ScopeWithClassifiers(classes))
             list.addAll(packageScopes)
-            scope = ChainedMemberScope("synthetic package view for test", list)
+            scope = ChainedMemberScope.create("synthetic package view for test", list)
         }
 
         override val fqName: FqName

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

@@ -24,26 +24,28 @@ import org.jetbrains.kotlin.name.Name
 import org.jetbrains.kotlin.util.collectionUtils.getFirstClassifierDiscriminateHeaders
 import org.jetbrains.kotlin.util.collectionUtils.getFromAllScopes
 import org.jetbrains.kotlin.utils.Printer
+import org.jetbrains.kotlin.utils.SmartList
 
-class ChainedMemberScope(
-        internal val debugName: String,
-        private val scopes: List<MemberScope>
+class ChainedMemberScope private constructor(
+    private val debugName: String,
+    private val scopes: Array<out MemberScope>
 ) : MemberScope {
-    override fun getContributedClassifier(name: Name, location: LookupLocation): ClassifierDescriptor?
-            = getFirstClassifierDiscriminateHeaders(scopes) { it.getContributedClassifier(name, location) }
 
-    override fun getContributedVariables(name: Name, location: LookupLocation): Collection<PropertyDescriptor>
-            = getFromAllScopes(scopes) { it.getContributedVariables(name, location) }
+    override fun getContributedClassifier(name: Name, location: LookupLocation): ClassifierDescriptor? =
+        getFirstClassifierDiscriminateHeaders(scopes) { it.getContributedClassifier(name, location) }
 
-    override fun getContributedFunctions(name: Name, location: LookupLocation): Collection<SimpleFunctionDescriptor>
-            = getFromAllScopes(scopes) { it.getContributedFunctions(name, location) }
+    override fun getContributedVariables(name: Name, location: LookupLocation): Collection<PropertyDescriptor> =
+        getFromAllScopes(scopes) { it.getContributedVariables(name, location) }
 
-    override fun getContributedDescriptors(kindFilter: DescriptorKindFilter, nameFilter: (Name) -> Boolean)
-            = getFromAllScopes(scopes) { it.getContributedDescriptors(kindFilter, nameFilter) }
+    override fun getContributedFunctions(name: Name, location: LookupLocation): Collection<SimpleFunctionDescriptor> =
+        getFromAllScopes(scopes) { it.getContributedFunctions(name, location) }
+
+    override fun getContributedDescriptors(kindFilter: DescriptorKindFilter, nameFilter: (Name) -> Boolean) =
+        getFromAllScopes(scopes) { it.getContributedDescriptors(kindFilter, nameFilter) }
 
     override fun getFunctionNames() = scopes.flatMapTo(mutableSetOf()) { it.getFunctionNames() }
     override fun getVariableNames() = scopes.flatMapTo(mutableSetOf()) { it.getVariableNames() }
-    override fun getClassifierNames(): Set<Name>? = scopes.flatMapClassifierNamesOrNull()
+    override fun getClassifierNames(): Set<Name>? = scopes.asIterable().flatMapClassifierNamesOrNull()
 
     override fun recordLookup(name: Name, location: LookupLocation) {
         scopes.forEach { it.recordLookup(name, location) }
@@ -64,12 +66,25 @@ class ChainedMemberScope(
     }
 
     companion object {
-        fun create(debugName: String, scopes: List<MemberScope>): MemberScope {
-            return when (scopes.size) {
-                0 -> MemberScope.Empty
-                1 -> scopes.single()
-                else -> ChainedMemberScope(debugName, scopes)
+        fun create(debugName: String, vararg scopes: MemberScope): MemberScope = create(debugName, scopes.asIterable())
+
+        fun create(debugName: String, scopes: Iterable<MemberScope>): MemberScope {
+            val flattenedNonEmptyScopes = SmartList<MemberScope>()
+            for (scope in scopes) {
+                when {
+                    scope === MemberScope.Empty -> {}
+                    scope is ChainedMemberScope -> flattenedNonEmptyScopes.addAll(scope.scopes)
+                    else -> flattenedNonEmptyScopes.add(scope)
+                }
             }
+            return createOrSingle(debugName, flattenedNonEmptyScopes)
         }
+
+        internal fun createOrSingle(debugName: String, scopes: List<MemberScope>): MemberScope =
+            when (scopes.size) {
+                0 -> MemberScope.Empty
+                1 -> scopes[0]
+                else -> ChainedMemberScope(debugName, scopes.toTypedArray())
+            }
     }
 }

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

@@ -22,9 +22,10 @@ import org.jetbrains.kotlin.incremental.components.LookupLocation
 import org.jetbrains.kotlin.name.Name
 import org.jetbrains.kotlin.resolve.selectMostSpecificInEachOverridableGroup
 import org.jetbrains.kotlin.types.KotlinType
+import org.jetbrains.kotlin.util.collectionUtils.listOfNonEmptyScopes
 import org.jetbrains.kotlin.utils.Printer
 
-class TypeIntersectionScope private constructor(override val workerScope: ChainedMemberScope) : AbstractScopeAdapter() {
+class TypeIntersectionScope private constructor(private val debugName: String, override val workerScope: MemberScope) : AbstractScopeAdapter() {
     override fun getContributedFunctions(name: Name, location: LookupLocation) =
             super.getContributedFunctions(name, location).selectMostSpecificInEachOverridableGroup { this }
 
@@ -39,17 +40,19 @@ class TypeIntersectionScope private constructor(override val workerScope: Chaine
     }
 
     override fun printScopeStructure(p: Printer) {
-        p.print("TypeIntersectionScope for: " + workerScope.debugName)
+        p.print("TypeIntersectionScope for: " + debugName)
         super.printScopeStructure(p)
     }
 
     companion object {
         @JvmStatic
         fun create(message: String, types: Collection<KotlinType>): MemberScope {
-            val chainedScope = ChainedMemberScope(message, types.map { it.memberScope })
-            if (types.size <= 1) return chainedScope
+            val nonEmptyScopes = listOfNonEmptyScopes(types.map { it.memberScope })
+            val chainedOrSingle = ChainedMemberScope.createOrSingle(message, nonEmptyScopes)
 
-            return TypeIntersectionScope(chainedScope)
+            if (nonEmptyScopes.size <= 1) return chainedOrSingle
+
+            return TypeIntersectionScope(message, chainedOrSingle)
         }
     }
 }

idea/ide-common/src/org/jetbrains/kotlin/idea/kdoc/resolveKDocLink.kt

@@ -212,7 +212,7 @@ fun getKDocLinkMemberScope(descriptor: DeclarationDescriptor, contextScope: Lexi
         is PackageViewDescriptor -> descriptor.memberScope
 
         is ClassDescriptor -> {
-            ChainedMemberScope(
+            ChainedMemberScope.create(
                 "Member scope for KDoc resolve", listOfNotNull(
                     descriptor.unsubstitutedMemberScope,
                     descriptor.staticScope,

idea/jvm-debugger/jvm-debugger-evaluation/src/org/jetbrains/kotlin/idea/debugger/evaluate/compilation/CodeFragmentCompiler.kt

@@ -284,7 +284,7 @@ private class EvaluatorModuleDescriptor(
                     MemberScope.Empty
                 } else {
                     val scopes = fragments.map { it.getMemberScope() } + SubpackagesScope(module, fqName)
-                    ChainedMemberScope("package view scope for $fqName in ${module.name}", scopes)
+                    ChainedMemberScope.create("package view scope for $fqName in ${module.name}", scopes)
                 }
             }