Optimize scopes handling inside ChainedMemberScope

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)
         }
     }
 }