Introduce components for library-to-source resolution in IDE

#KT-24309 In progress

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

@@ -20,6 +20,7 @@ import org.jetbrains.kotlin.builtins.KotlinBuiltIns
 import org.jetbrains.kotlin.name.FqName
 import org.jetbrains.kotlin.name.Name
 import org.jetbrains.kotlin.platform.TargetPlatform
+import org.jetbrains.kotlin.resolve.AnchorProvider
 
 interface ModuleDescriptor : DeclarationDescriptor {
     override fun getContainingDeclaration(): DeclarationDescriptor? = null
@@ -61,4 +62,6 @@ interface ModuleDescriptor : DeclarationDescriptor {
     val isValid: Boolean
 
     fun assertValid()
+
+    val anchorProvider: AnchorProvider
 }

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

@@ -19,21 +19,28 @@ package org.jetbrains.kotlin.descriptors
 import org.jetbrains.kotlin.incremental.components.NoLookupLocation
 import org.jetbrains.kotlin.name.ClassId
 
-fun ModuleDescriptor.findClassifierAcrossModuleDependencies(classId: ClassId): ClassifierDescriptor? {
+fun ModuleDescriptor.findClassifierAcrossModuleDependencies(classId: ClassId): ClassifierDescriptor? = withAnchorFallback {
     val packageViewDescriptor = getPackage(classId.packageFqName)
     val segments = classId.relativeClassName.pathSegments()
     val topLevelClass = packageViewDescriptor.memberScope.getContributedClassifier(
         segments.first(),
         NoLookupLocation.FROM_DESERIALIZATION
-    ) ?: return null
+    ) ?: return@withAnchorFallback null
     var result = topLevelClass
     for (name in segments.subList(1, segments.size)) {
-        if (result !is ClassDescriptor) return null
+        if (result !is ClassDescriptor) return@withAnchorFallback null
         result = result.unsubstitutedInnerClassesScope
             .getContributedClassifier(name, NoLookupLocation.FROM_DESERIALIZATION) as? ClassDescriptor
-            ?: return null
+            ?: return@withAnchorFallback null
     }
-    return result
+    return@withAnchorFallback result
+}
+
+private inline fun ModuleDescriptor.withAnchorFallback(
+    crossinline doSearch: ModuleDescriptor.() -> ClassifierDescriptor? 
+): ClassifierDescriptor? {
+    val anchor = anchorProvider.getAnchor(this)
+    return if (anchor == null) doSearch() else doSearch() ?: anchor.doSearch()
 }
 
 fun ModuleDescriptor.findClassAcrossModuleDependencies(classId: ClassId): ClassDescriptor? =

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

@@ -25,6 +25,7 @@ import org.jetbrains.kotlin.descriptors.annotations.Annotations
 import org.jetbrains.kotlin.name.FqName
 import org.jetbrains.kotlin.name.Name
 import org.jetbrains.kotlin.platform.TargetPlatform
+import org.jetbrains.kotlin.resolve.AnchorProvider
 import org.jetbrains.kotlin.storage.StorageManager
 import org.jetbrains.kotlin.types.checker.REFINER_CAPABILITY
 import org.jetbrains.kotlin.types.checker.Ref
@@ -38,7 +39,8 @@ class ModuleDescriptorImpl @JvmOverloads constructor(
     // May be null in compiler context, should be not-null in IDE context
     override val platform: TargetPlatform? = null,
     capabilities: Map<ModuleDescriptor.Capability<*>, Any?> = emptyMap(),
-    override val stableName: Name? = null
+    override val stableName: Name? = null,
+    override val anchorProvider: AnchorProvider = AnchorProvider.Default,
 ) : DeclarationDescriptorImpl(Annotations.EMPTY, moduleName), ModuleDescriptor {
     private val capabilities: Map<ModuleDescriptor.Capability<*>, Any?>
 

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

@@ -0,0 +1,14 @@
+/*
+ * Copyright 2010-2020 JetBrains s.r.o. and Kotlin Programming Language contributors.
+ * Use of this source code is governed by the Apache 2.0 license that can be found in the license/LICENSE.txt file.
+ */
+
+package org.jetbrains.kotlin.resolve
+
+import org.jetbrains.kotlin.descriptors.ModuleDescriptor
+
+abstract class AnchorProvider {
+    open fun getAnchor(moduleDescriptor: ModuleDescriptor): ModuleDescriptor? = null
+    
+    companion object Default : AnchorProvider()
+}

core/descriptors/src/org/jetbrains/kotlin/types/ErrorUtils.java

@@ -31,6 +31,7 @@ import org.jetbrains.kotlin.incremental.components.LookupLocation;
 import org.jetbrains.kotlin.name.FqName;
 import org.jetbrains.kotlin.name.Name;
 import org.jetbrains.kotlin.platform.TargetPlatform;
+import org.jetbrains.kotlin.resolve.AnchorProvider;
 import org.jetbrains.kotlin.resolve.descriptorUtil.DescriptorUtilsKt;
 import org.jetbrains.kotlin.resolve.scopes.DescriptorKindFilter;
 import org.jetbrains.kotlin.resolve.scopes.MemberScope;
@@ -53,6 +54,12 @@ public class ErrorUtils {
 
     static {
         ERROR_MODULE = new ModuleDescriptor() {
+            @NotNull
+            @Override
+            public AnchorProvider getAnchorProvider() {
+                return AnchorProvider.Default;
+            }
+
             @Nullable
             @Override
             public <T> T getCapability(@NotNull Capability<T> capability) {