enlarge use scope scope of PSI elements in built-in sources to Project and Libraries (to counteract the effect of https://github.com/JetBrains/intellij-community/commit/897d7cabe6d482182ae6d54a1b158f80b1652d75)

idea/idea-analysis/src/org/jetbrains/kotlin/idea/references/BuiltInsReferenceResolver.kt

@@ -21,6 +21,7 @@ import com.intellij.openapi.components.ServiceManager
 import com.intellij.openapi.project.Project
 import com.intellij.openapi.startup.StartupManager
 import com.intellij.openapi.vfs.VfsUtilCore
+import com.intellij.openapi.vfs.VirtualFile
 import com.intellij.openapi.vfs.VirtualFileManager
 import com.intellij.psi.PsiElement
 import com.intellij.psi.PsiManager
@@ -86,17 +87,7 @@ public class BuiltInsReferenceResolver(val project: Project, val startupManager:
     }
 
     private fun getJetBuiltInsFiles(): Set<JetFile> {
-        val builtIns = getBuiltInSourceFiles(LightClassUtil.getBuiltInsDirUrl())
-
-        if (ApplicationManager.getApplication().isUnitTestMode()) {
-            // In production, the above URL is enough as it contains sources for both native and compilable built-ins
-            // (it's simply the "kotlin" directory in kotlin-plugin.jar)
-            // But in tests, sources of built-ins are not added to the classpath automatically, so we manually specify URLs for both:
-            // LightClassUtil.getBuiltInsDirUrl() does so for native built-ins and the code below for compilable built-ins
-            return builtIns + getBuiltInSourceFiles(BUILT_INS_COMPILABLE_SRC_DIR.toURI().toURL())
-        }
-
-        return builtIns
+        return getBuiltInsDirUrls().flatMapTo(hashSetOf<JetFile>()) { getBuiltInSourceFiles(it) }
     }
 
     private fun getBuiltInSourceFiles(url: URL): Set<JetFile> {
@@ -147,6 +138,8 @@ public class BuiltInsReferenceResolver(val project: Project, val startupManager:
     companion object {
         private val BUILT_INS_COMPILABLE_SRC_DIR = File("core/builtins/src", KotlinBuiltIns.BUILT_INS_PACKAGE_NAME.asString())
 
+        private val builtInDirUrls = getBuiltInsDirUrls().map { VfsUtilCore.toIdeaUrl(it.toString()) }
+
         public fun getInstance(project: Project): BuiltInsReferenceResolver =
             ServiceManager.getService(project, javaClass<BuiltInsReferenceResolver>())
 
@@ -173,13 +166,28 @@ public class BuiltInsReferenceResolver(val project: Project, val startupManager:
             return null
         }
 
-        public fun isFromBuiltIns(element: PsiElement): Boolean =
-                getInstance(element.project).builtInsSources!!.contains(element.getContainingFile())
+        public fun isFromBuiltIns(element: PsiElement): Boolean {
+            val url = element.getContainingFile()?.getVirtualFile()?.getUrl()
+            return url != null && VfsUtilCore.isUnder(url, builtInDirUrls)
+        }
 
         private fun getMemberScope(parent: DeclarationDescriptor?): JetScope? = when(parent) {
             is ClassDescriptor -> parent.getDefaultType().getMemberScope()
             is PackageFragmentDescriptor -> parent.getMemberScope()
             else -> null
         }
+
+        public fun getBuiltInsDirUrls(): Set<URL> {
+            val defaultBuiltIns = LightClassUtil.getBuiltInsDirUrl()
+            // In production, the above URL is enough as it contains sources for both native and compilable built-ins
+            // (it's simply the "kotlin" directory in kotlin-plugin.jar)
+            // But in tests, sources of built-ins are not added to the classpath automatically, so we manually specify URLs for both:
+            // LightClassUtil.getBuiltInsDirUrl() does so for native built-ins and the code below for compilable built-ins
+
+            if (ApplicationManager.getApplication().isUnitTestMode) {
+                return setOf(defaultBuiltIns, BUILT_INS_COMPILABLE_SRC_DIR.toURI().toURL())
+            }
+            return setOf(defaultBuiltIns)
+        }
     }
 }

idea/src/META-INF/plugin.xml

@@ -420,6 +420,8 @@
     <highlightUsagesHandlerFactory implementation="org.jetbrains.kotlin.idea.highlighter.KotlinHighlightExitPointsHandlerFactory"/>
     <findUsagesHandlerFactory implementation="org.jetbrains.kotlin.idea.findUsages.KotlinFindUsagesHandlerFactory"/>
     <usageTypeProvider implementation="org.jetbrains.kotlin.idea.findUsages.JetUsageTypeProvider"/>
+    <useScopeEnlarger implementation="org.jetbrains.kotlin.idea.findUsages.BuiltInsUseScopeEnlarger"/>
+
     <refactoring.safeDeleteProcessor
         id="kotlinProcessor"
         implementation="org.jetbrains.kotlin.idea.refactoring.safeDelete.KotlinSafeDeleteProcessor"

idea/src/org/jetbrains/kotlin/idea/findUsages/BuiltInsUseScopeEnlarger.kt

@@ -0,0 +1,34 @@
+/*
+ * Copyright 2010-2015 JetBrains s.r.o.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.jetbrains.kotlin.idea.findUsages
+
+import com.intellij.openapi.vfs.VfsUtilCore
+import com.intellij.psi.PsiElement
+import com.intellij.psi.search.ProjectScope
+import com.intellij.psi.search.SearchScope
+import com.intellij.psi.search.UseScopeEnlarger
+import org.jetbrains.kotlin.idea.references.BuiltInsReferenceResolver
+import org.jetbrains.kotlin.psi.JetElement
+
+public class BuiltInsUseScopeEnlarger : UseScopeEnlarger() {
+    override fun getAdditionalUseScope(element: PsiElement): SearchScope? {
+        if (element is JetElement && BuiltInsReferenceResolver.isFromBuiltIns(element)) {
+            return ProjectScope.getAllScope(element.getProject())
+        }
+        return null
+    }
+}