Implemented own version of LookupElementProximityWeigher (the standard one checks getObject() instanceof PsiElement)

#KT-8842 Fixed

idea/idea-completion/src/org/jetbrains/kotlin/idea/completion/Weighers.kt

@@ -16,10 +16,13 @@
 
 package org.jetbrains.kotlin.idea.completion
 
+import com.intellij.codeInsight.completion.CompletionLocation
+import com.intellij.codeInsight.completion.CompletionWeigher
 import com.intellij.codeInsight.lookup.LookupElement
 import com.intellij.codeInsight.lookup.LookupElementWeigher
 import com.intellij.codeInsight.lookup.WeighingContext
 import com.intellij.openapi.module.ModuleUtilCore
+import com.intellij.psi.util.proximity.PsiProximityComparator
 import org.jetbrains.kotlin.descriptors.ClassDescriptor
 import org.jetbrains.kotlin.descriptors.ClassKind
 import org.jetbrains.kotlin.descriptors.FunctionDescriptor
@@ -102,6 +105,14 @@ class LocationWeigher(private val file: JetFile, private val originalFile: JetFi
     }
 }
 
+// analog of LookupElementProximityWeigher which does not work for us
+object KotlinLookupElementProximityWeigher : CompletionWeigher() {
+    override fun weigh(element: LookupElement, location: CompletionLocation): Comparable<Nothing>? {
+        val psiElement = (element.`object` as? DeclarationLookupObject)?.psiElement ?: return null
+        return PsiProximityComparator.getProximity({ psiElement }, location.completionParameters.position, location.processingContext)
+    }
+}
+
 object SmartCompletionPriorityWeigher : LookupElementWeigher("kotlin.smartCompletionPriority") {
     override fun weigh(element: LookupElement, context: WeighingContext)
             = element.getUserData(SMART_COMPLETION_ITEM_PRIORITY_KEY) ?: SmartCompletionItemPriority.DEFAULT

idea/idea-completion/testData/weighers/basic/PreferFromJdk.Data.kt

@@ -0,0 +1,3 @@
+package dependency
+
+public class Data

idea/idea-completion/testData/weighers/basic/PreferFromJdk.kt

@@ -0,0 +1,7 @@
+import dependency.*
+import java.util.*
+
+fun foo(): Dat<caret>
+
+// ORDER: Date
+// ORDER: Data

idea/idea-completion/tests/org/jetbrains/kotlin/idea/completion/test/weighers/BasicCompletionWeigherTestGenerated.java

@@ -131,6 +131,12 @@ public class BasicCompletionWeigherTestGenerated extends AbstractBasicCompletion
         doTest(fileName);
     }
 
+    @TestMetadata("PreferFromJdk.kt")
+    public void testPreferFromJdk() throws Exception {
+        String fileName = JetTestUtils.navigationMetadata("idea/idea-completion/testData/weighers/basic/PreferFromJdk.kt");
+        doTest(fileName);
+    }
+
     @TestMetadata("PropertiesBeforeKeywords.kt")
     public void testPropertiesBeforeKeywords() throws Exception {
         String fileName = JetTestUtils.navigationMetadata("idea/idea-completion/testData/weighers/basic/PropertiesBeforeKeywords.kt");

idea/src/META-INF/plugin.xml

@@ -331,6 +331,8 @@
     <statistician key="completion" implementationClass="org.jetbrains.kotlin.idea.completion.KotlinCompletionStatistician"/>
     <statistician key="proximity" implementationClass="org.jetbrains.kotlin.idea.completion.KotlinProximityStatistician"/>
 
+    <weigher key="completion" implementationClass="org.jetbrains.kotlin.idea.completion.KotlinLookupElementProximityWeigher" id="kotlin.proximity" order="after proximity"/>
+
     <psi.referenceContributor language="jet" implementation="org.jetbrains.kotlin.idea.references.JetReferenceContributor"/>
 
     <renamePsiElementProcessor id="KotlinClass"