Make keyword lookup objects correctly comparable

- This is done to fix the problem with duplicated keyword items in
CodeWithMe plugin (see https://youtrack.jetbrains.com/issue/CWM-438)

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

@@ -48,7 +48,16 @@ import org.jetbrains.kotlin.renderer.render
 import org.jetbrains.kotlin.resolve.ModifierCheckerCore
 import org.jetbrains.kotlin.utils.addToStdlib.firstIsInstanceOrNull
 
-open class KeywordLookupObject
+/**
+ * We want all [KeywordLookupObject]s to be equal to each other.
+ *
+ * That way, if the same keyword is completed twice, it would not be duplicated in the completion. This is not required in the regular
+ * completion, but can be a problem in CodeWithMe plugin (see https://youtrack.jetbrains.com/issue/CWM-438).
+ */
+open class KeywordLookupObject {
+    override fun equals(other: Any?): Boolean = this === other || javaClass == other?.javaClass
+    override fun hashCode(): Int = javaClass.hashCode()
+}
 
 object KeywordCompletion {
     private val ALL_KEYWORDS = (KEYWORDS.types + SOFT_KEYWORDS.types)

idea/idea-completion/src/org/jetbrains/kotlin/idea/completion/handlers/handlerUtils.kt

@@ -100,6 +100,11 @@ fun CharSequence.isCharAt(offset: Int, c: Char) = offset < length && this[offset
 fun Document.isTextAt(offset: Int, text: String) =
     offset + text.length <= textLength && getText(TextRange(offset, offset + text.length)) == text
 
+private data class KeywordConstructLookupObject(
+    private val keyword: String,
+    private val constructToInsert: String
+) : KeywordLookupObject()
+
 fun createKeywordConstructLookupElement(
     project: Project,
     keyword: String,
@@ -136,7 +141,8 @@ fun createKeywordConstructLookupElement(
             "..." +
             (if (tailAfterCaret.contains('\n')) tailAfterCaret.replace("\n", "").trimStart() else tailAfterCaret)
 
-    return LookupElementBuilder.create(KeywordLookupObject(), keyword)
+    val lookupElement = KeywordConstructLookupObject(keyword, fileTextToReformat)
+    return LookupElementBuilder.create(lookupElement, keyword)
         .bold()
         .withTailText(tailText)
         .withInsertHandler { insertionContext, _ ->