Implement quick fix to convert a too long char literal to a string #KT-13635 Fixed

idea/src/org/jetbrains/kotlin/idea/quickfix/QuickFixRegistrar.kt

@@ -422,5 +422,7 @@ class QuickFixRegistrar : QuickFixContributor {
         FINAL_UPPER_BOUND.registerFactory(RemoveFinalUpperBoundFix)
 
         TYPE_PARAMETER_AS_REIFIED.registerFactory(AddReifiedToTypeParameterOfFunctionFix)
+
+        TOO_MANY_CHARACTERS_IN_CHARACTER_LITERAL.registerFactory(TooLongCharLiteralToStringFix)
     }
 }

idea/src/org/jetbrains/kotlin/idea/quickfix/TooLongCharLiteralToStringFix.kt

@@ -0,0 +1,39 @@
+package org.jetbrains.kotlin.idea.quickfix
+
+import com.intellij.codeInsight.intention.IntentionAction
+import com.intellij.openapi.editor.Editor
+import com.intellij.openapi.project.Project
+import org.jetbrains.kotlin.diagnostics.Diagnostic
+import org.jetbrains.kotlin.diagnostics.Errors
+import org.jetbrains.kotlin.psi.KtConstantExpression
+import org.jetbrains.kotlin.psi.KtFile
+import org.jetbrains.kotlin.psi.KtPsiFactory
+
+class TooLongCharLiteralToStringFix(
+        element: KtConstantExpression
+) : KotlinQuickFixAction<KtConstantExpression>(element) {
+    override fun getText(): String = "Convert too long character literal to string"
+
+    override fun invoke(project: Project, editor: Editor?, file: KtFile) {
+        val text = element.text
+        if (!(text.startsWith("'") && text.endsWith("'") && text.length >= 2)) {
+            return
+        }
+
+        val newStringContent = text
+                .slice(1..text.length - 2)
+                .replace("\"", "\\\"")
+        val newElement = KtPsiFactory(element).createStringTemplate(newStringContent)
+
+        element.replace(newElement)
+    }
+
+    override fun getFamilyName(): String = text
+
+    companion object Factory : KotlinSingleIntentionActionFactory() {
+        override fun createAction(diagnostic: Diagnostic): IntentionAction? {
+            val element = Errors.TOO_MANY_CHARACTERS_IN_CHARACTER_LITERAL.cast(diagnostic).psiElement
+            return TooLongCharLiteralToStringFix(element = element)
+        }
+    }
+}