Inspection to get rid of unnecessary ticks in references #KT-18124 Fixed

idea/src/META-INF/plugin.xml

@@ -2497,8 +2497,15 @@
                      enabledByDefault="true"
                      cleanupTool="true"
                      level="WEAK WARNING"
-                     language="kotlin"
-    />
+                     language="kotlin"/>
+
+    <localInspection implementationClass="org.jetbrains.kotlin.idea.inspections.RemoveRedundantBackticksInspection"
+                     displayName="Remove redundant backticks"
+                     groupPath="Kotlin"
+                     groupName="Redundant constructs"
+                     enabledByDefault="true"
+                     level="WARNING"
+                     language="kotlin"/>
 
     <localInspection implementationClass="org.jetbrains.kotlin.idea.inspections.RedundantSetterInspection"
                      displayName="Redundant property setter"

idea/src/org/jetbrains/kotlin/idea/inspections/RemoveRedundantBackticksInspection.kt

@@ -0,0 +1,70 @@
+/*
+ * Copyright 2010-2017 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.inspections
+
+import com.intellij.codeInspection.*
+import com.intellij.lang.ASTNode
+import com.intellij.openapi.project.Project
+import com.intellij.psi.PsiElement
+import com.intellij.psi.PsiElementVisitor
+import com.intellij.psi.impl.source.tree.SharedImplUtil
+import org.jetbrains.kotlin.idea.core.KotlinNameSuggester
+import org.jetbrains.kotlin.lexer.KtTokens
+import org.jetbrains.kotlin.psi.*
+
+class RemoveRedundantBackticksInspection : AbstractKotlinInspection() {
+    override fun buildVisitor(holder: ProblemsHolder, isOnTheFly: Boolean): PsiElementVisitor {
+        return object : KtVisitorVoid() {
+            override fun visitKtElement(element: KtElement) {
+                super.visitKtElement(element)
+                SharedImplUtil.getChildrenOfType(element.node, KtTokens.IDENTIFIER).forEach {
+                    if (isRedundantBackticks(it)) {
+                        registerProblem(holder, it.psi)
+                    }
+                }
+            }
+        }
+    }
+
+    private fun isKeyword(text: String): Boolean {
+        return (KtTokens.KEYWORDS.types + KtTokens.SOFT_KEYWORDS.types).any { it.toString() == text }
+    }
+
+    private fun isRedundantBackticks(node: ASTNode): Boolean {
+        return (node.text.startsWith("`") &&
+                node.text.endsWith("`") &&
+                KotlinNameSuggester.isIdentifier(node.text) &&
+                !isKeyword(node.text.removePrefix("`").removeSuffix("`")))
+    }
+
+    private fun registerProblem(holder: ProblemsHolder, element: PsiElement) {
+        holder.registerProblem(element,
+                               "Remove redundant backticks",
+                               ProblemHighlightType.GENERIC_ERROR_OR_WARNING,
+                               RemoveRedundantBackticksQuickFix())
+    }
+}
+
+class RemoveRedundantBackticksQuickFix : LocalQuickFix {
+    override fun getName() = "Remove redundant backticks"
+    override fun getFamilyName() = name
+
+    override fun applyFix(project: Project, descriptor: ProblemDescriptor) {
+        val element = descriptor.psiElement
+        val factory = KtPsiFactory(project)
+        element.replace(factory.createIdentifier(element.text.removePrefix("`").removeSuffix("`")))
+    }
+}