FIR IDE: Enable RemoveUselessElvisFix.

idea/idea-core/src/org/jetbrains/kotlin/idea/core/psiModificationUtils.kt

@@ -33,7 +33,6 @@ import org.jetbrains.kotlin.name.Name
 import org.jetbrains.kotlin.psi.*
 import org.jetbrains.kotlin.psi.addRemoveModifier.MODIFIERS_ORDER
 import org.jetbrains.kotlin.psi.psiUtil.*
-import org.jetbrains.kotlin.psi.synthetics.findClassDescriptor
 import org.jetbrains.kotlin.psi.typeRefHelpers.setReceiverTypeReference
 import org.jetbrains.kotlin.resolve.BindingContext
 import org.jetbrains.kotlin.resolve.OverridingUtil
@@ -518,12 +517,6 @@ fun KtParameter.dropDefaultValue() {
     deleteChildRange(from, to)
 }
 
-fun dropEnclosingParenthesesIfPossible(expression: KtExpression): KtExpression {
-    val parent = expression.parent as? KtParenthesizedExpression ?: return expression
-    if (!KtPsiUtil.areParenthesesUseless(parent)) return expression
-    return parent.replaced(expression)
-}
-
 fun KtTypeParameterListOwner.addTypeParameter(typeParameter: KtTypeParameter): KtTypeParameter? {
     typeParameterList?.let { return it.addParameter(typeParameter) }
 

idea/idea-fir/src/org/jetbrains/kotlin/idea/quickfix/MainKtQuickFixRegistrar.kt

@@ -104,6 +104,8 @@ class MainKtQuickFixRegistrar : KtQuickFixRegistrar() {
     private val expressions = KtQuickFixesListBuilder.registerPsiQuickFix {
         registerPsiQuickFixes(KtFirDiagnostic.UnnecessarySafeCall::class, ReplaceWithDotCallFix)
         registerPsiQuickFixes(KtFirDiagnostic.UnnecessaryNotNullAssertion::class, RemoveExclExclCallFix)
+        registerPsiQuickFixes(KtFirDiagnostic.UselessElvis::class, RemoveUselessElvisFix)
+        registerPsiQuickFixes(KtFirDiagnostic.UselessElvisRightIsNull::class, RemoveUselessElvisFix)
         registerApplicator(ReplaceCallFixFactories.unsafeCallFactory)
         registerApplicator(AddExclExclCallFixFactories.unsafeCallFactory)
         registerApplicator(AddExclExclCallFixFactories.unsafeInfixCallFactory)

idea/idea-fir/tests/org/jetbrains/kotlin/idea/quickfix/HighLevelQuickFixTestGenerated.java

@@ -690,6 +690,11 @@ public class HighLevelQuickFixTestGenerated extends AbstractHighLevelQuickFixTes
         public void testUselessElvis() throws Exception {
             runTest("idea/testData/quickfix/expressions/uselessElvis.kt");
         }
+
+        @TestMetadata("uselessElvisRightIsNull.kt")
+        public void testUselessElvisRightIsNull() throws Exception {
+            runTest("idea/testData/quickfix/expressions/uselessElvisRightIsNull.kt");
+        }
     }
 
     @TestMetadata("idea/testData/quickfix/lateinit")

idea/idea-frontend-independent/src/org/jetbrains/kotlin/idea/core/frontendIndependentPsiUtils.kt

@@ -6,6 +6,7 @@
 package org.jetbrains.kotlin.idea.core
 
 import com.intellij.psi.PsiElement
+import org.jetbrains.kotlin.psi.KtExpression
 import org.jetbrains.kotlin.psi.KtParenthesizedExpression
 import org.jetbrains.kotlin.psi.KtPsiUtil
 
@@ -14,6 +15,12 @@ inline fun <reified T : PsiElement> PsiElement.replaced(newElement: T): T {
     return result as? T ?: (result as KtParenthesizedExpression).expression as T
 }
 
+fun KtExpression.dropEnclosingParenthesesIfPossible(): KtExpression {
+    val parent = parent as? KtParenthesizedExpression ?: return this
+    if (!KtPsiUtil.areParenthesesUseless(parent)) return this
+    return parent.replaced(this)
+}
+
 //todo make inline
 @Suppress("UNCHECKED_CAST")
 fun <T : PsiElement> T.copied(): T = copy() as T

idea/idea-frontend-independent/src/org/jetbrains/kotlin/idea/quickfix/RemoveUselessElvisFix.kt

@@ -0,0 +1,34 @@
+/*
+ * Copyright 2010-2021 JetBrains s.r.o. and Kotlin Programming Language contributors.
+ * Use of this source code is governed by the Apache 2.0 license that can be found in the license/LICENSE.txt file.
+ */
+
+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 com.intellij.psi.PsiElement
+import org.jetbrains.kotlin.idea.KotlinBundle
+import org.jetbrains.kotlin.idea.core.dropEnclosingParenthesesIfPossible
+import org.jetbrains.kotlin.idea.core.replaced
+import org.jetbrains.kotlin.psi.KtBinaryExpression
+import org.jetbrains.kotlin.psi.KtFile
+
+class RemoveUselessElvisFix(element: KtBinaryExpression) : KotlinPsiOnlyQuickFixAction<KtBinaryExpression>(element), CleanupFix {
+    override fun getFamilyName(): String = KotlinBundle.message("remove.useless.elvis.operator")
+
+    override fun getText(): String = familyName
+
+    override fun invoke(project: Project, editor: Editor?, file: KtFile) {
+        val element = element ?: return
+        element.replaced(element.left!!).dropEnclosingParenthesesIfPossible()
+    }
+
+    companion object : QuickFixesPsiBasedFactory<PsiElement>(PsiElement::class, PsiElementSuitabilityCheckers.ALWAYS_SUITABLE) {
+        override fun doCreateQuickFix(psiElement: PsiElement): List<IntentionAction> {
+            val expression = psiElement as? KtBinaryExpression ?: return emptyList()
+            return listOf(RemoveUselessElvisFix(expression))
+        }
+    }
+}

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

@@ -26,7 +26,7 @@ class RemoveUselessCastFix(element: KtBinaryExpressionWithTypeRHS) : KotlinQuick
     }
 
     companion object : KotlinSingleIntentionActionFactory() {
-        operator fun invoke(element: KtBinaryExpressionWithTypeRHS) = dropEnclosingParenthesesIfPossible(element.replaced(element.left))
+        operator fun invoke(element: KtBinaryExpressionWithTypeRHS) = element.replaced(element.left).dropEnclosingParenthesesIfPossible()
 
         override fun createAction(diagnostic: Diagnostic): KotlinQuickFixAction<KtBinaryExpressionWithTypeRHS>? {
             val expression = diagnostic.psiElement.getNonStrictParentOfType<KtBinaryExpressionWithTypeRHS>() ?: return null

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

@@ -1,44 +0,0 @@
-/*
- * Copyright 2010-2016 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.quickfix
-
-import com.intellij.openapi.editor.Editor
-import com.intellij.openapi.project.Project
-import org.jetbrains.kotlin.diagnostics.Diagnostic
-import org.jetbrains.kotlin.idea.KotlinBundle
-import org.jetbrains.kotlin.idea.core.dropEnclosingParenthesesIfPossible
-import org.jetbrains.kotlin.idea.core.replaced
-import org.jetbrains.kotlin.psi.KtBinaryExpression
-import org.jetbrains.kotlin.psi.KtFile
-
-class RemoveUselessElvisFix(element: KtBinaryExpression) : KotlinQuickFixAction<KtBinaryExpression>(element), CleanupFix {
-    override fun getFamilyName(): String = KotlinBundle.message("remove.useless.elvis.operator")
-
-    override fun getText(): String = familyName
-
-    override fun invoke(project: Project, editor: Editor?, file: KtFile) {
-        val element = element ?: return
-        dropEnclosingParenthesesIfPossible(element.replaced(element.left!!))
-    }
-
-    companion object : KotlinSingleIntentionActionFactory() {
-        override fun createAction(diagnostic: Diagnostic): KotlinQuickFixAction<KtBinaryExpression>? {
-            val expression = diagnostic.psiElement as? KtBinaryExpression ?: return null
-            return RemoveUselessElvisFix(expression)
-        }
-    }
-}

idea/testData/quickfix/expressions/uselessElvis.kt

@@ -2,5 +2,3 @@
 fun foo(a: String) {
     val b : String = a <caret>?: "s"
 }
-
-/* IGNORE_FIR */

idea/testData/quickfix/expressions/uselessElvis.kt.after

@@ -2,5 +2,3 @@
 fun foo(a: String) {
     val b : String = a<caret>
 }
-
-/* IGNORE_FIR */

idea/testData/quickfix/expressions/uselessElvisRightIsNull.kt

@@ -0,0 +1,4 @@
+// "Remove useless elvis operator" "true"
+fun foo(a: String?) {
+    val b = a <caret>?: null
+}

idea/testData/quickfix/expressions/uselessElvisRightIsNull.kt.after

@@ -0,0 +1,4 @@
+// "Remove useless elvis operator" "true"
+fun foo(a: String?) {
+    val b = a<caret>
+}

idea/tests/org/jetbrains/kotlin/idea/quickfix/QuickFixTestGenerated.java

@@ -7879,6 +7879,11 @@ public class QuickFixTestGenerated extends AbstractQuickFixTest {
         public void testUselessElvis() throws Exception {
             runTest("idea/testData/quickfix/expressions/uselessElvis.kt");
         }
+
+        @TestMetadata("uselessElvisRightIsNull.kt")
+        public void testUselessElvisRightIsNull() throws Exception {
+            runTest("idea/testData/quickfix/expressions/uselessElvisRightIsNull.kt");
+        }
     }
 
     @TestMetadata("idea/testData/quickfix/foldTryCatch")