Add quickfix for SENSELESS_NULL_IN_WHEN to remove redundant when branch

#KT-24556 Fixed

idea/resources-en/messages/KotlinBundle.properties

@@ -1138,6 +1138,7 @@ remove.useless.is.check=Remove useless is check
 remove.val.var.from.parameter=Remove 'val/var' from parameter
 remove.0.from.parameter=Remove ''{0}'' from parameter
 remove.else.branch=Remove else branch
+remove.branch=Remove branch
 rename.identifier.fix.text=Rename
 rename.to.0=Rename to ''{0}''
 rename.parameter.to.match.overridden.method=Rename parameter to match overridden method

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

@@ -276,7 +276,8 @@ class QuickFixRegistrar : QuickFixContributor {
         ELSE_MISPLACED_IN_WHEN.registerFactory(MoveWhenElseBranchFix)
         NO_ELSE_IN_WHEN.registerFactory(AddWhenElseBranchFix)
         NO_ELSE_IN_WHEN.registerFactory(AddWhenRemainingBranchesFix)
-        REDUNDANT_ELSE_IN_WHEN.registerFactory(RemoveWhenElseBranchFix)
+        REDUNDANT_ELSE_IN_WHEN.registerFactory(RemoveWhenBranchFix)
+        SENSELESS_NULL_IN_WHEN.registerFactory(RemoveWhenBranchFix)
         NON_EXHAUSTIVE_WHEN.registerFactory(AddWhenElseBranchFix)
         NON_EXHAUSTIVE_WHEN.registerFactory(AddWhenRemainingBranchesFix)
         NON_EXHAUSTIVE_WHEN_ON_SEALED_CLASS.registerFactory(AddWhenElseBranchFix)

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

@@ -19,12 +19,18 @@ 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.diagnostics.Errors
 import org.jetbrains.kotlin.idea.KotlinBundle
 import org.jetbrains.kotlin.psi.KtFile
 import org.jetbrains.kotlin.psi.KtWhenEntry
+import org.jetbrains.kotlin.psi.psiUtil.getStrictParentOfType
 
-class RemoveWhenElseBranchFix(element: KtWhenEntry) : KotlinQuickFixAction<KtWhenEntry>(element) {
-    override fun getFamilyName() = KotlinBundle.message("remove.else.branch")
+class RemoveWhenBranchFix(element: KtWhenEntry) : KotlinQuickFixAction<KtWhenEntry>(element) {
+    override fun getFamilyName() = if (element?.isElse == true) {
+        KotlinBundle.message("remove.else.branch")
+    } else {
+        KotlinBundle.message("remove.branch")
+    }
 
     override fun getText() = familyName
 
@@ -33,8 +39,15 @@ class RemoveWhenElseBranchFix(element: KtWhenEntry) : KotlinQuickFixAction<KtWhe
     }
 
     companion object : KotlinSingleIntentionActionFactory() {
-        override fun createAction(diagnostic: Diagnostic): RemoveWhenElseBranchFix? {
-            return (diagnostic.psiElement as? KtWhenEntry)?.let { RemoveWhenElseBranchFix(it) }
+        override fun createAction(diagnostic: Diagnostic): RemoveWhenBranchFix? {
+            return when (diagnostic.factory) {
+                Errors.REDUNDANT_ELSE_IN_WHEN ->
+                    (diagnostic.psiElement as? KtWhenEntry)?.let { RemoveWhenBranchFix(it) }
+                Errors.SENSELESS_NULL_IN_WHEN ->
+                    diagnostic.psiElement.getStrictParentOfType<KtWhenEntry>()?.let { RemoveWhenBranchFix(it) }
+                else ->
+                    null
+            }
         }
     }
 }

idea/testData/quickfix/when/removeRedundantBranch.kt

@@ -0,0 +1,9 @@
+// "Remove branch" "true"
+fun test(x: Int): String {
+    return when (x) {
+        1 -> "1"
+        2 -> "2"
+        <caret>null -> "null"
+        else -> ""
+    }
+}

idea/testData/quickfix/when/removeRedundantBranch.kt.after

@@ -0,0 +1,8 @@
+// "Remove branch" "true"
+fun test(x: Int): String {
+    return when (x) {
+        1 -> "1"
+        2 -> "2"
+        else -> ""
+    }
+}

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

@@ -15517,6 +15517,11 @@ public class QuickFixTestGenerated extends AbstractQuickFixTest {
             runTest("idea/testData/quickfix/when/noElseInWhenWithoutBranches.kt");
         }
 
+        @TestMetadata("removeRedundantBranch.kt")
+        public void testRemoveRedundantBranch() throws Exception {
+            runTest("idea/testData/quickfix/when/removeRedundantBranch.kt");
+        }
+
         @TestMetadata("removeRedundantElse.kt")
         public void testRemoveRedundantElse() throws Exception {
             runTest("idea/testData/quickfix/when/removeRedundantElse.kt");