Quick-Fixes: Drop unnecessary parentheses when simplifying cast expressions

#KT-6501 Fixed

idea/src/org/jetbrains/kotlin/idea/quickfix/RemoveRightPartOfBinaryExpressionFix.java

@@ -18,14 +18,12 @@ package org.jetbrains.kotlin.idea.quickfix;
 
 import com.intellij.openapi.editor.Editor;
 import com.intellij.openapi.project.Project;
+import com.intellij.psi.PsiElement;
 import com.intellij.util.IncorrectOperationException;
 import org.jetbrains.annotations.NotNull;
 import org.jetbrains.kotlin.diagnostics.Diagnostic;
 import org.jetbrains.kotlin.idea.JetBundle;
-import org.jetbrains.kotlin.psi.JetBinaryExpression;
-import org.jetbrains.kotlin.psi.JetBinaryExpressionWithTypeRHS;
-import org.jetbrains.kotlin.psi.JetExpression;
-import org.jetbrains.kotlin.psi.JetFile;
+import org.jetbrains.kotlin.psi.*;
 
 public class RemoveRightPartOfBinaryExpressionFix<T extends JetExpression> extends JetIntentionAction<T> {
     private final String message;
@@ -47,13 +45,19 @@ public class RemoveRightPartOfBinaryExpressionFix<T extends JetExpression> exten
 
     @Override
     public void invoke(@NotNull Project project, Editor editor, JetFile file) throws IncorrectOperationException {
+        PsiElement newElement = null;
+
         if (element instanceof JetBinaryExpression) {
-            JetBinaryExpression newElement = (JetBinaryExpression) element.copy();
-            element.replace(newElement.getLeft());
+            //noinspection ConstantConditions
+            newElement = element.replace(((JetBinaryExpression) element.copy()).getLeft());
         }
         else if (element instanceof JetBinaryExpressionWithTypeRHS) {
-            JetBinaryExpressionWithTypeRHS newElement = (JetBinaryExpressionWithTypeRHS) element.copy();
-            element.replace(newElement.getLeft());
+            newElement = element.replace(((JetBinaryExpressionWithTypeRHS) element.copy()).getLeft());
+        }
+
+        PsiElement parent = newElement != null ? newElement.getParent() : null;
+        if (parent instanceof JetParenthesizedExpression && JetPsiUtil.areParenthesesUseless((JetParenthesizedExpression) parent)) {
+            parent.replace(newElement);
         }
     }
 

idea/testData/quickfix/expressions/afterRemoveUselessCastInParens.kt

@@ -0,0 +1,7 @@
+// "Remove cast" "true"
+fun test(x: Any): Int {
+    if (x is String) {
+        return x.length()
+    }
+    return -1
+}

idea/testData/quickfix/expressions/beforeRemoveUselessCastInParens.kt

@@ -0,0 +1,7 @@
+// "Remove cast" "true"
+fun test(x: Any): Int {
+    if (x is String) {
+        return (x <caret>as String).length()
+    }
+    return -1
+}

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

@@ -2831,6 +2831,12 @@ public class QuickFixTestGenerated extends AbstractQuickFixTest {
             doTest(fileName);
         }
 
+        @TestMetadata("beforeRemoveUselessCastInParens.kt")
+        public void testRemoveUselessCastInParens() throws Exception {
+            String fileName = JetTestUtils.navigationMetadata("idea/testData/quickfix/expressions/beforeRemoveUselessCastInParens.kt");
+            doTest(fileName);
+        }
+
         @TestMetadata("beforeRemoveUselessCastUnderSmartCast.kt")
         public void testRemoveUselessCastUnderSmartCast() throws Exception {
             String fileName = JetTestUtils.navigationMetadata("idea/testData/quickfix/expressions/beforeRemoveUselessCastUnderSmartCast.kt");