MultipleUnaryOperatorsInMethodCall
Avoid having multiple unary operators acting on the same variable in a method call

Severity
SUGGESTION
Has Fix?
NO_FIX

The problem

Increment operators in method calls are dubious and while argument lists are evaluated left-to-right, documentation suggests that code not rely on this specification. In addition, code is clearer when each expression contains at most one side effect.

Suppression

Suppress false positives by adding the suppression annotation @SuppressWarnings("MultipleUnaryOperatorsInMethodCall") to the enclosing element.


Positive examples

MultipleUnaryOperatorsInMethodCallPositiveCases.java

/*
 * Copyright 2017 The Error Prone Authors.
 *
 * 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 com.google.errorprone.bugpatterns.testdata;

/** @author sulku@google.com (Marsela Sulku) */
public class MultipleUnaryOperatorsInMethodCallPositiveCases {
  public static void tests(int a, int b) {
    /** these cases do not have suggested fixes */

    // BUG: Diagnostic contains: Avoid having multiple unary operators acting
    twoArgs(a++, a--);
    // BUG: Diagnostic contains: Avoid having multiple unary operators acting
    twoArgs(a--, ++a);
    // BUG: Diagnostic contains: Avoid having multiple unary operators acting
    twoArgs(++a, a++);
    // BUG: Diagnostic contains: Avoid having multiple unary operators acting
    twoArgs(--a, --a);

    // BUG: Diagnostic contains: Avoid having multiple unary operators acting
    threeArgs(a++, b++, b++);
    // BUG: Diagnostic contains: Avoid having multiple unary operators acting
    threeArgs(a++, b, a++);
    // BUG: Diagnostic contains: Avoid having multiple unary operators acting
    threeArgs(++a, b++, --b);
    // BUG: Diagnostic contains: Avoid having multiple unary operators acting
    threeArgs(++a, a++, b);
    // BUG: Diagnostic contains: Avoid having multiple unary operators acting
    threeArgs(++a, a++, a);
    // BUG: Diagnostic contains: Avoid having multiple unary operators acting
    threeArgs(++a, a++, a--);
  }

  public static void twoArgs(int a, int b) {}

  public static void threeArgs(int a, int b, int c) {}

  public static int someFunction(int a) {
    return 0;
  }
}

Negative examples

MultipleUnaryOperatorsInMethodCallNegativeCases.java

/*
 * Copyright 2017 The Error Prone Authors.
 *
 * 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 com.google.errorprone.bugpatterns.testdata;

/** @author sulku@google.com (Marsela Sulku) */
public class MultipleUnaryOperatorsInMethodCallNegativeCases {
  public static void tests(int a, int b) {
    testMethod(a, b);
    testMethod(a + 1, b);
    testMethod(b, a + 1);
    testMethod(a++, b);
    testMethod(--a, b);
    testMethod(a, b--);
    testMethod(a, ++b);
  }

  public static void testMethod(int one, int two) {}
}