IncompatibleMaskInspection.java

/*
 * Copyright 2003-2011 Dave Griffith, Bas Leijdekkers
 *
 * 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.siyeh.ig.bitwise;

import com.intellij.psi.*;
import com.intellij.psi.tree.IElementType;
import com.intellij.psi.util.ConstantExpressionUtil;
import com.intellij.psi.util.PsiUtil;
import com.siyeh.InspectionGadgetsBundle;
import com.siyeh.ig.BaseInspection;
import com.siyeh.ig.BaseInspectionVisitor;
import com.siyeh.ig.psiutils.ComparisonUtils;
import com.siyeh.ig.psiutils.ParenthesesUtils;
import org.jetbrains.annotations.NotNull;

public class IncompatibleMaskInspection extends BaseInspection {

  @Override
  @NotNull
  public String getID() {
    return "IncompatibleBitwiseMaskOperation";
  }

  @Override
  @NotNull
  public String getDisplayName() {
    return InspectionGadgetsBundle.message(
      "incompatible.mask.operation.display.name");
  }

  @Override
  @NotNull
  public String buildErrorString(Object... infos) {
    final PsiBinaryExpression binaryExpression =
      (PsiBinaryExpression)infos[0];
    final IElementType tokenType = binaryExpression.getOperationTokenType();
    if (tokenType.equals(JavaTokenType.EQEQ)) {
      return InspectionGadgetsBundle.message(
        "incompatible.mask.operation.problem.descriptor.always.false");
    }
    else {
      return InspectionGadgetsBundle.message(
        "incompatible.mask.operation.problem.descriptor.always.true");
    }
  }

  @Override
  public boolean isEnabledByDefault() {
    return true;
  }

  @Override
  public BaseInspectionVisitor buildVisitor() {
    return new IncompatibleMaskVisitor();
  }

  private static class IncompatibleMaskVisitor extends BaseInspectionVisitor {

    @Override
    public void visitBinaryExpression(
      @NotNull PsiBinaryExpression expression) {
      super.visitBinaryExpression(expression);
      final PsiExpression rhs = expression.getROperand();
      if (!ComparisonUtils.isEqualityComparison(expression)) {
        return;
      }
      final PsiType expressionType = expression.getType();
      if (expressionType == null) {
        return;
      }
      final PsiExpression strippedRhs =
        ParenthesesUtils.stripParentheses(rhs);
      if (strippedRhs == null) {
        return;
      }
      final PsiExpression lhs = expression.getLOperand();
      final PsiExpression strippedLhs =
        ParenthesesUtils.stripParentheses(lhs);
      if (strippedLhs == null) {
        return;
      }
      if (isConstantMask(strippedLhs) &&
          PsiUtil.isConstantExpression(strippedRhs)) {
        if (isIncompatibleMask((PsiBinaryExpression)strippedLhs,
                               strippedRhs)) {
          registerError(expression, expression);
        }
      }
      else if (isConstantMask(strippedRhs) &&
               PsiUtil.isConstantExpression(strippedLhs)) {
        if (isIncompatibleMask((PsiBinaryExpression)strippedRhs,
                               strippedLhs)) {
          registerError(expression, expression);
        }
      }
    }

    private static boolean isIncompatibleMask(
      PsiBinaryExpression maskExpression,
      PsiExpression constantExpression) {
      final IElementType tokenType =
        maskExpression.getOperationTokenType();
      final Object constantValue =
        ConstantExpressionUtil.computeCastTo(constantExpression,
                                             PsiType.LONG);
      if (constantValue == null) {
        return false;
      }
      final long constantLongValue = ((Long)constantValue).longValue();
      final PsiExpression maskRhs = maskExpression.getROperand();
      final PsiExpression maskLhs = maskExpression.getLOperand();
      final long constantMaskValue;
      if (PsiUtil.isConstantExpression(maskRhs)) {
        final Object rhsValue =
          ConstantExpressionUtil.computeCastTo(maskRhs,
                                               PsiType.LONG);
        if (rhsValue == null) {
          return false; // Might indeed be the case with "null" literal
          // whoes constant value evaluates to null. Check out (a|null) case.
        }
        constantMaskValue = ((Long)rhsValue).longValue();
      }
      else {
        final Object lhsValue =
          ConstantExpressionUtil.computeCastTo(maskLhs,
                                               PsiType.LONG);
        if (lhsValue == null) {
          return false;
        }
        constantMaskValue = ((Long)lhsValue).longValue();
      }

      if (tokenType.equals(JavaTokenType.OR)) {
        if ((constantMaskValue | constantLongValue) != constantLongValue) {
          return true;
        }
      }
      if (tokenType.equals(JavaTokenType.AND)) {
        if ((constantMaskValue | constantLongValue) != constantMaskValue) {
          return true;
        }
      }
      return false;
    }

    private static boolean isConstantMask(PsiExpression expression) {
      if (expression == null) {
        return false;
      }
      if (!(expression instanceof PsiBinaryExpression)) {
        return false;
      }
      final PsiBinaryExpression binaryExpression =
        (PsiBinaryExpression)expression;
      final IElementType tokenType =
        binaryExpression.getOperationTokenType();
      if (!tokenType.equals(JavaTokenType.OR) &&
          !tokenType.equals(JavaTokenType.AND)) {
        return false;
      }
      final PsiExpression rhs = binaryExpression.getROperand();
      if (PsiUtil.isConstantExpression(rhs)) {
        return true;
      }
      final PsiExpression lhs = binaryExpression.getLOperand();
      return PsiUtil.isConstantExpression(lhs);
    }
  }
}