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A packaging of the IntelliJ Community Edition java-analysis-impl library. This is release number 1 of trunk branch 142.
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/*
 * 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.assignment;

import com.intellij.psi.*;
import com.intellij.psi.tree.IElementType;
import com.intellij.psi.util.PsiTreeUtil;
import com.intellij.codeInspection.ui.SingleCheckboxOptionsPanel;
import com.siyeh.InspectionGadgetsBundle;
import com.siyeh.ig.BaseInspection;
import com.siyeh.ig.BaseInspectionVisitor;
import com.siyeh.ig.InspectionGadgetsFix;
import com.siyeh.ig.fixes.ExtractParameterAsLocalVariableFix;
import com.siyeh.ig.psiutils.WellFormednessUtils;
import org.jetbrains.annotations.NotNull;
import org.jetbrains.annotations.Nullable;

import javax.swing.*;

public class AssignmentToForLoopParameterInspection
  extends BaseInspection {

  /**
   * @noinspection PublicField for externalization purposes
   */
  public boolean m_checkForeachParameters = false;

  @Override
  @NotNull
  public String getDisplayName() {
    return InspectionGadgetsBundle.message(
      "assignment.to.for.loop.parameter.display.name");
  }

  @Override
  @NotNull
  public String buildErrorString(Object... infos) {
    return InspectionGadgetsBundle.message(
      "assignment.to.for.loop.parameter.problem.descriptor");
  }

  @Override
  @Nullable
  public JComponent createOptionsPanel() {
    return new SingleCheckboxOptionsPanel(
      InspectionGadgetsBundle.message(
        "assignment.to.for.loop.parameter.check.foreach.option"),
      this, "m_checkForeachParameters");
  }

  @Override
  protected InspectionGadgetsFix buildFix(Object... infos) {
    final Boolean foreachLoop = (Boolean)infos[0];
    if (!foreachLoop.booleanValue()) {
      return null;
    }
    return new ExtractParameterAsLocalVariableFix();
  }

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

  private class AssignmentToForLoopParameterVisitor
    extends BaseInspectionVisitor {

    @Override
    public void visitAssignmentExpression(
      @NotNull PsiAssignmentExpression expression) {
      super.visitAssignmentExpression(expression);
      if (!WellFormednessUtils.isWellFormed(expression)) {
        return;
      }
      final PsiExpression lhs = expression.getLExpression();
      checkForForLoopParam(lhs);
      checkForForeachLoopParam(lhs);
    }

    @Override
    public void visitPrefixExpression(
      @NotNull PsiPrefixExpression expression) {
      super.visitPrefixExpression(expression);
      final IElementType tokenType = expression.getOperationTokenType();
      if (!tokenType.equals(JavaTokenType.PLUSPLUS) &&
          !tokenType.equals(JavaTokenType.MINUSMINUS)) {
        return;
      }
      final PsiExpression operand = expression.getOperand();
      if (operand == null) {
        return;
      }
      checkForForLoopParam(operand);
      checkForForeachLoopParam(operand);  //sensible due to autoboxing/unboxing
    }

    @Override
    public void visitPostfixExpression(
      @NotNull PsiPostfixExpression expression) {
      super.visitPostfixExpression(expression);
      final IElementType tokenType = expression.getOperationTokenType();
      if (!tokenType.equals(JavaTokenType.PLUSPLUS) &&
          !tokenType.equals(JavaTokenType.MINUSMINUS)) {
        return;
      }
      final PsiExpression operand = expression.getOperand();
      checkForForLoopParam(operand);
      checkForForeachLoopParam(operand);  //sensible due to autoboxing/unboxing
    }

    private void checkForForLoopParam(PsiExpression expression) {
      if (!(expression instanceof PsiReferenceExpression)) {
        return;
      }
      final PsiReferenceExpression referenceExpression =
        (PsiReferenceExpression)expression;
      final PsiElement element = referenceExpression.resolve();
      if (!(element instanceof PsiLocalVariable)) {
        return;
      }
      final PsiLocalVariable variable = (PsiLocalVariable)element;
      final PsiElement variableParent = variable.getParent();
      if (!(variableParent instanceof PsiDeclarationStatement)) {
        return;
      }
      final PsiDeclarationStatement declarationStatement =
        (PsiDeclarationStatement)variableParent;
      final PsiElement parent = declarationStatement.getParent();
      if (!(parent instanceof PsiForStatement)) {
        return;
      }
      final PsiForStatement forStatement = (PsiForStatement)parent;
      final PsiStatement initialization =
        forStatement.getInitialization();
      if (initialization == null) {
        return;
      }
      if (!initialization.equals(declarationStatement)) {
        return;
      }
      if (!isInForStatementBody(expression, forStatement)) {
        return;
      }
      registerError(expression, Boolean.FALSE);
    }

    private void checkForForeachLoopParam(PsiExpression expression) {
      if (!m_checkForeachParameters) {
        return;
      }
      if (!(expression instanceof PsiReferenceExpression)) {
        return;
      }
      final PsiReferenceExpression referenceExpression =
        (PsiReferenceExpression)expression;
      final PsiElement element = referenceExpression.resolve();
      if (!(element instanceof PsiParameter)) {
        return;
      }
      final PsiParameter parameter = (PsiParameter)element;
      if (!(parameter.getParent() instanceof PsiForeachStatement)) {
        return;
      }
      registerError(expression, Boolean.TRUE);
    }

    private boolean isInForStatementBody(PsiExpression expression,
                                         PsiForStatement statement) {
      final PsiStatement body = statement.getBody();
      if (body == null) {
        return false;
      }
      return PsiTreeUtil.isAncestor(body, expression, true);
    }
  }
}