plugins/InspectionGadgets/InspectionGadgetsAnalysis/src/com/siyeh/ig/bugs/ForLoopThatDoesntUseLoopVariableInspection.java

/*
 * Copyright 2003-2007 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.bugs;

import com.intellij.psi.*;
import com.siyeh.InspectionGadgetsBundle;
import com.siyeh.ig.BaseInspection;
import com.siyeh.ig.BaseInspectionVisitor;
import org.jetbrains.annotations.NotNull;

public class ForLoopThatDoesntUseLoopVariableInspection
  extends BaseInspection {

  @Override
  @NotNull
  public String getDisplayName() {
    return InspectionGadgetsBundle.message(
      "for.loop.not.use.loop.variable.display.name");
  }

  @Override
  @NotNull
  public String buildErrorString(Object... infos) {
    final boolean condition = ((Boolean)infos[0]).booleanValue();
    final boolean update = ((Boolean)infos[1]).booleanValue();
    if (condition && update) {
      return InspectionGadgetsBundle.message(
        "for.loop.not.use.loop.variable.problem.descriptor.both.condition.and.update");
    }
    if (condition) {
      return InspectionGadgetsBundle.message(
        "for.loop.not.use.loop.variable.problem.descriptor.condition");
    }
    return InspectionGadgetsBundle.message(
      "for.loop.not.use.loop.variable.problem.descriptor.update");
  }

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

  private static class ForLoopThatDoesntUseLoopVariableVisitor
    extends BaseInspectionVisitor {

    @Override
    public void visitForStatement(@NotNull PsiForStatement statement) {
      super.visitForStatement(statement);
      if (conditionUsesInitializer(statement)) {
        if (!updateUsesInitializer(statement)) {
          registerStatementError(statement,
                                 Boolean.FALSE, Boolean.TRUE);
        }
      }
      else {
        if (updateUsesInitializer(statement)) {
          registerStatementError(statement,
                                 Boolean.TRUE, Boolean.FALSE);
        }
        else {
          registerStatementError(statement,
                                 Boolean.TRUE, Boolean.TRUE);
        }
      }
    }

    private static boolean conditionUsesInitializer(
      PsiForStatement statement) {
      final PsiStatement initialization = statement.getInitialization();
      final PsiExpression condition = statement.getCondition();

      if (initialization == null) {
        return true;
      }
      if (condition == null) {
        return true;
      }
      if (!(initialization instanceof PsiDeclarationStatement)) {
        return true;
      }
      final PsiDeclarationStatement declaration =
        (PsiDeclarationStatement)initialization;
      final PsiElement[] declaredElements =
        declaration.getDeclaredElements();
      if (declaredElements.length != 1) {
        return true;
      }
      if (declaredElements[0] == null ||
          !(declaredElements[0] instanceof PsiLocalVariable)) {
        return true;
      }
      final PsiLocalVariable localVar =
        (PsiLocalVariable)declaredElements[0];
      return expressionUsesVariable(condition, localVar);
    }

    private static boolean updateUsesInitializer(PsiForStatement statement) {
      final PsiStatement initialization = statement.getInitialization();
      final PsiStatement update = statement.getUpdate();

      if (initialization == null) {
        return true;
      }
      if (update == null) {
        return true;
      }
      if (!(initialization instanceof PsiDeclarationStatement)) {
        return true;
      }
      final PsiDeclarationStatement declaration =
        (PsiDeclarationStatement)initialization;
      final PsiElement[] declaredElements =
        declaration.getDeclaredElements();
      if (declaredElements.length != 1) {
        return true;
      }
      if (declaredElements[0] == null ||
          !(declaredElements[0] instanceof PsiLocalVariable)) {
        return true;
      }
      final PsiLocalVariable localVar =
        (PsiLocalVariable)declaredElements[0];
      return statementUsesVariable(update, localVar);
    }

    private static boolean statementUsesVariable(PsiStatement statement,
                                                 PsiLocalVariable localVar) {
      final UseVisitor useVisitor = new UseVisitor(localVar);
      statement.accept(useVisitor);
      return useVisitor.isUsed();
    }

    private static boolean expressionUsesVariable(PsiExpression expression,
                                                  PsiLocalVariable localVar) {
      final UseVisitor useVisitor = new UseVisitor(localVar);
      expression.accept(useVisitor);
      return useVisitor.isUsed();
    }
  }

  private static class UseVisitor extends JavaRecursiveElementVisitor {

    private final PsiLocalVariable variable;
    private boolean used = false;

    private UseVisitor(PsiLocalVariable var) {
      super();
      variable = var;
    }

    @Override
    public void visitElement(@NotNull PsiElement element) {
      if (!used) {
        super.visitElement(element);
      }
    }

    @Override
    public void visitReferenceExpression(
      @NotNull PsiReferenceExpression ref) {
      if (used) {
        return;
      }
      super.visitReferenceExpression(ref);
      final PsiElement resolvedElement = ref.resolve();
      if (variable.equals(resolvedElement)) {
        used = true;
      }
    }

    public boolean isUsed() {
      return used;
    }
  }
}