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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 2000-2014 JetBrains s.r.o.
 *
 * 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.siyeh.ig.BaseInspection;
import com.siyeh.ig.BaseInspectionVisitor;
import com.siyeh.ig.InspectionGadgetsFix;
import com.siyeh.ig.fixes.ExtractParameterAsLocalVariableFix;
import com.siyeh.ig.psiutils.ParenthesesUtils;
import com.siyeh.ig.psiutils.VariableAccessUtils;
import org.jetbrains.annotations.NotNull;
import org.jetbrains.annotations.Nullable;

/**
 * @author Bas Leijdekkers
 */
public abstract class BaseAssignmentToParameterInspection extends BaseInspection {

  @SuppressWarnings({"PublicField"})
  public boolean ignoreTransformationOfOriginalParameter = false;

  @Override
  protected InspectionGadgetsFix buildFix(Object... infos) {
    return new ExtractParameterAsLocalVariableFix();
  }

  protected abstract boolean isCorrectScope(PsiElement declarationScope);

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

  private class AssignmentToParameterVisitor extends BaseInspectionVisitor {

    @Override
    public void visitAssignmentExpression(@NotNull PsiAssignmentExpression expression) {
      super.visitAssignmentExpression(expression);
      final PsiExpression lhs = expression.getLExpression();
      final PsiParameter parameter = getParameter(lhs);
      if (parameter == null) {
        return;
      }
      if (ignoreTransformationOfOriginalParameter) {
        final PsiExpression rhs = expression.getRExpression();
        if (rhs != null && VariableAccessUtils.variableIsUsed(parameter, rhs)) {
          return;
        }
        final IElementType tokenType =
          expression.getOperationTokenType();
        if (tokenType == JavaTokenType.PLUSEQ ||
            tokenType == JavaTokenType.MINUSEQ ||
            tokenType == JavaTokenType.ASTERISKEQ ||
            tokenType == JavaTokenType.DIVEQ ||
            tokenType == JavaTokenType.ANDEQ ||
            tokenType == JavaTokenType.OREQ ||
            tokenType == JavaTokenType.XOREQ ||
            tokenType == JavaTokenType.PERCEQ ||
            tokenType == JavaTokenType.LTLTEQ ||
            tokenType == JavaTokenType.GTGTEQ ||
            tokenType == JavaTokenType.GTGTGTEQ) {
          return;
        }
      }
      registerError(lhs);
    }

    @Override
    public void visitPrefixExpression(@NotNull PsiPrefixExpression expression) {
      if (ignoreTransformationOfOriginalParameter) {
        return;
      }
      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;
      }
      final PsiParameter parameter = getParameter(operand);
      if (parameter == null) {
        return;
      }
      registerError(operand);
    }

    @Override
    public void visitPostfixExpression(@NotNull PsiPostfixExpression expression) {
      if (ignoreTransformationOfOriginalParameter) {
        return;
      }
      super.visitPostfixExpression(expression);
      final IElementType tokenType = expression.getOperationTokenType();
      if (!tokenType.equals(JavaTokenType.PLUSPLUS) && !tokenType.equals(JavaTokenType.MINUSMINUS)) {
        return;
      }
      final PsiExpression operand = expression.getOperand();
      final PsiParameter parameter = getParameter(operand);
      if (parameter == null) {
        return;
      }
      registerError(operand);
    }

    @Nullable
    private PsiParameter getParameter(PsiExpression expression) {
      expression = ParenthesesUtils.stripParentheses(expression);
      if (!(expression instanceof PsiReferenceExpression)) {
        return null;
      }
      final PsiReferenceExpression referenceExpression = (PsiReferenceExpression)expression;
      final PsiElement variable = referenceExpression.resolve();
      if (!(variable instanceof PsiParameter)) {
        return null;
      }
      final PsiParameter parameter = (PsiParameter)variable;
      final PsiElement declarationScope = parameter.getDeclarationScope();
      if (!isCorrectScope(declarationScope)) {
        return null;
      }
      return parameter;
    }
  }
}