java/java-impl/src/com/intellij/codeInspection/sillyAssignment/SillyAssignmentInspection.java

   1 /*
   2  * Copyright 2000-2009 JetBrains s.r.o.
   3  *
   4  * Licensed under the Apache License, Version 2.0 (the "License");
   5  * you may not use this file except in compliance with the License.
   6  * You may obtain a copy of the License at
   7  *
   8  * http://www.apache.org/licenses/LICENSE-2.0
   9  *
  10  * Unless required by applicable law or agreed to in writing, software
  11  * distributed under the License is distributed on an "AS IS" BASIS,
  12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  13  * See the License for the specific language governing permissions and
  14  * limitations under the License.
  15  */
  16 package com.intellij.codeInspection.sillyAssignment;
  17
  18 import com.intellij.codeInsight.daemon.JavaErrorMessages;
  19 import com.intellij.codeInspection.BaseJavaLocalInspectionTool;
  20 import com.intellij.codeInspection.LocalQuickFix;
  21 import com.intellij.codeInspection.ProblemHighlightType;
  22 import com.intellij.codeInspection.ProblemsHolder;
  23 import com.intellij.openapi.util.Comparing;
  24 import com.intellij.psi.*;
  25 import com.intellij.psi.util.PsiUtil;
  26 import org.jetbrains.annotations.NonNls;
  27 import org.jetbrains.annotations.NotNull;
  28
  29 /**
  30  * User: anna
  31  * Date: 15-Nov-2005
  32  */
  33 public class SillyAssignmentInspection extends BaseJavaLocalInspectionTool {
  34   @NotNull
  35   public String getGroupDisplayName() {
  36     return "";
  37   }
  38
  39   @NotNull
  40   public String getDisplayName() {
  41     return JavaErrorMessages.message("assignment.to.itself");
  42   }
  43
  44   @NotNull
  45   @NonNls
  46   public String getShortName() {
  47     return "SillyAssignment";
  48   }
  49
  50   public boolean isEnabledByDefault() {
  51     return true;
  52   }
  53
  54   @NotNull
  55   public PsiElementVisitor buildVisitor(@NotNull final ProblemsHolder holder, boolean isOnTheFly) {
  56     return new JavaElementVisitor() {
  57
  58       @Override public void visitAssignmentExpression(PsiAssignmentExpression expression) {
  59         checkSillyAssignment(expression, holder);
  60       }
  61
  62       @Override public void visitReferenceExpression(PsiReferenceExpression expression) {
  63         visitElement(expression);
  64       }
  65
  66       @Override public void visitVariable(final PsiVariable variable) {
  67         final PsiExpression initializer = variable.getInitializer();
  68         if (initializer instanceof PsiAssignmentExpression) {
  69           final PsiExpression lExpr = ((PsiAssignmentExpression)initializer).getLExpression();
  70           if (lExpr instanceof PsiReferenceExpression) {
  71             final PsiReferenceExpression refExpr = (PsiReferenceExpression)lExpr;
  72             if (!refExpr.isQualified() && refExpr.isReferenceTo(variable)) {
  73               holder.registerProblem(lExpr, JavaErrorMessages.message("assignment.to.declared.variable", variable.getName()),
  74                                      ProblemHighlightType.LIKE_UNUSED_SYMBOL, (LocalQuickFix[])null);
  75             }
  76           }
  77         }
  78       }
  79     };
  80   }
  81
  82   private static void checkSillyAssignment(PsiAssignmentExpression assignment, ProblemsHolder holder) {
  83     if (assignment.getOperationSign().getTokenType() != JavaTokenType.EQ) return;
  84     PsiExpression lExpression = assignment.getLExpression();
  85     PsiExpression rExpression = assignment.getRExpression();
  86     if (rExpression == null) return;
  87     lExpression = PsiUtil.deparenthesizeExpression(lExpression);
  88     rExpression = PsiUtil.deparenthesizeExpression(rExpression);
  89     if (!(lExpression instanceof PsiReferenceExpression)) return;
  90     PsiReferenceExpression rRef;
  91     if (!(rExpression instanceof PsiReferenceExpression)) {
  92       if (!(rExpression instanceof PsiAssignmentExpression)) return;
  93       final PsiAssignmentExpression rAssignmentExpression = (PsiAssignmentExpression)rExpression;
  94       final PsiExpression assignee = rAssignmentExpression.getLExpression();
  95       if (!(assignee instanceof PsiReferenceExpression)) return;
  96       rRef = (PsiReferenceExpression)assignee;
  97     } else {
  98       rRef = (PsiReferenceExpression)rExpression;
  99     }
 100     PsiReferenceExpression lRef = (PsiReferenceExpression)lExpression;
 101     PsiManager manager = assignment.getManager();
 102     if (!sameInstanceReferences(lRef, rRef, manager)) return;
 103     holder.registerProblem(assignment, JavaErrorMessages.message("assignment.to.itself"), ProblemHighlightType.LIKE_UNUSED_SYMBOL, (LocalQuickFix[])null);
 104   }
 105
 106   /**
 107    * @return true if both expressions resolve to the same variable/class or field in the same instance of the class
 108    */
 109   private static boolean sameInstanceReferences(PsiReferenceExpression lRef, PsiReferenceExpression rRef, PsiManager manager) {
 110     PsiElement lResolved = lRef.resolve();
 111     PsiElement rResolved = rRef.resolve();
 112     if (!manager.areElementsEquivalent(lResolved, rResolved)) return false;
 113
 114     PsiExpression lQualifier = lRef.getQualifierExpression();
 115     PsiExpression rQualifier = rRef.getQualifierExpression();
 116     if (lQualifier instanceof PsiReferenceExpression && rQualifier instanceof PsiReferenceExpression) {
 117       return sameInstanceReferences((PsiReferenceExpression)lQualifier, (PsiReferenceExpression)rQualifier, manager);
 118     }
 119     if (Comparing.equal(lQualifier, rQualifier)) return true;
 120     boolean lThis = lQualifier == null || lQualifier instanceof PsiThisExpression;
 121     boolean rThis = rQualifier == null || rQualifier instanceof PsiThisExpression;
 122     return lThis && rThis;
 123   }
 124
 125 }