Bug fixes in DefUseInspection

IDEA-187758 Variable initializer is redundant false-negative with chained constructors
IDEA-187756 Variable initializer is redundant false-positive when the value is read before write

java/java-analysis-impl/src/com/intellij/codeInspection/defUse/DefUseInspectionBase.java

@@ -1,11 +1,16 @@
 // Copyright 2000-2017 JetBrains s.r.o. Use of this source code is governed by the Apache 2.0 license that can be found in the LICENSE file.
 package com.intellij.codeInspection.defUse;
 
+import com.intellij.codeInsight.ExpressionUtil;
 import com.intellij.codeInsight.daemon.GroupNames;
 import com.intellij.codeInsight.daemon.impl.analysis.HighlightControlFlowUtil;
+import com.intellij.codeInsight.daemon.impl.analysis.JavaHighlightUtil;
 import com.intellij.codeInsight.daemon.impl.quickfix.RemoveUnusedVariableUtil;
 import com.intellij.codeInspection.*;
 import com.intellij.psi.*;
+import com.intellij.psi.controlFlow.AnalysisCanceledException;
+import com.intellij.psi.controlFlow.ControlFlow;
+import com.intellij.psi.controlFlow.ControlFlowUtil;
 import com.intellij.psi.controlFlow.DefUseUtil;
 import com.intellij.psi.util.PsiTreeUtil;
 import com.intellij.util.ObjectUtils;
@@ -16,10 +21,8 @@ import org.jetbrains.annotations.NotNull;
 
 import javax.swing.*;
 import java.awt.*;
-import java.util.ArrayList;
-import java.util.Collections;
+import java.util.*;
 import java.util.List;
-import java.util.Set;
 
 public class DefUseInspectionBase extends AbstractBaseJavaLocalInspectionTool {
   public boolean REPORT_PREFIX_EXPRESSIONS;
@@ -66,15 +69,7 @@ public class DefUseInspectionBase extends AbstractBaseJavaLocalInspectionTool {
     List<DefUseUtil.Info> unusedDefs = DefUseUtil.getUnusedDefs(body, usedVariables);
 
     if (unusedDefs != null && !unusedDefs.isEmpty()) {
-      Collections.sort(unusedDefs, (o1, o2) -> {
-        int offset1 = o1.getContext().getTextOffset();
-        int offset2 = o2.getContext().getTextOffset();
-
-        if (offset1 == offset2) return 0;
-        if (offset1 < offset2) return -1;
-
-        return 1;
-      });
+      unusedDefs.sort(Comparator.comparingInt(o -> o.getContext().getTextOffset()));
 
       for (DefUseUtil.Info info : unusedDefs) {
         PsiElement context = info.getContext();
@@ -179,10 +174,21 @@ public class DefUseInspectionBase extends AbstractBaseJavaLocalInspectionTool {
       return false;
     }
     for (PsiMethod constructor : constructors) {
+      if (JavaHighlightUtil.getChainedConstructors(constructor) != null) continue;
       final PsiCodeBlock body = constructor.getBody();
       if (body == null || !HighlightControlFlowUtil.variableDefinitelyAssignedIn(field, body)) {
         return false;
       }
+      try {
+        ControlFlow flow = HighlightControlFlowUtil.getControlFlowNoConstantEvaluate(body);
+        if (ControlFlowUtil.getReadBeforeWrite(flow).stream()
+                           .anyMatch(read -> ExpressionUtil.isEffectivelyUnqualified(read) && read.isReferenceTo(field))) {
+          return false;
+        }
+      }
+      catch (AnalysisCanceledException e) {
+        return false;
+      }
     }
     return true;
   }

java/java-tests/testData/inspection/defUse/FieldInitializerChainedConstructor.java

@@ -0,0 +1,15 @@
+class Foo {
+  String s = <warning descr="Variable 's' initializer '\"foo\"' is redundant">"foo"</warning>;
+
+  Foo(String _s) {
+    s = _s;
+  }
+
+  Foo() {
+    this("foo");
+  }
+
+  public static void main(String[] args) {
+    new Foo();
+  }
+}

java/java-tests/testData/inspection/defUse/FieldInitializerUsedInMethodReference.java

@@ -0,0 +1,15 @@
+import java.util.function.Supplier;
+
+class Foo {
+  String s = "foo";
+
+  Foo() {
+    Supplier<String> fn = s::trim;
+    s = "bar";
+    System.out.println(fn.get());
+  }
+
+  public static void main(String[] args) {
+    new Foo();
+  }
+}

java/java-tests/testSrc/com/intellij/java/codeInspection/DefUseTest.java

@@ -17,7 +17,9 @@ package com.intellij.java.codeInspection;
 
 import com.intellij.JavaTestUtil;
 import com.intellij.codeInspection.defUse.DefUseInspection;
+import com.intellij.testFramework.LightProjectDescriptor;
 import com.intellij.testFramework.fixtures.LightCodeInsightFixtureTestCase;
+import org.jetbrains.annotations.NotNull;
 
 public class DefUseTest extends LightCodeInsightFixtureTestCase {
   @Override
@@ -63,6 +65,14 @@ public class DefUseTest extends LightCodeInsightFixtureTestCase {
     myFixture.enableInspections(inspection);
     myFixture.testHighlighting(getTestName(false) + ".java");
   }
+  public void testFieldInitializerUsedInMethodReference() { doTest(); }
+  public void testFieldInitializerChainedConstructor() { doTest(); }
+
+  @NotNull
+  @Override
+  protected LightProjectDescriptor getProjectDescriptor() {
+    return JAVA_10;
+  }
 
   private void doTest() {
     myFixture.enableInspections(new DefUseInspection());