From 0906b83847f6550f8e14a242558743c825a650d3 Mon Sep 17 00:00:00 2001
From: peter <peter@jetbrains.com>
Date: Wed, 8 Feb 2017 16:08:23 +0100
Subject: [PATCH] dfa: assume fields used before initialization are null
 (IDEA-110297)

---
 .../dataFlow/value/DfaExpressionFactory.java      | 15 +++++++++++++++
 .../fixture/FieldUsedBeforeInitialization.java    | 14 ++++++++++++++
 .../fixture/ImplicitlyInitializedField.java       |  2 +-
 .../codeInspection/DataFlowInspectionTest.java    |  2 ++
 4 files changed, 32 insertions(+), 1 deletion(-)
 create mode 100644 java/java-tests/testData/inspection/dataFlow/fixture/FieldUsedBeforeInitialization.java

diff --git a/java/java-analysis-impl/src/com/intellij/codeInspection/dataFlow/value/DfaExpressionFactory.java b/java/java-analysis-impl/src/com/intellij/codeInspection/dataFlow/value/DfaExpressionFactory.java
index 7d9ecdb76f7e..b336d42c2759 100644
--- a/java/java-analysis-impl/src/com/intellij/codeInspection/dataFlow/value/DfaExpressionFactory.java
+++ b/java/java-analysis-impl/src/com/intellij/codeInspection/dataFlow/value/DfaExpressionFactory.java
@@ -25,6 +25,7 @@ import com.intellij.openapi.util.text.StringUtil;
 import com.intellij.psi.*;
 import com.intellij.psi.impl.JavaConstantExpressionEvaluator;
 import com.intellij.psi.util.PropertyUtil;
+import com.intellij.psi.util.PsiTreeUtil;
 import com.intellij.psi.util.PsiUtil;
 import com.intellij.util.containers.ContainerUtil;
 import org.jetbrains.annotations.NotNull;
@@ -132,6 +133,10 @@ public class DfaExpressionFactory {
       }
 
       if (DfaValueFactory.isEffectivelyUnqualified(refExpr)) {
+        if (isFieldDereferenceBeforeInitialization(refExpr)) {
+          return myFactory.getConstFactory().getNull();
+        }
+
         return myFactory.getVarFactory().createVariableValue(var, refExpr.getType(), false, null);
       }
 
@@ -145,6 +150,16 @@ public class DfaExpressionFactory {
     return myFactory.createTypeValue(type, DfaPsiUtil.getElementNullability(type, var));
   }
 
+  private static boolean isFieldDereferenceBeforeInitialization(PsiReferenceExpression ref) {
+    PsiField placeField = PsiTreeUtil.getParentOfType(ref, PsiField.class, true, PsiClass.class, PsiLambdaExpression.class);
+    if (placeField == null) return false;
+
+    PsiElement target = ref.resolve();
+    return target instanceof PsiField &&
+           placeField.getContainingClass() == ((PsiField)target).getContainingClass() &&
+           ((PsiField)target).getInitializer() == null;
+  }
+
   @Nullable
   private static PsiModifierListOwner getAccessedVariableOrGetter(final PsiElement target) {
     if (target instanceof PsiVariable) {
diff --git a/java/java-tests/testData/inspection/dataFlow/fixture/FieldUsedBeforeInitialization.java b/java/java-tests/testData/inspection/dataFlow/fixture/FieldUsedBeforeInitialization.java
new file mode 100644
index 000000000000..dff3eda945b1
--- /dev/null
+++ b/java/java-tests/testData/inspection/dataFlow/fixture/FieldUsedBeforeInitialization.java
@@ -0,0 +1,14 @@
+class Foo {
+  String field;
+  String field2 = field.<warning descr="Method invocation 'substring' may produce 'java.lang.NullPointerException'">substring</warning>(1);
+  int field3 = field2.length();
+  Runnable r = new Runnable() {
+    public void run() {
+      System.out.println(field.hashCode());
+    }
+  };
+
+  Foo() {
+    field = "x";
+  }
+}
\ No newline at end of file
diff --git a/java/java-tests/testData/inspection/dataFlow/fixture/ImplicitlyInitializedField.java b/java/java-tests/testData/inspection/dataFlow/fixture/ImplicitlyInitializedField.java
index 0010c39a6772..b8b9a28972e2 100644
--- a/java/java-tests/testData/inspection/dataFlow/fixture/ImplicitlyInitializedField.java
+++ b/java/java-tests/testData/inspection/dataFlow/fixture/ImplicitlyInitializedField.java
@@ -1,7 +1,7 @@
 class Foo {
   String field;
   String field2;
-  int hash = field.hashCode();
+  int hash = field.<warning descr="Method invocation 'hashCode' may produce 'java.lang.NullPointerException'">hashCode</warning>();
 
   Foo(String f2) {
     field2 = f2;
diff --git a/java/java-tests/testSrc/com/intellij/codeInspection/DataFlowInspectionTest.java b/java/java-tests/testSrc/com/intellij/codeInspection/DataFlowInspectionTest.java
index d68abce179b9..5da2b3f67dc5 100644
--- a/java/java-tests/testSrc/com/intellij/codeInspection/DataFlowInspectionTest.java
+++ b/java/java-tests/testSrc/com/intellij/codeInspection/DataFlowInspectionTest.java
@@ -421,6 +421,8 @@ public class DataFlowInspectionTest extends DataFlowInspectionTestCase {
 
   public void testDivisionByZero() { doTestReportConstantReferences(); }
 
+  public void testFieldUsedBeforeInitialization() { doTest(); }
+
   public void testImplicitlyInitializedField() {
     PlatformTestUtil.registerExtension(ImplicitUsageProvider.EP_NAME, new ImplicitUsageProvider() {
       @Override