From af07f88aef6608544b4921a8c6ccc830debbe746 Mon Sep 17 00:00:00 2001
From: peter <peter@jetbrains.com>
Date: Mon, 12 Oct 2015 13:25:17 +0200
Subject: [PATCH] IDEA-146122 Wrong 'can produce NPE' after comparing with enum
 constant

---
 .../dataFlow/DfaMemoryStateImpl.java          | 10 ++++++++-
 .../fixture/CompareToEnumConstant.java        | 21 +++++++++++++++++++
 .../DataFlowInspectionTest.java               |  1 +
 3 files changed, 31 insertions(+), 1 deletion(-)
 create mode 100644 java/java-tests/testData/inspection/dataFlow/fixture/CompareToEnumConstant.java

diff --git a/java/java-analysis-impl/src/com/intellij/codeInspection/dataFlow/DfaMemoryStateImpl.java b/java/java-analysis-impl/src/com/intellij/codeInspection/dataFlow/DfaMemoryStateImpl.java
index e9f9d49eb3e5..b015f5bfa80d 100644
--- a/java/java-analysis-impl/src/com/intellij/codeInspection/dataFlow/DfaMemoryStateImpl.java
+++ b/java/java-analysis-impl/src/com/intellij/codeInspection/dataFlow/DfaMemoryStateImpl.java
@@ -30,6 +30,7 @@ import com.intellij.openapi.util.Pair;
 import com.intellij.openapi.util.UnorderedPair;
 import com.intellij.openapi.util.text.StringUtil;
 import com.intellij.psi.JavaTokenType;
+import com.intellij.psi.PsiEnumConstant;
 import com.intellij.psi.PsiPrimitiveType;
 import com.intellij.psi.PsiType;
 import com.intellij.psi.util.TypeConversionUtil;
@@ -833,7 +834,9 @@ public class DfaMemoryStateImpl implements DfaMemoryState {
       for (long encodedPair : myDistinctClasses.toArray()) {
         EqClass c1 = myEqClasses.get(low(encodedPair));
         EqClass c2 = myEqClasses.get(high(encodedPair));
-        if (c1.findConstant(false) != null && c2.findConstant(false) != null) {
+        DfaConstValue const1 = (DfaConstValue)c1.findConstant(false);
+        DfaConstValue const2 = (DfaConstValue)c2.findConstant(false);
+        if (const1 != null && const2 != null && !preserveConstantDistinction(const1.getValue(), const2.getValue())) {
           myDistinctClasses.remove(encodedPair);
         }
       }
@@ -851,6 +854,11 @@ public class DfaMemoryStateImpl implements DfaMemoryState {
     return true;
   }
 
+  private static boolean preserveConstantDistinction(final Object c1, final Object c2) {
+    return c1 == null && c2 instanceof PsiEnumConstant ||
+           c2 == null && c1 instanceof PsiEnumConstant;
+  }
+
   private boolean areCompatibleConstants(int i1, int i2) {
     Double dv1 = getDoubleValue(i1);
     return dv1 != null && dv1.equals(getDoubleValue(i2));
diff --git a/java/java-tests/testData/inspection/dataFlow/fixture/CompareToEnumConstant.java b/java/java-tests/testData/inspection/dataFlow/fixture/CompareToEnumConstant.java
new file mode 100644
index 000000000000..db5c5197a5ef
--- /dev/null
+++ b/java/java-tests/testData/inspection/dataFlow/fixture/CompareToEnumConstant.java
@@ -0,0 +1,21 @@
+import org.jetbrains.annotations.Nullable;
+
+enum MyEnum {
+  ITEM,
+  ANOTHER_ITEM,
+  LOL_ITEM;
+}
+
+@SuppressWarnings({"UseOfSystemOutOrSystemErr", "unused"})
+class Main {
+  void foo(@Nullable MyEnum myEnum) {
+    if (myEnum == null) return;
+    switch (myEnum) {
+      case ITEM:
+      case ANOTHER_ITEM:
+        System.out.println(myEnum == MyEnum.ITEM ? "item" : "another");
+        myEnum.name();
+      default:
+    }
+  }
+}
\ No newline at end of file
diff --git a/java/java-tests/testSrc/com/intellij/codeInspection/DataFlowInspectionTest.java b/java/java-tests/testSrc/com/intellij/codeInspection/DataFlowInspectionTest.java
index b08a702b883b..fdcb1a6d2c10 100644
--- a/java/java-tests/testSrc/com/intellij/codeInspection/DataFlowInspectionTest.java
+++ b/java/java-tests/testSrc/com/intellij/codeInspection/DataFlowInspectionTest.java
@@ -94,6 +94,7 @@ public class DataFlowInspectionTest extends LightCodeInsightFixtureTestCase {
   public void testEqualsEnumConstant() throws Throwable { doTest(); }
   public void testSwitchEnumConstant() { doTest(); }
   public void testEnumConstantNotNull() throws Throwable { doTest(); }
+  public void testCompareToEnumConstant() throws Throwable { doTest(); }
   public void testEqualsConstant() throws Throwable { doTest(); }
   public void testDontSaveTypeValue() { doTest(); }
   public void testFinalLoopVariableInstanceof() throws Throwable { doTest(); }