From 48848a8a7b01e1bbc0f33e9e835801ebb9bbd492 Mon Sep 17 00:00:00 2001
From: Tagir Valeev <Tagir.Valeev@jetbrains.com>
Date: Sat, 3 Mar 2018 15:02:58 +0700
Subject: [PATCH] IDEA-187645 NPE warning is not issued when "null -> null"
 method is called with Nullable argument

---
 .../dataFlow/value/DfaRelationValue.java      | 13 +++++++++--
 .../fixture/ContractWithNullable.java         | 22 ++++++++++++++++++-
 2 files changed, 32 insertions(+), 3 deletions(-)

diff --git a/java/java-analysis-impl/src/com/intellij/codeInspection/dataFlow/value/DfaRelationValue.java b/java/java-analysis-impl/src/com/intellij/codeInspection/dataFlow/value/DfaRelationValue.java
index 09d7f5692f41..24e48ae92fda 100644
--- a/java/java-analysis-impl/src/com/intellij/codeInspection/dataFlow/value/DfaRelationValue.java
+++ b/java/java-analysis-impl/src/com/intellij/codeInspection/dataFlow/value/DfaRelationValue.java
@@ -16,6 +16,7 @@
 
 package com.intellij.codeInspection.dataFlow.value;
 
+import com.intellij.codeInspection.dataFlow.DfaFactType;
 import com.intellij.openapi.util.Trinity;
 import com.intellij.psi.JavaTokenType;
 import com.intellij.psi.tree.IElementType;
@@ -189,14 +190,22 @@ public class DfaRelationValue extends DfaValue {
         return createCanonicalRelation(dfaLeft, relationType, dfaRight);
       }
       if (dfaLeft instanceof DfaFactMapValue && dfaRight instanceof DfaConstValue) {
-        return createCanonicalRelation(DfaUnknownValue.getInstance(), relationType, dfaRight);
+        return createConstBasedRelation((DfaFactMapValue)dfaLeft, relationType, (DfaConstValue)dfaRight);
       }
       else if (dfaRight instanceof DfaFactMapValue && dfaLeft instanceof DfaConstValue) {
-        return createCanonicalRelation(DfaUnknownValue.getInstance(), relationType, dfaLeft);
+        return createConstBasedRelation((DfaFactMapValue)dfaRight, relationType, (DfaConstValue)dfaLeft);
       }
       return null;
     }
 
+    @NotNull
+    private DfaRelationValue createConstBasedRelation(DfaFactMapValue dfaLeft, RelationType relationType, DfaConstValue dfaRight) {
+      if (dfaRight.getValue() == null && Boolean.TRUE.equals(dfaLeft.get(DfaFactType.CAN_BE_NULL))) {
+        return createCanonicalRelation(myFactory.getFactValue(DfaFactType.CAN_BE_NULL, Boolean.TRUE), relationType, dfaRight);
+      }
+      return createCanonicalRelation(DfaUnknownValue.getInstance(), relationType, dfaRight);
+    }
+
     @NotNull
     private DfaRelationValue createCanonicalRelation(@NotNull final DfaValue dfaLeft,
                                                      @NotNull RelationType relationType,
diff --git a/java/java-tests/testData/inspection/dataFlow/fixture/ContractWithNullable.java b/java/java-tests/testData/inspection/dataFlow/fixture/ContractWithNullable.java
index 99831720bfe7..5c21de8ec170 100644
--- a/java/java-tests/testData/inspection/dataFlow/fixture/ContractWithNullable.java
+++ b/java/java-tests/testData/inspection/dataFlow/fixture/ContractWithNullable.java
@@ -2,6 +2,26 @@ import org.jetbrains.annotations.Contract;
 import org.jetbrains.annotations.NotNull;
 import org.jetbrains.annotations.Nullable;
 
+class Test2 {
+  interface Project {}
+  interface Sdk {}
+  interface Version {}
+
+  @NotNull
+  native static Test2 getInstance(Project project);
+
+  @Nullable
+  native Sdk getProjectSdk();
+
+  @Contract("null -> null")
+  native static Version getVersion(@Nullable Sdk sdk);
+
+  static void test(Project project) {
+    Version version = getVersion(getInstance(project).getProjectSdk());
+    System.out.println(version.<warning descr="Method invocation 'hashCode' may produce 'java.lang.NullPointerException'">hashCode</warning>());
+  }
+}
+
 class Foo {
 
   public void main(@NotNull Object nn) {
@@ -58,4 +78,4 @@ class Test {
   String test() {
     return convert(getName());
   }
-}
\ No newline at end of file
+}