From d0d9cf8e6fdf2ca616f82ed8a7bb8c2fe6c4d044 Mon Sep 17 00:00:00 2001
From: Tagir Valeev <Tagir.Valeev@jetbrains.com>
Date: Mon, 4 Jun 2018 11:24:57 +0700
Subject: [PATCH] Mark code like `if(x > Double.NaN)` as "always false"

Fixes part of IDEA-193102 x > Double.NaN comparison should be highlighted as always false
---
 .../codeInspection/dataFlow/DfaMemoryStateImpl.java       | 5 +----
 .../testData/inspection/dataFlow/fixture/DoubleNaN.java   | 8 ++++++++
 2 files changed, 9 insertions(+), 4 deletions(-)

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 b4ecf08294b0..1510e585fdc5 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
@@ -441,10 +441,7 @@ public class DfaMemoryStateImpl implements DfaMemoryState {
 
 
   private boolean isEffectivelyNaN(@NotNull DfaValue dfaValue) {
-    for (DfaValue eqClass : getEquivalentValues(dfaValue)) {
-      if (isNaN(eqClass)) return true;
-    }
-    return false;
+    return isNaN(dfaValue) || getEquivalentValues(dfaValue).stream().anyMatch(DfaMemoryStateImpl::isNaN);
   }
 
   List<EqClass> getEqClasses() {
diff --git a/java/java-tests/testData/inspection/dataFlow/fixture/DoubleNaN.java b/java/java-tests/testData/inspection/dataFlow/fixture/DoubleNaN.java
index f363d23a257f..50968776eeb6 100644
--- a/java/java-tests/testData/inspection/dataFlow/fixture/DoubleNaN.java
+++ b/java/java-tests/testData/inspection/dataFlow/fixture/DoubleNaN.java
@@ -1,4 +1,12 @@
 public class DoubleNaN {
+  void testNanCmp(double x) {
+    if (<warning descr="Condition 'x > Double.NaN' is always 'false'">x > Double.NaN</warning>) {
+      return;
+    }
+    boolean cmp = x > Double.NaN; // this is always false, a warning is expected
+    System.out.println(x > Double.NaN); // this is always false, a warning is expected
+  }
+
   void test() {
     double x = Double.NaN;
     double y = Double.NaN;