Index: src/org/eclipse/jdt/core/tests/compiler/regression/ProgrammingProblemsTest.java
===================================================================
RCS file: /cvsroot/eclipse/org.eclipse.jdt.core.tests.compiler/src/org/eclipse/jdt/core/tests/compiler/regression/ProgrammingProblemsTest.java,v
--- src/org/eclipse/jdt/core/tests/compiler/regression/ProgrammingProblemsTest.java	17 Jun 2009 06:44:14 -0000	1.16
+++ src/org/eclipse/jdt/core/tests/compiler/regression/ProgrammingProblemsTest.java	16 Jul 2009 06:07:48 -0000
@@ -1529,4 +1529,34 @@ 
 			"Zork cannot be resolved to a type\n" + 
 			"----------\n");
 }
+/**
+ * @see "https://bugs.eclipse.org/bugs/show_bug.cgi?id=281776"
+ * We now tolerate comparison of float and double entities against
+ * themselves as a legitimate idiom for NaN checking. 
+ */
+public void test0040() {
+	this.runNegativeTest(
+		new String[] {
+			"X.java",
+			"public class X {\n" +
+		    "    public static void main(String[] args) {\n" +
+		    "        double var = Double.NaN;\n" +
+		    "            if(var != var) {\n" +
+		    "                  System.out.println(\"NaN\");\n" +
+		    "            }\n" +
+		    "            float varf = 10;\n" +
+		    "            if(varf != varf) {\n" +
+		    "            	System.out.println(\"NaN\");\n" +
+		    "            }\n" +
+		    "   }\n" +
+			"	Zork z;\n" +
+			"}\n"
+			},
+			"----------\n" + 
+			"1. ERROR in X.java (at line 12)\n" + 
+			"	Zork z;\n" + 
+			"	^^^^\n" + 
+			"Zork cannot be resolved to a type\n" + 
+			"----------\n");
+}
 }
Index: compiler/org/eclipse/jdt/internal/compiler/ast/EqualExpression.java
===================================================================
RCS file: /cvsroot/eclipse/org.eclipse.jdt.core/compiler/org/eclipse/jdt/internal/compiler/ast/EqualExpression.java,v
--- compiler/org/eclipse/jdt/internal/compiler/ast/EqualExpression.java	17 Jun 2009 06:44:02 -0000	1.74
+++ compiler/org/eclipse/jdt/internal/compiler/ast/EqualExpression.java	16 Jul 2009 06:08:03 -0000
@@ -812,7 +812,8 @@ 
 			// check whether comparing identical expressions
 			Binding leftDirect = Expression.getDirectBinding(this.left);
 			if (leftDirect != null && leftDirect == Expression.getDirectBinding(this.right)) {
-				scope.problemReporter().comparingIdenticalExpressions(this);
+				if (leftTypeID != TypeIds.T_double && leftTypeID != TypeIds.T_float) // https://bugs.eclipse.org/bugs/show_bug.cgi?id=281776
+					scope.problemReporter().comparingIdenticalExpressions(this);
 			} else if (this.constant != Constant.NotAConstant) {
 				// https://bugs.eclipse.org/bugs/show_bug.cgi?id=276740
 				int operator = (this.bits & OperatorMASK) >> OperatorSHIFT;