Bug 376263: Bogus "Potential null pointer access" warning

2 files changed, 46 insertions, 2 deletions

diff --git a/org.eclipse.jdt.core.tests.compiler/src/org/eclipse/jdt/core/tests/compiler/regression/NullReferenceTest.java b/org.eclipse.jdt.core.tests.compiler/src/org/eclipse/jdt/core/tests/compiler/regression/NullReferenceTest.java
index 077a4468cd..c67196f8e5 100644
--- a/org.eclipse.jdt.core.tests.compiler/src/org/eclipse/jdt/core/tests/compiler/regression/NullReferenceTest.java
+++ b/org.eclipse.jdt.core.tests.compiler/src/org/eclipse/jdt/core/tests/compiler/regression/NullReferenceTest.java
@@ -24,6 +24,7 @@
  * 							bug 367879 - Incorrect "Potential null pointer access" warning on statement after try-with-resources within try-finally
  * 							bug 383690 - [compiler] location of error re uninitialized final field should be aligned
  *							bug 345305 - [compiler][null] Compiler misidentifies a case of "variable can only be null"
+ *							bug 376263 - Bogus "Potential null pointer access" warning
  *******************************************************************************/
 package org.eclipse.jdt.core.tests.compiler.regression;
 
@@ -32,6 +33,7 @@ import java.util.Map;
 
 import junit.framework.Test;
 
+import org.eclipse.jdt.core.JavaCore;
 import org.eclipse.jdt.core.ToolFactory;
 import org.eclipse.jdt.core.tests.util.Util;
 import org.eclipse.jdt.core.util.ClassFileBytesDisassembler;
@@ -53,6 +55,7 @@ public NullReferenceTest(String name) {
 static {
 //		TESTS_NAMES = new String[] { "testBug345305_14" };
 //		TESTS_NAMES = new String[] { "test0515_try_finally" };
+//		TESTS_NAMES = new String[] { "testBug376263" };
 //		TESTS_NUMBERS = new int[] { 561 };
 //		TESTS_RANGE = new int[] { 1, 2049 };
 }
@@ -15623,6 +15626,41 @@ public void testBug360328d() {
 		"",/* expected error */
 	    JavacTestOptions.Excuse.EclipseWarningConfiguredAsError);
 }
+public void testBug376263() {
+	Map customOptions = getCompilerOptions();
+	customOptions.put(JavaCore.COMPILER_PB_POTENTIAL_NULL_REFERENCE, JavaCore.ERROR);
+	runConformTest(
+		new String[] {
+			"Test.java",
+			"public class Test {\n" + 
+			"    private int x;\n" + 
+			"\n" + 
+			"    static void test(Test[] array) {\n" + 
+			"        Test elem = null;\n" + 
+			"        int i = 0;\n" + 
+			"        while (i < array.length) {\n" + 
+			"            if (i == 0) {\n" + 
+			"                elem = array[0];\n" + 
+			"            }\n" + 
+			"            if (elem != null) {\n" + 
+			"                while (true) {\n" + 
+			"                    if (elem.x >= 0 || i >= array.length) { // should not warn here\n" + 
+			"                        break;\n" + 
+			"                    }\n" + 
+			"                    elem = array[i++];\n" + 
+			"                }\n" + 
+			"            }\n" + 
+			"        }\n" + 
+			"    }\n" + 
+			"}"
+		},
+		"",
+		null/*classLibraries*/,
+		true/*shouldFlush*/,
+		null/*vmArgs*/,
+		customOptions,
+		null/*requestor*/);
+}
 
 // Bug 345305 - [compiler][null] Compiler misidentifies a case of "variable can only be null"
 // simplified: only try-finally involved
diff --git a/org.eclipse.jdt.core/compiler/org/eclipse/jdt/internal/compiler/flow/LoopingFlowContext.java b/org.eclipse.jdt.core/compiler/org/eclipse/jdt/internal/compiler/flow/LoopingFlowContext.java
index 5020e8aea0..5dcf13ac5e 100644
--- a/org.eclipse.jdt.core/compiler/org/eclipse/jdt/internal/compiler/flow/LoopingFlowContext.java
+++ b/org.eclipse.jdt.core/compiler/org/eclipse/jdt/internal/compiler/flow/LoopingFlowContext.java
@@ -15,6 +15,7 @@
  *								bug 365859 - [compiler][null] distinguish warnings based on flow analysis vs. null annotations
  *								bug 385626 - @NonNull fails across loop boundaries
  *								bug 345305 - [compiler][null] Compiler misidentifies a case of "variable can only be null"
+ *								bug 376263 - Bogus "Potential null pointer access" warning
  *******************************************************************************/
 package org.eclipse.jdt.internal.compiler.flow;
 
@@ -148,6 +149,7 @@ public void complainOnDeferredNullChecks(BlockScope scope, FlowInfo callerFlowIn
 			addPotentialNullInfoFrom(this.innerFlowInfos[i]);
 	}
 	this.innerFlowContextsCount = 0;
+	FlowInfo upstreamCopy = this.upstreamNullFlowInfo.copy();
 	UnconditionalFlowInfo flowInfo = this.upstreamNullFlowInfo.
 		addPotentialNullInfoFrom(callerFlowInfo.unconditionalInitsWithoutSideEffect());
 	if ((this.tagBits & FlowContext.DEFER_NULL_DIAGNOSTIC) != 0) {
@@ -277,8 +279,12 @@ public void complainOnDeferredNullChecks(BlockScope scope, FlowInfo callerFlowIn
 				default:
 					// never happens
 			}
-			this.parent.recordUsingNullReference(scope, local, location,
-					this.nullCheckTypes[i], flowInfo);
+			// https://bugs.eclipse.org/376263: avoid further deferring if the upstream info
+			// already has definite information (which might get lost for deferred checking).
+			if (!(this.nullCheckTypes[i] == MAY_NULL && upstreamCopy.isDefinitelyNonNull(local))) {
+				this.parent.recordUsingNullReference(scope, local, location,
+						this.nullCheckTypes[i], flowInfo);
+			}
 		}
 	}
 	else {