Additional test to make sure that PR

eclipse-jdt#4554 does not
inadvertently mask problems (See
eclipse-jdt#4740 (comment))

Author: srikanth-sankaran

org.eclipse.jdt.core.compiler.batch/src/org/eclipse/jdt/internal/compiler/ast/TypeDeclaration.java

@@ -108,6 +108,9 @@ public class TypeDeclaration extends Statement implements ProblemSeverities, Ref
 	// 17 Sealed Type support
 	public TypeReference[] permittedTypes;
 
+	// TEST ONLY: disable one fix here to challenge another related fix (in TypeSystem):
+	public static boolean TESTING_GH_2158 = false;
+
 	static {
 		disallowedComponentNames = new HashSet<>(9);
 		disallowedComponentNames.add("clone"); //$NON-NLS-1$

org.eclipse.jdt.core.compiler.batch/src/org/eclipse/jdt/internal/compiler/lookup/Scope.java

@@ -3738,7 +3738,7 @@ public boolean hasErasedCandidatesCollisions(TypeBinding one, TypeBinding two, M
 				Object value = invocations.get(mec);
 				if (value instanceof TypeBinding[]) {
 					TypeBinding[] invalidInvocations = (TypeBinding[]) value;
-					if (areSignificantlyDifferent(invalidInvocations[0], invalidInvocations[1])) {
+					if (TypeDeclaration.TESTING_GH_2158 || areSignificantlyDifferent(invalidInvocations[0], invalidInvocations[1])) {
 						problemReporter().superinterfacesCollide(invalidInvocations[0].erasure(), typeRef, invalidInvocations[0], invalidInvocations[1]);
 						type.tagBits |= TagBits.HierarchyHasProblems;
 						return true;

org.eclipse.jdt.core.tests.compiler/src/org/eclipse/jdt/core/tests/compiler/regression/NullTypeAnnotationTest.java

@@ -27,6 +27,7 @@
 import junit.framework.Test;
 import org.eclipse.jdt.core.JavaCore;
 import org.eclipse.jdt.core.tests.compiler.regression.AbstractRegressionTest.JavacTestOptions.Excuse;
+import org.eclipse.jdt.internal.compiler.ast.TypeDeclaration;
 import org.eclipse.jdt.internal.compiler.classfmt.ClassFileConstants;
 import org.eclipse.jdt.internal.compiler.impl.CompilerOptions;
 
@@ -19365,6 +19366,14 @@ public class DMessageHandlerRegistryImpl<@NonNull C extends DConnection>
 	runner.customOptions = getCompilerOptions();
 	runner.classLibraries = this.LIBS;
 	runner.runConformTest();
+
+	// challenge other part of the fix:
+	TypeDeclaration.TESTING_GH_2158 = true;
+	try {
+		runner.runConformTest();
+	} finally {
+		TypeDeclaration.TESTING_GH_2158 = false;
+	}
 }
 public void testGH2325() {
 	Runner runner = new Runner();