Bug 75711 AstProvider should not create AST if requested by SelectionListenerWithASTManager
3.1 M2 If SelectionListenerWithASTManager waits for an AST and the editor closes we should not create an AST for that one but return null instead.
org.eclipse.jdt.ui/ui/org/eclipse/jdt/ui/OverrideIndicatorLabelDecorator.java
if (hierarchy != null) {
			return findInHierarchy(type, hierarchy, method.getElementName(), method.getParameterTypes());
		}
		return 0;
	}
	
	private int findInHierarchyWithAST(CompilationUnit astRoot, IMethod method) throws JavaModelException {
		ASTNode node= NodeFinder.perform(astRoot, method.getNameRange());
		if (node instanceof SimpleName && node.getParent() instanceof MethodDeclaration) {
			IMethodBinding binding= ((MethodDeclaration) node.getParent()).resolveBinding();
			if (binding != null) {
				IMethodBinding defining= Bindings.findMethodDefininition(binding, true);
				if (defining != null) {
					if (JdtFlags.isAbstract(defining)) {
						return JavaElementImageDescriptor.IMPLEMENTS;
					} else {
						return JavaElementImageDescriptor.OVERRIDES;
					}
				}
				return 0;
			}
		}		
		return -1;
	}
	/**
	 * Note: This method is for internal use only. Clients should not call this method.
	 * @param type The declaring type of the method to decorate.
	 * @param hierarchy The type hierarchy of the declaring type.
	 * @param name The name of the method to find.
	 * @param paramTypes The parameter types of the method to find.