Bug 52064 Content assist in "New Class" Dialog shows interfaces
Content Assist is available for the superclass in M7. However it also lists interfaces. If an interface is selected, the generated class "extends" it instead of "implementing" it.
org.eclipse.jdt.ui/ui/org/eclipse/jdt/ui/wizards/NewTypeWizardPage.java
return status;
				}
				IPath location= resource.getLocation();
				if (location != null && location.toFile().exists()) {
					status.setError(NewWizardMessages.getString("NewTypeWizardPage.error.TypeNameExistsDifferentCase")); 
					return status;
				}
			}
		} else {
			IType type= getEnclosingType();
			if (type != null) {
				IType member= type.getType(typeName);
				if (member.exists()) {
					status.setError(NewWizardMessages.getString("NewTypeWizardPage.error.TypeNameExists")); 
					return status;
				}
			}
		}
		return status;
	}
	
	/**
	 * Hook method that gets called when the superclass name has changed. The method 
	 * validates the superclass name and returns the status of the validation.
	 * <p>
	 * Subclasses may extend this method to perform their own validation.
	 * </p>
	 * 
	 * @return the status of the validation
	 */