src/vs/platform/extensions/common/extensions.ts/ExtensionIdentifier/equals
class ExtensionIdentifier:	public static equals(a: ExtensionIdentifier | string | null | undefined, b: ExtensionIdentifier | string | null | undefined) {
		if (typeof a === 'undefined' || a === null) {
			return (typeof b === 'undefined' || b === null);
		}
		if (typeof b === 'undefined' || b === null) {
			return false;
		}
		if (typeof a === 'string' || typeof b === 'string') {
			// At least one of the arguments is an extension id in string form,
			// so we have to use the string comparison which ignores case.
			let aValue = (typeof a === 'string' ? a : a.value);
			let bValue = (typeof b === 'string' ? b : b.value);
			return strings.equalsIgnoreCase(aValue, bValue);
		}

		// Now we know both arguments are ExtensionIdentifier
		return (a._lower === b._lower);
	}