// demangler does.  This is not very general but perhaps it is
	// sufficient.
	const enableIfPrefix = "Ua9enable_ifI"
	var enableIfArgs []AST
	if strings.HasPrefix(st.str, enableIfPrefix) {
		st.advance(len(enableIfPrefix) - 1)
		enableIfArgs = st.templateArgs()
	}

	ft := st.bareFunctionType(hasReturnType(a), explicitObjectParameter)

	var constraint AST