for i, arg := range args {
		argMap[macro.args[i]] = arg
	}
	return argMap
}

// collectArgument returns the actual tokens for a single argument of a macro.
// It also returns the token that terminated the argument, which will always
// be either ',' or ')'. The starting '(' has been scanned.
func (in *Input) collectArgument(macro *Macro) ([]Token, ScanToken) {
	nesting := 0
	var tokens []Token
	for {