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//! Keywords for interpreting items and rules for validating them.
use crate::parse::keyword::Keyword;
use crate::parse::tokenize::Item;
use crate::{NetdocErrorKind as EK, Result};
/// May an Item take an object?
#[derive(Copy, Clone)]
enum ObjKind {
/// No object is allowed.
NoObj,
/// An object is required.
RequireObj,
/// An object is optional.
ObjOk,
}
/// A set of restrictions to place on Items for a single keyword.
///
/// These are built by the TokenFmtBuilder API.
#[derive(Clone)]
pub(crate) struct TokenFmt<T: Keyword> {
/// Which keyword is being restricted?
kwd: T,
/// If present, a lower bound on how many arguments may be present.
min_args: Option<usize>,
/// If present, an upper bound on how many arguments may be present.
max_args: Option<usize>,
/// If true, then at least one of this Item must appear.
required: bool,
/// If false, then no more than one this Item may appear.
may_repeat: bool,
/// May this Item have an object? Must it?
obj: ObjKind,
impl<T: Keyword> TokenFmt<T> {
/// Return the keyword that this rule restricts.
pub(crate) fn kwd(&self) -> T {
self.kwd
/// Check whether a single Item matches this TokenFmt rule, with respect
/// to its number of arguments.
fn item_matches_args(&self, item: &Item<'_, T>) -> Result<()> {
let n_args = item.n_args();
if let Some(max) = self.max_args {
if n_args > max {
return Err(EK::TooManyArguments
.with_msg(self.kwd.to_str())
.at_pos(item.pos()));
if let Some(min) = self.min_args {
if n_args < min {
return Err(EK::TooFewArguments
Ok(())
/// Check whether a single Item matches a TokenFmt rule, with respect
/// to its object's presence and type.
fn item_matches_obj(&self, item: &Item<'_, T>) -> Result<()> {
match (&self.obj, item.has_obj()) {
(ObjKind::NoObj, true) => Err(EK::UnexpectedObject
.at_pos(item.pos())),
(ObjKind::RequireObj, false) => Err(EK::MissingObject
(_, _) => Ok(()),
/// Check whether a single item has the right number of arguments
/// and object.
pub(crate) fn check_item(&self, item: &Item<'_, T>) -> Result<()> {
self.item_matches_args(item)?;
self.item_matches_obj(item)
/// Check whether this kind of item may appear this many times.
pub(crate) fn check_multiplicity(&self, items: &[Item<'_, T>]) -> Result<()> {
match items.len() {
0 => {
if self.required {
return Err(EK::MissingToken.with_msg(self.kwd.to_str()));
1 => (),
_ => {
if !self.may_repeat {
return Err(EK::DuplicateToken
.at_pos(items[1].pos()));
/// Represents a TokenFmt under construction.
/// To construct a rule, create this type with Keyword::rule(), then
/// call method on it to set its fields, and then pass it to
/// SectionRules::add().
/// # Example
/// ```ignore
/// // There must be exactly one "ROUTER" entry, with 5 or more arguments.
/// section_rules.add(D.rule().required().args(5..));
/// ```
/// TODO: I'd rather have this be pub(crate), but I haven't figured out
/// how to make that work. There are complicated cascading side-effects.
pub struct TokenFmtBuilder<T: Keyword>(TokenFmt<T>);
impl<T: Keyword> From<TokenFmtBuilder<T>> for TokenFmt<T> {
fn from(builder: TokenFmtBuilder<T>) -> Self {
builder.0
impl<T: Keyword> TokenFmtBuilder<T> {
/// Make a new TokenFmtBuilder with default behavior.
/// (By default, all arguments are allowed, the Item may appear 0
/// or 1 times, and it may not take an object.)
pub(crate) fn new(t: T) -> Self {
Self(TokenFmt {
kwd: t,
min_args: None,
max_args: None,
required: false,
may_repeat: false,
obj: ObjKind::NoObj,
})
/// Indicate that this Item is required.
/// By default, no item is required.
pub(crate) fn required(self) -> Self {
required: true,
..self.0
/// Indicate that this Item may appear more than once.
/// By default, items may not repeat.
pub(crate) fn may_repeat(self) -> Self {
may_repeat: true,
/// Indicate that this Item takes no arguments.
/// By default, items may take any number of arguments.
pub(crate) fn no_args(self) -> Self {
max_args: Some(0),
/// Indicate that this item takes a certain number of arguments.
/// The number of arguments is provided as a range, like `5..`.
pub(crate) fn args<R>(self, r: R) -> Self
where
R: std::ops::RangeBounds<usize>,
{
use std::ops::Bound::*;
let min_args = match r.start_bound() {
Included(x) => Some(*x),
Excluded(x) => Some(*x + 1),
Unbounded => None,
};
let max_args = match r.end_bound() {
Excluded(x) => Some(*x - 1),
min_args,
max_args,
/// Indicate that this token takes an optional object.
/// By default, objects are not allowed.
pub(crate) fn obj_optional(self) -> Self {
obj: ObjKind::ObjOk,
/// Indicate that this token takes an required object.
pub(crate) fn obj_required(self) -> Self {
obj: ObjKind::RequireObj,