vendor/pulldown-cmark-0.10.3/src/lib.rs - toolchain/rustc - Git at Google

 // Copyright 2015 Google Inc. All rights reserved.
 //
 // Permission is hereby granted, free of charge, to any person obtaining a copy
 // of this software and associated documentation files (the "Software"), to deal
 // in the Software without restriction, including without limitation the rights
 // to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 // copies of the Software, and to permit persons to whom the Software is
 // furnished to do so, subject to the following conditions:
 //
 // The above copyright notice and this permission notice shall be included in
 // all copies or substantial portions of the Software.
 //
 // THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 // IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 // FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 // AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 // LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 // OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 // THE SOFTWARE.

 //! Pull parser for [CommonMark](https://commonmark.org). This crate provides a [Parser](struct.Parser.html) struct
 //! which is an iterator over [Event](enum.Event.html)s. This iterator can be used
 //! directly, or to output HTML using the [HTML module](html/index.html).
 //!
 //! By default, only CommonMark features are enabled. To use extensions like tables,
 //! footnotes or task lists, enable them by setting the corresponding flags in the
 //! [Options](struct.Options.html) struct.
 //!
 //! # Example
 //! ```rust
 //! use pulldown_cmark::{Parser, Options};
 //!
 //! let markdown_input = "Hello world, this is a ~~complicated~~ *very simple* example.";
 //!
 //! // Set up options and parser. Strikethroughs are not part of the CommonMark standard
 //! // and we therefore must enable it explicitly.
 //! let mut options = Options::empty();
 //! options.insert(Options::ENABLE_STRIKETHROUGH);
 //! let parser = Parser::new_ext(markdown_input, options);
 //!
 //! # #[cfg(feature = "html")] {
 //! // Write to String buffer.
 //! let mut html_output = String::new();
 //! pulldown_cmark::html::push_html(&mut html_output, parser);
 //!
 //! // Check that the output is what we expected.
 //! let expected_html = "<p>Hello world, this is a <del>complicated</del> <em>very simple</em> example.</p>\n";
 //! assert_eq!(expected_html, &html_output);
 //! # }
 //! ```
 //!
 //! Note that consecutive text events can happen due to the manner in which the
 //! parser evaluates the source. A utility `TextMergeStream` exists to improve
 //! the comfort of iterating the events:
 //!
 //! ```rust
 //! use pulldown_cmark::{Event, Parser, TextMergeStream};
 //!
 //! let markdown_input = "Hello world, this is a ~~complicated~~ *very simple* example.";
 //!
 //! let iterator = TextMergeStream::new(Parser::new(markdown_input));
 //!
 //! for event in iterator {
 //!     match event {
 //!         Event::Text(text) => println!("{}", text),
 //!         _ => {}
 //!     }
 //! }
 //! ```
 //!

 // When compiled for the rustc compiler itself we want to make sure that this is
 // an unstable crate.
 #![cfg_attr(rustbuild, feature(staged_api, rustc_private))]
 #![cfg_attr(rustbuild, unstable(feature = "rustc_private", issue = "27812"))]
 // Forbid unsafe code unless the SIMD feature is enabled.
 #![cfg_attr(not(feature = "simd"), forbid(unsafe_code))]
 #![warn(missing_debug_implementations)]

 #[cfg(feature = "serde")]
 use serde::{Deserialize, Serialize};

 #[cfg(feature = "html")]
 pub mod html;

 pub mod utils;

 mod entities;
 mod firstpass;
 mod linklabel;
 mod parse;
 mod puncttable;
 mod scanners;
 mod strings;
 mod tree;

 use std::fmt::Display;

 pub use crate::parse::{
     BrokenLink, BrokenLinkCallback, DefaultBrokenLinkCallback, OffsetIter, Parser, RefDefs,
 };
 pub use crate::strings::{CowStr, InlineStr};
 pub use crate::utils::*;

 /// Codeblock kind.
 #[derive(Clone, Debug, PartialEq)]
 #[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
 pub enum CodeBlockKind<'a> {
     Indented,
     /// The value contained in the tag describes the language of the code, which may be empty.
     #[cfg_attr(feature = "serde", serde(borrow))]
     Fenced(CowStr<'a>),
 }

 impl<'a> CodeBlockKind<'a> {
     pub fn is_indented(&self) -> bool {
         matches!(*self, CodeBlockKind::Indented)
     }

     pub fn is_fenced(&self) -> bool {
         matches!(*self, CodeBlockKind::Fenced(_))
     }
 }

 #[derive(Clone, Copy, Debug, PartialEq, Eq, PartialOrd, Ord, Hash)]
 #[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
 pub enum MetadataBlockKind {
     YamlStyle,
     PlusesStyle,
 }

 /// Tags for elements that can contain other elements.
 #[derive(Clone, Debug, PartialEq)]
 #[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
 pub enum Tag<'a> {
     /// A paragraph of text and other inline elements.
     Paragraph,

     /// A heading, with optional identifier, classes and custom attributes.
     /// The identifier is prefixed with `#` and the last one in the attributes
     /// list is chosen, classes are prefixed with `.` and custom attributes
     /// have no prefix and can optionally have a value (`myattr` or `myattr=myvalue`).
     Heading {
         level: HeadingLevel,
         id: Option<CowStr<'a>>,
         classes: Vec<CowStr<'a>>,
         /// The first item of the tuple is the attr and second one the value.
         attrs: Vec<(CowStr<'a>, Option<CowStr<'a>>)>,
     },

     BlockQuote,
     /// A code block.
     CodeBlock(CodeBlockKind<'a>),

     /// A HTML block.
     HtmlBlock,

     /// A list. If the list is ordered the field indicates the number of the first item.
     /// Contains only list items.
     List(Option<u64>), // TODO: add delim and tight for ast (not needed for html)
     /// A list item.
     Item,
     /// A footnote definition. The value contained is the footnote's label by which it can
     /// be referred to.
     #[cfg_attr(feature = "serde", serde(borrow))]
     FootnoteDefinition(CowStr<'a>),

     /// A table. Contains a vector describing the text-alignment for each of its columns.
     Table(Vec<Alignment>),
     /// A table header. Contains only `TableCell`s. Note that the table body starts immediately
     /// after the closure of the `TableHead` tag. There is no `TableBody` tag.
     TableHead,
     /// A table row. Is used both for header rows as body rows. Contains only `TableCell`s.
     TableRow,
     TableCell,

     // span-level tags
     Emphasis,
     Strong,
     Strikethrough,

     /// A link.
     Link {
         link_type: LinkType,
         dest_url: CowStr<'a>,
         title: CowStr<'a>,
         /// Identifier of reference links, e.g. `world` in the link `[hello][world]`.
         id: CowStr<'a>,
     },

     /// An image. The first field is the link type, the second the destination URL and the third is a title,
     /// the fourth is the link identifier.
     Image {
         link_type: LinkType,
         dest_url: CowStr<'a>,
         title: CowStr<'a>,
         /// Identifier of reference links, e.g. `world` in the link `[hello][world]`.
         id: CowStr<'a>,
     },

     /// A metadata block.
     MetadataBlock(MetadataBlockKind),
 }

 impl<'a> Tag<'a> {
     pub fn to_end(&self) -> TagEnd {
         match self {
             Tag::Paragraph => TagEnd::Paragraph,
             Tag::Heading { level, .. } => TagEnd::Heading(*level),
             Tag::BlockQuote => TagEnd::BlockQuote,
             Tag::CodeBlock(_) => TagEnd::CodeBlock,
             Tag::HtmlBlock => TagEnd::HtmlBlock,
             Tag::List(number) => TagEnd::List(number.is_some()),
             Tag::Item => TagEnd::Item,
             Tag::FootnoteDefinition(_) => TagEnd::FootnoteDefinition,
             Tag::Table(_) => TagEnd::Table,
             Tag::TableHead => TagEnd::TableHead,
             Tag::TableRow => TagEnd::TableRow,
             Tag::TableCell => TagEnd::TableCell,
             Tag::Emphasis => TagEnd::Emphasis,
             Tag::Strong => TagEnd::Strong,
             Tag::Strikethrough => TagEnd::Strikethrough,
             Tag::Link { .. } => TagEnd::Link,
             Tag::Image { .. } => TagEnd::Image,
             Tag::MetadataBlock(kind) => TagEnd::MetadataBlock(*kind),
         }
     }
 }

 /// The end of a `Tag`.
 #[derive(Copy, Clone, Eq, PartialEq, Ord, PartialOrd, Hash, Debug)]
 #[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
 pub enum TagEnd {
     Paragraph,
     Heading(HeadingLevel),

     BlockQuote,
     CodeBlock,

     HtmlBlock,

     /// A list, `true` for ordered lists.
     List(bool),
     Item,
     FootnoteDefinition,

     Table,
     TableHead,
     TableRow,
     TableCell,

     Emphasis,
     Strong,
     Strikethrough,

     Link,
     Image,

     MetadataBlock(MetadataBlockKind),
 }

 impl<'a> From<Tag<'a>> for TagEnd {
     fn from(value: Tag) -> Self {
         value.to_end()
     }
 }

 #[derive(Copy, Clone, Eq, PartialEq, Ord, PartialOrd, Hash, Debug)]
 #[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
 pub enum HeadingLevel {
     H1 = 1,
     H2,
     H3,
     H4,
     H5,
     H6,
 }

 impl Display for HeadingLevel {
     fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
         match self {
             Self::H1 => write!(f, "h1"),
             Self::H2 => write!(f, "h2"),
             Self::H3 => write!(f, "h3"),
             Self::H4 => write!(f, "h4"),
             Self::H5 => write!(f, "h5"),
             Self::H6 => write!(f, "h6"),
         }
     }
 }

 /// Returned when trying to convert a `usize` into a `Heading` but it fails
 /// because the usize isn't a valid heading level
 #[derive(Copy, Clone, Eq, PartialEq, Ord, PartialOrd, Hash, Debug)]
 pub struct InvalidHeadingLevel(usize);

 impl TryFrom<usize> for HeadingLevel {
     type Error = InvalidHeadingLevel;

     fn try_from(value: usize) -> Result<Self, Self::Error> {
         match value {
             1 => Ok(Self::H1),
             2 => Ok(Self::H2),
             3 => Ok(Self::H3),
             4 => Ok(Self::H4),
             5 => Ok(Self::H5),
             6 => Ok(Self::H6),
             _ => Err(InvalidHeadingLevel(value)),
         }
     }
 }

 /// Type specifier for inline links. See [the Tag::Link](enum.Tag.html#variant.Link) for more information.
 #[derive(Clone, Debug, PartialEq, Copy)]
 #[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
 pub enum LinkType {
     /// Inline link like `[foo](bar)`
     Inline,
     /// Reference link like `[foo][bar]`
     Reference,
     /// Reference without destination in the document, but resolved by the broken_link_callback
     ReferenceUnknown,
     /// Collapsed link like `[foo][]`
     Collapsed,
     /// Collapsed link without destination in the document, but resolved by the broken_link_callback
     CollapsedUnknown,
     /// Shortcut link like `[foo]`
     Shortcut,
     /// Shortcut without destination in the document, but resolved by the broken_link_callback
     ShortcutUnknown,
     /// Autolink like `<http://foo.bar/baz>`
     Autolink,
     /// Email address in autolink like `<[email protected]>`
     Email,
 }

 impl LinkType {
     /// Map the link type to an equivalent _Unknown link type.
     fn to_unknown(self) -> Self {
         match self {
             LinkType::Reference => LinkType::ReferenceUnknown,
             LinkType::Collapsed => LinkType::CollapsedUnknown,
             LinkType::Shortcut => LinkType::ShortcutUnknown,
             _ => unreachable!(),
         }
     }
 }

 /// Markdown events that are generated in a preorder traversal of the document
 /// tree, with additional `End` events whenever all of an inner node's children
 /// have been visited.
 #[derive(Clone, Debug, PartialEq)]
 #[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
 pub enum Event<'a> {
     /// Start of a tagged element. Events that are yielded after this event
     /// and before its corresponding `End` event are inside this element.
     /// Start and end events are guaranteed to be balanced.
     #[cfg_attr(feature = "serde", serde(borrow))]
     Start(Tag<'a>),
     /// End of a tagged element.
     End(TagEnd),
     /// A text node.
     #[cfg_attr(feature = "serde", serde(borrow))]
     Text(CowStr<'a>),
     /// An inline code node.
     #[cfg_attr(feature = "serde", serde(borrow))]
     Code(CowStr<'a>),
     /// An HTML node.
     #[cfg_attr(feature = "serde", serde(borrow))]
     Html(CowStr<'a>),
     /// An inline HTML node.
     #[cfg_attr(feature = "serde", serde(borrow))]
     InlineHtml(CowStr<'a>),
     /// A reference to a footnote with given label, which may or may not be defined
     /// by an event with a `Tag::FootnoteDefinition` tag. Definitions and references to them may
     /// occur in any order.
     #[cfg_attr(feature = "serde", serde(borrow))]
     FootnoteReference(CowStr<'a>),
     /// A soft line break.
     SoftBreak,
     /// A hard line break.
     HardBreak,
     /// A horizontal ruler.
     Rule,
     /// A task list marker, rendered as a checkbox in HTML. Contains a true when it is checked.
     TaskListMarker(bool),
 }

 /// Table column text alignment.
 #[derive(Copy, Clone, Debug, PartialEq)]
 #[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]

 pub enum Alignment {
     /// Default text alignment.
     None,
     Left,
     Center,
     Right,
 }

 bitflags::bitflags! {
     /// Option struct containing flags for enabling extra features
     /// that are not part of the CommonMark spec.
     #[derive(Debug, Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash)]
     pub struct Options: u32 {
         const ENABLE_TABLES = 1 << 1;
         /// GitHub-compatible footnote syntax.
         ///
         /// Footnotes are referenced with the syntax `[^IDENT]`,
         /// and defined with an identifier followed by a colon at top level.
         ///
         /// ---
         ///
         /// ```markdown
         /// Footnote referenced [^1].
         ///
         /// [^1]: footnote defined
         /// ```
         ///
         /// Footnote referenced [^1].
         ///
         /// [^1]: footnote defined
         const ENABLE_FOOTNOTES = 1 << 2;
         const ENABLE_STRIKETHROUGH = 1 << 3;
         const ENABLE_TASKLISTS = 1 << 4;
         const ENABLE_SMART_PUNCTUATION = 1 << 5;
         /// Extension to allow headings to have ID and classes.
         ///
         /// `# text { #id .class1 .class2 myattr other_attr=myvalue }`
         /// is interpreted as a level 1 heading
         /// with the content `text`, ID `id`, classes `class1` and `class2` and
         /// custom attributes `myattr` (without value) and
         /// `other_attr` with value `myvalue`.
         /// Note that ID, classes, and custom attributes should be space-separated.
         const ENABLE_HEADING_ATTRIBUTES = 1 << 6;
         /// Metadata blocks in YAML style, i.e.:
         /// - starting with a `---` line
         /// - ending with a `---` or `...` line
         const ENABLE_YAML_STYLE_METADATA_BLOCKS = 1 << 7;
         /// Metadata blocks delimited by:
         /// - `+++` line at start
         /// - `+++` line at end
         const ENABLE_PLUSES_DELIMITED_METADATA_BLOCKS = 1 << 8;
         /// Older footnote syntax. This flag implies `ENABLE_FOOTNOTES`, changing it to use an
         /// older syntax instead of the new, default, GitHub-compatible syntax.
         ///
         /// New syntax is different from the old syntax regarding
         /// indentation, nesting, and footnote references with no definition:
         ///
         /// ```markdown
         /// [^1]: In new syntax, this is two footnote definitions.
         /// [^2]: In old syntax, this is a single footnote definition with two lines.
         ///
         /// [^3]:
         ///
         ///     In new syntax, this is a footnote with two paragraphs.
         ///
         ///     In old syntax, this is a footnote followed by a code block.
         ///
         /// In new syntax, this undefined footnote definition renders as
         /// literal text [^4]. In old syntax, it creates a dangling link.
         /// ```
         const ENABLE_OLD_FOOTNOTES = (1 << 9) | (1 << 2);
     }
 }

 impl Options {
     pub(crate) fn has_gfm_footnotes(&self) -> bool {
         self.contains(Options::ENABLE_FOOTNOTES) && !self.contains(Options::ENABLE_OLD_FOOTNOTES)
     }
 }
	// Copyright 2015 Google Inc. All rights reserved.
	//
	// Permission is hereby granted, free of charge, to any person obtaining a copy
	// of this software and associated documentation files (the "Software"), to deal
	// in the Software without restriction, including without limitation the rights
	// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
	// copies of the Software, and to permit persons to whom the Software is
	// furnished to do so, subject to the following conditions:
	//
	// The above copyright notice and this permission notice shall be included in
	// all copies or substantial portions of the Software.
	//
	// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
	// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
	// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
	// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
	// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
	// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
	// THE SOFTWARE.

	//! Pull parser for [CommonMark](https://commonmark.org). This crate provides a [Parser](struct.Parser.html) struct
	//! which is an iterator over [Event](enum.Event.html)s. This iterator can be used
	//! directly, or to output HTML using the [HTML module](html/index.html).
	//!
	//! By default, only CommonMark features are enabled. To use extensions like tables,
	//! footnotes or task lists, enable them by setting the corresponding flags in the
	//! [Options](struct.Options.html) struct.
	//!
	//! # Example
	//! ```rust
	//! use pulldown_cmark::{Parser, Options};
	//!
	//! let markdown_input = "Hello world, this is a ~~complicated~~ very simple example.";
	//!
	//! // Set up options and parser. Strikethroughs are not part of the CommonMark standard
	//! // and we therefore must enable it explicitly.
	//! let mut options = Options::empty();
	//! options.insert(Options::ENABLE_STRIKETHROUGH);
	//! let parser = Parser::new_ext(markdown_input, options);
	//!
	//! # #[cfg(feature = "html")] {
	//! // Write to String buffer.
	//! let mut html_output = String::new();
	//! pulldown_cmark::html::push_html(&mut html_output, parser);
	//!
	//! // Check that the output is what we expected.
	//! let expected_html = "<p>Hello world, this is a <del>complicated</del> <em>very simple</em> example.</p>\n";
	//! assert_eq!(expected_html, &html_output);
	//! # }
	//! ```
	//!
	//! Note that consecutive text events can happen due to the manner in which the
	//! parser evaluates the source. A utility `TextMergeStream` exists to improve
	//! the comfort of iterating the events:
	//!
	//! ```rust
	//! use pulldown_cmark::{Event, Parser, TextMergeStream};
	//!
	//! let markdown_input = "Hello world, this is a ~~complicated~~ very simple example.";
	//!
	//! let iterator = TextMergeStream::new(Parser::new(markdown_input));
	//!
	//! for event in iterator {
	//! match event {
	//! Event::Text(text) => println!("{}", text),
	//! _ => {}
	//! }
	//! }
	//! ```
	//!

	// When compiled for the rustc compiler itself we want to make sure that this is
	// an unstable crate.
	#![cfg_attr(rustbuild, feature(staged_api, rustc_private))]
	#![cfg_attr(rustbuild, unstable(feature = "rustc_private", issue = "27812"))]
	// Forbid unsafe code unless the SIMD feature is enabled.
	#![cfg_attr(not(feature = "simd"), forbid(unsafe_code))]
	#![warn(missing_debug_implementations)]

	#[cfg(feature = "serde")]
	use serde::{Deserialize, Serialize};

	#[cfg(feature = "html")]
	pub mod html;

	pub mod utils;

	mod entities;
	mod firstpass;
	mod linklabel;
	mod parse;
	mod puncttable;
	mod scanners;
	mod strings;
	mod tree;

	use std::fmt::Display;

	pub use crate::parse::{
	BrokenLink, BrokenLinkCallback, DefaultBrokenLinkCallback, OffsetIter, Parser, RefDefs,
	};
	pub use crate::strings::{CowStr, InlineStr};
	pub use crate::utils::*;

	/// Codeblock kind.
	#[derive(Clone, Debug, PartialEq)]
	#[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
	pub enum CodeBlockKind<'a> {
	Indented,
	/// The value contained in the tag describes the language of the code, which may be empty.
	#[cfg_attr(feature = "serde", serde(borrow))]
	Fenced(CowStr<'a>),
	}

	impl<'a> CodeBlockKind<'a> {
	pub fn is_indented(&self) -> bool {
	matches!(*self, CodeBlockKind::Indented)
	}

	pub fn is_fenced(&self) -> bool {
	matches!(*self, CodeBlockKind::Fenced(_))
	}
	}

	#[derive(Clone, Copy, Debug, PartialEq, Eq, PartialOrd, Ord, Hash)]
	#[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
	pub enum MetadataBlockKind {
	YamlStyle,
	PlusesStyle,
	}

	/// Tags for elements that can contain other elements.
	#[derive(Clone, Debug, PartialEq)]
	#[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
	pub enum Tag<'a> {
	/// A paragraph of text and other inline elements.
	Paragraph,

	/// A heading, with optional identifier, classes and custom attributes.
	/// The identifier is prefixed with `#` and the last one in the attributes
	/// list is chosen, classes are prefixed with `.` and custom attributes
	/// have no prefix and can optionally have a value (`myattr` or `myattr=myvalue`).
	Heading {
	level: HeadingLevel,
	id: Option<CowStr<'a>>,
	classes: Vec<CowStr<'a>>,
	/// The first item of the tuple is the attr and second one the value.
	attrs: Vec<(CowStr<'a>, Option<CowStr<'a>>)>,
	},

	BlockQuote,
	/// A code block.
	CodeBlock(CodeBlockKind<'a>),

	/// A HTML block.
	HtmlBlock,

	/// A list. If the list is ordered the field indicates the number of the first item.
	/// Contains only list items.
	List(Option<u64>), // TODO: add delim and tight for ast (not needed for html)
	/// A list item.
	Item,
	/// A footnote definition. The value contained is the footnote's label by which it can
	/// be referred to.
	#[cfg_attr(feature = "serde", serde(borrow))]
	FootnoteDefinition(CowStr<'a>),

	/// A table. Contains a vector describing the text-alignment for each of its columns.
	Table(Vec<Alignment>),
	/// A table header. Contains only `TableCell`s. Note that the table body starts immediately
	/// after the closure of the `TableHead` tag. There is no `TableBody` tag.
	TableHead,
	/// A table row. Is used both for header rows as body rows. Contains only `TableCell`s.
	TableRow,
	TableCell,

	// span-level tags
	Emphasis,
	Strong,
	Strikethrough,

	/// A link.
	Link {
	link_type: LinkType,
	dest_url: CowStr<'a>,
	title: CowStr<'a>,
	/// Identifier of reference links, e.g. `world` in the link `[hello][world]`.
	id: CowStr<'a>,
	},

	/// An image. The first field is the link type, the second the destination URL and the third is a title,
	/// the fourth is the link identifier.
	Image {
	link_type: LinkType,
	dest_url: CowStr<'a>,
	title: CowStr<'a>,
	/// Identifier of reference links, e.g. `world` in the link `[hello][world]`.
	id: CowStr<'a>,
	},

	/// A metadata block.
	MetadataBlock(MetadataBlockKind),
	}

	impl<'a> Tag<'a> {
	pub fn to_end(&self) -> TagEnd {
	match self {
	Tag::Paragraph => TagEnd::Paragraph,
	Tag::Heading { level, .. } => TagEnd::Heading(*level),
	Tag::BlockQuote => TagEnd::BlockQuote,
	Tag::CodeBlock(_) => TagEnd::CodeBlock,
	Tag::HtmlBlock => TagEnd::HtmlBlock,
	Tag::List(number) => TagEnd::List(number.is_some()),
	Tag::Item => TagEnd::Item,
	Tag::FootnoteDefinition(_) => TagEnd::FootnoteDefinition,
	Tag::Table(_) => TagEnd::Table,
	Tag::TableHead => TagEnd::TableHead,
	Tag::TableRow => TagEnd::TableRow,
	Tag::TableCell => TagEnd::TableCell,
	Tag::Emphasis => TagEnd::Emphasis,
	Tag::Strong => TagEnd::Strong,
	Tag::Strikethrough => TagEnd::Strikethrough,
	Tag::Link { .. } => TagEnd::Link,
	Tag::Image { .. } => TagEnd::Image,
	Tag::MetadataBlock(kind) => TagEnd::MetadataBlock(*kind),
	}
	}
	}

	/// The end of a `Tag`.
	#[derive(Copy, Clone, Eq, PartialEq, Ord, PartialOrd, Hash, Debug)]
	#[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
	pub enum TagEnd {
	Paragraph,
	Heading(HeadingLevel),

	BlockQuote,
	CodeBlock,

	HtmlBlock,

	/// A list, `true` for ordered lists.
	List(bool),
	Item,
	FootnoteDefinition,

	Table,
	TableHead,
	TableRow,
	TableCell,

	Emphasis,
	Strong,
	Strikethrough,

	Link,
	Image,

	MetadataBlock(MetadataBlockKind),
	}

	impl<'a> From<Tag<'a>> for TagEnd {
	fn from(value: Tag) -> Self {
	value.to_end()
	}
	}

	#[derive(Copy, Clone, Eq, PartialEq, Ord, PartialOrd, Hash, Debug)]
	#[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
	pub enum HeadingLevel {
	H1 = 1,
	H2,
	H3,
	H4,
	H5,
	H6,
	}

	impl Display for HeadingLevel {
	fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
	match self {
	Self::H1 => write!(f, "h1"),
	Self::H2 => write!(f, "h2"),
	Self::H3 => write!(f, "h3"),
	Self::H4 => write!(f, "h4"),
	Self::H5 => write!(f, "h5"),
	Self::H6 => write!(f, "h6"),
	}
	}
	}

	/// Returned when trying to convert a `usize` into a `Heading` but it fails
	/// because the usize isn't a valid heading level
	#[derive(Copy, Clone, Eq, PartialEq, Ord, PartialOrd, Hash, Debug)]
	pub struct InvalidHeadingLevel(usize);

	impl TryFrom<usize> for HeadingLevel {
	type Error = InvalidHeadingLevel;

	fn try_from(value: usize) -> Result<Self, Self::Error> {
	match value {
	1 => Ok(Self::H1),
	2 => Ok(Self::H2),
	3 => Ok(Self::H3),
	4 => Ok(Self::H4),
	5 => Ok(Self::H5),
	6 => Ok(Self::H6),
	_ => Err(InvalidHeadingLevel(value)),
	}
	}
	}

	/// Type specifier for inline links. See [the Tag::Link](enum.Tag.html#variant.Link) for more information.
	#[derive(Clone, Debug, PartialEq, Copy)]
	#[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
	pub enum LinkType {
	/// Inline link like `[foo](bar)`
	Inline,
	/// Reference link like `[foo][bar]`
	Reference,
	/// Reference without destination in the document, but resolved by the broken_link_callback
	ReferenceUnknown,
	/// Collapsed link like `[foo][]`
	Collapsed,
	/// Collapsed link without destination in the document, but resolved by the broken_link_callback
	CollapsedUnknown,
	/// Shortcut link like `[foo]`
	Shortcut,
	/// Shortcut without destination in the document, but resolved by the broken_link_callback
	ShortcutUnknown,
	/// Autolink like `<http://foo.bar/baz>`
	Autolink,
	/// Email address in autolink like `<[email protected]>`
	Email,
	}

	impl LinkType {
	/// Map the link type to an equivalent _Unknown link type.
	fn to_unknown(self) -> Self {
	match self {
	LinkType::Reference => LinkType::ReferenceUnknown,
	LinkType::Collapsed => LinkType::CollapsedUnknown,
	LinkType::Shortcut => LinkType::ShortcutUnknown,
	_ => unreachable!(),
	}
	}
	}

	/// Markdown events that are generated in a preorder traversal of the document
	/// tree, with additional `End` events whenever all of an inner node's children
	/// have been visited.
	#[derive(Clone, Debug, PartialEq)]
	#[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
	pub enum Event<'a> {
	/// Start of a tagged element. Events that are yielded after this event
	/// and before its corresponding `End` event are inside this element.
	/// Start and end events are guaranteed to be balanced.
	#[cfg_attr(feature = "serde", serde(borrow))]
	Start(Tag<'a>),
	/// End of a tagged element.
	End(TagEnd),
	/// A text node.
	#[cfg_attr(feature = "serde", serde(borrow))]
	Text(CowStr<'a>),
	/// An inline code node.
	#[cfg_attr(feature = "serde", serde(borrow))]
	Code(CowStr<'a>),
	/// An HTML node.
	#[cfg_attr(feature = "serde", serde(borrow))]
	Html(CowStr<'a>),
	/// An inline HTML node.
	#[cfg_attr(feature = "serde", serde(borrow))]
	InlineHtml(CowStr<'a>),
	/// A reference to a footnote with given label, which may or may not be defined
	/// by an event with a `Tag::FootnoteDefinition` tag. Definitions and references to them may
	/// occur in any order.
	#[cfg_attr(feature = "serde", serde(borrow))]
	FootnoteReference(CowStr<'a>),
	/// A soft line break.
	SoftBreak,
	/// A hard line break.
	HardBreak,
	/// A horizontal ruler.
	Rule,
	/// A task list marker, rendered as a checkbox in HTML. Contains a true when it is checked.
	TaskListMarker(bool),
	}

	/// Table column text alignment.
	#[derive(Copy, Clone, Debug, PartialEq)]
	#[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]

	pub enum Alignment {
	/// Default text alignment.
	None,
	Left,
	Center,
	Right,
	}

	bitflags::bitflags! {
	/// Option struct containing flags for enabling extra features
	/// that are not part of the CommonMark spec.
	#[derive(Debug, Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash)]
	pub struct Options: u32 {
	const ENABLE_TABLES = 1 << 1;
	/// GitHub-compatible footnote syntax.
	///
	/// Footnotes are referenced with the syntax `[^IDENT]`,
	/// and defined with an identifier followed by a colon at top level.
	///
	/// ---
	///
	/// ```markdown
	/// Footnote referenced [^1].
	///
	/// [^1]: footnote defined
	/// ```
	///
	/// Footnote referenced [^1].
	///
	/// [^1]: footnote defined
	const ENABLE_FOOTNOTES = 1 << 2;
	const ENABLE_STRIKETHROUGH = 1 << 3;
	const ENABLE_TASKLISTS = 1 << 4;
	const ENABLE_SMART_PUNCTUATION = 1 << 5;
	/// Extension to allow headings to have ID and classes.
	///
	/// `# text { #id .class1 .class2 myattr other_attr=myvalue }`
	/// is interpreted as a level 1 heading
	/// with the content `text`, ID `id`, classes `class1` and `class2` and
	/// custom attributes `myattr` (without value) and
	/// `other_attr` with value `myvalue`.
	/// Note that ID, classes, and custom attributes should be space-separated.
	const ENABLE_HEADING_ATTRIBUTES = 1 << 6;
	/// Metadata blocks in YAML style, i.e.:
	/// - starting with a `---` line
	/// - ending with a `---` or `...` line
	const ENABLE_YAML_STYLE_METADATA_BLOCKS = 1 << 7;
	/// Metadata blocks delimited by:
	/// - `+++` line at start
	/// - `+++` line at end
	const ENABLE_PLUSES_DELIMITED_METADATA_BLOCKS = 1 << 8;
	/// Older footnote syntax. This flag implies `ENABLE_FOOTNOTES`, changing it to use an
	/// older syntax instead of the new, default, GitHub-compatible syntax.
	///
	/// New syntax is different from the old syntax regarding
	/// indentation, nesting, and footnote references with no definition:
	///
	/// ```markdown
	/// [^1]: In new syntax, this is two footnote definitions.
	/// [^2]: In old syntax, this is a single footnote definition with two lines.
	///
	/// [^3]:
	///
	/// In new syntax, this is a footnote with two paragraphs.
	///
	/// In old syntax, this is a footnote followed by a code block.
	///
	/// In new syntax, this undefined footnote definition renders as
	/// literal text [^4]. In old syntax, it creates a dangling link.
	/// ```
	const ENABLE_OLD_FOOTNOTES = (1 << 9) \| (1 << 2);
	}
	}

	impl Options {
	pub(crate) fn has_gfm_footnotes(&self) -> bool {
	self.contains(Options::ENABLE_FOOTNOTES) && !self.contains(Options::ENABLE_OLD_FOOTNOTES)
	}
	}