src/librustdoc/passes/mod.rs - third_party/rust - Git at Google

 //! Contains information about "passes", used to modify crate information during the documentation
 //! process.

 use rustc_hir::def_id::{DefId, DefIdSet};
 use rustc_middle::middle::privacy::AccessLevels;
 use rustc_span::{InnerSpan, Span, DUMMY_SP};
 use std::mem;
 use std::ops::Range;

 use self::Condition::*;
 use crate::clean::{self, GetDefId, Item};
 use crate::core::DocContext;
 use crate::fold::{DocFolder, StripItem};

 mod collapse_docs;
 pub use self::collapse_docs::COLLAPSE_DOCS;

 mod strip_hidden;
 pub use self::strip_hidden::STRIP_HIDDEN;

 mod strip_private;
 pub use self::strip_private::STRIP_PRIVATE;

 mod strip_priv_imports;
 pub use self::strip_priv_imports::STRIP_PRIV_IMPORTS;

 mod unindent_comments;
 pub use self::unindent_comments::UNINDENT_COMMENTS;

 mod propagate_doc_cfg;
 pub use self::propagate_doc_cfg::PROPAGATE_DOC_CFG;

 mod collect_intra_doc_links;
 pub use self::collect_intra_doc_links::COLLECT_INTRA_DOC_LINKS;

 mod doc_test_lints;
 pub use self::doc_test_lints::CHECK_PRIVATE_ITEMS_DOC_TESTS;

 mod collect_trait_impls;
 pub use self::collect_trait_impls::COLLECT_TRAIT_IMPLS;

 mod check_code_block_syntax;
 pub use self::check_code_block_syntax::CHECK_CODE_BLOCK_SYNTAX;

 mod calculate_doc_coverage;
 pub use self::calculate_doc_coverage::CALCULATE_DOC_COVERAGE;

 /// A single pass over the cleaned documentation.
 ///
 /// Runs in the compiler context, so it has access to types and traits and the like.
 #[derive(Copy, Clone)]
 pub struct Pass {
     pub name: &'static str,
     pub run: fn(clean::Crate, &DocContext<'_>) -> clean::Crate,
     pub description: &'static str,
 }

 /// In a list of passes, a pass that may or may not need to be run depending on options.
 #[derive(Copy, Clone)]
 pub struct ConditionalPass {
     pub pass: Pass,
     pub condition: Condition,
 }

 /// How to decide whether to run a conditional pass.
 #[derive(Copy, Clone)]
 pub enum Condition {
     Always,
     /// When `--document-private-items` is passed.
     WhenDocumentPrivate,
     /// When `--document-private-items` is not passed.
     WhenNotDocumentPrivate,
     /// When `--document-hidden-items` is not passed.
     WhenNotDocumentHidden,
 }

 /// The full list of passes.
 pub const PASSES: &[Pass] = &[
     CHECK_PRIVATE_ITEMS_DOC_TESTS,
     STRIP_HIDDEN,
     UNINDENT_COMMENTS,
     COLLAPSE_DOCS,
     STRIP_PRIVATE,
     STRIP_PRIV_IMPORTS,
     PROPAGATE_DOC_CFG,
     COLLECT_INTRA_DOC_LINKS,
     CHECK_CODE_BLOCK_SYNTAX,
     COLLECT_TRAIT_IMPLS,
     CALCULATE_DOC_COVERAGE,
 ];

 /// The list of passes run by default.
 pub const DEFAULT_PASSES: &[ConditionalPass] = &[
     ConditionalPass::always(COLLECT_TRAIT_IMPLS),
     ConditionalPass::always(COLLAPSE_DOCS),
     ConditionalPass::always(UNINDENT_COMMENTS),
     ConditionalPass::always(CHECK_PRIVATE_ITEMS_DOC_TESTS),
     ConditionalPass::new(STRIP_HIDDEN, WhenNotDocumentHidden),
     ConditionalPass::new(STRIP_PRIVATE, WhenNotDocumentPrivate),
     ConditionalPass::new(STRIP_PRIV_IMPORTS, WhenDocumentPrivate),
     ConditionalPass::always(COLLECT_INTRA_DOC_LINKS),
     ConditionalPass::always(CHECK_CODE_BLOCK_SYNTAX),
     ConditionalPass::always(PROPAGATE_DOC_CFG),
 ];

 /// The list of default passes run when `--doc-coverage` is passed to rustdoc.
 pub const COVERAGE_PASSES: &[ConditionalPass] = &[
     ConditionalPass::always(COLLECT_TRAIT_IMPLS),
     ConditionalPass::new(STRIP_HIDDEN, WhenNotDocumentHidden),
     ConditionalPass::new(STRIP_PRIVATE, WhenNotDocumentPrivate),
     ConditionalPass::always(CALCULATE_DOC_COVERAGE),
 ];

 impl ConditionalPass {
     pub const fn always(pass: Pass) -> Self {
         Self::new(pass, Always)
     }

     pub const fn new(pass: Pass, condition: Condition) -> Self {
         ConditionalPass { pass, condition }
     }
 }

 /// A shorthand way to refer to which set of passes to use, based on the presence of
 /// `--no-defaults` and `--show-coverage`.
 #[derive(Copy, Clone, PartialEq, Eq, Debug)]
 pub enum DefaultPassOption {
     Default,
     Coverage,
     None,
 }

 /// Returns the given default set of passes.
 pub fn defaults(default_set: DefaultPassOption) -> &'static [ConditionalPass] {
     match default_set {
         DefaultPassOption::Default => DEFAULT_PASSES,
         DefaultPassOption::Coverage => COVERAGE_PASSES,
         DefaultPassOption::None => &[],
     }
 }

 /// If the given name matches a known pass, returns its information.
 pub fn find_pass(pass_name: &str) -> Option<Pass> {
     PASSES.iter().find(|p| p.name == pass_name).copied()
 }

 struct Stripper<'a> {
     retained: &'a mut DefIdSet,
     access_levels: &'a AccessLevels<DefId>,
     update_retained: bool,
 }

 impl<'a> DocFolder for Stripper<'a> {
     fn fold_item(&mut self, i: Item) -> Option<Item> {
         match i.inner {
             clean::StrippedItem(..) => {
                 // We need to recurse into stripped modules to strip things
                 // like impl methods but when doing so we must not add any
                 // items to the `retained` set.
                 debug!("Stripper: recursing into stripped {:?} {:?}", i.type_(), i.name);
                 let old = mem::replace(&mut self.update_retained, false);
                 let ret = self.fold_item_recur(i);
                 self.update_retained = old;
                 return ret;
             }
             // These items can all get re-exported
             clean::OpaqueTyItem(..)
             | clean::TypedefItem(..)
             | clean::StaticItem(..)
             | clean::StructItem(..)
             | clean::EnumItem(..)
             | clean::TraitItem(..)
             | clean::FunctionItem(..)
             | clean::VariantItem(..)
             | clean::MethodItem(..)
             | clean::ForeignFunctionItem(..)
             | clean::ForeignStaticItem(..)
             | clean::ConstantItem(..)
             | clean::UnionItem(..)
             | clean::AssocConstItem(..)
             | clean::TraitAliasItem(..)
             | clean::ForeignTypeItem => {
                 if i.def_id.is_local() {
                     if !self.access_levels.is_exported(i.def_id) {
                         debug!("Stripper: stripping {:?} {:?}", i.type_(), i.name);
                         return None;
                     }
                 }
             }

             clean::StructFieldItem(..) => {
                 if i.visibility != clean::Public {
                     return StripItem(i).strip();
                 }
             }

             clean::ModuleItem(..) => {
                 if i.def_id.is_local() && i.visibility != clean::Public {
                     debug!("Stripper: stripping module {:?}", i.name);
                     let old = mem::replace(&mut self.update_retained, false);
                     let ret = StripItem(self.fold_item_recur(i).unwrap()).strip();
                     self.update_retained = old;
                     return ret;
                 }
             }

             // handled in the `strip-priv-imports` pass
             clean::ExternCrateItem(..) | clean::ImportItem(..) => {}

             clean::ImplItem(..) => {}

             // tymethods/macros have no control over privacy
             clean::MacroItem(..) | clean::TyMethodItem(..) => {}

             // Proc-macros are always public
             clean::ProcMacroItem(..) => {}

             // Primitives are never stripped
             clean::PrimitiveItem(..) => {}

             // Associated types are never stripped
             clean::AssocTypeItem(..) => {}

             // Keywords are never stripped
             clean::KeywordItem(..) => {}
         }

         let fastreturn = match i.inner {
             // nothing left to do for traits (don't want to filter their
             // methods out, visibility controlled by the trait)
             clean::TraitItem(..) => true,

             // implementations of traits are always public.
             clean::ImplItem(ref imp) if imp.trait_.is_some() => true,
             // Struct variant fields have inherited visibility
             clean::VariantItem(clean::Variant { kind: clean::VariantKind::Struct(..) }) => true,
             _ => false,
         };

         let i = if fastreturn {
             if self.update_retained {
                 self.retained.insert(i.def_id);
             }
             return Some(i);
         } else {
             self.fold_item_recur(i)
         };

         if let Some(ref i) = i {
             if self.update_retained {
                 self.retained.insert(i.def_id);
             }
         }
         i
     }
 }

 // This stripper discards all impls which reference stripped items
 struct ImplStripper<'a> {
     retained: &'a DefIdSet,
 }

 impl<'a> DocFolder for ImplStripper<'a> {
     fn fold_item(&mut self, i: Item) -> Option<Item> {
         if let clean::ImplItem(ref imp) = i.inner {
             // emptied none trait impls can be stripped
             if imp.trait_.is_none() && imp.items.is_empty() {
                 return None;
             }
             if let Some(did) = imp.for_.def_id() {
                 if did.is_local() && !imp.for_.is_generic() && !self.retained.contains(&did) {
                     debug!("ImplStripper: impl item for stripped type; removing");
                     return None;
                 }
             }
             if let Some(did) = imp.trait_.def_id() {
                 if did.is_local() && !self.retained.contains(&did) {
                     debug!("ImplStripper: impl item for stripped trait; removing");
                     return None;
                 }
             }
             if let Some(generics) = imp.trait_.as_ref().and_then(|t| t.generics()) {
                 for typaram in generics {
                     if let Some(did) = typaram.def_id() {
                         if did.is_local() && !self.retained.contains(&did) {
                             debug!(
                                 "ImplStripper: stripped item in trait's generics; removing impl"
                             );
                             return None;
                         }
                     }
                 }
             }
         }
         self.fold_item_recur(i)
     }
 }

 // This stripper discards all private import statements (`use`, `extern crate`)
 struct ImportStripper;
 impl DocFolder for ImportStripper {
     fn fold_item(&mut self, i: Item) -> Option<Item> {
         match i.inner {
             clean::ExternCrateItem(..) | clean::ImportItem(..) if i.visibility != clean::Public => {
                 None
             }
             _ => self.fold_item_recur(i),
         }
     }
 }

 /// Returns a span encompassing all the given attributes.
 crate fn span_of_attrs(attrs: &clean::Attributes) -> Option<Span> {
     if attrs.doc_strings.is_empty() {
         return None;
     }
     let start = attrs.doc_strings[0].span();
     if start == DUMMY_SP {
         return None;
     }
     let end = attrs.doc_strings.last().expect("no doc strings provided").span();
     Some(start.to(end))
 }

 /// Attempts to match a range of bytes from parsed markdown to a `Span` in the source code.
 ///
 /// This method will return `None` if we cannot construct a span from the source map or if the
 /// attributes are not all sugared doc comments. It's difficult to calculate the correct span in
 /// that case due to escaping and other source features.
 crate fn source_span_for_markdown_range(
     cx: &DocContext<'_>,
     markdown: &str,
     md_range: &Range<usize>,
     attrs: &clean::Attributes,
 ) -> Option<Span> {
     let is_all_sugared_doc = attrs.doc_strings.iter().all(|frag| match frag {
         clean::DocFragment::SugaredDoc(..) => true,
         _ => false,
     });

     if !is_all_sugared_doc {
         return None;
     }

     let snippet = cx.sess().source_map().span_to_snippet(span_of_attrs(attrs)?).ok()?;

     let starting_line = markdown[..md_range.start].matches('\n').count();
     let ending_line = starting_line + markdown[md_range.start..md_range.end].matches('\n').count();

     // We use `split_terminator('\n')` instead of `lines()` when counting bytes so that we treat
     // CRLF and LF line endings the same way.
     let mut src_lines = snippet.split_terminator('\n');
     let md_lines = markdown.split_terminator('\n');

     // The number of bytes from the source span to the markdown span that are not part
     // of the markdown, like comment markers.
     let mut start_bytes = 0;
     let mut end_bytes = 0;

     'outer: for (line_no, md_line) in md_lines.enumerate() {
         loop {
             let source_line = src_lines.next().expect("could not find markdown in source");
             match source_line.find(md_line) {
                 Some(offset) => {
                     if line_no == starting_line {
                         start_bytes += offset;

                         if starting_line == ending_line {
                             break 'outer;
                         }
                     } else if line_no == ending_line {
                         end_bytes += offset;
                         break 'outer;
                     } else if line_no < starting_line {
                         start_bytes += source_line.len() - md_line.len();
                     } else {
                         end_bytes += source_line.len() - md_line.len();
                     }
                     break;
                 }
                 None => {
                     // Since this is a source line that doesn't include a markdown line,
                     // we have to count the newline that we split from earlier.
                     if line_no <= starting_line {
                         start_bytes += source_line.len() + 1;
                     } else {
                         end_bytes += source_line.len() + 1;
                     }
                 }
             }
         }
     }

     Some(span_of_attrs(attrs)?.from_inner(InnerSpan::new(
         md_range.start + start_bytes,
         md_range.end + start_bytes + end_bytes,
     )))
 }
	//! Contains information about "passes", used to modify crate information during the documentation
	//! process.

	use rustc_hir::def_id::{DefId, DefIdSet};
	use rustc_middle::middle::privacy::AccessLevels;
	use rustc_span::{InnerSpan, Span, DUMMY_SP};
	use std::mem;
	use std::ops::Range;

	use self::Condition::*;
	use crate::clean::{self, GetDefId, Item};
	use crate::core::DocContext;
	use crate::fold::{DocFolder, StripItem};

	mod collapse_docs;
	pub use self::collapse_docs::COLLAPSE_DOCS;

	mod strip_hidden;
	pub use self::strip_hidden::STRIP_HIDDEN;

	mod strip_private;
	pub use self::strip_private::STRIP_PRIVATE;

	mod strip_priv_imports;
	pub use self::strip_priv_imports::STRIP_PRIV_IMPORTS;

	mod unindent_comments;
	pub use self::unindent_comments::UNINDENT_COMMENTS;

	mod propagate_doc_cfg;
	pub use self::propagate_doc_cfg::PROPAGATE_DOC_CFG;

	mod collect_intra_doc_links;
	pub use self::collect_intra_doc_links::COLLECT_INTRA_DOC_LINKS;

	mod doc_test_lints;
	pub use self::doc_test_lints::CHECK_PRIVATE_ITEMS_DOC_TESTS;

	mod collect_trait_impls;
	pub use self::collect_trait_impls::COLLECT_TRAIT_IMPLS;

	mod check_code_block_syntax;
	pub use self::check_code_block_syntax::CHECK_CODE_BLOCK_SYNTAX;

	mod calculate_doc_coverage;
	pub use self::calculate_doc_coverage::CALCULATE_DOC_COVERAGE;

	/// A single pass over the cleaned documentation.
	///
	/// Runs in the compiler context, so it has access to types and traits and the like.
	#[derive(Copy, Clone)]
	pub struct Pass {
	pub name: &'static str,
	pub run: fn(clean::Crate, &DocContext<'_>) -> clean::Crate,
	pub description: &'static str,
	}

	/// In a list of passes, a pass that may or may not need to be run depending on options.
	#[derive(Copy, Clone)]
	pub struct ConditionalPass {
	pub pass: Pass,
	pub condition: Condition,
	}

	/// How to decide whether to run a conditional pass.
	#[derive(Copy, Clone)]
	pub enum Condition {
	Always,
	/// When `--document-private-items` is passed.
	WhenDocumentPrivate,
	/// When `--document-private-items` is not passed.
	WhenNotDocumentPrivate,
	/// When `--document-hidden-items` is not passed.
	WhenNotDocumentHidden,
	}

	/// The full list of passes.
	pub const PASSES: &[Pass] = &[
	CHECK_PRIVATE_ITEMS_DOC_TESTS,
	STRIP_HIDDEN,
	UNINDENT_COMMENTS,
	COLLAPSE_DOCS,
	STRIP_PRIVATE,
	STRIP_PRIV_IMPORTS,
	PROPAGATE_DOC_CFG,
	COLLECT_INTRA_DOC_LINKS,
	CHECK_CODE_BLOCK_SYNTAX,
	COLLECT_TRAIT_IMPLS,
	CALCULATE_DOC_COVERAGE,
	];

	/// The list of passes run by default.
	pub const DEFAULT_PASSES: &[ConditionalPass] = &[
	ConditionalPass::always(COLLECT_TRAIT_IMPLS),
	ConditionalPass::always(COLLAPSE_DOCS),
	ConditionalPass::always(UNINDENT_COMMENTS),
	ConditionalPass::always(CHECK_PRIVATE_ITEMS_DOC_TESTS),
	ConditionalPass::new(STRIP_HIDDEN, WhenNotDocumentHidden),
	ConditionalPass::new(STRIP_PRIVATE, WhenNotDocumentPrivate),
	ConditionalPass::new(STRIP_PRIV_IMPORTS, WhenDocumentPrivate),
	ConditionalPass::always(COLLECT_INTRA_DOC_LINKS),
	ConditionalPass::always(CHECK_CODE_BLOCK_SYNTAX),
	ConditionalPass::always(PROPAGATE_DOC_CFG),
	];

	/// The list of default passes run when `--doc-coverage` is passed to rustdoc.
	pub const COVERAGE_PASSES: &[ConditionalPass] = &[
	ConditionalPass::always(COLLECT_TRAIT_IMPLS),
	ConditionalPass::new(STRIP_HIDDEN, WhenNotDocumentHidden),
	ConditionalPass::new(STRIP_PRIVATE, WhenNotDocumentPrivate),
	ConditionalPass::always(CALCULATE_DOC_COVERAGE),
	];

	impl ConditionalPass {
	pub const fn always(pass: Pass) -> Self {
	Self::new(pass, Always)
	}

	pub const fn new(pass: Pass, condition: Condition) -> Self {
	ConditionalPass { pass, condition }
	}
	}

	/// A shorthand way to refer to which set of passes to use, based on the presence of
	/// `--no-defaults` and `--show-coverage`.
	#[derive(Copy, Clone, PartialEq, Eq, Debug)]
	pub enum DefaultPassOption {
	Default,
	Coverage,
	None,
	}

	/// Returns the given default set of passes.
	pub fn defaults(default_set: DefaultPassOption) -> &'static [ConditionalPass] {
	match default_set {
	DefaultPassOption::Default => DEFAULT_PASSES,
	DefaultPassOption::Coverage => COVERAGE_PASSES,
	DefaultPassOption::None => &[],
	}
	}

	/// If the given name matches a known pass, returns its information.
	pub fn find_pass(pass_name: &str) -> Option<Pass> {
	PASSES.iter().find(\|p\| p.name == pass_name).copied()
	}

	struct Stripper<'a> {
	retained: &'a mut DefIdSet,
	access_levels: &'a AccessLevels<DefId>,
	update_retained: bool,
	}

	impl<'a> DocFolder for Stripper<'a> {
	fn fold_item(&mut self, i: Item) -> Option<Item> {
	match i.inner {
	clean::StrippedItem(..) => {
	// We need to recurse into stripped modules to strip things
	// like impl methods but when doing so we must not add any
	// items to the `retained` set.
	debug!("Stripper: recursing into stripped {:?} {:?}", i.type_(), i.name);
	let old = mem::replace(&mut self.update_retained, false);
	let ret = self.fold_item_recur(i);
	self.update_retained = old;
	return ret;
	}
	// These items can all get re-exported
	clean::OpaqueTyItem(..)
	\| clean::TypedefItem(..)
	\| clean::StaticItem(..)
	\| clean::StructItem(..)
	\| clean::EnumItem(..)
	\| clean::TraitItem(..)
	\| clean::FunctionItem(..)
	\| clean::VariantItem(..)
	\| clean::MethodItem(..)
	\| clean::ForeignFunctionItem(..)
	\| clean::ForeignStaticItem(..)
	\| clean::ConstantItem(..)
	\| clean::UnionItem(..)
	\| clean::AssocConstItem(..)
	\| clean::TraitAliasItem(..)
	\| clean::ForeignTypeItem => {
	if i.def_id.is_local() {
	if !self.access_levels.is_exported(i.def_id) {
	debug!("Stripper: stripping {:?} {:?}", i.type_(), i.name);
	return None;
	}
	}
	}

	clean::StructFieldItem(..) => {
	if i.visibility != clean::Public {
	return StripItem(i).strip();
	}
	}

	clean::ModuleItem(..) => {
	if i.def_id.is_local() && i.visibility != clean::Public {
	debug!("Stripper: stripping module {:?}", i.name);
	let old = mem::replace(&mut self.update_retained, false);
	let ret = StripItem(self.fold_item_recur(i).unwrap()).strip();
	self.update_retained = old;
	return ret;
	}
	}

	// handled in the `strip-priv-imports` pass
	clean::ExternCrateItem(..) \| clean::ImportItem(..) => {}

	clean::ImplItem(..) => {}

	// tymethods/macros have no control over privacy
	clean::MacroItem(..) \| clean::TyMethodItem(..) => {}

	// Proc-macros are always public
	clean::ProcMacroItem(..) => {}

	// Primitives are never stripped
	clean::PrimitiveItem(..) => {}

	// Associated types are never stripped
	clean::AssocTypeItem(..) => {}

	// Keywords are never stripped
	clean::KeywordItem(..) => {}
	}

	let fastreturn = match i.inner {
	// nothing left to do for traits (don't want to filter their
	// methods out, visibility controlled by the trait)
	clean::TraitItem(..) => true,

	// implementations of traits are always public.
	clean::ImplItem(ref imp) if imp.trait_.is_some() => true,
	// Struct variant fields have inherited visibility
	clean::VariantItem(clean::Variant { kind: clean::VariantKind::Struct(..) }) => true,
	_ => false,
	};

	let i = if fastreturn {
	if self.update_retained {
	self.retained.insert(i.def_id);
	}
	return Some(i);
	} else {
	self.fold_item_recur(i)
	};

	if let Some(ref i) = i {
	if self.update_retained {
	self.retained.insert(i.def_id);
	}
	}
	i
	}
	}

	// This stripper discards all impls which reference stripped items
	struct ImplStripper<'a> {
	retained: &'a DefIdSet,
	}

	impl<'a> DocFolder for ImplStripper<'a> {
	fn fold_item(&mut self, i: Item) -> Option<Item> {
	if let clean::ImplItem(ref imp) = i.inner {
	// emptied none trait impls can be stripped
	if imp.trait_.is_none() && imp.items.is_empty() {
	return None;
	}
	if let Some(did) = imp.for_.def_id() {
	if did.is_local() && !imp.for_.is_generic() && !self.retained.contains(&did) {
	debug!("ImplStripper: impl item for stripped type; removing");
	return None;
	}
	}
	if let Some(did) = imp.trait_.def_id() {
	if did.is_local() && !self.retained.contains(&did) {
	debug!("ImplStripper: impl item for stripped trait; removing");
	return None;
	}
	}
	if let Some(generics) = imp.trait_.as_ref().and_then(\|t\| t.generics()) {
	for typaram in generics {
	if let Some(did) = typaram.def_id() {
	if did.is_local() && !self.retained.contains(&did) {
	debug!(
	"ImplStripper: stripped item in trait's generics; removing impl"
	);
	return None;
	}
	}
	}
	}
	}
	self.fold_item_recur(i)
	}
	}

	// This stripper discards all private import statements (`use`, `extern crate`)
	struct ImportStripper;
	impl DocFolder for ImportStripper {
	fn fold_item(&mut self, i: Item) -> Option<Item> {
	match i.inner {
	clean::ExternCrateItem(..) \| clean::ImportItem(..) if i.visibility != clean::Public => {
	None
	}
	_ => self.fold_item_recur(i),
	}
	}
	}

	/// Returns a span encompassing all the given attributes.
	crate fn span_of_attrs(attrs: &clean::Attributes) -> Option<Span> {
	if attrs.doc_strings.is_empty() {
	return None;
	}
	let start = attrs.doc_strings[0].span();
	if start == DUMMY_SP {
	return None;
	}
	let end = attrs.doc_strings.last().expect("no doc strings provided").span();
	Some(start.to(end))
	}

	/// Attempts to match a range of bytes from parsed markdown to a `Span` in the source code.
	///
	/// This method will return `None` if we cannot construct a span from the source map or if the
	/// attributes are not all sugared doc comments. It's difficult to calculate the correct span in
	/// that case due to escaping and other source features.
	crate fn source_span_for_markdown_range(
	cx: &DocContext<'_>,
	markdown: &str,
	md_range: &Range<usize>,
	attrs: &clean::Attributes,
	) -> Option<Span> {
	let is_all_sugared_doc = attrs.doc_strings.iter().all(\|frag\| match frag {
	clean::DocFragment::SugaredDoc(..) => true,
	_ => false,
	});

	if !is_all_sugared_doc {
	return None;
	}

	let snippet = cx.sess().source_map().span_to_snippet(span_of_attrs(attrs)?).ok()?;

	let starting_line = markdown[..md_range.start].matches('\n').count();
	let ending_line = starting_line + markdown[md_range.start..md_range.end].matches('\n').count();

	// We use `split_terminator('\n')` instead of `lines()` when counting bytes so that we treat
	// CRLF and LF line endings the same way.
	let mut src_lines = snippet.split_terminator('\n');
	let md_lines = markdown.split_terminator('\n');

	// The number of bytes from the source span to the markdown span that are not part
	// of the markdown, like comment markers.
	let mut start_bytes = 0;
	let mut end_bytes = 0;

	'outer: for (line_no, md_line) in md_lines.enumerate() {
	loop {
	let source_line = src_lines.next().expect("could not find markdown in source");
	match source_line.find(md_line) {
	Some(offset) => {
	if line_no == starting_line {
	start_bytes += offset;

	if starting_line == ending_line {
	break 'outer;
	}
	} else if line_no == ending_line {
	end_bytes += offset;
	break 'outer;
	} else if line_no < starting_line {
	start_bytes += source_line.len() - md_line.len();
	} else {
	end_bytes += source_line.len() - md_line.len();
	}
	break;
	}
	None => {
	// Since this is a source line that doesn't include a markdown line,
	// we have to count the newline that we split from earlier.
	if line_no <= starting_line {
	start_bytes += source_line.len() + 1;
	} else {
	end_bytes += source_line.len() + 1;
	}
	}
	}
	}
	}

	Some(span_of_attrs(attrs)?.from_inner(InnerSpan::new(
	md_range.start + start_bytes,
	md_range.end + start_bytes + end_bytes,
	)))
	}