Adding upstream version 1.64.0+dfsg1.upstream/1.64.0+dfsg1

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

14 files changed, 4444 insertions, 0 deletions

diff --git a/src/librustdoc/passes/bare_urls.rs b/src/librustdoc/passes/bare_urls.rs
new file mode 100644
index 000000000..392e26ea6
--- /dev/null
+++ b/src/librustdoc/passes/bare_urls.rs
@@ -0,0 +1,112 @@
+//! Detects links that are not linkified, e.g., in Markdown such as `Go to https://example.com/.`
+//! Suggests wrapping the link with angle brackets: `Go to <https://example.com/>.` to linkify it.
+use super::Pass;
+use crate::clean::*;
+use crate::core::DocContext;
+use crate::html::markdown::main_body_opts;
+use crate::visit::DocVisitor;
+use core::ops::Range;
+use pulldown_cmark::{Event, Parser, Tag};
+use regex::Regex;
+use rustc_errors::Applicability;
+use std::mem;
+use std::sync::LazyLock;
+
+pub(crate) const CHECK_BARE_URLS: Pass = Pass {
+    name: "check-bare-urls",
+    run: check_bare_urls,
+    description: "detects URLs that are not hyperlinks",
+};
+
+static URL_REGEX: LazyLock<Regex> = LazyLock::new(|| {
+    Regex::new(concat!(
+        r"https?://",                          // url scheme
+        r"([-a-zA-Z0-9@:%._\+~#=]{2,256}\.)+", // one or more subdomains
+        r"[a-zA-Z]{2,63}",                     // root domain
+        r"\b([-a-zA-Z0-9@:%_\+.~#?&/=]*)"      // optional query or url fragments
+    ))
+    .expect("failed to build regex")
+});
+
+struct BareUrlsLinter<'a, 'tcx> {
+    cx: &'a mut DocContext<'tcx>,
+}
+
+impl<'a, 'tcx> BareUrlsLinter<'a, 'tcx> {
+    fn find_raw_urls(
+        &self,
+        text: &str,
+        range: Range<usize>,
+        f: &impl Fn(&DocContext<'_>, &str, &str, Range<usize>),
+    ) {
+        trace!("looking for raw urls in {}", text);
+        // For now, we only check "full" URLs (meaning, starting with "http://" or "https://").
+        for match_ in URL_REGEX.find_iter(text) {
+            let url = match_.as_str();
+            let url_range = match_.range();
+            f(
+                self.cx,
+                "this URL is not a hyperlink",
+                url,
+                Range { start: range.start + url_range.start, end: range.start + url_range.end },
+            );
+        }
+    }
+}
+
+pub(crate) fn check_bare_urls(krate: Crate, cx: &mut DocContext<'_>) -> Crate {
+    BareUrlsLinter { cx }.visit_crate(&krate);
+    krate
+}
+
+impl<'a, 'tcx> DocVisitor for BareUrlsLinter<'a, 'tcx> {
+    fn visit_item(&mut self, item: &Item) {
+        let Some(hir_id) = DocContext::as_local_hir_id(self.cx.tcx, item.item_id)
+        else {
+            // If non-local, no need to check anything.
+            return;
+        };
+        let dox = item.attrs.collapsed_doc_value().unwrap_or_default();
+        if !dox.is_empty() {
+            let report_diag = |cx: &DocContext<'_>, msg: &str, url: &str, range: Range<usize>| {
+                let sp = super::source_span_for_markdown_range(cx.tcx, &dox, &range, &item.attrs)
+                    .unwrap_or_else(|| item.attr_span(cx.tcx));
+                cx.tcx.struct_span_lint_hir(crate::lint::BARE_URLS, hir_id, sp, |lint| {
+                    lint.build(msg)
+                        .note("bare URLs are not automatically turned into clickable links")
+                        .span_suggestion(
+                            sp,
+                            "use an automatic link instead",
+                            format!("<{}>", url),
+                            Applicability::MachineApplicable,
+                        )
+                        .emit();
+                });
+            };
+
+            let mut p = Parser::new_ext(&dox, main_body_opts()).into_offset_iter();
+
+            while let Some((event, range)) = p.next() {
+                match event {
+                    Event::Text(s) => self.find_raw_urls(&s, range, &report_diag),
+                    // We don't want to check the text inside code blocks or links.
+                    Event::Start(tag @ (Tag::CodeBlock(_) | Tag::Link(..))) => {
+                        while let Some((event, _)) = p.next() {
+                            match event {
+                                Event::End(end)
+                                    if mem::discriminant(&end) == mem::discriminant(&tag) =>
+                                {
+                                    break;
+                                }
+                                _ => {}
+                            }
+                        }
+                    }
+                    _ => {}
+                }
+            }
+        }
+
+        self.visit_item_recur(item)
+    }
+}
diff --git a/src/librustdoc/passes/calculate_doc_coverage.rs b/src/librustdoc/passes/calculate_doc_coverage.rs
new file mode 100644
index 000000000..4c6e3eb04
--- /dev/null
+++ b/src/librustdoc/passes/calculate_doc_coverage.rs
@@ -0,0 +1,276 @@
+//! Calculates information used for the --show-coverage flag.
+use crate::clean;
+use crate::core::DocContext;
+use crate::html::markdown::{find_testable_code, ErrorCodes};
+use crate::passes::check_doc_test_visibility::{should_have_doc_example, Tests};
+use crate::passes::Pass;
+use crate::visit::DocVisitor;
+use rustc_hir as hir;
+use rustc_lint::builtin::MISSING_DOCS;
+use rustc_middle::lint::LintLevelSource;
+use rustc_middle::ty::DefIdTree;
+use rustc_session::lint;
+use rustc_span::FileName;
+use serde::Serialize;
+
+use std::collections::BTreeMap;
+use std::ops;
+
+pub(crate) const CALCULATE_DOC_COVERAGE: Pass = Pass {
+    name: "calculate-doc-coverage",
+    run: calculate_doc_coverage,
+    description: "counts the number of items with and without documentation",
+};
+
+fn calculate_doc_coverage(krate: clean::Crate, ctx: &mut DocContext<'_>) -> clean::Crate {
+    let mut calc = CoverageCalculator { items: Default::default(), ctx };
+    calc.visit_crate(&krate);
+
+    calc.print_results();
+
+    krate
+}
+
+#[derive(Default, Copy, Clone, Serialize, Debug)]
+struct ItemCount {
+    total: u64,
+    with_docs: u64,
+    total_examples: u64,
+    with_examples: u64,
+}
+
+impl ItemCount {
+    fn count_item(
+        &mut self,
+        has_docs: bool,
+        has_doc_example: bool,
+        should_have_doc_examples: bool,
+        should_have_docs: bool,
+    ) {
+        if has_docs || should_have_docs {
+            self.total += 1;
+        }
+
+        if has_docs {
+            self.with_docs += 1;
+        }
+        if should_have_doc_examples || has_doc_example {
+            self.total_examples += 1;
+        }
+        if has_doc_example {
+            self.with_examples += 1;
+        }
+    }
+
+    fn percentage(&self) -> Option<f64> {
+        if self.total > 0 {
+            Some((self.with_docs as f64 * 100.0) / self.total as f64)
+        } else {
+            None
+        }
+    }
+
+    fn examples_percentage(&self) -> Option<f64> {
+        if self.total_examples > 0 {
+            Some((self.with_examples as f64 * 100.0) / self.total_examples as f64)
+        } else {
+            None
+        }
+    }
+}
+
+impl ops::Sub for ItemCount {
+    type Output = Self;
+
+    fn sub(self, rhs: Self) -> Self {
+        ItemCount {
+            total: self.total - rhs.total,
+            with_docs: self.with_docs - rhs.with_docs,
+            total_examples: self.total_examples - rhs.total_examples,
+            with_examples: self.with_examples - rhs.with_examples,
+        }
+    }
+}
+
+impl ops::AddAssign for ItemCount {
+    fn add_assign(&mut self, rhs: Self) {
+        self.total += rhs.total;
+        self.with_docs += rhs.with_docs;
+        self.total_examples += rhs.total_examples;
+        self.with_examples += rhs.with_examples;
+    }
+}
+
+struct CoverageCalculator<'a, 'b> {
+    items: BTreeMap<FileName, ItemCount>,
+    ctx: &'a mut DocContext<'b>,
+}
+
+fn limit_filename_len(filename: String) -> String {
+    let nb_chars = filename.chars().count();
+    if nb_chars > 35 {
+        "...".to_string()
+            + &filename[filename.char_indices().nth(nb_chars - 32).map(|x| x.0).unwrap_or(0)..]
+    } else {
+        filename
+    }
+}
+
+impl<'a, 'b> CoverageCalculator<'a, 'b> {
+    fn to_json(&self) -> String {
+        serde_json::to_string(
+            &self
+                .items
+                .iter()
+                .map(|(k, v)| (k.prefer_local().to_string(), v))
+                .collect::<BTreeMap<String, &ItemCount>>(),
+        )
+        .expect("failed to convert JSON data to string")
+    }
+
+    fn print_results(&self) {
+        let output_format = self.ctx.output_format;
+        if output_format.is_json() {
+            println!("{}", self.to_json());
+            return;
+        }
+        let mut total = ItemCount::default();
+
+        fn print_table_line() {
+            println!("+-{0:->35}-+-{0:->10}-+-{0:->10}-+-{0:->10}-+-{0:->10}-+", "");
+        }
+
+        fn print_table_record(
+            name: &str,
+            count: ItemCount,
+            percentage: f64,
+            examples_percentage: f64,
+        ) {
+            println!(
+                "| {:<35} | {:>10} | {:>9.1}% | {:>10} | {:>9.1}% |",
+                name, count.with_docs, percentage, count.with_examples, examples_percentage,
+            );
+        }
+
+        print_table_line();
+        println!(
+            "| {:<35} | {:>10} | {:>10} | {:>10} | {:>10} |",
+            "File", "Documented", "Percentage", "Examples", "Percentage",
+        );
+        print_table_line();
+
+        for (file, &count) in &self.items {
+            if let Some(percentage) = count.percentage() {
+                print_table_record(
+                    &limit_filename_len(file.prefer_local().to_string_lossy().into()),
+                    count,
+                    percentage,
+                    count.examples_percentage().unwrap_or(0.),
+                );
+
+                total += count;
+            }
+        }
+
+        print_table_line();
+        print_table_record(
+            "Total",
+            total,
+            total.percentage().unwrap_or(0.0),
+            total.examples_percentage().unwrap_or(0.0),
+        );
+        print_table_line();
+    }
+}
+
+impl<'a, 'b> DocVisitor for CoverageCalculator<'a, 'b> {
+    fn visit_item(&mut self, i: &clean::Item) {
+        if !i.item_id.is_local() {
+            // non-local items are skipped because they can be out of the users control,
+            // especially in the case of trait impls, which rustdoc eagerly inlines
+            return;
+        }
+
+        match *i.kind {
+            clean::StrippedItem(..) => {
+                // don't count items in stripped modules
+                return;
+            }
+            // docs on `use` and `extern crate` statements are not displayed, so they're not
+            // worth counting
+            clean::ImportItem(..) | clean::ExternCrateItem { .. } => {}
+            // Don't count trait impls, the missing-docs lint doesn't so we shouldn't either.
+            // Inherent impls *can* be documented, and those docs show up, but in most cases it
+            // doesn't make sense, as all methods on a type are in one single impl block
+            clean::ImplItem(_) => {}
+            _ => {
+                let has_docs = !i.attrs.doc_strings.is_empty();
+                let mut tests = Tests { found_tests: 0 };
+
+                find_testable_code(
+                    &i.attrs.collapsed_doc_value().unwrap_or_default(),
+                    &mut tests,
+                    ErrorCodes::No,
+                    false,
+                    None,
+                );
+
+                let filename = i.span(self.ctx.tcx).filename(self.ctx.sess());
+                let has_doc_example = tests.found_tests != 0;
+                // The `expect_def_id()` should be okay because `local_def_id_to_hir_id`
+                // would presumably panic if a fake `DefIndex` were passed.
+                let hir_id = self
+                    .ctx
+                    .tcx
+                    .hir()
+                    .local_def_id_to_hir_id(i.item_id.expect_def_id().expect_local());
+                let (level, source) = self.ctx.tcx.lint_level_at_node(MISSING_DOCS, hir_id);
+
+                // In case we have:
+                //
+                // ```
+                // enum Foo { Bar(u32) }
+                // // or:
+                // struct Bar(u32);
+                // ```
+                //
+                // there is no need to require documentation on the fields of tuple variants and
+                // tuple structs.
+                let should_be_ignored = i
+                    .item_id
+                    .as_def_id()
+                    .and_then(|def_id| self.ctx.tcx.opt_parent(def_id))
+                    .and_then(|def_id| self.ctx.tcx.hir().get_if_local(def_id))
+                    .map(|node| {
+                        matches!(
+                            node,
+                            hir::Node::Variant(hir::Variant {
+                                data: hir::VariantData::Tuple(_, _),
+                                ..
+                            }) | hir::Node::Item(hir::Item {
+                                kind: hir::ItemKind::Struct(hir::VariantData::Tuple(_, _), _),
+                                ..
+                            })
+                        )
+                    })
+                    .unwrap_or(false);
+
+                // `missing_docs` is allow-by-default, so don't treat this as ignoring the item
+                // unless the user had an explicit `allow`.
+                //
+                let should_have_docs = !should_be_ignored
+                    && (level != lint::Level::Allow || matches!(source, LintLevelSource::Default));
+
+                debug!("counting {:?} {:?} in {:?}", i.type_(), i.name, filename);
+                self.items.entry(filename).or_default().count_item(
+                    has_docs,
+                    has_doc_example,
+                    should_have_doc_example(self.ctx, i),
+                    should_have_docs,
+                );
+            }
+        }
+
+        self.visit_item_recur(i)
+    }
+}
diff --git a/src/librustdoc/passes/check_code_block_syntax.rs b/src/librustdoc/passes/check_code_block_syntax.rs
new file mode 100644
index 000000000..0172ef570
--- /dev/null
+++ b/src/librustdoc/passes/check_code_block_syntax.rs
@@ -0,0 +1,205 @@
+//! Validates syntax inside Rust code blocks (\`\`\`rust).
+use rustc_data_structures::sync::{Lock, Lrc};
+use rustc_errors::{
+    emitter::Emitter, Applicability, Diagnostic, Handler, LazyFallbackBundle, LintDiagnosticBuilder,
+};
+use rustc_parse::parse_stream_from_source_str;
+use rustc_session::parse::ParseSess;
+use rustc_span::hygiene::{AstPass, ExpnData, ExpnKind, LocalExpnId};
+use rustc_span::source_map::{FilePathMapping, SourceMap};
+use rustc_span::{FileName, InnerSpan, DUMMY_SP};
+
+use crate::clean;
+use crate::core::DocContext;
+use crate::html::markdown::{self, RustCodeBlock};
+use crate::passes::Pass;
+use crate::visit::DocVisitor;
+
+pub(crate) const CHECK_CODE_BLOCK_SYNTAX: Pass = Pass {
+    name: "check-code-block-syntax",
+    run: check_code_block_syntax,
+    description: "validates syntax inside Rust code blocks",
+};
+
+pub(crate) fn check_code_block_syntax(
+    krate: clean::Crate,
+    cx: &mut DocContext<'_>,
+) -> clean::Crate {
+    SyntaxChecker { cx }.visit_crate(&krate);
+    krate
+}
+
+struct SyntaxChecker<'a, 'tcx> {
+    cx: &'a DocContext<'tcx>,
+}
+
+impl<'a, 'tcx> SyntaxChecker<'a, 'tcx> {
+    fn check_rust_syntax(&self, item: &clean::Item, dox: &str, code_block: RustCodeBlock) {
+        let buffer = Lrc::new(Lock::new(Buffer::default()));
+        let fallback_bundle =
+            rustc_errors::fallback_fluent_bundle(rustc_errors::DEFAULT_LOCALE_RESOURCES, false);
+        let emitter = BufferEmitter { buffer: Lrc::clone(&buffer), fallback_bundle };
+
+        let sm = Lrc::new(SourceMap::new(FilePathMapping::empty()));
+        let handler = Handler::with_emitter(false, None, Box::new(emitter));
+        let source = dox[code_block.code].to_owned();
+        let sess = ParseSess::with_span_handler(handler, sm);
+
+        let edition = code_block.lang_string.edition.unwrap_or_else(|| self.cx.tcx.sess.edition());
+        let expn_data = ExpnData::default(
+            ExpnKind::AstPass(AstPass::TestHarness),
+            DUMMY_SP,
+            edition,
+            None,
+            None,
+        );
+        let expn_id =
+            self.cx.tcx.with_stable_hashing_context(|hcx| LocalExpnId::fresh(expn_data, hcx));
+        let span = DUMMY_SP.fresh_expansion(expn_id);
+
+        let is_empty = rustc_driver::catch_fatal_errors(|| {
+            parse_stream_from_source_str(
+                FileName::Custom(String::from("doctest")),
+                source,
+                &sess,
+                Some(span),
+            )
+            .is_empty()
+        })
+        .unwrap_or(false);
+        let buffer = buffer.borrow();
+
+        if !buffer.has_errors && !is_empty {
+            // No errors in a non-empty program.
+            return;
+        }
+
+        let Some(local_id) = item.item_id.as_def_id().and_then(|x| x.as_local())
+        else {
+            // We don't need to check the syntax for other crates so returning
+            // without doing anything should not be a problem.
+            return;
+        };
+
+        let hir_id = self.cx.tcx.hir().local_def_id_to_hir_id(local_id);
+        let empty_block = code_block.lang_string == Default::default() && code_block.is_fenced;
+        let is_ignore = code_block.lang_string.ignore != markdown::Ignore::None;
+
+        // The span and whether it is precise or not.
+        let (sp, precise_span) = match super::source_span_for_markdown_range(
+            self.cx.tcx,
+            dox,
+            &code_block.range,
+            &item.attrs,
+        ) {
+            Some(sp) => (sp, true),
+            None => (item.attr_span(self.cx.tcx), false),
+        };
+
+        // lambda that will use the lint to start a new diagnostic and add
+        // a suggestion to it when needed.
+        let diag_builder = |lint: LintDiagnosticBuilder<'_, ()>| {
+            let explanation = if is_ignore {
+                "`ignore` code blocks require valid Rust code for syntax highlighting; \
+                    mark blocks that do not contain Rust code as text"
+            } else {
+                "mark blocks that do not contain Rust code as text"
+            };
+            let msg = if buffer.has_errors {
+                "could not parse code block as Rust code"
+            } else {
+                "Rust code block is empty"
+            };
+            let mut diag = lint.build(msg);
+
+            if precise_span {
+                if is_ignore {
+                    // giving an accurate suggestion is hard because `ignore` might not have come first in the list.
+                    // just give a `help` instead.
+                    diag.span_help(
+                        sp.from_inner(InnerSpan::new(0, 3)),
+                        &format!("{}: ```text", explanation),
+                    );
+                } else if empty_block {
+                    diag.span_suggestion(
+                        sp.from_inner(InnerSpan::new(0, 3)).shrink_to_hi(),
+                        explanation,
+                        "text",
+                        Applicability::MachineApplicable,
+                    );
+                }
+            } else if empty_block || is_ignore {
+                diag.help(&format!("{}: ```text", explanation));
+            }
+
+            // FIXME(#67563): Provide more context for these errors by displaying the spans inline.
+            for message in buffer.messages.iter() {
+                diag.note(message);
+            }
+
+            diag.emit();
+        };
+
+        // Finally build and emit the completed diagnostic.
+        // All points of divergence have been handled earlier so this can be
+        // done the same way whether the span is precise or not.
+        self.cx.tcx.struct_span_lint_hir(
+            crate::lint::INVALID_RUST_CODEBLOCKS,
+            hir_id,
+            sp,
+            diag_builder,
+        );
+    }
+}
+
+impl<'a, 'tcx> DocVisitor for SyntaxChecker<'a, 'tcx> {
+    fn visit_item(&mut self, item: &clean::Item) {
+        if let Some(dox) = &item.attrs.collapsed_doc_value() {
+            let sp = item.attr_span(self.cx.tcx);
+            let extra = crate::html::markdown::ExtraInfo::new_did(
+                self.cx.tcx,
+                item.item_id.expect_def_id(),
+                sp,
+            );
+            for code_block in markdown::rust_code_blocks(dox, &extra) {
+                self.check_rust_syntax(item, dox, code_block);
+            }
+        }
+
+        self.visit_item_recur(item)
+    }
+}
+
+#[derive(Default)]
+struct Buffer {
+    messages: Vec<String>,
+    has_errors: bool,
+}
+
+struct BufferEmitter {
+    buffer: Lrc<Lock<Buffer>>,
+    fallback_bundle: LazyFallbackBundle,
+}
+
+impl Emitter for BufferEmitter {
+    fn emit_diagnostic(&mut self, diag: &Diagnostic) {
+        let mut buffer = self.buffer.borrow_mut();
+        // FIXME(davidtwco): need to support translation here eventually
+        buffer.messages.push(format!("error from rustc: {}", diag.message[0].0.expect_str()));
+        if diag.is_error() {
+            buffer.has_errors = true;
+        }
+    }
+
+    fn source_map(&self) -> Option<&Lrc<SourceMap>> {
+        None
+    }
+
+    fn fluent_bundle(&self) -> Option<&Lrc<rustc_errors::FluentBundle>> {
+        None
+    }
+
+    fn fallback_fluent_bundle(&self) -> &rustc_errors::FluentBundle {
+        &**self.fallback_bundle
+    }
+}
diff --git a/src/librustdoc/passes/check_doc_test_visibility.rs b/src/librustdoc/passes/check_doc_test_visibility.rs
new file mode 100644
index 000000000..e86f90833
--- /dev/null
+++ b/src/librustdoc/passes/check_doc_test_visibility.rs
@@ -0,0 +1,145 @@
+//! Looks for items missing (or incorrectly having) doctests.
+//!
+//! This pass is overloaded and runs two different lints.
+//!
+//! - MISSING_DOC_CODE_EXAMPLES: this lint is **UNSTABLE** and looks for public items missing doctests.
+//! - PRIVATE_DOC_TESTS: this lint is **STABLE** and looks for private items with doctests.
+
+use super::Pass;
+use crate::clean;
+use crate::clean::*;
+use crate::core::DocContext;
+use crate::html::markdown::{find_testable_code, ErrorCodes, Ignore, LangString};
+use crate::visit::DocVisitor;
+use crate::visit_ast::inherits_doc_hidden;
+use rustc_hir as hir;
+use rustc_middle::lint::LintLevelSource;
+use rustc_session::lint;
+use rustc_span::symbol::sym;
+
+pub(crate) const CHECK_DOC_TEST_VISIBILITY: Pass = Pass {
+    name: "check_doc_test_visibility",
+    run: check_doc_test_visibility,
+    description: "run various visibility-related lints on doctests",
+};
+
+struct DocTestVisibilityLinter<'a, 'tcx> {
+    cx: &'a mut DocContext<'tcx>,
+}
+
+pub(crate) fn check_doc_test_visibility(krate: Crate, cx: &mut DocContext<'_>) -> Crate {
+    let mut coll = DocTestVisibilityLinter { cx };
+    coll.visit_crate(&krate);
+    krate
+}
+
+impl<'a, 'tcx> DocVisitor for DocTestVisibilityLinter<'a, 'tcx> {
+    fn visit_item(&mut self, item: &Item) {
+        let dox = item.attrs.collapsed_doc_value().unwrap_or_default();
+
+        look_for_tests(self.cx, &dox, item);
+
+        self.visit_item_recur(item)
+    }
+}
+
+pub(crate) struct Tests {
+    pub(crate) found_tests: usize,
+}
+
+impl crate::doctest::Tester for Tests {
+    fn add_test(&mut self, _: String, config: LangString, _: usize) {
+        if config.rust && config.ignore == Ignore::None {
+            self.found_tests += 1;
+        }
+    }
+}
+
+pub(crate) fn should_have_doc_example(cx: &DocContext<'_>, item: &clean::Item) -> bool {
+    if !cx.cache.access_levels.is_public(item.item_id.expect_def_id())
+        || matches!(
+            *item.kind,
+            clean::StructFieldItem(_)
+                | clean::VariantItem(_)
+                | clean::AssocConstItem(..)
+                | clean::AssocTypeItem(..)
+                | clean::TypedefItem(_)
+                | clean::StaticItem(_)
+                | clean::ConstantItem(_)
+                | clean::ExternCrateItem { .. }
+                | clean::ImportItem(_)
+                | clean::PrimitiveItem(_)
+                | clean::KeywordItem
+                // check for trait impl
+                | clean::ImplItem(box clean::Impl { trait_: Some(_), .. })
+        )
+    {
+        return false;
+    }
+
+    // The `expect_def_id()` should be okay because `local_def_id_to_hir_id`
+    // would presumably panic if a fake `DefIndex` were passed.
+    let hir_id = cx.tcx.hir().local_def_id_to_hir_id(item.item_id.expect_def_id().expect_local());
+
+    // check if parent is trait impl
+    if let Some(parent_hir_id) = cx.tcx.hir().find_parent_node(hir_id) {
+        if let Some(parent_node) = cx.tcx.hir().find(parent_hir_id) {
+            if matches!(
+                parent_node,
+                hir::Node::Item(hir::Item {
+                    kind: hir::ItemKind::Impl(hir::Impl { of_trait: Some(_), .. }),
+                    ..
+                })
+            ) {
+                return false;
+            }
+        }
+    }
+
+    if cx.tcx.hir().attrs(hir_id).lists(sym::doc).has_word(sym::hidden)
+        || inherits_doc_hidden(cx.tcx, hir_id)
+        || cx.tcx.hir().span(hir_id).in_derive_expansion()
+    {
+        return false;
+    }
+    let (level, source) = cx.tcx.lint_level_at_node(crate::lint::MISSING_DOC_CODE_EXAMPLES, hir_id);
+    level != lint::Level::Allow || matches!(source, LintLevelSource::Default)
+}
+
+pub(crate) fn look_for_tests<'tcx>(cx: &DocContext<'tcx>, dox: &str, item: &Item) {
+    let Some(hir_id) = DocContext::as_local_hir_id(cx.tcx, item.item_id)
+    else {
+        // If non-local, no need to check anything.
+        return;
+    };
+
+    let mut tests = Tests { found_tests: 0 };
+
+    find_testable_code(dox, &mut tests, ErrorCodes::No, false, None);
+
+    if tests.found_tests == 0 && cx.tcx.sess.is_nightly_build() {
+        if should_have_doc_example(cx, item) {
+            debug!("reporting error for {:?} (hir_id={:?})", item, hir_id);
+            let sp = item.attr_span(cx.tcx);
+            cx.tcx.struct_span_lint_hir(
+                crate::lint::MISSING_DOC_CODE_EXAMPLES,
+                hir_id,
+                sp,
+                |lint| {
+                    lint.build("missing code example in this documentation").emit();
+                },
+            );
+        }
+    } else if tests.found_tests > 0
+        && !cx.cache.access_levels.is_exported(item.item_id.expect_def_id())
+    {
+        cx.tcx.struct_span_lint_hir(
+            crate::lint::PRIVATE_DOC_TESTS,
+            hir_id,
+            item.attr_span(cx.tcx),
+            |lint| {
+                lint.build("documentation test in private item").emit();
+            },
+        );
+    }
+}
diff --git a/src/librustdoc/passes/collect_intra_doc_links.rs b/src/librustdoc/passes/collect_intra_doc_links.rs
new file mode 100644
index 000000000..7d7a63c53
--- /dev/null
+++ b/src/librustdoc/passes/collect_intra_doc_links.rs
@@ -0,0 +1,2161 @@
+//! This module implements [RFC 1946]: Intra-rustdoc-links
+//!
+//! [RFC 1946]: https://github.com/rust-lang/rfcs/blob/master/text/1946-intra-rustdoc-links.md
+
+use pulldown_cmark::LinkType;
+use rustc_ast::util::comments::may_have_doc_links;
+use rustc_data_structures::{
+    fx::{FxHashMap, FxHashSet},
+    intern::Interned,
+};
+use rustc_errors::{Applicability, Diagnostic};
+use rustc_hir::def::Namespace::*;
+use rustc_hir::def::{DefKind, Namespace, PerNS};
+use rustc_hir::def_id::{DefId, CRATE_DEF_ID};
+use rustc_hir::Mutability;
+use rustc_middle::ty::{DefIdTree, Ty, TyCtxt};
+use rustc_middle::{bug, ty};
+use rustc_resolve::ParentScope;
+use rustc_session::lint::Lint;
+use rustc_span::hygiene::MacroKind;
+use rustc_span::symbol::{sym, Ident, Symbol};
+use rustc_span::BytePos;
+use smallvec::{smallvec, SmallVec};
+
+use std::borrow::Cow;
+use std::mem;
+use std::ops::Range;
+
+use crate::clean::{self, utils::find_nearest_parent_module};
+use crate::clean::{Crate, Item, ItemId, ItemLink, PrimitiveType};
+use crate::core::DocContext;
+use crate::html::markdown::{markdown_links, MarkdownLink};
+use crate::lint::{BROKEN_INTRA_DOC_LINKS, PRIVATE_INTRA_DOC_LINKS};
+use crate::passes::Pass;
+use crate::visit::DocVisitor;
+
+mod early;
+pub(crate) use early::early_resolve_intra_doc_links;
+
+pub(crate) const COLLECT_INTRA_DOC_LINKS: Pass = Pass {
+    name: "collect-intra-doc-links",
+    run: collect_intra_doc_links,
+    description: "resolves intra-doc links",
+};
+
+fn collect_intra_doc_links(krate: Crate, cx: &mut DocContext<'_>) -> Crate {
+    let mut collector =
+        LinkCollector { cx, mod_ids: Vec::new(), visited_links: FxHashMap::default() };
+    collector.visit_crate(&krate);
+    krate
+}
+
+#[derive(Copy, Clone, Debug, Hash)]
+enum Res {
+    Def(DefKind, DefId),
+    Primitive(PrimitiveType),
+}
+
+type ResolveRes = rustc_hir::def::Res<rustc_ast::NodeId>;
+
+impl Res {
+    fn descr(self) -> &'static str {
+        match self {
+            Res::Def(kind, id) => ResolveRes::Def(kind, id).descr(),
+            Res::Primitive(_) => "builtin type",
+        }
+    }
+
+    fn article(self) -> &'static str {
+        match self {
+            Res::Def(kind, id) => ResolveRes::Def(kind, id).article(),
+            Res::Primitive(_) => "a",
+        }
+    }
+
+    fn name(self, tcx: TyCtxt<'_>) -> Symbol {
+        match self {
+            Res::Def(_, id) => tcx.item_name(id),
+            Res::Primitive(prim) => prim.as_sym(),
+        }
+    }
+
+    fn def_id(self, tcx: TyCtxt<'_>) -> DefId {
+        match self {
+            Res::Def(_, id) => id,
+            Res::Primitive(prim) => *PrimitiveType::primitive_locations(tcx).get(&prim).unwrap(),
+        }
+    }
+
+    fn from_def_id(tcx: TyCtxt<'_>, def_id: DefId) -> Res {
+        Res::Def(tcx.def_kind(def_id), def_id)
+    }
+
+    /// Used for error reporting.
+    fn disambiguator_suggestion(self) -> Suggestion {
+        let kind = match self {
+            Res::Primitive(_) => return Suggestion::Prefix("prim"),
+            Res::Def(kind, _) => kind,
+        };
+        if kind == DefKind::Macro(MacroKind::Bang) {
+            return Suggestion::Macro;
+        } else if kind == DefKind::Fn || kind == DefKind::AssocFn {
+            return Suggestion::Function;
+        } else if kind == DefKind::Field {
+            return Suggestion::RemoveDisambiguator;
+        }
+
+        let prefix = match kind {
+            DefKind::Struct => "struct",
+            DefKind::Enum => "enum",
+            DefKind::Trait => "trait",
+            DefKind::Union => "union",
+            DefKind::Mod => "mod",
+            DefKind::Const | DefKind::ConstParam | DefKind::AssocConst | DefKind::AnonConst => {
+                "const"
+            }
+            DefKind::Static(_) => "static",
+            DefKind::Macro(MacroKind::Derive) => "derive",
+            // Now handle things that don't have a specific disambiguator
+            _ => match kind
+                .ns()
+                .expect("tried to calculate a disambiguator for a def without a namespace?")
+            {
+                Namespace::TypeNS => "type",
+                Namespace::ValueNS => "value",
+                Namespace::MacroNS => "macro",
+            },
+        };
+
+        Suggestion::Prefix(prefix)
+    }
+}
+
+impl TryFrom<ResolveRes> for Res {
+    type Error = ();
+
+    fn try_from(res: ResolveRes) -> Result<Self, ()> {
+        use rustc_hir::def::Res::*;
+        match res {
+            Def(kind, id) => Ok(Res::Def(kind, id)),
+            PrimTy(prim) => Ok(Res::Primitive(PrimitiveType::from_hir(prim))),
+            // e.g. `#[derive]`
+            NonMacroAttr(..) | Err => Result::Err(()),
+            other => bug!("unrecognized res {:?}", other),
+        }
+    }
+}
+
+/// The link failed to resolve. [`resolution_failure`] should look to see if there's
+/// a more helpful error that can be given.
+#[derive(Debug)]
+struct UnresolvedPath<'a> {
+    /// Item on which the link is resolved, used for resolving `Self`.
+    item_id: ItemId,
+    /// The scope the link was resolved in.
+    module_id: DefId,
+    /// If part of the link resolved, this has the `Res`.
+    ///
+    /// In `[std::io::Error::x]`, `std::io::Error` would be a partial resolution.
+    partial_res: Option<Res>,
+    /// The remaining unresolved path segments.
+    ///
+    /// In `[std::io::Error::x]`, `x` would be unresolved.
+    unresolved: Cow<'a, str>,
+}
+
+#[derive(Debug)]
+enum ResolutionFailure<'a> {
+    /// This resolved, but with the wrong namespace.
+    WrongNamespace {
+        /// What the link resolved to.
+        res: Res,
+        /// The expected namespace for the resolution, determined from the link's disambiguator.
+        ///
+        /// E.g., for `[fn@Result]` this is [`Namespace::ValueNS`],
+        /// even though `Result`'s actual namespace is [`Namespace::TypeNS`].
+        expected_ns: Namespace,
+    },
+    NotResolved(UnresolvedPath<'a>),
+}
+
+#[derive(Clone, Copy, Debug)]
+enum MalformedGenerics {
+    /// This link has unbalanced angle brackets.
+    ///
+    /// For example, `Vec<T` should trigger this, as should `Vec<T>>`.
+    UnbalancedAngleBrackets,
+    /// The generics are not attached to a type.
+    ///
+    /// For example, `<T>` should trigger this.
+    ///
+    /// This is detected by checking if the path is empty after the generics are stripped.
+    MissingType,
+    /// The link uses fully-qualified syntax, which is currently unsupported.
+    ///
+    /// For example, `<Vec as IntoIterator>::into_iter` should trigger this.
+    ///
+    /// This is detected by checking if ` as ` (the keyword `as` with spaces around it) is inside
+    /// angle brackets.
+    HasFullyQualifiedSyntax,
+    /// The link has an invalid path separator.
+    ///
+    /// For example, `Vec:<T>:new()` should trigger this. Note that `Vec:new()` will **not**
+    /// trigger this because it has no generics and thus [`strip_generics_from_path`] will not be
+    /// called.
+    ///
+    /// Note that this will also **not** be triggered if the invalid path separator is inside angle
+    /// brackets because rustdoc mostly ignores what's inside angle brackets (except for
+    /// [`HasFullyQualifiedSyntax`](MalformedGenerics::HasFullyQualifiedSyntax)).
+    ///
+    /// This is detected by checking if there is a colon followed by a non-colon in the link.
+    InvalidPathSeparator,
+    /// The link has too many angle brackets.
+    ///
+    /// For example, `Vec<<T>>` should trigger this.
+    TooManyAngleBrackets,
+    /// The link has empty angle brackets.
+    ///
+    /// For example, `Vec<>` should trigger this.
+    EmptyAngleBrackets,
+}
+
+#[derive(Clone, Debug, Hash, PartialEq, Eq)]
+pub(crate) enum UrlFragment {
+    Item(DefId),
+    UserWritten(String),
+}
+
+impl UrlFragment {
+    /// Render the fragment, including the leading `#`.
+    pub(crate) fn render(&self, s: &mut String, tcx: TyCtxt<'_>) {
+        s.push('#');
+        match self {
+            &UrlFragment::Item(def_id) => {
+                let kind = match tcx.def_kind(def_id) {
+                    DefKind::AssocFn => {
+                        if tcx.impl_defaultness(def_id).has_value() {
+                            "method."
+                        } else {
+                            "tymethod."
+                        }
+                    }
+                    DefKind::AssocConst => "associatedconstant.",
+                    DefKind::AssocTy => "associatedtype.",
+                    DefKind::Variant => "variant.",
+                    DefKind::Field => {
+                        let parent_id = tcx.parent(def_id);
+                        if tcx.def_kind(parent_id) == DefKind::Variant {
+                            s.push_str("variant.");
+                            s.push_str(tcx.item_name(parent_id).as_str());
+                            ".field."
+                        } else {
+                            "structfield."
+                        }
+                    }
+                    kind => bug!("unexpected associated item kind: {:?}", kind),
+                };
+                s.push_str(kind);
+                s.push_str(tcx.item_name(def_id).as_str());
+            }
+            UrlFragment::UserWritten(raw) => s.push_str(&raw),
+        }
+    }
+}
+
+#[derive(Clone, Debug, Hash, PartialEq, Eq)]
+struct ResolutionInfo {
+    item_id: ItemId,
+    module_id: DefId,
+    dis: Option<Disambiguator>,
+    path_str: String,
+    extra_fragment: Option<String>,
+}
+
+#[derive(Clone)]
+struct DiagnosticInfo<'a> {
+    item: &'a Item,
+    dox: &'a str,
+    ori_link: &'a str,
+    link_range: Range<usize>,
+}
+
+struct LinkCollector<'a, 'tcx> {
+    cx: &'a mut DocContext<'tcx>,
+    /// A stack of modules used to decide what scope to resolve in.
+    ///
+    /// The last module will be used if the parent scope of the current item is
+    /// unknown.
+    mod_ids: Vec<DefId>,
+    /// Cache the resolved links so we can avoid resolving (and emitting errors for) the same link.
+    /// The link will be `None` if it could not be resolved (i.e. the error was cached).
+    visited_links: FxHashMap<ResolutionInfo, Option<(Res, Option<UrlFragment>)>>,
+}
+
+impl<'a, 'tcx> LinkCollector<'a, 'tcx> {
+    /// Given a full link, parse it as an [enum struct variant].
+    ///
+    /// In particular, this will return an error whenever there aren't three
+    /// full path segments left in the link.
+    ///
+    /// [enum struct variant]: rustc_hir::VariantData::Struct
+    fn variant_field<'path>(
+        &self,
+        path_str: &'path str,
+        item_id: ItemId,
+        module_id: DefId,
+    ) -> Result<(Res, DefId), UnresolvedPath<'path>> {
+        let tcx = self.cx.tcx;
+        let no_res = || UnresolvedPath {
+            item_id,
+            module_id,
+            partial_res: None,
+            unresolved: path_str.into(),
+        };
+
+        debug!("looking for enum variant {}", path_str);
+        let mut split = path_str.rsplitn(3, "::");
+        let variant_field_name = split
+            .next()
+            .map(|f| Symbol::intern(f))
+            .expect("fold_item should ensure link is non-empty");
+        let variant_name =
+            // we're not sure this is a variant at all, so use the full string
+            // If there's no second component, the link looks like `[path]`.
+            // So there's no partial res and we should say the whole link failed to resolve.
+            split.next().map(|f|  Symbol::intern(f)).ok_or_else(no_res)?;
+        let path = split
+            .next()
+            .map(|f| f.to_owned())
+            // If there's no third component, we saw `[a::b]` before and it failed to resolve.
+            // So there's no partial res.
+            .ok_or_else(no_res)?;
+        let ty_res = self.resolve_path(&path, TypeNS, item_id, module_id).ok_or_else(no_res)?;
+
+        match ty_res {
+            Res::Def(DefKind::Enum, did) => match tcx.type_of(did).kind() {
+                ty::Adt(def, _) if def.is_enum() => {
+                    if let Some(field) = def.all_fields().find(|f| f.name == variant_field_name) {
+                        Ok((ty_res, field.did))
+                    } else {
+                        Err(UnresolvedPath {
+                            item_id,
+                            module_id,
+                            partial_res: Some(Res::Def(DefKind::Enum, def.did())),
+                            unresolved: variant_field_name.to_string().into(),
+                        })
+                    }
+                }
+                _ => unreachable!(),
+            },
+            _ => Err(UnresolvedPath {
+                item_id,
+                module_id,
+                partial_res: Some(ty_res),
+                unresolved: variant_name.to_string().into(),
+            }),
+        }
+    }
+
+    /// Given a primitive type, try to resolve an associated item.
+    fn resolve_primitive_associated_item(
+        &self,
+        prim_ty: PrimitiveType,
+        ns: Namespace,
+        item_name: Symbol,
+    ) -> Option<(Res, DefId)> {
+        let tcx = self.cx.tcx;
+
+        prim_ty.impls(tcx).find_map(|impl_| {
+            tcx.associated_items(impl_)
+                .find_by_name_and_namespace(tcx, Ident::with_dummy_span(item_name), ns, impl_)
+                .map(|item| (Res::Primitive(prim_ty), item.def_id))
+        })
+    }
+
+    fn resolve_self_ty(&self, path_str: &str, ns: Namespace, item_id: ItemId) -> Option<Res> {
+        if ns != TypeNS || path_str != "Self" {
+            return None;
+        }
+
+        let tcx = self.cx.tcx;
+        item_id
+            .as_def_id()
+            .map(|def_id| match tcx.def_kind(def_id) {
+                def_kind @ (DefKind::AssocFn
+                | DefKind::AssocConst
+                | DefKind::AssocTy
+                | DefKind::Variant
+                | DefKind::Field) => {
+                    let parent_def_id = tcx.parent(def_id);
+                    if def_kind == DefKind::Field && tcx.def_kind(parent_def_id) == DefKind::Variant
+                    {
+                        tcx.parent(parent_def_id)
+                    } else {
+                        parent_def_id
+                    }
+                }
+                _ => def_id,
+            })
+            .and_then(|self_id| match tcx.def_kind(self_id) {
+                DefKind::Impl => self.def_id_to_res(self_id),
+                def_kind => Some(Res::Def(def_kind, self_id)),
+            })
+    }
+
+    /// Convenience wrapper around `resolve_rustdoc_path`.
+    ///
+    /// This also handles resolving `true` and `false` as booleans.
+    /// NOTE: `resolve_rustdoc_path` knows only about paths, not about types.
+    /// Associated items will never be resolved by this function.
+    fn resolve_path(
+        &self,
+        path_str: &str,
+        ns: Namespace,
+        item_id: ItemId,
+        module_id: DefId,
+    ) -> Option<Res> {
+        if let res @ Some(..) = self.resolve_self_ty(path_str, ns, item_id) {
+            return res;
+        }
+
+        // Resolver doesn't know about true, false, and types that aren't paths (e.g. `()`).
+        let result = self
+            .cx
+            .resolver_caches
+            .doc_link_resolutions
+            .get(&(Symbol::intern(path_str), ns, module_id))
+            .copied()
+            .unwrap_or_else(|| {
+                self.cx.enter_resolver(|resolver| {
+                    let parent_scope =
+                        ParentScope::module(resolver.expect_module(module_id), resolver);
+                    resolver.resolve_rustdoc_path(path_str, ns, parent_scope)
+                })
+            })
+            .and_then(|res| res.try_into().ok())
+            .or_else(|| resolve_primitive(path_str, ns));
+        debug!("{} resolved to {:?} in namespace {:?}", path_str, result, ns);
+        result
+    }
+
+    /// Resolves a string as a path within a particular namespace. Returns an
+    /// optional URL fragment in the case of variants and methods.
+    fn resolve<'path>(
+        &mut self,
+        path_str: &'path str,
+        ns: Namespace,
+        item_id: ItemId,
+        module_id: DefId,
+    ) -> Result<(Res, Option<DefId>), UnresolvedPath<'path>> {
+        if let Some(res) = self.resolve_path(path_str, ns, item_id, module_id) {
+            return Ok(match res {
+                Res::Def(
+                    DefKind::AssocFn | DefKind::AssocConst | DefKind::AssocTy | DefKind::Variant,
+                    def_id,
+                ) => (Res::from_def_id(self.cx.tcx, self.cx.tcx.parent(def_id)), Some(def_id)),
+                _ => (res, None),
+            });
+        } else if ns == MacroNS {
+            return Err(UnresolvedPath {
+                item_id,
+                module_id,
+                partial_res: None,
+                unresolved: path_str.into(),
+            });
+        }
+
+        // Try looking for methods and associated items.
+        let mut split = path_str.rsplitn(2, "::");
+        // NB: `split`'s first element is always defined, even if the delimiter was not present.
+        // NB: `item_str` could be empty when resolving in the root namespace (e.g. `::std`).
+        let item_str = split.next().unwrap();
+        let item_name = Symbol::intern(item_str);
+        let path_root = split
+            .next()
+            .map(|f| f.to_owned())
+            // If there's no `::`, it's not an associated item.
+            // So we can be sure that `rustc_resolve` was accurate when it said it wasn't resolved.
+            .ok_or_else(|| {
+                debug!("found no `::`, assumming {} was correctly not in scope", item_name);
+                UnresolvedPath {
+                    item_id,
+                    module_id,
+                    partial_res: None,
+                    unresolved: item_str.into(),
+                }
+            })?;
+
+        // FIXME(#83862): this arbitrarily gives precedence to primitives over modules to support
+        // links to primitives when `#[doc(primitive)]` is present. It should give an ambiguity
+        // error instead and special case *only* modules with `#[doc(primitive)]`, not all
+        // primitives.
+        resolve_primitive(&path_root, TypeNS)
+            .or_else(|| self.resolve_path(&path_root, TypeNS, item_id, module_id))
+            .and_then(|ty_res| {
+                self.resolve_associated_item(ty_res, item_name, ns, module_id).map(Ok)
+            })
+            .unwrap_or_else(|| {
+                if ns == Namespace::ValueNS {
+                    self.variant_field(path_str, item_id, module_id)
+                } else {
+                    Err(UnresolvedPath {
+                        item_id,
+                        module_id,
+                        partial_res: None,
+                        unresolved: path_root.into(),
+                    })
+                }
+            })
+            .map(|(res, def_id)| (res, Some(def_id)))
+    }
+
+    /// Convert a DefId to a Res, where possible.
+    ///
+    /// This is used for resolving type aliases.
+    fn def_id_to_res(&self, ty_id: DefId) -> Option<Res> {
+        use PrimitiveType::*;
+        Some(match *self.cx.tcx.type_of(ty_id).kind() {
+            ty::Bool => Res::Primitive(Bool),
+            ty::Char => Res::Primitive(Char),
+            ty::Int(ity) => Res::Primitive(ity.into()),
+            ty::Uint(uty) => Res::Primitive(uty.into()),
+            ty::Float(fty) => Res::Primitive(fty.into()),
+            ty::Str => Res::Primitive(Str),
+            ty::Tuple(tys) if tys.is_empty() => Res::Primitive(Unit),
+            ty::Tuple(_) => Res::Primitive(Tuple),
+            ty::Array(..) => Res::Primitive(Array),
+            ty::Slice(_) => Res::Primitive(Slice),
+            ty::RawPtr(_) => Res::Primitive(RawPointer),
+            ty::Ref(..) => Res::Primitive(Reference),
+            ty::FnDef(..) => panic!("type alias to a function definition"),
+            ty::FnPtr(_) => Res::Primitive(Fn),
+            ty::Never => Res::Primitive(Never),
+            ty::Adt(ty::AdtDef(Interned(&ty::AdtDefData { did, .. }, _)), _) | ty::Foreign(did) => {
+                Res::from_def_id(self.cx.tcx, did)
+            }
+            ty::Projection(_)
+            | ty::Closure(..)
+            | ty::Generator(..)
+            | ty::GeneratorWitness(_)
+            | ty::Opaque(..)
+            | ty::Dynamic(..)
+            | ty::Param(_)
+            | ty::Bound(..)
+            | ty::Placeholder(_)
+            | ty::Infer(_)
+            | ty::Error(_) => return None,
+        })
+    }
+
+    /// Convert a PrimitiveType to a Ty, where possible.
+    ///
+    /// This is used for resolving trait impls for primitives
+    fn primitive_type_to_ty(&mut self, prim: PrimitiveType) -> Option<Ty<'tcx>> {
+        use PrimitiveType::*;
+        let tcx = self.cx.tcx;
+
+        // FIXME: Only simple types are supported here, see if we can support
+        // other types such as Tuple, Array, Slice, etc.
+        // See https://github.com/rust-lang/rust/issues/90703#issuecomment-1004263455
+        Some(tcx.mk_ty(match prim {
+            Bool => ty::Bool,
+            Str => ty::Str,
+            Char => ty::Char,
+            Never => ty::Never,
+            I8 => ty::Int(ty::IntTy::I8),
+            I16 => ty::Int(ty::IntTy::I16),
+            I32 => ty::Int(ty::IntTy::I32),
+            I64 => ty::Int(ty::IntTy::I64),
+            I128 => ty::Int(ty::IntTy::I128),
+            Isize => ty::Int(ty::IntTy::Isize),
+            F32 => ty::Float(ty::FloatTy::F32),
+            F64 => ty::Float(ty::FloatTy::F64),
+            U8 => ty::Uint(ty::UintTy::U8),
+            U16 => ty::Uint(ty::UintTy::U16),
+            U32 => ty::Uint(ty::UintTy::U32),
+            U64 => ty::Uint(ty::UintTy::U64),
+            U128 => ty::Uint(ty::UintTy::U128),
+            Usize => ty::Uint(ty::UintTy::Usize),
+            _ => return None,
+        }))
+    }
+
+    /// Resolve an associated item, returning its containing page's `Res`
+    /// and the fragment targeting the associated item on its page.
+    fn resolve_associated_item(
+        &mut self,
+        root_res: Res,
+        item_name: Symbol,
+        ns: Namespace,
+        module_id: DefId,
+    ) -> Option<(Res, DefId)> {
+        let tcx = self.cx.tcx;
+
+        match root_res {
+            Res::Primitive(prim) => {
+                self.resolve_primitive_associated_item(prim, ns, item_name).or_else(|| {
+                    self.primitive_type_to_ty(prim)
+                        .and_then(|ty| {
+                            resolve_associated_trait_item(ty, module_id, item_name, ns, self.cx)
+                        })
+                        .map(|item| (root_res, item.def_id))
+                })
+            }
+            Res::Def(DefKind::TyAlias, did) => {
+                // Resolve the link on the type the alias points to.
+                // FIXME: if the associated item is defined directly on the type alias,
+                // it will show up on its documentation page, we should link there instead.
+                let res = self.def_id_to_res(did)?;
+                self.resolve_associated_item(res, item_name, ns, module_id)
+            }
+            Res::Def(
+                def_kind @ (DefKind::Struct | DefKind::Union | DefKind::Enum | DefKind::ForeignTy),
+                did,
+            ) => {
+                debug!("looking for associated item named {} for item {:?}", item_name, did);
+                // Checks if item_name is a variant of the `SomeItem` enum
+                if ns == TypeNS && def_kind == DefKind::Enum {
+                    match tcx.type_of(did).kind() {
+                        ty::Adt(adt_def, _) => {
+                            for variant in adt_def.variants() {
+                                if variant.name == item_name {
+                                    return Some((root_res, variant.def_id));
+                                }
+                            }
+                        }
+                        _ => unreachable!(),
+                    }
+                }
+
+                // Checks if item_name belongs to `impl SomeItem`
+                let assoc_item = tcx
+                    .inherent_impls(did)
+                    .iter()
+                    .flat_map(|&imp| {
+                        tcx.associated_items(imp).find_by_name_and_namespace(
+                            tcx,
+                            Ident::with_dummy_span(item_name),
+                            ns,
+                            imp,
+                        )
+                    })
+                    .copied()
+                    // There should only ever be one associated item that matches from any inherent impl
+                    .next()
+                    // Check if item_name belongs to `impl SomeTrait for SomeItem`
+                    // FIXME(#74563): This gives precedence to `impl SomeItem`:
+                    // Although having both would be ambiguous, use impl version for compatibility's sake.
+                    // To handle that properly resolve() would have to support
+                    // something like [`ambi_fn`](<SomeStruct as SomeTrait>::ambi_fn)
+                    .or_else(|| {
+                        resolve_associated_trait_item(
+                            tcx.type_of(did),
+                            module_id,
+                            item_name,
+                            ns,
+                            self.cx,
+                        )
+                    });
+
+                debug!("got associated item {:?}", assoc_item);
+
+                if let Some(item) = assoc_item {
+                    return Some((root_res, item.def_id));
+                }
+
+                if ns != Namespace::ValueNS {
+                    return None;
+                }
+                debug!("looking for fields named {} for {:?}", item_name, did);
+                // FIXME: this doesn't really belong in `associated_item` (maybe `variant_field` is better?)
+                // NOTE: it's different from variant_field because it only resolves struct fields,
+                // not variant fields (2 path segments, not 3).
+                //
+                // We need to handle struct (and union) fields in this code because
+                // syntactically their paths are identical to associated item paths:
+                // `module::Type::field` and `module::Type::Assoc`.
+                //
+                // On the other hand, variant fields can't be mistaken for associated
+                // items because they look like this: `module::Type::Variant::field`.
+                //
+                // Variants themselves don't need to be handled here, even though
+                // they also look like associated items (`module::Type::Variant`),
+                // because they are real Rust syntax (unlike the intra-doc links
+                // field syntax) and are handled by the compiler's resolver.
+                let def = match tcx.type_of(did).kind() {
+                    ty::Adt(def, _) if !def.is_enum() => def,
+                    _ => return None,
+                };
+                let field =
+                    def.non_enum_variant().fields.iter().find(|item| item.name == item_name)?;
+                Some((root_res, field.did))
+            }
+            Res::Def(DefKind::Trait, did) => tcx
+                .associated_items(did)
+                .find_by_name_and_namespace(tcx, Ident::with_dummy_span(item_name), ns, did)
+                .map(|item| {
+                    let res = Res::Def(item.kind.as_def_kind(), item.def_id);
+                    (res, item.def_id)
+                }),
+            _ => None,
+        }
+    }
+}
+
+fn full_res(tcx: TyCtxt<'_>, (base, assoc_item): (Res, Option<DefId>)) -> Res {
+    assoc_item.map_or(base, |def_id| Res::from_def_id(tcx, def_id))
+}
+
+/// Look to see if a resolved item has an associated item named `item_name`.
+///
+/// Given `[std::io::Error::source]`, where `source` is unresolved, this would
+/// find `std::error::Error::source` and return
+/// `<io::Error as error::Error>::source`.
+fn resolve_associated_trait_item<'a>(
+    ty: Ty<'a>,
+    module: DefId,
+    item_name: Symbol,
+    ns: Namespace,
+    cx: &mut DocContext<'a>,
+) -> Option<ty::AssocItem> {
+    // FIXME: this should also consider blanket impls (`impl<T> X for T`). Unfortunately
+    // `get_auto_trait_and_blanket_impls` is broken because the caching behavior is wrong. In the
+    // meantime, just don't look for these blanket impls.
+
+    // Next consider explicit impls: `impl MyTrait for MyType`
+    // Give precedence to inherent impls.
+    let traits = trait_impls_for(cx, ty, module);
+    debug!("considering traits {:?}", traits);
+    let mut candidates = traits.iter().filter_map(|&(impl_, trait_)| {
+        cx.tcx
+            .associated_items(trait_)
+            .find_by_name_and_namespace(cx.tcx, Ident::with_dummy_span(item_name), ns, trait_)
+            .map(|trait_assoc| {
+                trait_assoc_to_impl_assoc_item(cx.tcx, impl_, trait_assoc.def_id)
+                    .unwrap_or(trait_assoc)
+            })
+    });
+    // FIXME(#74563): warn about ambiguity
+    debug!("the candidates were {:?}", candidates.clone().collect::<Vec<_>>());
+    candidates.next().copied()
+}
+
+/// Find the associated item in the impl `impl_id` that corresponds to the
+/// trait associated item `trait_assoc_id`.
+///
+/// This function returns `None` if no associated item was found in the impl.
+/// This can occur when the trait associated item has a default value that is
+/// not overridden in the impl.
+///
+/// This is just a wrapper around [`TyCtxt::impl_item_implementor_ids()`] and
+/// [`TyCtxt::associated_item()`] (with some helpful logging added).
+#[instrument(level = "debug", skip(tcx))]
+fn trait_assoc_to_impl_assoc_item<'tcx>(
+    tcx: TyCtxt<'tcx>,
+    impl_id: DefId,
+    trait_assoc_id: DefId,
+) -> Option<&'tcx ty::AssocItem> {
+    let trait_to_impl_assoc_map = tcx.impl_item_implementor_ids(impl_id);
+    debug!(?trait_to_impl_assoc_map);
+    let impl_assoc_id = *trait_to_impl_assoc_map.get(&trait_assoc_id)?;
+    debug!(?impl_assoc_id);
+    let impl_assoc = tcx.associated_item(impl_assoc_id);
+    debug!(?impl_assoc);
+    Some(impl_assoc)
+}
+
+/// Given a type, return all trait impls in scope in `module` for that type.
+/// Returns a set of pairs of `(impl_id, trait_id)`.
+///
+/// NOTE: this cannot be a query because more traits could be available when more crates are compiled!
+/// So it is not stable to serialize cross-crate.
+#[instrument(level = "debug", skip(cx))]
+fn trait_impls_for<'a>(
+    cx: &mut DocContext<'a>,
+    ty: Ty<'a>,
+    module: DefId,
+) -> FxHashSet<(DefId, DefId)> {
+    let tcx = cx.tcx;
+    let iter = cx.resolver_caches.traits_in_scope[&module].iter().flat_map(|trait_candidate| {
+        let trait_ = trait_candidate.def_id;
+        trace!("considering explicit impl for trait {:?}", trait_);
+
+        // Look at each trait implementation to see if it's an impl for `did`
+        tcx.find_map_relevant_impl(trait_, ty, |impl_| {
+            let trait_ref = tcx.impl_trait_ref(impl_).expect("this is not an inherent impl");
+            // Check if these are the same type.
+            let impl_type = trait_ref.self_ty();
+            trace!(
+                "comparing type {} with kind {:?} against type {:?}",
+                impl_type,
+                impl_type.kind(),
+                ty
+            );
+            // Fast path: if this is a primitive simple `==` will work
+            // NOTE: the `match` is necessary; see #92662.
+            // this allows us to ignore generics because the user input
+            // may not include the generic placeholders
+            // e.g. this allows us to match Foo (user comment) with Foo<T> (actual type)
+            let saw_impl = impl_type == ty
+                || match (impl_type.kind(), ty.kind()) {
+                    (ty::Adt(impl_def, _), ty::Adt(ty_def, _)) => {
+                        debug!("impl def_id: {:?}, ty def_id: {:?}", impl_def.did(), ty_def.did());
+                        impl_def.did() == ty_def.did()
+                    }
+                    _ => false,
+                };
+
+            if saw_impl { Some((impl_, trait_)) } else { None }
+        })
+    });
+    iter.collect()
+}
+
+/// Check for resolve collisions between a trait and its derive.
+///
+/// These are common and we should just resolve to the trait in that case.
+fn is_derive_trait_collision<T>(ns: &PerNS<Result<(Res, T), ResolutionFailure<'_>>>) -> bool {
+    matches!(
+        *ns,
+        PerNS {
+            type_ns: Ok((Res::Def(DefKind::Trait, _), _)),
+            macro_ns: Ok((Res::Def(DefKind::Macro(MacroKind::Derive), _), _)),
+            ..
+        }
+    )
+}
+
+impl<'a, 'tcx> DocVisitor for LinkCollector<'a, 'tcx> {
+    fn visit_item(&mut self, item: &Item) {
+        let parent_node =
+            item.item_id.as_def_id().and_then(|did| find_nearest_parent_module(self.cx.tcx, did));
+        if parent_node.is_some() {
+            trace!("got parent node for {:?} {:?}, id {:?}", item.type_(), item.name, item.item_id);
+        }
+
+        let inner_docs = item.inner_docs(self.cx.tcx);
+
+        if item.is_mod() && inner_docs {
+            self.mod_ids.push(item.item_id.expect_def_id());
+        }
+
+        // We want to resolve in the lexical scope of the documentation.
+        // In the presence of re-exports, this is not the same as the module of the item.
+        // Rather than merging all documentation into one, resolve it one attribute at a time
+        // so we know which module it came from.
+        for (parent_module, doc) in item.attrs.prepare_to_doc_link_resolution() {
+            if !may_have_doc_links(&doc) {
+                continue;
+            }
+            debug!("combined_docs={}", doc);
+            // NOTE: if there are links that start in one crate and end in another, this will not resolve them.
+            // This is a degenerate case and it's not supported by rustdoc.
+            let parent_node = parent_module.or(parent_node);
+            let mut tmp_links = self
+                .cx
+                .resolver_caches
+                .markdown_links
+                .take()
+                .expect("`markdown_links` are already borrowed");
+            if !tmp_links.contains_key(&doc) {
+                tmp_links.insert(doc.clone(), preprocessed_markdown_links(&doc));
+            }
+            for md_link in &tmp_links[&doc] {
+                let link = self.resolve_link(item, &doc, parent_node, md_link);
+                if let Some(link) = link {
+                    self.cx.cache.intra_doc_links.entry(item.item_id).or_default().push(link);
+                }
+            }
+            self.cx.resolver_caches.markdown_links = Some(tmp_links);
+        }
+
+        if item.is_mod() {
+            if !inner_docs {
+                self.mod_ids.push(item.item_id.expect_def_id());
+            }
+
+            self.visit_item_recur(item);
+            self.mod_ids.pop();
+        } else {
+            self.visit_item_recur(item)
+        }
+    }
+}
+
+enum PreprocessingError {
+    /// User error: `[std#x#y]` is not valid
+    MultipleAnchors,
+    Disambiguator(Range<usize>, String),
+    MalformedGenerics(MalformedGenerics, String),
+}
+
+impl PreprocessingError {
+    fn report(&self, cx: &DocContext<'_>, diag_info: DiagnosticInfo<'_>) {
+        match self {
+            PreprocessingError::MultipleAnchors => report_multiple_anchors(cx, diag_info),
+            PreprocessingError::Disambiguator(range, msg) => {
+                disambiguator_error(cx, diag_info, range.clone(), msg)
+            }
+            PreprocessingError::MalformedGenerics(err, path_str) => {
+                report_malformed_generics(cx, diag_info, *err, path_str)
+            }
+        }
+    }
+}
+
+#[derive(Clone)]
+struct PreprocessingInfo {
+    path_str: String,
+    disambiguator: Option<Disambiguator>,
+    extra_fragment: Option<String>,
+    link_text: String,
+}
+
+// Not a typedef to avoid leaking several private structures from this module.
+pub(crate) struct PreprocessedMarkdownLink(
+    Result<PreprocessingInfo, PreprocessingError>,
+    MarkdownLink,
+);
+
+/// Returns:
+/// - `None` if the link should be ignored.
+/// - `Some(Err)` if the link should emit an error
+/// - `Some(Ok)` if the link is valid
+///
+/// `link_buffer` is needed for lifetime reasons; it will always be overwritten and the contents ignored.
+fn preprocess_link(
+    ori_link: &MarkdownLink,
+) -> Option<Result<PreprocessingInfo, PreprocessingError>> {
+    // [] is mostly likely not supposed to be a link
+    if ori_link.link.is_empty() {
+        return None;
+    }
+
+    // Bail early for real links.
+    if ori_link.link.contains('/') {
+        return None;
+    }
+
+    let stripped = ori_link.link.replace('`', "");
+    let mut parts = stripped.split('#');
+
+    let link = parts.next().unwrap();
+    if link.trim().is_empty() {
+        // This is an anchor to an element of the current page, nothing to do in here!
+        return None;
+    }
+    let extra_fragment = parts.next();
+    if parts.next().is_some() {
+        // A valid link can't have multiple #'s
+        return Some(Err(PreprocessingError::MultipleAnchors));
+    }
+
+    // Parse and strip the disambiguator from the link, if present.
+    let (disambiguator, path_str, link_text) = match Disambiguator::from_str(link) {
+        Ok(Some((d, path, link_text))) => (Some(d), path.trim(), link_text.trim()),
+        Ok(None) => (None, link.trim(), link.trim()),
+        Err((err_msg, relative_range)) => {
+            // Only report error if we would not have ignored this link. See issue #83859.
+            if !should_ignore_link_with_disambiguators(link) {
+                let no_backticks_range = range_between_backticks(ori_link);
+                let disambiguator_range = (no_backticks_range.start + relative_range.start)
+                    ..(no_backticks_range.start + relative_range.end);
+                return Some(Err(PreprocessingError::Disambiguator(disambiguator_range, err_msg)));
+            } else {
+                return None;
+            }
+        }
+    };
+
+    if should_ignore_link(path_str) {
+        return None;
+    }
+
+    // Strip generics from the path.
+    let path_str = if path_str.contains(['<', '>'].as_slice()) {
+        match strip_generics_from_path(path_str) {
+            Ok(path) => path,
+            Err(err) => {
+                debug!("link has malformed generics: {}", path_str);
+                return Some(Err(PreprocessingError::MalformedGenerics(err, path_str.to_owned())));
+            }
+        }
+    } else {
+        path_str.to_owned()
+    };
+
+    // Sanity check to make sure we don't have any angle brackets after stripping generics.
+    assert!(!path_str.contains(['<', '>'].as_slice()));
+
+    // The link is not an intra-doc link if it still contains spaces after stripping generics.
+    if path_str.contains(' ') {
+        return None;
+    }
+
+    Some(Ok(PreprocessingInfo {
+        path_str,
+        disambiguator,
+        extra_fragment: extra_fragment.map(|frag| frag.to_owned()),
+        link_text: link_text.to_owned(),
+    }))
+}
+
+fn preprocessed_markdown_links(s: &str) -> Vec<PreprocessedMarkdownLink> {
+    markdown_links(s, |link| {
+        preprocess_link(&link).map(|pp_link| PreprocessedMarkdownLink(pp_link, link))
+    })
+}
+
+impl LinkCollector<'_, '_> {
+    /// This is the entry point for resolving an intra-doc link.
+    ///
+    /// FIXME(jynelson): this is way too many arguments
+    fn resolve_link(
+        &mut self,
+        item: &Item,
+        dox: &str,
+        parent_node: Option<DefId>,
+        link: &PreprocessedMarkdownLink,
+    ) -> Option<ItemLink> {
+        let PreprocessedMarkdownLink(pp_link, ori_link) = link;
+        trace!("considering link '{}'", ori_link.link);
+
+        let diag_info = DiagnosticInfo {
+            item,
+            dox,
+            ori_link: &ori_link.link,
+            link_range: ori_link.range.clone(),
+        };
+
+        let PreprocessingInfo { path_str, disambiguator, extra_fragment, link_text } =
+            pp_link.as_ref().map_err(|err| err.report(self.cx, diag_info.clone())).ok()?;
+        let disambiguator = *disambiguator;
+
+        // In order to correctly resolve intra-doc links we need to
+        // pick a base AST node to work from.  If the documentation for
+        // this module came from an inner comment (//!) then we anchor
+        // our name resolution *inside* the module.  If, on the other
+        // hand it was an outer comment (///) then we anchor the name
+        // resolution in the parent module on the basis that the names
+        // used are more likely to be intended to be parent names.  For
+        // this, we set base_node to None for inner comments since
+        // we've already pushed this node onto the resolution stack but
+        // for outer comments we explicitly try and resolve against the
+        // parent_node first.
+        let inner_docs = item.inner_docs(self.cx.tcx);
+        let base_node =
+            if item.is_mod() && inner_docs { self.mod_ids.last().copied() } else { parent_node };
+        let module_id = base_node.expect("doc link without parent module");
+
+        let (mut res, fragment) = self.resolve_with_disambiguator_cached(
+            ResolutionInfo {
+                item_id: item.item_id,
+                module_id,
+                dis: disambiguator,
+                path_str: path_str.to_owned(),
+                extra_fragment: extra_fragment.clone(),
+            },
+            diag_info.clone(), // this struct should really be Copy, but Range is not :(
+            // For reference-style links we want to report only one error so unsuccessful
+            // resolutions are cached, for other links we want to report an error every
+            // time so they are not cached.
+            matches!(ori_link.kind, LinkType::Reference | LinkType::Shortcut),
+        )?;
+
+        // Check for a primitive which might conflict with a module
+        // Report the ambiguity and require that the user specify which one they meant.
+        // FIXME: could there ever be a primitive not in the type namespace?
+        if matches!(
+            disambiguator,
+            None | Some(Disambiguator::Namespace(Namespace::TypeNS) | Disambiguator::Primitive)
+        ) && !matches!(res, Res::Primitive(_))
+        {
+            if let Some(prim) = resolve_primitive(path_str, TypeNS) {
+                // `prim@char`
+                if matches!(disambiguator, Some(Disambiguator::Primitive)) {
+                    res = prim;
+                } else {
+                    // `[char]` when a `char` module is in scope
+                    let candidates = vec![res, prim];
+                    ambiguity_error(self.cx, diag_info, path_str, candidates);
+                    return None;
+                }
+            }
+        }
+
+        match res {
+            Res::Primitive(prim) => {
+                if let Some(UrlFragment::Item(id)) = fragment {
+                    // We're actually resolving an associated item of a primitive, so we need to
+                    // verify the disambiguator (if any) matches the type of the associated item.
+                    // This case should really follow the same flow as the `Res::Def` branch below,
+                    // but attempting to add a call to `clean::register_res` causes an ICE. @jyn514
+                    // thinks `register_res` is only needed for cross-crate re-exports, but Rust
+                    // doesn't allow statements like `use str::trim;`, making this a (hopefully)
+                    // valid omission. See https://github.com/rust-lang/rust/pull/80660#discussion_r551585677
+                    // for discussion on the matter.
+                    let kind = self.cx.tcx.def_kind(id);
+                    self.verify_disambiguator(
+                        path_str,
+                        ori_link,
+                        kind,
+                        id,
+                        disambiguator,
+                        item,
+                        &diag_info,
+                    )?;
+
+                    // FIXME: it would be nice to check that the feature gate was enabled in the original crate, not just ignore it altogether.
+                    // However I'm not sure how to check that across crates.
+                    if prim == PrimitiveType::RawPointer
+                        && item.item_id.is_local()
+                        && !self.cx.tcx.features().intra_doc_pointers
+                    {
+                        self.report_rawptr_assoc_feature_gate(dox, ori_link, item);
+                    }
+                } else {
+                    match disambiguator {
+                        Some(Disambiguator::Primitive | Disambiguator::Namespace(_)) | None => {}
+                        Some(other) => {
+                            self.report_disambiguator_mismatch(
+                                path_str, ori_link, other, res, &diag_info,
+                            );
+                            return None;
+                        }
+                    }
+                }
+
+                Some(ItemLink {
+                    link: ori_link.link.clone(),
+                    link_text: link_text.clone(),
+                    did: res.def_id(self.cx.tcx),
+                    fragment,
+                })
+            }
+            Res::Def(kind, id) => {
+                let (kind_for_dis, id_for_dis) = if let Some(UrlFragment::Item(id)) = fragment {
+                    (self.cx.tcx.def_kind(id), id)
+                } else {
+                    (kind, id)
+                };
+                self.verify_disambiguator(
+                    path_str,
+                    ori_link,
+                    kind_for_dis,
+                    id_for_dis,
+                    disambiguator,
+                    item,
+                    &diag_info,
+                )?;
+                let id = clean::register_res(self.cx, rustc_hir::def::Res::Def(kind, id));
+                Some(ItemLink {
+                    link: ori_link.link.clone(),
+                    link_text: link_text.clone(),
+                    did: id,
+                    fragment,
+                })
+            }
+        }
+    }
+
+    fn verify_disambiguator(
+        &self,
+        path_str: &str,
+        ori_link: &MarkdownLink,
+        kind: DefKind,
+        id: DefId,
+        disambiguator: Option<Disambiguator>,
+        item: &Item,
+        diag_info: &DiagnosticInfo<'_>,
+    ) -> Option<()> {
+        debug!("intra-doc link to {} resolved to {:?}", path_str, (kind, id));
+
+        // Disallow e.g. linking to enums with `struct@`
+        debug!("saw kind {:?} with disambiguator {:?}", kind, disambiguator);
+        match (kind, disambiguator) {
+                | (DefKind::Const | DefKind::ConstParam | DefKind::AssocConst | DefKind::AnonConst, Some(Disambiguator::Kind(DefKind::Const)))
+                // NOTE: this allows 'method' to mean both normal functions and associated functions
+                // This can't cause ambiguity because both are in the same namespace.
+                | (DefKind::Fn | DefKind::AssocFn, Some(Disambiguator::Kind(DefKind::Fn)))
+                // These are namespaces; allow anything in the namespace to match
+                | (_, Some(Disambiguator::Namespace(_)))
+                // If no disambiguator given, allow anything
+                | (_, None)
+                // All of these are valid, so do nothing
+                => {}
+                (actual, Some(Disambiguator::Kind(expected))) if actual == expected => {}
+                (_, Some(specified @ Disambiguator::Kind(_) | specified @ Disambiguator::Primitive)) => {
+                    self.report_disambiguator_mismatch(path_str,ori_link,specified, Res::Def(kind, id),diag_info);
+                    return None;
+                }
+            }
+
+        // item can be non-local e.g. when using #[doc(primitive = "pointer")]
+        if let Some((src_id, dst_id)) = id
+            .as_local()
+            // The `expect_def_id()` should be okay because `local_def_id_to_hir_id`
+            // would presumably panic if a fake `DefIndex` were passed.
+            .and_then(|dst_id| {
+                item.item_id.expect_def_id().as_local().map(|src_id| (src_id, dst_id))
+            })
+        {
+            if self.cx.tcx.privacy_access_levels(()).is_exported(src_id)
+                && !self.cx.tcx.privacy_access_levels(()).is_exported(dst_id)
+            {
+                privacy_error(self.cx, diag_info, path_str);
+            }
+        }
+
+        Some(())
+    }
+
+    fn report_disambiguator_mismatch(
+        &self,
+        path_str: &str,
+        ori_link: &MarkdownLink,
+        specified: Disambiguator,
+        resolved: Res,
+        diag_info: &DiagnosticInfo<'_>,
+    ) {
+        // The resolved item did not match the disambiguator; give a better error than 'not found'
+        let msg = format!("incompatible link kind for `{}`", path_str);
+        let callback = |diag: &mut Diagnostic, sp: Option<rustc_span::Span>| {
+            let note = format!(
+                "this link resolved to {} {}, which is not {} {}",
+                resolved.article(),
+                resolved.descr(),
+                specified.article(),
+                specified.descr(),
+            );
+            if let Some(sp) = sp {
+                diag.span_label(sp, &note);
+            } else {
+                diag.note(&note);
+            }
+            suggest_disambiguator(resolved, diag, path_str, &ori_link.link, sp);
+        };
+        report_diagnostic(self.cx.tcx, BROKEN_INTRA_DOC_LINKS, &msg, diag_info, callback);
+    }
+
+    fn report_rawptr_assoc_feature_gate(&self, dox: &str, ori_link: &MarkdownLink, item: &Item) {
+        let span =
+            super::source_span_for_markdown_range(self.cx.tcx, dox, &ori_link.range, &item.attrs)
+                .unwrap_or_else(|| item.attr_span(self.cx.tcx));
+        rustc_session::parse::feature_err(
+            &self.cx.tcx.sess.parse_sess,
+            sym::intra_doc_pointers,
+            span,
+            "linking to associated items of raw pointers is experimental",
+        )
+        .note("rustdoc does not allow disambiguating between `*const` and `*mut`, and pointers are unstable until it does")
+        .emit();
+    }
+
+    fn resolve_with_disambiguator_cached(
+        &mut self,
+        key: ResolutionInfo,
+        diag: DiagnosticInfo<'_>,
+        // If errors are cached then they are only reported on first ocurrence
+        // which we want in some cases but not in others.
+        cache_errors: bool,
+    ) -> Option<(Res, Option<UrlFragment>)> {
+        if let Some(res) = self.visited_links.get(&key) {
+            if res.is_some() || cache_errors {
+                return res.clone();
+            }
+        }
+
+        let res = self.resolve_with_disambiguator(&key, diag.clone()).and_then(|(res, def_id)| {
+            let fragment = match (&key.extra_fragment, def_id) {
+                (Some(_), Some(def_id)) => {
+                    report_anchor_conflict(self.cx, diag, def_id);
+                    return None;
+                }
+                (Some(u_frag), None) => Some(UrlFragment::UserWritten(u_frag.clone())),
+                (None, Some(def_id)) => Some(UrlFragment::Item(def_id)),
+                (None, None) => None,
+            };
+            Some((res, fragment))
+        });
+
+        if res.is_some() || cache_errors {
+            self.visited_links.insert(key, res.clone());
+        }
+        res
+    }
+
+    /// After parsing the disambiguator, resolve the main part of the link.
+    // FIXME(jynelson): wow this is just so much
+    fn resolve_with_disambiguator(
+        &mut self,
+        key: &ResolutionInfo,
+        diag: DiagnosticInfo<'_>,
+    ) -> Option<(Res, Option<DefId>)> {
+        let disambiguator = key.dis;
+        let path_str = &key.path_str;
+        let item_id = key.item_id;
+        let base_node = key.module_id;
+
+        match disambiguator.map(Disambiguator::ns) {
+            Some(expected_ns) => {
+                match self.resolve(path_str, expected_ns, item_id, base_node) {
+                    Ok(res) => Some(res),
+                    Err(err) => {
+                        // We only looked in one namespace. Try to give a better error if possible.
+                        // FIXME: really it should be `resolution_failure` that does this, not `resolve_with_disambiguator`.
+                        // See https://github.com/rust-lang/rust/pull/76955#discussion_r493953382 for a good approach.
+                        let mut err = ResolutionFailure::NotResolved(err);
+                        for other_ns in [TypeNS, ValueNS, MacroNS] {
+                            if other_ns != expected_ns {
+                                if let Ok(res) =
+                                    self.resolve(path_str, other_ns, item_id, base_node)
+                                {
+                                    err = ResolutionFailure::WrongNamespace {
+                                        res: full_res(self.cx.tcx, res),
+                                        expected_ns,
+                                    };
+                                    break;
+                                }
+                            }
+                        }
+                        resolution_failure(self, diag, path_str, disambiguator, smallvec![err])
+                    }
+                }
+            }
+            None => {
+                // Try everything!
+                let mut candidate = |ns| {
+                    self.resolve(path_str, ns, item_id, base_node)
+                        .map_err(ResolutionFailure::NotResolved)
+                };
+
+                let candidates = PerNS {
+                    macro_ns: candidate(MacroNS),
+                    type_ns: candidate(TypeNS),
+                    value_ns: candidate(ValueNS).and_then(|(res, def_id)| {
+                        match res {
+                            // Constructors are picked up in the type namespace.
+                            Res::Def(DefKind::Ctor(..), _) => {
+                                Err(ResolutionFailure::WrongNamespace { res, expected_ns: TypeNS })
+                            }
+                            _ => Ok((res, def_id)),
+                        }
+                    }),
+                };
+
+                let len = candidates.iter().filter(|res| res.is_ok()).count();
+
+                if len == 0 {
+                    return resolution_failure(
+                        self,
+                        diag,
+                        path_str,
+                        disambiguator,
+                        candidates.into_iter().filter_map(|res| res.err()).collect(),
+                    );
+                }
+
+                if len == 1 {
+                    Some(candidates.into_iter().find_map(|res| res.ok()).unwrap())
+                } else if len == 2 && is_derive_trait_collision(&candidates) {
+                    Some(candidates.type_ns.unwrap())
+                } else {
+                    let ignore_macro = is_derive_trait_collision(&candidates);
+                    // If we're reporting an ambiguity, don't mention the namespaces that failed
+                    let mut candidates =
+                        candidates.map(|candidate| candidate.ok().map(|(res, _)| res));
+                    if ignore_macro {
+                        candidates.macro_ns = None;
+                    }
+                    ambiguity_error(self.cx, diag, path_str, candidates.present_items().collect());
+                    None
+                }
+            }
+        }
+    }
+}
+
+/// Get the section of a link between the backticks,
+/// or the whole link if there aren't any backticks.
+///
+/// For example:
+///
+/// ```text
+/// [`Foo`]
+///   ^^^
+/// ```
+fn range_between_backticks(ori_link: &MarkdownLink) -> Range<usize> {
+    let after_first_backtick_group = ori_link.link.bytes().position(|b| b != b'`').unwrap_or(0);
+    let before_second_backtick_group = ori_link
+        .link
+        .bytes()
+        .skip(after_first_backtick_group)
+        .position(|b| b == b'`')
+        .unwrap_or(ori_link.link.len());
+    (ori_link.range.start + after_first_backtick_group)
+        ..(ori_link.range.start + before_second_backtick_group)
+}
+
+/// Returns true if we should ignore `link` due to it being unlikely
+/// that it is an intra-doc link. `link` should still have disambiguators
+/// if there were any.
+///
+/// The difference between this and [`should_ignore_link()`] is that this
+/// check should only be used on links that still have disambiguators.
+fn should_ignore_link_with_disambiguators(link: &str) -> bool {
+    link.contains(|ch: char| !(ch.is_alphanumeric() || ":_<>, !*&;@()".contains(ch)))
+}
+
+/// Returns true if we should ignore `path_str` due to it being unlikely
+/// that it is an intra-doc link.
+fn should_ignore_link(path_str: &str) -> bool {
+    path_str.contains(|ch: char| !(ch.is_alphanumeric() || ":_<>, !*&;".contains(ch)))
+}
+
+#[derive(Copy, Clone, Debug, PartialEq, Eq, Hash)]
+/// Disambiguators for a link.
+enum Disambiguator {
+    /// `prim@`
+    ///
+    /// This is buggy, see <https://github.com/rust-lang/rust/pull/77875#discussion_r503583103>
+    Primitive,
+    /// `struct@` or `f()`
+    Kind(DefKind),
+    /// `type@`
+    Namespace(Namespace),
+}
+
+impl Disambiguator {
+    /// Given a link, parse and return `(disambiguator, path_str, link_text)`.
+    ///
+    /// This returns `Ok(Some(...))` if a disambiguator was found,
+    /// `Ok(None)` if no disambiguator was found, or `Err(...)`
+    /// if there was a problem with the disambiguator.
+    fn from_str(link: &str) -> Result<Option<(Self, &str, &str)>, (String, Range<usize>)> {
+        use Disambiguator::{Kind, Namespace as NS, Primitive};
+
+        if let Some(idx) = link.find('@') {
+            let (prefix, rest) = link.split_at(idx);
+            let d = match prefix {
+                "struct" => Kind(DefKind::Struct),
+                "enum" => Kind(DefKind::Enum),
+                "trait" => Kind(DefKind::Trait),
+                "union" => Kind(DefKind::Union),
+                "module" | "mod" => Kind(DefKind::Mod),
+                "const" | "constant" => Kind(DefKind::Const),
+                "static" => Kind(DefKind::Static(Mutability::Not)),
+                "function" | "fn" | "method" => Kind(DefKind::Fn),
+                "derive" => Kind(DefKind::Macro(MacroKind::Derive)),
+                "type" => NS(Namespace::TypeNS),
+                "value" => NS(Namespace::ValueNS),
+                "macro" => NS(Namespace::MacroNS),
+                "prim" | "primitive" => Primitive,
+                _ => return Err((format!("unknown disambiguator `{}`", prefix), 0..idx)),
+            };
+            Ok(Some((d, &rest[1..], &rest[1..])))
+        } else {
+            let suffixes = [
+                ("!()", DefKind::Macro(MacroKind::Bang)),
+                ("!{}", DefKind::Macro(MacroKind::Bang)),
+                ("![]", DefKind::Macro(MacroKind::Bang)),
+                ("()", DefKind::Fn),
+                ("!", DefKind::Macro(MacroKind::Bang)),
+            ];
+            for (suffix, kind) in suffixes {
+                if let Some(path_str) = link.strip_suffix(suffix) {
+                    // Avoid turning `!` or `()` into an empty string
+                    if !path_str.is_empty() {
+                        return Ok(Some((Kind(kind), path_str, link)));
+                    }
+                }
+            }
+            Ok(None)
+        }
+    }
+
+    fn ns(self) -> Namespace {
+        match self {
+            Self::Namespace(n) => n,
+            Self::Kind(k) => {
+                k.ns().expect("only DefKinds with a valid namespace can be disambiguators")
+            }
+            Self::Primitive => TypeNS,
+        }
+    }
+
+    fn article(self) -> &'static str {
+        match self {
+            Self::Namespace(_) => panic!("article() doesn't make sense for namespaces"),
+            Self::Kind(k) => k.article(),
+            Self::Primitive => "a",
+        }
+    }
+
+    fn descr(self) -> &'static str {
+        match self {
+            Self::Namespace(n) => n.descr(),
+            // HACK(jynelson): the source of `DefKind::descr` only uses the DefId for
+            // printing "module" vs "crate" so using the wrong ID is not a huge problem
+            Self::Kind(k) => k.descr(CRATE_DEF_ID.to_def_id()),
+            Self::Primitive => "builtin type",
+        }
+    }
+}
+
+/// A suggestion to show in a diagnostic.
+enum Suggestion {
+    /// `struct@`
+    Prefix(&'static str),
+    /// `f()`
+    Function,
+    /// `m!`
+    Macro,
+    /// `foo` without any disambiguator
+    RemoveDisambiguator,
+}
+
+impl Suggestion {
+    fn descr(&self) -> Cow<'static, str> {
+        match self {
+            Self::Prefix(x) => format!("prefix with `{}@`", x).into(),
+            Self::Function => "add parentheses".into(),
+            Self::Macro => "add an exclamation mark".into(),
+            Self::RemoveDisambiguator => "remove the disambiguator".into(),
+        }
+    }
+
+    fn as_help(&self, path_str: &str) -> String {
+        // FIXME: if this is an implied shortcut link, it's bad style to suggest `@`
+        match self {
+            Self::Prefix(prefix) => format!("{}@{}", prefix, path_str),
+            Self::Function => format!("{}()", path_str),
+            Self::Macro => format!("{}!", path_str),
+            Self::RemoveDisambiguator => path_str.into(),
+        }
+    }
+
+    fn as_help_span(
+        &self,
+        path_str: &str,
+        ori_link: &str,
+        sp: rustc_span::Span,
+    ) -> Vec<(rustc_span::Span, String)> {
+        let inner_sp = match ori_link.find('(') {
+            Some(index) => sp.with_hi(sp.lo() + BytePos(index as _)),
+            None => sp,
+        };
+        let inner_sp = match ori_link.find('!') {
+            Some(index) => inner_sp.with_hi(inner_sp.lo() + BytePos(index as _)),
+            None => inner_sp,
+        };
+        let inner_sp = match ori_link.find('@') {
+            Some(index) => inner_sp.with_lo(inner_sp.lo() + BytePos(index as u32 + 1)),
+            None => inner_sp,
+        };
+        match self {
+            Self::Prefix(prefix) => {
+                // FIXME: if this is an implied shortcut link, it's bad style to suggest `@`
+                let mut sugg = vec![(sp.with_hi(inner_sp.lo()), format!("{}@", prefix))];
+                if sp.hi() != inner_sp.hi() {
+                    sugg.push((inner_sp.shrink_to_hi().with_hi(sp.hi()), String::new()));
+                }
+                sugg
+            }
+            Self::Function => {
+                let mut sugg = vec![(inner_sp.shrink_to_hi().with_hi(sp.hi()), "()".to_string())];
+                if sp.lo() != inner_sp.lo() {
+                    sugg.push((inner_sp.shrink_to_lo().with_lo(sp.lo()), String::new()));
+                }
+                sugg
+            }
+            Self::Macro => {
+                let mut sugg = vec![(inner_sp.shrink_to_hi(), "!".to_string())];
+                if sp.lo() != inner_sp.lo() {
+                    sugg.push((inner_sp.shrink_to_lo().with_lo(sp.lo()), String::new()));
+                }
+                sugg
+            }
+            Self::RemoveDisambiguator => vec![(sp, path_str.into())],
+        }
+    }
+}
+
+/// Reports a diagnostic for an intra-doc link.
+///
+/// If no link range is provided, or the source span of the link cannot be determined, the span of
+/// the entire documentation block is used for the lint. If a range is provided but the span
+/// calculation fails, a note is added to the diagnostic pointing to the link in the markdown.
+///
+/// The `decorate` callback is invoked in all cases to allow further customization of the
+/// diagnostic before emission. If the span of the link was able to be determined, the second
+/// parameter of the callback will contain it, and the primary span of the diagnostic will be set
+/// to it.
+fn report_diagnostic(
+    tcx: TyCtxt<'_>,
+    lint: &'static Lint,
+    msg: &str,
+    DiagnosticInfo { item, ori_link: _, dox, link_range }: &DiagnosticInfo<'_>,
+    decorate: impl FnOnce(&mut Diagnostic, Option<rustc_span::Span>),
+) {
+    let Some(hir_id) = DocContext::as_local_hir_id(tcx, item.item_id)
+    else {
+        // If non-local, no need to check anything.
+        info!("ignoring warning from parent crate: {}", msg);
+        return;
+    };
+
+    let sp = item.attr_span(tcx);
+
+    tcx.struct_span_lint_hir(lint, hir_id, sp, |lint| {
+        let mut diag = lint.build(msg);
+
+        let span =
+            super::source_span_for_markdown_range(tcx, dox, link_range, &item.attrs).map(|sp| {
+                if dox.as_bytes().get(link_range.start) == Some(&b'`')
+                    && dox.as_bytes().get(link_range.end - 1) == Some(&b'`')
+                {
+                    sp.with_lo(sp.lo() + BytePos(1)).with_hi(sp.hi() - BytePos(1))
+                } else {
+                    sp
+                }
+            });
+
+        if let Some(sp) = span {
+            diag.set_span(sp);
+        } else {
+            // blah blah blah\nblah\nblah [blah] blah blah\nblah blah
+            //                       ^     ~~~~
+            //                       |     link_range
+            //                       last_new_line_offset
+            let last_new_line_offset = dox[..link_range.start].rfind('\n').map_or(0, |n| n + 1);
+            let line = dox[last_new_line_offset..].lines().next().unwrap_or("");
+
+            // Print the line containing the `link_range` and manually mark it with '^'s.
+            diag.note(&format!(
+                "the link appears in this line:\n\n{line}\n\
+                     {indicator: <before$}{indicator:^<found$}",
+                line = line,
+                indicator = "",
+                before = link_range.start - last_new_line_offset,
+                found = link_range.len(),
+            ));
+        }
+
+        decorate(&mut diag, span);
+
+        diag.emit();
+    });
+}
+
+/// Reports a link that failed to resolve.
+///
+/// This also tries to resolve any intermediate path segments that weren't
+/// handled earlier. For example, if passed `Item::Crate(std)` and `path_str`
+/// `std::io::Error::x`, this will resolve `std::io::Error`.
+fn resolution_failure(
+    collector: &mut LinkCollector<'_, '_>,
+    diag_info: DiagnosticInfo<'_>,
+    path_str: &str,
+    disambiguator: Option<Disambiguator>,
+    kinds: SmallVec<[ResolutionFailure<'_>; 3]>,
+) -> Option<(Res, Option<DefId>)> {
+    let tcx = collector.cx.tcx;
+    let mut recovered_res = None;
+    report_diagnostic(
+        tcx,
+        BROKEN_INTRA_DOC_LINKS,
+        &format!("unresolved link to `{}`", path_str),
+        &diag_info,
+        |diag, sp| {
+            let item = |res: Res| format!("the {} `{}`", res.descr(), res.name(tcx),);
+            let assoc_item_not_allowed = |res: Res| {
+                let name = res.name(tcx);
+                format!(
+                    "`{}` is {} {}, not a module or type, and cannot have associated items",
+                    name,
+                    res.article(),
+                    res.descr()
+                )
+            };
+            // ignore duplicates
+            let mut variants_seen = SmallVec::<[_; 3]>::new();
+            for mut failure in kinds {
+                let variant = std::mem::discriminant(&failure);
+                if variants_seen.contains(&variant) {
+                    continue;
+                }
+                variants_seen.push(variant);
+
+                if let ResolutionFailure::NotResolved(UnresolvedPath {
+                    item_id,
+                    module_id,
+                    partial_res,
+                    unresolved,
+                }) = &mut failure
+                {
+                    use DefKind::*;
+
+                    let item_id = *item_id;
+                    let module_id = *module_id;
+                    // FIXME(jynelson): this might conflict with my `Self` fix in #76467
+                    // FIXME: maybe use itertools `collect_tuple` instead?
+                    fn split(path: &str) -> Option<(&str, &str)> {
+                        let mut splitter = path.rsplitn(2, "::");
+                        splitter.next().and_then(|right| splitter.next().map(|left| (left, right)))
+                    }
+
+                    // Check if _any_ parent of the path gets resolved.
+                    // If so, report it and say the first which failed; if not, say the first path segment didn't resolve.
+                    let mut name = path_str;
+                    'outer: loop {
+                        let Some((start, end)) = split(name) else {
+                            // avoid bug that marked [Quux::Z] as missing Z, not Quux
+                            if partial_res.is_none() {
+                                *unresolved = name.into();
+                            }
+                            break;
+                        };
+                        name = start;
+                        for ns in [TypeNS, ValueNS, MacroNS] {
+                            if let Ok(res) = collector.resolve(start, ns, item_id, module_id) {
+                                debug!("found partial_res={:?}", res);
+                                *partial_res = Some(full_res(collector.cx.tcx, res));
+                                *unresolved = end.into();
+                                break 'outer;
+                            }
+                        }
+                        *unresolved = end.into();
+                    }
+
+                    let last_found_module = match *partial_res {
+                        Some(Res::Def(DefKind::Mod, id)) => Some(id),
+                        None => Some(module_id),
+                        _ => None,
+                    };
+                    // See if this was a module: `[path]` or `[std::io::nope]`
+                    if let Some(module) = last_found_module {
+                        let note = if partial_res.is_some() {
+                            // Part of the link resolved; e.g. `std::io::nonexistent`
+                            let module_name = tcx.item_name(module);
+                            format!("no item named `{}` in module `{}`", unresolved, module_name)
+                        } else {
+                            // None of the link resolved; e.g. `Notimported`
+                            format!("no item named `{}` in scope", unresolved)
+                        };
+                        if let Some(span) = sp {
+                            diag.span_label(span, &note);
+                        } else {
+                            diag.note(&note);
+                        }
+
+                        if !path_str.contains("::") {
+                            if disambiguator.map_or(true, |d| d.ns() == MacroNS)
+                                && let Some(&res) = collector.cx.resolver_caches.all_macro_rules
+                                                             .get(&Symbol::intern(path_str))
+                            {
+                                diag.note(format!(
+                                    "`macro_rules` named `{path_str}` exists in this crate, \
+                                     but it is not in scope at this link's location"
+                                ));
+                                recovered_res = res.try_into().ok().map(|res| (res, None));
+                            } else {
+                                // If the link has `::` in it, assume it was meant to be an
+                                // intra-doc link. Otherwise, the `[]` might be unrelated.
+                                diag.help("to escape `[` and `]` characters, \
+                                           add '\\' before them like `\\[` or `\\]`");
+                            }
+                        }
+
+                        continue;
+                    }
+
+                    // Otherwise, it must be an associated item or variant
+                    let res = partial_res.expect("None case was handled by `last_found_module`");
+                    let name = res.name(tcx);
+                    let kind = match res {
+                        Res::Def(kind, _) => Some(kind),
+                        Res::Primitive(_) => None,
+                    };
+                    let path_description = if let Some(kind) = kind {
+                        match kind {
+                            Mod | ForeignMod => "inner item",
+                            Struct => "field or associated item",
+                            Enum | Union => "variant or associated item",
+                            Variant
+                            | Field
+                            | Closure
+                            | Generator
+                            | AssocTy
+                            | AssocConst
+                            | AssocFn
+                            | Fn
+                            | Macro(_)
+                            | Const
+                            | ConstParam
+                            | ExternCrate
+                            | Use
+                            | LifetimeParam
+                            | Ctor(_, _)
+                            | AnonConst
+                            | InlineConst => {
+                                let note = assoc_item_not_allowed(res);
+                                if let Some(span) = sp {
+                                    diag.span_label(span, &note);
+                                } else {
+                                    diag.note(&note);
+                                }
+                                return;
+                            }
+                            Trait | TyAlias | ForeignTy | OpaqueTy | TraitAlias | TyParam
+                            | Static(_) => "associated item",
+                            Impl | GlobalAsm => unreachable!("not a path"),
+                        }
+                    } else {
+                        "associated item"
+                    };
+                    let note = format!(
+                        "the {} `{}` has no {} named `{}`",
+                        res.descr(),
+                        name,
+                        disambiguator.map_or(path_description, |d| d.descr()),
+                        unresolved,
+                    );
+                    if let Some(span) = sp {
+                        diag.span_label(span, &note);
+                    } else {
+                        diag.note(&note);
+                    }
+
+                    continue;
+                }
+                let note = match failure {
+                    ResolutionFailure::NotResolved { .. } => unreachable!("handled above"),
+                    ResolutionFailure::WrongNamespace { res, expected_ns } => {
+                        suggest_disambiguator(res, diag, path_str, diag_info.ori_link, sp);
+
+                        format!(
+                            "this link resolves to {}, which is not in the {} namespace",
+                            item(res),
+                            expected_ns.descr()
+                        )
+                    }
+                };
+                if let Some(span) = sp {
+                    diag.span_label(span, &note);
+                } else {
+                    diag.note(&note);
+                }
+            }
+        },
+    );
+
+    recovered_res
+}
+
+fn report_multiple_anchors(cx: &DocContext<'_>, diag_info: DiagnosticInfo<'_>) {
+    let msg = format!("`{}` contains multiple anchors", diag_info.ori_link);
+    anchor_failure(cx, diag_info, &msg, 1)
+}
+
+fn report_anchor_conflict(cx: &DocContext<'_>, diag_info: DiagnosticInfo<'_>, def_id: DefId) {
+    let (link, kind) = (diag_info.ori_link, Res::from_def_id(cx.tcx, def_id).descr());
+    let msg = format!("`{link}` contains an anchor, but links to {kind}s are already anchored");
+    anchor_failure(cx, diag_info, &msg, 0)
+}
+
+/// Report an anchor failure.
+fn anchor_failure(
+    cx: &DocContext<'_>,
+    diag_info: DiagnosticInfo<'_>,
+    msg: &str,
+    anchor_idx: usize,
+) {
+    report_diagnostic(cx.tcx, BROKEN_INTRA_DOC_LINKS, msg, &diag_info, |diag, sp| {
+        if let Some(mut sp) = sp {
+            if let Some((fragment_offset, _)) =
+                diag_info.ori_link.char_indices().filter(|(_, x)| *x == '#').nth(anchor_idx)
+            {
+                sp = sp.with_lo(sp.lo() + BytePos(fragment_offset as _));
+            }
+            diag.span_label(sp, "invalid anchor");
+        }
+    });
+}
+
+/// Report an error in the link disambiguator.
+fn disambiguator_error(
+    cx: &DocContext<'_>,
+    mut diag_info: DiagnosticInfo<'_>,
+    disambiguator_range: Range<usize>,
+    msg: &str,
+) {
+    diag_info.link_range = disambiguator_range;
+    report_diagnostic(cx.tcx, BROKEN_INTRA_DOC_LINKS, msg, &diag_info, |diag, _sp| {
+        let msg = format!(
+            "see {}/rustdoc/linking-to-items-by-name.html#namespaces-and-disambiguators for more info about disambiguators",
+            crate::DOC_RUST_LANG_ORG_CHANNEL
+        );
+        diag.note(&msg);
+    });
+}
+
+fn report_malformed_generics(
+    cx: &DocContext<'_>,
+    diag_info: DiagnosticInfo<'_>,
+    err: MalformedGenerics,
+    path_str: &str,
+) {
+    report_diagnostic(
+        cx.tcx,
+        BROKEN_INTRA_DOC_LINKS,
+        &format!("unresolved link to `{}`", path_str),
+        &diag_info,
+        |diag, sp| {
+            let note = match err {
+                MalformedGenerics::UnbalancedAngleBrackets => "unbalanced angle brackets",
+                MalformedGenerics::MissingType => "missing type for generic parameters",
+                MalformedGenerics::HasFullyQualifiedSyntax => {
+                    diag.note(
+                        "see https://github.com/rust-lang/rust/issues/74563 for more information",
+                    );
+                    "fully-qualified syntax is unsupported"
+                }
+                MalformedGenerics::InvalidPathSeparator => "has invalid path separator",
+                MalformedGenerics::TooManyAngleBrackets => "too many angle brackets",
+                MalformedGenerics::EmptyAngleBrackets => "empty angle brackets",
+            };
+            if let Some(span) = sp {
+                diag.span_label(span, note);
+            } else {
+                diag.note(note);
+            }
+        },
+    );
+}
+
+/// Report an ambiguity error, where there were multiple possible resolutions.
+fn ambiguity_error(
+    cx: &DocContext<'_>,
+    diag_info: DiagnosticInfo<'_>,
+    path_str: &str,
+    candidates: Vec<Res>,
+) {
+    let mut msg = format!("`{}` is ", path_str);
+
+    match candidates.as_slice() {
+        [first_def, second_def] => {
+            msg += &format!(
+                "both {} {} and {} {}",
+                first_def.article(),
+                first_def.descr(),
+                second_def.article(),
+                second_def.descr(),
+            );
+        }
+        _ => {
+            let mut candidates = candidates.iter().peekable();
+            while let Some(res) = candidates.next() {
+                if candidates.peek().is_some() {
+                    msg += &format!("{} {}, ", res.article(), res.descr());
+                } else {
+                    msg += &format!("and {} {}", res.article(), res.descr());
+                }
+            }
+        }
+    }
+
+    report_diagnostic(cx.tcx, BROKEN_INTRA_DOC_LINKS, &msg, &diag_info, |diag, sp| {
+        if let Some(sp) = sp {
+            diag.span_label(sp, "ambiguous link");
+        } else {
+            diag.note("ambiguous link");
+        }
+
+        for res in candidates {
+            suggest_disambiguator(res, diag, path_str, diag_info.ori_link, sp);
+        }
+    });
+}
+
+/// In case of an ambiguity or mismatched disambiguator, suggest the correct
+/// disambiguator.
+fn suggest_disambiguator(
+    res: Res,
+    diag: &mut Diagnostic,
+    path_str: &str,
+    ori_link: &str,
+    sp: Option<rustc_span::Span>,
+) {
+    let suggestion = res.disambiguator_suggestion();
+    let help = format!("to link to the {}, {}", res.descr(), suggestion.descr());
+
+    if let Some(sp) = sp {
+        let mut spans = suggestion.as_help_span(path_str, ori_link, sp);
+        if spans.len() > 1 {
+            diag.multipart_suggestion(&help, spans, Applicability::MaybeIncorrect);
+        } else {
+            let (sp, suggestion_text) = spans.pop().unwrap();
+            diag.span_suggestion_verbose(sp, &help, suggestion_text, Applicability::MaybeIncorrect);
+        }
+    } else {
+        diag.help(&format!("{}: {}", help, suggestion.as_help(path_str)));
+    }
+}
+
+/// Report a link from a public item to a private one.
+fn privacy_error(cx: &DocContext<'_>, diag_info: &DiagnosticInfo<'_>, path_str: &str) {
+    let sym;
+    let item_name = match diag_info.item.name {
+        Some(name) => {
+            sym = name;
+            sym.as_str()
+        }
+        None => "<unknown>",
+    };
+    let msg =
+        format!("public documentation for `{}` links to private item `{}`", item_name, path_str);
+
+    report_diagnostic(cx.tcx, PRIVATE_INTRA_DOC_LINKS, &msg, diag_info, |diag, sp| {
+        if let Some(sp) = sp {
+            diag.span_label(sp, "this item is private");
+        }
+
+        let note_msg = if cx.render_options.document_private {
+            "this link resolves only because you passed `--document-private-items`, but will break without"
+        } else {
+            "this link will resolve properly if you pass `--document-private-items`"
+        };
+        diag.note(note_msg);
+    });
+}
+
+/// Resolve a primitive type or value.
+fn resolve_primitive(path_str: &str, ns: Namespace) -> Option<Res> {
+    if ns != TypeNS {
+        return None;
+    }
+    use PrimitiveType::*;
+    let prim = match path_str {
+        "isize" => Isize,
+        "i8" => I8,
+        "i16" => I16,
+        "i32" => I32,
+        "i64" => I64,
+        "i128" => I128,
+        "usize" => Usize,
+        "u8" => U8,
+        "u16" => U16,
+        "u32" => U32,
+        "u64" => U64,
+        "u128" => U128,
+        "f32" => F32,
+        "f64" => F64,
+        "char" => Char,
+        "bool" | "true" | "false" => Bool,
+        "str" | "&str" => Str,
+        // See #80181 for why these don't have symbols associated.
+        "slice" => Slice,
+        "array" => Array,
+        "tuple" => Tuple,
+        "unit" => Unit,
+        "pointer" | "*const" | "*mut" => RawPointer,
+        "reference" | "&" | "&mut" => Reference,
+        "fn" => Fn,
+        "never" | "!" => Never,
+        _ => return None,
+    };
+    debug!("resolved primitives {:?}", prim);
+    Some(Res::Primitive(prim))
+}
+
+fn strip_generics_from_path(path_str: &str) -> Result<String, MalformedGenerics> {
+    let mut stripped_segments = vec![];
+    let mut path = path_str.chars().peekable();
+    let mut segment = Vec::new();
+
+    while let Some(chr) = path.next() {
+        match chr {
+            ':' => {
+                if path.next_if_eq(&':').is_some() {
+                    let stripped_segment =
+                        strip_generics_from_path_segment(mem::take(&mut segment))?;
+                    if !stripped_segment.is_empty() {
+                        stripped_segments.push(stripped_segment);
+                    }
+                } else {
+                    return Err(MalformedGenerics::InvalidPathSeparator);
+                }
+            }
+            '<' => {
+                segment.push(chr);
+
+                match path.next() {
+                    Some('<') => {
+                        return Err(MalformedGenerics::TooManyAngleBrackets);
+                    }
+                    Some('>') => {
+                        return Err(MalformedGenerics::EmptyAngleBrackets);
+                    }
+                    Some(chr) => {
+                        segment.push(chr);
+
+                        while let Some(chr) = path.next_if(|c| *c != '>') {
+                            segment.push(chr);
+                        }
+                    }
+                    None => break,
+                }
+            }
+            _ => segment.push(chr),
+        }
+        trace!("raw segment: {:?}", segment);
+    }
+
+    if !segment.is_empty() {
+        let stripped_segment = strip_generics_from_path_segment(segment)?;
+        if !stripped_segment.is_empty() {
+            stripped_segments.push(stripped_segment);
+        }
+    }
+
+    debug!("path_str: {:?}\nstripped segments: {:?}", path_str, &stripped_segments);
+
+    let stripped_path = stripped_segments.join("::");
+
+    if !stripped_path.is_empty() { Ok(stripped_path) } else { Err(MalformedGenerics::MissingType) }
+}
+
+fn strip_generics_from_path_segment(segment: Vec<char>) -> Result<String, MalformedGenerics> {
+    let mut stripped_segment = String::new();
+    let mut param_depth = 0;
+
+    let mut latest_generics_chunk = String::new();
+
+    for c in segment {
+        if c == '<' {
+            param_depth += 1;
+            latest_generics_chunk.clear();
+        } else if c == '>' {
+            param_depth -= 1;
+            if latest_generics_chunk.contains(" as ") {
+                // The segment tries to use fully-qualified syntax, which is currently unsupported.
+                // Give a helpful error message instead of completely ignoring the angle brackets.
+                return Err(MalformedGenerics::HasFullyQualifiedSyntax);
+            }
+        } else {
+            if param_depth == 0 {
+                stripped_segment.push(c);
+            } else {
+                latest_generics_chunk.push(c);
+            }
+        }
+    }
+
+    if param_depth == 0 {
+        Ok(stripped_segment)
+    } else {
+        // The segment has unbalanced angle brackets, e.g. `Vec<T` or `Vec<T>>`
+        Err(MalformedGenerics::UnbalancedAngleBrackets)
+    }
+}
diff --git a/src/librustdoc/passes/collect_intra_doc_links/early.rs b/src/librustdoc/passes/collect_intra_doc_links/early.rs
new file mode 100644
index 000000000..38cfd7a27
--- /dev/null
+++ b/src/librustdoc/passes/collect_intra_doc_links/early.rs
@@ -0,0 +1,405 @@
+use crate::clean::Attributes;
+use crate::core::ResolverCaches;
+use crate::passes::collect_intra_doc_links::preprocessed_markdown_links;
+use crate::passes::collect_intra_doc_links::{Disambiguator, PreprocessedMarkdownLink};
+
+use rustc_ast::visit::{self, AssocCtxt, Visitor};
+use rustc_ast::{self as ast, ItemKind};
+use rustc_data_structures::fx::FxHashMap;
+use rustc_hir::def::Namespace::*;
+use rustc_hir::def::{DefKind, Namespace, Res};
+use rustc_hir::def_id::{DefId, DefIdMap, DefIdSet, CRATE_DEF_ID};
+use rustc_hir::TraitCandidate;
+use rustc_middle::ty::{DefIdTree, Visibility};
+use rustc_resolve::{ParentScope, Resolver};
+use rustc_session::config::Externs;
+use rustc_session::Session;
+use rustc_span::symbol::sym;
+use rustc_span::{Symbol, SyntaxContext};
+
+use std::collections::hash_map::Entry;
+use std::mem;
+
+pub(crate) fn early_resolve_intra_doc_links(
+    resolver: &mut Resolver<'_>,
+    sess: &Session,
+    krate: &ast::Crate,
+    externs: Externs,
+    document_private_items: bool,
+) -> ResolverCaches {
+    let parent_scope =
+        ParentScope::module(resolver.expect_module(CRATE_DEF_ID.to_def_id()), resolver);
+    let mut link_resolver = EarlyDocLinkResolver {
+        resolver,
+        sess,
+        parent_scope,
+        visited_mods: Default::default(),
+        markdown_links: Default::default(),
+        doc_link_resolutions: Default::default(),
+        traits_in_scope: Default::default(),
+        all_traits: Default::default(),
+        all_trait_impls: Default::default(),
+        all_macro_rules: Default::default(),
+        document_private_items,
+    };
+
+    // Overridden `visit_item` below doesn't apply to the crate root,
+    // so we have to visit its attributes and reexports separately.
+    link_resolver.resolve_doc_links_local(&krate.attrs);
+    link_resolver.process_module_children_or_reexports(CRATE_DEF_ID.to_def_id());
+    visit::walk_crate(&mut link_resolver, krate);
+    link_resolver.process_extern_impls();
+
+    // FIXME: somehow rustdoc is still missing crates even though we loaded all
+    // the known necessary crates. Load them all unconditionally until we find a way to fix this.
+    // DO NOT REMOVE THIS without first testing on the reproducer in
+    // https://github.com/jyn514/objr/commit/edcee7b8124abf0e4c63873e8422ff81beb11ebb
+    for (extern_name, _) in externs.iter().filter(|(_, entry)| entry.add_prelude) {
+        link_resolver.resolver.resolve_rustdoc_path(extern_name, TypeNS, parent_scope);
+    }
+
+    ResolverCaches {
+        markdown_links: Some(link_resolver.markdown_links),
+        doc_link_resolutions: link_resolver.doc_link_resolutions,
+        traits_in_scope: link_resolver.traits_in_scope,
+        all_traits: Some(link_resolver.all_traits),
+        all_trait_impls: Some(link_resolver.all_trait_impls),
+        all_macro_rules: link_resolver.all_macro_rules,
+    }
+}
+
+fn doc_attrs<'a>(attrs: impl Iterator<Item = &'a ast::Attribute>) -> Attributes {
+    Attributes::from_ast_iter(attrs.map(|attr| (attr, None)), true)
+}
+
+struct EarlyDocLinkResolver<'r, 'ra> {
+    resolver: &'r mut Resolver<'ra>,
+    sess: &'r Session,
+    parent_scope: ParentScope<'ra>,
+    visited_mods: DefIdSet,
+    markdown_links: FxHashMap<String, Vec<PreprocessedMarkdownLink>>,
+    doc_link_resolutions: FxHashMap<(Symbol, Namespace, DefId), Option<Res<ast::NodeId>>>,
+    traits_in_scope: DefIdMap<Vec<TraitCandidate>>,
+    all_traits: Vec<DefId>,
+    all_trait_impls: Vec<DefId>,
+    all_macro_rules: FxHashMap<Symbol, Res<ast::NodeId>>,
+    document_private_items: bool,
+}
+
+impl<'ra> EarlyDocLinkResolver<'_, 'ra> {
+    fn add_traits_in_scope(&mut self, def_id: DefId) {
+        // Calls to `traits_in_scope` are expensive, so try to avoid them if only possible.
+        // Keys in the `traits_in_scope` cache are always module IDs.
+        if let Entry::Vacant(entry) = self.traits_in_scope.entry(def_id) {
+            let module = self.resolver.get_nearest_non_block_module(def_id);
+            let module_id = module.def_id();
+            let entry = if module_id == def_id {
+                Some(entry)
+            } else if let Entry::Vacant(entry) = self.traits_in_scope.entry(module_id) {
+                Some(entry)
+            } else {
+                None
+            };
+            if let Some(entry) = entry {
+                entry.insert(self.resolver.traits_in_scope(
+                    None,
+                    &ParentScope::module(module, self.resolver),
+                    SyntaxContext::root(),
+                    None,
+                ));
+            }
+        }
+    }
+
+    /// Add traits in scope for links in impls collected by the `collect-intra-doc-links` pass.
+    /// That pass filters impls using type-based information, but we don't yet have such
+    /// information here, so we just conservatively calculate traits in scope for *all* modules
+    /// having impls in them.
+    fn process_extern_impls(&mut self) {
+        // Resolving links in already existing crates may trigger loading of new crates.
+        let mut start_cnum = 0;
+        loop {
+            let crates = Vec::from_iter(self.resolver.cstore().crates_untracked());
+            for &cnum in &crates[start_cnum..] {
+                let all_traits =
+                    Vec::from_iter(self.resolver.cstore().traits_in_crate_untracked(cnum));
+                let all_trait_impls =
+                    Vec::from_iter(self.resolver.cstore().trait_impls_in_crate_untracked(cnum));
+                let all_inherent_impls =
+                    Vec::from_iter(self.resolver.cstore().inherent_impls_in_crate_untracked(cnum));
+                let all_incoherent_impls = Vec::from_iter(
+                    self.resolver.cstore().incoherent_impls_in_crate_untracked(cnum),
+                );
+
+                // Querying traits in scope is expensive so we try to prune the impl and traits lists
+                // using privacy, private traits and impls from other crates are never documented in
+                // the current crate, and links in their doc comments are not resolved.
+                for &def_id in &all_traits {
+                    if self.resolver.cstore().visibility_untracked(def_id).is_public() {
+                        self.resolve_doc_links_extern_impl(def_id, false);
+                    }
+                }
+                for &(trait_def_id, impl_def_id, simplified_self_ty) in &all_trait_impls {
+                    if self.resolver.cstore().visibility_untracked(trait_def_id).is_public()
+                        && simplified_self_ty.and_then(|ty| ty.def()).map_or(true, |ty_def_id| {
+                            self.resolver.cstore().visibility_untracked(ty_def_id).is_public()
+                        })
+                    {
+                        self.resolve_doc_links_extern_impl(impl_def_id, false);
+                    }
+                }
+                for (ty_def_id, impl_def_id) in all_inherent_impls {
+                    if self.resolver.cstore().visibility_untracked(ty_def_id).is_public() {
+                        self.resolve_doc_links_extern_impl(impl_def_id, true);
+                    }
+                }
+                for impl_def_id in all_incoherent_impls {
+                    self.resolve_doc_links_extern_impl(impl_def_id, true);
+                }
+
+                self.all_traits.extend(all_traits);
+                self.all_trait_impls
+                    .extend(all_trait_impls.into_iter().map(|(_, def_id, _)| def_id));
+            }
+
+            if crates.len() > start_cnum {
+                start_cnum = crates.len();
+            } else {
+                break;
+            }
+        }
+    }
+
+    fn resolve_doc_links_extern_impl(&mut self, def_id: DefId, is_inherent: bool) {
+        self.resolve_doc_links_extern_outer_fixme(def_id, def_id);
+        let assoc_item_def_ids = Vec::from_iter(
+            self.resolver.cstore().associated_item_def_ids_untracked(def_id, self.sess),
+        );
+        for assoc_def_id in assoc_item_def_ids {
+            if !is_inherent || self.resolver.cstore().visibility_untracked(assoc_def_id).is_public()
+            {
+                self.resolve_doc_links_extern_outer_fixme(assoc_def_id, def_id);
+            }
+        }
+    }
+
+    // FIXME: replace all uses with `resolve_doc_links_extern_outer` to actually resolve links, not
+    // just add traits in scope. This may be expensive and require benchmarking and optimization.
+    fn resolve_doc_links_extern_outer_fixme(&mut self, def_id: DefId, scope_id: DefId) {
+        if !self.resolver.cstore().may_have_doc_links_untracked(def_id) {
+            return;
+        }
+        if let Some(parent_id) = self.resolver.opt_parent(scope_id) {
+            self.add_traits_in_scope(parent_id);
+        }
+    }
+
+    fn resolve_doc_links_extern_outer(&mut self, def_id: DefId, scope_id: DefId) {
+        if !self.resolver.cstore().may_have_doc_links_untracked(def_id) {
+            return;
+        }
+        let attrs = Vec::from_iter(self.resolver.cstore().item_attrs_untracked(def_id, self.sess));
+        let parent_scope = ParentScope::module(
+            self.resolver.get_nearest_non_block_module(
+                self.resolver.opt_parent(scope_id).unwrap_or(scope_id),
+            ),
+            self.resolver,
+        );
+        self.resolve_doc_links(doc_attrs(attrs.iter()), parent_scope);
+    }
+
+    fn resolve_doc_links_extern_inner(&mut self, def_id: DefId) {
+        if !self.resolver.cstore().may_have_doc_links_untracked(def_id) {
+            return;
+        }
+        let attrs = Vec::from_iter(self.resolver.cstore().item_attrs_untracked(def_id, self.sess));
+        let parent_scope = ParentScope::module(self.resolver.expect_module(def_id), self.resolver);
+        self.resolve_doc_links(doc_attrs(attrs.iter()), parent_scope);
+    }
+
+    fn resolve_doc_links_local(&mut self, attrs: &[ast::Attribute]) {
+        if !attrs.iter().any(|attr| attr.may_have_doc_links()) {
+            return;
+        }
+        self.resolve_doc_links(doc_attrs(attrs.iter()), self.parent_scope);
+    }
+
+    fn resolve_and_cache(
+        &mut self,
+        path_str: &str,
+        ns: Namespace,
+        parent_scope: &ParentScope<'ra>,
+    ) -> bool {
+        // FIXME: This caching may be incorrect in case of multiple `macro_rules`
+        // items with the same name in the same module.
+        self.doc_link_resolutions
+            .entry((Symbol::intern(path_str), ns, parent_scope.module.def_id()))
+            .or_insert_with_key(|(path, ns, _)| {
+                self.resolver.resolve_rustdoc_path(path.as_str(), *ns, *parent_scope)
+            })
+            .is_some()
+    }
+
+    fn resolve_doc_links(&mut self, attrs: Attributes, parent_scope: ParentScope<'ra>) {
+        let mut need_traits_in_scope = false;
+        for (doc_module, doc) in attrs.prepare_to_doc_link_resolution() {
+            assert_eq!(doc_module, None);
+            let mut tmp_links = mem::take(&mut self.markdown_links);
+            let links =
+                tmp_links.entry(doc).or_insert_with_key(|doc| preprocessed_markdown_links(doc));
+            for PreprocessedMarkdownLink(pp_link, _) in links {
+                if let Ok(pinfo) = pp_link {
+                    // The logic here is a conservative approximation for path resolution in
+                    // `resolve_with_disambiguator`.
+                    if let Some(ns) = pinfo.disambiguator.map(Disambiguator::ns) {
+                        if self.resolve_and_cache(&pinfo.path_str, ns, &parent_scope) {
+                            continue;
+                        }
+                    }
+
+                    // Resolve all namespaces due to no disambiguator or for diagnostics.
+                    let mut any_resolved = false;
+                    let mut need_assoc = false;
+                    for ns in [TypeNS, ValueNS, MacroNS] {
+                        if self.resolve_and_cache(&pinfo.path_str, ns, &parent_scope) {
+                            any_resolved = true;
+                        } else if ns != MacroNS {
+                            need_assoc = true;
+                        }
+                    }
+
+                    // Resolve all prefixes for type-relative resolution or for diagnostics.
+                    if need_assoc || !any_resolved {
+                        let mut path = &pinfo.path_str[..];
+                        while let Some(idx) = path.rfind("::") {
+                            path = &path[..idx];
+                            need_traits_in_scope = true;
+                            for ns in [TypeNS, ValueNS, MacroNS] {
+                                self.resolve_and_cache(path, ns, &parent_scope);
+                            }
+                        }
+                    }
+                }
+            }
+            self.markdown_links = tmp_links;
+        }
+
+        if need_traits_in_scope {
+            self.add_traits_in_scope(parent_scope.module.def_id());
+        }
+    }
+
+    /// When reexports are inlined, they are replaced with item which they refer to, those items
+    /// may have links in their doc comments, those links are resolved at the item definition site,
+    /// so we need to know traits in scope at that definition site.
+    fn process_module_children_or_reexports(&mut self, module_id: DefId) {
+        if !self.visited_mods.insert(module_id) {
+            return; // avoid infinite recursion
+        }
+
+        for child in self.resolver.module_children_or_reexports(module_id) {
+            // This condition should give a superset of `denied` from `fn clean_use_statement`.
+            if child.vis.is_public()
+                || self.document_private_items
+                    && child.vis != Visibility::Restricted(module_id)
+                    && module_id.is_local()
+            {
+                if let Some(def_id) = child.res.opt_def_id() && !def_id.is_local() {
+                    let scope_id = match child.res {
+                        Res::Def(DefKind::Variant, ..) => self.resolver.parent(def_id),
+                        _ => def_id,
+                    };
+                    self.resolve_doc_links_extern_outer(def_id, scope_id); // Outer attribute scope
+                    if let Res::Def(DefKind::Mod, ..) = child.res {
+                        self.resolve_doc_links_extern_inner(def_id); // Inner attribute scope
+                    }
+                    // `DefKind::Trait`s are processed in `process_extern_impls`.
+                    if let Res::Def(DefKind::Mod | DefKind::Enum, ..) = child.res {
+                        self.process_module_children_or_reexports(def_id);
+                    }
+                    if let Res::Def(DefKind::Struct | DefKind::Union | DefKind::Variant, _) =
+                        child.res
+                    {
+                        let field_def_ids = Vec::from_iter(
+                            self.resolver
+                                .cstore()
+                                .associated_item_def_ids_untracked(def_id, self.sess),
+                        );
+                        for field_def_id in field_def_ids {
+                            self.resolve_doc_links_extern_outer(field_def_id, scope_id);
+                        }
+                    }
+                }
+            }
+        }
+    }
+}
+
+impl Visitor<'_> for EarlyDocLinkResolver<'_, '_> {
+    fn visit_item(&mut self, item: &ast::Item) {
+        self.resolve_doc_links_local(&item.attrs); // Outer attribute scope
+        if let ItemKind::Mod(..) = item.kind {
+            let module_def_id = self.resolver.local_def_id(item.id).to_def_id();
+            let module = self.resolver.expect_module(module_def_id);
+            let old_module = mem::replace(&mut self.parent_scope.module, module);
+            let old_macro_rules = self.parent_scope.macro_rules;
+            self.resolve_doc_links_local(&item.attrs); // Inner attribute scope
+            self.process_module_children_or_reexports(module_def_id);
+            visit::walk_item(self, item);
+            if item
+                .attrs
+                .iter()
+                .all(|attr| !attr.has_name(sym::macro_use) && !attr.has_name(sym::macro_escape))
+            {
+                self.parent_scope.macro_rules = old_macro_rules;
+            }
+            self.parent_scope.module = old_module;
+        } else {
+            match &item.kind {
+                ItemKind::Trait(..) => {
+                    self.all_traits.push(self.resolver.local_def_id(item.id).to_def_id());
+                }
+                ItemKind::Impl(box ast::Impl { of_trait: Some(..), .. }) => {
+                    self.all_trait_impls.push(self.resolver.local_def_id(item.id).to_def_id());
+                }
+                ItemKind::MacroDef(macro_def) if macro_def.macro_rules => {
+                    let (macro_rules_scope, res) =
+                        self.resolver.macro_rules_scope(self.resolver.local_def_id(item.id));
+                    self.parent_scope.macro_rules = macro_rules_scope;
+                    self.all_macro_rules.insert(item.ident.name, res);
+                }
+                _ => {}
+            }
+            visit::walk_item(self, item);
+        }
+    }
+
+    fn visit_assoc_item(&mut self, item: &ast::AssocItem, ctxt: AssocCtxt) {
+        self.resolve_doc_links_local(&item.attrs);
+        visit::walk_assoc_item(self, item, ctxt)
+    }
+
+    fn visit_foreign_item(&mut self, item: &ast::ForeignItem) {
+        self.resolve_doc_links_local(&item.attrs);
+        visit::walk_foreign_item(self, item)
+    }
+
+    fn visit_variant(&mut self, v: &ast::Variant) {
+        self.resolve_doc_links_local(&v.attrs);
+        visit::walk_variant(self, v)
+    }
+
+    fn visit_field_def(&mut self, field: &ast::FieldDef) {
+        self.resolve_doc_links_local(&field.attrs);
+        visit::walk_field_def(self, field)
+    }
+
+    fn visit_block(&mut self, block: &ast::Block) {
+        let old_macro_rules = self.parent_scope.macro_rules;
+        visit::walk_block(self, block);
+        self.parent_scope.macro_rules = old_macro_rules;
+    }
+
+    // NOTE: if doc-comments are ever allowed on other nodes (e.g. function parameters),
+    // then this will have to implement other visitor methods too.
+}
diff --git a/src/librustdoc/passes/collect_trait_impls.rs b/src/librustdoc/passes/collect_trait_impls.rs
new file mode 100644
index 000000000..6b699c790
--- /dev/null
+++ b/src/librustdoc/passes/collect_trait_impls.rs
@@ -0,0 +1,273 @@
+//! Collects trait impls for each item in the crate. For example, if a crate
+//! defines a struct that implements a trait, this pass will note that the
+//! struct implements that trait.
+use super::Pass;
+use crate::clean::*;
+use crate::core::DocContext;
+use crate::formats::cache::Cache;
+use crate::visit::DocVisitor;
+
+use rustc_data_structures::fx::{FxHashMap, FxHashSet};
+use rustc_hir::def_id::DefId;
+use rustc_middle::ty::{self, DefIdTree};
+use rustc_span::symbol::sym;
+
+pub(crate) const COLLECT_TRAIT_IMPLS: Pass = Pass {
+    name: "collect-trait-impls",
+    run: collect_trait_impls,
+    description: "retrieves trait impls for items in the crate",
+};
+
+pub(crate) fn collect_trait_impls(mut krate: Crate, cx: &mut DocContext<'_>) -> Crate {
+    let synth_impls = cx.sess().time("collect_synthetic_impls", || {
+        let mut synth = SyntheticImplCollector { cx, impls: Vec::new() };
+        synth.visit_crate(&krate);
+        synth.impls
+    });
+
+    let prims: FxHashSet<PrimitiveType> = krate.primitives.iter().map(|p| p.1).collect();
+
+    let crate_items = {
+        let mut coll = ItemCollector::new();
+        cx.sess().time("collect_items_for_trait_impls", || coll.visit_crate(&krate));
+        coll.items
+    };
+
+    let mut new_items_external = Vec::new();
+    let mut new_items_local = Vec::new();
+
+    // External trait impls.
+    cx.with_all_trait_impls(|cx, all_trait_impls| {
+        let _prof_timer = cx.tcx.sess.prof.generic_activity("build_extern_trait_impls");
+        for &impl_def_id in all_trait_impls.iter().skip_while(|def_id| def_id.is_local()) {
+            inline::build_impl(cx, None, impl_def_id, None, &mut new_items_external);
+        }
+    });
+
+    // Local trait impls.
+    cx.with_all_trait_impls(|cx, all_trait_impls| {
+        let _prof_timer = cx.tcx.sess.prof.generic_activity("build_local_trait_impls");
+        let mut attr_buf = Vec::new();
+        for &impl_def_id in all_trait_impls.iter().take_while(|def_id| def_id.is_local()) {
+            let mut parent = Some(cx.tcx.parent(impl_def_id));
+            while let Some(did) = parent {
+                attr_buf.extend(
+                    cx.tcx
+                        .get_attrs(did, sym::doc)
+                        .filter(|attr| {
+                            if let Some([attr]) = attr.meta_item_list().as_deref() {
+                                attr.has_name(sym::cfg)
+                            } else {
+                                false
+                            }
+                        })
+                        .cloned(),
+                );
+                parent = cx.tcx.opt_parent(did);
+            }
+            inline::build_impl(cx, None, impl_def_id, Some(&attr_buf), &mut new_items_local);
+            attr_buf.clear();
+        }
+    });
+
+    cx.tcx.sess.prof.generic_activity("build_primitive_trait_impls").run(|| {
+        for def_id in PrimitiveType::all_impls(cx.tcx) {
+            // Try to inline primitive impls from other crates.
+            if !def_id.is_local() {
+                inline::build_impl(cx, None, def_id, None, &mut new_items_external);
+            }
+        }
+        for (prim, did) in PrimitiveType::primitive_locations(cx.tcx) {
+            // Do not calculate blanket impl list for docs that are not going to be rendered.
+            // While the `impl` blocks themselves are only in `libcore`, the module with `doc`
+            // attached is directly included in `libstd` as well.
+            let tcx = cx.tcx;
+            if did.is_local() {
+                for def_id in prim.impls(tcx).filter(|def_id| {
+                    // Avoid including impl blocks with filled-in generics.
+                    // https://github.com/rust-lang/rust/issues/94937
+                    //
+                    // FIXME(notriddle): https://github.com/rust-lang/rust/issues/97129
+                    //
+                    // This tactic of using inherent impl blocks for getting
+                    // auto traits and blanket impls is a hack. What we really
+                    // want is to check if `[T]` impls `Send`, which has
+                    // nothing to do with the inherent impl.
+                    //
+                    // Rustdoc currently uses these `impl` block as a source of
+                    // the `Ty`, as well as the `ParamEnv`, `SubstsRef`, and
+                    // `Generics`. To avoid relying on the `impl` block, these
+                    // things would need to be created from wholecloth, in a
+                    // form that is valid for use in type inference.
+                    let ty = tcx.type_of(def_id);
+                    match ty.kind() {
+                        ty::Slice(ty)
+                        | ty::Ref(_, ty, _)
+                        | ty::RawPtr(ty::TypeAndMut { ty, .. }) => {
+                            matches!(ty.kind(), ty::Param(..))
+                        }
+                        ty::Tuple(tys) => tys.iter().all(|ty| matches!(ty.kind(), ty::Param(..))),
+                        _ => true,
+                    }
+                }) {
+                    let impls = get_auto_trait_and_blanket_impls(cx, def_id);
+                    new_items_external.extend(impls.filter(|i| cx.inlined.insert(i.item_id)));
+                }
+            }
+        }
+    });
+
+    let mut cleaner = BadImplStripper { prims, items: crate_items, cache: &cx.cache };
+    let mut type_did_to_deref_target: FxHashMap<DefId, &Type> = FxHashMap::default();
+
+    // Follow all `Deref` targets of included items and recursively add them as valid
+    fn add_deref_target(
+        cx: &DocContext<'_>,
+        map: &FxHashMap<DefId, &Type>,
+        cleaner: &mut BadImplStripper<'_>,
+        targets: &mut FxHashSet<DefId>,
+        type_did: DefId,
+    ) {
+        if let Some(target) = map.get(&type_did) {
+            debug!("add_deref_target: type {:?}, target {:?}", type_did, target);
+            if let Some(target_prim) = target.primitive_type() {
+                cleaner.prims.insert(target_prim);
+            } else if let Some(target_did) = target.def_id(&cx.cache) {
+                // `impl Deref<Target = S> for S`
+                if !targets.insert(target_did) {
+                    // Avoid infinite cycles
+                    return;
+                }
+                cleaner.items.insert(target_did.into());
+                add_deref_target(cx, map, cleaner, targets, target_did);
+            }
+        }
+    }
+
+    // scan through included items ahead of time to splice in Deref targets to the "valid" sets
+    for it in new_items_external.iter().chain(new_items_local.iter()) {
+        if let ImplItem(box Impl { ref for_, ref trait_, ref items, .. }) = *it.kind {
+            if trait_.as_ref().map(|t| t.def_id()) == cx.tcx.lang_items().deref_trait()
+                && cleaner.keep_impl(for_, true)
+            {
+                let target = items
+                    .iter()
+                    .find_map(|item| match *item.kind {
+                        AssocTypeItem(ref t, _) => Some(&t.type_),
+                        _ => None,
+                    })
+                    .expect("Deref impl without Target type");
+
+                if let Some(prim) = target.primitive_type() {
+                    cleaner.prims.insert(prim);
+                } else if let Some(did) = target.def_id(&cx.cache) {
+                    cleaner.items.insert(did.into());
+                }
+                if let Some(for_did) = for_.def_id(&cx.cache) {
+                    if type_did_to_deref_target.insert(for_did, target).is_none() {
+                        // Since only the `DefId` portion of the `Type` instances is known to be same for both the
+                        // `Deref` target type and the impl for type positions, this map of types is keyed by
+                        // `DefId` and for convenience uses a special cleaner that accepts `DefId`s directly.
+                        if cleaner.keep_impl_with_def_id(for_did.into()) {
+                            let mut targets = FxHashSet::default();
+                            targets.insert(for_did);
+                            add_deref_target(
+                                cx,
+                                &type_did_to_deref_target,
+                                &mut cleaner,
+                                &mut targets,
+                                for_did,
+                            );
+                        }
+                    }
+                }
+            }
+        }
+    }
+
+    // Filter out external items that are not needed
+    new_items_external.retain(|it| {
+        if let ImplItem(box Impl { ref for_, ref trait_, ref kind, .. }) = *it.kind {
+            cleaner.keep_impl(
+                for_,
+                trait_.as_ref().map(|t| t.def_id()) == cx.tcx.lang_items().deref_trait(),
+            ) || trait_.as_ref().map_or(false, |t| cleaner.keep_impl_with_def_id(t.def_id().into()))
+                || kind.is_blanket()
+        } else {
+            true
+        }
+    });
+
+    if let ModuleItem(Module { items, .. }) = &mut *krate.module.kind {
+        items.extend(synth_impls);
+        items.extend(new_items_external);
+        items.extend(new_items_local);
+    } else {
+        panic!("collect-trait-impls can't run");
+    };
+
+    krate
+}
+
+struct SyntheticImplCollector<'a, 'tcx> {
+    cx: &'a mut DocContext<'tcx>,
+    impls: Vec<Item>,
+}
+
+impl<'a, 'tcx> DocVisitor for SyntheticImplCollector<'a, 'tcx> {
+    fn visit_item(&mut self, i: &Item) {
+        if i.is_struct() || i.is_enum() || i.is_union() {
+            // FIXME(eddyb) is this `doc(hidden)` check needed?
+            if !self.cx.tcx.is_doc_hidden(i.item_id.expect_def_id()) {
+                self.impls
+                    .extend(get_auto_trait_and_blanket_impls(self.cx, i.item_id.expect_def_id()));
+            }
+        }
+
+        self.visit_item_recur(i)
+    }
+}
+
+#[derive(Default)]
+struct ItemCollector {
+    items: FxHashSet<ItemId>,
+}
+
+impl ItemCollector {
+    fn new() -> Self {
+        Self::default()
+    }
+}
+
+impl DocVisitor for ItemCollector {
+    fn visit_item(&mut self, i: &Item) {
+        self.items.insert(i.item_id);
+
+        self.visit_item_recur(i)
+    }
+}
+
+struct BadImplStripper<'a> {
+    prims: FxHashSet<PrimitiveType>,
+    items: FxHashSet<ItemId>,
+    cache: &'a Cache,
+}
+
+impl<'a> BadImplStripper<'a> {
+    fn keep_impl(&self, ty: &Type, is_deref: bool) -> bool {
+        if let Generic(_) = ty {
+            // keep impls made on generics
+            true
+        } else if let Some(prim) = ty.primitive_type() {
+            self.prims.contains(&prim)
+        } else if let Some(did) = ty.def_id(self.cache) {
+            is_deref || self.keep_impl_with_def_id(did.into())
+        } else {
+            false
+        }
+    }
+
+    fn keep_impl_with_def_id(&self, item_id: ItemId) -> bool {
+        self.items.contains(&item_id)
+    }
+}
diff --git a/src/librustdoc/passes/html_tags.rs b/src/librustdoc/passes/html_tags.rs
new file mode 100644
index 000000000..f3a3c853c
--- /dev/null
+++ b/src/librustdoc/passes/html_tags.rs
@@ -0,0 +1,303 @@
+//! Detects invalid HTML (like an unclosed `<span>`) in doc comments.
+use super::Pass;
+use crate::clean::*;
+use crate::core::DocContext;
+use crate::html::markdown::main_body_opts;
+use crate::visit::DocVisitor;
+
+use pulldown_cmark::{BrokenLink, Event, LinkType, Parser, Tag};
+
+use std::iter::Peekable;
+use std::ops::Range;
+use std::str::CharIndices;
+
+pub(crate) const CHECK_INVALID_HTML_TAGS: Pass = Pass {
+    name: "check-invalid-html-tags",
+    run: check_invalid_html_tags,
+    description: "detects invalid HTML tags in doc comments",
+};
+
+struct InvalidHtmlTagsLinter<'a, 'tcx> {
+    cx: &'a mut DocContext<'tcx>,
+}
+
+pub(crate) fn check_invalid_html_tags(krate: Crate, cx: &mut DocContext<'_>) -> Crate {
+    if cx.tcx.sess.is_nightly_build() {
+        let mut coll = InvalidHtmlTagsLinter { cx };
+        coll.visit_crate(&krate);
+    }
+    krate
+}
+
+const ALLOWED_UNCLOSED: &[&str] = &[
+    "area", "base", "br", "col", "embed", "hr", "img", "input", "keygen", "link", "meta", "param",
+    "source", "track", "wbr",
+];
+
+fn drop_tag(
+    tags: &mut Vec<(String, Range<usize>)>,
+    tag_name: String,
+    range: Range<usize>,
+    f: &impl Fn(&str, &Range<usize>, bool),
+) {
+    let tag_name_low = tag_name.to_lowercase();
+    if let Some(pos) = tags.iter().rposition(|(t, _)| t.to_lowercase() == tag_name_low) {
+        // If the tag is nested inside a "<script>" or a "<style>" tag, no warning should
+        // be emitted.
+        let should_not_warn = tags.iter().take(pos + 1).any(|(at, _)| {
+            let at = at.to_lowercase();
+            at == "script" || at == "style"
+        });
+        for (last_tag_name, last_tag_span) in tags.drain(pos + 1..) {
+            if should_not_warn {
+                continue;
+            }
+            let last_tag_name_low = last_tag_name.to_lowercase();
+            if ALLOWED_UNCLOSED.contains(&last_tag_name_low.as_str()) {
+                continue;
+            }
+            // `tags` is used as a queue, meaning that everything after `pos` is included inside it.
+            // So `<h2><h3></h2>` will look like `["h2", "h3"]`. So when closing `h2`, we will still
+            // have `h3`, meaning the tag wasn't closed as it should have.
+            f(&format!("unclosed HTML tag `{}`", last_tag_name), &last_tag_span, true);
+        }
+        // Remove the `tag_name` that was originally closed
+        tags.pop();
+    } else {
+        // It can happen for example in this case: `<h2></script></h2>` (the `h2` tag isn't required
+        // but it helps for the visualization).
+        f(&format!("unopened HTML tag `{}`", tag_name), &range, false);
+    }
+}
+
+fn extract_path_backwards(text: &str, end_pos: usize) -> Option<usize> {
+    use rustc_lexer::{is_id_continue, is_id_start};
+    let mut current_pos = end_pos;
+    loop {
+        if current_pos >= 2 && text[..current_pos].ends_with("::") {
+            current_pos -= 2;
+        }
+        let new_pos = text[..current_pos]
+            .char_indices()
+            .rev()
+            .take_while(|(_, c)| is_id_start(*c) || is_id_continue(*c))
+            .reduce(|_accum, item| item)
+            .and_then(|(new_pos, c)| is_id_start(c).then_some(new_pos));
+        if let Some(new_pos) = new_pos {
+            if current_pos != new_pos {
+                current_pos = new_pos;
+                continue;
+            }
+        }
+        break;
+    }
+    if current_pos == end_pos { None } else { Some(current_pos) }
+}
+
+fn is_valid_for_html_tag_name(c: char, is_empty: bool) -> bool {
+    // https://spec.commonmark.org/0.30/#raw-html
+    //
+    // > A tag name consists of an ASCII letter followed by zero or more ASCII letters, digits, or
+    // > hyphens (-).
+    c.is_ascii_alphabetic() || !is_empty && (c == '-' || c.is_ascii_digit())
+}
+
+fn extract_html_tag(
+    tags: &mut Vec<(String, Range<usize>)>,
+    text: &str,
+    range: &Range<usize>,
+    start_pos: usize,
+    iter: &mut Peekable<CharIndices<'_>>,
+    f: &impl Fn(&str, &Range<usize>, bool),
+) {
+    let mut tag_name = String::new();
+    let mut is_closing = false;
+    let mut prev_pos = start_pos;
+
+    loop {
+        let (pos, c) = match iter.peek() {
+            Some((pos, c)) => (*pos, *c),
+            // In case we reached the of the doc comment, we want to check that it's an
+            // unclosed HTML tag. For example "/// <h3".
+            None => (prev_pos, '\0'),
+        };
+        prev_pos = pos;
+        // Checking if this is a closing tag (like `</a>` for `<a>`).
+        if c == '/' && tag_name.is_empty() {
+            is_closing = true;
+        } else if is_valid_for_html_tag_name(c, tag_name.is_empty()) {
+            tag_name.push(c);
+        } else {
+            if !tag_name.is_empty() {
+                let mut r = Range { start: range.start + start_pos, end: range.start + pos };
+                if c == '>' {
+                    // In case we have a tag without attribute, we can consider the span to
+                    // refer to it fully.
+                    r.end += 1;
+                }
+                if is_closing {
+                    // In case we have "</div >" or even "</div         >".
+                    if c != '>' {
+                        if !c.is_whitespace() {
+                            // It seems like it's not a valid HTML tag.
+                            break;
+                        }
+                        let mut found = false;
+                        for (new_pos, c) in text[pos..].char_indices() {
+                            if !c.is_whitespace() {
+                                if c == '>' {
+                                    r.end = range.start + new_pos + 1;
+                                    found = true;
+                                }
+                                break;
+                            }
+                        }
+                        if !found {
+                            break;
+                        }
+                    }
+                    drop_tag(tags, tag_name, r, f);
+                } else {
+                    tags.push((tag_name, r));
+                }
+            }
+            break;
+        }
+        iter.next();
+    }
+}
+
+fn extract_tags(
+    tags: &mut Vec<(String, Range<usize>)>,
+    text: &str,
+    range: Range<usize>,
+    is_in_comment: &mut Option<Range<usize>>,
+    f: &impl Fn(&str, &Range<usize>, bool),
+) {
+    let mut iter = text.char_indices().peekable();
+
+    while let Some((start_pos, c)) = iter.next() {
+        if is_in_comment.is_some() {
+            if text[start_pos..].starts_with("-->") {
+                *is_in_comment = None;
+            }
+        } else if c == '<' {
+            if text[start_pos..].starts_with("<!--") {
+                // We skip the "!--" part. (Once `advance_by` is stable, might be nice to use it!)
+                iter.next();
+                iter.next();
+                iter.next();
+                *is_in_comment = Some(Range {
+                    start: range.start + start_pos,
+                    end: range.start + start_pos + 3,
+                });
+            } else {
+                extract_html_tag(tags, text, &range, start_pos, &mut iter, f);
+            }
+        }
+    }
+}
+
+impl<'a, 'tcx> DocVisitor for InvalidHtmlTagsLinter<'a, 'tcx> {
+    fn visit_item(&mut self, item: &Item) {
+        let tcx = self.cx.tcx;
+        let Some(hir_id) = DocContext::as_local_hir_id(tcx, item.item_id)
+        // If non-local, no need to check anything.
+        else { return };
+        let dox = item.attrs.collapsed_doc_value().unwrap_or_default();
+        if !dox.is_empty() {
+            let report_diag = |msg: &str, range: &Range<usize>, is_open_tag: bool| {
+                let sp = match super::source_span_for_markdown_range(tcx, &dox, range, &item.attrs)
+                {
+                    Some(sp) => sp,
+                    None => item.attr_span(tcx),
+                };
+                tcx.struct_span_lint_hir(crate::lint::INVALID_HTML_TAGS, hir_id, sp, |lint| {
+                    use rustc_lint_defs::Applicability;
+                    let mut diag = lint.build(msg);
+                    // If a tag looks like `<this>`, it might actually be a generic.
+                    // We don't try to detect stuff `<like, this>` because that's not valid HTML,
+                    // and we don't try to detect stuff `<like this>` because that's not valid Rust.
+                    if let Some(Some(generics_start)) = (is_open_tag
+                        && dox[..range.end].ends_with('>'))
+                    .then(|| extract_path_backwards(&dox, range.start))
+                    {
+                        let generics_sp = match super::source_span_for_markdown_range(
+                            tcx,
+                            &dox,
+                            &(generics_start..range.end),
+                            &item.attrs,
+                        ) {
+                            Some(sp) => sp,
+                            None => item.attr_span(tcx),
+                        };
+                        // multipart form is chosen here because ``Vec<i32>`` would be confusing.
+                        diag.multipart_suggestion(
+                            "try marking as source code",
+                            vec![
+                                (generics_sp.shrink_to_lo(), String::from("`")),
+                                (generics_sp.shrink_to_hi(), String::from("`")),
+                            ],
+                            Applicability::MaybeIncorrect,
+                        );
+                    }
+                    diag.emit()
+                });
+            };
+
+            let mut tags = Vec::new();
+            let mut is_in_comment = None;
+            let mut in_code_block = false;
+
+            let link_names = item.link_names(&self.cx.cache);
+
+            let mut replacer = |broken_link: BrokenLink<'_>| {
+                if let Some(link) =
+                    link_names.iter().find(|link| *link.original_text == *broken_link.reference)
+                {
+                    Some((link.href.as_str().into(), link.new_text.as_str().into()))
+                } else if matches!(
+                    &broken_link.link_type,
+                    LinkType::Reference | LinkType::ReferenceUnknown
+                ) {
+                    // If the link is shaped [like][this], suppress any broken HTML in the [this] part.
+                    // The `broken_intra_doc_links` will report typos in there anyway.
+                    Some((
+                        broken_link.reference.to_string().into(),
+                        broken_link.reference.to_string().into(),
+                    ))
+                } else {
+                    None
+                }
+            };
+
+            let p =
+                Parser::new_with_broken_link_callback(&dox, main_body_opts(), Some(&mut replacer))
+                    .into_offset_iter();
+
+            for (event, range) in p {
+                match event {
+                    Event::Start(Tag::CodeBlock(_)) => in_code_block = true,
+                    Event::Html(text) | Event::Text(text) if !in_code_block => {
+                        extract_tags(&mut tags, &text, range, &mut is_in_comment, &report_diag)
+                    }
+                    Event::End(Tag::CodeBlock(_)) => in_code_block = false,
+                    _ => {}
+                }
+            }
+
+            for (tag, range) in tags.iter().filter(|(t, _)| {
+                let t = t.to_lowercase();
+                !ALLOWED_UNCLOSED.contains(&t.as_str())
+            }) {
+                report_diag(&format!("unclosed HTML tag `{}`", tag), range, true);
+            }
+
+            if let Some(range) = is_in_comment {
+                report_diag("Unclosed HTML comment", &range, false);
+            }
+        }
+
+        self.visit_item_recur(item)
+    }
+}
diff --git a/src/librustdoc/passes/mod.rs b/src/librustdoc/passes/mod.rs
new file mode 100644
index 000000000..f81b38ea3
--- /dev/null
+++ b/src/librustdoc/passes/mod.rs
@@ -0,0 +1,212 @@
+//! Contains information about "passes", used to modify crate information during the documentation
+//! process.
+
+use rustc_middle::ty::TyCtxt;
+use rustc_span::{InnerSpan, Span, DUMMY_SP};
+use std::ops::Range;
+
+use self::Condition::*;
+use crate::clean::{self, DocFragmentKind};
+use crate::core::DocContext;
+
+mod stripper;
+pub(crate) use stripper::*;
+
+mod bare_urls;
+pub(crate) use self::bare_urls::CHECK_BARE_URLS;
+
+mod strip_hidden;
+pub(crate) use self::strip_hidden::STRIP_HIDDEN;
+
+mod strip_private;
+pub(crate) use self::strip_private::STRIP_PRIVATE;
+
+mod strip_priv_imports;
+pub(crate) use self::strip_priv_imports::STRIP_PRIV_IMPORTS;
+
+mod propagate_doc_cfg;
+pub(crate) use self::propagate_doc_cfg::PROPAGATE_DOC_CFG;
+
+pub(crate) mod collect_intra_doc_links;
+pub(crate) use self::collect_intra_doc_links::COLLECT_INTRA_DOC_LINKS;
+
+mod check_doc_test_visibility;
+pub(crate) use self::check_doc_test_visibility::CHECK_DOC_TEST_VISIBILITY;
+
+mod collect_trait_impls;
+pub(crate) use self::collect_trait_impls::COLLECT_TRAIT_IMPLS;
+
+mod check_code_block_syntax;
+pub(crate) use self::check_code_block_syntax::CHECK_CODE_BLOCK_SYNTAX;
+
+mod calculate_doc_coverage;
+pub(crate) use self::calculate_doc_coverage::CALCULATE_DOC_COVERAGE;
+
+mod html_tags;
+pub(crate) use self::html_tags::CHECK_INVALID_HTML_TAGS;
+
+/// 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(crate) struct Pass {
+    pub(crate) name: &'static str,
+    pub(crate) run: fn(clean::Crate, &mut DocContext<'_>) -> clean::Crate,
+    pub(crate) 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(crate) struct ConditionalPass {
+    pub(crate) pass: Pass,
+    pub(crate) condition: Condition,
+}
+
+/// How to decide whether to run a conditional pass.
+#[derive(Copy, Clone)]
+pub(crate) 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(crate) const PASSES: &[Pass] = &[
+    CHECK_DOC_TEST_VISIBILITY,
+    STRIP_HIDDEN,
+    STRIP_PRIVATE,
+    STRIP_PRIV_IMPORTS,
+    PROPAGATE_DOC_CFG,
+    COLLECT_INTRA_DOC_LINKS,
+    CHECK_CODE_BLOCK_SYNTAX,
+    COLLECT_TRAIT_IMPLS,
+    CALCULATE_DOC_COVERAGE,
+    CHECK_INVALID_HTML_TAGS,
+    CHECK_BARE_URLS,
+];
+
+/// The list of passes run by default.
+pub(crate) const DEFAULT_PASSES: &[ConditionalPass] = &[
+    ConditionalPass::always(COLLECT_TRAIT_IMPLS),
+    ConditionalPass::always(CHECK_DOC_TEST_VISIBILITY),
+    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(CHECK_INVALID_HTML_TAGS),
+    ConditionalPass::always(PROPAGATE_DOC_CFG),
+    ConditionalPass::always(CHECK_BARE_URLS),
+];
+
+/// The list of default passes run when `--doc-coverage` is passed to rustdoc.
+pub(crate) const COVERAGE_PASSES: &[ConditionalPass] = &[
+    ConditionalPass::new(STRIP_HIDDEN, WhenNotDocumentHidden),
+    ConditionalPass::new(STRIP_PRIVATE, WhenNotDocumentPrivate),
+    ConditionalPass::always(CALCULATE_DOC_COVERAGE),
+];
+
+impl ConditionalPass {
+    pub(crate) const fn always(pass: Pass) -> Self {
+        Self::new(pass, Always)
+    }
+
+    pub(crate) const fn new(pass: Pass, condition: Condition) -> Self {
+        ConditionalPass { pass, condition }
+    }
+}
+
+/// Returns the given default set of passes.
+pub(crate) fn defaults(show_coverage: bool) -> &'static [ConditionalPass] {
+    if show_coverage { COVERAGE_PASSES } else { DEFAULT_PASSES }
+}
+
+/// Returns a span encompassing all the given attributes.
+pub(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.
+pub(crate) fn source_span_for_markdown_range(
+    tcx: TyCtxt<'_>,
+    markdown: &str,
+    md_range: &Range<usize>,
+    attrs: &clean::Attributes,
+) -> Option<Span> {
+    let is_all_sugared_doc =
+        attrs.doc_strings.iter().all(|frag| frag.kind == DocFragmentKind::SugaredDoc);
+
+    if !is_all_sugared_doc {
+        return None;
+    }
+
+    let snippet = tcx.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()?;
+            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,
+    )))
+}
diff --git a/src/librustdoc/passes/propagate_doc_cfg.rs b/src/librustdoc/passes/propagate_doc_cfg.rs
new file mode 100644
index 000000000..0c5d83655
--- /dev/null
+++ b/src/librustdoc/passes/propagate_doc_cfg.rs
@@ -0,0 +1,45 @@
+//! Propagates [`#[doc(cfg(...))]`](https://github.com/rust-lang/rust/issues/43781) to child items.
+use std::sync::Arc;
+
+use crate::clean::cfg::Cfg;
+use crate::clean::{Crate, Item};
+use crate::core::DocContext;
+use crate::fold::DocFolder;
+use crate::passes::Pass;
+
+pub(crate) const PROPAGATE_DOC_CFG: Pass = Pass {
+    name: "propagate-doc-cfg",
+    run: propagate_doc_cfg,
+    description: "propagates `#[doc(cfg(...))]` to child items",
+};
+
+pub(crate) fn propagate_doc_cfg(cr: Crate, _: &mut DocContext<'_>) -> Crate {
+    CfgPropagator { parent_cfg: None }.fold_crate(cr)
+}
+
+struct CfgPropagator {
+    parent_cfg: Option<Arc<Cfg>>,
+}
+
+impl DocFolder for CfgPropagator {
+    fn fold_item(&mut self, mut item: Item) -> Option<Item> {
+        let old_parent_cfg = self.parent_cfg.clone();
+
+        let new_cfg = match (self.parent_cfg.take(), item.cfg.take()) {
+            (None, None) => None,
+            (Some(rc), None) | (None, Some(rc)) => Some(rc),
+            (Some(mut a), Some(b)) => {
+                let b = Arc::try_unwrap(b).unwrap_or_else(|rc| Cfg::clone(&rc));
+                *Arc::make_mut(&mut a) &= b;
+                Some(a)
+            }
+        };
+        self.parent_cfg = new_cfg.clone();
+        item.cfg = new_cfg;
+
+        let result = self.fold_item_recur(item);
+        self.parent_cfg = old_parent_cfg;
+
+        Some(result)
+    }
+}
diff --git a/src/librustdoc/passes/strip_hidden.rs b/src/librustdoc/passes/strip_hidden.rs
new file mode 100644
index 000000000..533e2ce46
--- /dev/null
+++ b/src/librustdoc/passes/strip_hidden.rs
@@ -0,0 +1,68 @@
+//! Strip all doc(hidden) items from the output.
+use rustc_span::symbol::sym;
+use std::mem;
+
+use crate::clean;
+use crate::clean::{Item, ItemIdSet, NestedAttributesExt};
+use crate::core::DocContext;
+use crate::fold::{strip_item, DocFolder};
+use crate::passes::{ImplStripper, Pass};
+
+pub(crate) const STRIP_HIDDEN: Pass = Pass {
+    name: "strip-hidden",
+    run: strip_hidden,
+    description: "strips all `#[doc(hidden)]` items from the output",
+};
+
+/// Strip items marked `#[doc(hidden)]`
+pub(crate) fn strip_hidden(krate: clean::Crate, cx: &mut DocContext<'_>) -> clean::Crate {
+    let mut retained = ItemIdSet::default();
+
+    // strip all #[doc(hidden)] items
+    let krate = {
+        let mut stripper = Stripper { retained: &mut retained, update_retained: true };
+        stripper.fold_crate(krate)
+    };
+
+    // strip all impls referencing stripped items
+    let mut stripper = ImplStripper { retained: &retained, cache: &cx.cache };
+    stripper.fold_crate(krate)
+}
+
+struct Stripper<'a> {
+    retained: &'a mut ItemIdSet,
+    update_retained: bool,
+}
+
+impl<'a> DocFolder for Stripper<'a> {
+    fn fold_item(&mut self, i: Item) -> Option<Item> {
+        if i.attrs.lists(sym::doc).has_word(sym::hidden) {
+            debug!("strip_hidden: stripping {:?} {:?}", i.type_(), i.name);
+            // Use a dedicated hidden item for fields, variants, and modules.
+            // We need to keep private fields and variants, so that the docs
+            // can show a placeholder "// some variants omitted". We need to keep
+            // private modules, because they can contain impl blocks, and impl
+            // block privacy is inherited from the type and trait, not from the
+            // module it's defined in. Both of these are marked "stripped," and
+            // not included in the final docs, but since they still have an effect
+            // on the final doc, cannot be completely removed from the Clean IR.
+            match *i.kind {
+                clean::StructFieldItem(..) | clean::ModuleItem(..) | clean::VariantItem(..) => {
+                    // 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.
+                    let old = mem::replace(&mut self.update_retained, false);
+                    let ret = strip_item(self.fold_item_recur(i));
+                    self.update_retained = old;
+                    return Some(ret);
+                }
+                _ => return None,
+            }
+        } else {
+            if self.update_retained {
+                self.retained.insert(i.item_id);
+            }
+        }
+        Some(self.fold_item_recur(i))
+    }
+}
diff --git a/src/librustdoc/passes/strip_priv_imports.rs b/src/librustdoc/passes/strip_priv_imports.rs
new file mode 100644
index 000000000..85be8fa10
--- /dev/null
+++ b/src/librustdoc/passes/strip_priv_imports.rs
@@ -0,0 +1,16 @@
+//! Strips all private import statements (use, extern crate) from a
+//! crate.
+use crate::clean;
+use crate::core::DocContext;
+use crate::fold::DocFolder;
+use crate::passes::{ImportStripper, Pass};
+
+pub(crate) const STRIP_PRIV_IMPORTS: Pass = Pass {
+    name: "strip-priv-imports",
+    run: strip_priv_imports,
+    description: "strips all private import statements (`use`, `extern crate`) from a crate",
+};
+
+pub(crate) fn strip_priv_imports(krate: clean::Crate, _: &mut DocContext<'_>) -> clean::Crate {
+    ImportStripper.fold_crate(krate)
+}
diff --git a/src/librustdoc/passes/strip_private.rs b/src/librustdoc/passes/strip_private.rs
new file mode 100644
index 000000000..9ba841a31
--- /dev/null
+++ b/src/librustdoc/passes/strip_private.rs
@@ -0,0 +1,35 @@
+//! Strip all private items from the output. Additionally implies strip_priv_imports.
+//! Basically, the goal is to remove items that are not relevant for public documentation.
+use crate::clean::{self, ItemIdSet};
+use crate::core::DocContext;
+use crate::fold::DocFolder;
+use crate::passes::{ImplStripper, ImportStripper, Pass, Stripper};
+
+pub(crate) const STRIP_PRIVATE: Pass = Pass {
+    name: "strip-private",
+    run: strip_private,
+    description: "strips all private items from a crate which cannot be seen externally, \
+                  implies strip-priv-imports",
+};
+
+/// Strip private items from the point of view of a crate or externally from a
+/// crate, specified by the `xcrate` flag.
+pub(crate) fn strip_private(mut krate: clean::Crate, cx: &mut DocContext<'_>) -> clean::Crate {
+    // This stripper collects all *retained* nodes.
+    let mut retained = ItemIdSet::default();
+
+    // strip all private items
+    {
+        let mut stripper = Stripper {
+            retained: &mut retained,
+            access_levels: &cx.cache.access_levels,
+            update_retained: true,
+            is_json_output: cx.output_format.is_json() && !cx.show_coverage,
+        };
+        krate = ImportStripper.fold_crate(stripper.fold_crate(krate));
+    }
+
+    // strip all impls referencing private items
+    let mut stripper = ImplStripper { retained: &retained, cache: &cx.cache };
+    stripper.fold_crate(krate)
+}
diff --git a/src/librustdoc/passes/stripper.rs b/src/librustdoc/passes/stripper.rs
new file mode 100644
index 000000000..0d419042a
--- /dev/null
+++ b/src/librustdoc/passes/stripper.rs
@@ -0,0 +1,188 @@
+//! A collection of utility functions for the `strip_*` passes.
+use rustc_hir::def_id::DefId;
+use rustc_middle::middle::privacy::AccessLevels;
+use std::mem;
+
+use crate::clean::{self, Item, ItemId, ItemIdSet};
+use crate::fold::{strip_item, DocFolder};
+use crate::formats::cache::Cache;
+
+pub(crate) struct Stripper<'a> {
+    pub(crate) retained: &'a mut ItemIdSet,
+    pub(crate) access_levels: &'a AccessLevels<DefId>,
+    pub(crate) update_retained: bool,
+    pub(crate) is_json_output: bool,
+}
+
+impl<'a> Stripper<'a> {
+    // We need to handle this differently for the JSON output because some non exported items could
+    // be used in public API. And so, we need these items as well. `is_exported` only checks if they
+    // are in the public API, which is not enough.
+    #[inline]
+    fn is_item_reachable(&self, item_id: ItemId) -> bool {
+        if self.is_json_output {
+            self.access_levels.is_reachable(item_id.expect_def_id())
+        } else {
+            self.access_levels.is_exported(item_id.expect_def_id())
+        }
+    }
+}
+
+impl<'a> DocFolder for Stripper<'a> {
+    fn fold_item(&mut self, i: Item) -> Option<Item> {
+        match *i.kind {
+            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 Some(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::AssocTypeItem(..)
+            | clean::TraitAliasItem(..)
+            | clean::MacroItem(..)
+            | clean::ForeignTypeItem => {
+                let item_id = i.item_id;
+                if item_id.is_local() && !self.is_item_reachable(item_id) {
+                    debug!("Stripper: stripping {:?} {:?}", i.type_(), i.name);
+                    return None;
+                }
+            }
+
+            clean::StructFieldItem(..) => {
+                if !i.visibility.is_public() {
+                    return Some(strip_item(i));
+                }
+            }
+
+            clean::ModuleItem(..) => {
+                if i.item_id.is_local() && !i.visibility.is_public() {
+                    debug!("Stripper: stripping module {:?}", i.name);
+                    let old = mem::replace(&mut self.update_retained, false);
+                    let ret = strip_item(self.fold_item_recur(i));
+                    self.update_retained = old;
+                    return Some(ret);
+                }
+            }
+
+            // handled in the `strip-priv-imports` pass
+            clean::ExternCrateItem { .. } | clean::ImportItem(..) => {}
+
+            clean::ImplItem(..) => {}
+
+            // tymethods etc. have no control over privacy
+            clean::TyMethodItem(..) | clean::TyAssocConstItem(..) | clean::TyAssocTypeItem(..) => {}
+
+            // Proc-macros are always public
+            clean::ProcMacroItem(..) => {}
+
+            // Primitives are never stripped
+            clean::PrimitiveItem(..) => {}
+
+            // Keywords are never stripped
+            clean::KeywordItem => {}
+        }
+
+        let fastreturn = match *i.kind {
+            // 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,
+            // Variant fields have inherited visibility
+            clean::VariantItem(clean::Variant::Struct(..) | clean::Variant::Tuple(..)) => true,
+            _ => false,
+        };
+
+        let i = if fastreturn {
+            if self.update_retained {
+                self.retained.insert(i.item_id);
+            }
+            return Some(i);
+        } else {
+            self.fold_item_recur(i)
+        };
+
+        if self.update_retained {
+            self.retained.insert(i.item_id);
+        }
+        Some(i)
+    }
+}
+
+/// This stripper discards all impls which reference stripped items
+pub(crate) struct ImplStripper<'a> {
+    pub(crate) retained: &'a ItemIdSet,
+    pub(crate) cache: &'a Cache,
+}
+
+impl<'a> DocFolder for ImplStripper<'a> {
+    fn fold_item(&mut self, i: Item) -> Option<Item> {
+        if let clean::ImplItem(ref imp) = *i.kind {
+            // Impl blocks can be skipped if they are: empty; not a trait impl; and have no
+            // documentation.
+            if imp.trait_.is_none() && imp.items.is_empty() && i.doc_value().is_none() {
+                return None;
+            }
+            if let Some(did) = imp.for_.def_id(self.cache) {
+                if did.is_local() && !imp.for_.is_assoc_ty() && !self.retained.contains(&did.into())
+                {
+                    debug!("ImplStripper: impl item for stripped type; removing");
+                    return None;
+                }
+            }
+            if let Some(did) = imp.trait_.as_ref().map(|t| t.def_id()) {
+                if did.is_local() && !self.retained.contains(&did.into()) {
+                    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(self.cache) {
+                        if did.is_local() && !self.retained.contains(&did.into()) {
+                            debug!(
+                                "ImplStripper: stripped item in trait's generics; removing impl"
+                            );
+                            return None;
+                        }
+                    }
+                }
+            }
+        }
+        Some(self.fold_item_recur(i))
+    }
+}
+
+/// This stripper discards all private import statements (`use`, `extern crate`)
+pub(crate) struct ImportStripper;
+
+impl DocFolder for ImportStripper {
+    fn fold_item(&mut self, i: Item) -> Option<Item> {
+        match *i.kind {
+            clean::ExternCrateItem { .. } | clean::ImportItem(..) if !i.visibility.is_public() => {
+                None
+            }
+            _ => Some(self.fold_item_recur(i)),
+        }
+    }
+}