From 8437d7b1d30b62b0ada5afd21ba4f9e32635bf31 Mon Sep 17 00:00:00 2001
From: Joshua Nelson <jyn514@gmail.com>
Date: Sat, 26 Sep 2020 22:32:20 -0400
Subject: [PATCH 1/2] Resolve `crate` properly across crates

---
 src/librustdoc/passes/collect_intra_doc_links.rs    | 13 ++++++++++++-
 .../auxiliary/intra-link-cross-crate-crate.rs       |  5 +++++
 src/test/rustdoc/intra-link-cross-crate-crate.rs    |  6 ++++++
 3 files changed, 23 insertions(+), 1 deletion(-)
 create mode 100644 src/test/rustdoc/auxiliary/intra-link-cross-crate-crate.rs
 create mode 100644 src/test/rustdoc/intra-link-cross-crate-crate.rs

diff --git a/src/librustdoc/passes/collect_intra_doc_links.rs b/src/librustdoc/passes/collect_intra_doc_links.rs
index 5d74a3da9a205..a463c0a3c9cda 100644
--- a/src/librustdoc/passes/collect_intra_doc_links.rs
+++ b/src/librustdoc/passes/collect_intra_doc_links.rs
@@ -911,7 +911,7 @@ impl LinkCollector<'_, '_> {
                 parent_node
             };
 
-            let module_id = if let Some(id) = base_node {
+            let mut module_id = if let Some(id) = base_node {
                 id
             } else {
                 debug!("attempting to resolve item without parent module: {}", path_str);
@@ -934,6 +934,17 @@ impl LinkCollector<'_, '_> {
                     resolved_self = format!("{}::{}", name, &path_str[6..]);
                     path_str = &resolved_self;
                 }
+            } else if path_str.starts_with("crate::") {
+                use rustc_span::def_id::CRATE_DEF_INDEX;
+
+                // HACK(jynelson): rustc_resolve thinks that `crate` is the crate currently being documented.
+                // But rustdoc wants it to mean the crate this item was originally present in.
+                // To work around this, remove it and resolve relative to the crate root instead.
+                // HACK(jynelson)(2): If we just strip `crate::` then suddenly primitives become ambiguous
+                // (consider `crate::char`). Instead, change it to `self::`. This works because 'self' is now the crate root.
+                resolved_self = format!("self::{}", &path_str["crate::".len()..]);
+                path_str = &resolved_self;
+                module_id = DefId { krate: item.def_id.krate, index: CRATE_DEF_INDEX };
             }
 
             match self.resolve_with_disambiguator(
diff --git a/src/test/rustdoc/auxiliary/intra-link-cross-crate-crate.rs b/src/test/rustdoc/auxiliary/intra-link-cross-crate-crate.rs
new file mode 100644
index 0000000000000..a37848e23d993
--- /dev/null
+++ b/src/test/rustdoc/auxiliary/intra-link-cross-crate-crate.rs
@@ -0,0 +1,5 @@
+#![crate_name = "inner"]
+
+/// Links to [crate::g]
+pub fn f() {}
+pub fn g() {}
diff --git a/src/test/rustdoc/intra-link-cross-crate-crate.rs b/src/test/rustdoc/intra-link-cross-crate-crate.rs
new file mode 100644
index 0000000000000..edf544708b628
--- /dev/null
+++ b/src/test/rustdoc/intra-link-cross-crate-crate.rs
@@ -0,0 +1,6 @@
+// aux-build:intra-link-cross-crate-crate.rs
+// build-aux-docs
+#![crate_name = "outer"]
+extern crate inner;
+// @has outer/fn.f.html '//a[@href="../inner/fn.g.html"]' "crate::g"
+pub use inner::f;

From 406584621a4e2d3752b2444c5bed2218447f0bfe Mon Sep 17 00:00:00 2001
From: Joshua Nelson <jyn514@gmail.com>
Date: Sat, 26 Sep 2020 23:44:12 -0400
Subject: [PATCH 2/2] Use relative links instead of intra-doc links

Previously, `BTreeMap` tried to link to `crate::collections`, intending
for the link to go to `std/collections/index.html`. But `BTreeMap` is
defined in `alloc`, so after the fix in the previous commit, the links
instead went to `alloc/collections/index.html`, which has almost no
information.

This changes it to link to `index.html`, which only works when viewing
from `std::collections::BTreeMap`, the most common place to visit the
docs. Fixing it to work from anywhere would require the docs for
`std::collections` to be duplicated in `alloc::collections`, which in
turn would require HashMap to be `alloc` for intra-doc links to work
(https://github.com/rust-lang/rust/issues/74481).
---
 library/alloc/src/collections/btree/map.rs | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/library/alloc/src/collections/btree/map.rs b/library/alloc/src/collections/btree/map.rs
index b4e9929af5ff2..3fb03a5412e4f 100644
--- a/library/alloc/src/collections/btree/map.rs
+++ b/library/alloc/src/collections/btree/map.rs
@@ -811,7 +811,7 @@ impl<K: Ord, V> BTreeMap<K, V> {
     /// types that can be `==` without being identical. See the [module-level
     /// documentation] for more.
     ///
-    /// [module-level documentation]: crate::collections#insert-and-complex-keys
+    /// [module-level documentation]: index.html#insert-and-complex-keys
     ///
     /// # Examples
     ///