From f5b97e52c97fe6cc12aba3587c12e37b403deea4 Mon Sep 17 00:00:00 2001
From: Daiki Ihara <sasurau4@gmail.com>
Date: Wed, 20 Jan 2021 00:43:06 +0900
Subject: Fix broken link in intra-doc

---
 crates/hir/src/attrs.rs        |  6 ++++++
 crates/hir_def/src/resolver.rs | 13 +++++++++++++
 crates/ide/src/doc_links.rs    | 23 ++++++++++++++++++++---
 crates/ide/src/hover.rs        | 29 +++++++++++++++++++++++++++++
 4 files changed, 68 insertions(+), 3 deletions(-)

(limited to 'crates')

diff --git a/crates/hir/src/attrs.rs b/crates/hir/src/attrs.rs
index 99fb65bac..9e6a3e155 100644
--- a/crates/hir/src/attrs.rs
+++ b/crates/hir/src/attrs.rs
@@ -2,6 +2,7 @@
 use hir_def::{
     attr::{Attrs, Documentation},
     path::ModPath,
+    per_ns::PerNs,
     resolver::HasResolver,
     AttrDefId, GenericParamId, ModuleDefId,
 };
@@ -112,6 +113,11 @@ fn resolve_doc_path(
     let path = ast::Path::parse(link).ok()?;
     let modpath = ModPath::from_src(path, &Hygiene::new_unhygienic()).unwrap();
     let resolved = resolver.resolve_module_path_in_items(db.upcast(), &modpath);
+    if resolved == PerNs::none() {
+        if let Some(trait_id) = resolver.resolve_module_path_in_trait_items(db.upcast(), &modpath) {
+            return Some(ModuleDefId::TraitId(trait_id));
+        };
+    }
     let def = match ns {
         Some(Namespace::Types) => resolved.take_types()?,
         Some(Namespace::Values) => resolved.take_values()?,
diff --git a/crates/hir_def/src/resolver.rs b/crates/hir_def/src/resolver.rs
index d48029b7d..b2f577649 100644
--- a/crates/hir_def/src/resolver.rs
+++ b/crates/hir_def/src/resolver.rs
@@ -146,6 +146,19 @@ impl Resolver {
         self.resolve_module_path(db, path, BuiltinShadowMode::Module)
     }
 
+    pub fn resolve_module_path_in_trait_items(
+        &self,
+        db: &dyn DefDatabase,
+        path: &ModPath,
+    ) -> Option<TraitId> {
+        let (item_map, module) = self.module_scope()?;
+        let (module_res, ..) = item_map.resolve_path(db, module, &path, BuiltinShadowMode::Module);
+        match module_res.take_types()? {
+            ModuleDefId::TraitId(it) => Some(it),
+            _ => None,
+        }
+    }
+
     pub fn resolve_path_in_type_ns(
         &self,
         db: &dyn DefDatabase,
diff --git a/crates/ide/src/doc_links.rs b/crates/ide/src/doc_links.rs
index 1f08d7810..730e0dd0a 100644
--- a/crates/ide/src/doc_links.rs
+++ b/crates/ide/src/doc_links.rs
@@ -221,14 +221,31 @@ fn rewrite_intra_doc_link(
     }?;
     let krate = resolved.module(db)?.krate();
     let canonical_path = resolved.canonical_path(db)?;
-    let new_target = get_doc_url(db, &krate)?
+    let mut new_url = get_doc_url(db, &krate)?
         .join(&format!("{}/", krate.display_name(db)?))
         .ok()?
         .join(&canonical_path.replace("::", "/"))
         .ok()?
         .join(&get_symbol_filename(db, &resolved)?)
-        .ok()?
-        .into_string();
+        .ok()?;
+
+    if let ModuleDef::Trait(t) = resolved {
+        let items = t.items(db);
+        if let Some(field_or_assoc_item) = items.iter().find_map(|assoc_item| {
+            if let Some(name) = assoc_item.name(db) {
+                if link.to_string() == format!("{}::{}", canonical_path, name) {
+                    return Some(FieldOrAssocItem::AssocItem(*assoc_item));
+                }
+            }
+            None
+        }) {
+            if let Some(fragment) = get_symbol_fragment(db, &field_or_assoc_item) {
+                new_url = new_url.join(&fragment).ok()?;
+            }
+        };
+    }
+
+    let new_target = new_url.into_string();
     let new_title = strip_prefixes_suffixes(title);
     Some((new_target, new_title.to_string()))
 }
diff --git a/crates/ide/src/hover.rs b/crates/ide/src/hover.rs
index ec1631486..d47a4cb0f 100644
--- a/crates/ide/src/hover.rs
+++ b/crates/ide/src/hover.rs
@@ -1826,6 +1826,35 @@ pub struct B$0ar
             "#]],
         );
     }
+    #[test]
+    fn test_hover_intra_link_reference_to_trait_method() {
+        check(
+            r#"
+pub trait Foo {
+    fn buzz() -> usize;
+}
+/// [Foo][buzz]
+///
+/// [buzz]: Foo::buzz
+pub struct B$0ar
+"#,
+            expect![[r#"
+                *Bar*
+
+                ```rust
+                test
+                ```
+
+                ```rust
+                pub struct Bar
+                ```
+
+                ---
+
+                [Foo](https://docs.rs/test/*/test/trait.Foo.html#tymethod.buzz)
+            "#]],
+        );
+    }
 
     #[test]
     fn test_hover_external_url() {
-- 
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