Show item info when hovering intra doc links

6 files changed, 175 insertions, 128 deletions

diff --git a/crates/ide/src/call_hierarchy.rs b/crates/ide/src/call_hierarchy.rs
index 96021f677..5cd186565 100644
--- a/crates/ide/src/call_hierarchy.rs
+++ b/crates/ide/src/call_hierarchy.rs
@@ -50,16 +50,16 @@ pub(crate) fn incoming_calls(db: &RootDatabase, position: FilePosition) -> Optio
     for (file_id, references) in refs.references {
         let file = sema.parse(file_id);
         let file = file.syntax();
-        for (r_range, _) in references {
-            let token = file.token_at_offset(r_range.start()).next()?;
+        for (relative_range, token) in references
+            .into_iter()
+            .filter_map(|(range, _)| Some(range).zip(file.token_at_offset(range.start()).next()))
+        {
             let token = sema.descend_into_macros(token);
             // This target is the containing function
             if let Some(nav) = token.ancestors().find_map(|node| {
-                let fn_ = ast::Fn::cast(node)?;
-                let def = sema.to_def(&fn_)?;
+                let def = ast::Fn::cast(node).and_then(|fn_| sema.to_def(&fn_))?;
                 def.try_to_nav(sema.db)
             }) {
-                let relative_range = r_range;
                 calls.add(&nav, relative_range);
             }
         }
@@ -87,7 +87,6 @@ pub(crate) fn outgoing_calls(db: &RootDatabase, position: FilePosition) -> Optio
             let name_ref = call_node.name_ref()?;
             let func_target = match call_node {
                 FnCallNode::CallExpr(expr) => {
-                    //FIXME: Type::as_callable is broken
                     let callable = sema.type_of_expr(&expr.expr()?)?.as_callable(db)?;
                     match callable.kind() {
                         hir::CallableKind::Function(it) => it.try_to_nav(db),
diff --git a/crates/ide/src/doc_links.rs b/crates/ide/src/doc_links.rs
index c7c1f4fee..f12c9d442 100644
--- a/crates/ide/src/doc_links.rs
+++ b/crates/ide/src/doc_links.rs
@@ -1,4 +1,4 @@
-//! Resolves and rewrites links in markdown documentation.
+//! Extracts, resolves and rewrites links and intra-doc links in markdown documentation.
 
 use std::{convert::TryFrom, iter::once, ops::Range};
 
@@ -15,7 +15,10 @@ use ide_db::{
     defs::{Definition, NameClass, NameRefClass},
     RootDatabase,
 };
-use syntax::{ast, match_ast, AstNode, SyntaxKind::*, SyntaxToken, TokenAtOffset, T};
+use syntax::{
+    ast, match_ast, AstNode, AstToken, SyntaxKind::*, SyntaxNode, SyntaxToken, TextRange, TextSize,
+    TokenAtOffset, T,
+};
 
 use crate::{FilePosition, Semantics};
 
@@ -60,29 +63,6 @@ pub(crate) fn rewrite_links(db: &RootDatabase, markdown: &str, definition: &Defi
     out
 }
 
-pub(crate) fn extract_definitions_from_markdown(
-    markdown: &str,
-) -> Vec<(String, Option<hir::Namespace>, Range<usize>)> {
-    let mut res = vec![];
-    let mut cb = |link: BrokenLink| {
-        // These allocations are actually unnecessary but the lifetimes on BrokenLinkCallback are wrong
-        // this is fixed in the repo but not on the crates.io release yet
-        Some((
-            /*url*/ link.reference.to_owned().into(),
-            /*title*/ link.reference.to_owned().into(),
-        ))
-    };
-    let doc = Parser::new_with_broken_link_callback(markdown, Options::empty(), Some(&mut cb));
-    for (event, range) in doc.into_offset_iter() {
-        if let Event::Start(Tag::Link(_, target, title)) = event {
-            let link = if target.is_empty() { title } else { target };
-            let (link, ns) = parse_link(&link);
-            res.push((link.to_string(), ns, range));
-        }
-    }
-    res
-}
-
 /// Remove all links in markdown documentation.
 pub(crate) fn remove_links(markdown: &str) -> String {
     let mut drop_link = false;
@@ -118,6 +98,105 @@ pub(crate) fn remove_links(markdown: &str) -> String {
     out
 }
 
+pub(crate) fn extract_definitions_from_markdown(
+    markdown: &str,
+) -> Vec<(Range<usize>, String, Option<hir::Namespace>)> {
+    let mut res = vec![];
+    let mut cb = |link: BrokenLink| {
+        // These allocations are actually unnecessary but the lifetimes on BrokenLinkCallback are wrong
+        // this is fixed in the repo but not on the crates.io release yet
+        Some((
+            /*url*/ link.reference.to_owned().into(),
+            /*title*/ link.reference.to_owned().into(),
+        ))
+    };
+    let doc = Parser::new_with_broken_link_callback(markdown, Options::empty(), Some(&mut cb));
+    for (event, range) in doc.into_offset_iter() {
+        if let Event::Start(Tag::Link(_, target, title)) = event {
+            let link = if target.is_empty() { title } else { target };
+            let (link, ns) = parse_link(&link);
+            res.push((range, link.to_string(), ns));
+        }
+    }
+    res
+}
+
+/// Extracts a link from a comment at the given position returning the spanning range, link and
+/// optionally it's namespace.
+pub(crate) fn extract_positioned_link_from_comment(
+    position: TextSize,
+    comment: &ast::Comment,
+) -> Option<(TextRange, String, Option<hir::Namespace>)> {
+    let doc_comment = comment.doc_comment()?;
+    let comment_start =
+        comment.syntax().text_range().start() + TextSize::from(comment.prefix().len() as u32);
+    let def_links = extract_definitions_from_markdown(doc_comment);
+    let (range, def_link, ns) =
+        def_links.into_iter().find_map(|(Range { start, end }, def_link, ns)| {
+            let range = TextRange::at(
+                comment_start + TextSize::from(start as u32),
+                TextSize::from((end - start) as u32),
+            );
+            range.contains(position).then(|| (range, def_link, ns))
+        })?;
+    Some((range, def_link, ns))
+}
+
+/// Turns a syntax node into it's [`Definition`] if it can hold docs.
+pub(crate) fn doc_owner_to_def(
+    sema: &Semantics<RootDatabase>,
+    item: &SyntaxNode,
+) -> Option<Definition> {
+    let res: hir::ModuleDef = match_ast! {
+        match item {
+            ast::SourceFile(_it) => sema.scope(item).module()?.into(),
+            ast::Fn(it) => sema.to_def(&it)?.into(),
+            ast::Struct(it) => sema.to_def(&it)?.into(),
+            ast::Enum(it) => sema.to_def(&it)?.into(),
+            ast::Union(it) => sema.to_def(&it)?.into(),
+            ast::Trait(it) => sema.to_def(&it)?.into(),
+            ast::Const(it) => sema.to_def(&it)?.into(),
+            ast::Static(it) => sema.to_def(&it)?.into(),
+            ast::TypeAlias(it) => sema.to_def(&it)?.into(),
+            ast::Variant(it) => sema.to_def(&it)?.into(),
+            ast::Trait(it) => sema.to_def(&it)?.into(),
+            ast::Impl(it) => return sema.to_def(&it).map(Definition::SelfType),
+            ast::MacroRules(it) => return sema.to_def(&it).map(Definition::Macro),
+            ast::TupleField(it) => return sema.to_def(&it).map(Definition::Field),
+            ast::RecordField(it) => return sema.to_def(&it).map(Definition::Field),
+            _ => return None,
+        }
+    };
+    Some(Definition::ModuleDef(res))
+}
+
+pub(crate) fn resolve_doc_path_for_def(
+    db: &dyn HirDatabase,
+    def: Definition,
+    link: &str,
+    ns: Option<hir::Namespace>,
+) -> Option<hir::ModuleDef> {
+    match def {
+        Definition::ModuleDef(def) => match def {
+            ModuleDef::Module(it) => it.resolve_doc_path(db, &link, ns),
+            ModuleDef::Function(it) => it.resolve_doc_path(db, &link, ns),
+            ModuleDef::Adt(it) => it.resolve_doc_path(db, &link, ns),
+            ModuleDef::Variant(it) => it.resolve_doc_path(db, &link, ns),
+            ModuleDef::Const(it) => it.resolve_doc_path(db, &link, ns),
+            ModuleDef::Static(it) => it.resolve_doc_path(db, &link, ns),
+            ModuleDef::Trait(it) => it.resolve_doc_path(db, &link, ns),
+            ModuleDef::TypeAlias(it) => it.resolve_doc_path(db, &link, ns),
+            ModuleDef::BuiltinType(_) => None,
+        },
+        Definition::Macro(it) => it.resolve_doc_path(db, &link, ns),
+        Definition::Field(it) => it.resolve_doc_path(db, &link, ns),
+        Definition::SelfType(_)
+        | Definition::Local(_)
+        | Definition::GenericParam(_)
+        | Definition::Label(_) => None,
+    }
+}
+
 // FIXME:
 // BUG: For Option::Some
 // Returns https://doc.rust-lang.org/nightly/core/prelude/v1/enum.Option.html#variant.Some
diff --git a/crates/ide/src/goto_definition.rs b/crates/ide/src/goto_definition.rs
index 473d48c2f..a2c97061f 100644
--- a/crates/ide/src/goto_definition.rs
+++ b/crates/ide/src/goto_definition.rs
@@ -1,18 +1,14 @@
-use std::ops::Range;
-
 use either::Either;
-use hir::{HasAttrs, ModuleDef, Semantics};
+use hir::Semantics;
 use ide_db::{
-    defs::{Definition, NameClass, NameRefClass},
+    defs::{NameClass, NameRefClass},
     RootDatabase,
 };
-use syntax::{
-    ast, match_ast, AstNode, AstToken, SyntaxKind::*, SyntaxToken, TextRange, TextSize,
-    TokenAtOffset, T,
-};
+use syntax::{ast, match_ast, AstNode, AstToken, SyntaxKind::*, SyntaxToken, TokenAtOffset, T};
 
 use crate::{
-    display::TryToNav, doc_links::extract_definitions_from_markdown, runnables::doc_owner_to_def,
+    display::TryToNav,
+    doc_links::{doc_owner_to_def, extract_positioned_link_from_comment, resolve_doc_path_for_def},
     FilePosition, NavigationTarget, RangeInfo,
 };
 
@@ -35,7 +31,9 @@ pub(crate) fn goto_definition(
     let token = sema.descend_into_macros(original_token.clone());
     let parent = token.parent()?;
     if let Some(comment) = ast::Comment::cast(token) {
-        let nav = def_for_doc_comment(&sema, position, &comment)?.try_to_nav(db)?;
+        let (_, link, ns) = extract_positioned_link_from_comment(position.offset, &comment)?;
+        let def = doc_owner_to_def(&sema, &parent)?;
+        let nav = resolve_doc_path_for_def(db, def, &link, ns)?.try_to_nav(db)?;
         return Some(RangeInfo::new(original_token.text_range(), vec![nav]));
     }
 
@@ -61,54 +59,6 @@ pub(crate) fn goto_definition(
     Some(RangeInfo::new(original_token.text_range(), nav.into_iter().collect()))
 }
 
-fn def_for_doc_comment(
-    sema: &Semantics<RootDatabase>,
-    position: FilePosition,
-    doc_comment: &ast::Comment,
-) -> Option<hir::ModuleDef> {
-    let parent = doc_comment.syntax().parent()?;
-    let (link, ns) = extract_positioned_link_from_comment(position, doc_comment)?;
-
-    let def = doc_owner_to_def(sema, parent)?;
-    match def {
-        Definition::ModuleDef(def) => match def {
-            ModuleDef::Module(it) => it.resolve_doc_path(sema.db, &link, ns),
-            ModuleDef::Function(it) => it.resolve_doc_path(sema.db, &link, ns),
-            ModuleDef::Adt(it) => it.resolve_doc_path(sema.db, &link, ns),
-            ModuleDef::Variant(it) => it.resolve_doc_path(sema.db, &link, ns),
-            ModuleDef::Const(it) => it.resolve_doc_path(sema.db, &link, ns),
-            ModuleDef::Static(it) => it.resolve_doc_path(sema.db, &link, ns),
-            ModuleDef::Trait(it) => it.resolve_doc_path(sema.db, &link, ns),
-            ModuleDef::TypeAlias(it) => it.resolve_doc_path(sema.db, &link, ns),
-            ModuleDef::BuiltinType(_) => return None,
-        },
-        Definition::Macro(it) => it.resolve_doc_path(sema.db, &link, ns),
-        Definition::Field(it) => it.resolve_doc_path(sema.db, &link, ns),
-        Definition::SelfType(_)
-        | Definition::Local(_)
-        | Definition::GenericParam(_)
-        | Definition::Label(_) => return None,
-    }
-}
-
-fn extract_positioned_link_from_comment(
-    position: FilePosition,
-    comment: &ast::Comment,
-) -> Option<(String, Option<hir::Namespace>)> {
-    let doc_comment = comment.doc_comment()?;
-    let comment_start =
-        comment.syntax().text_range().start() + TextSize::from(comment.prefix().len() as u32);
-    let def_links = extract_definitions_from_markdown(doc_comment);
-    let (def_link, ns, _) = def_links.into_iter().find(|&(_, _, Range { start, end })| {
-        TextRange::at(
-            comment_start + TextSize::from(start as u32),
-            TextSize::from((end - start) as u32),
-        )
-        .contains(position.offset)
-    })?;
-    Some((def_link, ns))
-}
-
 fn pick_best(tokens: TokenAtOffset<SyntaxToken>) -> Option<SyntaxToken> {
     return tokens.max_by_key(priority);
     fn priority(n: &SyntaxToken) -> usize {
diff --git a/crates/ide/src/hover.rs b/crates/ide/src/hover.rs
index a3fb17c0a..c43089476 100644
--- a/crates/ide/src/hover.rs
+++ b/crates/ide/src/hover.rs
@@ -11,11 +11,14 @@ use ide_db::{
 };
 use itertools::Itertools;
 use stdx::format_to;
-use syntax::{ast, match_ast, AstNode, SyntaxKind::*, SyntaxToken, TokenAtOffset, T};
+use syntax::{ast, match_ast, AstNode, AstToken, SyntaxKind::*, SyntaxToken, TokenAtOffset, T};
 
 use crate::{
     display::{macro_label, TryToNav},
-    doc_links::{remove_links, rewrite_links},
+    doc_links::{
+        doc_owner_to_def, extract_positioned_link_from_comment, remove_links,
+        resolve_doc_path_for_def, rewrite_links,
+    },
     markdown_remove::remove_markdown,
     markup::Markup,
     runnables::{runnable_fn, runnable_mod},
@@ -93,20 +96,35 @@ pub(crate) fn hover(
     let mut res = HoverResult::default();
 
     let node = token.parent()?;
+    let mut range = None;
     let definition = match_ast! {
         match node {
             // we don't use NameClass::referenced_or_defined here as we do not want to resolve
             // field pattern shorthands to their definition
             ast::Name(name) => NameClass::classify(&sema, &name).and_then(|class| match class {
                 NameClass::ConstReference(def) => Some(def),
-                def => def.defined(sema.db),
+                def => def.defined(db),
             }),
-            ast::NameRef(name_ref) => NameRefClass::classify(&sema, &name_ref).map(|d| d.referenced(sema.db)),
-            ast::Lifetime(lifetime) => NameClass::classify_lifetime(&sema, &lifetime)
-                .map_or_else(|| NameRefClass::classify_lifetime(&sema, &lifetime).map(|d| d.referenced(sema.db)), |d| d.defined(sema.db)),
-            _ => None,
+            ast::NameRef(name_ref) => {
+                NameRefClass::classify(&sema, &name_ref).map(|d| d.referenced(db))
+            },
+            ast::Lifetime(lifetime) => NameClass::classify_lifetime(&sema, &lifetime).map_or_else(
+                || NameRefClass::classify_lifetime(&sema, &lifetime).map(|d| d.referenced(db)),
+                |d| d.defined(db),
+            ),
+
+            _ => ast::Comment::cast(token.clone())
+                .and_then(|comment| {
+                    let (idl_range, link, ns) =
+                        extract_positioned_link_from_comment(position.offset, &comment)?;
+                    range = Some(idl_range);
+                    let def = doc_owner_to_def(&sema, &node)?;
+                    resolve_doc_path_for_def(db, def, &link, ns)
+                })
+                .map(Definition::ModuleDef),
         }
     };
+
     if let Some(definition) = definition {
         let famous_defs = match &definition {
             Definition::ModuleDef(ModuleDef::BuiltinType(_)) => {
@@ -128,15 +146,16 @@ pub(crate) fn hover(
                 res.actions.push(action);
             }
 
-            let range = sema.original_range(&node).range;
+            let range = range.unwrap_or_else(|| sema.original_range(&node).range);
             return Some(RangeInfo::new(range, res));
         }
     }
 
     if token.kind() == syntax::SyntaxKind::COMMENT {
-        // don't highlight the entire parent node on comment hover
+        cov_mark::hit!(no_highlight_on_comment_hover);
         return None;
     }
+
     if let res @ Some(_) = hover_for_keyword(&sema, links_in_hover, markdown, &token) {
         return res;
     }
@@ -3483,6 +3502,7 @@ fn foo$0() {}
 
     #[test]
     fn hover_comments_dont_highlight_parent() {
+        cov_mark::check!(no_highlight_on_comment_hover);
         check_hover_no_result(
             r#"
 fn no_hover() {
@@ -3755,4 +3775,29 @@ fn main() {
             "#]],
         )
     }
+
+    #[test]
+    fn hover_intra_doc_links() {
+        check(
+            r#"
+/// This is the [`foo`](foo$0) function.
+fn foo() {}
+"#,
+            expect![[r#"
+                *[`foo`](foo)*
+
+                ```rust
+                test
+                ```
+
+                ```rust
+                fn foo()
+                ```
+
+                ---
+
+                This is the [`foo`](https://docs.rs/test/*/test/fn.foo.html) function.
+            "#]],
+        );
+    }
 }
diff --git a/crates/ide/src/runnables.rs b/crates/ide/src/runnables.rs
index bea020b06..5b488e2c5 100644
--- a/crates/ide/src/runnables.rs
+++ b/crates/ide/src/runnables.rs
@@ -7,17 +7,13 @@ use hir::{AsAssocItem, HasAttrs, HasSource, HirDisplay, Semantics};
 use ide_assists::utils::test_related_attribute;
 use ide_db::{
     base_db::{FilePosition, FileRange},
-    defs::Definition,
     helpers::visit_file_defs,
     search::SearchScope,
     RootDatabase, SymbolKind,
 };
 use itertools::Itertools;
 use rustc_hash::FxHashSet;
-use syntax::{
-    ast::{self, AstNode, AttrsOwner},
-    match_ast, SyntaxNode,
-};
+use syntax::ast::{self, AstNode, AttrsOwner};
 
 use crate::{
     display::{ToNav, TryToNav},
@@ -271,28 +267,6 @@ pub(crate) fn runnable_mod(sema: &Semantics<RootDatabase>, def: hir::Module) ->
     Some(Runnable { nav, kind: RunnableKind::TestMod { path }, cfg })
 }
 
-// FIXME: figure out a proper API here.
-pub(crate) fn doc_owner_to_def(
-    sema: &Semantics<RootDatabase>,
-    item: SyntaxNode,
-) -> Option<Definition> {
-    let res: hir::ModuleDef = match_ast! {
-        match item {
-            ast::SourceFile(_it) => sema.scope(&item).module()?.into(),
-            ast::Fn(it) => sema.to_def(&it)?.into(),
-            ast::Struct(it) => sema.to_def(&it)?.into(),
-            ast::Enum(it) => sema.to_def(&it)?.into(),
-            ast::Union(it) => sema.to_def(&it)?.into(),
-            ast::Trait(it) => sema.to_def(&it)?.into(),
-            ast::Const(it) => sema.to_def(&it)?.into(),
-            ast::Static(it) => sema.to_def(&it)?.into(),
-            ast::TypeAlias(it) => sema.to_def(&it)?.into(),
-            _ => return None,
-        }
-    };
-    Some(Definition::ModuleDef(res))
-}
-
 fn module_def_doctest(sema: &Semantics<RootDatabase>, def: hir::ModuleDef) -> Option<Runnable> {
     let attrs = match def {
         hir::ModuleDef::Module(it) => it.attrs(sema.db),
diff --git a/crates/ide/src/syntax_highlighting/inject.rs b/crates/ide/src/syntax_highlighting/inject.rs
index 8e0940184..38bf49348 100644
--- a/crates/ide/src/syntax_highlighting/inject.rs
+++ b/crates/ide/src/syntax_highlighting/inject.rs
@@ -190,10 +190,10 @@ pub(super) fn doc_comment(
                     intra_doc_links.extend(
                         extract_definitions_from_markdown(line)
                             .into_iter()
-                            .filter_map(|(link, ns, range)| {
-                                validate_intra_doc_link(sema.db, &def, &link, ns).zip(Some(range))
+                            .filter_map(|(range, link, ns)| {
+                                Some(range).zip(validate_intra_doc_link(sema.db, &def, &link, ns))
                             })
-                            .map(|(def, Range { start, end })| {
+                            .map(|(Range { start, end }, def)| {
                                 (
                                     def,
                                     TextRange::at(