1 files changed, 93 insertions, 53 deletions

diff --git a/crates/hir_def/src/attr.rs b/crates/hir_def/src/attr.rs
index b0b4b5052..e4c84afbf 100644
--- a/crates/hir_def/src/attr.rs
+++ b/crates/hir_def/src/attr.rs
@@ -76,37 +76,23 @@ impl ops::Deref for Attrs {
 impl RawAttrs {
     pub(crate) const EMPTY: Self = Self { entries: None };
 
-    pub(crate) fn new(owner: &dyn AttrsOwner, hygiene: &Hygiene) -> Self {
-        let attrs: Vec<_> = collect_attrs(owner).collect();
-        let entries = if attrs.is_empty() {
-            // Avoid heap allocation
-            None
-        } else {
-            Some(
-                attrs
-                    .into_iter()
-                    .enumerate()
-                    .flat_map(|(i, attr)| match attr {
-                        Either::Left(attr) => Attr::from_src(attr, hygiene).map(|attr| (i, attr)),
-                        Either::Right(comment) => comment.doc_comment().map(|doc| {
-                            (
-                                i,
-                                Attr {
-                                    index: 0,
-                                    input: Some(AttrInput::Literal(SmolStr::new(doc))),
-                                    path: ModPath::from(hir_expand::name!(doc)),
-                                },
-                            )
-                        }),
-                    })
-                    .map(|(i, attr)| Attr { index: i as u32, ..attr })
-                    .collect(),
-            )
-        };
-        Self { entries }
+    pub(crate) fn new(owner: &dyn ast::AttrsOwner, hygiene: &Hygiene) -> Self {
+        let entries = collect_attrs(owner)
+            .enumerate()
+            .flat_map(|(i, attr)| match attr {
+                Either::Left(attr) => Attr::from_src(attr, hygiene, i as u32),
+                Either::Right(comment) => comment.doc_comment().map(|doc| Attr {
+                    index: i as u32,
+                    input: Some(AttrInput::Literal(SmolStr::new(doc))),
+                    path: ModPath::from(hir_expand::name!(doc)),
+                }),
+            })
+            .collect::<Arc<_>>();
+
+        Self { entries: if entries.is_empty() { None } else { Some(entries) } }
     }
 
-    fn from_attrs_owner(db: &dyn DefDatabase, owner: InFile<&dyn AttrsOwner>) -> Self {
+    fn from_attrs_owner(db: &dyn DefDatabase, owner: InFile<&dyn ast::AttrsOwner>) -> Self {
         let hygiene = Hygiene::new(db.upcast(), owner.file_id);
         Self::new(owner.value, &hygiene)
     }
@@ -136,16 +122,15 @@ impl RawAttrs {
         let new_attrs = self
             .iter()
             .flat_map(|attr| -> SmallVec<[_; 1]> {
-                let attr = attr.clone();
                 let is_cfg_attr =
                     attr.path.as_ident().map_or(false, |name| *name == hir_expand::name![cfg_attr]);
                 if !is_cfg_attr {
-                    return smallvec![attr];
+                    return smallvec![attr.clone()];
                 }
 
                 let subtree = match &attr.input {
                     Some(AttrInput::TokenTree(it)) => it,
-                    _ => return smallvec![attr],
+                    _ => return smallvec![attr.clone()],
                 };
 
                 // Input subtree is: `(cfg, $(attr),+)`
@@ -157,11 +142,13 @@ impl RawAttrs {
                 let cfg = parts.next().unwrap();
                 let cfg = Subtree { delimiter: subtree.delimiter, token_trees: cfg.to_vec() };
                 let cfg = CfgExpr::parse(&cfg);
+                let index = attr.index;
                 let attrs = parts.filter(|a| !a.is_empty()).filter_map(|attr| {
                     let tree = Subtree { delimiter: None, token_trees: attr.to_vec() };
                     let attr = ast::Attr::parse(&format!("#[{}]", tree)).ok()?;
-                    let hygiene = Hygiene::new_unhygienic(); // FIXME
-                    Attr::from_src(attr, &hygiene)
+                    // FIXME hygiene
+                    let hygiene = Hygiene::new_unhygienic();
+                    Attr::from_src(attr, &hygiene, index)
                 });
 
                 let cfg_options = &crate_graph[krate].cfg_options;
@@ -191,7 +178,7 @@ impl Attrs {
                     Some(it) => {
                         let raw_attrs = RawAttrs::from_attrs_owner(
                             db,
-                            it.as_ref().map(|it| it as &dyn AttrsOwner),
+                            it.as_ref().map(|it| it as &dyn ast::AttrsOwner),
                         );
                         match mod_data.definition_source(db) {
                             InFile { file_id, value: ModuleSource::SourceFile(file) } => raw_attrs
@@ -202,9 +189,9 @@ impl Attrs {
                     None => RawAttrs::from_attrs_owner(
                         db,
                         mod_data.definition_source(db).as_ref().map(|src| match src {
-                            ModuleSource::SourceFile(file) => file as &dyn AttrsOwner,
-                            ModuleSource::Module(module) => module as &dyn AttrsOwner,
-                            ModuleSource::BlockExpr(block) => block as &dyn AttrsOwner,
+                            ModuleSource::SourceFile(file) => file as &dyn ast::AttrsOwner,
+                            ModuleSource::Module(module) => module as &dyn ast::AttrsOwner,
+                            ModuleSource::BlockExpr(block) => block as &dyn ast::AttrsOwner,
                         }),
                     ),
                 }
@@ -262,7 +249,7 @@ impl Attrs {
         let mut res = ArenaMap::default();
 
         for (id, var) in src.value.iter() {
-            let attrs = RawAttrs::from_attrs_owner(db, src.with_value(var as &dyn AttrsOwner))
+            let attrs = RawAttrs::from_attrs_owner(db, src.with_value(var as &dyn ast::AttrsOwner))
                 .filter(db, krate);
 
             res.insert(id, attrs)
@@ -293,6 +280,13 @@ impl Attrs {
         Arc::new(res)
     }
 
+    /// Constructs a map that maps the lowered `Attr`s in this `Attrs` back to its original syntax nodes.
+    ///
+    /// `owner` must be the original owner of the attributes.
+    pub fn source_map(&self, owner: &dyn ast::AttrsOwner) -> AttrSourceMap {
+        AttrSourceMap { attrs: collect_attrs(owner).collect() }
+    }
+
     pub fn by_key(&self, key: &'static str) -> AttrQuery<'_> {
         AttrQuery { attrs: self, key }
     }
@@ -317,15 +311,34 @@ impl Attrs {
             AttrInput::Literal(s) => Some(s),
             AttrInput::TokenTree(_) => None,
         });
-        // FIXME: Replace `Itertools::intersperse` with `Iterator::intersperse[_with]` until the
-        // libstd api gets stabilized (https://github.com/rust-lang/rust/issues/79524).
-        let docs = Itertools::intersperse(docs, &SmolStr::new_inline("\n"))
-            .map(|it| it.as_str())
-            .collect::<String>();
-        if docs.is_empty() {
+        let indent = docs
+            .clone()
+            .flat_map(|s| s.lines())
+            .filter(|line| !line.chars().all(|c| c.is_whitespace()))
+            .map(|line| line.chars().take_while(|c| c.is_whitespace()).count())
+            .min()
+            .unwrap_or(0);
+        let mut buf = String::new();
+        for doc in docs {
+            // str::lines doesn't yield anything for the empty string
+            if !doc.is_empty() {
+                buf.extend(Itertools::intersperse(
+                    doc.lines().map(|line| {
+                        line.char_indices()
+                            .nth(indent)
+                            .map_or(line, |(offset, _)| &line[offset..])
+                            .trim_end()
+                    }),
+                    "\n",
+                ));
+            }
+            buf.push('\n');
+        }
+        buf.pop();
+        if buf.is_empty() {
             None
         } else {
-            Some(Documentation(docs))
+            Some(Documentation(buf))
         }
     }
 }
@@ -365,6 +378,24 @@ fn inner_attributes(
     Some((attrs, docs))
 }
 
+pub struct AttrSourceMap {
+    attrs: Vec<Either<ast::Attr, ast::Comment>>,
+}
+
+impl AttrSourceMap {
+    /// Maps the lowered `Attr` back to its original syntax node.
+    ///
+    /// `attr` must come from the `owner` used for AttrSourceMap
+    ///
+    /// Note that the returned syntax node might be a `#[cfg_attr]`, or a doc comment, instead of
+    /// the attribute represented by `Attr`.
+    pub fn source_of(&self, attr: &Attr) -> &Either<ast::Attr, ast::Comment> {
+        self.attrs
+            .get(attr.index as usize)
+            .unwrap_or_else(|| panic!("cannot find `Attr` at index {}", attr.index))
+    }
+}
+
 #[derive(Debug, Clone, PartialEq, Eq)]
 pub struct Attr {
     index: u32,
@@ -381,7 +412,7 @@ pub enum AttrInput {
 }
 
 impl Attr {
-    fn from_src(ast: ast::Attr, hygiene: &Hygiene) -> Option<Attr> {
+    fn from_src(ast: ast::Attr, hygiene: &Hygiene, index: u32) -> Option<Attr> {
         let path = ModPath::from_src(ast.path()?, hygiene)?;
         let input = if let Some(lit) = ast.literal() {
             let value = match lit.kind() {
@@ -394,7 +425,7 @@ impl Attr {
         } else {
             None
         };
-        Some(Attr { index: 0, path, input })
+        Some(Attr { index, path, input })
     }
 
     /// Maps this lowered `Attr` back to its original syntax node.
@@ -403,7 +434,7 @@ impl Attr {
     ///
     /// Note that the returned syntax node might be a `#[cfg_attr]`, or a doc comment, instead of
     /// the attribute represented by `Attr`.
-    pub fn to_src(&self, owner: &dyn AttrsOwner) -> Either<ast::Attr, ast::Comment> {
+    pub fn to_src(&self, owner: &dyn ast::AttrsOwner) -> Either<ast::Attr, ast::Comment> {
         collect_attrs(owner).nth(self.index as usize).unwrap_or_else(|| {
             panic!("cannot find `Attr` at index {} in {}", self.index, owner.syntax())
         })
@@ -448,6 +479,13 @@ impl Attr {
             _ => None,
         }
     }
+
+    pub fn string_value(&self) -> Option<&SmolStr> {
+        match self.input.as_ref()? {
+            AttrInput::Literal(it) => Some(it),
+            _ => None,
+        }
+    }
 }
 
 #[derive(Debug, Clone, Copy)]
@@ -475,7 +513,7 @@ impl<'a> AttrQuery<'a> {
         self.attrs().next().is_some()
     }
 
-    pub(crate) fn attrs(self) -> impl Iterator<Item = &'a Attr> {
+    pub fn attrs(self) -> impl Iterator<Item = &'a Attr> + Clone {
         let key = self.key;
         self.attrs
             .iter()
@@ -488,16 +526,18 @@ where
     N: ast::AttrsOwner,
 {
     let src = InFile::new(src.file_id, src.to_node(db.upcast()));
-    RawAttrs::from_attrs_owner(db, src.as_ref().map(|it| it as &dyn AttrsOwner))
+    RawAttrs::from_attrs_owner(db, src.as_ref().map(|it| it as &dyn ast::AttrsOwner))
 }
 
 fn attrs_from_item_tree<N: ItemTreeNode>(id: ItemTreeId<N>, db: &dyn DefDatabase) -> RawAttrs {
-    let tree = db.item_tree(id.file_id);
+    let tree = id.item_tree(db);
     let mod_item = N::id_to_mod_item(id.value);
     tree.raw_attrs(mod_item.into()).clone()
 }
 
-fn collect_attrs(owner: &dyn AttrsOwner) -> impl Iterator<Item = Either<ast::Attr, ast::Comment>> {
+fn collect_attrs(
+    owner: &dyn ast::AttrsOwner,
+) -> impl Iterator<Item = Either<ast::Attr, ast::Comment>> {
     let (inner_attrs, inner_docs) = inner_attributes(owner.syntax())
         .map_or((None, None), |(attrs, docs)| ((Some(attrs), Some(docs))));