From cdfb5c353f09138540ae66a2eb80a6a81802bbd6 Mon Sep 17 00:00:00 2001
From: Lukas Wirth <lukastw97@gmail.com>
Date: Wed, 17 Mar 2021 11:22:40 +0100
Subject: Remove quadratic attr source lookup

---
 crates/hir_def/src/attr.rs | 25 +++++++++++++++++++++++++
 1 file changed, 25 insertions(+)

(limited to 'crates/hir_def/src')

diff --git a/crates/hir_def/src/attr.rs b/crates/hir_def/src/attr.rs
index e7019e0c9..7a6a41dc2 100644
--- a/crates/hir_def/src/attr.rs
+++ b/crates/hir_def/src/attr.rs
@@ -294,6 +294,13 @@ 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 AttrsOwner) -> AttrSourceMap {
+        AttrSourceMap { attrs: collect_attrs(owner).collect() }
+    }
+
     pub fn by_key(&self, key: &'static str) -> AttrQuery<'_> {
         AttrQuery { attrs: self, key }
     }
@@ -366,6 +373,24 @@ 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,
-- 
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