From 44f4510caa6becafc3621253e8115d94b6bd4423 Mon Sep 17 00:00:00 2001
From: Jonas Schievink <jonas.schievink@ferrous-systems.com>
Date: Wed, 16 Sep 2020 12:35:09 +0200
Subject: [PATCH] Store `Import` indices for later reconstruction

---
 crates/hir_def/src/item_tree.rs       | 6 +++++-
 crates/hir_def/src/item_tree/lower.rs | 3 ++-
 crates/hir_def/src/item_tree/tests.rs | 4 ++--
 3 files changed, 9 insertions(+), 4 deletions(-)

diff --git a/crates/hir_def/src/item_tree.rs b/crates/hir_def/src/item_tree.rs
index e14722caebb..f02cfb0c692 100644
--- a/crates/hir_def/src/item_tree.rs
+++ b/crates/hir_def/src/item_tree.rs
@@ -291,7 +291,6 @@ pub enum AttrOwner {
 
     Variant(Idx<Variant>),
     Field(Idx<Field>),
-    // FIXME: Store variant and field attrs, and stop reparsing them in `attrs_query`.
 }
 
 macro_rules! from_attrs {
@@ -483,6 +482,11 @@ pub struct Import {
     /// AST ID of the `use` or `extern crate` item this import was derived from. Note that many
     /// `Import`s can map to the same `use` item.
     pub ast_id: FileAstId<ast::Use>,
+    /// Index of this `Import` when the containing `Use` is visited via `ModPath::expand_use_item`.
+    ///
+    /// This can be used to get the `UseTree` this `Import` corresponds to and allows emitting
+    /// precise diagnostics.
+    pub index: usize,
 }
 
 #[derive(Debug, Clone, Eq, PartialEq)]
diff --git a/crates/hir_def/src/item_tree/lower.rs b/crates/hir_def/src/item_tree/lower.rs
index 6a503d7853e..9160bfafe83 100644
--- a/crates/hir_def/src/item_tree/lower.rs
+++ b/crates/hir_def/src/item_tree/lower.rs
@@ -482,7 +482,7 @@ fn lower_use(&mut self, use_item: &ast::Use) -> Vec<FileItemTreeId<Import>> {
         ModPath::expand_use_item(
             InFile::new(self.file, use_item.clone()),
             &self.hygiene,
-            |path, _tree, is_glob, alias| {
+            |path, _use_tree, is_glob, alias| {
                 imports.push(id(tree.imports.alloc(Import {
                     path,
                     alias,
@@ -490,6 +490,7 @@ fn lower_use(&mut self, use_item: &ast::Use) -> Vec<FileItemTreeId<Import>> {
                     is_glob,
                     is_prelude,
                     ast_id,
+                    index: imports.len(),
                 })));
             },
         );
diff --git a/crates/hir_def/src/item_tree/tests.rs b/crates/hir_def/src/item_tree/tests.rs
index 620e697d4a1..d26c032b714 100644
--- a/crates/hir_def/src/item_tree/tests.rs
+++ b/crates/hir_def/src/item_tree/tests.rs
@@ -228,9 +228,9 @@ union Un {
 
             top-level items:
             #[Attrs { entries: Some([Attr { path: ModPath { kind: Plain, segments: [Name(Text("attr_on_use"))] }, input: None }]) }]
-            Import { path: ModPath { kind: Plain, segments: [Name(Text("a"))] }, alias: None, visibility: RawVisibilityId("pub(self)"), is_glob: false, is_prelude: false, ast_id: FileAstId::<syntax::ast::generated::nodes::Use>(0) }
+            Import { path: ModPath { kind: Plain, segments: [Name(Text("a"))] }, alias: None, visibility: RawVisibilityId("pub(self)"), is_glob: false, is_prelude: false, ast_id: FileAstId::<syntax::ast::generated::nodes::Use>(0), index: 0 }
             #[Attrs { entries: Some([Attr { path: ModPath { kind: Plain, segments: [Name(Text("attr_on_use"))] }, input: None }]) }]
-            Import { path: ModPath { kind: Plain, segments: [Name(Text("b"))] }, alias: None, visibility: RawVisibilityId("pub(self)"), is_glob: true, is_prelude: false, ast_id: FileAstId::<syntax::ast::generated::nodes::Use>(0) }
+            Import { path: ModPath { kind: Plain, segments: [Name(Text("b"))] }, alias: None, visibility: RawVisibilityId("pub(self)"), is_glob: true, is_prelude: false, ast_id: FileAstId::<syntax::ast::generated::nodes::Use>(0), index: 1 }
             #[Attrs { entries: Some([Attr { path: ModPath { kind: Plain, segments: [Name(Text("ext_crate"))] }, input: None }]) }]
             ExternCrate { path: ModPath { kind: Plain, segments: [Name(Text("krate"))] }, alias: None, visibility: RawVisibilityId("pub(self)"), is_macro_use: false, ast_id: FileAstId::<syntax::ast::generated::nodes::ExternCrate>(1) }
             #[Attrs { entries: Some([Attr { path: ModPath { kind: Plain, segments: [Name(Text("on_trait"))] }, input: None }]) }]