From 06f7ca307d7ffdbdafe05eb76cc850eaf716916d Mon Sep 17 00:00:00 2001
From: Camille GILLOT <gillot.camille@gmail.com>
Date: Sun, 4 Apr 2021 16:04:38 +0200
Subject: [PATCH] Keep def_spans collected by resolution.

---
 compiler/rustc_hir/src/definitions.rs | 20 +++++++++++++++++++-
 compiler/rustc_resolve/src/lib.rs     | 13 +++----------
 2 files changed, 22 insertions(+), 11 deletions(-)

diff --git a/compiler/rustc_hir/src/definitions.rs b/compiler/rustc_hir/src/definitions.rs
index 30a367052cb..ada012b6697 100644
--- a/compiler/rustc_hir/src/definitions.rs
+++ b/compiler/rustc_hir/src/definitions.rs
@@ -14,6 +14,7 @@ use rustc_data_structures::unhash::UnhashMap;
 use rustc_index::vec::IndexVec;
 use rustc_span::hygiene::ExpnId;
 use rustc_span::symbol::{kw, sym, Symbol};
+use rustc_span::Span;
 
 use std::fmt::{self, Write};
 use std::hash::Hash;
@@ -107,6 +108,8 @@ pub struct Definitions {
 
     /// Item with a given `LocalDefId` was defined during macro expansion with ID `ExpnId`.
     expansions_that_defined: FxHashMap<LocalDefId, ExpnId>,
+
+    def_id_to_span: IndexVec<LocalDefId, Span>,
 }
 
 /// A unique identifier that we can use to lookup a definition
@@ -324,7 +327,7 @@ impl Definitions {
     }
 
     /// Adds a root definition (no parent) and a few other reserved definitions.
-    pub fn new(stable_crate_id: StableCrateId) -> Definitions {
+    pub fn new(stable_crate_id: StableCrateId, crate_span: Span) -> Definitions {
         let key = DefKey {
             parent: None,
             disambiguated_data: DisambiguatedDefPathData {
@@ -341,11 +344,16 @@ impl Definitions {
         let root = LocalDefId { local_def_index: table.allocate(key, def_path_hash) };
         assert_eq!(root.local_def_index, CRATE_DEF_INDEX);
 
+        let mut def_id_to_span = IndexVec::new();
+        let _root = def_id_to_span.push(crate_span);
+        debug_assert_eq!(_root, root);
+
         Definitions {
             table,
             def_id_to_hir_id: Default::default(),
             hir_id_to_def_id: Default::default(),
             expansions_that_defined: Default::default(),
+            def_id_to_span,
         }
     }
 
@@ -361,6 +369,7 @@ impl Definitions {
         data: DefPathData,
         expn_id: ExpnId,
         mut next_disambiguator: impl FnMut(LocalDefId, DefPathData) -> u32,
+        span: Span,
     ) -> LocalDefId {
         debug!("create_def(parent={:?}, data={:?}, expn_id={:?})", parent, data, expn_id);
 
@@ -385,6 +394,9 @@ impl Definitions {
             self.expansions_that_defined.insert(def_id, expn_id);
         }
 
+        let _id = self.def_id_to_span.push(span);
+        debug_assert_eq!(_id, def_id);
+
         def_id
     }
 
@@ -412,6 +424,12 @@ impl Definitions {
         self.expansions_that_defined.get(&id).copied().unwrap_or_else(ExpnId::root)
     }
 
+    /// Retrieves the span of the given `DefId` if `DefId` is in the local crate.
+    #[inline]
+    pub fn def_span(&self, def_id: LocalDefId) -> Span {
+        self.def_id_to_span[def_id]
+    }
+
     pub fn iter_local_def_id(&self) -> impl Iterator<Item = LocalDefId> + '_ {
         self.def_id_to_hir_id.iter_enumerated().map(|(k, _)| k)
     }
diff --git a/compiler/rustc_resolve/src/lib.rs b/compiler/rustc_resolve/src/lib.rs
index 6d2961db9e3..ead3ca9fcde 100644
--- a/compiler/rustc_resolve/src/lib.rs
+++ b/compiler/rustc_resolve/src/lib.rs
@@ -1012,8 +1012,6 @@ pub struct Resolver<'a> {
 
     next_node_id: NodeId,
 
-    def_id_to_span: IndexVec<LocalDefId, Span>,
-
     node_id_to_def_id: FxHashMap<ast::NodeId, LocalDefId>,
     def_id_to_node_id: IndexVec<LocalDefId, ast::NodeId>,
 
@@ -1197,9 +1195,7 @@ impl ResolverAstLowering for Resolver<'_> {
             disambiguator
         };
 
-        let def_id = self.definitions.create_def(parent, data, expn_id, next_disambiguator);
-
-        assert_eq!(self.def_id_to_span.push(span), def_id);
+        let def_id = self.definitions.create_def(parent, data, expn_id, next_disambiguator, span);
 
         // Some things for which we allocate `LocalDefId`s don't correspond to
         // anything in the AST, so they don't have a `NodeId`. For these cases
@@ -1269,14 +1265,12 @@ impl<'a> Resolver<'a> {
         let mut module_map = FxHashMap::default();
         module_map.insert(root_local_def_id, graph_root);
 
-        let definitions = Definitions::new(session.local_stable_crate_id());
+        let definitions = Definitions::new(session.local_stable_crate_id(), krate.span);
         let root = definitions.get_root_def();
 
         let mut visibilities = FxHashMap::default();
         visibilities.insert(root_local_def_id, ty::Visibility::Public);
 
-        let mut def_id_to_span = IndexVec::default();
-        assert_eq!(def_id_to_span.push(rustc_span::DUMMY_SP), root);
         let mut def_id_to_node_id = IndexVec::default();
         assert_eq!(def_id_to_node_id.push(CRATE_NODE_ID), root);
         let mut node_id_to_def_id = FxHashMap::default();
@@ -1393,7 +1387,6 @@ impl<'a> Resolver<'a> {
                 .collect(),
             lint_buffer: LintBuffer::default(),
             next_node_id: NodeId::from_u32(1),
-            def_id_to_span,
             node_id_to_def_id,
             def_id_to_node_id,
             placeholder_field_indices: Default::default(),
@@ -3360,7 +3353,7 @@ impl<'a> Resolver<'a> {
     /// Retrieves the span of the given `DefId` if `DefId` is in the local crate.
     #[inline]
     pub fn opt_span(&self, def_id: DefId) -> Option<Span> {
-        if let Some(def_id) = def_id.as_local() { Some(self.def_id_to_span[def_id]) } else { None }
+        def_id.as_local().map(|def_id| self.definitions.def_span(def_id))
     }
 
     /// Checks if an expression refers to a function marked with