Rewrite method resolution to be cleaner, more correct, and to lay

groundwork for better performance.

Key points:

- Separate out determining which method to use from actually selecting
  a method (this should enable caching, as well as the pcwalton fast-reject strategy).
- Merge the impl selection back into method resolution and don't rely on
  trait matching (this should perform better but also is needed to resolve some
  kind of conflicts, see e.g. `method-two-traits-distinguished-via-where-clause.rs`)
- Purge a lot of out-of-date junk and coercions from method lookups.

1 files changed, 1 insertions, 1 deletions

diff --git a/src/libsyntax/ast_map/mod.rs b/src/libsyntax/ast_map/mod.rs
index 2a2ad9fd664..b116c84552e 100644
--- a/src/libsyntax/ast_map/mod.rs
+++ b/src/libsyntax/ast_map/mod.rs
@@ -544,7 +544,7 @@ impl<'ast> Map<'ast> {
 
     pub fn def_id_span(&self, def_id: DefId, fallback: Span) -> Span {
         if def_id.krate == LOCAL_CRATE {
-            self.span(def_id.node)
+            self.opt_span(def_id.node).unwrap_or(fallback)
         } else {
             fallback
         }