Don't create a path with zero segments

Author: fmease

src/librustdoc/html/render/span_map.rs

@@ -131,32 +131,23 @@ impl<'tcx> SpanMapVisitor<'tcx> {
             Res::Def(kind, def_id) if kind != DefKind::TyParam => {
                 let last_segment = path.segments.last().unwrap();
                 // In case the path ends with generics, we remove them from the span.
-                let span = if only_use_last_segment
-                    && let Some(path_span) = path.segments.last().map(|segment| segment.ident.span)
-                {
-                    path_span
+                let span = if only_use_last_segment {
+                    last_segment.ident.span
                 } else {
-                    path.segments
-                        .last()
-                        .map(|last| {
-                            // In `use` statements, the included item is not in the path segments.
-                            // However, it doesn't matter because you can't have generics on `use`
-                            // statements.
-                            if path.span.contains(last.ident.span) {
-                                path.span.with_hi(last.ident.span.hi())
-                            } else {
-                                path.span
-                            }
-                        })
-                        .unwrap_or(path.span)
+                    // In `use` statements, the included item is not in the path segments.
+                    // However, it doesn't matter because you can't have generics on `use`
+                    // statements.
+                    if path.span.contains(last_segment.ident.span) {
+                        path.span.with_hi(last_segment.ident.span.hi())
+                    } else {
+                        path.span
+                    }
                 };
                 self.matches.insert(span.into(), self.link_for_def(def_id));
             }
             Res::Local(_) if let Some(span) = self.tcx.hir_res_span(path.res) => {
-                let path_span = if only_use_last_segment
-                    && let Some(path_span) = path.segments.last().map(|segment| segment.ident.span)
-                {
-                    path_span
+                let path_span = if only_use_last_segment {
+                    path.segments.last().unwrap().ident.span
                 } else {
                     path.span
                 };
@@ -167,7 +158,6 @@ impl<'tcx> SpanMapVisitor<'tcx> {
                 self.matches
                     .insert(path.span.into(), LinkFromSrc::Primitive(PrimitiveType::from(p)));
             }
-            Res::Err => {}
             _ => {}
         }
     }
@@ -265,8 +255,7 @@ impl<'tcx> Visitor<'tcx> for SpanMapVisitor<'tcx> {
                         // We change the span to not include parens.
                         span: segment.ident.span,
                         res: typeck_results.qpath_res(qpath, id),
-                        // FIXME(fmease): Don't create a path with zero segments!
-                        segments: &[],
+                        segments: std::slice::from_ref(segment),
                     };
                     self.handle_path(&path, false);
                 }