Fix panic in tuple fields

Author: matklad

crates/ra_hir_expand/src/name.rs

@@ -93,7 +93,10 @@ impl AsName for ast::FieldKind {
     fn as_name(&self) -> Name {
         match self {
             ast::FieldKind::Name(nr) => nr.as_name(),
-            ast::FieldKind::Index(idx) => Name::new_tuple_field(idx.text().parse().unwrap()),
+            ast::FieldKind::Index(idx) => {
+                let idx = idx.text().parse::<usize>().unwrap_or(0);
+                Name::new_tuple_field(idx)
+            }
         }
     }
 }