Auto merge of #36066 - jseyfried:rollup, r=Manishearth

Batch up libsyntax breaking changes

Batch of the following syntax-[breaking-change] changes:
 - #35591: Add a field `span: Span` to `ast::Generics`.
 - #35618: Remove variant `Mod` of `ast::PathListItemKind` and refactor the remaining variant `ast::PathListKind::Ident` to a struct `ast::PathListKind_`.
 - #35480: Change uses of `Constness` in the AST to `Spanned<Constness>`.
  - c.f. `MethodSig`, `ItemKind`
 - #35728: Refactor `cx.pat_enum()` into `cx.pat_tuple_struct()` and `cx.pat_path()`.
 - #35850: Generalize the elements of lists in attributes from `MetaItem` to a new type `NestedMetaItem` that can represent a `MetaItem` or a literal.
 - #35917: Remove traits `AttrMetaMethods`, `AttributeMethods`, and `AttrNestedMetaItemMethods`.
  - Besides removing imports of these traits, this won't cause fallout.
 - Add a variant `Union` to `ItemKind` to future proof for `union` (c.f. #36016).
 - Remove inherent methods `attrs` and `fold_attrs` of `Annotatable`.
  - Use methods `attrs` and `map_attrs` of `HasAttrs` instead.

r? @Manishearth

1 files changed, 3 insertions, 2 deletions

diff --git a/src/libsyntax_ext/deriving/default.rs b/src/libsyntax_ext/deriving/default.rs
index 9df3db938b1..b15fd2b49a6 100644
--- a/src/libsyntax_ext/deriving/default.rs
+++ b/src/libsyntax_ext/deriving/default.rs
@@ -32,6 +32,7 @@ pub fn expand_deriving_default(cx: &mut ExtCtxt,
         additional_bounds: Vec::new(),
         generics: LifetimeBounds::empty(),
         is_unsafe: false,
+        supports_unions: false,
         methods: vec![MethodDef {
                           name: "default",
                           generics: LifetimeBounds::empty(),
@@ -57,8 +58,8 @@ fn default_substructure(cx: &mut ExtCtxt, trait_span: Span, substr: &Substructur
     return match *substr.fields {
         StaticStruct(_, ref summary) => {
             match *summary {
-                Unnamed(ref fields) => {
-                    if fields.is_empty() {
+                Unnamed(ref fields, is_tuple) => {
+                    if !is_tuple {
                         cx.expr_ident(trait_span, substr.type_ident)
                     } else {
                         let exprs = fields.iter().map(|sp| default_call(*sp)).collect();