Rollup merge of #67131 - Centril:item-merge, r=petrochenkov

Merge `TraitItem` & `ImplItem into `AssocItem`

In this PR we:

- Merge `{Trait,Impl}Item{Kind?}` into `AssocItem{Kind?}` as discussed in https://github.com/rust-lang/rust/issues/65041#issuecomment-538105286.

   - This is done by using the cover grammar of both forms.

   - In particular, it requires that we syntactically allow (under `#[cfg(FALSE)]`):

      - `default`ness on `trait` items,

      - `impl` items without a body / definition (`const`, `type`, and `fn`),

      - and associated `type`s in `impl`s with bounds, e.g., `type Foo: Ord;`.

   - The syntactic restrictions are replaced by semantic ones in `ast_validation`.

- Move syntactic restrictions around C-variadic parameters from the parser into `ast_validation`:

    - `fn`s in all contexts now syntactically allow `...`,

    - `...` can occur anywhere in the list syntactically (`fn foo(..., x: usize) {}`),

    - and `...` can be the sole parameter (`fn foo(...) {}`.

r? @petrochenkov

1 files changed, 10 insertions, 8 deletions

diff --git a/src/libsyntax_ext/deriving/generic/mod.rs b/src/libsyntax_ext/deriving/generic/mod.rs
index 5bd84b43a78..b7707bfb8e5 100644
--- a/src/libsyntax_ext/deriving/generic/mod.rs
+++ b/src/libsyntax_ext/deriving/generic/mod.rs
@@ -504,13 +504,13 @@ impl<'a> TraitDef<'a> {
                            type_ident: Ident,
                            generics: &Generics,
                            field_tys: Vec<P<ast::Ty>>,
-                           methods: Vec<ast::ImplItem>)
+                           methods: Vec<ast::AssocItem>)
                            -> P<ast::Item> {
         let trait_path = self.path.to_path(cx, self.span, type_ident, generics);
 
-        // Transform associated types from `deriving::ty::Ty` into `ast::ImplItem`
+        // Transform associated types from `deriving::ty::Ty` into `ast::AssocItem`
         let associated_types = self.associated_types.iter().map(|&(ident, ref type_def)| {
-            ast::ImplItem {
+            ast::AssocItem {
                 id: ast::DUMMY_NODE_ID,
                 span: self.span,
                 ident,
@@ -518,8 +518,10 @@ impl<'a> TraitDef<'a> {
                 defaultness: ast::Defaultness::Final,
                 attrs: Vec::new(),
                 generics: Generics::default(),
-                kind: ast::ImplItemKind::TyAlias(
-                    type_def.to_ty(cx, self.span, type_ident, generics)),
+                kind: ast::AssocItemKind::TyAlias(
+                    Vec::new(),
+                    Some(type_def.to_ty(cx, self.span, type_ident, generics)),
+                ),
                 tokens: None,
             }
         });
@@ -910,7 +912,7 @@ impl<'a> MethodDef<'a> {
                      explicit_self: Option<ast::ExplicitSelf>,
                      arg_types: Vec<(Ident, P<ast::Ty>)>,
                      body: P<Expr>)
-                     -> ast::ImplItem {
+                     -> ast::AssocItem {
         // Create the generics that aren't for `Self`.
         let fn_generics = self.generics.to_generics(cx, trait_.span, type_ident, generics);
 
@@ -948,7 +950,7 @@ impl<'a> MethodDef<'a> {
         };
 
         // Create the method.
-        ast::ImplItem {
+        ast::AssocItem {
             id: ast::DUMMY_NODE_ID,
             attrs: self.attributes.clone(),
             generics: fn_generics,
@@ -956,7 +958,7 @@ impl<'a> MethodDef<'a> {
             vis: respan(trait_lo_sp, ast::VisibilityKind::Inherited),
             defaultness: ast::Defaultness::Final,
             ident: method_ident,
-            kind: ast::ImplItemKind::Method(sig, body_block),
+            kind: ast::AssocItemKind::Fn(sig, Some(body_block)),
             tokens: None,
         }
     }