Allow builtin macros to be used more than once.

This removes E0773 "A builtin-macro was defined more than once."

Author: m-ou-se

compiler/rustc_builtin_macros/src/eii.rs

@@ -62,14 +62,8 @@ fn eii_(
 
     let item = item.into_inner();
 
-    let ast::Item {
-        attrs,
-        id: _,
-        span: item_span,
-        vis,
-        kind: ItemKind::Fn(mut func),
-        tokens: _,
-    } = item
+    let ast::Item { attrs, id: _, span: item_span, vis, kind: ItemKind::Fn(mut func), tokens: _ } =
+        item
     else {
         ecx.dcx()
             .emit_err(EIIMacroExpectedFunction { span, name: path_to_string(&meta_item.path) });
@@ -195,7 +189,7 @@ fn eii_(
                     extern_item_path: ast::Path::from_ident(func.ident),
                     impl_unsafe,
                 }),
-            }
+            },
         ),
         tokens: None,
     }));

compiler/rustc_resolve/src/macros.rs

@@ -1138,8 +1138,6 @@ impl<'ra, 'tcx> Resolver<'ra, 'tcx> {
         if let Some(builtin_name) = ext.builtin_name {
             // The macro was marked with `#[rustc_builtin_macro]`.
             if let Some(builtin_ext_kind) = self.builtin_macros.get(&builtin_name) {
-                // The macro is a built-in, replace its expander function
-                // while still taking everything else from the source code.
                 ext.kind = builtin_ext_kind.clone();
                 rule_spans = Vec::new();
             } else {