mbe: Silently ignore the body of a macro with rustc_builtin_macro

Don't bother detecting and reporting an error on a builtin macro with
`attr` rules; just ignore them.

Author: joshtriplett

compiler/rustc_resolve/messages.ftl

@@ -53,9 +53,6 @@ resolve_binding_shadows_something_unacceptable =
 resolve_binding_shadows_something_unacceptable_suggestion =
     try specify the pattern arguments
 
-resolve_builtin_macro_with_non_invocation_rules =
-    built-in macro `{$ident}` has non-invocation rules
-
 resolve_cannot_be_reexported_crate_public =
     `{$ident}` is only public within the crate, and cannot be re-exported outside
 

compiler/rustc_resolve/src/errors.rs

@@ -1054,14 +1054,6 @@ pub(crate) struct NameReservedInAttributeNamespace {
     pub(crate) ident: Ident,
 }
 
-#[derive(Diagnostic)]
-#[diag(resolve_builtin_macro_with_non_invocation_rules)]
-pub(crate) struct BuiltinMacroWithNonInvocationRules {
-    #[primary_span]
-    pub(crate) span: Span,
-    pub(crate) ident: Ident,
-}
-
 #[derive(Diagnostic)]
 #[diag(resolve_cannot_find_builtin_macro_with_name)]
 pub(crate) struct CannotFindBuiltinMacroWithName {

compiler/rustc_resolve/src/macros.rs

@@ -1170,7 +1170,7 @@ impl<'ra, 'tcx> Resolver<'ra, 'tcx> {
         node_id: NodeId,
         edition: Edition,
     ) -> MacroData {
-        let (mut ext, attr_ext, mut nrules) = compile_declarative_macro(
+        let (mut ext, mut attr_ext, mut nrules) = compile_declarative_macro(
             self.tcx.sess,
             self.tcx.features(),
             macro_def,
@@ -1182,14 +1182,12 @@ impl<'ra, 'tcx> Resolver<'ra, 'tcx> {
         );
 
         if let Some(builtin_name) = ext.builtin_name {
-            if attr_ext.is_some() {
-                self.dcx().emit_err(errors::BuiltinMacroWithNonInvocationRules { span, ident });
-            }
             // 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();
+                attr_ext = None;
                 nrules = 0;
             } else {
                 self.dcx().emit_err(errors::CannotFindBuiltinMacroWithName { span, ident });