make `cfg_select` a builtin macro

1 files changed, 20 insertions, 0 deletions

diff --git a/compiler/rustc_expand/src/base.rs b/compiler/rustc_expand/src/base.rs
index d6d89808839..757a7e1c8e7 100644
--- a/compiler/rustc_expand/src/base.rs
+++ b/compiler/rustc_expand/src/base.rs
@@ -34,6 +34,7 @@ use thin_vec::ThinVec;
 use crate::base::ast::MetaItemInner;
 use crate::errors;
 use crate::expand::{self, AstFragment, Invocation};
+use crate::mbe::macro_rules::ParserAnyMacro;
 use crate::module::DirOwnership;
 use crate::stats::MacroStat;
 
@@ -262,6 +263,25 @@ impl<T, U> ExpandResult<T, U> {
     }
 }
 
+impl<'cx> MacroExpanderResult<'cx> {
+    /// Creates a [`MacroExpanderResult::Ready`] from a [`TokenStream`].
+    ///
+    /// The `TokenStream` is forwarded without any expansion.
+    pub fn from_tts(
+        cx: &'cx mut ExtCtxt<'_>,
+        tts: TokenStream,
+        site_span: Span,
+        arm_span: Span,
+        macro_ident: Ident,
+    ) -> Self {
+        // Emit the SEMICOLON_IN_EXPRESSIONS_FROM_MACROS deprecation lint.
+        let is_local = true;
+
+        let parser = ParserAnyMacro::from_tts(cx, tts, site_span, arm_span, is_local, macro_ident);
+        ExpandResult::Ready(Box::new(parser))
+    }
+}
+
 pub trait MultiItemModifier {
     /// `meta_item` is the attribute, and `item` is the item being modified.
     fn expand(