RFC3239: Implement compact cfg(target(..))

compiler/rustc_attr/src/builtin.rs

@@ -630,6 +630,25 @@ pub fn eval_condition(
 
                     !eval_condition(mis[0].meta_item().unwrap(), sess, features, eval)
                 }
+                sym::target => {
+                    if let Some(features) = features && !features.cfg_target_compact {
+                        feature_err(
+                            sess,
+                            sym::cfg_target_compact,
+                            cfg.span,
+                            &"compact `cfg(target(..))` is experimental and subject to change"
+                        ).emit();
+                    }
+
+                    mis.iter().fold(true, |res, mi| {
+                        let mut mi = mi.meta_item().unwrap().clone();
+                        if let [seg, ..] = &mut mi.path.segments[..] {
+                            seg.ident.name = Symbol::intern(&format!("target_{}", seg.ident.name));
+                        }
+
+                        res & eval_condition(&mi, sess, features, eval)
+                    })
+                }
                 _ => {
                     struct_span_err!(
                         sess.span_diagnostic,

compiler/rustc_attr/src/lib.rs

@@ -4,6 +4,7 @@
 //! The goal is to move the definition of `MetaItem` and things that don't need to be in `syntax`
 //! to this crate.
 
+#![feature(let_chains)]
 #![feature(let_else)]
 
 #[macro_use]

compiler/rustc_feature/src/active.rs

@@ -319,6 +319,8 @@ declare_features! (
     (active, cfg_sanitize, "1.41.0", Some(39699), None),
     /// Allows `cfg(target_abi = "...")`.
     (active, cfg_target_abi, "1.55.0", Some(80970), None),
+    /// Allows `cfg(target(abi = "..."))`.
+    (active, cfg_target_compact, "1.63.0", Some(96901), None),
     /// Allows `cfg(target_has_atomic_load_store = "...")`.
     (active, cfg_target_has_atomic, "1.60.0", Some(94039), None),
     /// Allows `cfg(target_has_atomic_equal_alignment = "...")`.

compiler/rustc_span/src/symbol.rs

@@ -427,6 +427,7 @@ symbols! {
         cfg_panic,
         cfg_sanitize,
         cfg_target_abi,
+        cfg_target_compact,
         cfg_target_feature,
         cfg_target_has_atomic,
         cfg_target_has_atomic_equal_alignment,
@@ -1375,6 +1376,7 @@ symbols! {
         sym,
         sync,
         t32,
+        target,
         target_abi,
         target_arch,
         target_endian,