stabilise cfg_attr

Author: Dylan-DPC

src/doc/unstable-book/src/language-features/cfg-attr-multi.md

@@ -94,11 +94,6 @@ impl<'a> StripUnconfigured<'a> {
             return vec![attr];
         }
 
-        let gate_cfg_attr_multi = if let Some(ref features) = self.features {
-            !features.cfg_attr_multi
-        } else {
-            false
-        };
         let cfg_attr_span = attr.span;
 
         let (cfg_predicate, expanded_attrs) = match attr.parse(self.sess, |parser| {
@@ -130,21 +125,8 @@ impl<'a> StripUnconfigured<'a> {
         // Check feature gate and lint on zero attributes in source. Even if the feature is gated,
         // we still compute as if it wasn't, since the emitted error will stop compilation further
         // along the compilation.
-        match (expanded_attrs.len(), gate_cfg_attr_multi) {
-            (0, false) => {
-                // FIXME: Emit unused attribute lint here.
-            },
-            (1, _) => {},
-            (_, true) => {
-                emit_feature_err(
-                    self.sess,
-                    "cfg_attr_multi",
-                    cfg_attr_span,
-                    GateIssue::Language,
-                    "cfg_attr with zero or more than one attributes is experimental",
-                );
-            },
-            (_, false) => {}
+        if expanded_attrs.len() == 0 {
+            // FIXME: Emit unused attribute lint here.
         }
 
         if attr::cfg_matches(&cfg_predicate, self.sess, self.features) {

src/libsyntax/config.rs

@@ -465,9 +465,6 @@ declare_features! (
     // Allows `impl Trait` in bindings (`let`, `const`, `static`).
     (active, impl_trait_in_bindings, "1.30.0", Some(34511), None),
 
-    // `#[cfg_attr(predicate, multiple, attributes, here)]`
-    (active, cfg_attr_multi, "1.31.0", Some(54881), None),
-
     // Allows `const _: TYPE = VALUE`.
     (active, underscore_const_names, "1.31.0", Some(54912), None),
 
@@ -689,6 +686,8 @@ declare_features! (
     (accepted, repr_packed, "1.33.0", Some(33158), None),
     // Allows calling `const unsafe fn` inside `unsafe` blocks in `const fn` functions.
     (accepted, min_const_unsafe_fn, "1.33.0", Some(55607), None),
+// `#[cfg_attr(predicate, multiple, attributes, here)]`
+    (accepted, cfg_attr_multi, "1.33.0", Some(54881), None),
 );
 
 // If you change this, please modify `src/doc/unstable-book` as well. You must

src/libsyntax/feature_gate.rs

@@ -4,7 +4,7 @@
 // compile-pass
 
 #![warn(unused_must_use)]
-#![feature(cfg_attr_multi)]
+#![cfg_attr(stage0, feature(cfg_attr_multi))]
 
 #[cfg_attr(any(), deprecated, must_use)]
 struct Struct {}

src/test/ui/conditional-compilation/cfg-attr-multi-false.rs

@@ -1,6 +1,5 @@
 // compile-flags: --cfg broken
 
-#![feature(cfg_attr_multi)]
 #![crate_type = "lib"]
 #![cfg_attr(broken, no_core, no_std)] //~ ERROR no_core is experimental
 

src/test/ui/conditional-compilation/cfg-attr-multi-invalid-1.rs

@@ -1,6 +1,5 @@
 // compile-flags: --cfg broken
 
-#![feature(cfg_attr_multi)]
 #![crate_type = "lib"]
 #![cfg_attr(broken, no_std, no_core)] //~ ERROR no_core is experimental
 

src/test/ui/conditional-compilation/cfg-attr-multi-invalid-2.rs

@@ -5,7 +5,7 @@
 // compile-pass
 
 #![warn(unused_must_use)]
-#![feature(cfg_attr_multi)]
+#![cfg_attr(stage0, feature(cfg_attr_multi))]
 
 #[cfg_attr(all(), deprecated, must_use)]
 struct MustUseDeprecated {}

src/test/ui/conditional-compilation/cfg-attr-multi-true.rs

@@ -1,6 +1,6 @@
 // Parse `cfg_attr` with varying numbers of attributes and trailing commas
 
-#![feature(cfg_attr_multi)]
+#![cfg_attr(stage0, feature(cfg_attr_multi))]
 
 // Completely empty `cfg_attr` input
 #[cfg_attr()] //~ error: expected identifier, found `)`