Make -Z allow-features work for stdlib features

Author: tmandry

src/libsyntax/feature_gate.rs

@@ -2258,32 +2258,32 @@ pub fn get_features(span_handler: &Handler, krate_attrs: &[ast::Attribute],
                 continue;
             }
 
-            if let Some((.., set)) = ACTIVE_FEATURES.iter().find(|f| name == f.0) {
-                if let Some(allowed) = allow_features.as_ref() {
-                    if allowed.iter().find(|f| *f == name.as_str()).is_none() {
-                        span_err!(span_handler, mi.span(), E0725,
-                                  "the feature `{}` is not in the list of allowed features",
-                                  name);
-                        continue;
-                    }
-                }
-
-                set(&mut features, mi.span());
-                features.declared_lang_features.push((name, mi.span(), None));
-                continue
-            }
-
             let removed = REMOVED_FEATURES.iter().find(|f| name == f.0);
             let stable_removed = STABLE_REMOVED_FEATURES.iter().find(|f| name == f.0);
             if let Some((.., reason)) = removed.or(stable_removed) {
                 feature_removed(span_handler, mi.span(), *reason);
-                continue
+                continue;
             }
 
             if let Some((_, since, ..)) = ACCEPTED_FEATURES.iter().find(|f| name == f.0) {
                 let since = Some(Symbol::intern(since));
                 features.declared_lang_features.push((name, mi.span(), since));
-                continue
+                continue;
+            }
+
+            if let Some(allowed) = allow_features.as_ref() {
+                if allowed.iter().find(|f| *f == name.as_str()).is_none() {
+                    span_err!(span_handler, mi.span(), E0725,
+                              "the feature `{}` is not in the list of allowed features",
+                              name);
+                    continue;
+                }
+            }
+
+            if let Some((.., set)) = ACTIVE_FEATURES.iter().find(|f| name == f.0) {
+                set(&mut features, mi.span());
+                features.declared_lang_features.push((name, mi.span(), None));
+                continue;
             }
 
             features.declared_lib_features.push((name, mi.span()));

src/test/ui/feature-gate/allow-features-empty.rs

@@ -7,4 +7,6 @@
 
 #![feature(lang_items)] //~ ERROR
 
+#![feature(unknown_stdlib_feature)] //~ ERROR
+
 fn main() {}

src/test/ui/feature-gate/allow-features-empty.stderr

@@ -16,6 +16,12 @@ error[E0725]: the feature `lang_items` is not in the list of allowed features
 LL | #![feature(lang_items)]
    |            ^^^^^^^^^^
 
-error: aborting due to 3 previous errors
+error[E0725]: the feature `unknown_stdlib_feature` is not in the list of allowed features
+  --> $DIR/allow-features-empty.rs:10:12
+   |
+LL | #![feature(unknown_stdlib_feature)]
+   |            ^^^^^^^^^^^^^^^^^^^^^^
+
+error: aborting due to 4 previous errors
 
 For more information about this error, try `rustc --explain E0725`.

src/test/ui/feature-gate/allow-features.rs

@@ -7,4 +7,6 @@
 
 #![feature(lang_items)]
 
+#![feature(unknown_stdlib_feature)] //~ ERROR
+
 fn main() {}

src/test/ui/feature-gate/allow-features.stderr

@@ -4,6 +4,12 @@ error[E0725]: the feature `rustc_const_unstable` is not in the list of allowed f
 LL | #![feature(rustc_const_unstable)]
    |            ^^^^^^^^^^^^^^^^^^^^
 
-error: aborting due to previous error
+error[E0725]: the feature `unknown_stdlib_feature` is not in the list of allowed features
+  --> $DIR/allow-features.rs:10:12
+   |
+LL | #![feature(unknown_stdlib_feature)]
+   |            ^^^^^^^^^^^^^^^^^^^^^^
+
+error: aborting due to 2 previous errors
 
 For more information about this error, try `rustc --explain E0725`.