Convert unknown_features lint into an error

Author: varkor

src/librustc/diagnostics.rs

@@ -1918,6 +1918,17 @@ fn foo<'a>(x: &'a i32, y: &i32) -> &'a i32 {
 ```
 "##,
 
+E0635: r##"
+The `#![feature]` attribute specified an unknown feature.
+
+Erroneous code example:
+
+```compile_fail,E0635
+#![feature(nonexistent_rust_feature)] // error: unknown feature
+```
+
+"##,
+
 E0636: r##"
 A `#![feature]` attribute was declared multiple times.
 

src/librustc/lint/builtin.rs

@@ -105,12 +105,6 @@ declare_lint! {
     "unused features found in crate-level #[feature] directives"
 }
 
-declare_lint! {
-    pub UNKNOWN_FEATURES,
-    Deny,
-    "unknown features found in crate-level #[feature] directives"
-}
-
 declare_lint! {
     pub STABLE_FEATURES,
     Warn,
@@ -368,7 +362,6 @@ impl LintPass for HardwiredLints {
             UNUSED_MACROS,
             WARNINGS,
             UNUSED_FEATURES,
-            UNKNOWN_FEATURES,
             STABLE_FEATURES,
             UNKNOWN_CRATE_TYPES,
             TRIVIAL_CASTS,

src/librustc/middle/stability.rs

@@ -840,6 +840,10 @@ pub fn check_unused_or_stable_features<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>) {
     // FIXME(varkor): we don't properly handle lib features behind `cfg` attributes yet,
     // but it happens just to affect `libc`, so we're just going to hard-code it for now.
     remaining_lib_features.remove(&Symbol::intern("libc"));
+    // FIXME(varkor): we have a problem gathering features on macros right now, so we're
+    // going to hard-code some features here for now.
+    remaining_lib_features.remove(&Symbol::intern("await_macro"));
+    remaining_lib_features.remove(&Symbol::intern("unstable_macros"));
 
     for (feature, stable) in tcx.lib_features().iter() {
         if let Some(since) = stable {
@@ -852,10 +856,7 @@ pub fn check_unused_or_stable_features<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>) {
     }
 
     for (feature, span) in remaining_lib_features {
-        tcx.lint_node(lint::builtin::UNKNOWN_FEATURES,
-                      ast::CRATE_NODE_ID,
-                      span,
-                      &format!("unknown feature `{}`", feature));
+        struct_span_err!(tcx.sess, span, E0635, "unknown feature `{}`", feature).emit();
     }
 
     // FIXME(#44232): the `used_features` table no longer exists, so we

src/librustc_lint/lib.rs

@@ -188,7 +188,6 @@ pub fn register_builtins(store: &mut lint::LintStore, sess: Option<&Session>) {
                     UNUSED_DOC_COMMENTS,
                     UNUSED_EXTERN_CRATES,
                     UNUSED_FEATURES,
-                    UNKNOWN_FEATURES,
                     UNUSED_LABELS,
                     UNUSED_PARENS);
 
@@ -343,6 +342,7 @@ pub fn register_builtins(store: &mut lint::LintStore, sess: Option<&Session>) {
     store.register_renamed("bare_trait_object", "bare_trait_objects");
     store.register_renamed("unstable_name_collision", "unstable_name_collisions");
     store.register_renamed("unused_doc_comment", "unused_doc_comments");
+    store.register_removed("unknown_features", "replaced by an error");
     store.register_removed("unsigned_negation", "replaced by negate_unsigned feature gate");
     store.register_removed("negate_unsigned", "cast a signed value instead");
     store.register_removed("raw_pointer_derive", "using derive with raw pointers is ok");

src/libsyntax/diagnostic_list.rs

@@ -374,18 +374,6 @@ and likely to change in the future.
 
 "##,
 
-E0635: r##"
-The `#![feature]` attribute specified an unknown feature.
-
-Erroneous code example:
-
-```compile_fail,E0635
-#![feature(nonexistent_rust_feature)] // error: unknown feature
-```
-
-"##,
-
-
 }
 
 register_diagnostics! {

src/libsyntax/feature_gate.rs

@@ -140,7 +140,6 @@ declare_features! (
     (active, linkage, "1.0.0", Some(29603), None),
     (active, quote, "1.0.0", Some(29601), None),
 
-
     // rustc internal
     (active, rustc_diagnostic_macros, "1.0.0", None, None),
     (active, rustc_const_unstable, "1.0.0", None, None),

src/test/compile-fail/lint-renamed-allow.rs

@@ -13,6 +13,6 @@
 
 #![allow(renamed_and_removed_lints)]
 
-#[deny(unknown_features)]
+#[deny(single_use_lifetime)]
 #[deny(unused)]
 fn main() { let unused = (); } //~ ERROR unused

src/test/compile-fail/lint-unknown-feature-default.rs

@@ -10,8 +10,9 @@
 
 // Tests the default for the unused_features lint
 
+#![allow(stable_features)]
 // FIXME(#44232) we should warn that this isn't used.
-#![feature(this_is_not_a_feature)]
+#![feature(rust1)]
 
 #![feature(rustc_attrs)]
 

src/test/compile-fail/lint-unknown-feature.rs

@@ -10,8 +10,9 @@
 
 #![warn(unused_features)]
 
+#![allow(stable_features)]
 // FIXME(#44232) we should warn that this isn't used.
-#![feature(this_is_not_a_feature)]
+#![feature(rust1)]
 
 #![feature(rustc_attrs)]
 

src/test/run-fail/args-panic.rs

@@ -11,7 +11,6 @@
 
 // error-pattern:meep
 
-#![allow(unknown_features)]
 #![feature(box_syntax)]
 
 fn f(_a: isize, _b: isize, _c: Box<isize>) {