Auto merge of #52644 - varkor:lib-feature-gate-2, r=withoutboats

Add errors for unknown, stable and duplicate feature attributes

- Adds an error for unknown (lang and lib) features.
- Extends the lint for unnecessary feature attributes for stable features to libs features (this already exists for lang features).
- Adds an error for duplicate (lang and lib) features.

```rust
#![feature(fake_feature)] //~ ERROR unknown feature `fake_feature`

#![feature(i128_type)] //~ WARNING the feature `i128_type` has been stable since 1.26.0

#![feature(non_exhaustive)]
#![feature(non_exhaustive)] //~ ERROR duplicate `non_exhaustive` feature attribute
```

Fixes #52053, fixes #53032 and address some of the problems noted in #44232 (though not unused features).

There are a few outstanding problems, that I haven't narrowed down yet:
- [x] Stability attributes on macros do not seem to be taken into account.
- [x] Stability attributes behind `cfg` attributes are not taken into account.
- [x] There are failing incremental tests.

Author: bors

src/etc/test-float-parse/many-digits.rs

@@ -8,8 +8,6 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-#![feature(rand)]
-
 extern crate rand;
 
 mod _common;

src/etc/test-float-parse/rand-f64.rs

@@ -8,8 +8,6 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-#![feature(rand)]
-
 extern crate rand;
 
 mod _common;

src/liballoc/benches/lib.rs

@@ -8,7 +8,6 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-#![feature(rand)]
 #![feature(repr_simd)]
 #![feature(slice_sort_by_cached_key)]
 #![feature(test)]

src/liballoc/collections/vec_deque.rs

@@ -2370,7 +2370,7 @@ macro_rules! __impl_slice_eq1 {
         __impl_slice_eq1! { $Lhs, $Rhs, Sized }
     };
     ($Lhs: ty, $Rhs: ty, $Bound: ident) => {
-        #[stable(feature = "vec-deque-partial-eq-slice", since = "1.17.0")]
+        #[stable(feature = "vec_deque_partial_eq_slice", since = "1.17.0")]
         impl<'a, 'b, A: $Bound, B> PartialEq<$Rhs> for $Lhs where A: PartialEq<B> {
             fn eq(&self, other: &$Rhs) -> bool {
                 if self.len() != other.len() {

src/liballoc/lib.rs

@@ -74,27 +74,24 @@
 #![needs_allocator]
 #![deny(missing_debug_implementations)]
 
-#![cfg_attr(test, allow(deprecated))] // rand
-#![cfg_attr(not(test), feature(exact_size_is_empty))]
+#![cfg_attr(not(test), feature(fn_traits))]
 #![cfg_attr(not(test), feature(generator_trait))]
-#![cfg_attr(test, feature(rand, test))]
+#![cfg_attr(test, feature(test))]
+
 #![feature(allocator_api)]
 #![feature(allow_internal_unstable)]
 #![feature(arbitrary_self_types)]
-#![feature(ascii_ctype)]
 #![feature(box_into_raw_non_null)]
 #![feature(box_patterns)]
 #![feature(box_syntax)]
 #![feature(cfg_target_has_atomic)]
 #![feature(coerce_unsized)]
-#![feature(collections_range)]
 #![feature(const_fn)]
 #![feature(core_intrinsics)]
 #![feature(custom_attribute)]
 #![feature(dropck_eyepatch)]
 #![feature(exact_size_is_empty)]
 #![feature(fmt_internals)]
-#![feature(from_ref)]
 #![feature(fundamental)]
 #![feature(futures_api)]
 #![feature(lang_items)]
@@ -118,14 +115,9 @@
 #![feature(allocator_internals)]
 #![feature(on_unimplemented)]
 #![feature(exact_chunks)]
-#![feature(pointer_methods)]
-#![feature(inclusive_range_methods)]
 #![feature(rustc_const_unstable)]
 #![feature(const_vec_new)]
 
-#![cfg_attr(not(test), feature(fn_traits, i128))]
-#![cfg_attr(test, feature(test))]
-
 // Allow testing this library
 
 #[cfg(test)]

src/liballoc/tests/lib.rs

@@ -16,11 +16,8 @@
 #![feature(drain_filter)]
 #![feature(exact_size_is_empty)]
 #![feature(pattern)]
-#![feature(rand)]
 #![feature(slice_sort_by_cached_key)]
-#![feature(splice)]
 #![feature(str_escape)]
-#![feature(string_retain)]
 #![feature(try_reserve)]
 #![feature(unboxed_closures)]
 #![feature(exact_chunks)]

src/libcore/char/methods.rs

@@ -1050,8 +1050,6 @@ impl char {
     /// # Examples
     ///
     /// ```
-    /// #![feature(ascii_ctype)]
-    ///
     /// let uppercase_a = 'A';
     /// let uppercase_g = 'G';
     /// let a = 'a';
@@ -1084,8 +1082,6 @@ impl char {
     /// # Examples
     ///
     /// ```
-    /// #![feature(ascii_ctype)]
-    ///
     /// let uppercase_a = 'A';
     /// let uppercase_g = 'G';
     /// let a = 'a';
@@ -1118,8 +1114,6 @@ impl char {
     /// # Examples
     ///
     /// ```
-    /// #![feature(ascii_ctype)]
-    ///
     /// let uppercase_a = 'A';
     /// let uppercase_g = 'G';
     /// let a = 'a';
@@ -1155,8 +1149,6 @@ impl char {
     /// # Examples
     ///
     /// ```
-    /// #![feature(ascii_ctype)]
-    ///
     /// let uppercase_a = 'A';
     /// let uppercase_g = 'G';
     /// let a = 'a';
@@ -1189,8 +1181,6 @@ impl char {
     /// # Examples
     ///
     /// ```
-    /// #![feature(ascii_ctype)]
-    ///
     /// let uppercase_a = 'A';
     /// let uppercase_g = 'G';
     /// let a = 'a';
@@ -1226,8 +1216,6 @@ impl char {
     /// # Examples
     ///
     /// ```
-    /// #![feature(ascii_ctype)]
-    ///
     /// let uppercase_a = 'A';
     /// let uppercase_g = 'G';
     /// let a = 'a';
@@ -1264,8 +1252,6 @@ impl char {
     /// # Examples
     ///
     /// ```
-    /// #![feature(ascii_ctype)]
-    ///
     /// let uppercase_a = 'A';
     /// let uppercase_g = 'G';
     /// let a = 'a';
@@ -1298,8 +1284,6 @@ impl char {
     /// # Examples
     ///
     /// ```
-    /// #![feature(ascii_ctype)]
-    ///
     /// let uppercase_a = 'A';
     /// let uppercase_g = 'G';
     /// let a = 'a';
@@ -1349,8 +1333,6 @@ impl char {
     /// # Examples
     ///
     /// ```
-    /// #![feature(ascii_ctype)]
-    ///
     /// let uppercase_a = 'A';
     /// let uppercase_g = 'G';
     /// let a = 'a';
@@ -1385,8 +1367,6 @@ impl char {
     /// # Examples
     ///
     /// ```
-    /// #![feature(ascii_ctype)]
-    ///
     /// let uppercase_a = 'A';
     /// let uppercase_g = 'G';
     /// let a = 'a';

src/libcore/lib.rs

@@ -82,7 +82,6 @@
 #![feature(concat_idents)]
 #![feature(const_fn)]
 #![feature(const_int_ops)]
-#![feature(core_float)]
 #![feature(custom_attribute)]
 #![feature(doc_cfg)]
 #![feature(doc_spotlight)]
@@ -102,16 +101,13 @@
 #![feature(rustc_attrs)]
 #![feature(rustc_const_unstable)]
 #![feature(simd_ffi)]
-#![feature(core_slice_ext)]
-#![feature(core_str_ext)]
 #![feature(specialization)]
 #![feature(staged_api)]
 #![feature(stmt_expr_attributes)]
 #![feature(unboxed_closures)]
 #![feature(untagged_unions)]
 #![feature(unwind_attributes)]
 #![feature(doc_alias)]
-#![feature(inclusive_range_methods)]
 #![feature(mmx_target_feature)]
 #![feature(tbm_target_feature)]
 #![feature(sse4a_target_feature)]

src/libcore/num/mod.rs

@@ -3761,8 +3761,6 @@ impl u8 {
     /// # Examples
     ///
     /// ```
-    /// #![feature(ascii_ctype)]
-    ///
     /// let uppercase_a = b'A';
     /// let uppercase_g = b'G';
     /// let a = b'a';
@@ -3799,8 +3797,6 @@ impl u8 {
     /// # Examples
     ///
     /// ```
-    /// #![feature(ascii_ctype)]
-    ///
     /// let uppercase_a = b'A';
     /// let uppercase_g = b'G';
     /// let a = b'a';
@@ -3837,8 +3833,6 @@ impl u8 {
     /// # Examples
     ///
     /// ```
-    /// #![feature(ascii_ctype)]
-    ///
     /// let uppercase_a = b'A';
     /// let uppercase_g = b'G';
     /// let a = b'a';
@@ -3878,8 +3872,6 @@ impl u8 {
     /// # Examples
     ///
     /// ```
-    /// #![feature(ascii_ctype)]
-    ///
     /// let uppercase_a = b'A';
     /// let uppercase_g = b'G';
     /// let a = b'a';
@@ -3916,8 +3908,6 @@ impl u8 {
     /// # Examples
     ///
     /// ```
-    /// #![feature(ascii_ctype)]
-    ///
     /// let uppercase_a = b'A';
     /// let uppercase_g = b'G';
     /// let a = b'a';
@@ -3957,8 +3947,6 @@ impl u8 {
     /// # Examples
     ///
     /// ```
-    /// #![feature(ascii_ctype)]
-    ///
     /// let uppercase_a = b'A';
     /// let uppercase_g = b'G';
     /// let a = b'a';
@@ -3999,8 +3987,6 @@ impl u8 {
     /// # Examples
     ///
     /// ```
-    /// #![feature(ascii_ctype)]
-    ///
     /// let uppercase_a = b'A';
     /// let uppercase_g = b'G';
     /// let a = b'a';
@@ -4037,8 +4023,6 @@ impl u8 {
     /// # Examples
     ///
     /// ```
-    /// #![feature(ascii_ctype)]
-    ///
     /// let uppercase_a = b'A';
     /// let uppercase_g = b'G';
     /// let a = b'a';
@@ -4092,8 +4076,6 @@ impl u8 {
     /// # Examples
     ///
     /// ```
-    /// #![feature(ascii_ctype)]
-    ///
     /// let uppercase_a = b'A';
     /// let uppercase_g = b'G';
     /// let a = b'a';
@@ -4132,8 +4114,6 @@ impl u8 {
     /// # Examples
     ///
     /// ```
-    /// #![feature(ascii_ctype)]
-    ///
     /// let uppercase_a = b'A';
     /// let uppercase_g = b'G';
     /// let a = b'a';

src/libcore/slice/mod.rs

@@ -2007,7 +2007,7 @@ pub trait SliceIndex<T: ?Sized>: private_slice_index::Sealed {
     fn index_mut(self, slice: &mut T) -> &mut Self::Output;
 }
 
-#[stable(feature = "slice-get-slice-impls", since = "1.15.0")]
+#[stable(feature = "slice_get_slice_impls", since = "1.15.0")]
 impl<T> SliceIndex<[T]> for usize {
     type Output = T;
 
@@ -2056,7 +2056,7 @@ impl<T> SliceIndex<[T]> for usize {
     }
 }
 
-#[stable(feature = "slice-get-slice-impls", since = "1.15.0")]
+#[stable(feature = "slice_get_slice_impls", since = "1.15.0")]
 impl<T> SliceIndex<[T]> for  ops::Range<usize> {
     type Output = [T];
 
@@ -2117,7 +2117,7 @@ impl<T> SliceIndex<[T]> for  ops::Range<usize> {
     }
 }
 
-#[stable(feature = "slice-get-slice-impls", since = "1.15.0")]
+#[stable(feature = "slice_get_slice_impls", since = "1.15.0")]
 impl<T> SliceIndex<[T]> for ops::RangeTo<usize> {
     type Output = [T];
 
@@ -2152,7 +2152,7 @@ impl<T> SliceIndex<[T]> for ops::RangeTo<usize> {
     }
 }
 
-#[stable(feature = "slice-get-slice-impls", since = "1.15.0")]
+#[stable(feature = "slice_get_slice_impls", since = "1.15.0")]
 impl<T> SliceIndex<[T]> for ops::RangeFrom<usize> {
     type Output = [T];
 
@@ -2187,7 +2187,7 @@ impl<T> SliceIndex<[T]> for ops::RangeFrom<usize> {
     }
 }
 
-#[stable(feature = "slice-get-slice-impls", since = "1.15.0")]
+#[stable(feature = "slice_get_slice_impls", since = "1.15.0")]
 impl<T> SliceIndex<[T]> for ops::RangeFull {
     type Output = [T];