Auto merge of #83301 - Dylan-DPC:rollup-x1yzvhm, r=Dylan-DPC

Rollup of 11 pull requests

Successful merges:

 - #82500 (Reuse `std::sys::unsupported::pipe` on `hermit`)
 - #82759 (Remove unwrap_none/expect_none from compiler/.)
 - #82846 (rustdoc: allow list syntax for #[doc(alias)] attributes)
 - #82892 (Clarify docs for Read::read's return value)
 - #83179 (Extend `proc_macro_back_compat` lint to `actix-web`)
 - #83197 (Move some test-only code to test files)
 - #83208 (Fix gitattibutes for old git versions)
 - #83215 (Deprecate std::os::haiku::raw, which accidentally wasn't deprecated)
 - #83230 (Remove unnecessary `forward_inner_docs` hack)
 - #83236 (Upgrade memmap to memmap2)
 - #83270 (Fix typo/inaccuracy in the documentation of Iterator::skip_while)

Failed merges:

r? `@ghost`
`@rustbot` modify labels: rollup

45 files changed, 530 insertions, 252 deletions

diff --git a/.gitattributes b/.gitattributes
index 4038db6f7da..d29c15fe712 100644
--- a/.gitattributes
+++ b/.gitattributes
@@ -7,11 +7,11 @@
 *.fixed linguist-language=Rust
 *.mir linguist-language=Rust
 src/etc/installer/gfx/* binary
-*.woff binary
-*.woff2 binary
 src/vendor/** -text
 Cargo.lock linguist-generated=false
 
-# Older git versions try to fix line endings on images, this prevents it.
+# Older git versions try to fix line endings on images and fonts, this prevents it.
 *.png binary
 *.ico binary
+*.woff binary
+*.woff2 binary
diff --git a/Cargo.lock b/Cargo.lock
index fd6fffe980b..e5a7b7d9b60 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -2165,6 +2165,15 @@ dependencies = [
 ]
 
 [[package]]
+name = "memmap2"
+version = "0.2.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "04e3e85b970d650e2ae6d70592474087051c11c54da7f7b4949725c5735fbcc6"
+dependencies = [
+ "libc",
+]
+
+[[package]]
 name = "memoffset"
 version = "0.5.5"
 source = "registry+https://github.com/rust-lang/crates.io-index"
@@ -3782,7 +3791,7 @@ dependencies = [
  "itertools 0.9.0",
  "jobserver",
  "libc",
- "memmap",
+ "memmap2",
  "pathdiff",
  "rustc_apfloat",
  "rustc_ast",
@@ -4116,7 +4125,7 @@ name = "rustc_metadata"
 version = "0.0.0"
 dependencies = [
  "libc",
- "memmap",
+ "memmap2",
  "rustc_ast",
  "rustc_attr",
  "rustc_data_structures",
diff --git a/compiler/rustc_arena/src/lib.rs b/compiler/rustc_arena/src/lib.rs
index a9917f50cc2..c3198fb1043 100644
--- a/compiler/rustc_arena/src/lib.rs
+++ b/compiler/rustc_arena/src/lib.rs
@@ -298,22 +298,6 @@ impl<T> TypedArena<T> {
         }
     }
 
-    /// Clears the arena. Deallocates all but the longest chunk which may be reused.
-    pub fn clear(&mut self) {
-        unsafe {
-            // Clear the last chunk, which is partially filled.
-            let mut chunks_borrow = self.chunks.borrow_mut();
-            if let Some(mut last_chunk) = chunks_borrow.last_mut() {
-                self.clear_last_chunk(&mut last_chunk);
-                let len = chunks_borrow.len();
-                // If `T` is ZST, code below has no effect.
-                for mut chunk in chunks_borrow.drain(..len - 1) {
-                    chunk.destroy(chunk.entries);
-                }
-            }
-        }
-    }
-
     // Drops the contents of the last chunk. The last chunk is partially empty, unlike all other
     // chunks.
     fn clear_last_chunk(&self, last_chunk: &mut TypedArenaChunk<T>) {
diff --git a/compiler/rustc_arena/src/tests.rs b/compiler/rustc_arena/src/tests.rs
index e8a1f2db1a1..911e577c1ed 100644
--- a/compiler/rustc_arena/src/tests.rs
+++ b/compiler/rustc_arena/src/tests.rs
@@ -11,6 +11,24 @@ struct Point {
     z: i32,
 }
 
+impl<T> TypedArena<T> {
+    /// Clears the arena. Deallocates all but the longest chunk which may be reused.
+    fn clear(&mut self) {
+        unsafe {
+            // Clear the last chunk, which is partially filled.
+            let mut chunks_borrow = self.chunks.borrow_mut();
+            if let Some(mut last_chunk) = chunks_borrow.last_mut() {
+                self.clear_last_chunk(&mut last_chunk);
+                let len = chunks_borrow.len();
+                // If `T` is ZST, code below has no effect.
+                for mut chunk in chunks_borrow.drain(..len - 1) {
+                    chunk.destroy(chunk.entries);
+                }
+            }
+        }
+    }
+}
+
 #[test]
 pub fn test_unused() {
     let arena: TypedArena<Point> = TypedArena::default();
diff --git a/compiler/rustc_codegen_ssa/Cargo.toml b/compiler/rustc_codegen_ssa/Cargo.toml
index 5e2f01b2c9d..15dbbbd49aa 100644
--- a/compiler/rustc_codegen_ssa/Cargo.toml
+++ b/compiler/rustc_codegen_ssa/Cargo.toml
@@ -11,7 +11,7 @@ test = false
 bitflags = "1.2.1"
 cc = "1.0.1"
 itertools = "0.9"
-memmap = "0.7"
+memmap2 = "0.2.1"
 tracing = "0.1"
 libc = "0.2.50"
 jobserver = "0.1.11"
diff --git a/compiler/rustc_codegen_ssa/src/back/lto.rs b/compiler/rustc_codegen_ssa/src/back/lto.rs
index 0d7f4447696..c6aea22a63e 100644
--- a/compiler/rustc_codegen_ssa/src/back/lto.rs
+++ b/compiler/rustc_codegen_ssa/src/back/lto.rs
@@ -93,7 +93,7 @@ impl<B: WriteBackendMethods> LtoModuleCodegen<B> {
 pub enum SerializedModule<M: ModuleBufferMethods> {
     Local(M),
     FromRlib(Vec<u8>),
-    FromUncompressedFile(memmap::Mmap),
+    FromUncompressedFile(memmap2::Mmap),
 }
 
 impl<M: ModuleBufferMethods> SerializedModule<M> {
diff --git a/compiler/rustc_codegen_ssa/src/back/write.rs b/compiler/rustc_codegen_ssa/src/back/write.rs
index 854aaac757f..490b3d33112 100644
--- a/compiler/rustc_codegen_ssa/src/back/write.rs
+++ b/compiler/rustc_codegen_ssa/src/back/write.rs
@@ -1958,7 +1958,7 @@ pub fn submit_pre_lto_module_to_llvm<B: ExtraBackendMethods>(
         .unwrap_or_else(|e| panic!("failed to open bitcode file `{}`: {}", bc_path.display(), e));
 
     let mmap = unsafe {
-        memmap::Mmap::map(&file).unwrap_or_else(|e| {
+        memmap2::Mmap::map(&file).unwrap_or_else(|e| {
             panic!("failed to mmap bitcode file `{}`: {}", bc_path.display(), e)
         })
     };
diff --git a/compiler/rustc_codegen_ssa/src/lib.rs b/compiler/rustc_codegen_ssa/src/lib.rs
index 2c2330409fd..dd04d3e548f 100644
--- a/compiler/rustc_codegen_ssa/src/lib.rs
+++ b/compiler/rustc_codegen_ssa/src/lib.rs
@@ -1,6 +1,6 @@
 #![doc(html_root_url = "https://doc.rust-lang.org/nightly/nightly-rustc/")]
+#![feature(assert_matches)]
 #![feature(bool_to_option)]
-#![feature(option_expect_none)]
 #![feature(box_patterns)]
 #![feature(drain_filter)]
 #![feature(try_blocks)]
diff --git a/compiler/rustc_data_structures/src/tiny_list.rs b/compiler/rustc_data_structures/src/tiny_list.rs
index e94a0c6eb59..f88bcc29481 100644
--- a/compiler/rustc_data_structures/src/tiny_list.rs
+++ b/compiler/rustc_data_structures/src/tiny_list.rs
@@ -15,7 +15,7 @@
 mod tests;
 
 #[derive(Clone)]
-pub struct TinyList<T: PartialEq> {
+pub struct TinyList<T> {
     head: Option<Element<T>>,
 }
 
@@ -56,20 +56,10 @@ impl<T: PartialEq> TinyList<T> {
         }
         false
     }
-
-    #[inline]
-    pub fn len(&self) -> usize {
-        let (mut elem, mut count) = (self.head.as_ref(), 0);
-        while let Some(ref e) = elem {
-            count += 1;
-            elem = e.next.as_deref();
-        }
-        count
-    }
 }
 
 #[derive(Clone)]
-struct Element<T: PartialEq> {
+struct Element<T> {
     data: T,
     next: Option<Box<Element<T>>>,
 }
diff --git a/compiler/rustc_data_structures/src/tiny_list/tests.rs b/compiler/rustc_data_structures/src/tiny_list/tests.rs
index a8ae2bc8727..c0334d2e23e 100644
--- a/compiler/rustc_data_structures/src/tiny_list/tests.rs
+++ b/compiler/rustc_data_structures/src/tiny_list/tests.rs
@@ -3,6 +3,17 @@ use super::*;
 extern crate test;
 use test::{black_box, Bencher};
 
+impl<T> TinyList<T> {
+    fn len(&self) -> usize {
+        let (mut elem, mut count) = (self.head.as_ref(), 0);
+        while let Some(ref e) = elem {
+            count += 1;
+            elem = e.next.as_deref();
+        }
+        count
+    }
+}
+
 #[test]
 fn test_contains_and_insert() {
     fn do_insert(i: u32) -> bool {
diff --git a/compiler/rustc_data_structures/src/transitive_relation.rs b/compiler/rustc_data_structures/src/transitive_relation.rs
index 2e1512b3929..ccf8bd69ebd 100644
--- a/compiler/rustc_data_structures/src/transitive_relation.rs
+++ b/compiler/rustc_data_structures/src/transitive_relation.rs
@@ -9,7 +9,7 @@ use std::mem;
 mod tests;
 
 #[derive(Clone, Debug)]
-pub struct TransitiveRelation<T: Eq + Hash> {
+pub struct TransitiveRelation<T> {
     // List of elements. This is used to map from a T to a usize.
     elements: FxIndexSet<T>,
 
@@ -49,7 +49,7 @@ struct Edge {
     target: Index,
 }
 
-impl<T: Clone + Debug + Eq + Hash> TransitiveRelation<T> {
+impl<T: Eq + Hash> TransitiveRelation<T> {
     pub fn is_empty(&self) -> bool {
         self.edges.is_empty()
     }
@@ -322,12 +322,6 @@ impl<T: Clone + Debug + Eq + Hash> TransitiveRelation<T> {
             .collect()
     }
 
-    /// A "best" parent in some sense. See `parents` and
-    /// `postdom_upper_bound` for more details.
-    pub fn postdom_parent(&self, a: &T) -> Option<&T> {
-        self.mutual_immediate_postdominator(self.parents(a))
-    }
-
     fn with_closure<OP, R>(&self, op: OP) -> R
     where
         OP: FnOnce(&BitMatrix<usize, usize>) -> R,
diff --git a/compiler/rustc_data_structures/src/transitive_relation/tests.rs b/compiler/rustc_data_structures/src/transitive_relation/tests.rs
index ca90ba176ae..9fa7224376c 100644
--- a/compiler/rustc_data_structures/src/transitive_relation/tests.rs
+++ b/compiler/rustc_data_structures/src/transitive_relation/tests.rs
@@ -1,5 +1,13 @@
 use super::*;
 
+impl<T: Eq + Hash> TransitiveRelation<T> {
+    /// A "best" parent in some sense. See `parents` and
+    /// `postdom_upper_bound` for more details.
+    fn postdom_parent(&self, a: &T) -> Option<&T> {
+        self.mutual_immediate_postdominator(self.parents(a))
+    }
+}
+
 #[test]
 fn test_one_step() {
     let mut relation = TransitiveRelation::default();
diff --git a/compiler/rustc_errors/src/diagnostic_builder.rs b/compiler/rustc_errors/src/diagnostic_builder.rs
index c09cce21bf2..79507e61522 100644
--- a/compiler/rustc_errors/src/diagnostic_builder.rs
+++ b/compiler/rustc_errors/src/diagnostic_builder.rs
@@ -30,15 +30,6 @@ struct DiagnosticBuilderInner<'a> {
     allow_suggestions: bool,
 }
 
-/// This is a helper macro for [`forward!`] that allows automatically adding documentation
-/// that uses tokens from [`forward!`]'s input.
-macro_rules! forward_inner_docs {
-    ($e:expr => $i:item) => {
-        #[doc = $e]
-        $i
-    };
-}
-
 /// In general, the `DiagnosticBuilder` uses deref to allow access to
 /// the fields and methods of the embedded `diagnostic` in a
 /// transparent way. *However,* many of the methods are intended to
@@ -54,11 +45,11 @@ macro_rules! forward {
         pub fn $n:ident(&self, $($name:ident: $ty:ty),* $(,)?) -> &Self
     ) => {
         $(#[$attrs])*
-        forward_inner_docs!(concat!("See [`Diagnostic::", stringify!($n), "()`].") =>
+        #[doc = concat!("See [`Diagnostic::", stringify!($n), "()`].")]
         pub fn $n(&self, $($name: $ty),*) -> &Self {
             self.diagnostic.$n($($name),*);
             self
-        });
+        }
     };
 
     // Forward pattern for &mut self -> &mut Self
@@ -67,11 +58,11 @@ macro_rules! forward {
         pub fn $n:ident(&mut self, $($name:ident: $ty:ty),* $(,)?) -> &mut Self
     ) => {
         $(#[$attrs])*
-        forward_inner_docs!(concat!("See [`Diagnostic::", stringify!($n), "()`].") =>
+        #[doc = concat!("See [`Diagnostic::", stringify!($n), "()`].")]
         pub fn $n(&mut self, $($name: $ty),*) -> &mut Self {
             self.0.diagnostic.$n($($name),*);
             self
-        });
+        }
     };
 
     // Forward pattern for &mut self -> &mut Self, with generic parameters.
@@ -84,11 +75,11 @@ macro_rules! forward {
         ) -> &mut Self
     ) => {
         $(#[$attrs])*
-        forward_inner_docs!(concat!("See [`Diagnostic::", stringify!($n), "()`].") =>
+        #[doc = concat!("See [`Diagnostic::", stringify!($n), "()`].")]
         pub fn $n<$($generic: $bound),*>(&mut self, $($name: $ty),*) -> &mut Self {
             self.0.diagnostic.$n($($name),*);
             self
-        });
+        }
     };
 }
 
diff --git a/compiler/rustc_errors/src/lib.rs b/compiler/rustc_errors/src/lib.rs
index 1db39fbfba5..fa855f544e8 100644
--- a/compiler/rustc_errors/src/lib.rs
+++ b/compiler/rustc_errors/src/lib.rs
@@ -5,6 +5,7 @@
 #![doc(html_root_url = "https://doc.rust-lang.org/nightly/nightly-rustc/")]
 #![feature(crate_visibility_modifier)]
 #![feature(backtrace)]
+#![feature(extended_key_value_attributes)]
 #![feature(nll)]
 
 #[macro_use]
diff --git a/compiler/rustc_expand/src/proc_macro_server.rs b/compiler/rustc_expand/src/proc_macro_server.rs
index 67edfe19da3..cb41bc81225 100644
--- a/compiler/rustc_expand/src/proc_macro_server.rs
+++ b/compiler/rustc_expand/src/proc_macro_server.rs
@@ -53,11 +53,11 @@ impl ToInternal<token::DelimToken> for Delimiter {
     }
 }
 
-impl FromInternal<(TreeAndSpacing, &'_ ParseSess, &'_ mut Vec<Self>)>
+impl FromInternal<(TreeAndSpacing, &'_ mut Vec<Self>, &mut Rustc<'_>)>
     for TokenTree<Group, Punct, Ident, Literal>
 {
     fn from_internal(
-        ((tree, spacing), sess, stack): (TreeAndSpacing, &ParseSess, &mut Vec<Self>),
+        ((tree, spacing), stack, rustc): (TreeAndSpacing, &mut Vec<Self>, &mut Rustc<'_>),
     ) -> Self {
         use rustc_ast::token::*;
 
@@ -146,10 +146,10 @@ impl FromInternal<(TreeAndSpacing, &'_ ParseSess, &'_ mut Vec<Self>)>
             SingleQuote => op!('\''),
 
             Ident(name, false) if name == kw::DollarCrate => tt!(Ident::dollar_crate()),
-            Ident(name, is_raw) => tt!(Ident::new(sess, name, is_raw)),
+            Ident(name, is_raw) => tt!(Ident::new(rustc.sess, name, is_raw)),
             Lifetime(name) => {
                 let ident = symbol::Ident::new(name, span).without_first_quote();
-                stack.push(tt!(Ident::new(sess, ident.name, false)));
+                stack.push(tt!(Ident::new(rustc.sess, ident.name, false)));
                 tt!(Punct::new('\'', true))
             }
             Literal(lit) => tt!(Literal { lit }),
@@ -179,15 +179,15 @@ impl FromInternal<(TreeAndSpacing, &'_ ParseSess, &'_ mut Vec<Self>)>
             }
 
             Interpolated(nt) => {
-                if let Some((name, is_raw)) = ident_name_compatibility_hack(&nt, span, sess) {
-                    TokenTree::Ident(Ident::new(sess, name.name, is_raw, name.span))
+                if let Some((name, is_raw)) = ident_name_compatibility_hack(&nt, span, rustc) {
+                    TokenTree::Ident(Ident::new(rustc.sess, name.name, is_raw, name.span))
                 } else {
-                    let stream = nt_to_tokenstream(&nt, sess, CanSynthesizeMissingTokens::No);
+                    let stream = nt_to_tokenstream(&nt, rustc.sess, CanSynthesizeMissingTokens::No);
                     TokenTree::Group(Group {
                         delimiter: Delimiter::None,
                         stream,
                         span: DelimSpan::from_single(span),
-                        flatten: crate::base::pretty_printing_compatibility_hack(&nt, sess),
+                        flatten: crate::base::pretty_printing_compatibility_hack(&nt, rustc.sess),
                     })
                 }
             }
@@ -449,7 +449,7 @@ impl server::TokenStreamIter for Rustc<'_> {
         loop {
             let tree = iter.stack.pop().or_else(|| {
                 let next = iter.cursor.next_with_spacing()?;
-                Some(TokenTree::from_internal((next, self.sess, &mut iter.stack)))
+                Some(TokenTree::from_internal((next, &mut iter.stack, self)))
             })?;
             // A hack used to pass AST fragments to attribute and derive macros
             // as a single nonterminal token instead of a token stream.
@@ -719,11 +719,11 @@ impl server::Span for Rustc<'_> {
 fn ident_name_compatibility_hack(
     nt: &Nonterminal,
     orig_span: Span,
-    sess: &ParseSess,
+    rustc: &mut Rustc<'_>,
 ) -> Option<(rustc_span::symbol::Ident, bool)> {
     if let NtIdent(ident, is_raw) = nt {
         if let ExpnKind::Macro(_, macro_name) = orig_span.ctxt().outer_expn_data().kind {
-            let source_map = sess.source_map();
+            let source_map = rustc.sess.source_map();
             let filename = source_map.span_to_filename(orig_span);
             if let FileName::Real(RealFileName::Named(path)) = filename {
                 let matches_prefix = |prefix, filename| {
@@ -745,7 +745,7 @@ fn ident_name_compatibility_hack(
                     let snippet = source_map.span_to_snippet(orig_span);
                     if snippet.as_deref() == Ok("$name") {
                         if time_macros_impl {
-                            sess.buffer_lint_with_diagnostic(
+                            rustc.sess.buffer_lint_with_diagnostic(
                                 &PROC_MACRO_BACK_COMPAT,
                                 orig_span,
                                 ast::CRATE_NODE_ID,
@@ -759,13 +759,25 @@ fn ident_name_compatibility_hack(
                     }
                 }
 
-                if macro_name == sym::tuple_from_req
-                    && (matches_prefix("actix-web", "extract.rs")
-                        || matches_prefix("actori-web", "extract.rs"))
-                {
+                if macro_name == sym::tuple_from_req && matches_prefix("actix-web", "extract.rs") {
                     let snippet = source_map.span_to_snippet(orig_span);
                     if snippet.as_deref() == Ok("$T") {
-                        return Some((*ident, *is_raw));
+                        if let FileName::Real(RealFileName::Named(macro_path)) =
+                            source_map.span_to_filename(rustc.def_site)
+                        {
+                            if macro_path.to_string_lossy().contains("pin-project-internal-0.") {
+                                rustc.sess.buffer_lint_with_diagnostic(
+                                    &PROC_MACRO_BACK_COMPAT,
+                                    orig_span,
+                                    ast::CRATE_NODE_ID,
+                                    "using an old version of `actix-web`",
+                                    BuiltinLintDiagnostics::ProcMacroBackCompat(
+                                    "the version of `actix-web` you are using might stop compiling in future versions of Rust; \
+                                    please update to the latest version of the `actix-web` crate to avoid breakage".to_string())
+                                );
+                                return Some((*ident, *is_raw));
+                            }
+                        }
                     }
                 }
             }
diff --git a/compiler/rustc_metadata/Cargo.toml b/compiler/rustc_metadata/Cargo.toml
index 2aabc2c407b..48effed9274 100644
--- a/compiler/rustc_metadata/Cargo.toml
+++ b/compiler/rustc_metadata/Cargo.toml
@@ -11,7 +11,7 @@ doctest = false
 libc = "0.2"
 snap = "1"
 tracing = "0.1"
-memmap = "0.7"
+memmap2 = "0.2.1"
 smallvec = { version = "1.6.1", features = ["union", "may_dangle"] }
 rustc_middle = { path = "../rustc_middle" }
 rustc_attr = { path = "../rustc_attr" }
diff --git a/compiler/rustc_metadata/src/locator.rs b/compiler/rustc_metadata/src/locator.rs
index a9f58b08f58..39a39917f57 100644
--- a/compiler/rustc_metadata/src/locator.rs
+++ b/compiler/rustc_metadata/src/locator.rs
@@ -728,7 +728,7 @@ impl<'a> CrateLocator<'a> {
 }
 
 /// A trivial wrapper for `Mmap` that implements `StableDeref`.
-struct StableDerefMmap(memmap::Mmap);
+struct StableDerefMmap(memmap2::Mmap);
 
 impl Deref for StableDerefMmap {
     type Target = [u8];
@@ -779,7 +779,7 @@ fn get_metadata_section(
             // mmap the file, because only a small fraction of it is read.
             let file = std::fs::File::open(filename)
                 .map_err(|_| format!("failed to open rmeta metadata: '{}'", filename.display()))?;
-            let mmap = unsafe { memmap::Mmap::map(&file) };
+            let mmap = unsafe { memmap2::Mmap::map(&file) };
             let mmap = mmap
                 .map_err(|_| format!("failed to mmap rmeta metadata: '{}'", filename.display()))?;
 
diff --git a/compiler/rustc_middle/src/ich/impls_syntax.rs b/compiler/rustc_middle/src/ich/impls_syntax.rs
index bfbe15749ee..31374429940 100644
--- a/compiler/rustc_middle/src/ich/impls_syntax.rs
+++ b/compiler/rustc_middle/src/ich/impls_syntax.rs
@@ -45,7 +45,11 @@ impl<'ctx> rustc_ast::HashStableContext for StableHashingContext<'ctx> {
             item.hash_stable(self, hasher);
             style.hash_stable(self, hasher);
             span.hash_stable(self, hasher);
-            tokens.as_ref().expect_none("Tokens should have been removed during lowering!");
+            assert_matches!(
+                tokens.as_ref(),
+                None,
+                "Tokens should have been removed during lowering!"
+            );
         } else {
             unreachable!();
         }
diff --git a/compiler/rustc_middle/src/lib.rs b/compiler/rustc_middle/src/lib.rs
index d9e88265050..2d807591bfd 100644
--- a/compiler/rustc_middle/src/lib.rs
+++ b/compiler/rustc_middle/src/lib.rs
@@ -24,6 +24,7 @@
 
 #![doc(html_root_url = "https://doc.rust-lang.org/nightly/nightly-rustc/")]
 #![feature(array_windows)]
+#![feature(assert_matches)]
 #![feature(assoc_char_funcs)]
 #![feature(backtrace)]
 #![feature(bool_to_option)]
@@ -38,7 +39,6 @@
 #![feature(extern_types)]
 #![feature(nll)]
 #![feature(once_cell)]
-#![feature(option_expect_none)]
 #![feature(or_patterns)]
 #![feature(min_specialization)]
 #![feature(trusted_len)]
diff --git a/compiler/rustc_middle/src/mir/interpret/allocation.rs b/compiler/rustc_middle/src/mir/interpret/allocation.rs
index 48595f2badc..766d6a06f7e 100644
--- a/compiler/rustc_middle/src/mir/interpret/allocation.rs
+++ b/compiler/rustc_middle/src/mir/interpret/allocation.rs
@@ -339,7 +339,7 @@ impl<'tcx, Tag: Copy, Extra: AllocationExtra<Tag>> Allocation<Tag, Extra> {
         for dest in bytes {
             *dest = src.next().expect("iterator was shorter than it said it would be");
         }
-        src.next().expect_none("iterator was longer than it said it would be");
+        assert_matches!(src.next(), None, "iterator was longer than it said it would be");
         Ok(())
     }
 
diff --git a/compiler/rustc_mir/src/interpret/memory.rs b/compiler/rustc_mir/src/interpret/memory.rs
index f3e373813ca..fe5ebf0b6fe 100644
--- a/compiler/rustc_mir/src/interpret/memory.rs
+++ b/compiler/rustc_mir/src/interpret/memory.rs
@@ -854,7 +854,11 @@ impl<'mir, 'tcx, M: Machine<'mir, 'tcx>> Memory<'mir, 'tcx, M> {
             Some(ptr) => ptr,
             None => {
                 // zero-sized access
-                src.next().expect_none("iterator said it was empty but returned an element");
+                assert_matches!(
+                    src.next(),
+                    None,
+                    "iterator said it was empty but returned an element"
+                );
                 return Ok(());
             }
         };
@@ -880,7 +884,11 @@ impl<'mir, 'tcx, M: Machine<'mir, 'tcx>> Memory<'mir, 'tcx, M> {
             Some(ptr) => ptr,
             None => {
                 // zero-sized access
-                src.next().expect_none("iterator said it was empty but returned an element");
+                assert_matches!(
+                    src.next(),
+                    None,
+                    "iterator said it was empty but returned an element"
+                );
                 return Ok(());
             }
         };
@@ -894,7 +902,7 @@ impl<'mir, 'tcx, M: Machine<'mir, 'tcx>> Memory<'mir, 'tcx, M> {
             let offset_ptr = ptr.offset(Size::from_bytes(idx) * 2, &tcx)?; // `Size` multiplication
             allocation.write_scalar(&tcx, offset_ptr, val.into(), Size::from_bytes(2))?;
         }
-        src.next().expect_none("iterator was longer than it said it would be");
+        assert_matches!(src.next(), None, "iterator was longer than it said it would be");
         Ok(())
     }
 
diff --git a/compiler/rustc_mir/src/lib.rs b/compiler/rustc_mir/src/lib.rs
index 194bc74c0fb..f73d5dc0c11 100644
--- a/compiler/rustc_mir/src/lib.rs
+++ b/compiler/rustc_mir/src/lib.rs
@@ -7,6 +7,7 @@ Rust MIR: a lowered representation of Rust.
 #![feature(nll)]
 #![feature(in_band_lifetimes)]
 #![feature(array_windows)]
+#![feature(assert_matches)]
 #![feature(bindings_after_at)]
 #![feature(bool_to_option)]
 #![feature(box_patterns)]
@@ -18,13 +19,13 @@ Rust MIR: a lowered representation of Rust.
 #![feature(exact_size_is_empty)]
 #![feature(exhaustive_patterns)]
 #![feature(never_type)]
+#![feature(map_try_insert)]
 #![feature(min_specialization)]
 #![feature(trusted_len)]
 #![feature(try_blocks)]
 #![feature(associated_type_defaults)]
 #![feature(stmt_expr_attributes)]
 #![feature(trait_alias)]
-#![feature(option_expect_none)]
 #![feature(option_get_or_insert_default)]
 #![feature(or_patterns)]
 #![feature(once_cell)]
diff --git a/compiler/rustc_mir/src/transform/coverage/debug.rs b/compiler/rustc_mir/src/transform/coverage/debug.rs
index 2cd0dc6b1f2..aabfee53acb 100644
--- a/compiler/rustc_mir/src/transform/coverage/debug.rs
+++ b/compiler/rustc_mir/src/transform/coverage/debug.rs
@@ -285,10 +285,8 @@ impl DebugCounters {
                 ),
             };
             counters
-                .insert(id, DebugCounter::new(counter_kind.clone(), some_block_label))
-                .expect_none(
-                    "attempt to add the same counter_kind to DebugCounters more than once",
-                );
+                .try_insert(id, DebugCounter::new(counter_kind.clone(), some_block_label))
+                .expect("attempt to add the same counter_kind to DebugCounters more than once");
         }
     }
 
@@ -479,9 +477,9 @@ impl GraphvizData {
         counter_kind: &CoverageKind,
     ) {
         if let Some(edge_to_counter) = self.some_edge_to_counter.as_mut() {
-            edge_to_counter.insert((from_bcb, to_bb), counter_kind.clone()).expect_none(
-                "invalid attempt to insert more than one edge counter for the same edge",
-            );
+            edge_to_counter
+                .try_insert((from_bcb, to_bb), counter_kind.clone())
+                .expect("invalid attempt to insert more than one edge counter for the same edge");
         }
     }
 
diff --git a/compiler/rustc_mir/src/transform/deduplicate_blocks.rs b/compiler/rustc_mir/src/transform/deduplicate_blocks.rs
index c4b51099f53..e102512e1f3 100644
--- a/compiler/rustc_mir/src/transform/deduplicate_blocks.rs
+++ b/compiler/rustc_mir/src/transform/deduplicate_blocks.rs
@@ -86,7 +86,7 @@ fn find_duplicates<'a, 'tcx>(body: &'a Body<'tcx>) -> FxHashMap<BasicBlock, Basi
                 // The basic block was already in the hashmap, which means we have a duplicate
                 let value = *occupied.get();
                 debug!("Inserting {:?} -> {:?}", bb, value);
-                duplicates.insert(bb, value).expect_none("key was already inserted");
+                duplicates.try_insert(bb, value).expect("key was already inserted");
             }
             Entry::Vacant(vacant) => {
                 vacant.insert(bb);
diff --git a/compiler/rustc_passes/src/check_attr.rs b/compiler/rustc_passes/src/check_attr.rs
index 775e27e68f8..d91d0e1765b 100644
--- a/compiler/rustc_passes/src/check_attr.rs
+++ b/compiler/rustc_passes/src/check_attr.rs
@@ -394,33 +394,50 @@ impl CheckAttrVisitor<'tcx> {
             .emit();
     }
 
-    fn check_doc_alias(&self, meta: &NestedMetaItem, hir_id: HirId, target: Target) -> bool {
-        let doc_alias = meta.value_str().map(|s| s.to_string()).unwrap_or_else(String::new);
+    fn check_doc_alias_value(
+        &self,
+        meta: &NestedMetaItem,
+        doc_alias: &str,
+        hir_id: HirId,
+        target: Target,
+        is_list: bool,
+    ) -> bool {
+        let tcx = self.tcx;
+        let err_fn = move |span: Span, msg: &str| {
+            tcx.sess.span_err(
+                span,
+                &format!(
+                    "`#[doc(alias{})]` {}",
+                    if is_list { "(\"...\")" } else { " = \"...\"" },
+                    msg,
+                ),
+            );
+            false
+        };
         if doc_alias.is_empty() {
-            self.doc_attr_str_error(meta, "alias");
-            return false;
+            return err_fn(
+                meta.name_value_literal_span().unwrap_or_else(|| meta.span()),
+                "attribute cannot have empty value",
+            );
         }
         if let Some(c) =
             doc_alias.chars().find(|&c| c == '"' || c == '\'' || (c.is_whitespace() && c != ' '))
         {
-            self.tcx
-                .sess
-                .struct_span_err(
-                    meta.name_value_literal_span().unwrap_or_else(|| meta.span()),
-                    &format!("{:?} character isn't allowed in `#[doc(alias = \"...\")]`", c),
-                )
-                .emit();
+            self.tcx.sess.span_err(
+                meta.name_value_literal_span().unwrap_or_else(|| meta.span()),
+                &format!(
+                    "{:?} character isn't allowed in `#[doc(alias{})]`",
+                    c,
+                    if is_list { "(\"...\")" } else { " = \"...\"" },
+                ),
+            );
             return false;
         }
         if doc_alias.starts_with(' ') || doc_alias.ends_with(' ') {
-            self.tcx
-                .sess
-                .struct_span_err(
-                    meta.name_value_literal_span().unwrap_or_else(|| meta.span()),
-                    "`#[doc(alias = \"...\")]` cannot start or end with ' '",
-                )
-                .emit();
-            return false;
+            return err_fn(
+                meta.name_value_literal_span().unwrap_or_else(|| meta.span()),
+                "cannot start or end with ' '",
+            );
         }
         if let Some(err) = match target {
             Target::Impl => Some("implementation block"),
@@ -446,27 +463,63 @@ impl CheckAttrVisitor<'tcx> {
             }
             _ => None,
         } {
-            self.tcx
-                .sess
-                .struct_span_err(
-                    meta.span(),
-                    &format!("`#[doc(alias = \"...\")]` isn't allowed on {}", err),
-                )
-                .emit();
-            return false;
+            return err_fn(meta.span(), &format!("isn't allowed on {}", err));
         }
         let item_name = self.tcx.hir().name(hir_id);
         if &*item_name.as_str() == doc_alias {
+            return err_fn(meta.span(), "is the same as the item's name");
+        }
+        true
+    }
+
+    fn check_doc_alias(&self, meta: &NestedMetaItem, hir_id: HirId, target: Target) -> bool {
+        if let Some(values) = meta.meta_item_list() {
+            let mut errors = 0;
+            for v in values {
+                match v.literal() {
+                    Some(l) => match l.kind {
+                        LitKind::Str(s, _) => {
+                            if !self.check_doc_alias_value(v, &s.as_str(), hir_id, target, true) {
+                                errors += 1;
+                            }
+                        }
+                        _ => {
+                            self.tcx
+                                .sess
+                                .struct_span_err(
+                                    v.span(),
+                                    "`#[doc(alias(\"a\"))]` expects string literals",
+                                )
+                                .emit();
+                            errors += 1;
+                        }
+                    },
+                    None => {
+                        self.tcx
+                            .sess
+                            .struct_span_err(
+                                v.span(),
+                                "`#[doc(alias(\"a\"))]` expects string literals",
+                            )
+                            .emit();
+                        errors += 1;
+                    }
+                }
+            }
+            errors == 0
+        } else if let Some(doc_alias) = meta.value_str().map(|s| s.to_string()) {
+            self.check_doc_alias_value(meta, &doc_alias, hir_id, target, false)
+        } else {
             self.tcx
                 .sess
                 .struct_span_err(
                     meta.span(),
-                    &format!("`#[doc(alias = \"...\")]` is the same as the item's name"),
+                    "doc alias attribute expects a string `#[doc(alias = \"a\")]` or a list of \
+                     strings `#[doc(alias(\"a\", \"b\"))]`",
                 )
                 .emit();
-            return false;
+            false
         }
-        true
     }
 
     fn check_doc_keyword(&self, meta: &NestedMetaItem, hir_id: HirId) -> bool {
diff --git a/compiler/rustc_span/src/hygiene.rs b/compiler/rustc_span/src/hygiene.rs
index e67a4ca8fb2..eb5b7c4a74a 100644
--- a/compiler/rustc_span/src/hygiene.rs
+++ b/compiler/rustc_span/src/hygiene.rs
@@ -118,7 +118,8 @@ impl ExpnId {
         HygieneData::with(|data| {
             let old_expn_data = &mut data.expn_data[self.0 as usize];
             assert!(old_expn_data.is_none(), "expansion data is reset for an expansion ID");
-            expn_data.orig_id.replace(self.as_u32()).expect_none("orig_id should be None");
+            assert_eq!(expn_data.orig_id, None);
+            expn_data.orig_id = Some(self.as_u32());
             *old_expn_data = Some(expn_data);
         });
         update_disambiguator(self)
@@ -202,7 +203,8 @@ impl HygieneData {
     fn fresh_expn(&mut self, mut expn_data: Option<ExpnData>) -> ExpnId {
         let raw_id = self.expn_data.len() as u32;
         if let Some(data) = expn_data.as_mut() {
-            data.orig_id.replace(raw_id).expect_none("orig_id should be None");
+            assert_eq!(data.orig_id, None);
+            data.orig_id = Some(raw_id);
         }
         self.expn_data.push(expn_data);
         ExpnId(raw_id)
@@ -1410,9 +1412,11 @@ fn update_disambiguator(expn_id: ExpnId) {
             let new_hash: Fingerprint = hasher.finish();
 
             HygieneData::with(|data| {
-                data.expn_data_disambiguators
-                    .get(&new_hash)
-                    .expect_none("Hash collision after disambiguator update!");
+                assert_eq!(
+                    data.expn_data_disambiguators.get(&new_hash),
+                    None,
+                    "Hash collision after disambiguator update!",
+                );
             });
         };
     }
diff --git a/compiler/rustc_span/src/lib.rs b/compiler/rustc_span/src/lib.rs
index 6030c8a86d9..d2790335b5a 100644
--- a/compiler/rustc_span/src/lib.rs
+++ b/compiler/rustc_span/src/lib.rs
@@ -21,7 +21,6 @@
 #![feature(negative_impls)]
 #![feature(nll)]
 #![feature(min_specialization)]
-#![feature(option_expect_none)]
 
 #[macro_use]
 extern crate rustc_macros;
@@ -1996,7 +1995,8 @@ impl<CTX: HashStableContext> HashStable<CTX> for ExpnId {
                 if cache.len() < new_len {
                     cache.resize(new_len, None);
                 }
-                cache[index].replace(sub_hash).expect_none("Cache slot was filled");
+                let prev = cache[index].replace(sub_hash);
+                assert_eq!(prev, None, "Cache slot was filled");
             });
             sub_hash.hash_stable(ctx, hasher);
         }
diff --git a/compiler/rustc_span/src/source_map.rs b/compiler/rustc_span/src/source_map.rs
index b7eb6d5b379..f612d1425b9 100644
--- a/compiler/rustc_span/src/source_map.rs
+++ b/compiler/rustc_span/src/source_map.rs
@@ -453,41 +453,6 @@ impl SourceMap {
         }
     }
 
-    /// Returns `Some(span)`, a union of the LHS and RHS span. The LHS must precede the RHS. If
-    /// there are gaps between LHS and RHS, the resulting union will cross these gaps.
-    /// For this to work,
-    ///
-    ///    * the syntax contexts of both spans much match,
-    ///    * the LHS span needs to end on the same line the RHS span begins,
-    ///    * the LHS span must start at or before the RHS span.
-    pub fn merge_spans(&self, sp_lhs: Span, sp_rhs: Span) -> Option<Span> {
-        // Ensure we're at the same expansion ID.
-        if sp_lhs.ctxt() != sp_rhs.ctxt() {
-            return None;
-        }
-
-        let lhs_end = match self.lookup_line(sp_lhs.hi()) {
-            Ok(x) => x,
-            Err(_) => return None,
-        };
-        let rhs_begin = match self.lookup_line(sp_rhs.lo()) {
-            Ok(x) => x,
-            Err(_) => return None,
-        };
-
-        // If we must cross lines to merge, don't merge.
-        if lhs_end.line != rhs_begin.line {
-            return None;
-        }
-
-        // Ensure these follow the expected order and that we don't overlap.
-        if (sp_lhs.lo() <= sp_rhs.lo()) && (sp_lhs.hi() <= sp_rhs.lo()) {
-            Some(sp_lhs.to(sp_rhs))
-        } else {
-            None
-        }
-    }
-
     pub fn span_to_string(&self, sp: Span) -> String {
         if self.files.borrow().source_files.is_empty() && sp.is_dummy() {
             return "no-location".to_string();
@@ -931,13 +896,6 @@ impl SourceMap {
         SourceFileAndBytePos { sf, pos: offset }
     }
 
-    /// Converts an absolute `BytePos` to a `CharPos` relative to the `SourceFile`.
-    pub fn bytepos_to_file_charpos(&self, bpos: BytePos) -> CharPos {
-        let idx = self.lookup_source_file_idx(bpos);
-        let sf = &(*self.files.borrow().source_files)[idx];
-        sf.bytepos_to_file_charpos(bpos)
-    }
-
     // Returns the index of the `SourceFile` (in `self.files`) that contains `pos`.
     // This index is guaranteed to be valid for the lifetime of this `SourceMap`,
     // since `source_files` is a `MonotonicVec`
diff --git a/compiler/rustc_span/src/source_map/tests.rs b/compiler/rustc_span/src/source_map/tests.rs
index 0aca677248b..7d814f1d82c 100644
--- a/compiler/rustc_span/src/source_map/tests.rs
+++ b/compiler/rustc_span/src/source_map/tests.rs
@@ -10,6 +10,50 @@ fn init_source_map() -> SourceMap {
     sm
 }
 
+impl SourceMap {
+    /// Returns `Some(span)`, a union of the LHS and RHS span. The LHS must precede the RHS. If
+    /// there are gaps between LHS and RHS, the resulting union will cross these gaps.
+    /// For this to work,
+    ///
+    ///    * the syntax contexts of both spans much match,
+    ///    * the LHS span needs to end on the same line the RHS span begins,
+    ///    * the LHS span must start at or before the RHS span.
+    fn merge_spans(&self, sp_lhs: Span, sp_rhs: Span) -> Option<Span> {
+        // Ensure we're at the same expansion ID.
+        if sp_lhs.ctxt() != sp_rhs.ctxt() {
+            return None;
+        }
+
+        let lhs_end = match self.lookup_line(sp_lhs.hi()) {
+            Ok(x) => x,
+            Err(_) => return None,
+        };
+        let rhs_begin = match self.lookup_line(sp_rhs.lo()) {
+            Ok(x) => x,
+            Err(_) => return None,
+        };
+
+        // If we must cross lines to merge, don't merge.
+        if lhs_end.line != rhs_begin.line {
+            return None;
+        }
+
+        // Ensure these follow the expected order and that we don't overlap.
+        if (sp_lhs.lo() <= sp_rhs.lo()) && (sp_lhs.hi() <= sp_rhs.lo()) {
+            Some(sp_lhs.to(sp_rhs))
+        } else {
+            None
+        }
+    }
+
+    /// Converts an absolute `BytePos` to a `CharPos` relative to the `SourceFile`.
+    fn bytepos_to_file_charpos(&self, bpos: BytePos) -> CharPos {
+        let idx = self.lookup_source_file_idx(bpos);
+        let sf = &(*self.files.borrow().source_files)[idx];
+        sf.bytepos_to_file_charpos(bpos)
+    }
+}
+
 /// Tests `lookup_byte_offset`.
 #[test]
 fn t3() {
diff --git a/library/core/src/iter/traits/iterator.rs b/library/core/src/iter/traits/iterator.rs
index f8504e842ee..a07750f4ad1 100644
--- a/library/core/src/iter/traits/iterator.rs
+++ b/library/core/src/iter/traits/iterator.rs
@@ -1012,7 +1012,7 @@ pub trait Iterator {
     ///
     /// Because the closure passed to `skip_while()` takes a reference, and many
     /// iterators iterate over references, this leads to a possibly confusing
-    /// situation, where the type of the closure is a double reference:
+    /// situation, where the type of the closure argument is a double reference:
     ///
     /// ```
     /// let a = [-1, 0, 1];
diff --git a/library/std/src/io/mod.rs b/library/std/src/io/mod.rs
index 17002e3b860..6abb300054a 100644
--- a/library/std/src/io/mod.rs
+++ b/library/std/src/io/mod.rs
@@ -514,8 +514,8 @@ pub trait Read {
     /// waiting for data, but if an object needs to block for a read and cannot,
     /// it will typically signal this via an [`Err`] return value.
     ///
-    /// If the return value of this method is [`Ok(n)`], then it must be
-    /// guaranteed that `0 <= n <= buf.len()`. A nonzero `n` value indicates
+    /// If the return value of this method is [`Ok(n)`], then implementations must
+    /// guarantee that `0 <= n <= buf.len()`. A nonzero `n` value indicates
     /// that the buffer `buf` has been filled in with `n` bytes of data from this
     /// source. If `n` is `0`, then it can indicate one of two scenarios:
     ///
@@ -529,6 +529,11 @@ pub trait Read {
     /// This may happen for example because fewer bytes are actually available right now
     /// (e. g. being close to end-of-file) or because read() was interrupted by a signal.
     ///
+    /// As this trait is safe to implement, callers cannot rely on `n <= buf.len()` for safety.
+    /// Extra care needs to be taken when `unsafe` functions are used to access the read bytes.
+    /// Callers have to ensure that no unchecked out-of-bounds accesses are possible even if
+    /// `n > buf.len()`.
+    ///
     /// No guarantees are provided about the contents of `buf` when this
     /// function is called, implementations cannot rely on any property of the
     /// contents of `buf` being true. It is recommended that *implementations*
diff --git a/library/std/src/os/haiku/raw.rs b/library/std/src/os/haiku/raw.rs
index 0d7e70b6b35..48117d288ae 100644
--- a/library/std/src/os/haiku/raw.rs
+++ b/library/std/src/os/haiku/raw.rs
@@ -1,6 +1,13 @@
 //! Haiku-specific raw type definitions
 
 #![stable(feature = "raw_ext", since = "1.1.0")]
+#![rustc_deprecated(
+    since = "1.53.0",
+    reason = "these type aliases are no longer supported by \
+              the standard library, the `libc` crate on \
+              crates.io should be used instead for the correct \
+              definitions"
+)]
 #![allow(deprecated)]
 
 use crate::os::raw::c_long;
diff --git a/library/std/src/sys/hermit/mod.rs b/library/std/src/sys/hermit/mod.rs
index f185635b7a0..17a51abeb0e 100644
--- a/library/std/src/sys/hermit/mod.rs
+++ b/library/std/src/sys/hermit/mod.rs
@@ -32,6 +32,7 @@ pub mod mutex;
 pub mod net;
 pub mod os;
 pub mod path;
+#[path = "../unsupported/pipe.rs"]
 pub mod pipe;
 #[path = "../unsupported/process.rs"]
 pub mod process;
diff --git a/library/std/src/sys/hermit/pipe.rs b/library/std/src/sys/hermit/pipe.rs
deleted file mode 100644
index 10d0925823e..00000000000
--- a/library/std/src/sys/hermit/pipe.rs
+++ /dev/null
@@ -1,38 +0,0 @@
-use crate::io::{self, IoSlice, IoSliceMut};
-use crate::sys::Void;
-
-pub struct AnonPipe(Void);
-
-impl AnonPipe {
-    pub fn read(&self, _buf: &mut [u8]) -> io::Result<usize> {
-        match self.0 {}
-    }
-
-    pub fn read_vectored(&self, _bufs: &mut [IoSliceMut<'_>]) -> io::Result<usize> {
-        match self.0 {}
-    }
-
-    pub fn is_read_vectored(&self) -> bool {
-        match self.0 {}
-    }
-
-    pub fn write(&self, _buf: &[u8]) -> io::Result<usize> {
-        match self.0 {}
-    }
-
-    pub fn write_vectored(&self, _bufs: &[IoSlice<'_>]) -> io::Result<usize> {
-        match self.0 {}
-    }
-
-    pub fn is_write_vectored(&self) -> bool {
-        match self.0 {}
-    }
-
-    pub fn diverge(&self) -> ! {
-        match self.0 {}
-    }
-}
-
-pub fn read2(p1: AnonPipe, _v1: &mut Vec<u8>, _p2: AnonPipe, _v2: &mut Vec<u8>) -> io::Result<()> {
-    match p1.0 {}
-}
diff --git a/src/doc/rustdoc/src/advanced-features.md b/src/doc/rustdoc/src/advanced-features.md
index abdc2e4025d..6147bd0a97a 100644
--- a/src/doc/rustdoc/src/advanced-features.md
+++ b/src/doc/rustdoc/src/advanced-features.md
@@ -81,3 +81,10 @@ Then, when looking for it through the `rustdoc` search, if you enter "x" or
 "big", search will show the `BigX` struct first.
 
 There are some limitations on the doc alias names though: you can't use `"` or whitespace.
+
+You can add multiple aliases at the same time by using a list:
+
+```rust,no_run
+#[doc(alias("x", "big"))]
+pub struct BigX;
+```
diff --git a/src/librustdoc/clean/types.rs b/src/librustdoc/clean/types.rs
index 114b68c56b8..840a42c2b8a 100644
--- a/src/librustdoc/clean/types.rs
+++ b/src/librustdoc/clean/types.rs
@@ -910,12 +910,23 @@ impl Attributes {
     }
 
     crate fn get_doc_aliases(&self) -> FxHashSet<String> {
-        self.other_attrs
-            .lists(sym::doc)
-            .filter(|a| a.has_name(sym::alias))
-            .filter_map(|a| a.value_str().map(|s| s.to_string()))
-            .filter(|v| !v.is_empty())
-            .collect::<FxHashSet<_>>()
+        let mut aliases = FxHashSet::default();
+
+        for attr in self.other_attrs.lists(sym::doc).filter(|a| a.has_name(sym::alias)) {
+            if let Some(values) = attr.meta_item_list() {
+                for l in values {
+                    match l.literal().unwrap().kind {
+                        ast::LitKind::Str(s, _) => {
+                            aliases.insert(s.as_str().to_string());
+                        }
+                        _ => unreachable!(),
+                    }
+                }
+            } else {
+                aliases.insert(attr.value_str().map(|s| s.to_string()).unwrap());
+            }
+        }
+        aliases
     }
 }
 
diff --git a/src/test/rustdoc-ui/check-doc-alias-attr.rs b/src/test/rustdoc-ui/check-doc-alias-attr.rs
index 912e35f9165..719b98604c4 100644
--- a/src/test/rustdoc-ui/check-doc-alias-attr.rs
+++ b/src/test/rustdoc-ui/check-doc-alias-attr.rs
@@ -1,11 +1,11 @@
 #![crate_type = "lib"]
 
 #[doc(alias = "foo")] // ok!
+#[doc(alias("bar", "baz"))] // ok!
 pub struct Bar;
 
 #[doc(alias)] //~ ERROR
 #[doc(alias = 0)] //~ ERROR
-#[doc(alias("bar"))] //~ ERROR
 #[doc(alias = "\"")] //~ ERROR
 #[doc(alias = "\n")] //~ ERROR
 #[doc(alias = "
@@ -13,4 +13,16 @@ pub struct Bar;
 #[doc(alias = "\t")] //~ ERROR
 #[doc(alias = " hello")] //~ ERROR
 #[doc(alias = "hello ")] //~ ERROR
+#[doc(alias = "")] //~ ERROR
 pub struct Foo;
+
+#[doc(alias(0))] //~ ERROR
+#[doc(alias("\""))] //~ ERROR
+#[doc(alias("\n"))] //~ ERROR
+#[doc(alias("
+"))] //~^ ERROR
+#[doc(alias("\t"))] //~ ERROR
+#[doc(alias(" hello"))] //~ ERROR
+#[doc(alias("hello "))] //~ ERROR
+#[doc(alias(""))] //~ ERROR
+pub struct Foo2;
diff --git a/src/test/rustdoc-ui/check-doc-alias-attr.stderr b/src/test/rustdoc-ui/check-doc-alias-attr.stderr
index 1c7fc83bb8d..f99d69dc101 100644
--- a/src/test/rustdoc-ui/check-doc-alias-attr.stderr
+++ b/src/test/rustdoc-ui/check-doc-alias-attr.stderr
@@ -1,21 +1,15 @@
-error: doc alias attribute expects a string: #[doc(alias = "a")]
-  --> $DIR/check-doc-alias-attr.rs:6:7
+error: doc alias attribute expects a string `#[doc(alias = "a")]` or a list of strings `#[doc(alias("a", "b"))]`
+  --> $DIR/check-doc-alias-attr.rs:7:7
    |
 LL | #[doc(alias)]
    |       ^^^^^
 
-error: doc alias attribute expects a string: #[doc(alias = "a")]
-  --> $DIR/check-doc-alias-attr.rs:7:7
+error: doc alias attribute expects a string `#[doc(alias = "a")]` or a list of strings `#[doc(alias("a", "b"))]`
+  --> $DIR/check-doc-alias-attr.rs:8:7
    |
 LL | #[doc(alias = 0)]
    |       ^^^^^^^^^
 
-error: doc alias attribute expects a string: #[doc(alias = "a")]
-  --> $DIR/check-doc-alias-attr.rs:8:7
-   |
-LL | #[doc(alias("bar"))]
-   |       ^^^^^^^^^^^^
-
 error: '\"' character isn't allowed in `#[doc(alias = "...")]`
   --> $DIR/check-doc-alias-attr.rs:9:15
    |
@@ -54,5 +48,61 @@ error: `#[doc(alias = "...")]` cannot start or end with ' '
 LL | #[doc(alias = "hello ")]
    |               ^^^^^^^^
 
-error: aborting due to 9 previous errors
+error: `#[doc(alias = "...")]` attribute cannot have empty value
+  --> $DIR/check-doc-alias-attr.rs:16:15
+   |
+LL | #[doc(alias = "")]
+   |               ^^
+
+error: `#[doc(alias("a"))]` expects string literals
+  --> $DIR/check-doc-alias-attr.rs:19:13
+   |
+LL | #[doc(alias(0))]
+   |             ^
+
+error: '\"' character isn't allowed in `#[doc(alias("..."))]`
+  --> $DIR/check-doc-alias-attr.rs:20:13
+   |
+LL | #[doc(alias("\""))]
+   |             ^^^^
+
+error: '\n' character isn't allowed in `#[doc(alias("..."))]`
+  --> $DIR/check-doc-alias-attr.rs:21:13
+   |
+LL | #[doc(alias("\n"))]
+   |             ^^^^
+
+error: '\n' character isn't allowed in `#[doc(alias("..."))]`
+  --> $DIR/check-doc-alias-attr.rs:22:13
+   |
+LL |   #[doc(alias("
+   |  _____________^
+LL | | "))]
+   | |_^
+
+error: '\t' character isn't allowed in `#[doc(alias("..."))]`
+  --> $DIR/check-doc-alias-attr.rs:24:13
+   |
+LL | #[doc(alias("\t"))]
+   |             ^^^^
+
+error: `#[doc(alias("..."))]` cannot start or end with ' '
+  --> $DIR/check-doc-alias-attr.rs:25:13
+   |
+LL | #[doc(alias(" hello"))]
+   |             ^^^^^^^^
+
+error: `#[doc(alias("..."))]` cannot start or end with ' '
+  --> $DIR/check-doc-alias-attr.rs:26:13
+   |
+LL | #[doc(alias("hello "))]
+   |             ^^^^^^^^
+
+error: `#[doc(alias("..."))]` attribute cannot have empty value
+  --> $DIR/check-doc-alias-attr.rs:27:13
+   |
+LL | #[doc(alias(""))]
+   |             ^^
+
+error: aborting due to 17 previous errors
 
diff --git a/src/test/ui/proc-macro/group-compat-hack/auxiliary/group-compat-hack.rs b/src/test/ui/proc-macro/group-compat-hack/auxiliary/pin-project-internal-0.4.0.rs
index 5cd3b40a2e4..baa4fd3a105 100644
--- a/src/test/ui/proc-macro/group-compat-hack/auxiliary/group-compat-hack.rs
+++ b/src/test/ui/proc-macro/group-compat-hack/auxiliary/pin-project-internal-0.4.0.rs
@@ -2,6 +2,10 @@
 // no-prefer-dynamic
 
 #![crate_type = "proc-macro"]
+#![crate_name = "group_compat_hack"]
+
+// This file has an unusual name in order to trigger the back-compat
+// code in the compiler
 
 extern crate proc_macro;
 use proc_macro::TokenStream;
diff --git a/src/test/ui/proc-macro/group-compat-hack/group-compat-hack.rs b/src/test/ui/proc-macro/group-compat-hack/group-compat-hack.rs
index 7f3f5e36f50..d9687490cad 100644
--- a/src/test/ui/proc-macro/group-compat-hack/group-compat-hack.rs
+++ b/src/test/ui/proc-macro/group-compat-hack/group-compat-hack.rs
@@ -1,5 +1,5 @@
 // check-pass
-// aux-build:group-compat-hack.rs
+// aux-build:pin-project-internal-0.4.0.rs
 // compile-flags: -Z span-debug
 
 #![no_std] // Don't load unnecessary hygiene information from std
@@ -51,14 +51,16 @@ mod actix_web_test {
     include!("actix-web/src/extract.rs");
 
     struct Foo;
-    tuple_from_req!(Foo);
+    tuple_from_req!(Foo); //~ WARN using an old version
+    //~| WARN this was previously
 }
 
 mod actix_web_version_test {
     include!("actix-web-2.0.0/src/extract.rs");
 
     struct Foo;
-    tuple_from_req!(Foo);
+    tuple_from_req!(Foo); //~ WARN using an old version
+    //~| WARN this was previously
 }
 
 mod actori_web_test {
diff --git a/src/test/ui/proc-macro/group-compat-hack/group-compat-hack.stderr b/src/test/ui/proc-macro/group-compat-hack/group-compat-hack.stderr
index 9370440a635..e2b680f8d27 100644
--- a/src/test/ui/proc-macro/group-compat-hack/group-compat-hack.stderr
+++ b/src/test/ui/proc-macro/group-compat-hack/group-compat-hack.stderr
@@ -31,7 +31,39 @@ LL |     impl_macros!(Foo);
    = note: the `time-macros-impl` crate will stop compiling in futures version of Rust. Please update to the latest version of the `time` crate to avoid breakage
    = note: this warning originates in a macro (in Nightly builds, run with -Z macro-backtrace for more info)
 
-warning: 2 warnings emitted
+warning: using an old version of `actix-web`
+  --> $DIR/actix-web/src/extract.rs:5:34
+   |
+LL |         #[my_macro] struct Three($T);
+   |                                  ^^
+   | 
+  ::: $DIR/group-compat-hack.rs:54:5
+   |
+LL |     tuple_from_req!(Foo);
+   |     --------------------- in this macro invocation
+   |
+   = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
+   = note: for more information, see issue #83125 <https://github.com/rust-lang/rust/issues/83125>
+   = note: the version of `actix-web` you are using might stop compiling in future versions of Rust; please update to the latest version of the `actix-web` crate to avoid breakage
+   = note: this warning originates in a macro (in Nightly builds, run with -Z macro-backtrace for more info)
+
+warning: using an old version of `actix-web`
+  --> $DIR/actix-web-2.0.0/src/extract.rs:5:34
+   |
+LL |         #[my_macro] struct Three($T);
+   |                                  ^^
+   | 
+  ::: $DIR/group-compat-hack.rs:62:5
+   |
+LL |     tuple_from_req!(Foo);
+   |     --------------------- in this macro invocation
+   |
+   = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
+   = note: for more information, see issue #83125 <https://github.com/rust-lang/rust/issues/83125>
+   = note: the version of `actix-web` you are using might stop compiling in future versions of Rust; please update to the latest version of the `actix-web` crate to avoid breakage
+   = note: this warning originates in a macro (in Nightly builds, run with -Z macro-backtrace for more info)
+
+warning: 4 warnings emitted
 
 Future incompatibility report: Future breakage date: None, diagnostic:
 warning: using an old version of `time-macros-impl`
@@ -68,3 +100,37 @@ LL |     impl_macros!(Foo);
    = note: the `time-macros-impl` crate will stop compiling in futures version of Rust. Please update to the latest version of the `time` crate to avoid breakage
    = note: this warning originates in a macro (in Nightly builds, run with -Z macro-backtrace for more info)
 
+Future breakage date: None, diagnostic:
+warning: using an old version of `actix-web`
+  --> $DIR/actix-web/src/extract.rs:5:34
+   |
+LL |         #[my_macro] struct Three($T);
+   |                                  ^^
+   | 
+  ::: $DIR/group-compat-hack.rs:54:5
+   |
+LL |     tuple_from_req!(Foo);
+   |     --------------------- in this macro invocation
+   |
+   = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
+   = note: for more information, see issue #83125 <https://github.com/rust-lang/rust/issues/83125>
+   = note: the version of `actix-web` you are using might stop compiling in future versions of Rust; please update to the latest version of the `actix-web` crate to avoid breakage
+   = note: this warning originates in a macro (in Nightly builds, run with -Z macro-backtrace for more info)
+
+Future breakage date: None, diagnostic:
+warning: using an old version of `actix-web`
+  --> $DIR/actix-web-2.0.0/src/extract.rs:5:34
+   |
+LL |         #[my_macro] struct Three($T);
+   |                                  ^^
+   | 
+  ::: $DIR/group-compat-hack.rs:62:5
+   |
+LL |     tuple_from_req!(Foo);
+   |     --------------------- in this macro invocation
+   |
+   = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
+   = note: for more information, see issue #83125 <https://github.com/rust-lang/rust/issues/83125>
+   = note: the version of `actix-web` you are using might stop compiling in future versions of Rust; please update to the latest version of the `actix-web` crate to avoid breakage
+   = note: this warning originates in a macro (in Nightly builds, run with -Z macro-backtrace for more info)
+
diff --git a/src/test/ui/proc-macro/group-compat-hack/group-compat-hack.stdout b/src/test/ui/proc-macro/group-compat-hack/group-compat-hack.stdout
index 468cb511915..3fe744e12ff 100644
--- a/src/test/ui/proc-macro/group-compat-hack/group-compat-hack.stdout
+++ b/src/test/ui/proc-macro/group-compat-hack/group-compat-hack.stdout
@@ -5,6 +5,6 @@ Called proc_macro_hack with TokenStream [Ident { ident: "struct", span: $DIR/tim
 Called proc_macro_hack with TokenStream [Ident { ident: "struct", span: $DIR/js-sys-0.3.17/src/lib.rs:5:21: 5:27 (#24) }, Ident { ident: "Two", span: $DIR/js-sys-0.3.17/src/lib.rs:5:28: 5:31 (#24) }, Group { delimiter: Parenthesis, stream: TokenStream [Ident { ident: "Foo", span: $DIR/group-compat-hack.rs:46:13: 46:16 (#0) }], span: $DIR/js-sys-0.3.17/src/lib.rs:5:31: 5:38 (#24) }, Punct { ch: ';', spacing: Alone, span: $DIR/js-sys-0.3.17/src/lib.rs:5:38: 5:39 (#24) }]
 Called proc_macro_hack with TokenStream [Ident { ident: "struct", span: $DIR/group-compat-hack.rs:39:25: 39:31 (#28) }, Ident { ident: "Three", span: $DIR/group-compat-hack.rs:39:32: 39:37 (#28) }, Group { delimiter: Parenthesis, stream: TokenStream [Group { delimiter: None, stream: TokenStream [Ident { ident: "Foo", span: $DIR/group-compat-hack.rs:47:12: 47:15 (#0) }], span: $DIR/group-compat-hack.rs:39:38: 39:43 (#28) }], span: $DIR/group-compat-hack.rs:39:37: 39:44 (#28) }, Punct { ch: ';', spacing: Alone, span: $DIR/group-compat-hack.rs:39:44: 39:45 (#28) }]
 Called proc_macro_hack with TokenStream [Ident { ident: "struct", span: $DIR/actix-web/src/extract.rs:5:21: 5:27 (#33) }, Ident { ident: "Three", span: $DIR/actix-web/src/extract.rs:5:28: 5:33 (#33) }, Group { delimiter: Parenthesis, stream: TokenStream [Ident { ident: "Foo", span: $DIR/group-compat-hack.rs:54:21: 54:24 (#0) }], span: $DIR/actix-web/src/extract.rs:5:33: 5:37 (#33) }, Punct { ch: ';', spacing: Alone, span: $DIR/actix-web/src/extract.rs:5:37: 5:38 (#33) }]
-Called proc_macro_hack with TokenStream [Ident { ident: "struct", span: $DIR/actix-web-2.0.0/src/extract.rs:5:21: 5:27 (#38) }, Ident { ident: "Three", span: $DIR/actix-web-2.0.0/src/extract.rs:5:28: 5:33 (#38) }, Group { delimiter: Parenthesis, stream: TokenStream [Ident { ident: "Foo", span: $DIR/group-compat-hack.rs:61:21: 61:24 (#0) }], span: $DIR/actix-web-2.0.0/src/extract.rs:5:33: 5:37 (#38) }, Punct { ch: ';', spacing: Alone, span: $DIR/actix-web-2.0.0/src/extract.rs:5:37: 5:38 (#38) }]
-Called proc_macro_hack with TokenStream [Ident { ident: "struct", span: $DIR/actori-web/src/extract.rs:5:21: 5:27 (#43) }, Ident { ident: "Four", span: $DIR/actori-web/src/extract.rs:5:28: 5:32 (#43) }, Group { delimiter: Parenthesis, stream: TokenStream [Ident { ident: "Foo", span: $DIR/group-compat-hack.rs:68:21: 68:24 (#0) }], span: $DIR/actori-web/src/extract.rs:5:32: 5:36 (#43) }, Punct { ch: ';', spacing: Alone, span: $DIR/actori-web/src/extract.rs:5:36: 5:37 (#43) }]
-Called proc_macro_hack with TokenStream [Ident { ident: "struct", span: $DIR/actori-web-2.0.0/src/extract.rs:5:21: 5:27 (#48) }, Ident { ident: "Four", span: $DIR/actori-web-2.0.0/src/extract.rs:5:28: 5:32 (#48) }, Group { delimiter: Parenthesis, stream: TokenStream [Ident { ident: "Foo", span: $DIR/group-compat-hack.rs:75:21: 75:24 (#0) }], span: $DIR/actori-web-2.0.0/src/extract.rs:5:32: 5:36 (#48) }, Punct { ch: ';', spacing: Alone, span: $DIR/actori-web-2.0.0/src/extract.rs:5:36: 5:37 (#48) }]
+Called proc_macro_hack with TokenStream [Ident { ident: "struct", span: $DIR/actix-web-2.0.0/src/extract.rs:5:21: 5:27 (#38) }, Ident { ident: "Three", span: $DIR/actix-web-2.0.0/src/extract.rs:5:28: 5:33 (#38) }, Group { delimiter: Parenthesis, stream: TokenStream [Ident { ident: "Foo", span: $DIR/group-compat-hack.rs:62:21: 62:24 (#0) }], span: $DIR/actix-web-2.0.0/src/extract.rs:5:33: 5:37 (#38) }, Punct { ch: ';', spacing: Alone, span: $DIR/actix-web-2.0.0/src/extract.rs:5:37: 5:38 (#38) }]
+Called proc_macro_hack with TokenStream [Ident { ident: "struct", span: $DIR/actori-web/src/extract.rs:5:21: 5:27 (#43) }, Ident { ident: "Four", span: $DIR/actori-web/src/extract.rs:5:28: 5:32 (#43) }, Group { delimiter: Parenthesis, stream: TokenStream [Group { delimiter: None, stream: TokenStream [Ident { ident: "Foo", span: $DIR/group-compat-hack.rs:70:21: 70:24 (#0) }], span: $DIR/actori-web/src/extract.rs:5:33: 5:35 (#43) }], span: $DIR/actori-web/src/extract.rs:5:32: 5:36 (#43) }, Punct { ch: ';', spacing: Alone, span: $DIR/actori-web/src/extract.rs:5:36: 5:37 (#43) }]
+Called proc_macro_hack with TokenStream [Ident { ident: "struct", span: $DIR/actori-web-2.0.0/src/extract.rs:5:21: 5:27 (#48) }, Ident { ident: "Four", span: $DIR/actori-web-2.0.0/src/extract.rs:5:28: 5:32 (#48) }, Group { delimiter: Parenthesis, stream: TokenStream [Group { delimiter: None, stream: TokenStream [Ident { ident: "Foo", span: $DIR/group-compat-hack.rs:77:21: 77:24 (#0) }], span: $DIR/actori-web-2.0.0/src/extract.rs:5:33: 5:35 (#48) }], span: $DIR/actori-web-2.0.0/src/extract.rs:5:32: 5:36 (#48) }, Punct { ch: ';', spacing: Alone, span: $DIR/actori-web-2.0.0/src/extract.rs:5:36: 5:37 (#48) }]
diff --git a/src/test/ui/rustdoc/check-doc-alias-attr.rs b/src/test/ui/rustdoc/check-doc-alias-attr.rs
index 912e35f9165..719b98604c4 100644
--- a/src/test/ui/rustdoc/check-doc-alias-attr.rs
+++ b/src/test/ui/rustdoc/check-doc-alias-attr.rs
@@ -1,11 +1,11 @@
 #![crate_type = "lib"]
 
 #[doc(alias = "foo")] // ok!
+#[doc(alias("bar", "baz"))] // ok!
 pub struct Bar;
 
 #[doc(alias)] //~ ERROR
 #[doc(alias = 0)] //~ ERROR
-#[doc(alias("bar"))] //~ ERROR
 #[doc(alias = "\"")] //~ ERROR
 #[doc(alias = "\n")] //~ ERROR
 #[doc(alias = "
@@ -13,4 +13,16 @@ pub struct Bar;
 #[doc(alias = "\t")] //~ ERROR
 #[doc(alias = " hello")] //~ ERROR
 #[doc(alias = "hello ")] //~ ERROR
+#[doc(alias = "")] //~ ERROR
 pub struct Foo;
+
+#[doc(alias(0))] //~ ERROR
+#[doc(alias("\""))] //~ ERROR
+#[doc(alias("\n"))] //~ ERROR
+#[doc(alias("
+"))] //~^ ERROR
+#[doc(alias("\t"))] //~ ERROR
+#[doc(alias(" hello"))] //~ ERROR
+#[doc(alias("hello "))] //~ ERROR
+#[doc(alias(""))] //~ ERROR
+pub struct Foo2;
diff --git a/src/test/ui/rustdoc/check-doc-alias-attr.stderr b/src/test/ui/rustdoc/check-doc-alias-attr.stderr
index 1c7fc83bb8d..f99d69dc101 100644
--- a/src/test/ui/rustdoc/check-doc-alias-attr.stderr
+++ b/src/test/ui/rustdoc/check-doc-alias-attr.stderr
@@ -1,21 +1,15 @@
-error: doc alias attribute expects a string: #[doc(alias = "a")]
-  --> $DIR/check-doc-alias-attr.rs:6:7
+error: doc alias attribute expects a string `#[doc(alias = "a")]` or a list of strings `#[doc(alias("a", "b"))]`
+  --> $DIR/check-doc-alias-attr.rs:7:7
    |
 LL | #[doc(alias)]
    |       ^^^^^
 
-error: doc alias attribute expects a string: #[doc(alias = "a")]
-  --> $DIR/check-doc-alias-attr.rs:7:7
+error: doc alias attribute expects a string `#[doc(alias = "a")]` or a list of strings `#[doc(alias("a", "b"))]`
+  --> $DIR/check-doc-alias-attr.rs:8:7
    |
 LL | #[doc(alias = 0)]
    |       ^^^^^^^^^
 
-error: doc alias attribute expects a string: #[doc(alias = "a")]
-  --> $DIR/check-doc-alias-attr.rs:8:7
-   |
-LL | #[doc(alias("bar"))]
-   |       ^^^^^^^^^^^^
-
 error: '\"' character isn't allowed in `#[doc(alias = "...")]`
   --> $DIR/check-doc-alias-attr.rs:9:15
    |
@@ -54,5 +48,61 @@ error: `#[doc(alias = "...")]` cannot start or end with ' '
 LL | #[doc(alias = "hello ")]
    |               ^^^^^^^^
 
-error: aborting due to 9 previous errors
+error: `#[doc(alias = "...")]` attribute cannot have empty value
+  --> $DIR/check-doc-alias-attr.rs:16:15
+   |
+LL | #[doc(alias = "")]
+   |               ^^
+
+error: `#[doc(alias("a"))]` expects string literals
+  --> $DIR/check-doc-alias-attr.rs:19:13
+   |
+LL | #[doc(alias(0))]
+   |             ^
+
+error: '\"' character isn't allowed in `#[doc(alias("..."))]`
+  --> $DIR/check-doc-alias-attr.rs:20:13
+   |
+LL | #[doc(alias("\""))]
+   |             ^^^^
+
+error: '\n' character isn't allowed in `#[doc(alias("..."))]`
+  --> $DIR/check-doc-alias-attr.rs:21:13
+   |
+LL | #[doc(alias("\n"))]
+   |             ^^^^
+
+error: '\n' character isn't allowed in `#[doc(alias("..."))]`
+  --> $DIR/check-doc-alias-attr.rs:22:13
+   |
+LL |   #[doc(alias("
+   |  _____________^
+LL | | "))]
+   | |_^
+
+error: '\t' character isn't allowed in `#[doc(alias("..."))]`
+  --> $DIR/check-doc-alias-attr.rs:24:13
+   |
+LL | #[doc(alias("\t"))]
+   |             ^^^^
+
+error: `#[doc(alias("..."))]` cannot start or end with ' '
+  --> $DIR/check-doc-alias-attr.rs:25:13
+   |
+LL | #[doc(alias(" hello"))]
+   |             ^^^^^^^^
+
+error: `#[doc(alias("..."))]` cannot start or end with ' '
+  --> $DIR/check-doc-alias-attr.rs:26:13
+   |
+LL | #[doc(alias("hello "))]
+   |             ^^^^^^^^
+
+error: `#[doc(alias("..."))]` attribute cannot have empty value
+  --> $DIR/check-doc-alias-attr.rs:27:13
+   |
+LL | #[doc(alias(""))]
+   |             ^^
+
+error: aborting due to 17 previous errors
 
diff --git a/src/tools/tidy/src/deps.rs b/src/tools/tidy/src/deps.rs
index 06dc16f7676..96a02038638 100644
--- a/src/tools/tidy/src/deps.rs
+++ b/src/tools/tidy/src/deps.rs
@@ -123,6 +123,7 @@ const PERMITTED_DEPENDENCIES: &[&str] = &[
     "measureme",
     "memchr",
     "memmap",
+    "memmap2",
     "memoffset",
     "miniz_oxide",
     "num_cpus",