diff --git a/.gitattributes b/.gitattributes
index 4038db6f7dab1..d29c15fe712f3 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/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 99a0c0b4b85de..2ead68638fa4a 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -622,7 +622,7 @@ jobs:
     if: "github.event_name == 'push' && github.ref == 'refs/heads/master' && github.repository == 'rust-lang-ci/rust'"
     steps:
       - name: checkout the source code
-        uses: actions/checkout@v1
+        uses: actions/checkout@v2
         with:
           fetch-depth: 2
       - name: publish toolstate
diff --git a/Cargo.lock b/Cargo.lock
index fd6fffe980bc5..e5a7b7d9b6056 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -2164,6 +2164,15 @@ dependencies = [
  "winapi 0.3.9",
 ]
 
+[[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"
@@ -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_codegen_ssa/Cargo.toml b/compiler/rustc_codegen_ssa/Cargo.toml
index 5e2f01b2c9da8..15dbbbd49aa56 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 0d7f4447696f2..c6aea22a63eb7 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 854aaac757fb0..490b3d3311284 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_errors/src/diagnostic_builder.rs b/compiler/rustc_errors/src/diagnostic_builder.rs
index c09cce21bf24c..79507e6152219 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 1db39fbfba502..fa855f544e819 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_metadata/Cargo.toml b/compiler/rustc_metadata/Cargo.toml
index 2aabc2c407b1a..48effed927493 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 a9f58b08f5899..39a39917f578c 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/library/core/src/iter/traits/iterator.rs b/library/core/src/iter/traits/iterator.rs
index f8504e842ee33..a07750f4ad1fe 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/collections/mod.rs b/library/std/src/collections/mod.rs
index 7f8f9c991fe40..8cda601edd141 100644
--- a/library/std/src/collections/mod.rs
+++ b/library/std/src/collections/mod.rs
@@ -401,9 +401,10 @@
 #![stable(feature = "rust1", since = "1.0.0")]
 
 #[stable(feature = "rust1", since = "1.0.0")]
-#[rustc_deprecated(reason = "moved to `std::ops::Bound`", since = "1.52.0")]
+// FIXME(#82080) The deprecation here is only theoretical, and does not actually produce a warning.
+#[rustc_deprecated(reason = "moved to `std::ops::Bound`", since = "1.26.0")]
 #[doc(hidden)]
-pub type Bound<T> = crate::ops::Bound<T>;
+pub use crate::ops::Bound;
 
 #[stable(feature = "rust1", since = "1.0.0")]
 pub use alloc_crate::collections::{binary_heap, btree_map, btree_set};
diff --git a/library/std/src/io/mod.rs b/library/std/src/io/mod.rs
index 17002e3b8602d..6abb300054af8 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 0d7e70b6b351d..48117d288ae47 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 f185635b7a0a6..17a51abeb0ef6 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 10d0925823eb9..0000000000000
--- 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/ci/github-actions/ci.yml b/src/ci/github-actions/ci.yml
index 7125b33699a0c..c0a84444a5928 100644
--- a/src/ci/github-actions/ci.yml
+++ b/src/ci/github-actions/ci.yml
@@ -655,7 +655,7 @@ jobs:
     if: github.event_name == 'push' && github.ref == 'refs/heads/master' && github.repository == 'rust-lang-ci/rust'
     steps:
       - name: checkout the source code
-        uses: actions/checkout@v1
+        uses: actions/checkout@v2
         with:
           fetch-depth: 2
 
diff --git a/src/tools/tidy/src/deps.rs b/src/tools/tidy/src/deps.rs
index 06dc16f767660..96a02038638af 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",