diff --git a/Cargo.lock b/Cargo.lock
index 16f2ffc28150f..7c074fb18a6f1 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -3120,7 +3120,6 @@ dependencies = [
  "graphviz",
  "jobserver",
  "log",
- "measureme",
  "num_cpus",
  "parking_lot 0.9.0",
  "polonius-engine",
@@ -3470,6 +3469,7 @@ dependencies = [
 name = "rustc_data_structures"
 version = "0.0.0"
 dependencies = [
+ "bitflags",
  "cfg-if",
  "crossbeam-utils 0.6.5",
  "ena",
@@ -3478,6 +3478,7 @@ dependencies = [
  "jobserver",
  "lazy_static 1.3.0",
  "log",
+ "measureme",
  "parking_lot 0.9.0",
  "rustc-hash",
  "rustc-rayon 0.3.0",
diff --git a/src/bootstrap/bin/rustdoc.rs b/src/bootstrap/bin/rustdoc.rs
index a13ff69a7b56f..6937fb922de48 100644
--- a/src/bootstrap/bin/rustdoc.rs
+++ b/src/bootstrap/bin/rustdoc.rs
@@ -25,7 +25,7 @@ fn main() {
     let mut dylib_path = bootstrap::util::dylib_path();
     dylib_path.insert(0, PathBuf::from(libdir.clone()));
 
-    //FIXME(misdreavus): once stdsimd uses cfg(rustdoc) instead of cfg(dox), remove the `--cfg dox`
+    //FIXME(misdreavus): once stdsimd uses cfg(doc) instead of cfg(dox), remove the `--cfg dox`
     //arguments here
     let mut cmd = Command::new(rustdoc);
     cmd.args(&args)
diff --git a/src/bootstrap/bootstrap.py b/src/bootstrap/bootstrap.py
index 4caf36a6f2a51..730e8cf05d41d 100644
--- a/src/bootstrap/bootstrap.py
+++ b/src/bootstrap/bootstrap.py
@@ -102,10 +102,10 @@ def verify(path, sha_path, verbose):
     return verified
 
 
-def unpack(tarball, dst, verbose=False, match=None):
+def unpack(tarball, tarball_suffix, dst, verbose=False, match=None):
     """Unpack the given tarball file"""
     print("extracting", tarball)
-    fname = os.path.basename(tarball).replace(".tar.gz", "")
+    fname = os.path.basename(tarball).replace(tarball_suffix, "")
     with contextlib.closing(tarfile.open(tarball)) as tar:
         for member in tar.getnames():
             if "/" not in member:
@@ -331,6 +331,7 @@ def __init__(self):
         self.use_vendored_sources = ''
         self.verbose = False
 
+
     def download_stage0(self):
         """Fetch the build system for Rust, written in Rust
 
@@ -344,18 +345,30 @@ def download_stage0(self):
         rustc_channel = self.rustc_channel
         cargo_channel = self.cargo_channel
 
+        def support_xz():
+            try:
+                with tempfile.NamedTemporaryFile(delete=False) as temp_file:
+                    temp_path = temp_file.name
+                with tarfile.open(temp_path, "w:xz") as tar:
+                    pass
+                return True
+            except tarfile.CompressionError:
+                return False
+
         if self.rustc().startswith(self.bin_root()) and \
                 (not os.path.exists(self.rustc()) or
                  self.program_out_of_date(self.rustc_stamp())):
             if os.path.exists(self.bin_root()):
                 shutil.rmtree(self.bin_root())
-            filename = "rust-std-{}-{}.tar.gz".format(
-                rustc_channel, self.build)
+            tarball_suffix = '.tar.xz' if support_xz() else '.tar.gz'
+            filename = "rust-std-{}-{}{}".format(
+                rustc_channel, self.build, tarball_suffix)
             pattern = "rust-std-{}".format(self.build)
-            self._download_stage0_helper(filename, pattern)
+            self._download_stage0_helper(filename, pattern, tarball_suffix)
 
-            filename = "rustc-{}-{}.tar.gz".format(rustc_channel, self.build)
-            self._download_stage0_helper(filename, "rustc")
+            filename = "rustc-{}-{}{}".format(rustc_channel, self.build,
+                                              tarball_suffix)
+            self._download_stage0_helper(filename, "rustc", tarball_suffix)
             self.fix_executable("{}/bin/rustc".format(self.bin_root()))
             self.fix_executable("{}/bin/rustdoc".format(self.bin_root()))
             with output(self.rustc_stamp()) as rust_stamp:
@@ -365,20 +378,22 @@ def download_stage0(self):
             # libraries/binaries that are included in rust-std with
             # the system MinGW ones.
             if "pc-windows-gnu" in self.build:
-                filename = "rust-mingw-{}-{}.tar.gz".format(
-                    rustc_channel, self.build)
-                self._download_stage0_helper(filename, "rust-mingw")
+                filename = "rust-mingw-{}-{}{}".format(
+                    rustc_channel, self.build, tarball_suffix)
+                self._download_stage0_helper(filename, "rust-mingw", tarball_suffix)
 
         if self.cargo().startswith(self.bin_root()) and \
                 (not os.path.exists(self.cargo()) or
                  self.program_out_of_date(self.cargo_stamp())):
-            filename = "cargo-{}-{}.tar.gz".format(cargo_channel, self.build)
-            self._download_stage0_helper(filename, "cargo")
+            tarball_suffix = '.tar.xz' if support_xz() else '.tar.gz'
+            filename = "cargo-{}-{}{}".format(cargo_channel, self.build,
+                                              tarball_suffix)
+            self._download_stage0_helper(filename, "cargo", tarball_suffix)
             self.fix_executable("{}/bin/cargo".format(self.bin_root()))
             with output(self.cargo_stamp()) as cargo_stamp:
                 cargo_stamp.write(self.date)
 
-    def _download_stage0_helper(self, filename, pattern):
+    def _download_stage0_helper(self, filename, pattern, tarball_suffix):
         cache_dst = os.path.join(self.build_dir, "cache")
         rustc_cache = os.path.join(cache_dst, self.date)
         if not os.path.exists(rustc_cache):
@@ -388,7 +403,7 @@ def _download_stage0_helper(self, filename, pattern):
         tarball = os.path.join(rustc_cache, filename)
         if not os.path.exists(tarball):
             get("{}/{}".format(url, filename), tarball, verbose=self.verbose)
-        unpack(tarball, self.bin_root(), match=pattern, verbose=self.verbose)
+        unpack(tarball, tarball_suffix, self.bin_root(), match=pattern, verbose=self.verbose)
 
     @staticmethod
     def fix_executable(fname):
diff --git a/src/bootstrap/builder.rs b/src/bootstrap/builder.rs
index 2edcef203ad26..99b8ddf7db1f0 100644
--- a/src/bootstrap/builder.rs
+++ b/src/bootstrap/builder.rs
@@ -1242,7 +1242,8 @@ impl<'a> Builder<'a> {
             cargo.arg("--frozen");
         }
 
-        cargo.env("RUSTC_INSTALL_BINDIR", &self.config.bindir);
+        // Try to use a sysroot-relative bindir, in case it was configured absolutely.
+        cargo.env("RUSTC_INSTALL_BINDIR", self.config.bindir_relative());
 
         self.ci_env.force_coloring_in_ci(&mut cargo);
 
diff --git a/src/bootstrap/config.rs b/src/bootstrap/config.rs
index d1bdfa0a76763..0c03b95c7b251 100644
--- a/src/bootstrap/config.rs
+++ b/src/bootstrap/config.rs
@@ -647,6 +647,20 @@ impl Config {
         config
     }
 
+    /// Try to find the relative path of `bindir`, otherwise return it in full.
+    pub fn bindir_relative(&self) -> &Path {
+        let bindir = &self.bindir;
+        if bindir.is_absolute() {
+            // Try to make it relative to the prefix.
+            if let Some(prefix) = &self.prefix {
+                if let Ok(stripped) = bindir.strip_prefix(prefix) {
+                    return stripped;
+                }
+            }
+        }
+        bindir
+    }
+
     /// Try to find the relative path of `libdir`.
     pub fn libdir_relative(&self) -> Option<&Path> {
         let libdir = self.libdir.as_ref()?;
diff --git a/src/doc/rustdoc/src/unstable-features.md b/src/doc/rustdoc/src/unstable-features.md
index 3c3e72aa37959..f8be04a1087bf 100644
--- a/src/doc/rustdoc/src/unstable-features.md
+++ b/src/doc/rustdoc/src/unstable-features.md
@@ -106,11 +106,11 @@ item, it will be accompanied by a banner explaining that the item is only availa
 platforms.
 
 For Rustdoc to document an item, it needs to see it, regardless of what platform it's currently
-running on. To aid this, Rustdoc sets the flag `#[cfg(rustdoc)]` when running on your crate.
+running on. To aid this, Rustdoc sets the flag `#[cfg(doc)]` when running on your crate.
 Combining this with the target platform of a given item allows it to appear when building your crate
 normally on that platform, as well as when building documentation anywhere.
 
-For example, `#[cfg(any(windows, rustdoc))]` will preserve the item either on Windows or during the
+For example, `#[cfg(any(windows, doc))]` will preserve the item either on Windows or during the
 documentation process. Then, adding a new attribute `#[doc(cfg(windows))]` will tell Rustdoc that
 the item is supposed to be used on Windows. For example:
 
@@ -118,12 +118,12 @@ the item is supposed to be used on Windows. For example:
 #![feature(doc_cfg)]
 
 /// Token struct that can only be used on Windows.
-#[cfg(any(windows, rustdoc))]
+#[cfg(any(windows, doc))]
 #[doc(cfg(windows))]
 pub struct WindowsToken;
 
 /// Token struct that can only be used on Unix.
-#[cfg(any(unix, rustdoc))]
+#[cfg(any(unix, doc))]
 #[doc(cfg(unix))]
 pub struct UnixToken;
 ```
diff --git a/src/doc/unstable-book/src/language-features/doc-cfg.md b/src/doc/unstable-book/src/language-features/doc-cfg.md
index 96c66a1515ed5..e75f1aea99229 100644
--- a/src/doc/unstable-book/src/language-features/doc-cfg.md
+++ b/src/doc/unstable-book/src/language-features/doc-cfg.md
@@ -13,7 +13,7 @@ This attribute has two effects:
 2. The item's doc-tests will only run on the specific platform.
 
 In addition to allowing the use of the `#[doc(cfg)]` attribute, this feature enables the use of a
-special conditional compilation flag, `#[cfg(rustdoc)]`, set whenever building documentation on your
+special conditional compilation flag, `#[cfg(doc)]`, set whenever building documentation on your
 crate.
 
 This feature was introduced as part of PR [#43348] to allow the platform-specific parts of the
@@ -22,7 +22,7 @@ standard library be documented.
 ```rust
 #![feature(doc_cfg)]
 
-#[cfg(any(windows, rustdoc))]
+#[cfg(any(windows, doc))]
 #[doc(cfg(windows))]
 /// The application's icon in the notification area (a.k.a. system tray).
 ///
diff --git a/src/libcore/cell.rs b/src/libcore/cell.rs
index 87d8e7aff058d..03f32e726187b 100644
--- a/src/libcore/cell.rs
+++ b/src/libcore/cell.rs
@@ -1545,9 +1545,46 @@ impl<T: ?Sized> UnsafeCell<T> {
     #[stable(feature = "rust1", since = "1.0.0")]
     pub const fn get(&self) -> *mut T {
         // We can just cast the pointer from `UnsafeCell<T>` to `T` because of
-        // #[repr(transparent)]
+        // #[repr(transparent)]. This exploits libstd's special status, there is
+        // no guarantee for user code that this will work in future versions of the compiler!
         self as *const UnsafeCell<T> as *const T as *mut T
     }
+
+    /// Gets a mutable pointer to the wrapped value.
+    /// The difference to [`get`] is that this function accepts a raw pointer,
+    /// which is useful to avoid the creation of temporary references.
+    ///
+    /// The result can be cast to a pointer of any kind.
+    /// Ensure that the access is unique (no active references, mutable or not)
+    /// when casting to `&mut T`, and ensure that there are no mutations
+    /// or mutable aliases going on when casting to `&T`.
+    ///
+    /// [`get`]: #method.get
+    ///
+    /// # Examples
+    ///
+    /// Gradual initialization of an `UnsafeCell` requires `raw_get`, as
+    /// calling `get` would require creating a reference to uninitialized data:
+    ///
+    /// ```
+    /// #![feature(unsafe_cell_raw_get)]
+    /// use std::cell::UnsafeCell;
+    /// use std::mem::MaybeUninit;
+    ///
+    /// let m = MaybeUninit::<UnsafeCell<i32>>::uninit();
+    /// unsafe { UnsafeCell::raw_get(m.as_ptr()).write(5); }
+    /// let uc = unsafe { m.assume_init() };
+    ///
+    /// assert_eq!(uc.into_inner(), 5);
+    /// ```
+    #[inline]
+    #[unstable(feature = "unsafe_cell_raw_get", issue = "66358")]
+    pub const fn raw_get(this: *const Self) -> *mut T {
+        // We can just cast the pointer from `UnsafeCell<T>` to `T` because of
+        // #[repr(transparent)]. This exploits libstd's special status, there is
+        // no guarantee for user code that this will work in future versions of the compiler!
+        this as *const T as *mut T
+    }
 }
 
 #[stable(feature = "unsafe_cell_default", since = "1.10.0")]
diff --git a/src/libcore/iter/traits/iterator.rs b/src/libcore/iter/traits/iterator.rs
index 7ffc8b3729cb4..b7a35568e3fc5 100644
--- a/src/libcore/iter/traits/iterator.rs
+++ b/src/libcore/iter/traits/iterator.rs
@@ -201,12 +201,13 @@ pub trait Iterator {
 
     /// Consumes the iterator, counting the number of iterations and returning it.
     ///
-    /// This method will evaluate the iterator until its [`next`] returns
-    /// [`None`]. Once [`None`] is encountered, `count()` returns the number of
-    /// times it called [`next`].
+    /// This method will call [`next`] repeatedly until [`None`] is encountered,
+    /// returning the number of times it saw [`Some`]. Note that [`next`] has to be
+    /// called at least once even if the iterator does not have any elements.
     ///
     /// [`next`]: #tymethod.next
     /// [`None`]: ../../std/option/enum.Option.html#variant.None
+    /// [`Some`]: ../../std/option/enum.Option.html#variant.Some
     ///
     /// # Overflow Behavior
     ///
diff --git a/src/libcore/result.rs b/src/libcore/result.rs
index ed40a5f31d9bd..06c7041703ae5 100644
--- a/src/libcore/result.rs
+++ b/src/libcore/result.rs
@@ -514,6 +514,28 @@ impl<T, E> Result<T, E> {
         }
     }
 
+    /// Applies a function to the contained value (if any),
+    /// or returns the provided default (if not).
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// #![feature(result_map_or)]
+    /// let x: Result<_, &str> = Ok("foo");
+    /// assert_eq!(x.map_or(42, |v| v.len()), 3);
+    ///
+    /// let x: Result<&str, _> = Err("bar");
+    /// assert_eq!(x.map_or(42, |v| v.len()), 42);
+    /// ```
+    #[inline]
+    #[unstable(feature = "result_map_or", issue = "66293")]
+    pub fn map_or<U, F: FnOnce(T) -> U>(self, default: U, f: F) -> U {
+        match self {
+            Ok(t) => f(t),
+            Err(_) => default,
+        }
+    }
+
     /// Maps a `Result<T, E>` to `U` by applying a function to a
     /// contained [`Ok`] value, or a fallback function to a
     /// contained [`Err`] value.
diff --git a/src/librustc/Cargo.toml b/src/librustc/Cargo.toml
index 92b94af75d750..bcbe765b85073 100644
--- a/src/librustc/Cargo.toml
+++ b/src/librustc/Cargo.toml
@@ -40,4 +40,3 @@ byteorder = { version = "1.3" }
 chalk-engine = { version = "0.9.0", default-features=false }
 rustc_fs_util = { path = "../librustc_fs_util" }
 smallvec = { version = "1.0", features = ["union", "may_dangle"] }
-measureme = "0.4"
diff --git a/src/librustc/error_codes.rs b/src/librustc/error_codes.rs
index f40b892a06bf2..d5c2db5fb9705 100644
--- a/src/librustc/error_codes.rs
+++ b/src/librustc/error_codes.rs
@@ -1896,6 +1896,51 @@ fn foo<'a>(x: &'a i32, y: &i32) -> &'a i32 {
 ```
 "##,
 
+E0623: r##"
+A lifetime didn't match what was expected.
+
+Erroneous code example:
+
+```compile_fail,E0623
+struct Foo<'a> {
+    x: &'a isize,
+}
+
+fn bar<'short, 'long>(c: Foo<'short>, l: &'long isize) {
+    let _: Foo<'long> = c; // error!
+}
+```
+
+In this example, we tried to set a value with an incompatible lifetime to
+another one (`'long` is unrelated to `'short`). We can solve this issue in
+two different ways:
+
+Either we make `'short` live at least as long as `'long`:
+
+```
+struct Foo<'a> {
+    x: &'a isize,
+}
+
+// we set 'short to live at least as long as 'long
+fn bar<'short: 'long, 'long>(c: Foo<'short>, l: &'long isize) {
+    let _: Foo<'long> = c; // ok!
+}
+```
+
+Or we use only one lifetime:
+
+```
+struct Foo<'a> {
+    x: &'a isize,
+}
+
+fn bar<'short>(c: Foo<'short>, l: &'short isize) {
+    let _: Foo<'short> = c; // ok!
+}
+```
+"##,
+
 E0635: r##"
 The `#![feature]` attribute specified an unknown feature.
 
@@ -2329,7 +2374,6 @@ the future, [RFC 2091] prohibits their implementation without a follow-up RFC.
     E0488, // lifetime of variable does not enclose its declaration
     E0489, // type/lifetime parameter not in scope here
     E0490, // a value of type `..` is borrowed for too long
-    E0623, // lifetime mismatch where both parameters are anonymous regions
     E0628, // generators cannot have explicit parameters
     E0631, // type mismatch in closure arguments
     E0637, // "'_" is not a valid lifetime bound
diff --git a/src/librustc/lib.rs b/src/librustc/lib.rs
index 0ea33d725f1e7..7dbacfd133f3f 100644
--- a/src/librustc/lib.rs
+++ b/src/librustc/lib.rs
@@ -124,7 +124,6 @@ pub mod util {
     pub mod captures;
     pub mod common;
     pub mod nodemap;
-    pub mod profiling;
     pub mod bug;
 }
 
diff --git a/src/librustc/lint/context.rs b/src/librustc/lint/context.rs
index 721baad25639f..dc3bc5fa0cebf 100644
--- a/src/librustc/lint/context.rs
+++ b/src/librustc/lint/context.rs
@@ -35,7 +35,6 @@ use crate::util::common::time;
 use errors::DiagnosticBuilder;
 use std::slice;
 use rustc_data_structures::sync::{self, ParallelIterator, join, par_iter};
-use rustc_serialize::{Decoder, Decodable, Encoder, Encodable};
 use syntax::ast;
 use syntax::util::lev_distance::find_best_match_for_name;
 use syntax::visit as ast_visit;
@@ -71,7 +70,7 @@ pub struct LintStore {
 
 /// Lints that are buffered up early on in the `Session` before the
 /// `LintLevels` is calculated
-#[derive(PartialEq, RustcEncodable, RustcDecodable, Debug)]
+#[derive(PartialEq, Debug)]
 pub struct BufferedEarlyLint {
     pub lint_id: LintId,
     pub ast_id: ast::NodeId,
@@ -1574,27 +1573,3 @@ pub fn check_ast_crate<T: EarlyLintPass>(
         }
     }
 }
-
-impl Encodable for LintId {
-    fn encode<S: Encoder>(&self, s: &mut S) -> Result<(), S::Error> {
-        s.emit_str(&self.lint.name.to_lowercase())
-    }
-}
-
-impl Decodable for LintId {
-    #[inline]
-    fn decode<D: Decoder>(d: &mut D) -> Result<LintId, D::Error> {
-        let s = d.read_str()?;
-        ty::tls::with(|tcx| {
-            match tcx.lint_store.find_lints(&s) {
-                Ok(ids) => {
-                    if ids.len() != 0 {
-                        panic!("invalid lint-id `{}`", s);
-                    }
-                    Ok(ids[0])
-                }
-                Err(_) => panic!("invalid lint-id `{}`", s),
-            }
-        })
-    }
-}
diff --git a/src/librustc/middle/cstore.rs b/src/librustc/middle/cstore.rs
index 1f4086227327e..e5c80c3589494 100644
--- a/src/librustc/middle/cstore.rs
+++ b/src/librustc/middle/cstore.rs
@@ -15,6 +15,7 @@ use std::path::{Path, PathBuf};
 use syntax::ast;
 use syntax::symbol::Symbol;
 use syntax_pos::Span;
+use syntax::expand::allocator::AllocatorKind;
 use rustc_target::spec::Target;
 use rustc_data_structures::sync::{self, MetadataRef};
 use rustc_macros::HashStable;
@@ -227,6 +228,8 @@ pub trait CrateStore {
     // utility functions
     fn encode_metadata(&self, tcx: TyCtxt<'_>) -> EncodedMetadata;
     fn metadata_encoding_version(&self) -> &[u8];
+    fn injected_panic_runtime(&self) -> Option<CrateNum>;
+    fn allocator_kind(&self) -> Option<AllocatorKind>;
 }
 
 pub type CrateStoreDyn = dyn CrateStore + sync::Sync;
diff --git a/src/librustc/session/mod.rs b/src/librustc/session/mod.rs
index 9792223ea1506..a69584cb90ad1 100644
--- a/src/librustc/session/mod.rs
+++ b/src/librustc/session/mod.rs
@@ -2,7 +2,6 @@ pub use self::code_stats::{DataTypeKind, SizeKind, FieldInfo, VariantInfo};
 use self::code_stats::CodeStats;
 
 use crate::dep_graph::cgu_reuse_tracker::CguReuseTracker;
-use crate::hir::def_id::CrateNum;
 use rustc_data_structures::fingerprint::Fingerprint;
 
 use crate::lint;
@@ -22,18 +21,17 @@ use errors::emitter::{Emitter, EmitterWriter};
 use errors::emitter::HumanReadableErrorType;
 use errors::annotate_snippet_emitter_writer::{AnnotateSnippetEmitterWriter};
 use syntax::edition::Edition;
-use syntax::expand::allocator::AllocatorKind;
 use syntax::feature_gate::{self, AttributeType};
 use syntax::json::JsonEmitter;
 use syntax::source_map;
 use syntax::sess::{ParseSess, ProcessCfgMod};
 use syntax::symbol::Symbol;
 use syntax_pos::{MultiSpan, Span};
-use crate::util::profiling::{SelfProfiler, SelfProfilerRef};
 
 use rustc_target::spec::{PanicStrategy, RelroLevel, Target, TargetTriple};
 use rustc_data_structures::flock;
 use rustc_data_structures::jobserver;
+use rustc_data_structures::profiling::{SelfProfiler, SelfProfilerRef};
 use ::jobserver::Client;
 
 use std;
@@ -102,12 +100,6 @@ pub struct Session {
     /// The maximum number of stackframes allowed in const eval.
     pub const_eval_stack_frame_limit: usize,
 
-    /// The `metadata::creader` module may inject an allocator/`panic_runtime`
-    /// dependency if it didn't already find one, and this tracks what was
-    /// injected.
-    pub allocator_kind: Once<Option<AllocatorKind>>,
-    pub injected_panic_runtime: Once<Option<CrateNum>>,
-
     /// Map from imported macro spans (which consist of
     /// the localized span for the macro body) to the
     /// macro name and definition span in the source crate.
@@ -1099,7 +1091,6 @@ fn build_session_(
             );
             match profiler {
                 Ok(profiler) => {
-                    crate::ty::query::QueryName::register_with_profiler(&profiler);
                     Some(Arc::new(profiler))
                 },
                 Err(e) => {
@@ -1182,8 +1173,6 @@ fn build_session_(
         recursion_limit: Once::new(),
         type_length_limit: Once::new(),
         const_eval_stack_frame_limit: 100,
-        allocator_kind: Once::new(),
-        injected_panic_runtime: Once::new(),
         imported_macro_spans: OneThread::new(RefCell::new(FxHashMap::default())),
         incr_comp_session: OneThread::new(RefCell::new(IncrCompSession::NotInitialized)),
         cgu_reuse_tracker,
diff --git a/src/librustc/ty/context.rs b/src/librustc/ty/context.rs
index 04e0f6f4b56d7..a15acb00c17fb 100644
--- a/src/librustc/ty/context.rs
+++ b/src/librustc/ty/context.rs
@@ -46,11 +46,11 @@ use crate::ty::CanonicalPolyFnSig;
 use crate::util::common::ErrorReported;
 use crate::util::nodemap::{DefIdMap, DefIdSet, ItemLocalMap, ItemLocalSet, NodeMap};
 use crate::util::nodemap::{FxHashMap, FxHashSet};
-use crate::util::profiling::SelfProfilerRef;
 
 use errors::DiagnosticBuilder;
 use arena::SyncDroplessArena;
 use smallvec::SmallVec;
+use rustc_data_structures::profiling::SelfProfilerRef;
 use rustc_data_structures::stable_hasher::{
     HashStable, StableHasher, StableVec, hash_stable_hashmap,
 };
@@ -75,6 +75,7 @@ use syntax::source_map::MultiSpan;
 use syntax::feature_gate;
 use syntax::symbol::{Symbol, kw, sym};
 use syntax_pos::Span;
+use syntax::expand::allocator::AllocatorKind;
 
 pub struct AllArenas {
     pub interner: SyncDroplessArena,
@@ -1338,6 +1339,14 @@ impl<'tcx> TyCtxt<'tcx> {
         self.all_crate_nums(LOCAL_CRATE)
     }
 
+    pub fn injected_panic_runtime(self) -> Option<CrateNum> {
+        self.cstore.injected_panic_runtime()
+    }
+
+    pub fn allocator_kind(self) -> Option<AllocatorKind> {
+        self.cstore.allocator_kind()
+    }
+
     pub fn features(self) -> &'tcx feature_gate::Features {
         self.features_query(LOCAL_CRATE)
     }
diff --git a/src/librustc/ty/query/config.rs b/src/librustc/ty/query/config.rs
index c1c6a655d96a9..7e126459dcc73 100644
--- a/src/librustc/ty/query/config.rs
+++ b/src/librustc/ty/query/config.rs
@@ -6,7 +6,7 @@ use crate::ty::query::queries;
 use crate::ty::query::{Query, QueryName};
 use crate::ty::query::QueryCache;
 use crate::ty::query::plumbing::CycleError;
-use crate::util::profiling::ProfileCategory;
+use rustc_data_structures::profiling::ProfileCategory;
 
 use std::borrow::Cow;
 use std::hash::Hash;
diff --git a/src/librustc/ty/query/mod.rs b/src/librustc/ty/query/mod.rs
index 0615004125b3c..a1eb1c43335b1 100644
--- a/src/librustc/ty/query/mod.rs
+++ b/src/librustc/ty/query/mod.rs
@@ -39,7 +39,7 @@ use crate::ty::util::NeedsDrop;
 use crate::ty::subst::SubstsRef;
 use crate::util::nodemap::{DefIdSet, DefIdMap};
 use crate::util::common::ErrorReported;
-use crate::util::profiling::ProfileCategory::*;
+use rustc_data_structures::profiling::ProfileCategory::*;
 
 use rustc_data_structures::svh::Svh;
 use rustc_index::vec::IndexVec;
diff --git a/src/librustc/ty/query/plumbing.rs b/src/librustc/ty/query/plumbing.rs
index 538154b035ac6..1c15b7d5f3559 100644
--- a/src/librustc/ty/query/plumbing.rs
+++ b/src/librustc/ty/query/plumbing.rs
@@ -672,7 +672,7 @@ macro_rules! define_queries_inner {
             rustc_data_structures::stable_hasher::StableHasher,
             ich::StableHashingContext
         };
-        use crate::util::profiling::ProfileCategory;
+        use rustc_data_structures::profiling::ProfileCategory;
 
         define_queries_struct! {
             tcx: $tcx,
@@ -816,8 +816,20 @@ macro_rules! define_queries_inner {
             $($name),*
         }
 
+        impl rustc_data_structures::profiling::QueryName for QueryName {
+            fn discriminant(self) -> std::mem::Discriminant<QueryName> {
+                std::mem::discriminant(&self)
+            }
+
+            fn as_str(self) -> &'static str {
+                QueryName::as_str(&self)
+            }
+        }
+
         impl QueryName {
-            pub fn register_with_profiler(profiler: &crate::util::profiling::SelfProfiler) {
+            pub fn register_with_profiler(
+                profiler: &rustc_data_structures::profiling::SelfProfiler,
+            ) {
                 $(profiler.register_query_name(QueryName::$name);)*
             }
 
diff --git a/src/librustc_codegen_ssa/back/symbol_export.rs b/src/librustc_codegen_ssa/back/symbol_export.rs
index 35b62603b076a..f8b3e0ffe5cd9 100644
--- a/src/librustc_codegen_ssa/back/symbol_export.rs
+++ b/src/librustc_codegen_ssa/back/symbol_export.rs
@@ -194,7 +194,7 @@ fn exported_symbols_provider_local(
         symbols.push((exported_symbol, SymbolExportLevel::C));
     }
 
-    if tcx.sess.allocator_kind.get().is_some() {
+    if tcx.allocator_kind().is_some() {
         for method in ALLOCATOR_METHODS {
             let symbol_name = format!("__rust_{}", method.name);
             let exported_symbol = ExportedSymbol::NoDefId(SymbolName::new(&symbol_name));
diff --git a/src/librustc_codegen_ssa/back/write.rs b/src/librustc_codegen_ssa/back/write.rs
index b302b9ae7f0e4..ed901fa064a4e 100644
--- a/src/librustc_codegen_ssa/back/write.rs
+++ b/src/librustc_codegen_ssa/back/write.rs
@@ -19,7 +19,7 @@ use rustc::util::nodemap::FxHashMap;
 use rustc::hir::def_id::{CrateNum, LOCAL_CRATE};
 use rustc::ty::TyCtxt;
 use rustc::util::common::{time_depth, set_time_depth, print_time_passes_entry};
-use rustc::util::profiling::SelfProfilerRef;
+use rustc_data_structures::profiling::SelfProfilerRef;
 use rustc_fs_util::link_or_copy;
 use rustc_data_structures::svh::Svh;
 use rustc_data_structures::sync::Lrc;
diff --git a/src/librustc_codegen_ssa/base.rs b/src/librustc_codegen_ssa/base.rs
index c3f2a5161ae1c..faa7b588e56e3 100644
--- a/src/librustc_codegen_ssa/base.rs
+++ b/src/librustc_codegen_ssa/base.rs
@@ -549,7 +549,7 @@ pub fn codegen_crate<B: ExtraBackendMethods>(
         });
     let allocator_module = if any_dynamic_crate {
         None
-    } else if let Some(kind) = *tcx.sess.allocator_kind.get() {
+    } else if let Some(kind) = tcx.allocator_kind() {
         let llmod_id = cgu_name_builder.build_cgu_name(LOCAL_CRATE,
                                                        &["crate"],
                                                        Some("allocator")).to_string();
diff --git a/src/librustc_data_structures/Cargo.toml b/src/librustc_data_structures/Cargo.toml
index e79b3a81b9654..0fd47115022c2 100644
--- a/src/librustc_data_structures/Cargo.toml
+++ b/src/librustc_data_structures/Cargo.toml
@@ -25,6 +25,8 @@ rayon-core = { version = "0.3.0", package = "rustc-rayon-core" }
 rustc-hash = "1.0.1"
 smallvec = { version = "1.0", features = ["union", "may_dangle"] }
 rustc_index = { path = "../librustc_index", package = "rustc_index" }
+bitflags = "1.2.1"
+measureme = "0.4"
 
 [dependencies.parking_lot]
 version = "0.9"
diff --git a/src/librustc_data_structures/lib.rs b/src/librustc_data_structures/lib.rs
index 474a42644d915..fb541637e5f79 100644
--- a/src/librustc_data_structures/lib.rs
+++ b/src/librustc_data_structures/lib.rs
@@ -94,6 +94,7 @@ pub use ena::unify;
 pub mod vec_linked_list;
 pub mod work_queue;
 pub mod fingerprint;
+pub mod profiling;
 
 pub struct OnDrop<F: Fn()>(pub F);
 
diff --git a/src/librustc/util/profiling.rs b/src/librustc_data_structures/profiling.rs
similarity index 92%
rename from src/librustc/util/profiling.rs
rename to src/librustc_data_structures/profiling.rs
index 5a1b7f3aa4cb8..86f59bfabe627 100644
--- a/src/librustc/util/profiling.rs
+++ b/src/librustc_data_structures/profiling.rs
@@ -7,8 +7,6 @@ use std::sync::Arc;
 use std::thread::ThreadId;
 use std::u32;
 
-use crate::ty::query::QueryName;
-
 use measureme::{StringId, TimestampKind};
 
 /// MmapSerializatioSink is faster on macOS and Linux
@@ -20,6 +18,10 @@ type SerializationSink = measureme::FileSerializationSink;
 
 type Profiler = measureme::Profiler<SerializationSink>;
 
+pub trait QueryName: Sized + Copy {
+    fn discriminant(self) -> Discriminant<Self>;
+    fn as_str(self) -> &'static str;
+}
 
 #[derive(Clone, Copy, Debug, PartialEq, Eq, Ord, PartialOrd)]
 pub enum ProfileCategory {
@@ -32,7 +34,7 @@ pub enum ProfileCategory {
     Other,
 }
 
-bitflags! {
+bitflags::bitflags! {
     struct EventFilter: u32 {
         const GENERIC_ACTIVITIES = 1 << 0;
         const QUERY_PROVIDERS    = 1 << 1;
@@ -137,7 +139,7 @@ impl SelfProfilerRef {
     /// Start profiling a query provider. Profiling continues until the
     /// TimingGuard returned from this call is dropped.
     #[inline(always)]
-    pub fn query_provider(&self, query_name: QueryName) -> TimingGuard<'_> {
+    pub fn query_provider(&self, query_name: impl QueryName) -> TimingGuard<'_> {
         self.exec(EventFilter::QUERY_PROVIDERS, |profiler| {
             let event_id = SelfProfiler::get_query_name_string_id(query_name);
             TimingGuard::start(profiler, profiler.query_event_kind, event_id)
@@ -146,7 +148,7 @@ impl SelfProfilerRef {
 
     /// Record a query in-memory cache hit.
     #[inline(always)]
-    pub fn query_cache_hit(&self, query_name: QueryName) {
+    pub fn query_cache_hit(&self, query_name: impl QueryName) {
         self.non_guard_query_event(
             |profiler| profiler.query_cache_hit_event_kind,
             query_name,
@@ -159,7 +161,7 @@ impl SelfProfilerRef {
     /// Profiling continues until the TimingGuard returned from this call is
     /// dropped.
     #[inline(always)]
-    pub fn query_blocked(&self, query_name: QueryName) -> TimingGuard<'_> {
+    pub fn query_blocked(&self, query_name: impl QueryName) -> TimingGuard<'_> {
         self.exec(EventFilter::QUERY_BLOCKED, |profiler| {
             let event_id = SelfProfiler::get_query_name_string_id(query_name);
             TimingGuard::start(profiler, profiler.query_blocked_event_kind, event_id)
@@ -170,7 +172,7 @@ impl SelfProfilerRef {
     /// incremental compilation on-disk cache. Profiling continues until the
     /// TimingGuard returned from this call is dropped.
     #[inline(always)]
-    pub fn incr_cache_loading(&self, query_name: QueryName) -> TimingGuard<'_> {
+    pub fn incr_cache_loading(&self, query_name: impl QueryName) -> TimingGuard<'_> {
         self.exec(EventFilter::INCR_CACHE_LOADS, |profiler| {
             let event_id = SelfProfiler::get_query_name_string_id(query_name);
             TimingGuard::start(
@@ -185,7 +187,7 @@ impl SelfProfilerRef {
     fn non_guard_query_event(
         &self,
         event_kind: fn(&SelfProfiler) -> StringId,
-        query_name: QueryName,
+        query_name: impl QueryName,
         event_filter: EventFilter,
         timestamp_kind: TimestampKind
     ) {
@@ -203,6 +205,12 @@ impl SelfProfilerRef {
             TimingGuard::none()
         }));
     }
+
+    pub fn register_queries(&self, f: impl FnOnce(&SelfProfiler)) {
+        if let Some(profiler) = &self.profiler {
+            f(&profiler)
+        }
+    }
 }
 
 pub struct SelfProfiler {
@@ -274,15 +282,15 @@ impl SelfProfiler {
         })
     }
 
-    fn get_query_name_string_id(query_name: QueryName) -> StringId {
+    fn get_query_name_string_id(query_name: impl QueryName) -> StringId {
         let discriminant = unsafe {
-            mem::transmute::<Discriminant<QueryName>, u64>(mem::discriminant(&query_name))
+            mem::transmute::<Discriminant<_>, u64>(query_name.discriminant())
         };
 
         StringId::reserved(discriminant as u32)
     }
 
-    pub fn register_query_name(&self, query_name: QueryName) {
+    pub fn register_query_name(&self, query_name: impl QueryName) {
         let id = SelfProfiler::get_query_name_string_id(query_name);
         self.profiler.alloc_string_with_reserved_id(id, query_name.as_str());
     }
diff --git a/src/librustc_driver/lib.rs b/src/librustc_driver/lib.rs
index 10bc6599e7592..514c6d0e1dad9 100644
--- a/src/librustc_driver/lib.rs
+++ b/src/librustc_driver/lib.rs
@@ -181,6 +181,7 @@ pub fn run_compiler(
             crate_name: None,
             lint_caps: Default::default(),
             register_lints: None,
+            override_queries: None,
         };
         callbacks.config(&mut config);
         config
@@ -259,6 +260,7 @@ pub fn run_compiler(
         crate_name: None,
         lint_caps: Default::default(),
         register_lints: None,
+        override_queries: None,
     };
 
     callbacks.config(&mut config);
diff --git a/src/librustc_interface/interface.rs b/src/librustc_interface/interface.rs
index 02068b2ce388d..fae4eb48c4a1b 100644
--- a/src/librustc_interface/interface.rs
+++ b/src/librustc_interface/interface.rs
@@ -12,6 +12,7 @@ use rustc_data_structures::OnDrop;
 use rustc_data_structures::sync::Lrc;
 use rustc_data_structures::fx::{FxHashSet, FxHashMap};
 use rustc_parse::new_parser_from_source_str;
+use rustc::ty;
 use std::path::PathBuf;
 use std::result;
 use std::sync::{Arc, Mutex};
@@ -38,6 +39,8 @@ pub struct Compiler {
     pub(crate) queries: Queries,
     pub(crate) crate_name: Option<String>,
     pub(crate) register_lints: Option<Box<dyn Fn(&Session, &mut lint::LintStore) + Send + Sync>>,
+    pub(crate) override_queries:
+        Option<fn(&Session, &mut ty::query::Providers<'_>, &mut ty::query::Providers<'_>)>,
 }
 
 impl Compiler {
@@ -131,6 +134,13 @@ pub struct Config {
     /// Note that if you find a Some here you probably want to call that function in the new
     /// function being registered.
     pub register_lints: Option<Box<dyn Fn(&Session, &mut lint::LintStore) + Send + Sync>>,
+
+    /// This is a callback from the driver that is called just after we have populated
+    /// the list of queries.
+    ///
+    /// The second parameter is local providers and the third parameter is external providers.
+    pub override_queries:
+        Option<fn(&Session, &mut ty::query::Providers<'_>, &mut ty::query::Providers<'_>)>,
 }
 
 pub fn run_compiler_in_existing_thread_pool<F, R>(config: Config, f: F) -> R
@@ -157,6 +167,7 @@ where
         queries: Default::default(),
         crate_name: config.crate_name,
         register_lints: config.register_lints,
+        override_queries: config.override_queries,
     };
 
     let _sess_abort_error = OnDrop(|| {
diff --git a/src/librustc_interface/passes.rs b/src/librustc_interface/passes.rs
index 453007c564246..c57622b8b8fe5 100644
--- a/src/librustc_interface/passes.rs
+++ b/src/librustc_interface/passes.rs
@@ -786,6 +786,7 @@ pub fn create_global_ctxt(
     let codegen_backend = compiler.codegen_backend().clone();
     let crate_name = crate_name.to_string();
     let defs = mem::take(&mut resolver_outputs.definitions);
+    let override_queries = compiler.override_queries;
 
     let ((), result) = BoxedGlobalCtxt::new(static move || {
         let sess = &*sess;
@@ -810,6 +811,10 @@ pub fn create_global_ctxt(
         default_provide_extern(&mut extern_providers);
         codegen_backend.provide_extern(&mut extern_providers);
 
+        if let Some(callback) = override_queries {
+            callback(sess, &mut local_providers, &mut extern_providers);
+        }
+
         let gcx = TyCtxt::create_global_ctxt(
             sess,
             lint_store,
diff --git a/src/librustc_interface/util.rs b/src/librustc_interface/util.rs
index 115345955aea3..6b9d708cefaca 100644
--- a/src/librustc_interface/util.rs
+++ b/src/librustc_interface/util.rs
@@ -108,6 +108,10 @@ pub fn create_session(
         process_configure_mod,
     );
 
+    sess.prof.register_queries(|profiler| {
+        rustc::ty::query::QueryName::register_with_profiler(&profiler);
+    });
+
     let codegen_backend = get_codegen_backend(&sess);
 
     let mut cfg = config::build_configuration(&sess, config::to_crate_config(cfg));
diff --git a/src/librustc_metadata/creader.rs b/src/librustc_metadata/creader.rs
index 05e3ee3322e59..b4dea19d3dc3f 100644
--- a/src/librustc_metadata/creader.rs
+++ b/src/librustc_metadata/creader.rs
@@ -531,7 +531,7 @@ impl<'a> CrateLoader<'a> {
         });
         if !any_non_rlib {
             info!("panic runtime injection skipped, only generating rlib");
-            self.sess.injected_panic_runtime.set(None);
+            self.cstore.injected_panic_runtime = None;
             return
         }
 
@@ -563,7 +563,7 @@ impl<'a> CrateLoader<'a> {
         // we just don't need one at all, then we're done here and there's
         // nothing else to do.
         if !needs_panic_runtime || runtime_found {
-            self.sess.injected_panic_runtime.set(None);
+            self.cstore.injected_panic_runtime = None;
             return
         }
 
@@ -600,7 +600,7 @@ impl<'a> CrateLoader<'a> {
                                    name, desired_strategy.desc()));
         }
 
-        self.sess.injected_panic_runtime.set(Some(cnum));
+        self.cstore.injected_panic_runtime = Some(cnum);
         self.inject_dependency_if(cnum, "a panic runtime",
                                   &|data| data.root.needs_panic_runtime);
     }
@@ -722,7 +722,7 @@ impl<'a> CrateLoader<'a> {
         }
     }
 
-    fn inject_allocator_crate(&self, krate: &ast::Crate) {
+    fn inject_allocator_crate(&mut self, krate: &ast::Crate) {
         let has_global_allocator = match &*global_allocator_spans(krate) {
             [span1, span2, ..] => {
                 self.sess.struct_span_err(*span2, "cannot define multiple global allocators")
@@ -742,7 +742,7 @@ impl<'a> CrateLoader<'a> {
             needs_allocator = needs_allocator || data.root.needs_allocator;
         });
         if !needs_allocator {
-            self.sess.allocator_kind.set(None);
+            self.cstore.allocator_kind = None;
             return
         }
 
@@ -758,7 +758,7 @@ impl<'a> CrateLoader<'a> {
                 }
             });
         if all_rlib {
-            self.sess.allocator_kind.set(None);
+            self.cstore.allocator_kind = None;
             return
         }
 
@@ -795,7 +795,7 @@ impl<'a> CrateLoader<'a> {
             }
         });
         if global_allocator.is_some() {
-            self.sess.allocator_kind.set(Some(AllocatorKind::Global));
+            self.cstore.allocator_kind = Some(AllocatorKind::Global);
             return
         }
 
@@ -816,7 +816,7 @@ impl<'a> CrateLoader<'a> {
                            add `#[global_allocator]` to a static item \
                            that implements the GlobalAlloc trait.");
         }
-        self.sess.allocator_kind.set(Some(AllocatorKind::DefaultLib));
+        self.cstore.allocator_kind = Some(AllocatorKind::DefaultLib);
     }
 
     fn inject_dependency_if(&self,
diff --git a/src/librustc_metadata/cstore.rs b/src/librustc_metadata/cstore.rs
index c6c8ee575a98a..54857ce1b8281 100644
--- a/src/librustc_metadata/cstore.rs
+++ b/src/librustc_metadata/cstore.rs
@@ -14,6 +14,7 @@ use rustc_data_structures::svh::Svh;
 use syntax::ast;
 use syntax::edition::Edition;
 use syntax_expand::base::SyntaxExtension;
+use syntax::expand::allocator::AllocatorKind;
 use syntax_pos;
 use proc_macro::bridge::client::ProcMacro;
 
@@ -101,6 +102,8 @@ crate struct CrateMetadata {
 #[derive(Clone)]
 pub struct CStore {
     metas: IndexVec<CrateNum, Option<Lrc<CrateMetadata>>>,
+    pub(crate) injected_panic_runtime: Option<CrateNum>,
+    pub(crate) allocator_kind: Option<AllocatorKind>,
 }
 
 pub enum LoadedMacro {
@@ -116,6 +119,8 @@ impl Default for CStore {
             // corresponding `CrateNum`. This first entry will always remain
             // `None`.
             metas: IndexVec::from_elem_n(None, 1),
+            injected_panic_runtime: None,
+            allocator_kind: None,
         }
     }
 }
diff --git a/src/librustc_metadata/dependency_format.rs b/src/librustc_metadata/dependency_format.rs
index 7f76a9730e198..dbf7fede1469f 100644
--- a/src/librustc_metadata/dependency_format.rs
+++ b/src/librustc_metadata/dependency_format.rs
@@ -184,7 +184,7 @@ fn calculate_type(tcx: TyCtxt<'_>, ty: config::CrateType) -> DependencyList {
     //
     // Things like allocators and panic runtimes may not have been activated
     // quite yet, so do so here.
-    activate_injected_dep(*sess.injected_panic_runtime.get(), &mut ret,
+    activate_injected_dep(tcx.injected_panic_runtime(), &mut ret,
                           &|cnum| tcx.is_panic_runtime(cnum));
 
     // When dylib B links to dylib A, then when using B we must also link to A.
@@ -244,7 +244,6 @@ fn add_library(
 }
 
 fn attempt_static(tcx: TyCtxt<'_>) -> Option<DependencyList> {
-    let sess = &tcx.sess;
     let crates = cstore::used_crates(tcx, RequireStatic);
     if !crates.iter().by_ref().all(|&(_, ref p)| p.is_some()) {
         return None
@@ -264,7 +263,7 @@ fn attempt_static(tcx: TyCtxt<'_>) -> Option<DependencyList> {
     // Our allocator/panic runtime may not have been linked above if it wasn't
     // explicitly linked, which is the case for any injected dependency. Handle
     // that here and activate them.
-    activate_injected_dep(*sess.injected_panic_runtime.get(), &mut ret,
+    activate_injected_dep(tcx.injected_panic_runtime(), &mut ret,
                           &|cnum| tcx.is_panic_runtime(cnum));
 
     Some(ret)
diff --git a/src/librustc_metadata/rmeta/decoder/cstore_impl.rs b/src/librustc_metadata/rmeta/decoder/cstore_impl.rs
index 015866548cd38..a6cb3864ca7d4 100644
--- a/src/librustc_metadata/rmeta/decoder/cstore_impl.rs
+++ b/src/librustc_metadata/rmeta/decoder/cstore_impl.rs
@@ -31,6 +31,7 @@ use syntax::attr;
 use syntax::source_map;
 use syntax::source_map::Spanned;
 use syntax::symbol::Symbol;
+use syntax::expand::allocator::AllocatorKind;
 use syntax_pos::{Span, FileName};
 
 macro_rules! provide {
@@ -527,4 +528,12 @@ impl CrateStore for cstore::CStore {
     {
         rmeta::METADATA_HEADER
     }
+
+    fn injected_panic_runtime(&self) -> Option<CrateNum> {
+        self.injected_panic_runtime
+    }
+
+    fn allocator_kind(&self) -> Option<AllocatorKind> {
+        self.allocator_kind
+    }
 }
diff --git a/src/librustc_mir/hair/pattern/_match.rs b/src/librustc_mir/hair/pattern/_match.rs
index 982330baf9c95..8e574cc961b2b 100644
--- a/src/librustc_mir/hair/pattern/_match.rs
+++ b/src/librustc_mir/hair/pattern/_match.rs
@@ -560,13 +560,6 @@ impl<'a, 'tcx> MatchCheckCtxt<'a, 'tcx> {
         }
     }
 
-    fn is_non_exhaustive_enum(&self, ty: Ty<'tcx>) -> bool {
-        match ty.kind {
-            ty::Adt(adt_def, ..) => adt_def.is_variant_list_non_exhaustive(),
-            _ => false,
-        }
-    }
-
     fn is_local(&self, ty: Ty<'tcx>) -> bool {
         match ty.kind {
             ty::Adt(adt_def, ..) => adt_def.did.is_local(),
@@ -590,6 +583,8 @@ enum Constructor<'tcx> {
     FixedLenSlice(u64),
     /// Slice patterns. Captures any array constructor of `length >= i + j`.
     VarLenSlice(u64, u64),
+    /// Fake extra constructor for enums that aren't allowed to be matched exhaustively.
+    NonExhaustive,
 }
 
 // Ignore spans when comparing, they don't carry semantic information as they are only for lints.
@@ -597,6 +592,7 @@ impl<'tcx> std::cmp::PartialEq for Constructor<'tcx> {
     fn eq(&self, other: &Self) -> bool {
         match (self, other) {
             (Constructor::Single, Constructor::Single) => true,
+            (Constructor::NonExhaustive, Constructor::NonExhaustive) => true,
             (Constructor::Variant(a), Constructor::Variant(b)) => a == b,
             (Constructor::ConstantValue(a, _), Constructor::ConstantValue(b, _)) => a == b,
             (
@@ -771,6 +767,8 @@ impl<'tcx> Constructor<'tcx> {
                 // ranges have been omitted.
                 remaining_ctors
             }
+            // This constructor is never covered by anything else
+            NonExhaustive => vec![NonExhaustive],
         }
     }
 
@@ -781,65 +779,68 @@ impl<'tcx> Constructor<'tcx> {
         ty: Ty<'tcx>,
     ) -> Vec<Pat<'tcx>> {
         debug!("wildcard_subpatterns({:#?}, {:?})", self, ty);
-        match ty.kind {
-            ty::Tuple(ref fs) => {
-                fs.into_iter().map(|t| t.expect_ty()).map(Pat::wildcard_from_ty).collect()
-            }
-            ty::Slice(ty) | ty::Array(ty, _) => match *self {
-                FixedLenSlice(length) => (0..length).map(|_| Pat::wildcard_from_ty(ty)).collect(),
-                VarLenSlice(prefix, suffix) => {
-                    (0..prefix + suffix).map(|_| Pat::wildcard_from_ty(ty)).collect()
+
+        match self {
+            Single | Variant(_) => match ty.kind {
+                ty::Tuple(ref fs) => {
+                    fs.into_iter().map(|t| t.expect_ty()).map(Pat::wildcard_from_ty).collect()
                 }
-                ConstantValue(..) => vec![],
-                _ => bug!("bad slice pattern {:?} {:?}", self, ty),
-            },
-            ty::Ref(_, rty, _) => vec![Pat::wildcard_from_ty(rty)],
-            ty::Adt(adt, substs) => {
-                if adt.is_box() {
-                    // Use T as the sub pattern type of Box<T>.
-                    vec![Pat::wildcard_from_ty(substs.type_at(0))]
-                } else {
-                    let variant = &adt.variants[self.variant_index_for_adt(cx, adt)];
-                    let is_non_exhaustive =
-                        variant.is_field_list_non_exhaustive() && !cx.is_local(ty);
-                    variant
-                        .fields
-                        .iter()
-                        .map(|field| {
-                            let is_visible =
-                                adt.is_enum() || field.vis.is_accessible_from(cx.module, cx.tcx);
-                            let is_uninhabited = cx.is_uninhabited(field.ty(cx.tcx, substs));
-                            match (is_visible, is_non_exhaustive, is_uninhabited) {
-                                // Treat all uninhabited types in non-exhaustive variants as
-                                // `TyErr`.
-                                (_, true, true) => cx.tcx.types.err,
-                                // Treat all non-visible fields as `TyErr`. They can't appear in
-                                // any other pattern from this match (because they are private), so
-                                // their type does not matter - but we don't want to know they are
-                                // uninhabited.
-                                (false, ..) => cx.tcx.types.err,
-                                (true, ..) => {
-                                    let ty = field.ty(cx.tcx, substs);
-                                    match ty.kind {
-                                        // If the field type returned is an array of an unknown
-                                        // size return an TyErr.
-                                        ty::Array(_, len)
-                                            if len
-                                                .try_eval_usize(cx.tcx, cx.param_env)
-                                                .is_none() =>
-                                        {
-                                            cx.tcx.types.err
+                ty::Ref(_, rty, _) => vec![Pat::wildcard_from_ty(rty)],
+                ty::Adt(adt, substs) => {
+                    if adt.is_box() {
+                        // Use T as the sub pattern type of Box<T>.
+                        vec![Pat::wildcard_from_ty(substs.type_at(0))]
+                    } else {
+                        let variant = &adt.variants[self.variant_index_for_adt(cx, adt)];
+                        let is_non_exhaustive =
+                            variant.is_field_list_non_exhaustive() && !cx.is_local(ty);
+                        variant
+                            .fields
+                            .iter()
+                            .map(|field| {
+                                let is_visible = adt.is_enum()
+                                    || field.vis.is_accessible_from(cx.module, cx.tcx);
+                                let is_uninhabited = cx.is_uninhabited(field.ty(cx.tcx, substs));
+                                match (is_visible, is_non_exhaustive, is_uninhabited) {
+                                    // Treat all uninhabited types in non-exhaustive variants as
+                                    // `TyErr`.
+                                    (_, true, true) => cx.tcx.types.err,
+                                    // Treat all non-visible fields as `TyErr`. They can't appear
+                                    // in any other pattern from this match (because they are
+                                    // private), so their type does not matter - but we don't want
+                                    // to know they are uninhabited.
+                                    (false, ..) => cx.tcx.types.err,
+                                    (true, ..) => {
+                                        let ty = field.ty(cx.tcx, substs);
+                                        match ty.kind {
+                                            // If the field type returned is an array of an unknown
+                                            // size return an TyErr.
+                                            ty::Array(_, len)
+                                                if len
+                                                    .try_eval_usize(cx.tcx, cx.param_env)
+                                                    .is_none() =>
+                                            {
+                                                cx.tcx.types.err
+                                            }
+                                            _ => ty,
                                         }
-                                        _ => ty,
                                     }
                                 }
-                            }
-                        })
-                        .map(Pat::wildcard_from_ty)
-                        .collect()
+                            })
+                            .map(Pat::wildcard_from_ty)
+                            .collect()
+                    }
                 }
-            }
-            _ => vec![],
+                _ => vec![],
+            },
+            FixedLenSlice(_) | VarLenSlice(..) => match ty.kind {
+                ty::Slice(ty) | ty::Array(ty, _) => {
+                    let arity = self.arity(cx, ty);
+                    (0..arity).map(|_| Pat::wildcard_from_ty(ty)).collect()
+                }
+                _ => bug!("bad slice pattern {:?} {:?}", self, ty),
+            },
+            ConstantValue(..) | ConstantRange(..) | NonExhaustive => vec![],
         }
     }
 
@@ -850,19 +851,19 @@ impl<'tcx> Constructor<'tcx> {
     /// A struct pattern's arity is the number of fields it contains, etc.
     fn arity<'a>(&self, cx: &MatchCheckCtxt<'a, 'tcx>, ty: Ty<'tcx>) -> u64 {
         debug!("Constructor::arity({:#?}, {:?})", self, ty);
-        match ty.kind {
-            ty::Tuple(ref fs) => fs.len() as u64,
-            ty::Slice(..) | ty::Array(..) => match *self {
-                FixedLenSlice(length) => length,
-                VarLenSlice(prefix, suffix) => prefix + suffix,
-                ConstantValue(..) => 0,
-                _ => bug!("bad slice pattern {:?} {:?}", self, ty),
+        match self {
+            Single | Variant(_) => match ty.kind {
+                ty::Tuple(ref fs) => fs.len() as u64,
+                ty::Slice(..) | ty::Array(..) => bug!("bad slice pattern {:?} {:?}", self, ty),
+                ty::Ref(..) => 1,
+                ty::Adt(adt, _) => {
+                    adt.variants[self.variant_index_for_adt(cx, adt)].fields.len() as u64
+                }
+                _ => 0,
             },
-            ty::Ref(..) => 1,
-            ty::Adt(adt, _) => {
-                adt.variants[self.variant_index_for_adt(cx, adt)].fields.len() as u64
-            }
-            _ => 0,
+            FixedLenSlice(length) => *length,
+            VarLenSlice(prefix, suffix) => prefix + suffix,
+            ConstantValue(..) | ConstantRange(..) | NonExhaustive => 0,
         }
     }
 
@@ -886,53 +887,50 @@ impl<'tcx> Constructor<'tcx> {
         pats: impl IntoIterator<Item = Pat<'tcx>>,
     ) -> Pat<'tcx> {
         let mut subpatterns = pats.into_iter();
-        let pat = match ty.kind {
-            ty::Adt(..) | ty::Tuple(..) => {
-                let subpatterns = subpatterns
-                    .enumerate()
-                    .map(|(i, p)| FieldPat { field: Field::new(i), pattern: p })
-                    .collect();
-
-                if let ty::Adt(adt, substs) = ty.kind {
-                    if adt.is_enum() {
-                        PatKind::Variant {
-                            adt_def: adt,
-                            substs,
-                            variant_index: self.variant_index_for_adt(cx, adt),
-                            subpatterns,
+
+        let pat = match self {
+            Single | Variant(_) => match ty.kind {
+                ty::Adt(..) | ty::Tuple(..) => {
+                    let subpatterns = subpatterns
+                        .enumerate()
+                        .map(|(i, p)| FieldPat { field: Field::new(i), pattern: p })
+                        .collect();
+
+                    if let ty::Adt(adt, substs) = ty.kind {
+                        if adt.is_enum() {
+                            PatKind::Variant {
+                                adt_def: adt,
+                                substs,
+                                variant_index: self.variant_index_for_adt(cx, adt),
+                                subpatterns,
+                            }
+                        } else {
+                            PatKind::Leaf { subpatterns }
                         }
                     } else {
                         PatKind::Leaf { subpatterns }
                     }
-                } else {
-                    PatKind::Leaf { subpatterns }
-                }
-            }
-
-            ty::Ref(..) => PatKind::Deref { subpattern: subpatterns.nth(0).unwrap() },
-
-            ty::Slice(_) | ty::Array(..) => match self {
-                FixedLenSlice(_) => {
-                    PatKind::Slice { prefix: subpatterns.collect(), slice: None, suffix: vec![] }
                 }
-                VarLenSlice(prefix_len, _suffix_len) => {
-                    let prefix = subpatterns.by_ref().take(*prefix_len as usize).collect();
-                    let suffix = subpatterns.collect();
-                    let wild = Pat::wildcard_from_ty(ty);
-                    PatKind::Slice { prefix, slice: Some(wild), suffix }
-                }
-                _ => bug!("bad slice pattern {:?} {:?}", self, ty),
-            },
-
-            _ => match *self {
-                ConstantValue(value, _) => PatKind::Constant { value },
-                ConstantRange(lo, hi, ty, end, _) => PatKind::Range(PatRange {
-                    lo: ty::Const::from_bits(cx.tcx, lo, ty::ParamEnv::empty().and(ty)),
-                    hi: ty::Const::from_bits(cx.tcx, hi, ty::ParamEnv::empty().and(ty)),
-                    end,
-                }),
+                ty::Ref(..) => PatKind::Deref { subpattern: subpatterns.nth(0).unwrap() },
+                ty::Slice(_) | ty::Array(..) => bug!("bad slice pattern {:?} {:?}", self, ty),
                 _ => PatKind::Wild,
             },
+            FixedLenSlice(_) => {
+                PatKind::Slice { prefix: subpatterns.collect(), slice: None, suffix: vec![] }
+            }
+            &VarLenSlice(prefix_len, _) => {
+                let prefix = subpatterns.by_ref().take(prefix_len as usize).collect();
+                let suffix = subpatterns.collect();
+                let wild = Pat::wildcard_from_ty(ty);
+                PatKind::Slice { prefix, slice: Some(wild), suffix }
+            }
+            &ConstantValue(value, _) => PatKind::Constant { value },
+            &ConstantRange(lo, hi, ty, end, _) => PatKind::Range(PatRange {
+                lo: ty::Const::from_bits(cx.tcx, lo, ty::ParamEnv::empty().and(ty)),
+                hi: ty::Const::from_bits(cx.tcx, hi, ty::ParamEnv::empty().and(ty)),
+                end,
+            }),
+            NonExhaustive => PatKind::Wild,
         };
 
         Pat { ty, span: DUMMY_SP, kind: Box::new(pat) }
@@ -1128,7 +1126,7 @@ fn all_constructors<'a, 'tcx>(
     pcx: PatCtxt<'tcx>,
 ) -> Vec<Constructor<'tcx>> {
     debug!("all_constructors({:?})", pcx.ty);
-    let ctors = match pcx.ty.kind {
+    match pcx.ty.kind {
         ty::Bool => [true, false]
             .iter()
             .map(|&b| ConstantValue(ty::Const::from_bool(cx.tcx, b), pcx.span))
@@ -1145,17 +1143,49 @@ fn all_constructors<'a, 'tcx>(
                 vec![VarLenSlice(0, 0)]
             }
         }
-        ty::Adt(def, substs) if def.is_enum() => def
-            .variants
-            .iter()
-            .filter(|v| {
-                !cx.tcx.features().exhaustive_patterns
-                    || !v
-                        .uninhabited_from(cx.tcx, substs, def.adt_kind())
-                        .contains(cx.tcx, cx.module)
-            })
-            .map(|v| Variant(v.def_id))
-            .collect(),
+        ty::Adt(def, substs) if def.is_enum() => {
+            let ctors: Vec<_> = def
+                .variants
+                .iter()
+                .filter(|v| {
+                    !cx.tcx.features().exhaustive_patterns
+                        || !v
+                            .uninhabited_from(cx.tcx, substs, def.adt_kind())
+                            .contains(cx.tcx, cx.module)
+                })
+                .map(|v| Variant(v.def_id))
+                .collect();
+
+            // If our scrutinee is *privately* an empty enum, we must treat it as though it had an
+            // "unknown" constructor (in that case, all other patterns obviously can't be variants)
+            // to avoid exposing its emptyness. See the `match_privately_empty` test for details.
+            // FIXME: currently the only way I know of something can be a privately-empty enum is
+            // when the exhaustive_patterns feature flag is not present, so this is only needed for
+            // that case.
+            let is_privately_empty = ctors.is_empty() && !cx.is_uninhabited(pcx.ty);
+            // If the enum is declared as `#[non_exhaustive]`, we treat it as if it had an
+            // additionnal "unknown" constructor.
+            let is_declared_nonexhaustive =
+                def.is_variant_list_non_exhaustive() && !cx.is_local(pcx.ty);
+
+            if is_privately_empty || is_declared_nonexhaustive {
+                // There is no point in enumerating all possible variants, because the user can't
+                // actually match against them themselves. So we return only the fictitious
+                // constructor.
+                // E.g., in an example like:
+                // ```
+                //     let err: io::ErrorKind = ...;
+                //     match err {
+                //         io::ErrorKind::NotFound => {},
+                //     }
+                // ```
+                // we don't want to show every possible IO error, but instead have only `_` as the
+                // witness.
+                vec![NonExhaustive]
+            } else {
+                ctors
+            }
+        }
         ty::Char => {
             vec![
                 // The valid Unicode Scalar Value ranges.
@@ -1175,6 +1205,15 @@ fn all_constructors<'a, 'tcx>(
                 ),
             ]
         }
+        ty::Int(_) | ty::Uint(_)
+            if pcx.ty.is_ptr_sized_integral()
+                && !cx.tcx.features().precise_pointer_size_matching =>
+        {
+            // `usize`/`isize` are not allowed to be matched exhaustively unless the
+            // `precise_pointer_size_matching` feature is enabled. So we treat those types like
+            // `#[non_exhaustive]` enums by returning a special unmatcheable constructor.
+            vec![NonExhaustive]
+        }
         ty::Int(ity) => {
             let bits = Integer::from_attr(&cx.tcx, SignedInt(ity)).size().bits() as u128;
             let min = 1u128 << (bits - 1);
@@ -1193,8 +1232,7 @@ fn all_constructors<'a, 'tcx>(
                 vec![Single]
             }
         }
-    };
-    ctors
+    }
 }
 
 /// An inclusive interval, used for precise integer exhaustiveness checking.
@@ -1592,9 +1630,6 @@ pub fn is_useful<'p, 'a, 'tcx>(
         let all_ctors = all_constructors(cx, pcx);
         debug!("all_ctors = {:#?}", all_ctors);
 
-        let is_privately_empty = all_ctors.is_empty() && !cx.is_uninhabited(pcx.ty);
-        let is_declared_nonexhaustive = cx.is_non_exhaustive_enum(pcx.ty) && !cx.is_local(pcx.ty);
-
         // `missing_ctors` is the set of constructors from the same type as the
         // first column of `matrix` that are matched only by wildcard patterns
         // from the first column.
@@ -1602,38 +1637,15 @@ pub fn is_useful<'p, 'a, 'tcx>(
         // Therefore, if there is some pattern that is unmatched by `matrix`,
         // it will still be unmatched if the first constructor is replaced by
         // any of the constructors in `missing_ctors`
-        //
-        // However, if our scrutinee is *privately* an empty enum, we
-        // must treat it as though it had an "unknown" constructor (in
-        // that case, all other patterns obviously can't be variants)
-        // to avoid exposing its emptyness. See the `match_privately_empty`
-        // test for details.
-        //
-        // FIXME: currently the only way I know of something can
-        // be a privately-empty enum is when the exhaustive_patterns
-        // feature flag is not present, so this is only
-        // needed for that case.
-
-        // Missing constructors are those that are not matched by any
-        // non-wildcard patterns in the current column. To determine if
-        // the set is empty, we can check that `.peek().is_none()`, so
-        // we only fully construct them on-demand, because they're rarely used and can be big.
-        let missing_ctors = MissingConstructors::new(cx.tcx, cx.param_env, all_ctors, used_ctors);
 
-        debug!(
-            "missing_ctors.empty()={:#?} is_privately_empty={:#?} is_declared_nonexhaustive={:#?}",
-            missing_ctors.is_empty(),
-            is_privately_empty,
-            is_declared_nonexhaustive
-        );
+        // Missing constructors are those that are not matched by any non-wildcard patterns in the
+        // current column. We only fully construct them on-demand, because they're rarely used and
+        // can be big.
+        let missing_ctors = MissingConstructors::new(cx.tcx, cx.param_env, all_ctors, used_ctors);
 
-        // For privately empty and non-exhaustive enums, we work as if there were an "extra"
-        // `_` constructor for the type, so we can never match over all constructors.
-        let is_non_exhaustive = is_privately_empty
-            || is_declared_nonexhaustive
-            || (pcx.ty.is_ptr_sized_integral() && !cx.tcx.features().precise_pointer_size_matching);
+        debug!("missing_ctors.empty()={:#?}", missing_ctors.is_empty(),);
 
-        if missing_ctors.is_empty() && !is_non_exhaustive {
+        if missing_ctors.is_empty() {
             let (all_ctors, _) = missing_ctors.into_inner();
             split_grouped_constructors(cx.tcx, cx.param_env, pcx, all_ctors, matrix, DUMMY_SP, None)
                 .into_iter()
@@ -1662,26 +1674,9 @@ pub fn is_useful<'p, 'a, 'tcx>(
             //
             // we can report 3 witnesses: `S`, `E`, and `W`.
             //
-            // However, there are 2 cases where we don't want
+            // However, there is a case where we don't want
             // to do this and instead report a single `_` witness:
-            //
-            // 1) If the user is matching against a non-exhaustive
-            // enum, there is no point in enumerating all possible
-            // variants, because the user can't actually match
-            // against them themselves, e.g., in an example like:
-            // ```
-            //     let err: io::ErrorKind = ...;
-            //     match err {
-            //         io::ErrorKind::NotFound => {},
-            //     }
-            // ```
-            // we don't want to show every possible IO error,
-            // but instead have `_` as the witness (this is
-            // actually *required* if the user specified *all*
-            // IO errors, but is probably what we want in every
-            // case).
-            //
-            // 2) If the user didn't actually specify a constructor
+            // if the user didn't actually specify a constructor
             // in this arm, e.g., in
             // ```
             //     let x: (Direction, Direction, bool) = ...;
@@ -1691,7 +1686,7 @@ pub fn is_useful<'p, 'a, 'tcx>(
             // `(<direction-1>, <direction-2>, true)` - we are
             // satisfied with `(_, _, true)`. In this case,
             // `used_ctors` is empty.
-            if is_non_exhaustive || missing_ctors.all_ctors_are_missing() {
+            if missing_ctors.all_ctors_are_missing() {
                 // All constructors are unused. Add a wild pattern
                 // rather than each individual constructor.
                 usefulness.apply_wildcard(pcx.ty)
@@ -2218,13 +2213,21 @@ fn patterns_for_variant<'p, 'a: 'p, 'tcx>(
 /// fields filled with wild patterns.
 fn specialize_one_pattern<'p, 'a: 'p, 'q: 'p, 'tcx>(
     cx: &mut MatchCheckCtxt<'a, 'tcx>,
-    pat: &'q Pat<'tcx>,
+    mut pat: &'q Pat<'tcx>,
     constructor: &Constructor<'tcx>,
     ctor_wild_subpatterns: &[&'p Pat<'tcx>],
 ) -> Option<PatStack<'p, 'tcx>> {
+    while let PatKind::AscribeUserType { ref subpattern, .. } = *pat.kind {
+        pat = subpattern;
+    }
+
+    if let NonExhaustive = constructor {
+        // Only a wildcard pattern can match the special extra constructor
+        return if pat.is_wildcard() { Some(PatStack::default()) } else { None };
+    }
+
     let result = match *pat.kind {
-        PatKind::AscribeUserType { ref subpattern, .. } => PatStack::from_pattern(subpattern)
-            .specialize_constructor(cx, constructor, ctor_wild_subpatterns),
+        PatKind::AscribeUserType { .. } => bug!(), // Handled above
 
         PatKind::Binding { .. } | PatKind::Wild => {
             Some(PatStack::from_slice(ctor_wild_subpatterns))
diff --git a/src/librustdoc/core.rs b/src/librustdoc/core.rs
index b227f432a4e98..0f508966a4cc2 100644
--- a/src/librustdoc/core.rs
+++ b/src/librustdoc/core.rs
@@ -247,7 +247,7 @@ pub fn run_core(options: RustdocOptions) -> (clean::Crate, RenderInfo, RenderOpt
     } = options;
 
     // Add the rustdoc cfg into the doc build.
-    cfgs.push("rustdoc".to_string());
+    cfgs.push("doc".to_string());
 
     let cpath = Some(input.clone());
     let input = Input::File(input);
@@ -335,6 +335,7 @@ pub fn run_core(options: RustdocOptions) -> (clean::Crate, RenderInfo, RenderOpt
         crate_name,
         lint_caps,
         register_lints: None,
+        override_queries: None,
     };
 
     interface::run_compiler_in_existing_thread_pool(config, |compiler| {
diff --git a/src/librustdoc/test.rs b/src/librustdoc/test.rs
index 553ef6a9c4788..c483f6fb4770f 100644
--- a/src/librustdoc/test.rs
+++ b/src/librustdoc/test.rs
@@ -64,7 +64,7 @@ pub fn run(options: Options) -> i32 {
     };
 
     let mut cfgs = options.cfgs.clone();
-    cfgs.push("rustdoc".to_owned());
+    cfgs.push("doc".to_owned());
     cfgs.push("doctest".to_owned());
     let config = interface::Config {
         opts: sessopts,
@@ -79,6 +79,7 @@ pub fn run(options: Options) -> i32 {
         crate_name: options.crate_name.clone(),
         lint_caps: Default::default(),
         register_lints: None,
+        override_queries: None,
     };
 
     let mut test_args = options.test_args.clone();
diff --git a/src/libstd/io/buffered.rs b/src/libstd/io/buffered.rs
index ad567c97c2c40..557da174d8941 100644
--- a/src/libstd/io/buffered.rs
+++ b/src/libstd/io/buffered.rs
@@ -369,7 +369,7 @@ impl<R: Seek> Seek for BufReader<R> {
 ///
 /// It is critical to call [`flush`] before `BufWriter<W>` is dropped. Though
 /// dropping will attempt to flush the the contents of the buffer, any errors
-/// that happen in the process of dropping will be ignored. Calling ['flush']
+/// that happen in the process of dropping will be ignored. Calling [`flush`]
 /// ensures that the buffer is empty and thus dropping will not even attempt
 /// file operations.
 ///
diff --git a/src/libstd/os/mod.rs b/src/libstd/os/mod.rs
index d44c8ca544e80..a8d2b0cb397ab 100644
--- a/src/libstd/os/mod.rs
+++ b/src/libstd/os/mod.rs
@@ -4,7 +4,7 @@
 #![allow(missing_docs, nonstandard_style, missing_debug_implementations)]
 
 cfg_if::cfg_if! {
-    if #[cfg(rustdoc)] {
+    if #[cfg(doc)] {
 
         // When documenting libstd we want to show unix/windows/linux modules as
         // these are the "main modules" that are used across platforms. This
diff --git a/src/libstd/sys/mod.rs b/src/libstd/sys/mod.rs
index 16b0539cdb9f9..9eeab34643f93 100644
--- a/src/libstd/sys/mod.rs
+++ b/src/libstd/sys/mod.rs
@@ -56,7 +56,7 @@ cfg_if::cfg_if! {
 // then later used in the `std::os` module when documenting, for example,
 // Windows when we're compiling for Linux.
 
-#[cfg(rustdoc)]
+#[cfg(doc)]
 cfg_if::cfg_if! {
     if #[cfg(unix)] {
         // On unix we'll document what's already available
@@ -80,7 +80,7 @@ cfg_if::cfg_if! {
     }
 }
 
-#[cfg(rustdoc)]
+#[cfg(doc)]
 cfg_if::cfg_if! {
     if #[cfg(windows)] {
         // On windows we'll just be documenting what's already available
diff --git a/src/libstd/sys/unix/mod.rs b/src/libstd/sys/unix/mod.rs
index d0bed0f038e6c..bf0166ceb6fbf 100644
--- a/src/libstd/sys/unix/mod.rs
+++ b/src/libstd/sys/unix/mod.rs
@@ -2,21 +2,21 @@
 
 use crate::io::ErrorKind;
 
-#[cfg(any(rustdoc, target_os = "linux"))] pub use crate::os::linux as platform;
-
-#[cfg(all(not(rustdoc), target_os = "android"))]   pub use crate::os::android as platform;
-#[cfg(all(not(rustdoc), target_os = "dragonfly"))] pub use crate::os::dragonfly as platform;
-#[cfg(all(not(rustdoc), target_os = "freebsd"))]   pub use crate::os::freebsd as platform;
-#[cfg(all(not(rustdoc), target_os = "haiku"))]     pub use crate::os::haiku as platform;
-#[cfg(all(not(rustdoc), target_os = "ios"))]       pub use crate::os::ios as platform;
-#[cfg(all(not(rustdoc), target_os = "macos"))]     pub use crate::os::macos as platform;
-#[cfg(all(not(rustdoc), target_os = "netbsd"))]    pub use crate::os::netbsd as platform;
-#[cfg(all(not(rustdoc), target_os = "openbsd"))]   pub use crate::os::openbsd as platform;
-#[cfg(all(not(rustdoc), target_os = "solaris"))]   pub use crate::os::solaris as platform;
-#[cfg(all(not(rustdoc), target_os = "emscripten"))] pub use crate::os::emscripten as platform;
-#[cfg(all(not(rustdoc), target_os = "fuchsia"))]   pub use crate::os::fuchsia as platform;
-#[cfg(all(not(rustdoc), target_os = "l4re"))]      pub use crate::os::linux as platform;
-#[cfg(all(not(rustdoc), target_os = "redox"))]      pub use crate::os::redox as platform;
+#[cfg(any(doc, target_os = "linux"))] pub use crate::os::linux as platform;
+
+#[cfg(all(not(doc), target_os = "android"))]   pub use crate::os::android as platform;
+#[cfg(all(not(doc), target_os = "dragonfly"))] pub use crate::os::dragonfly as platform;
+#[cfg(all(not(doc), target_os = "freebsd"))]   pub use crate::os::freebsd as platform;
+#[cfg(all(not(doc), target_os = "haiku"))]     pub use crate::os::haiku as platform;
+#[cfg(all(not(doc), target_os = "ios"))]       pub use crate::os::ios as platform;
+#[cfg(all(not(doc), target_os = "macos"))]     pub use crate::os::macos as platform;
+#[cfg(all(not(doc), target_os = "netbsd"))]    pub use crate::os::netbsd as platform;
+#[cfg(all(not(doc), target_os = "openbsd"))]   pub use crate::os::openbsd as platform;
+#[cfg(all(not(doc), target_os = "solaris"))]   pub use crate::os::solaris as platform;
+#[cfg(all(not(doc), target_os = "emscripten"))] pub use crate::os::emscripten as platform;
+#[cfg(all(not(doc), target_os = "fuchsia"))]   pub use crate::os::fuchsia as platform;
+#[cfg(all(not(doc), target_os = "l4re"))]      pub use crate::os::linux as platform;
+#[cfg(all(not(doc), target_os = "redox"))]      pub use crate::os::redox as platform;
 
 pub use self::rand::hashmap_random_keys;
 pub use libc::strlen;
diff --git a/src/libstd/sys_common/mod.rs b/src/libstd/sys_common/mod.rs
index 7a0bcd03d758f..8912aed925580 100644
--- a/src/libstd/sys_common/mod.rs
+++ b/src/libstd/sys_common/mod.rs
@@ -45,7 +45,7 @@ pub mod backtrace;
 pub mod condvar;
 pub mod io;
 pub mod mutex;
-#[cfg(any(rustdoc, // see `mod os`, docs are generated for multiple platforms
+#[cfg(any(doc, // see `mod os`, docs are generated for multiple platforms
           unix,
           target_os = "redox",
           target_os = "cloudabi",
diff --git a/src/libsyntax/feature_gate/builtin_attrs.rs b/src/libsyntax/feature_gate/builtin_attrs.rs
index 608cc2a09cbee..555c715771aaa 100644
--- a/src/libsyntax/feature_gate/builtin_attrs.rs
+++ b/src/libsyntax/feature_gate/builtin_attrs.rs
@@ -30,7 +30,7 @@ const GATED_CFGS: &[(Symbol, Symbol, GateFn)] = &[
     (sym::target_thread_local, sym::cfg_target_thread_local, cfg_fn!(cfg_target_thread_local)),
     (sym::target_has_atomic, sym::cfg_target_has_atomic, cfg_fn!(cfg_target_has_atomic)),
     (sym::target_has_atomic_load_store, sym::cfg_target_has_atomic, cfg_fn!(cfg_target_has_atomic)),
-    (sym::rustdoc, sym::doc_cfg, cfg_fn!(doc_cfg)),
+    (sym::doc, sym::doc_cfg, cfg_fn!(doc_cfg)),
 ];
 
 #[derive(Debug)]
diff --git a/src/test/run-make-fulldeps/issue-19371/foo.rs b/src/test/run-make-fulldeps/issue-19371/foo.rs
index 9582137eae91c..9f1850dfb4c90 100644
--- a/src/test/run-make-fulldeps/issue-19371/foo.rs
+++ b/src/test/run-make-fulldeps/issue-19371/foo.rs
@@ -60,6 +60,7 @@ fn compile(code: String, output: PathBuf, sysroot: PathBuf) {
         crate_name: None,
         lint_caps: Default::default(),
         register_lints: None,
+        override_queries: None,
     };
 
     interface::run_compiler(config, |compiler| {
diff --git a/src/test/rustdoc-ui/doc-test-rustdoc-feature.rs b/src/test/rustdoc-ui/doc-test-rustdoc-feature.rs
index d0ead4136575f..62fd3da9233fa 100644
--- a/src/test/rustdoc-ui/doc-test-rustdoc-feature.rs
+++ b/src/test/rustdoc-ui/doc-test-rustdoc-feature.rs
@@ -4,11 +4,11 @@
 
 #![feature(doc_cfg)]
 
-// Make sure `cfg(rustdoc)` is set when finding doctests but not inside the doctests.
+// Make sure `cfg(doc)` is set when finding doctests but not inside the doctests.
 
 /// ```
 /// #![feature(doc_cfg)]
-/// assert!(!cfg!(rustdoc));
+/// assert!(!cfg!(doc));
 /// ```
-#[cfg(rustdoc)]
+#[cfg(doc)]
 pub struct Foo;
diff --git a/src/test/ui/associated-type-bounds/implied-region-constraints.stderr b/src/test/ui/associated-type-bounds/implied-region-constraints.stderr
index 9968f3e8bac5e..60c6e8a80fb6a 100644
--- a/src/test/ui/associated-type-bounds/implied-region-constraints.stderr
+++ b/src/test/ui/associated-type-bounds/implied-region-constraints.stderr
@@ -18,3 +18,4 @@ LL |             let _failure_proves_not_implied_outlives_region_b: &'b T = &x;
 
 error: aborting due to 2 previous errors
 
+For more information about this error, try `rustc --explain E0623`.
diff --git a/src/test/ui/associated-types/associated-types-project-from-hrtb-in-fn-body.stderr b/src/test/ui/associated-types/associated-types-project-from-hrtb-in-fn-body.stderr
index 63d662f44658a..d5310c47fcf1e 100644
--- a/src/test/ui/associated-types/associated-types-project-from-hrtb-in-fn-body.stderr
+++ b/src/test/ui/associated-types/associated-types-project-from-hrtb-in-fn-body.stderr
@@ -11,3 +11,4 @@ LL |     let z: I::A = if cond { x } else { y };
 
 error: aborting due to previous error
 
+For more information about this error, try `rustc --explain E0623`.
diff --git a/src/test/ui/associated-types/associated-types-subtyping-1.stderr b/src/test/ui/associated-types/associated-types-subtyping-1.stderr
index 660e5b3928acf..58ceec9040b9d 100644
--- a/src/test/ui/associated-types/associated-types-subtyping-1.stderr
+++ b/src/test/ui/associated-types/associated-types-subtyping-1.stderr
@@ -18,3 +18,4 @@ LL |     let _c: <T as Trait<'a>>::Type = b;
 
 error: aborting due to 2 previous errors
 
+For more information about this error, try `rustc --explain E0623`.
diff --git a/src/test/ui/associated-types/cache/project-fn-ret-contravariant.krisskross.stderr b/src/test/ui/associated-types/cache/project-fn-ret-contravariant.krisskross.stderr
index dc9a549586bab..fa4c6adb5fff7 100644
--- a/src/test/ui/associated-types/cache/project-fn-ret-contravariant.krisskross.stderr
+++ b/src/test/ui/associated-types/cache/project-fn-ret-contravariant.krisskross.stderr
@@ -22,3 +22,4 @@ LL |    (a, b)
 
 error: aborting due to 2 previous errors
 
+For more information about this error, try `rustc --explain E0623`.
diff --git a/src/test/ui/associated-types/cache/project-fn-ret-invariant.krisskross.stderr b/src/test/ui/associated-types/cache/project-fn-ret-invariant.krisskross.stderr
index 6accf8110ad1e..5009e0868a7d4 100644
--- a/src/test/ui/associated-types/cache/project-fn-ret-invariant.krisskross.stderr
+++ b/src/test/ui/associated-types/cache/project-fn-ret-invariant.krisskross.stderr
@@ -21,3 +21,4 @@ LL |    let b = bar(foo, x);
 
 error: aborting due to 2 previous errors
 
+For more information about this error, try `rustc --explain E0623`.
diff --git a/src/test/ui/associated-types/cache/project-fn-ret-invariant.oneuse.stderr b/src/test/ui/associated-types/cache/project-fn-ret-invariant.oneuse.stderr
index ef036bd8fbaa8..65d16440ac9b0 100644
--- a/src/test/ui/associated-types/cache/project-fn-ret-invariant.oneuse.stderr
+++ b/src/test/ui/associated-types/cache/project-fn-ret-invariant.oneuse.stderr
@@ -11,3 +11,4 @@ LL |    let b = bar(f, y);
 
 error: aborting due to previous error
 
+For more information about this error, try `rustc --explain E0623`.
diff --git a/src/test/ui/async-await/issues/issue-63388-1.stderr b/src/test/ui/async-await/issues/issue-63388-1.stderr
index 2917fa9ccb7f2..8813183312ddf 100644
--- a/src/test/ui/async-await/issues/issue-63388-1.stderr
+++ b/src/test/ui/async-await/issues/issue-63388-1.stderr
@@ -11,3 +11,4 @@ LL |         foo
 
 error: aborting due to previous error
 
+For more information about this error, try `rustc --explain E0623`.
diff --git a/src/test/ui/async-await/multiple-lifetimes/ret-impl-trait-one.stderr b/src/test/ui/async-await/multiple-lifetimes/ret-impl-trait-one.stderr
index f6d611517bc8f..7b8f290d6c2f8 100644
--- a/src/test/ui/async-await/multiple-lifetimes/ret-impl-trait-one.stderr
+++ b/src/test/ui/async-await/multiple-lifetimes/ret-impl-trait-one.stderr
@@ -9,3 +9,4 @@ LL | async fn async_ret_impl_trait1<'a, 'b>(a: &'a u8, b: &'b u8) -> impl Trait<
 
 error: aborting due to previous error
 
+For more information about this error, try `rustc --explain E0623`.
diff --git a/src/test/ui/borrowck/borrowck-reborrow-from-shorter-lived-andmut.stderr b/src/test/ui/borrowck/borrowck-reborrow-from-shorter-lived-andmut.stderr
index 4142fc488c0dd..67b6f64eaa64f 100644
--- a/src/test/ui/borrowck/borrowck-reborrow-from-shorter-lived-andmut.stderr
+++ b/src/test/ui/borrowck/borrowck-reborrow-from-shorter-lived-andmut.stderr
@@ -10,3 +10,4 @@ LL |     S { pointer: &mut *p.pointer }
 
 error: aborting due to previous error
 
+For more information about this error, try `rustc --explain E0623`.
diff --git a/src/test/ui/consts/issue-52432.rs b/src/test/ui/consts/issue-52432.rs
new file mode 100644
index 0000000000000..2d4c939f47d79
--- /dev/null
+++ b/src/test/ui/consts/issue-52432.rs
@@ -0,0 +1,10 @@
+#![feature(const_raw_ptr_to_usize_cast)]
+
+fn main() {
+    [(); &(static |x| {}) as *const _ as usize];
+    //~^ ERROR: closures cannot be static
+    //~| ERROR: type annotations needed
+    [(); &(static || {}) as *const _ as usize];
+    //~^ ERROR: closures cannot be static
+    //~| ERROR: evaluation of constant value failed
+}
diff --git a/src/test/ui/consts/issue-52432.stderr b/src/test/ui/consts/issue-52432.stderr
new file mode 100644
index 0000000000000..e9539d24118a0
--- /dev/null
+++ b/src/test/ui/consts/issue-52432.stderr
@@ -0,0 +1,28 @@
+error[E0697]: closures cannot be static
+  --> $DIR/issue-52432.rs:4:12
+   |
+LL |     [(); &(static |x| {}) as *const _ as usize];
+   |            ^^^^^^^^^^
+
+error[E0697]: closures cannot be static
+  --> $DIR/issue-52432.rs:7:12
+   |
+LL |     [(); &(static || {}) as *const _ as usize];
+   |            ^^^^^^^^^
+
+error[E0282]: type annotations needed
+  --> $DIR/issue-52432.rs:4:20
+   |
+LL |     [(); &(static |x| {}) as *const _ as usize];
+   |                    ^ consider giving this closure parameter a type
+
+error[E0080]: evaluation of constant value failed
+  --> $DIR/issue-52432.rs:7:10
+   |
+LL |     [(); &(static || {}) as *const _ as usize];
+   |          ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ "pointer-to-integer cast" needs an rfc before being allowed inside constants
+
+error: aborting due to 4 previous errors
+
+Some errors have detailed explanations: E0080, E0282, E0697.
+For more information about an error, try `rustc --explain E0080`.
diff --git a/src/test/ui/continue-after-missing-main.stderr b/src/test/ui/continue-after-missing-main.stderr
index 64d34cb6a1947..439f9e5221f66 100644
--- a/src/test/ui/continue-after-missing-main.stderr
+++ b/src/test/ui/continue-after-missing-main.stderr
@@ -21,4 +21,5 @@ LL |     let _: AdaptedMatrixProvider<'original_data, MP> = tableau.provider().c
 
 error: aborting due to 2 previous errors
 
-For more information about this error, try `rustc --explain E0601`.
+Some errors have detailed explanations: E0601, E0623.
+For more information about an error, try `rustc --explain E0601`.
diff --git a/src/test/ui/feature-gates/feature-gate-doc_cfg-cfg-rustdoc.rs b/src/test/ui/feature-gates/feature-gate-doc_cfg-cfg-rustdoc.rs
index 17ea58231915d..9830503a8cac6 100644
--- a/src/test/ui/feature-gates/feature-gate-doc_cfg-cfg-rustdoc.rs
+++ b/src/test/ui/feature-gates/feature-gate-doc_cfg-cfg-rustdoc.rs
@@ -1,4 +1,4 @@
-#[cfg(rustdoc)] //~ ERROR: `cfg(rustdoc)` is experimental and subject to change
+#[cfg(doc)] //~ ERROR: `cfg(doc)` is experimental and subject to change
 pub struct SomeStruct;
 
 fn main() {}
diff --git a/src/test/ui/feature-gates/feature-gate-doc_cfg-cfg-rustdoc.stderr b/src/test/ui/feature-gates/feature-gate-doc_cfg-cfg-rustdoc.stderr
index 9bf97a4a4771c..26a1f4decf4cf 100644
--- a/src/test/ui/feature-gates/feature-gate-doc_cfg-cfg-rustdoc.stderr
+++ b/src/test/ui/feature-gates/feature-gate-doc_cfg-cfg-rustdoc.stderr
@@ -1,8 +1,8 @@
-error[E0658]: `cfg(rustdoc)` is experimental and subject to change
+error[E0658]: `cfg(doc)` is experimental and subject to change
   --> $DIR/feature-gate-doc_cfg-cfg-rustdoc.rs:1:7
    |
-LL | #[cfg(rustdoc)]
-   |       ^^^^^^^
+LL | #[cfg(doc)]
+   |       ^^^
    |
    = note: for more information, see https://github.com/rust-lang/rust/issues/43781
    = help: add `#![feature(doc_cfg)]` to the crate attributes to enable
diff --git a/src/test/ui/impl-trait/must_outlive_least_region_or_bound.stderr b/src/test/ui/impl-trait/must_outlive_least_region_or_bound.stderr
index 2ffb94348616b..a8341f62e1d14 100644
--- a/src/test/ui/impl-trait/must_outlive_least_region_or_bound.stderr
+++ b/src/test/ui/impl-trait/must_outlive_least_region_or_bound.stderr
@@ -77,4 +77,5 @@ LL | fn ty_param_wont_outlive_static<T:Debug>(x: T) -> impl Debug + 'static {
 
 error: aborting due to 5 previous errors
 
-For more information about this error, try `rustc --explain E0310`.
+Some errors have detailed explanations: E0310, E0623.
+For more information about an error, try `rustc --explain E0310`.
diff --git a/src/test/ui/in-band-lifetimes/mismatched.stderr b/src/test/ui/in-band-lifetimes/mismatched.stderr
index ec1045d5fae37..db72c20697108 100644
--- a/src/test/ui/in-band-lifetimes/mismatched.stderr
+++ b/src/test/ui/in-band-lifetimes/mismatched.stderr
@@ -16,4 +16,5 @@ LL | fn foo2(x: &'a u32, y: &'b u32) -> &'a u32 { y }
 
 error: aborting due to 2 previous errors
 
-For more information about this error, try `rustc --explain E0621`.
+Some errors have detailed explanations: E0621, E0623.
+For more information about an error, try `rustc --explain E0621`.
diff --git a/src/test/ui/in-band-lifetimes/mismatched_trait_impl.stderr b/src/test/ui/in-band-lifetimes/mismatched_trait_impl.stderr
index bc302e91c1c51..15891c9e7a62d 100644
--- a/src/test/ui/in-band-lifetimes/mismatched_trait_impl.stderr
+++ b/src/test/ui/in-band-lifetimes/mismatched_trait_impl.stderr
@@ -22,3 +22,4 @@ LL |         x
 
 error: aborting due to 2 previous errors
 
+For more information about this error, try `rustc --explain E0623`.
diff --git a/src/test/ui/issues/issue-17728.stderr b/src/test/ui/issues/issue-17728.stderr
index 56dfb89456fe5..945dfc26b206d 100644
--- a/src/test/ui/issues/issue-17728.stderr
+++ b/src/test/ui/issues/issue-17728.stderr
@@ -29,4 +29,5 @@ LL | |     }
 
 error: aborting due to 2 previous errors
 
-For more information about this error, try `rustc --explain E0308`.
+Some errors have detailed explanations: E0308, E0623.
+For more information about an error, try `rustc --explain E0308`.
diff --git a/src/test/ui/issues/issue-40231-1.rs b/src/test/ui/issues/issue-40231-1.rs
new file mode 100644
index 0000000000000..999399ec8d34c
--- /dev/null
+++ b/src/test/ui/issues/issue-40231-1.rs
@@ -0,0 +1,54 @@
+// check-pass
+
+#![allow(dead_code)]
+
+trait Structure<E>: Sized where E: Encoding {
+    type RefTarget: ?Sized;
+    type FfiPtr;
+    unsafe fn borrow_from_ffi_ptr<'a>(ptr: Self::FfiPtr) -> Option<&'a Self::RefTarget>;
+}
+
+enum Slice {}
+
+impl<E> Structure<E> for Slice where E: Encoding {
+    type RefTarget = [E::Unit];
+    type FfiPtr = (*const E::FfiUnit, usize);
+    unsafe fn borrow_from_ffi_ptr<'a>(_ptr: Self::FfiPtr) -> Option<&'a Self::RefTarget> {
+        panic!()
+    }
+}
+
+trait Encoding {
+    type Unit: Unit;
+    type FfiUnit;
+}
+
+trait Unit {}
+
+enum Utf16 {}
+
+impl Encoding for Utf16 {
+    type Unit = Utf16Unit;
+    type FfiUnit = u16;
+}
+
+struct Utf16Unit(pub u16);
+
+impl Unit for Utf16Unit {}
+
+type SUtf16Str = SeStr<Slice, Utf16>;
+
+struct SeStr<S, E> where S: Structure<E>, E: Encoding {
+    _data: S::RefTarget,
+}
+
+impl<S, E> SeStr<S, E> where S: Structure<E>, E: Encoding {
+    pub unsafe fn from_ptr<'a>(_ptr: S::FfiPtr) -> Option<&'a Self> {
+        panic!()
+    }
+}
+
+fn main() {
+    const TEXT_U16: &'static [u16] = &[];
+    let _ = unsafe { SUtf16Str::from_ptr((TEXT_U16.as_ptr(), TEXT_U16.len())).unwrap() };
+}
diff --git a/src/test/ui/issues/issue-40231-2.rs b/src/test/ui/issues/issue-40231-2.rs
new file mode 100644
index 0000000000000..780433b28c596
--- /dev/null
+++ b/src/test/ui/issues/issue-40231-2.rs
@@ -0,0 +1,54 @@
+// check-pass
+
+#![allow(dead_code)]
+
+trait Structure<E>: Sized where E: Encoding {
+    type RefTarget: ?Sized;
+    type FfiPtr;
+    unsafe fn borrow_from_ffi_ptr<'a>(ptr: Self::FfiPtr) -> Option<&'a Self::RefTarget>;
+}
+
+enum Slice {}
+
+impl<E> Structure<E> for Slice where E: Encoding {
+    type RefTarget = [E::Unit];
+    type FfiPtr = (*const E::FfiUnit, usize);
+    unsafe fn borrow_from_ffi_ptr<'a>(_ptr: Self::FfiPtr) -> Option<&'a Self::RefTarget> {
+        panic!()
+    }
+}
+
+trait Encoding {
+    type Unit: Unit;
+    type FfiUnit;
+}
+
+trait Unit {}
+
+enum Utf16 {}
+
+impl Encoding for Utf16 {
+    type Unit = Utf16Unit;
+    type FfiUnit = u16;
+}
+
+struct Utf16Unit(pub u16);
+
+impl Unit for Utf16Unit {}
+
+struct SUtf16Str {
+    _data: <Slice as Structure<Utf16>>::RefTarget,
+}
+
+impl SUtf16Str {
+    pub unsafe fn from_ptr<'a>(ptr: <Slice as Structure<Utf16>>::FfiPtr)
+    -> Option<&'a Self> {
+        std::mem::transmute::<Option<&[<Utf16 as Encoding>::Unit]>, _>(
+            <Slice as Structure<Utf16>>::borrow_from_ffi_ptr(ptr))
+    }
+}
+
+fn main() {
+    const TEXT_U16: &'static [u16] = &[];
+    let _ = unsafe { SUtf16Str::from_ptr((TEXT_U16.as_ptr(), TEXT_U16.len())).unwrap() };
+}
diff --git a/src/test/ui/lifetimes/lifetime-errors/ex1-return-one-existing-name-if-else-using-impl.stderr b/src/test/ui/lifetimes/lifetime-errors/ex1-return-one-existing-name-if-else-using-impl.stderr
index 56ca610019c4c..e9f5fc311dfc2 100644
--- a/src/test/ui/lifetimes/lifetime-errors/ex1-return-one-existing-name-if-else-using-impl.stderr
+++ b/src/test/ui/lifetimes/lifetime-errors/ex1-return-one-existing-name-if-else-using-impl.stderr
@@ -11,3 +11,4 @@ LL |         if x > y { x } else { y }
 
 error: aborting due to previous error
 
+For more information about this error, try `rustc --explain E0623`.
diff --git a/src/test/ui/lifetimes/lifetime-errors/ex1-return-one-existing-name-return-type-is-anon.stderr b/src/test/ui/lifetimes/lifetime-errors/ex1-return-one-existing-name-return-type-is-anon.stderr
index df34d18ee83a4..0d506f2b9fcb4 100644
--- a/src/test/ui/lifetimes/lifetime-errors/ex1-return-one-existing-name-return-type-is-anon.stderr
+++ b/src/test/ui/lifetimes/lifetime-errors/ex1-return-one-existing-name-return-type-is-anon.stderr
@@ -11,3 +11,4 @@ LL |     x
 
 error: aborting due to previous error
 
+For more information about this error, try `rustc --explain E0623`.
diff --git a/src/test/ui/lifetimes/lifetime-errors/ex1-return-one-existing-name-self-is-anon.stderr b/src/test/ui/lifetimes/lifetime-errors/ex1-return-one-existing-name-self-is-anon.stderr
index 22e14df9edc03..98a23613c3635 100644
--- a/src/test/ui/lifetimes/lifetime-errors/ex1-return-one-existing-name-self-is-anon.stderr
+++ b/src/test/ui/lifetimes/lifetime-errors/ex1-return-one-existing-name-self-is-anon.stderr
@@ -11,3 +11,4 @@ LL |         if true { x } else { self }
 
 error: aborting due to previous error
 
+For more information about this error, try `rustc --explain E0623`.
diff --git a/src/test/ui/lifetimes/lifetime-errors/ex2b-push-no-existing-names.stderr b/src/test/ui/lifetimes/lifetime-errors/ex2b-push-no-existing-names.stderr
index c0c75c7453d24..e505c9c0dc262 100644
--- a/src/test/ui/lifetimes/lifetime-errors/ex2b-push-no-existing-names.stderr
+++ b/src/test/ui/lifetimes/lifetime-errors/ex2b-push-no-existing-names.stderr
@@ -8,3 +8,4 @@ LL |     x.push(y);
 
 error: aborting due to previous error
 
+For more information about this error, try `rustc --explain E0623`.
diff --git a/src/test/ui/lifetimes/lifetime-errors/ex2c-push-inference-variable.stderr b/src/test/ui/lifetimes/lifetime-errors/ex2c-push-inference-variable.stderr
index 57101cffe9b92..63b1c6db28f14 100644
--- a/src/test/ui/lifetimes/lifetime-errors/ex2c-push-inference-variable.stderr
+++ b/src/test/ui/lifetimes/lifetime-errors/ex2c-push-inference-variable.stderr
@@ -9,3 +9,4 @@ LL |     x.push(z);
 
 error: aborting due to previous error
 
+For more information about this error, try `rustc --explain E0623`.
diff --git a/src/test/ui/lifetimes/lifetime-errors/ex2d-push-inference-variable-2.stderr b/src/test/ui/lifetimes/lifetime-errors/ex2d-push-inference-variable-2.stderr
index cab30636280a9..2f669efcf1eb4 100644
--- a/src/test/ui/lifetimes/lifetime-errors/ex2d-push-inference-variable-2.stderr
+++ b/src/test/ui/lifetimes/lifetime-errors/ex2d-push-inference-variable-2.stderr
@@ -8,3 +8,4 @@ LL |     let a: &mut Vec<Ref<i32>> = x;
 
 error: aborting due to previous error
 
+For more information about this error, try `rustc --explain E0623`.
diff --git a/src/test/ui/lifetimes/lifetime-errors/ex2e-push-inference-variable-3.stderr b/src/test/ui/lifetimes/lifetime-errors/ex2e-push-inference-variable-3.stderr
index 384caca824892..258b6805acd5c 100644
--- a/src/test/ui/lifetimes/lifetime-errors/ex2e-push-inference-variable-3.stderr
+++ b/src/test/ui/lifetimes/lifetime-errors/ex2e-push-inference-variable-3.stderr
@@ -8,3 +8,4 @@ LL |     let a: &mut Vec<Ref<i32>> = x;
 
 error: aborting due to previous error
 
+For more information about this error, try `rustc --explain E0623`.
diff --git a/src/test/ui/lifetimes/lifetime-errors/ex3-both-anon-regions-2.stderr b/src/test/ui/lifetimes/lifetime-errors/ex3-both-anon-regions-2.stderr
index 9251c5e2446f3..0aff80c6fbdd3 100644
--- a/src/test/ui/lifetimes/lifetime-errors/ex3-both-anon-regions-2.stderr
+++ b/src/test/ui/lifetimes/lifetime-errors/ex3-both-anon-regions-2.stderr
@@ -8,3 +8,4 @@ LL |     *v = x;
 
 error: aborting due to previous error
 
+For more information about this error, try `rustc --explain E0623`.
diff --git a/src/test/ui/lifetimes/lifetime-errors/ex3-both-anon-regions-3.stderr b/src/test/ui/lifetimes/lifetime-errors/ex3-both-anon-regions-3.stderr
index adda66899cbf0..2e5ff6782d3b6 100644
--- a/src/test/ui/lifetimes/lifetime-errors/ex3-both-anon-regions-3.stderr
+++ b/src/test/ui/lifetimes/lifetime-errors/ex3-both-anon-regions-3.stderr
@@ -16,3 +16,4 @@ LL |     z.push((x,y));
 
 error: aborting due to 2 previous errors
 
+For more information about this error, try `rustc --explain E0623`.
diff --git a/src/test/ui/lifetimes/lifetime-errors/ex3-both-anon-regions-both-are-structs-2.stderr b/src/test/ui/lifetimes/lifetime-errors/ex3-both-anon-regions-both-are-structs-2.stderr
index 4341e8e663e19..8e41d7c54e68d 100644
--- a/src/test/ui/lifetimes/lifetime-errors/ex3-both-anon-regions-both-are-structs-2.stderr
+++ b/src/test/ui/lifetimes/lifetime-errors/ex3-both-anon-regions-both-are-structs-2.stderr
@@ -8,3 +8,4 @@ LL |     x.b = y.b;
 
 error: aborting due to previous error
 
+For more information about this error, try `rustc --explain E0623`.
diff --git a/src/test/ui/lifetimes/lifetime-errors/ex3-both-anon-regions-both-are-structs-3.stderr b/src/test/ui/lifetimes/lifetime-errors/ex3-both-anon-regions-both-are-structs-3.stderr
index b49ee0cfc7033..d659c88f69ef7 100644
--- a/src/test/ui/lifetimes/lifetime-errors/ex3-both-anon-regions-both-are-structs-3.stderr
+++ b/src/test/ui/lifetimes/lifetime-errors/ex3-both-anon-regions-both-are-structs-3.stderr
@@ -8,3 +8,4 @@ LL |     x.a = x.b;
 
 error: aborting due to previous error
 
+For more information about this error, try `rustc --explain E0623`.
diff --git a/src/test/ui/lifetimes/lifetime-errors/ex3-both-anon-regions-both-are-structs-earlybound-regions.stderr b/src/test/ui/lifetimes/lifetime-errors/ex3-both-anon-regions-both-are-structs-earlybound-regions.stderr
index a13c7e63cd6d9..374bbd93d0874 100644
--- a/src/test/ui/lifetimes/lifetime-errors/ex3-both-anon-regions-both-are-structs-earlybound-regions.stderr
+++ b/src/test/ui/lifetimes/lifetime-errors/ex3-both-anon-regions-both-are-structs-earlybound-regions.stderr
@@ -9,3 +9,4 @@ LL |     x.push(y);
 
 error: aborting due to previous error
 
+For more information about this error, try `rustc --explain E0623`.
diff --git a/src/test/ui/lifetimes/lifetime-errors/ex3-both-anon-regions-both-are-structs-latebound-regions.stderr b/src/test/ui/lifetimes/lifetime-errors/ex3-both-anon-regions-both-are-structs-latebound-regions.stderr
index 14faf6f460f52..94798d1ce2ab6 100644
--- a/src/test/ui/lifetimes/lifetime-errors/ex3-both-anon-regions-both-are-structs-latebound-regions.stderr
+++ b/src/test/ui/lifetimes/lifetime-errors/ex3-both-anon-regions-both-are-structs-latebound-regions.stderr
@@ -8,3 +8,4 @@ LL |     x.push(y);
 
 error: aborting due to previous error
 
+For more information about this error, try `rustc --explain E0623`.
diff --git a/src/test/ui/lifetimes/lifetime-errors/ex3-both-anon-regions-both-are-structs.stderr b/src/test/ui/lifetimes/lifetime-errors/ex3-both-anon-regions-both-are-structs.stderr
index e5696b74da9ec..9f5a79ed333dc 100644
--- a/src/test/ui/lifetimes/lifetime-errors/ex3-both-anon-regions-both-are-structs.stderr
+++ b/src/test/ui/lifetimes/lifetime-errors/ex3-both-anon-regions-both-are-structs.stderr
@@ -8,3 +8,4 @@ LL |     x.push(y);
 
 error: aborting due to previous error
 
+For more information about this error, try `rustc --explain E0623`.
diff --git a/src/test/ui/lifetimes/lifetime-errors/ex3-both-anon-regions-latebound-regions.stderr b/src/test/ui/lifetimes/lifetime-errors/ex3-both-anon-regions-latebound-regions.stderr
index bbf5d2452bfb9..2c87f8dbd2c2b 100644
--- a/src/test/ui/lifetimes/lifetime-errors/ex3-both-anon-regions-latebound-regions.stderr
+++ b/src/test/ui/lifetimes/lifetime-errors/ex3-both-anon-regions-latebound-regions.stderr
@@ -8,3 +8,4 @@ LL |     x.push(y);
 
 error: aborting due to previous error
 
+For more information about this error, try `rustc --explain E0623`.
diff --git a/src/test/ui/lifetimes/lifetime-errors/ex3-both-anon-regions-one-is-struct-2.stderr b/src/test/ui/lifetimes/lifetime-errors/ex3-both-anon-regions-one-is-struct-2.stderr
index f1bc1ca3aab01..60b92ed2b3247 100644
--- a/src/test/ui/lifetimes/lifetime-errors/ex3-both-anon-regions-one-is-struct-2.stderr
+++ b/src/test/ui/lifetimes/lifetime-errors/ex3-both-anon-regions-one-is-struct-2.stderr
@@ -10,3 +10,4 @@ LL |     y = x.b;
 
 error: aborting due to previous error
 
+For more information about this error, try `rustc --explain E0623`.
diff --git a/src/test/ui/lifetimes/lifetime-errors/ex3-both-anon-regions-one-is-struct-3.stderr b/src/test/ui/lifetimes/lifetime-errors/ex3-both-anon-regions-one-is-struct-3.stderr
index d8f6b8c49d30d..a220c8ddb2be6 100644
--- a/src/test/ui/lifetimes/lifetime-errors/ex3-both-anon-regions-one-is-struct-3.stderr
+++ b/src/test/ui/lifetimes/lifetime-errors/ex3-both-anon-regions-one-is-struct-3.stderr
@@ -8,3 +8,4 @@ LL |     y.b = x;
 
 error: aborting due to previous error
 
+For more information about this error, try `rustc --explain E0623`.
diff --git a/src/test/ui/lifetimes/lifetime-errors/ex3-both-anon-regions-one-is-struct-4.stderr b/src/test/ui/lifetimes/lifetime-errors/ex3-both-anon-regions-one-is-struct-4.stderr
index 08ae2c9db52e7..73472a8d02252 100644
--- a/src/test/ui/lifetimes/lifetime-errors/ex3-both-anon-regions-one-is-struct-4.stderr
+++ b/src/test/ui/lifetimes/lifetime-errors/ex3-both-anon-regions-one-is-struct-4.stderr
@@ -8,3 +8,4 @@ LL |     y.b = x;
 
 error: aborting due to previous error
 
+For more information about this error, try `rustc --explain E0623`.
diff --git a/src/test/ui/lifetimes/lifetime-errors/ex3-both-anon-regions-one-is-struct.stderr b/src/test/ui/lifetimes/lifetime-errors/ex3-both-anon-regions-one-is-struct.stderr
index ff286d722aacd..eb6e6f2e95e78 100644
--- a/src/test/ui/lifetimes/lifetime-errors/ex3-both-anon-regions-one-is-struct.stderr
+++ b/src/test/ui/lifetimes/lifetime-errors/ex3-both-anon-regions-one-is-struct.stderr
@@ -8,3 +8,4 @@ LL |     x.b = y;
 
 error: aborting due to previous error
 
+For more information about this error, try `rustc --explain E0623`.
diff --git a/src/test/ui/lifetimes/lifetime-errors/ex3-both-anon-regions-return-type-is-anon.stderr b/src/test/ui/lifetimes/lifetime-errors/ex3-both-anon-regions-return-type-is-anon.stderr
index 3d16c26568353..199f880b3c487 100644
--- a/src/test/ui/lifetimes/lifetime-errors/ex3-both-anon-regions-return-type-is-anon.stderr
+++ b/src/test/ui/lifetimes/lifetime-errors/ex3-both-anon-regions-return-type-is-anon.stderr
@@ -10,3 +10,4 @@ LL |     x
 
 error: aborting due to previous error
 
+For more information about this error, try `rustc --explain E0623`.
diff --git a/src/test/ui/lifetimes/lifetime-errors/ex3-both-anon-regions-self-is-anon.stderr b/src/test/ui/lifetimes/lifetime-errors/ex3-both-anon-regions-self-is-anon.stderr
index 10872d31ef206..838f43b37747f 100644
--- a/src/test/ui/lifetimes/lifetime-errors/ex3-both-anon-regions-self-is-anon.stderr
+++ b/src/test/ui/lifetimes/lifetime-errors/ex3-both-anon-regions-self-is-anon.stderr
@@ -10,3 +10,4 @@ LL |         if true { x } else { self }
 
 error: aborting due to previous error
 
+For more information about this error, try `rustc --explain E0623`.
diff --git a/src/test/ui/lifetimes/lifetime-errors/ex3-both-anon-regions-using-fn-items.stderr b/src/test/ui/lifetimes/lifetime-errors/ex3-both-anon-regions-using-fn-items.stderr
index 99e6e8bc5aa9b..d2cc3dba6a433 100644
--- a/src/test/ui/lifetimes/lifetime-errors/ex3-both-anon-regions-using-fn-items.stderr
+++ b/src/test/ui/lifetimes/lifetime-errors/ex3-both-anon-regions-using-fn-items.stderr
@@ -8,3 +8,4 @@ LL |   y.push(z);
 
 error: aborting due to previous error
 
+For more information about this error, try `rustc --explain E0623`.
diff --git a/src/test/ui/lifetimes/lifetime-errors/ex3-both-anon-regions-using-impl-items.stderr b/src/test/ui/lifetimes/lifetime-errors/ex3-both-anon-regions-using-impl-items.stderr
index 8ac221e333ad7..e8b0208f092f7 100644
--- a/src/test/ui/lifetimes/lifetime-errors/ex3-both-anon-regions-using-impl-items.stderr
+++ b/src/test/ui/lifetimes/lifetime-errors/ex3-both-anon-regions-using-impl-items.stderr
@@ -8,3 +8,4 @@ LL |         x.push(y);
 
 error: aborting due to previous error
 
+For more information about this error, try `rustc --explain E0623`.
diff --git a/src/test/ui/lifetimes/lifetime-errors/ex3-both-anon-regions-using-trait-objects.stderr b/src/test/ui/lifetimes/lifetime-errors/ex3-both-anon-regions-using-trait-objects.stderr
index bfecb4d33931b..2acc4eaf60f55 100644
--- a/src/test/ui/lifetimes/lifetime-errors/ex3-both-anon-regions-using-trait-objects.stderr
+++ b/src/test/ui/lifetimes/lifetime-errors/ex3-both-anon-regions-using-trait-objects.stderr
@@ -8,3 +8,4 @@ LL |   y.push(z);
 
 error: aborting due to previous error
 
+For more information about this error, try `rustc --explain E0623`.
diff --git a/src/test/ui/lifetimes/lifetime-errors/ex3-both-anon-regions.stderr b/src/test/ui/lifetimes/lifetime-errors/ex3-both-anon-regions.stderr
index 053d577fa01ed..b2784827672b8 100644
--- a/src/test/ui/lifetimes/lifetime-errors/ex3-both-anon-regions.stderr
+++ b/src/test/ui/lifetimes/lifetime-errors/ex3-both-anon-regions.stderr
@@ -8,3 +8,4 @@ LL |     x.push(y);
 
 error: aborting due to previous error
 
+For more information about this error, try `rustc --explain E0623`.
diff --git a/src/test/ui/object-lifetime/object-lifetime-default-mybox.stderr b/src/test/ui/object-lifetime/object-lifetime-default-mybox.stderr
index f825475b96b03..89579fb1df3df 100644
--- a/src/test/ui/object-lifetime/object-lifetime-default-mybox.stderr
+++ b/src/test/ui/object-lifetime/object-lifetime-default-mybox.stderr
@@ -27,4 +27,5 @@ LL | fn load2<'a>(ss: &MyBox<dyn SomeTrait + 'a>) -> MyBox<dyn SomeTrait + 'a> {
 
 error: aborting due to 2 previous errors
 
-For more information about this error, try `rustc --explain E0308`.
+Some errors have detailed explanations: E0308, E0623.
+For more information about an error, try `rustc --explain E0308`.
diff --git a/src/test/ui/regions/region-lifetime-bounds-on-fns-where-clause.stderr b/src/test/ui/regions/region-lifetime-bounds-on-fns-where-clause.stderr
index fd78f82d0f321..36c66451cfaf6 100644
--- a/src/test/ui/regions/region-lifetime-bounds-on-fns-where-clause.stderr
+++ b/src/test/ui/regions/region-lifetime-bounds-on-fns-where-clause.stderr
@@ -27,4 +27,5 @@ LL |     let _: fn(&mut &isize, &mut &isize) = a;
 
 error: aborting due to 3 previous errors
 
-For more information about this error, try `rustc --explain E0308`.
+Some errors have detailed explanations: E0308, E0623.
+For more information about an error, try `rustc --explain E0308`.
diff --git a/src/test/ui/regions/region-multiple-lifetime-bounds-on-fns-where-clause.stderr b/src/test/ui/regions/region-multiple-lifetime-bounds-on-fns-where-clause.stderr
index 220c5493d19b1..a366bd2e5c2d7 100644
--- a/src/test/ui/regions/region-multiple-lifetime-bounds-on-fns-where-clause.stderr
+++ b/src/test/ui/regions/region-multiple-lifetime-bounds-on-fns-where-clause.stderr
@@ -38,4 +38,5 @@ LL |     let _: fn(&mut &isize, &mut &isize, &mut &isize) = a;
 
 error: aborting due to 4 previous errors
 
-For more information about this error, try `rustc --explain E0308`.
+Some errors have detailed explanations: E0308, E0623.
+For more information about an error, try `rustc --explain E0308`.
diff --git a/src/test/ui/regions/regions-bounded-method-type-parameters-cross-crate.stderr b/src/test/ui/regions/regions-bounded-method-type-parameters-cross-crate.stderr
index 4e88be1c1e8a8..eb205a303dbdf 100644
--- a/src/test/ui/regions/regions-bounded-method-type-parameters-cross-crate.stderr
+++ b/src/test/ui/regions/regions-bounded-method-type-parameters-cross-crate.stderr
@@ -9,3 +9,4 @@ LL |     a.bigger_region(b)
 
 error: aborting due to previous error
 
+For more information about this error, try `rustc --explain E0623`.
diff --git a/src/test/ui/regions/regions-bounded-method-type-parameters-trait-bound.stderr b/src/test/ui/regions/regions-bounded-method-type-parameters-trait-bound.stderr
index 6b1302b539402..de1073cd1d9da 100644
--- a/src/test/ui/regions/regions-bounded-method-type-parameters-trait-bound.stderr
+++ b/src/test/ui/regions/regions-bounded-method-type-parameters-trait-bound.stderr
@@ -9,3 +9,4 @@ LL |     f.method(b);
 
 error: aborting due to previous error
 
+For more information about this error, try `rustc --explain E0623`.
diff --git a/src/test/ui/regions/regions-creating-enums3.stderr b/src/test/ui/regions/regions-creating-enums3.stderr
index 763b62d945df8..2fc1fc3f68128 100644
--- a/src/test/ui/regions/regions-creating-enums3.stderr
+++ b/src/test/ui/regions/regions-creating-enums3.stderr
@@ -10,3 +10,4 @@ LL |     Ast::Add(x, y)
 
 error: aborting due to previous error
 
+For more information about this error, try `rustc --explain E0623`.
diff --git a/src/test/ui/regions/regions-free-region-ordering-callee.stderr b/src/test/ui/regions/regions-free-region-ordering-callee.stderr
index 49cf1dfc642da..4648bf046bc77 100644
--- a/src/test/ui/regions/regions-free-region-ordering-callee.stderr
+++ b/src/test/ui/regions/regions-free-region-ordering-callee.stderr
@@ -22,3 +22,4 @@ LL |     let z: &'b usize = &*x;
 
 error: aborting due to 2 previous errors
 
+For more information about this error, try `rustc --explain E0623`.
diff --git a/src/test/ui/regions/regions-free-region-ordering-caller.migrate.stderr b/src/test/ui/regions/regions-free-region-ordering-caller.migrate.stderr
index 9d6bae79ce5d8..a33d3583552dc 100644
--- a/src/test/ui/regions/regions-free-region-ordering-caller.migrate.stderr
+++ b/src/test/ui/regions/regions-free-region-ordering-caller.migrate.stderr
@@ -29,3 +29,4 @@ LL |     let z: Option<&'a &'b usize> = None;
 
 error: aborting due to 3 previous errors
 
+For more information about this error, try `rustc --explain E0623`.
diff --git a/src/test/ui/regions/regions-infer-contravariance-due-to-decl.stderr b/src/test/ui/regions/regions-infer-contravariance-due-to-decl.stderr
index 9374818960d36..f3a0358b90fb0 100644
--- a/src/test/ui/regions/regions-infer-contravariance-due-to-decl.stderr
+++ b/src/test/ui/regions/regions-infer-contravariance-due-to-decl.stderr
@@ -12,3 +12,4 @@ LL |     let _: Contravariant<'long> = c;
 
 error: aborting due to previous error
 
+For more information about this error, try `rustc --explain E0623`.
diff --git a/src/test/ui/regions/regions-infer-covariance-due-to-decl.stderr b/src/test/ui/regions/regions-infer-covariance-due-to-decl.stderr
index cd0a18a892f20..c3e2075fbc37e 100644
--- a/src/test/ui/regions/regions-infer-covariance-due-to-decl.stderr
+++ b/src/test/ui/regions/regions-infer-covariance-due-to-decl.stderr
@@ -11,3 +11,4 @@ LL |     let _: Covariant<'short> = c;
 
 error: aborting due to previous error
 
+For more information about this error, try `rustc --explain E0623`.
diff --git a/src/test/ui/regions/regions-lifetime-bounds-on-fns.stderr b/src/test/ui/regions/regions-lifetime-bounds-on-fns.stderr
index 0c3c342728c01..e260fccf8488c 100644
--- a/src/test/ui/regions/regions-lifetime-bounds-on-fns.stderr
+++ b/src/test/ui/regions/regions-lifetime-bounds-on-fns.stderr
@@ -27,4 +27,5 @@ LL |     let _: fn(&mut &isize, &mut &isize) = a;
 
 error: aborting due to 3 previous errors
 
-For more information about this error, try `rustc --explain E0308`.
+Some errors have detailed explanations: E0308, E0623.
+For more information about an error, try `rustc --explain E0308`.
diff --git a/src/test/ui/regions/regions-reborrow-from-shorter-mut-ref-mut-ref.stderr b/src/test/ui/regions/regions-reborrow-from-shorter-mut-ref-mut-ref.stderr
index ead448df930fe..aca3a1ed05728 100644
--- a/src/test/ui/regions/regions-reborrow-from-shorter-mut-ref-mut-ref.stderr
+++ b/src/test/ui/regions/regions-reborrow-from-shorter-mut-ref-mut-ref.stderr
@@ -10,3 +10,4 @@ LL |     &mut ***p
 
 error: aborting due to previous error
 
+For more information about this error, try `rustc --explain E0623`.
diff --git a/src/test/ui/regions/regions-reborrow-from-shorter-mut-ref.stderr b/src/test/ui/regions/regions-reborrow-from-shorter-mut-ref.stderr
index 064e89ee001c1..a9916dbe4f5ef 100644
--- a/src/test/ui/regions/regions-reborrow-from-shorter-mut-ref.stderr
+++ b/src/test/ui/regions/regions-reborrow-from-shorter-mut-ref.stderr
@@ -10,3 +10,4 @@ LL |     &mut **p
 
 error: aborting due to previous error
 
+For more information about this error, try `rustc --explain E0623`.
diff --git a/src/test/ui/regions/regions-variance-contravariant-use-covariant-in-second-position.stderr b/src/test/ui/regions/regions-variance-contravariant-use-covariant-in-second-position.stderr
index 6b3a488805f97..98f7a8136da91 100644
--- a/src/test/ui/regions/regions-variance-contravariant-use-covariant-in-second-position.stderr
+++ b/src/test/ui/regions/regions-variance-contravariant-use-covariant-in-second-position.stderr
@@ -9,3 +9,4 @@ LL |     let _: S<'long, 'long> = c;
 
 error: aborting due to previous error
 
+For more information about this error, try `rustc --explain E0623`.
diff --git a/src/test/ui/regions/regions-variance-contravariant-use-covariant.stderr b/src/test/ui/regions/regions-variance-contravariant-use-covariant.stderr
index 44199881444ad..e7c106cbbe3d1 100644
--- a/src/test/ui/regions/regions-variance-contravariant-use-covariant.stderr
+++ b/src/test/ui/regions/regions-variance-contravariant-use-covariant.stderr
@@ -12,3 +12,4 @@ LL |     let _: Contravariant<'long> = c;
 
 error: aborting due to previous error
 
+For more information about this error, try `rustc --explain E0623`.
diff --git a/src/test/ui/regions/regions-variance-covariant-use-contravariant.stderr b/src/test/ui/regions/regions-variance-covariant-use-contravariant.stderr
index 22ba8838893d6..e5e5261ba993f 100644
--- a/src/test/ui/regions/regions-variance-covariant-use-contravariant.stderr
+++ b/src/test/ui/regions/regions-variance-covariant-use-contravariant.stderr
@@ -11,3 +11,4 @@ LL |     let _: Covariant<'short> = c;
 
 error: aborting due to previous error
 
+For more information about this error, try `rustc --explain E0623`.
diff --git a/src/test/ui/regions/regions-variance-invariant-use-contravariant.stderr b/src/test/ui/regions/regions-variance-invariant-use-contravariant.stderr
index a779b485ea701..2a2d5d019a129 100644
--- a/src/test/ui/regions/regions-variance-invariant-use-contravariant.stderr
+++ b/src/test/ui/regions/regions-variance-invariant-use-contravariant.stderr
@@ -11,3 +11,4 @@ LL |     let _: Invariant<'short> = c;
 
 error: aborting due to previous error
 
+For more information about this error, try `rustc --explain E0623`.
diff --git a/src/test/ui/self/arbitrary_self_types_pin_lifetime_mismatch-async.stderr b/src/test/ui/self/arbitrary_self_types_pin_lifetime_mismatch-async.stderr
index e3c261576e61e..37297032632e1 100644
--- a/src/test/ui/self/arbitrary_self_types_pin_lifetime_mismatch-async.stderr
+++ b/src/test/ui/self/arbitrary_self_types_pin_lifetime_mismatch-async.stderr
@@ -24,3 +24,4 @@ LL |     async fn bar<'a>(self: Alias<&Self>, arg: &'a ()) -> &() { arg }
 
 error: aborting due to 3 previous errors
 
+For more information about this error, try `rustc --explain E0623`.
diff --git a/src/test/ui/self/arbitrary_self_types_pin_lifetime_mismatch.stderr b/src/test/ui/self/arbitrary_self_types_pin_lifetime_mismatch.stderr
index 3296e14f806e1..f3a7d14720171 100644
--- a/src/test/ui/self/arbitrary_self_types_pin_lifetime_mismatch.stderr
+++ b/src/test/ui/self/arbitrary_self_types_pin_lifetime_mismatch.stderr
@@ -24,3 +24,4 @@ LL |     fn bar<'a>(self: Alias<&Self>, arg: &'a ()) -> &() { arg }
 
 error: aborting due to 3 previous errors
 
+For more information about this error, try `rustc --explain E0623`.
diff --git a/src/test/ui/self/elision/lt-ref-self-async.stderr b/src/test/ui/self/elision/lt-ref-self-async.stderr
index 6b668d9f1f655..235b71ccab3a8 100644
--- a/src/test/ui/self/elision/lt-ref-self-async.stderr
+++ b/src/test/ui/self/elision/lt-ref-self-async.stderr
@@ -60,3 +60,4 @@ LL |         f
 
 error: aborting due to 6 previous errors
 
+For more information about this error, try `rustc --explain E0623`.
diff --git a/src/test/ui/self/elision/lt-ref-self.stderr b/src/test/ui/self/elision/lt-ref-self.stderr
index f73b3eddd3821..afd07d38f2fe4 100644
--- a/src/test/ui/self/elision/lt-ref-self.stderr
+++ b/src/test/ui/self/elision/lt-ref-self.stderr
@@ -60,3 +60,4 @@ LL |         f
 
 error: aborting due to 6 previous errors
 
+For more information about this error, try `rustc --explain E0623`.
diff --git a/src/test/ui/self/elision/ref-mut-self-async.stderr b/src/test/ui/self/elision/ref-mut-self-async.stderr
index 29fbec9fa7ae0..a656808d46bc2 100644
--- a/src/test/ui/self/elision/ref-mut-self-async.stderr
+++ b/src/test/ui/self/elision/ref-mut-self-async.stderr
@@ -60,3 +60,4 @@ LL |         f
 
 error: aborting due to 6 previous errors
 
+For more information about this error, try `rustc --explain E0623`.
diff --git a/src/test/ui/self/elision/ref-mut-self.stderr b/src/test/ui/self/elision/ref-mut-self.stderr
index 37984cd72fbac..3d6ae4b3dd388 100644
--- a/src/test/ui/self/elision/ref-mut-self.stderr
+++ b/src/test/ui/self/elision/ref-mut-self.stderr
@@ -60,3 +60,4 @@ LL |         f
 
 error: aborting due to 6 previous errors
 
+For more information about this error, try `rustc --explain E0623`.
diff --git a/src/test/ui/self/elision/ref-mut-struct-async.stderr b/src/test/ui/self/elision/ref-mut-struct-async.stderr
index 46591bfc9580f..2dc8cdb7d28ec 100644
--- a/src/test/ui/self/elision/ref-mut-struct-async.stderr
+++ b/src/test/ui/self/elision/ref-mut-struct-async.stderr
@@ -50,3 +50,4 @@ LL |         f
 
 error: aborting due to 5 previous errors
 
+For more information about this error, try `rustc --explain E0623`.
diff --git a/src/test/ui/self/elision/ref-mut-struct.stderr b/src/test/ui/self/elision/ref-mut-struct.stderr
index 2a4826905b94a..3fec398bb9879 100644
--- a/src/test/ui/self/elision/ref-mut-struct.stderr
+++ b/src/test/ui/self/elision/ref-mut-struct.stderr
@@ -50,3 +50,4 @@ LL |         f
 
 error: aborting due to 5 previous errors
 
+For more information about this error, try `rustc --explain E0623`.
diff --git a/src/test/ui/self/elision/ref-self-async.stderr b/src/test/ui/self/elision/ref-self-async.stderr
index c255d18936376..bda958241b67b 100644
--- a/src/test/ui/self/elision/ref-self-async.stderr
+++ b/src/test/ui/self/elision/ref-self-async.stderr
@@ -70,3 +70,4 @@ LL |         f
 
 error: aborting due to 7 previous errors
 
+For more information about this error, try `rustc --explain E0623`.
diff --git a/src/test/ui/self/elision/ref-self.stderr b/src/test/ui/self/elision/ref-self.stderr
index 611498f18da42..8343c8d349e16 100644
--- a/src/test/ui/self/elision/ref-self.stderr
+++ b/src/test/ui/self/elision/ref-self.stderr
@@ -70,3 +70,4 @@ LL |         f
 
 error: aborting due to 7 previous errors
 
+For more information about this error, try `rustc --explain E0623`.
diff --git a/src/test/ui/self/elision/ref-struct-async.stderr b/src/test/ui/self/elision/ref-struct-async.stderr
index c70facc931ec1..49a2a00953d87 100644
--- a/src/test/ui/self/elision/ref-struct-async.stderr
+++ b/src/test/ui/self/elision/ref-struct-async.stderr
@@ -50,3 +50,4 @@ LL |         f
 
 error: aborting due to 5 previous errors
 
+For more information about this error, try `rustc --explain E0623`.
diff --git a/src/test/ui/self/elision/ref-struct.stderr b/src/test/ui/self/elision/ref-struct.stderr
index 186e651c143bf..5116488dd22bb 100644
--- a/src/test/ui/self/elision/ref-struct.stderr
+++ b/src/test/ui/self/elision/ref-struct.stderr
@@ -50,3 +50,4 @@ LL |         f
 
 error: aborting due to 5 previous errors
 
+For more information about this error, try `rustc --explain E0623`.
diff --git a/src/test/ui/type-alias-impl-trait/issue-63279.rs b/src/test/ui/type-alias-impl-trait/issue-63279.rs
new file mode 100644
index 0000000000000..586ff7a31587f
--- /dev/null
+++ b/src/test/ui/type-alias-impl-trait/issue-63279.rs
@@ -0,0 +1,9 @@
+#![feature(type_alias_impl_trait)]
+
+type Closure = impl FnOnce(); //~ ERROR: type mismatch resolving
+
+fn c() -> Closure {
+    || -> Closure { || () }
+}
+
+fn main() {}
diff --git a/src/test/ui/type-alias-impl-trait/issue-63279.stderr b/src/test/ui/type-alias-impl-trait/issue-63279.stderr
new file mode 100644
index 0000000000000..a5065241fc74d
--- /dev/null
+++ b/src/test/ui/type-alias-impl-trait/issue-63279.stderr
@@ -0,0 +1,13 @@
+error[E0271]: type mismatch resolving `<[closure@$DIR/issue-63279.rs:6:5: 6:28] as std::ops::FnOnce<()>>::Output == ()`
+  --> $DIR/issue-63279.rs:3:1
+   |
+LL | type Closure = impl FnOnce();
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ expected opaque type, found ()
+   |
+   = note: expected type `Closure`
+              found type `()`
+   = note: the return type of a function must have a statically known size
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0271`.
diff --git a/src/test/ui/unboxed-closures/issue-30904.rs b/src/test/ui/unboxed-closures/issue-30904.rs
new file mode 100644
index 0000000000000..eec5e962b431e
--- /dev/null
+++ b/src/test/ui/unboxed-closures/issue-30904.rs
@@ -0,0 +1,36 @@
+#![feature(fn_traits, unboxed_closures)]
+
+fn test<F: for<'x> FnOnce<(&'x str,)>>(_: F) {}
+
+struct Compose<F,G>(F,G);
+impl<T,F,G> FnOnce<(T,)> for Compose<F,G>
+where F: FnOnce<(T,)>, G: FnOnce<(F::Output,)> {
+    type Output = G::Output;
+    extern "rust-call" fn call_once(self, (x,): (T,)) -> G::Output {
+        (self.1)((self.0)(x))
+    }
+}
+
+struct Str<'a>(&'a str);
+fn mk_str<'a>(s: &'a str) -> Str<'a> { Str(s) }
+
+fn main() {
+    let _: for<'a> fn(&'a str) -> Str<'a> = mk_str;
+    // expected concrete lifetime, found bound lifetime parameter 'a
+    let _: for<'a> fn(&'a str) -> Str<'a> = Str;
+    //~^ ERROR: mismatched types
+
+    test(|_: &str| {});
+    test(mk_str);
+    // expected concrete lifetime, found bound lifetime parameter 'x
+    test(Str); //~ ERROR: type mismatch in function arguments
+
+    test(Compose(|_: &str| {}, |_| {}));
+    test(Compose(mk_str, |_| {}));
+    // internal compiler error: cannot relate bound region:
+    //   ReLateBound(DebruijnIndex { depth: 2 },
+    //     BrNamed(DefId { krate: 0, node: DefIndex(6) => test::'x }, 'x(65)))
+    //<= ReSkolemized(0,
+    //     BrNamed(DefId { krate: 0, node: DefIndex(6) => test::'x }, 'x(65)))
+    test(Compose(Str, |_| {}));
+}
diff --git a/src/test/ui/unboxed-closures/issue-30904.stderr b/src/test/ui/unboxed-closures/issue-30904.stderr
new file mode 100644
index 0000000000000..943cbe0ccc297
--- /dev/null
+++ b/src/test/ui/unboxed-closures/issue-30904.stderr
@@ -0,0 +1,24 @@
+error[E0308]: mismatched types
+  --> $DIR/issue-30904.rs:20:45
+   |
+LL |     let _: for<'a> fn(&'a str) -> Str<'a> = Str;
+   |                                             ^^^ expected concrete lifetime, found bound lifetime parameter 'a
+   |
+   = note: expected type `for<'a> fn(&'a str) -> Str<'a>`
+              found type `fn(&str) -> Str<'_> {Str::<'_>}`
+
+error[E0631]: type mismatch in function arguments
+  --> $DIR/issue-30904.rs:26:10
+   |
+LL | fn test<F: for<'x> FnOnce<(&'x str,)>>(_: F) {}
+   |    ----    -------------------------- required by this bound in `test`
+...
+LL | struct Str<'a>(&'a str);
+   | ------------------------ found signature of `fn(&str) -> _`
+...
+LL |     test(Str);
+   |          ^^^ expected signature of `for<'x> fn(&'x str) -> _`
+
+error: aborting due to 2 previous errors
+
+For more information about this error, try `rustc --explain E0308`.
diff --git a/src/test/ui/underscore-lifetime/underscore-lifetime-elison-mismatch.stderr b/src/test/ui/underscore-lifetime/underscore-lifetime-elison-mismatch.stderr
index 21fdfcaef862e..76c14ccc14b45 100644
--- a/src/test/ui/underscore-lifetime/underscore-lifetime-elison-mismatch.stderr
+++ b/src/test/ui/underscore-lifetime/underscore-lifetime-elison-mismatch.stderr
@@ -8,3 +8,4 @@ LL | fn foo(x: &mut Vec<&'_ u8>, y: &'_ u8) { x.push(y); }
 
 error: aborting due to previous error
 
+For more information about this error, try `rustc --explain E0623`.
diff --git a/src/test/ui/variance/variance-cell-is-invariant.stderr b/src/test/ui/variance/variance-cell-is-invariant.stderr
index 91f6d7659ed4e..6fcd6460fe30a 100644
--- a/src/test/ui/variance/variance-cell-is-invariant.stderr
+++ b/src/test/ui/variance/variance-cell-is-invariant.stderr
@@ -12,3 +12,4 @@ LL |     let _: Foo<'long> = c;
 
 error: aborting due to previous error
 
+For more information about this error, try `rustc --explain E0623`.