Auto merge of #63990 - Centril:rollup-q1nt0b0, r=Centril

Rollup of 11 pull requests

Successful merges:

 - #63811 (Correctly suggest adding bounds to `impl Trait` argument)
 - #63933 (Resolve some small issues related to #63580)
 - #63938 (or-pattern: fix typo in error message)
 - #63945 (Recover `mut $pat` and other improvements)
 - #63958 (const_prop: only call error_to_const_error if we are actually showing something)
 - #63961 (Add Option<Span> to `require_lang_item`)
 - #63963 (remove the reference to __cxa_thread_atexit_impl)
 - #63965 (Prevent syntax error in LD linker version script)
 - #63968 (rustc_apfloat: make the crate #![no_std] explicitly.)
 - #63970 (Notify me (flip1995) when Clippy toolstate changes)
 - #63980 (add missing `#[repr(C)]` on the Slices union)

Failed merges:

 - #63989 (Add Yaah to clippy toolstain notification list)

r? @ghost

src/libcore/str/mod.rs

@@ -2170,6 +2170,7 @@ impl str {
     #[inline(always)]
     #[rustc_const_unstable(feature="const_str_as_bytes")]
     pub const fn as_bytes(&self) -> &[u8] {
+        #[repr(C)]
         union Slices<'a> {
             str: &'a str,
             slice: &'a [u8],

src/librustc/infer/mod.rs

@@ -1460,7 +1460,7 @@ impl<'a, 'tcx> InferCtxt<'a, 'tcx> {
             }
         }
 
-        let copy_def_id = self.tcx.require_lang_item(lang_items::CopyTraitLangItem);
+        let copy_def_id = self.tcx.require_lang_item(lang_items::CopyTraitLangItem, None);
 
         // this can get called from typeck (by euv), and moves_by_default
         // rightly refuses to work with inference variables, but

src/librustc/middle/lang_items.rs

@@ -381,9 +381,13 @@ language_item_table! {
 impl<'tcx> TyCtxt<'tcx> {
     /// Returns the `DefId` for a given `LangItem`.
     /// If not found, fatally abort compilation.
-    pub fn require_lang_item(&self, lang_item: LangItem) -> DefId {
+    pub fn require_lang_item(&self, lang_item: LangItem, span: Option<Span>) -> DefId {
         self.lang_items().require(lang_item).unwrap_or_else(|msg| {
-            self.sess.fatal(&msg)
+            if let Some(span) = span {
+                self.sess.span_fatal(span, &msg)
+            } else {
+                self.sess.fatal(&msg)
+            }
         })
     }
 }

src/librustc/mir/mod.rs

@@ -1733,6 +1733,10 @@ pub enum PlaceBase<'tcx> {
 pub struct Static<'tcx> {
     pub ty: Ty<'tcx>,
     pub kind: StaticKind<'tcx>,
+    /// The `DefId` of the item this static was declared in. For promoted values, usually, this is
+    /// the same as the `DefId` of the `mir::Body` containing the `Place` this promoted appears in.
+    /// However, after inlining, that might no longer be the case as inlined `Place`s are copied
+    /// into the calling frame.
     pub def_id: DefId,
 }
 
@@ -1740,6 +1744,9 @@ pub struct Static<'tcx> {
     Clone, Debug, PartialEq, Eq, PartialOrd, Ord, Hash, HashStable, RustcEncodable, RustcDecodable,
 )]
 pub enum StaticKind<'tcx> {
+    /// Promoted references consist of an id (`Promoted`) and the substs necessary to monomorphize
+    /// it. Usually, these substs are just the identity substs for the item. However, the inliner
+    /// will adjust these substs when it inlines a function based on the substs at the callsite.
     Promoted(Promoted, SubstsRef<'tcx>),
     Static,
 }

src/librustc/traits/select.rs

@@ -3513,7 +3513,7 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
 
                 // We can only make objects from sized types.
                 let tr = ty::TraitRef {
-                    def_id: tcx.require_lang_item(lang_items::SizedTraitLangItem),
+                    def_id: tcx.require_lang_item(lang_items::SizedTraitLangItem, None),
                     substs: tcx.mk_substs_trait(source, &[]),
                 };
                 nested.push(predicate_to_obligation(tr.to_predicate()));

src/librustc/ty/context.rs

@@ -2385,13 +2385,13 @@ impl<'tcx> TyCtxt<'tcx> {
 
     #[inline]
     pub fn mk_box(self, ty: Ty<'tcx>) -> Ty<'tcx> {
-        let def_id = self.require_lang_item(lang_items::OwnedBoxLangItem);
+        let def_id = self.require_lang_item(lang_items::OwnedBoxLangItem, None);
         self.mk_generic_adt(def_id, ty)
     }
 
     #[inline]
     pub fn mk_maybe_uninit(self, ty: Ty<'tcx>) -> Ty<'tcx> {
-        let def_id = self.require_lang_item(lang_items::MaybeUninitLangItem);
+        let def_id = self.require_lang_item(lang_items::MaybeUninitLangItem, None);
         self.mk_generic_adt(def_id, ty)
     }
 

src/librustc/ty/instance.rs

@@ -327,7 +327,7 @@ impl<'tcx> Instance<'tcx> {
     }
 
     pub fn resolve_drop_in_place(tcx: TyCtxt<'tcx>, ty: Ty<'tcx>) -> ty::Instance<'tcx> {
-        let def_id = tcx.require_lang_item(DropInPlaceFnLangItem);
+        let def_id = tcx.require_lang_item(DropInPlaceFnLangItem, None);
         let substs = tcx.intern_substs(&[ty.into()]);
         Instance::resolve(tcx, ty::ParamEnv::reveal_all(), def_id, substs).unwrap()
     }

src/librustc/ty/mod.rs

@@ -2588,12 +2588,12 @@ impl<'tcx> ClosureKind {
 
     pub fn trait_did(&self, tcx: TyCtxt<'tcx>) -> DefId {
         match *self {
-            ClosureKind::Fn => tcx.require_lang_item(FnTraitLangItem),
+            ClosureKind::Fn => tcx.require_lang_item(FnTraitLangItem, None),
             ClosureKind::FnMut => {
-                tcx.require_lang_item(FnMutTraitLangItem)
+                tcx.require_lang_item(FnMutTraitLangItem, None)
             }
             ClosureKind::FnOnce => {
-                tcx.require_lang_item(FnOnceTraitLangItem)
+                tcx.require_lang_item(FnOnceTraitLangItem, None)
             }
         }
     }

src/librustc/ty/util.rs

@@ -998,7 +998,7 @@ impl<'tcx> ty::TyS<'tcx> {
 
 fn is_copy_raw<'tcx>(tcx: TyCtxt<'tcx>, query: ty::ParamEnvAnd<'tcx, Ty<'tcx>>) -> bool {
     let (param_env, ty) = query.into_parts();
-    let trait_def_id = tcx.require_lang_item(lang_items::CopyTraitLangItem);
+    let trait_def_id = tcx.require_lang_item(lang_items::CopyTraitLangItem, None);
     tcx.infer_ctxt()
         .enter(|infcx| traits::type_known_to_meet_bound_modulo_regions(
             &infcx,
@@ -1011,7 +1011,7 @@ fn is_copy_raw<'tcx>(tcx: TyCtxt<'tcx>, query: ty::ParamEnvAnd<'tcx, Ty<'tcx>>)
 
 fn is_sized_raw<'tcx>(tcx: TyCtxt<'tcx>, query: ty::ParamEnvAnd<'tcx, Ty<'tcx>>) -> bool {
     let (param_env, ty) = query.into_parts();
-    let trait_def_id = tcx.require_lang_item(lang_items::SizedTraitLangItem);
+    let trait_def_id = tcx.require_lang_item(lang_items::SizedTraitLangItem, None);
     tcx.infer_ctxt()
         .enter(|infcx| traits::type_known_to_meet_bound_modulo_regions(
             &infcx,
@@ -1024,7 +1024,7 @@ fn is_sized_raw<'tcx>(tcx: TyCtxt<'tcx>, query: ty::ParamEnvAnd<'tcx, Ty<'tcx>>)
 
 fn is_freeze_raw<'tcx>(tcx: TyCtxt<'tcx>, query: ty::ParamEnvAnd<'tcx, Ty<'tcx>>) -> bool {
     let (param_env, ty) = query.into_parts();
-    let trait_def_id = tcx.require_lang_item(lang_items::FreezeTraitLangItem);
+    let trait_def_id = tcx.require_lang_item(lang_items::FreezeTraitLangItem, None);
     tcx.infer_ctxt()
         .enter(|infcx| traits::type_known_to_meet_bound_modulo_regions(
             &infcx,

src/librustc/ty/wf.rs

@@ -221,7 +221,7 @@ impl<'a, 'tcx> WfPredicates<'a, 'tcx> {
         if !subty.has_escaping_bound_vars() {
             let cause = self.cause(cause);
             let trait_ref = ty::TraitRef {
-                def_id: self.infcx.tcx.require_lang_item(lang_items::SizedTraitLangItem),
+                def_id: self.infcx.tcx.require_lang_item(lang_items::SizedTraitLangItem, None),
                 substs: self.infcx.tcx.mk_substs_trait(subty, &[]),
             };
             self.out.push(traits::Obligation::new(cause, self.param_env, trait_ref.to_predicate()));

src/librustc_apfloat/ieee.rs

@@ -1,13 +1,13 @@
 use crate::{Category, ExpInt, IEK_INF, IEK_NAN, IEK_ZERO};
 use crate::{Float, FloatConvert, ParseError, Round, Status, StatusAnd};
 
+use core::cmp::{self, Ordering};
+use core::convert::TryFrom;
+use core::fmt::{self, Write};
+use core::marker::PhantomData;
+use core::mem;
+use core::ops::Neg;
 use smallvec::{SmallVec, smallvec};
-use std::cmp::{self, Ordering};
-use std::convert::TryFrom;
-use std::fmt::{self, Write};
-use std::marker::PhantomData;
-use std::mem;
-use std::ops::Neg;
 
 #[must_use]
 pub struct IeeeFloat<S> {
@@ -2287,8 +2287,8 @@ impl Loss {
 /// Implementation details of IeeeFloat significands, such as big integer arithmetic.
 /// As a rule of thumb, no functions in this module should dynamically allocate.
 mod sig {
-    use std::cmp::Ordering;
-    use std::mem;
+    use core::cmp::Ordering;
+    use core::mem;
     use super::{ExpInt, Limb, LIMB_BITS, limbs_for_bits, Loss};
 
     pub(super) fn is_all_zeros(limbs: &[Limb]) -> bool {

src/librustc_apfloat/lib.rs

@@ -31,15 +31,19 @@
 //! This API is completely unstable and subject to change.
 
 #![doc(html_root_url = "https://doc.rust-lang.org/nightly/")]
+#![no_std]
 #![forbid(unsafe_code)]
 
 #![feature(nll)]
 
-use std::cmp::Ordering;
-use std::fmt;
-use std::ops::{Neg, Add, Sub, Mul, Div, Rem};
-use std::ops::{AddAssign, SubAssign, MulAssign, DivAssign, RemAssign};
-use std::str::FromStr;
+#[macro_use]
+extern crate alloc;
+
+use core::cmp::Ordering;
+use core::fmt;
+use core::ops::{Neg, Add, Sub, Mul, Div, Rem};
+use core::ops::{AddAssign, SubAssign, MulAssign, DivAssign, RemAssign};
+use core::str::FromStr;
 
 bitflags::bitflags! {
     /// IEEE-754R 7: Default exception handling.
@@ -587,7 +591,7 @@ macro_rules! float_common_impls {
             }
         }
 
-        impl<$t> ::std::str::FromStr for $ty<$t> where Self: Float {
+        impl<$t> ::core::str::FromStr for $ty<$t> where Self: Float {
             type Err = ParseError;
             fn from_str(s: &str) -> Result<Self, ParseError> {
                 Self::from_str_r(s, Round::NearestTiesToEven).map(|x| x.value)
@@ -596,66 +600,66 @@ macro_rules! float_common_impls {
 
         // Rounding ties to the nearest even, by default.
 
-        impl<$t> ::std::ops::Add for $ty<$t> where Self: Float {
+        impl<$t> ::core::ops::Add for $ty<$t> where Self: Float {
             type Output = StatusAnd<Self>;
             fn add(self, rhs: Self) -> StatusAnd<Self> {
                 self.add_r(rhs, Round::NearestTiesToEven)
             }
         }
 
-        impl<$t> ::std::ops::Sub for $ty<$t> where Self: Float {
+        impl<$t> ::core::ops::Sub for $ty<$t> where Self: Float {
             type Output = StatusAnd<Self>;
             fn sub(self, rhs: Self) -> StatusAnd<Self> {
                 self.sub_r(rhs, Round::NearestTiesToEven)
             }
         }
 
-        impl<$t> ::std::ops::Mul for $ty<$t> where Self: Float {
+        impl<$t> ::core::ops::Mul for $ty<$t> where Self: Float {
             type Output = StatusAnd<Self>;
             fn mul(self, rhs: Self) -> StatusAnd<Self> {
                 self.mul_r(rhs, Round::NearestTiesToEven)
             }
         }
 
-        impl<$t> ::std::ops::Div for $ty<$t> where Self: Float {
+        impl<$t> ::core::ops::Div for $ty<$t> where Self: Float {
             type Output = StatusAnd<Self>;
             fn div(self, rhs: Self) -> StatusAnd<Self> {
                 self.div_r(rhs, Round::NearestTiesToEven)
             }
         }
 
-        impl<$t> ::std::ops::Rem for $ty<$t> where Self: Float {
+        impl<$t> ::core::ops::Rem for $ty<$t> where Self: Float {
             type Output = StatusAnd<Self>;
             fn rem(self, rhs: Self) -> StatusAnd<Self> {
                 self.c_fmod(rhs)
             }
         }
 
-        impl<$t> ::std::ops::AddAssign for $ty<$t> where Self: Float {
+        impl<$t> ::core::ops::AddAssign for $ty<$t> where Self: Float {
             fn add_assign(&mut self, rhs: Self) {
                 *self = (*self + rhs).value;
             }
         }
 
-        impl<$t> ::std::ops::SubAssign for $ty<$t> where Self: Float {
+        impl<$t> ::core::ops::SubAssign for $ty<$t> where Self: Float {
             fn sub_assign(&mut self, rhs: Self) {
                 *self = (*self - rhs).value;
             }
         }
 
-        impl<$t> ::std::ops::MulAssign for $ty<$t> where Self: Float {
+        impl<$t> ::core::ops::MulAssign for $ty<$t> where Self: Float {
             fn mul_assign(&mut self, rhs: Self) {
                 *self = (*self * rhs).value;
             }
         }
 
-        impl<$t> ::std::ops::DivAssign for $ty<$t> where Self: Float {
+        impl<$t> ::core::ops::DivAssign for $ty<$t> where Self: Float {
             fn div_assign(&mut self, rhs: Self) {
                 *self = (*self / rhs).value;
             }
         }
 
-        impl<$t> ::std::ops::RemAssign for $ty<$t> where Self: Float {
+        impl<$t> ::core::ops::RemAssign for $ty<$t> where Self: Float {
             fn rem_assign(&mut self, rhs: Self) {
                 *self = (*self % rhs).value;
             }

src/librustc_apfloat/ppc.rs

@@ -1,9 +1,9 @@
 use crate::{Category, ExpInt, Float, FloatConvert, Round, ParseError, Status, StatusAnd};
 use crate::ieee;
 
-use std::cmp::Ordering;
-use std::fmt;
-use std::ops::Neg;
+use core::cmp::Ordering;
+use core::fmt;
+use core::ops::Neg;
 
 #[must_use]
 #[derive(Copy, Clone, PartialEq, PartialOrd, Debug)]

src/librustc_codegen_ssa/back/linker.rs

@@ -430,10 +430,13 @@ impl<'a> Linker for GccLinker<'a> {
             // Write an LD version script
             let res: io::Result<()> = try {
                 let mut f = BufWriter::new(File::create(&path)?);
-                writeln!(f, "{{\n  global:")?;
-                for sym in self.info.exports[&crate_type].iter() {
-                    debug!("    {};", sym);
-                    writeln!(f, "    {};", sym)?;
+                writeln!(f, "{{")?;
+                if !self.info.exports[&crate_type].is_empty() {
+                    writeln!(f, "  global:")?;
+                    for sym in self.info.exports[&crate_type].iter() {
+                        debug!("    {};", sym);
+                        writeln!(f, "    {};", sym)?;
+                    }
                 }
                 writeln!(f, "\n  local:\n    *;\n}};")?;
             };

src/librustc_codegen_ssa/base.rs

@@ -456,7 +456,7 @@ pub fn maybe_create_entry_wrapper<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>>(cx: &'
         let arg_argv = param_argv;
 
         let (start_fn, args) = if use_start_lang_item {
-            let start_def_id = cx.tcx().require_lang_item(StartFnLangItem);
+            let start_def_id = cx.tcx().require_lang_item(StartFnLangItem, None);
             let start_fn = callee::resolve_and_get_fn(
                 cx,
                 start_def_id,

src/librustc_metadata/cstore_impl.rs

@@ -125,24 +125,8 @@ provide! { <'tcx> tcx, def_id, other, cdata,
             bug!("coerce_unsized_info: `{:?}` is missing its info", def_id);
         })
     }
-    optimized_mir => {
-        let mir = cdata.maybe_get_optimized_mir(tcx, def_id.index).unwrap_or_else(|| {
-            bug!("get_optimized_mir: missing MIR for `{:?}`", def_id)
-        });
-
-        let mir = tcx.arena.alloc(mir);
-
-        mir
-    }
-    promoted_mir => {
-        let promoted = cdata.maybe_get_promoted_mir(tcx, def_id.index).unwrap_or_else(|| {
-            bug!("get_promoted_mir: missing promoted MIR for `{:?}`", def_id)
-        });
-
-        let promoted = tcx.arena.alloc(promoted);
-
-        promoted
-    }
+    optimized_mir => { tcx.arena.alloc(cdata.get_optimized_mir(tcx, def_id.index)) }
+    promoted_mir => { tcx.arena.alloc(cdata.get_promoted_mir(tcx, def_id.index)) }
     mir_const_qualif => {
         (cdata.mir_const_qualif(def_id.index), tcx.arena.alloc(BitSet::new_empty(0)))
     }

src/librustc_metadata/decoder.rs

@@ -450,11 +450,19 @@ impl<'a, 'tcx> CrateMetadata {
     pub fn is_proc_macro_crate(&self) -> bool {
         self.root.proc_macro_decls_static.is_some()
     }
+
     fn is_proc_macro(&self, id: DefIndex) -> bool {
         self.is_proc_macro_crate() &&
             self.root.proc_macro_data.unwrap().decode(self).find(|x| *x == id).is_some()
     }
 
+    fn entry_unless_proc_macro(&self, id: DefIndex) -> Option<Entry<'tcx>> {
+        match self.is_proc_macro(id) {
+            true => None,
+            false => Some(self.entry(id)),
+        }
+    }
+
     fn maybe_entry(&self, item_id: DefIndex) -> Option<Lazy<Entry<'tcx>>> {
         self.root.entries_index.lookup(self.blob.raw_bytes(), item_id)
     }
@@ -689,10 +697,8 @@ impl<'a, 'tcx> CrateMetadata {
     }
 
     pub fn get_deprecation(&self, id: DefIndex) -> Option<attr::Deprecation> {
-        match self.is_proc_macro(id) {
-            true => None,
-            false => self.entry(id).deprecation.map(|depr| depr.decode(self)),
-        }
+        self.entry_unless_proc_macro(id)
+            .and_then(|entry| entry.deprecation.map(|depr| depr.decode(self)))
     }
 
     pub fn get_visibility(&self, id: DefIndex) -> ty::Visibility {
@@ -902,22 +908,24 @@ impl<'a, 'tcx> CrateMetadata {
         self.maybe_entry(id).and_then(|item| item.decode(self).mir).is_some()
     }
 
-    pub fn maybe_get_optimized_mir(&self, tcx: TyCtxt<'tcx>, id: DefIndex) -> Option<Body<'tcx>> {
-        match self.is_proc_macro(id) {
-            true => None,
-            false => self.entry(id).mir.map(|mir| mir.decode((self, tcx))),
-        }
+    pub fn get_optimized_mir(&self, tcx: TyCtxt<'tcx>, id: DefIndex) -> Body<'tcx> {
+        self.entry_unless_proc_macro(id)
+            .and_then(|entry| entry.mir.map(|mir| mir.decode((self, tcx))))
+            .unwrap_or_else(|| {
+                bug!("get_optimized_mir: missing MIR for `{:?}", self.local_def_id(id))
+            })
     }
 
-    pub fn maybe_get_promoted_mir(
+    pub fn get_promoted_mir(
         &self,
         tcx: TyCtxt<'tcx>,
         id: DefIndex,
-    ) -> Option<IndexVec<Promoted, Body<'tcx>>> {
-        match self.is_proc_macro(id) {
-            true => None,
-            false => self.entry(id).promoted_mir.map(|promoted| promoted.decode((self, tcx)),)
-        }
+    ) -> IndexVec<Promoted, Body<'tcx>> {
+        self.entry_unless_proc_macro(id)
+            .and_then(|entry| entry.promoted_mir.map(|promoted| promoted.decode((self, tcx))))
+            .unwrap_or_else(|| {
+                bug!("get_promoted_mir: missing MIR for `{:?}`", self.local_def_id(id))
+            })
     }
 
     pub fn mir_const_qualif(&self, id: DefIndex) -> u8 {

src/librustc_mir/build/matches/test.rs

@@ -443,7 +443,7 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
             _ => bug!("non_scalar_compare called on non-reference type: {}", ty),
         };
 
-        let eq_def_id = self.hir.tcx().require_lang_item(EqTraitLangItem);
+        let eq_def_id = self.hir.tcx().require_lang_item(EqTraitLangItem, None);
         let method = self.hir.trait_method(eq_def_id, sym::eq, deref_ty, &[deref_ty.into()]);
 
         let bool_ty = self.hir.bool_ty();

src/librustc_mir/const_eval.rs

@@ -519,6 +519,9 @@ pub fn const_variant_index<'tcx>(
     ecx.read_discriminant(op).unwrap().1
 }
 
+/// Turn an interpreter error into something to report to the user.
+/// As a side-effect, if RUSTC_CTFE_BACKTRACE is set, this prints the backtrace.
+/// Should be called only if the error is actually going to to be reported!
 pub fn error_to_const_error<'mir, 'tcx>(
     ecx: &InterpCx<'mir, 'tcx, CompileTimeInterpreter<'mir, 'tcx>>,
     mut error: InterpErrorInfo<'tcx>,

src/librustc_mir/transform/const_prop.rs

@@ -237,9 +237,8 @@ impl<'mir, 'tcx> ConstPropagator<'mir, 'tcx> {
         let r = match f(self) {
             Ok(val) => Some(val),
             Err(error) => {
-                let diagnostic = error_to_const_error(&self.ecx, error);
                 use rustc::mir::interpret::InterpError::*;
-                match diagnostic.error {
+                match error.kind {
                     Exit(_) => bug!("the CTFE program cannot exit"),
                     Unsupported(_)
                     | UndefinedBehavior(_)
@@ -248,6 +247,7 @@ impl<'mir, 'tcx> ConstPropagator<'mir, 'tcx> {
                         // Ignore these errors.
                     }
                     Panic(_) => {
+                        let diagnostic = error_to_const_error(&self.ecx, error);
                         diagnostic.report_as_lint(
                             self.ecx.tcx,
                             "this expression will panic at runtime",

src/librustc_mir/transform/qualify_consts.rs

@@ -1752,7 +1752,10 @@ impl<'tcx> MirPass<'tcx> for QualifyAndPromoteConstants<'tcx> {
                 fulfillment_cx.register_bound(&infcx,
                                               param_env,
                                               ty,
-                                              tcx.require_lang_item(lang_items::SyncTraitLangItem),
+                                              tcx.require_lang_item(
+                                                  lang_items::SyncTraitLangItem,
+                                                  Some(body.span)
+                                              ),
                                               cause);
                 if let Err(err) = fulfillment_cx.select_all_or_error(&infcx) {
                     infcx.report_fulfillment_errors(&err, None, false);

src/librustc_mir/util/elaborate_drops.rs

@@ -897,7 +897,10 @@ where
     ) -> BasicBlock {
         let tcx = self.tcx();
         let unit_temp = Place::from(self.new_temp(tcx.mk_unit()));
-        let free_func = tcx.require_lang_item(lang_items::BoxFreeFnLangItem);
+        let free_func = tcx.require_lang_item(
+            lang_items::BoxFreeFnLangItem,
+            Some(self.source_info.span)
+        );
         let args = adt.variants[VariantIdx::new(0)].fields.iter().enumerate().map(|(i, f)| {
             let field = Field::new(i);
             let field_ty = f.ty(self.tcx(), substs);

src/librustc_typeck/check/cast.rs

@@ -649,7 +649,7 @@ impl<'a, 'tcx> CastCheck<'tcx> {
 
 impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
     fn type_is_known_to_be_sized_modulo_regions(&self, ty: Ty<'tcx>, span: Span) -> bool {
-        let lang_item = self.tcx.require_lang_item(lang_items::SizedTraitLangItem);
+        let lang_item = self.tcx.require_lang_item(lang_items::SizedTraitLangItem, None);
         traits::type_known_to_meet_bound_modulo_regions(self, self.param_env, ty, lang_item, span)
     }
 }

src/librustc_typeck/check/closure.rs

@@ -266,7 +266,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         let trait_ref = projection.to_poly_trait_ref(tcx);
 
         let is_fn = tcx.lang_items().fn_trait_kind(trait_ref.def_id()).is_some();
-        let gen_trait = tcx.require_lang_item(lang_items::GeneratorTraitLangItem);
+        let gen_trait = tcx.require_lang_item(lang_items::GeneratorTraitLangItem, cause_span);
         let is_gen = gen_trait == trait_ref.def_id();
         if !is_fn && !is_gen {
             debug!("deduce_sig_from_projection: not fn or generator");

src/librustc_typeck/check/method/suggest.rs

@@ -743,8 +743,21 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                         // We do this to avoid suggesting code that ends up as `T: FooBar`,
                         // instead we suggest `T: Foo + Bar` in that case.
                         let mut has_bounds = false;
+                        let mut impl_trait = false;
                         if let Node::GenericParam(ref param) = hir.get(id) {
-                            has_bounds = !param.bounds.is_empty();
+                            match param.kind {
+                                hir::GenericParamKind::Type { synthetic: Some(_), .. } => {
+                                    // We've found `fn foo(x: impl Trait)` instead of
+                                    // `fn foo<T>(x: T)`. We want to suggest the correct
+                                    // `fn foo(x: impl Trait + TraitBound)` instead of
+                                    // `fn foo<T: TraitBound>(x: T)`. (#63706)
+                                    impl_trait = true;
+                                    has_bounds = param.bounds.len() > 1;
+                                }
+                                _ => {
+                                    has_bounds = !param.bounds.is_empty();
+                                }
+                            }
                         }
                         let sp = hir.span(id);
                         // `sp` only covers `T`, change it so that it covers
@@ -765,8 +778,9 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                             sp,
                             &msg[..],
                             candidates.iter().map(|t| format!(
-                                "{}: {}{}",
+                                "{}{} {}{}",
                                 param,
+                                if impl_trait { " +" } else { ":" },
                                 self.tcx.def_path_str(t.def_id),
                                 if has_bounds { " +"} else { "" },
                             )),

src/librustc_typeck/check/mod.rs

@@ -2622,7 +2622,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                                  span: Span,
                                  code: traits::ObligationCauseCode<'tcx>)
     {
-        let lang_item = self.tcx.require_lang_item(lang_items::SizedTraitLangItem);
+        let lang_item = self.tcx.require_lang_item(lang_items::SizedTraitLangItem, None);
         self.require_type_meets(ty, span, code, lang_item);
     }
 

src/librustc_typeck/check/wfcheck.rs

@@ -287,7 +287,7 @@ fn check_type_defn<'tcx, F>(
                 let last = idx == variant.fields.len() - 1;
                 fcx.register_bound(
                     field.ty,
-                    fcx.tcx.require_lang_item(lang_items::SizedTraitLangItem),
+                    fcx.tcx.require_lang_item(lang_items::SizedTraitLangItem, None),
                     traits::ObligationCause::new(
                         field.span,
                         fcx.body_id,
@@ -375,7 +375,7 @@ fn check_item_type(
         if forbid_unsized {
             fcx.register_bound(
                 item_ty,
-                fcx.tcx.require_lang_item(lang_items::SizedTraitLangItem),
+                fcx.tcx.require_lang_item(lang_items::SizedTraitLangItem, None),
                 traits::ObligationCause::new(ty_span, fcx.body_id, traits::MiscObligation),
             );
         }

src/librustdoc/clean/auto_trait.rs

@@ -464,7 +464,7 @@ impl<'a, 'tcx> AutoTraitFinder<'a, 'tcx> {
         // it is *not* required (i.e., '?Sized')
         let sized_trait = self.cx
             .tcx
-            .require_lang_item(lang_items::SizedTraitLangItem);
+            .require_lang_item(lang_items::SizedTraitLangItem, None);
 
         let mut replacer = RegionReplacer {
             vid_to_region: &vid_to_region,
@@ -777,9 +777,9 @@ impl<'a, 'tcx> AutoTraitFinder<'a, 'tcx> {
     fn is_fn_ty(&self, tcx: TyCtxt<'_>, ty: &Type) -> bool {
         match &ty {
             &&Type::ResolvedPath { ref did, .. } => {
-                *did == tcx.require_lang_item(lang_items::FnTraitLangItem)
-                    || *did == tcx.require_lang_item(lang_items::FnMutTraitLangItem)
-                    || *did == tcx.require_lang_item(lang_items::FnOnceTraitLangItem)
+                *did == tcx.require_lang_item(lang_items::FnTraitLangItem, None)
+                    || *did == tcx.require_lang_item(lang_items::FnMutTraitLangItem, None)
+                    || *did == tcx.require_lang_item(lang_items::FnOnceTraitLangItem, None)
             }
             _ => false,
         }

src/librustdoc/clean/mod.rs

@@ -1037,7 +1037,7 @@ pub enum GenericBound {
 
 impl GenericBound {
     fn maybe_sized(cx: &DocContext<'_>) -> GenericBound {
-        let did = cx.tcx.require_lang_item(lang_items::SizedTraitLangItem);
+        let did = cx.tcx.require_lang_item(lang_items::SizedTraitLangItem, None);
         let empty = cx.tcx.intern_substs(&[]);
         let path = external_path(cx, &cx.tcx.item_name(did).as_str(),
             Some(did), false, vec![], empty);

src/libstd/sys/vxworks/fast_thread_local.rs

@@ -1,33 +1,10 @@
+// Copyright (c) 2019 Wind River Systems, Inc.
+
 #![cfg(target_thread_local)]
 #![unstable(feature = "thread_local_internals", issue = "0")]
 
-// Since what appears to be glibc 2.18 this symbol has been shipped which
-// GCC and clang both use to invoke destructors in thread_local globals, so
-// let's do the same!
-//
-// Note, however, that we run on lots older linuxes, as well as cross
-// compiling from a newer linux to an older linux, so we also have a
-// fallback implementation to use as well.
-//
-// Due to rust-lang/rust#18804, make sure this is not generic!
 pub unsafe fn register_dtor(t: *mut u8, dtor: unsafe extern fn(*mut u8)) {
-    use crate::mem;
     use crate::sys_common::thread_local::register_dtor_fallback;
-
-    extern {
-        #[linkage = "extern_weak"]
-        static __dso_handle: *mut u8;
-        #[linkage = "extern_weak"]
-        static __cxa_thread_atexit_impl: *const libc::c_void;
-    }
-    if !__cxa_thread_atexit_impl.is_null() {
-        type F = unsafe extern fn(dtor: unsafe extern fn(*mut u8),
-                                  arg: *mut u8,
-                                  dso_handle: *mut u8) -> libc::c_int;
-        mem::transmute::<*const libc::c_void, F>(__cxa_thread_atexit_impl)
-            (dtor, t, &__dso_handle as *const _ as *mut _);
-        return
-    }
     register_dtor_fallback(t, dtor);
 }
 

src/libsyntax/parse/literal.rs

@@ -104,7 +104,7 @@ impl LitKind {
 
         Ok(match kind {
             token::Bool => {
-                assert!(symbol == kw::True || symbol == kw::False);
+                assert!(symbol.is_bool_lit());
                 LitKind::Bool(symbol == kw::True)
             }
             token::Byte => return unescape_byte(&symbol.as_str())
@@ -261,7 +261,7 @@ impl Lit {
     /// Converts arbitrary token into an AST literal.
     crate fn from_token(token: &Token) -> Result<Lit, LitError> {
         let lit = match token.kind {
-            token::Ident(name, false) if name == kw::True || name == kw::False =>
+            token::Ident(name, false) if name.is_bool_lit() =>
                 token::Lit::new(token::Bool, name, None),
             token::Literal(lit) =>
                 lit,

src/libsyntax/parse/parser/pat.rs

@@ -4,6 +4,7 @@ use crate::{maybe_recover_from_interpolated_ty_qpath, maybe_whole};
 use crate::ptr::P;
 use crate::ast::{self, Attribute, Pat, PatKind, FieldPat, RangeEnd, RangeSyntax, Mac};
 use crate::ast::{BindingMode, Ident, Mutability, Path, QSelf, Expr, ExprKind};
+use crate::mut_visit::{noop_visit_pat, MutVisitor};
 use crate::parse::token::{self};
 use crate::print::pprust;
 use crate::source_map::{respan, Span, Spanned};
@@ -113,7 +114,7 @@ impl<'a> Parser<'a> {
         let mut pats = vec![first_pat];
         while self.eat_or_separator() {
             let pat = self.parse_pat(expected).map_err(|mut err| {
-                err.span_label(lo, "while parsing this or-pattern staring here");
+                err.span_label(lo, "while parsing this or-pattern starting here");
                 err
             })?;
             self.maybe_recover_unexpected_comma(pat.span, rc)?;
@@ -273,7 +274,7 @@ impl<'a> Parser<'a> {
                 // Parse _
                 PatKind::Wild
             } else if self.eat_keyword(kw::Mut) {
-                self.recover_pat_ident_mut_first()?
+                self.parse_pat_ident_mut()?
             } else if self.eat_keyword(kw::Ref) {
                 // Parse ref ident @ pat / ref mut ident @ pat
                 let mutbl = self.parse_mutability();
@@ -281,13 +282,12 @@ impl<'a> Parser<'a> {
             } else if self.eat_keyword(kw::Box) {
                 // Parse `box pat`
                 PatKind::Box(self.parse_pat_with_range_pat(false, None)?)
-            } else if self.token.is_ident() && !self.token.is_reserved_ident() &&
-                      self.parse_as_ident() {
+            } else if self.can_be_ident_pat() {
                 // Parse `ident @ pat`
                 // This can give false positives and parse nullary enums,
                 // they are dealt with later in resolve.
                 self.parse_pat_ident(BindingMode::ByValue(Mutability::Immutable))?
-            } else if self.token.is_path_start() {
+            } else if self.is_start_of_pat_with_path() {
                 // Parse pattern starting with a path
                 let (qself, path) = if self.eat_lt() {
                     // Parse a qualified path
@@ -384,24 +384,108 @@ impl<'a> Parser<'a> {
         })
     }
 
+    /// Parse a mutable binding with the `mut` token already eaten.
+    fn parse_pat_ident_mut(&mut self) -> PResult<'a, PatKind> {
+        let mut_span = self.prev_span;
+
+        if self.eat_keyword(kw::Ref) {
+            return self.recover_mut_ref_ident(mut_span)
+        }
+
+        self.recover_additional_muts();
+
+        // Make sure we don't allow e.g. `let mut $p;` where `$p:pat`.
+        if let token::Interpolated(ref nt) = self.token.kind {
+             if let token::NtPat(_) = **nt {
+                 self.expected_ident_found().emit();
+             }
+        }
+
+        // Parse the pattern we hope to be an identifier.
+        let mut pat = self.parse_pat(Some("identifier"))?;
+
+        // Add `mut` to any binding in the parsed pattern.
+        let changed_any_binding = Self::make_all_value_bindings_mutable(&mut pat);
+
+        // Unwrap; If we don't have `mut $ident`, error.
+        let pat = pat.into_inner();
+        match &pat.node {
+            PatKind::Ident(..) => {}
+            _ => self.ban_mut_general_pat(mut_span, &pat, changed_any_binding),
+        }
+
+        Ok(pat.node)
+    }
+
     /// Recover on `mut ref? ident @ pat` and suggest
     /// that the order of `mut` and `ref` is incorrect.
-    fn recover_pat_ident_mut_first(&mut self) -> PResult<'a, PatKind> {
-        let mutref_span = self.prev_span.to(self.token.span);
-        let binding_mode = if self.eat_keyword(kw::Ref) {
-            self.struct_span_err(mutref_span, "the order of `mut` and `ref` is incorrect")
-                .span_suggestion(
-                    mutref_span,
-                    "try switching the order",
-                    "ref mut".into(),
-                    Applicability::MachineApplicable
-                )
-                .emit();
-            BindingMode::ByRef(Mutability::Mutable)
+    fn recover_mut_ref_ident(&mut self, lo: Span) -> PResult<'a, PatKind> {
+        let mutref_span = lo.to(self.prev_span);
+        self.struct_span_err(mutref_span, "the order of `mut` and `ref` is incorrect")
+            .span_suggestion(
+                mutref_span,
+                "try switching the order",
+                "ref mut".into(),
+                Applicability::MachineApplicable
+            )
+            .emit();
+
+        self.parse_pat_ident(BindingMode::ByRef(Mutability::Mutable))
+    }
+
+    /// Turn all by-value immutable bindings in a pattern into mutable bindings.
+    /// Returns `true` if any change was made.
+    fn make_all_value_bindings_mutable(pat: &mut P<Pat>) -> bool {
+        struct AddMut(bool);
+        impl MutVisitor for AddMut {
+            fn visit_pat(&mut self, pat: &mut P<Pat>) {
+                if let PatKind::Ident(BindingMode::ByValue(ref mut m @ Mutability::Immutable), ..)
+                    = pat.node
+                {
+                    *m = Mutability::Mutable;
+                    self.0 = true;
+                }
+                noop_visit_pat(pat, self);
+            }
+        }
+
+        let mut add_mut = AddMut(false);
+        add_mut.visit_pat(pat);
+        add_mut.0
+    }
+
+    /// Error on `mut $pat` where `$pat` is not an ident.
+    fn ban_mut_general_pat(&self, lo: Span, pat: &Pat, changed_any_binding: bool) {
+        let span = lo.to(pat.span);
+        let fix = pprust::pat_to_string(&pat);
+        let (problem, suggestion) = if changed_any_binding {
+            ("`mut` must be attached to each individual binding", "add `mut` to each binding")
         } else {
-            BindingMode::ByValue(Mutability::Mutable)
+            ("`mut` must be followed by a named binding", "remove the `mut` prefix")
         };
-        self.parse_pat_ident(binding_mode)
+        self.struct_span_err(span, problem)
+            .span_suggestion(span, suggestion, fix, Applicability::MachineApplicable)
+            .note("`mut` may be followed by `variable` and `variable @ pattern`")
+            .emit()
+    }
+
+    /// Eat any extraneous `mut`s and error + recover if we ate any.
+    fn recover_additional_muts(&mut self) {
+        let lo = self.token.span;
+        while self.eat_keyword(kw::Mut) {}
+        if lo == self.token.span {
+            return;
+        }
+
+        let span = lo.to(self.prev_span);
+        self.struct_span_err(span, "`mut` on a binding may not be repeated")
+            .span_suggestion(
+                span,
+                "remove the additional `mut`s",
+                String::new(),
+                Applicability::MachineApplicable,
+            )
+            .emit();
     }
 
     /// Parse macro invocation
@@ -479,17 +563,6 @@ impl<'a> Parser<'a> {
         Err(err)
     }
 
-    // Helper function to decide whether to parse as ident binding
-    // or to try to do something more complex like range patterns.
-    fn parse_as_ident(&mut self) -> bool {
-        self.look_ahead(1, |t| match t.kind {
-            token::OpenDelim(token::Paren) | token::OpenDelim(token::Brace) |
-            token::DotDotDot | token::DotDotEq | token::DotDot |
-            token::ModSep | token::Not => false,
-            _ => true,
-        })
-    }
-
     /// Is the current token suitable as the start of a range patterns end?
     fn is_pat_range_end_start(&self) -> bool {
         self.token.is_path_start() // e.g. `MY_CONST`;
@@ -563,6 +636,30 @@ impl<'a> Parser<'a> {
         }
     }
 
+    /// Is this the start of a pattern beginning with a path?
+    fn is_start_of_pat_with_path(&mut self) -> bool {
+        self.check_path()
+        // Just for recovery (see `can_be_ident`).
+        || self.token.is_ident() && !self.token.is_bool_lit() && !self.token.is_keyword(kw::In)
+    }
+
+    /// Would `parse_pat_ident` be appropriate here?
+    fn can_be_ident_pat(&mut self) -> bool {
+        self.check_ident()
+        && !self.token.is_bool_lit() // Avoid `true` or `false` as a binding as it is a literal.
+        && !self.token.is_path_segment_keyword() // Avoid e.g. `Self` as it is a path.
+        // Avoid `in`. Due to recovery in the list parser this messes with `for ( $pat in $expr )`.
+        && !self.token.is_keyword(kw::In)
+        && self.look_ahead(1, |t| match t.kind { // Try to do something more complex?
+            token::OpenDelim(token::Paren) // A tuple struct pattern.
+            | token::OpenDelim(token::Brace) // A struct pattern.
+            | token::DotDotDot | token::DotDotEq | token::DotDot // A range pattern.
+            | token::ModSep // A tuple / struct variant pattern.
+            | token::Not => false, // A macro expanding to a pattern.
+            _ => true,
+        })
+    }
+
     /// Parses `ident` or `ident @ pat`.
     /// Used by the copy foo and ref foo patterns to give a good
     /// error message when parsing mistakes like `ref foo(a, b)`.

src/libsyntax/parse/parser/path.rs

@@ -423,7 +423,7 @@ impl<'a> Parser<'a> {
                     // FIXME(const_generics): to distinguish between idents for types and consts,
                     // we should introduce a GenericArg::Ident in the AST and distinguish when
                     // lowering to the HIR. For now, idents for const args are not permitted.
-                    if self.token.is_keyword(kw::True) || self.token.is_keyword(kw::False) {
+                    if self.token.is_bool_lit() {
                         self.parse_literal_maybe_minus()?
                     } else {
                         return Err(

src/libsyntax/parse/token.rs

@@ -409,7 +409,7 @@ impl Token {
     crate fn expect_lit(&self) -> Lit {
         match self.kind {
             Literal(lit) => lit,
-            _=> panic!("`expect_lit` called on non-literal"),
+            _ => panic!("`expect_lit` called on non-literal"),
         }
     }
 
@@ -417,10 +417,8 @@ impl Token {
     /// for example a '-42', or one of the boolean idents).
     crate fn can_begin_literal_or_bool(&self) -> bool {
         match self.kind {
-            Literal(..)  => true,
-            BinOp(Minus) => true,
-            Ident(name, false) if name == kw::True => true,
-            Ident(name, false) if name == kw::False => true,
+            Literal(..) | BinOp(Minus) => true,
+            Ident(name, false) if name.is_bool_lit() => true,
             Interpolated(ref nt) => match **nt {
                 NtLiteral(..) => true,
                 _             => false,
@@ -457,6 +455,7 @@ impl Token {
     pub fn is_ident(&self) -> bool {
         self.ident().is_some()
     }
+
     /// Returns `true` if the token is a lifetime.
     crate fn is_lifetime(&self) -> bool {
         self.lifetime().is_some()
@@ -508,45 +507,43 @@ impl Token {
 
     /// Returns `true` if the token is a given keyword, `kw`.
     pub fn is_keyword(&self, kw: Symbol) -> bool {
-        self.ident().map(|(id, is_raw)| id.name == kw && !is_raw).unwrap_or(false)
+        self.is_non_raw_ident_where(|id| id.name == kw)
     }
 
     crate fn is_path_segment_keyword(&self) -> bool {
-        match self.ident() {
-            Some((id, false)) => id.is_path_segment_keyword(),
-            _ => false,
-        }
+        self.is_non_raw_ident_where(ast::Ident::is_path_segment_keyword)
     }
 
     // Returns true for reserved identifiers used internally for elided lifetimes,
     // unnamed method parameters, crate root module, error recovery etc.
     crate fn is_special_ident(&self) -> bool {
-        match self.ident() {
-            Some((id, false)) => id.is_special(),
-            _ => false,
-        }
+        self.is_non_raw_ident_where(ast::Ident::is_special)
     }
 
     /// Returns `true` if the token is a keyword used in the language.
     crate fn is_used_keyword(&self) -> bool {
-        match self.ident() {
-            Some((id, false)) => id.is_used_keyword(),
-            _ => false,
-        }
+        self.is_non_raw_ident_where(ast::Ident::is_used_keyword)
     }
 
     /// Returns `true` if the token is a keyword reserved for possible future use.
     crate fn is_unused_keyword(&self) -> bool {
-        match self.ident() {
-            Some((id, false)) => id.is_unused_keyword(),
-            _ => false,
-        }
+        self.is_non_raw_ident_where(ast::Ident::is_unused_keyword)
     }
 
     /// Returns `true` if the token is either a special identifier or a keyword.
     pub fn is_reserved_ident(&self) -> bool {
+        self.is_non_raw_ident_where(ast::Ident::is_reserved)
+    }
+
+    /// Returns `true` if the token is the identifier `true` or `false`.
+    crate fn is_bool_lit(&self) -> bool {
+        self.is_non_raw_ident_where(|id| id.name.is_bool_lit())
+    }
+
+    /// Returns `true` if the token is a non-raw identifier for which `pred` holds.
+    fn is_non_raw_ident_where(&self, pred: impl FnOnce(ast::Ident) -> bool) -> bool {
         match self.ident() {
-            Some((id, false)) => id.is_reserved(),
+            Some((id, false)) => pred(id),
             _ => false,
         }
     }

src/libsyntax_pos/symbol.rs

@@ -1083,6 +1083,11 @@ impl Symbol {
         self == kw::DollarCrate
     }
 
+    /// Returns `true` if the symbol is `true` or `false`.
+    pub fn is_bool_lit(self) -> bool {
+        self == kw::True || self == kw::False
+    }
+
     /// This symbol can be a raw identifier.
     pub fn can_be_raw(self) -> bool {
         self != kw::Invalid && self != kw::Underscore && !self.is_path_segment_keyword()

src/test/ui/keyword/extern/keyword-extern-as-identifier-pat.rs

@@ -1,3 +1,3 @@
 fn main() {
-    let extern = 0; //~ ERROR expected pattern, found keyword `extern`
+    let extern = 0; //~ ERROR expected identifier, found keyword `extern`
 }

src/test/ui/keyword/extern/keyword-extern-as-identifier-pat.stderr

@@ -1,8 +1,12 @@
-error: expected pattern, found keyword `extern`
+error: expected identifier, found keyword `extern`
   --> $DIR/keyword-extern-as-identifier-pat.rs:2:9
    |
 LL |     let extern = 0;
-   |         ^^^^^^ expected pattern
+   |         ^^^^^^ expected identifier, found keyword
+help: you can escape reserved keywords to use them as identifiers
+   |
+LL |     let r#extern = 0;
+   |         ^^^^^^^^
 
 error: aborting due to previous error
 

src/test/ui/lang-item-missing-generator.stderr

@@ -1,4 +1,8 @@
 error: requires `generator` lang_item
+  --> $DIR/lang-item-missing-generator.rs:15:17
+   |
+LL | pub fn abc() -> impl FnOnce(f32) {
+   |                 ^^^^^^^^^^^^^^^^
 
 error: aborting due to previous error
 

src/test/ui/or-patterns/while-parsing-this-or-pattern.rs

@@ -3,7 +3,7 @@
 fn main() {
     match Some(42) {
         Some(42) | .=. => {} //~ ERROR expected pattern, found `.`
-        //~^ while parsing this or-pattern staring here
+        //~^ while parsing this or-pattern starting here
         //~| NOTE expected pattern
     }
 }

src/test/ui/or-patterns/while-parsing-this-or-pattern.stderr

@@ -4,7 +4,7 @@ error: expected pattern, found `.`
 LL |         Some(42) | .=. => {}
    |         --------   ^ expected pattern
    |         |
-   |         while parsing this or-pattern staring here
+   |         while parsing this or-pattern starting here
 
 error: aborting due to previous error
 

src/test/ui/parser/issue-32501.rs

@@ -4,5 +4,6 @@ fn main() {
     let _ = 0;
     let mut b = 0;
     let mut _b = 0;
-    let mut _ = 0; //~ ERROR expected identifier, found reserved identifier `_`
+    let mut _ = 0;
+    //~^ ERROR `mut` must be followed by a named binding
 }

src/test/ui/parser/issue-32501.stderr

@@ -1,8 +1,10 @@
-error: expected identifier, found reserved identifier `_`
-  --> $DIR/issue-32501.rs:7:13
+error: `mut` must be followed by a named binding
+  --> $DIR/issue-32501.rs:7:9
    |
 LL |     let mut _ = 0;
-   |             ^ expected identifier, found reserved identifier
+   |         ^^^^^ help: remove the `mut` prefix: `_`
+   |
+   = note: `mut` may be followed by `variable` and `variable @ pattern`
 
 error: aborting due to previous error
 

src/test/ui/parser/keyword-abstract.rs

@@ -1,3 +1,3 @@
 fn main() {
-    let abstract = (); //~ ERROR expected pattern, found reserved keyword `abstract`
+    let abstract = (); //~ ERROR expected identifier, found reserved keyword `abstract`
 }

src/test/ui/parser/keyword-abstract.stderr

@@ -1,8 +1,12 @@
-error: expected pattern, found reserved keyword `abstract`
+error: expected identifier, found reserved keyword `abstract`
   --> $DIR/keyword-abstract.rs:2:9
    |
 LL |     let abstract = ();
-   |         ^^^^^^^^ expected pattern
+   |         ^^^^^^^^ expected identifier, found reserved keyword
+help: you can escape reserved keywords to use them as identifiers
+   |
+LL |     let r#abstract = ();
+   |         ^^^^^^^^^^
 
 error: aborting due to previous error
 

src/test/ui/parser/keyword-as-as-identifier.rs

@@ -1,5 +1,5 @@
 // This file was auto-generated using 'src/etc/generate-keyword-tests.py as'
 
 fn main() {
-    let as = "foo"; //~ error: expected pattern, found keyword `as`
+    let as = "foo"; //~ error: expected identifier, found keyword `as`
 }

src/test/ui/parser/keyword-as-as-identifier.stderr

@@ -1,8 +1,12 @@
-error: expected pattern, found keyword `as`
+error: expected identifier, found keyword `as`
   --> $DIR/keyword-as-as-identifier.rs:4:9
    |
 LL |     let as = "foo";
-   |         ^^ expected pattern
+   |         ^^ expected identifier, found keyword
+help: you can escape reserved keywords to use them as identifiers
+   |
+LL |     let r#as = "foo";
+   |         ^^^^
 
 error: aborting due to previous error
 

src/test/ui/parser/keyword-break-as-identifier.rs

@@ -1,5 +1,5 @@
 // This file was auto-generated using 'src/etc/generate-keyword-tests.py break'
 
 fn main() {
-    let break = "foo"; //~ error: expected pattern, found keyword `break`
+    let break = "foo"; //~ error: expected identifier, found keyword `break`
 }

src/test/ui/parser/keyword-break-as-identifier.stderr

@@ -1,8 +1,12 @@
-error: expected pattern, found keyword `break`
+error: expected identifier, found keyword `break`
   --> $DIR/keyword-break-as-identifier.rs:4:9
    |
 LL |     let break = "foo";
-   |         ^^^^^ expected pattern
+   |         ^^^^^ expected identifier, found keyword
+help: you can escape reserved keywords to use them as identifiers
+   |
+LL |     let r#break = "foo";
+   |         ^^^^^^^
 
 error: aborting due to previous error
 

src/test/ui/parser/keyword-const-as-identifier.rs

@@ -1,5 +1,5 @@
 // This file was auto-generated using 'src/etc/generate-keyword-tests.py const'
 
 fn main() {
-    let const = "foo"; //~ error: expected pattern, found keyword `const`
+    let const = "foo"; //~ error: expected identifier, found keyword `const`
 }

src/test/ui/parser/keyword-const-as-identifier.stderr

@@ -1,8 +1,12 @@
-error: expected pattern, found keyword `const`
+error: expected identifier, found keyword `const`
   --> $DIR/keyword-const-as-identifier.rs:4:9
    |
 LL |     let const = "foo";
-   |         ^^^^^ expected pattern
+   |         ^^^^^ expected identifier, found keyword
+help: you can escape reserved keywords to use them as identifiers
+   |
+LL |     let r#const = "foo";
+   |         ^^^^^^^
 
 error: aborting due to previous error
 

src/test/ui/parser/keyword-continue-as-identifier.rs

@@ -1,5 +1,5 @@
 // This file was auto-generated using 'src/etc/generate-keyword-tests.py continue'
 
 fn main() {
-    let continue = "foo"; //~ error: expected pattern, found keyword `continue`
+    let continue = "foo"; //~ error: expected identifier, found keyword `continue`
 }

src/test/ui/parser/keyword-continue-as-identifier.stderr

@@ -1,8 +1,12 @@
-error: expected pattern, found keyword `continue`
+error: expected identifier, found keyword `continue`
   --> $DIR/keyword-continue-as-identifier.rs:4:9
    |
 LL |     let continue = "foo";
-   |         ^^^^^^^^ expected pattern
+   |         ^^^^^^^^ expected identifier, found keyword
+help: you can escape reserved keywords to use them as identifiers
+   |
+LL |     let r#continue = "foo";
+   |         ^^^^^^^^^^
 
 error: aborting due to previous error
 

src/test/ui/parser/keyword-else-as-identifier.rs

@@ -1,5 +1,5 @@
 // This file was auto-generated using 'src/etc/generate-keyword-tests.py else'
 
 fn main() {
-    let else = "foo"; //~ error: expected pattern, found keyword `else`
+    let else = "foo"; //~ error: expected identifier, found keyword `else`
 }

src/test/ui/parser/keyword-else-as-identifier.stderr

@@ -1,8 +1,12 @@
-error: expected pattern, found keyword `else`
+error: expected identifier, found keyword `else`
   --> $DIR/keyword-else-as-identifier.rs:4:9
    |
 LL |     let else = "foo";
-   |         ^^^^ expected pattern
+   |         ^^^^ expected identifier, found keyword
+help: you can escape reserved keywords to use them as identifiers
+   |
+LL |     let r#else = "foo";
+   |         ^^^^^^
 
 error: aborting due to previous error
 

src/test/ui/parser/keyword-enum-as-identifier.rs

@@ -1,5 +1,5 @@
 // This file was auto-generated using 'src/etc/generate-keyword-tests.py enum'
 
 fn main() {
-    let enum = "foo"; //~ error: expected pattern, found keyword `enum`
+    let enum = "foo"; //~ error: expected identifier, found keyword `enum`
 }

src/test/ui/parser/keyword-enum-as-identifier.stderr

@@ -1,8 +1,12 @@
-error: expected pattern, found keyword `enum`
+error: expected identifier, found keyword `enum`
   --> $DIR/keyword-enum-as-identifier.rs:4:9
    |
 LL |     let enum = "foo";
-   |         ^^^^ expected pattern
+   |         ^^^^ expected identifier, found keyword
+help: you can escape reserved keywords to use them as identifiers
+   |
+LL |     let r#enum = "foo";
+   |         ^^^^^^
 
 error: aborting due to previous error
 

src/test/ui/parser/keyword-final.rs

@@ -1,3 +1,3 @@
 fn main() {
-    let final = (); //~ ERROR expected pattern, found reserved keyword `final`
+    let final = (); //~ ERROR expected identifier, found reserved keyword `final`
 }

src/test/ui/parser/keyword-final.stderr

@@ -1,8 +1,12 @@
-error: expected pattern, found reserved keyword `final`
+error: expected identifier, found reserved keyword `final`
   --> $DIR/keyword-final.rs:2:9
    |
 LL |     let final = ();
-   |         ^^^^^ expected pattern
+   |         ^^^^^ expected identifier, found reserved keyword
+help: you can escape reserved keywords to use them as identifiers
+   |
+LL |     let r#final = ();
+   |         ^^^^^^^
 
 error: aborting due to previous error
 

src/test/ui/parser/keyword-fn-as-identifier.rs

@@ -1,5 +1,5 @@
 // This file was auto-generated using 'src/etc/generate-keyword-tests.py fn'
 
 fn main() {
-    let fn = "foo"; //~ error: expected pattern, found keyword `fn`
+    let fn = "foo"; //~ error: expected identifier, found keyword `fn`
 }

src/test/ui/parser/keyword-fn-as-identifier.stderr

@@ -1,8 +1,12 @@
-error: expected pattern, found keyword `fn`
+error: expected identifier, found keyword `fn`
   --> $DIR/keyword-fn-as-identifier.rs:4:9
    |
 LL |     let fn = "foo";
-   |         ^^ expected pattern
+   |         ^^ expected identifier, found keyword
+help: you can escape reserved keywords to use them as identifiers
+   |
+LL |     let r#fn = "foo";
+   |         ^^^^
 
 error: aborting due to previous error
 

src/test/ui/parser/keyword-for-as-identifier.rs

@@ -1,5 +1,5 @@
 // This file was auto-generated using 'src/etc/generate-keyword-tests.py for'
 
 fn main() {
-    let for = "foo"; //~ error: expected pattern, found keyword `for`
+    let for = "foo"; //~ error: expected identifier, found keyword `for`
 }

src/test/ui/parser/keyword-for-as-identifier.stderr

@@ -1,8 +1,12 @@
-error: expected pattern, found keyword `for`
+error: expected identifier, found keyword `for`
   --> $DIR/keyword-for-as-identifier.rs:4:9
    |
 LL |     let for = "foo";
-   |         ^^^ expected pattern
+   |         ^^^ expected identifier, found keyword
+help: you can escape reserved keywords to use them as identifiers
+   |
+LL |     let r#for = "foo";
+   |         ^^^^^
 
 error: aborting due to previous error
 

src/test/ui/parser/keyword-if-as-identifier.rs

@@ -1,5 +1,5 @@
 // This file was auto-generated using 'src/etc/generate-keyword-tests.py if'
 
 fn main() {
-    let if = "foo"; //~ error: expected pattern, found keyword `if`
+    let if = "foo"; //~ error: expected identifier, found keyword `if`
 }

src/test/ui/parser/keyword-if-as-identifier.stderr

@@ -1,8 +1,12 @@
-error: expected pattern, found keyword `if`
+error: expected identifier, found keyword `if`
   --> $DIR/keyword-if-as-identifier.rs:4:9
    |
 LL |     let if = "foo";
-   |         ^^ expected pattern
+   |         ^^ expected identifier, found keyword
+help: you can escape reserved keywords to use them as identifiers
+   |
+LL |     let r#if = "foo";
+   |         ^^^^
 
 error: aborting due to previous error
 

src/test/ui/parser/keyword-impl-as-identifier.rs

@@ -1,5 +1,5 @@
 // This file was auto-generated using 'src/etc/generate-keyword-tests.py impl'
 
 fn main() {
-    let impl = "foo"; //~ error: expected pattern, found keyword `impl`
+    let impl = "foo"; //~ error: expected identifier, found keyword `impl`
 }

src/test/ui/parser/keyword-impl-as-identifier.stderr

@@ -1,8 +1,12 @@
-error: expected pattern, found keyword `impl`
+error: expected identifier, found keyword `impl`
   --> $DIR/keyword-impl-as-identifier.rs:4:9
    |
 LL |     let impl = "foo";
-   |         ^^^^ expected pattern
+   |         ^^^^ expected identifier, found keyword
+help: you can escape reserved keywords to use them as identifiers
+   |
+LL |     let r#impl = "foo";
+   |         ^^^^^^
 
 error: aborting due to previous error
 

src/test/ui/parser/keyword-let-as-identifier.rs

@@ -1,5 +1,5 @@
 // This file was auto-generated using 'src/etc/generate-keyword-tests.py let'
 
 fn main() {
-    let let = "foo"; //~ error: expected pattern, found keyword `let`
+    let let = "foo"; //~ error: expected identifier, found keyword `let`
 }

src/test/ui/parser/keyword-let-as-identifier.stderr

@@ -1,8 +1,12 @@
-error: expected pattern, found keyword `let`
+error: expected identifier, found keyword `let`
   --> $DIR/keyword-let-as-identifier.rs:4:9
    |
 LL |     let let = "foo";
-   |         ^^^ expected pattern
+   |         ^^^ expected identifier, found keyword
+help: you can escape reserved keywords to use them as identifiers
+   |
+LL |     let r#let = "foo";
+   |         ^^^^^
 
 error: aborting due to previous error
 

src/test/ui/parser/keyword-loop-as-identifier.rs

@@ -1,5 +1,5 @@
 // This file was auto-generated using 'src/etc/generate-keyword-tests.py loop'
 
 fn main() {
-    let loop = "foo"; //~ error: expected pattern, found keyword `loop`
+    let loop = "foo"; //~ error: expected identifier, found keyword `loop`
 }

src/test/ui/parser/keyword-loop-as-identifier.stderr

@@ -1,8 +1,12 @@
-error: expected pattern, found keyword `loop`
+error: expected identifier, found keyword `loop`
   --> $DIR/keyword-loop-as-identifier.rs:4:9
    |
 LL |     let loop = "foo";
-   |         ^^^^ expected pattern
+   |         ^^^^ expected identifier, found keyword
+help: you can escape reserved keywords to use them as identifiers
+   |
+LL |     let r#loop = "foo";
+   |         ^^^^^^
 
 error: aborting due to previous error
 

src/test/ui/parser/keyword-match-as-identifier.rs

@@ -1,5 +1,5 @@
 // This file was auto-generated using 'src/etc/generate-keyword-tests.py match'
 
 fn main() {
-    let match = "foo"; //~ error: expected pattern, found keyword `match`
+    let match = "foo"; //~ error: expected identifier, found keyword `match`
 }

src/test/ui/parser/keyword-match-as-identifier.stderr

@@ -1,8 +1,12 @@
-error: expected pattern, found keyword `match`
+error: expected identifier, found keyword `match`
   --> $DIR/keyword-match-as-identifier.rs:4:9
    |
 LL |     let match = "foo";
-   |         ^^^^^ expected pattern
+   |         ^^^^^ expected identifier, found keyword
+help: you can escape reserved keywords to use them as identifiers
+   |
+LL |     let r#match = "foo";
+   |         ^^^^^^^
 
 error: aborting due to previous error
 

src/test/ui/parser/keyword-mod-as-identifier.rs

@@ -1,5 +1,5 @@
 // This file was auto-generated using 'src/etc/generate-keyword-tests.py mod'
 
 fn main() {
-    let mod = "foo"; //~ error: expected pattern, found keyword `mod`
+    let mod = "foo"; //~ error: expected identifier, found keyword `mod`
 }

src/test/ui/parser/keyword-mod-as-identifier.stderr

@@ -1,8 +1,12 @@
-error: expected pattern, found keyword `mod`
+error: expected identifier, found keyword `mod`
   --> $DIR/keyword-mod-as-identifier.rs:4:9
    |
 LL |     let mod = "foo";
-   |         ^^^ expected pattern
+   |         ^^^ expected identifier, found keyword
+help: you can escape reserved keywords to use them as identifiers
+   |
+LL |     let r#mod = "foo";
+   |         ^^^^^
 
 error: aborting due to previous error
 

src/test/ui/parser/keyword-move-as-identifier.rs

@@ -1,5 +1,5 @@
 // This file was auto-generated using 'src/etc/generate-keyword-tests.py move'
 
 fn main() {
-    let move = "foo"; //~ error: expected pattern, found keyword `move`
+    let move = "foo"; //~ error: expected identifier, found keyword `move`
 }

src/test/ui/parser/keyword-move-as-identifier.stderr

@@ -1,8 +1,12 @@
-error: expected pattern, found keyword `move`
+error: expected identifier, found keyword `move`
   --> $DIR/keyword-move-as-identifier.rs:4:9
    |
 LL |     let move = "foo";
-   |         ^^^^ expected pattern
+   |         ^^^^ expected identifier, found keyword
+help: you can escape reserved keywords to use them as identifiers
+   |
+LL |     let r#move = "foo";
+   |         ^^^^^^
 
 error: aborting due to previous error
 

src/test/ui/parser/keyword-override.rs

@@ -1,3 +1,3 @@
 fn main() {
-    let override = (); //~ ERROR expected pattern, found reserved keyword `override`
+    let override = (); //~ ERROR expected identifier, found reserved keyword `override`
 }

src/test/ui/parser/keyword-override.stderr

@@ -1,8 +1,12 @@
-error: expected pattern, found reserved keyword `override`
+error: expected identifier, found reserved keyword `override`
   --> $DIR/keyword-override.rs:2:9
    |
 LL |     let override = ();
-   |         ^^^^^^^^ expected pattern
+   |         ^^^^^^^^ expected identifier, found reserved keyword
+help: you can escape reserved keywords to use them as identifiers
+   |
+LL |     let r#override = ();
+   |         ^^^^^^^^^^
 
 error: aborting due to previous error
 

src/test/ui/parser/keyword-pub-as-identifier.rs

@@ -1,5 +1,5 @@
 // This file was auto-generated using 'src/etc/generate-keyword-tests.py pub'
 
 fn main() {
-    let pub = "foo"; //~ error: expected pattern, found keyword `pub`
+    let pub = "foo"; //~ error: expected identifier, found keyword `pub`
 }

src/test/ui/parser/keyword-pub-as-identifier.stderr

@@ -1,8 +1,12 @@
-error: expected pattern, found keyword `pub`
+error: expected identifier, found keyword `pub`
   --> $DIR/keyword-pub-as-identifier.rs:4:9
    |
 LL |     let pub = "foo";
-   |         ^^^ expected pattern
+   |         ^^^ expected identifier, found keyword
+help: you can escape reserved keywords to use them as identifiers
+   |
+LL |     let r#pub = "foo";
+   |         ^^^^^
 
 error: aborting due to previous error
 

src/test/ui/parser/keyword-return-as-identifier.rs

@@ -1,5 +1,5 @@
 // This file was auto-generated using 'src/etc/generate-keyword-tests.py return'
 
 fn main() {
-    let return = "foo"; //~ error: expected pattern, found keyword `return`
+    let return = "foo"; //~ error: expected identifier, found keyword `return`
 }

src/test/ui/parser/keyword-return-as-identifier.stderr

@@ -1,8 +1,12 @@
-error: expected pattern, found keyword `return`
+error: expected identifier, found keyword `return`
   --> $DIR/keyword-return-as-identifier.rs:4:9
    |
 LL |     let return = "foo";
-   |         ^^^^^^ expected pattern
+   |         ^^^^^^ expected identifier, found keyword
+help: you can escape reserved keywords to use them as identifiers
+   |
+LL |     let r#return = "foo";
+   |         ^^^^^^^^
 
 error: aborting due to previous error
 

src/test/ui/parser/keyword-static-as-identifier.rs

@@ -1,5 +1,5 @@
 // This file was auto-generated using 'src/etc/generate-keyword-tests.py static'
 
 fn main() {
-    let static = "foo"; //~ error: expected pattern, found keyword `static`
+    let static = "foo"; //~ error: expected identifier, found keyword `static`
 }

src/test/ui/parser/keyword-static-as-identifier.stderr

@@ -1,8 +1,12 @@
-error: expected pattern, found keyword `static`
+error: expected identifier, found keyword `static`
   --> $DIR/keyword-static-as-identifier.rs:4:9
    |
 LL |     let static = "foo";
-   |         ^^^^^^ expected pattern
+   |         ^^^^^^ expected identifier, found keyword
+help: you can escape reserved keywords to use them as identifiers
+   |
+LL |     let r#static = "foo";
+   |         ^^^^^^^^
 
 error: aborting due to previous error
 

src/test/ui/parser/keyword-struct-as-identifier.rs

@@ -1,5 +1,5 @@
 // This file was auto-generated using 'src/etc/generate-keyword-tests.py struct'
 
 fn main() {
-    let struct = "foo"; //~ error: expected pattern, found keyword `struct`
+    let struct = "foo"; //~ error: expected identifier, found keyword `struct`
 }

src/test/ui/parser/keyword-struct-as-identifier.stderr

@@ -1,8 +1,12 @@
-error: expected pattern, found keyword `struct`
+error: expected identifier, found keyword `struct`
   --> $DIR/keyword-struct-as-identifier.rs:4:9
    |
 LL |     let struct = "foo";
-   |         ^^^^^^ expected pattern
+   |         ^^^^^^ expected identifier, found keyword
+help: you can escape reserved keywords to use them as identifiers
+   |
+LL |     let r#struct = "foo";
+   |         ^^^^^^^^
 
 error: aborting due to previous error
 

src/test/ui/parser/keyword-trait-as-identifier.rs

@@ -1,5 +1,5 @@
 // This file was auto-generated using 'src/etc/generate-keyword-tests.py trait'
 
 fn main() {
-    let trait = "foo"; //~ error: expected pattern, found keyword `trait`
+    let trait = "foo"; //~ error: expected identifier, found keyword `trait`
 }

src/test/ui/parser/keyword-trait-as-identifier.stderr

@@ -1,8 +1,12 @@
-error: expected pattern, found keyword `trait`
+error: expected identifier, found keyword `trait`
   --> $DIR/keyword-trait-as-identifier.rs:4:9
    |
 LL |     let trait = "foo";
-   |         ^^^^^ expected pattern
+   |         ^^^^^ expected identifier, found keyword
+help: you can escape reserved keywords to use them as identifiers
+   |
+LL |     let r#trait = "foo";
+   |         ^^^^^^^
 
 error: aborting due to previous error
 

src/test/ui/parser/keyword-try-as-identifier-edition2018.rs

@@ -1,5 +1,5 @@
 // compile-flags: --edition 2018
 
 fn main() {
-    let try = "foo"; //~ error: expected pattern, found reserved keyword `try`
+    let try = "foo"; //~ error: expected identifier, found reserved keyword `try`
 }

src/test/ui/parser/keyword-try-as-identifier-edition2018.stderr

@@ -1,8 +1,12 @@
-error: expected pattern, found reserved keyword `try`
+error: expected identifier, found reserved keyword `try`
   --> $DIR/keyword-try-as-identifier-edition2018.rs:4:9
    |
 LL |     let try = "foo";
-   |         ^^^ expected pattern
+   |         ^^^ expected identifier, found reserved keyword
+help: you can escape reserved keywords to use them as identifiers
+   |
+LL |     let r#try = "foo";
+   |         ^^^^^
 
 error: aborting due to previous error
 

src/test/ui/parser/keyword-type-as-identifier.rs

@@ -1,5 +1,5 @@
 // This file was auto-generated using 'src/etc/generate-keyword-tests.py type'
 
 fn main() {
-    let type = "foo"; //~ error: expected pattern, found keyword `type`
+    let type = "foo"; //~ error: expected identifier, found keyword `type`
 }

src/test/ui/parser/keyword-type-as-identifier.stderr

@@ -1,8 +1,12 @@
-error: expected pattern, found keyword `type`
+error: expected identifier, found keyword `type`
   --> $DIR/keyword-type-as-identifier.rs:4:9
    |
 LL |     let type = "foo";
-   |         ^^^^ expected pattern
+   |         ^^^^ expected identifier, found keyword
+help: you can escape reserved keywords to use them as identifiers
+   |
+LL |     let r#type = "foo";
+   |         ^^^^^^
 
 error: aborting due to previous error
 

src/test/ui/parser/keyword-typeof.rs

@@ -1,3 +1,3 @@
 fn main() {
-    let typeof = (); //~ ERROR expected pattern, found reserved keyword `typeof`
+    let typeof = (); //~ ERROR expected identifier, found reserved keyword `typeof`
 }

src/test/ui/parser/keyword-typeof.stderr

@@ -1,8 +1,12 @@
-error: expected pattern, found reserved keyword `typeof`
+error: expected identifier, found reserved keyword `typeof`
   --> $DIR/keyword-typeof.rs:2:9
    |
 LL |     let typeof = ();
-   |         ^^^^^^ expected pattern
+   |         ^^^^^^ expected identifier, found reserved keyword
+help: you can escape reserved keywords to use them as identifiers
+   |
+LL |     let r#typeof = ();
+   |         ^^^^^^^^
 
 error: aborting due to previous error
 

src/test/ui/parser/keyword-unsafe-as-identifier.rs

@@ -1,5 +1,5 @@
 // This file was auto-generated using 'src/etc/generate-keyword-tests.py unsafe'
 
 fn main() {
-    let unsafe = "foo"; //~ error: expected pattern, found keyword `unsafe`
+    let unsafe = "foo"; //~ error: expected identifier, found keyword `unsafe`
 }

src/test/ui/parser/keyword-unsafe-as-identifier.stderr

@@ -1,8 +1,12 @@
-error: expected pattern, found keyword `unsafe`
+error: expected identifier, found keyword `unsafe`
   --> $DIR/keyword-unsafe-as-identifier.rs:4:9
    |
 LL |     let unsafe = "foo";
-   |         ^^^^^^ expected pattern
+   |         ^^^^^^ expected identifier, found keyword
+help: you can escape reserved keywords to use them as identifiers
+   |
+LL |     let r#unsafe = "foo";
+   |         ^^^^^^^^
 
 error: aborting due to previous error
 

src/test/ui/parser/keyword-use-as-identifier.rs

@@ -1,5 +1,5 @@
 // This file was auto-generated using 'src/etc/generate-keyword-tests.py use'
 
 fn main() {
-    let use = "foo"; //~ error: expected pattern, found keyword `use`
+    let use = "foo"; //~ error: expected identifier, found keyword `use`
 }

src/test/ui/parser/keyword-use-as-identifier.stderr

@@ -1,8 +1,12 @@
-error: expected pattern, found keyword `use`
+error: expected identifier, found keyword `use`
   --> $DIR/keyword-use-as-identifier.rs:4:9
    |
 LL |     let use = "foo";
-   |         ^^^ expected pattern
+   |         ^^^ expected identifier, found keyword
+help: you can escape reserved keywords to use them as identifiers
+   |
+LL |     let r#use = "foo";
+   |         ^^^^^
 
 error: aborting due to previous error
 

src/test/ui/parser/keyword-where-as-identifier.rs

@@ -1,5 +1,5 @@
 // This file was auto-generated using 'src/etc/generate-keyword-tests.py where'
 
 fn main() {
-    let where = "foo"; //~ error: expected pattern, found keyword `where`
+    let where = "foo"; //~ error: expected identifier, found keyword `where`
 }

src/test/ui/parser/keyword-where-as-identifier.stderr

@@ -1,8 +1,12 @@
-error: expected pattern, found keyword `where`
+error: expected identifier, found keyword `where`
   --> $DIR/keyword-where-as-identifier.rs:4:9
    |
 LL |     let where = "foo";
-   |         ^^^^^ expected pattern
+   |         ^^^^^ expected identifier, found keyword
+help: you can escape reserved keywords to use them as identifiers
+   |
+LL |     let r#where = "foo";
+   |         ^^^^^^^
 
 error: aborting due to previous error