Auto merge of #132603 - matthiaskrgr:rollup-ikzofgc, r=matthiaskrgr

Rollup of 6 pull requests Successful merges: - #132355 (Fix compiler panic with a large number of threads) - #132486 (No need to instantiate binder in `confirm_async_closure_candidate`) - #132544 (Use backticks instead of single quotes for library feature names in diagnostics) - #132559 (find the generic container rather than simply looking up for the assoc with const arg) - #132579 (add rustc std workspace crate sources) - #132583 (Suggest creating unary tuples when types don't match a trait) r? `@ghost` `@rustbot` modify labels: rollup
2024-11-25 08:13:41 +00:00 · 2024-11-04 17:39:34 +00:00 · 2024-11-04 17:39:34 +00:00 · 82c24eccad
commit 82c24eccad
parent 432972cae6 a4f323ce9c
140 changed files with 725 additions and 451 deletions
--- a/Cargo.lock
+++ b/Cargo.lock
@ -3196,6 +3196,18 @@ version = "0.1.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "e5c9f15eec8235d7cb775ee6f81891db79b98fd54ba1ad8fae565b88ef1ae4e2"

+[[package]]
+name = "rustc-std-workspace-alloc"
+version = "1.0.1"
+
+[[package]]
+name = "rustc-std-workspace-core"
+version = "1.0.1"
+
+[[package]]
+name = "rustc-std-workspace-std"
+version = "1.0.1"
+
 [[package]]
 name = "rustc_abi"
 version = "0.0.0"
--- a/Cargo.toml
+++ b/Cargo.toml
@ -3,6 +3,9 @@ resolver = "2"
 members = [
  "compiler/rustc",
  "src/etc/test-float-parse",
+  "src/rustc-std-workspace/rustc-std-workspace-core",
+  "src/rustc-std-workspace/rustc-std-workspace-alloc",
+  "src/rustc-std-workspace/rustc-std-workspace-std",
  "src/rustdoc-json-types",
  "src/tools/build_helper",
  "src/tools/cargotest",
--- a/compiler/rustc_hir_analysis/messages.ftl
+++ b/compiler/rustc_hir_analysis/messages.ftl
@ -311,8 +311,8 @@ hir_analysis_missing_trait_item_suggestion = implement the missing item: `{$snip

 hir_analysis_missing_trait_item_unstable = not all trait items implemented, missing: `{$missing_item_name}`
    .note = default implementation of `{$missing_item_name}` is unstable
-    .some_note = use of unstable library feature '{$feature}': {$reason}
-    .none_note = use of unstable library feature '{$feature}'
+    .some_note = use of unstable library feature `{$feature}`: {$reason}
+    .none_note = use of unstable library feature `{$feature}`

 hir_analysis_missing_type_params =
    the type {$parameterCount ->
--- a/compiler/rustc_hir_analysis/src/collect/type_of.rs
+++ b/compiler/rustc_hir_analysis/src/collect/type_of.rs
@ -175,19 +175,13 @@ fn const_arg_anon_type_of<'tcx>(tcx: TyCtxt<'tcx>, arg_hir_id: HirId, span: Span
        // arm would handle this.
        //
        // I believe this match arm is only needed for GAT but I am not 100% sure - BoxyUwU
-        Node::Ty(hir_ty @ hir::Ty { kind: TyKind::Path(QPath::TypeRelative(_, segment)), .. }) => {
+        Node::Ty(hir_ty @ hir::Ty { kind: TyKind::Path(QPath::TypeRelative(ty, segment)), .. }) => {
            // Find the Item containing the associated type so we can create an ItemCtxt.
            // Using the ItemCtxt lower the HIR for the unresolved assoc type into a
            // ty which is a fully resolved projection.
            // For the code example above, this would mean lowering `Self::Assoc<3>`
            // to a ty::Alias(ty::Projection, `<Self as Foo>::Assoc<3>`).
-            let item_def_id = tcx
-                .hir()
-                .parent_owner_iter(arg_hir_id)
-                .find(|(_, node)| matches!(node, OwnerNode::Item(_)))
-                .unwrap()
-                .0
-                .def_id;
+            let item_def_id = tcx.hir().get_parent_item(ty.hir_id).def_id;
            let ty = ItemCtxt::new(tcx, item_def_id).lower_ty(hir_ty);

            // Iterate through the generics of the projection to find the one that corresponds to
--- a/compiler/rustc_middle/src/middle/stability.rs
+++ b/compiler/rustc_middle/src/middle/stability.rs
@ -112,8 +112,8 @@ pub fn report_unstable(
    soft_handler: impl FnOnce(&'static Lint, Span, String),
 ) {
    let msg = match reason {
-        Some(r) => format!("use of unstable library feature '{feature}': {r}"),
-        None => format!("use of unstable library feature '{feature}'"),
+        Some(r) => format!("use of unstable library feature `{feature}`: {r}"),
+        None => format!("use of unstable library feature `{feature}`"),
    };

    if is_soft {
--- a/compiler/rustc_session/src/config.rs
+++ b/compiler/rustc_session/src/config.rs
@ -2466,6 +2466,10 @@ pub fn build_session_options(early_dcx: &mut EarlyDiagCtxt, matches: &getopts::M
        early_dcx.early_fatal("value for threads must be a positive non-zero integer");
    }

+    if unstable_opts.threads == parse::MAX_THREADS_CAP {
+        early_dcx.early_warn(format!("number of threads was capped at {}", parse::MAX_THREADS_CAP));
+    }
+
    let fuel = unstable_opts.fuel.is_some() || unstable_opts.print_fuel.is_some();
    if fuel && unstable_opts.threads > 1 {
        early_dcx.early_fatal("optimization fuel is incompatible with multiple threads");
--- a/compiler/rustc_session/src/options.rs
+++ b/compiler/rustc_session/src/options.rs
@ -457,10 +457,11 @@ mod desc {
        "either a boolean (`yes`, `no`, `on`, `off`, etc), or `nll` (default: `nll`)";
 }

-mod parse {
+pub mod parse {
    use std::str::FromStr;

    pub(crate) use super::*;
+    pub(crate) const MAX_THREADS_CAP: usize = 256;

    /// This is for boolean options that don't take a value and start with
    /// `no-`. This style of option is deprecated.
@ -657,7 +658,7 @@ mod parse {
    }

    pub(crate) fn parse_threads(slot: &mut usize, v: Option<&str>) -> bool {
-        match v.and_then(|s| s.parse().ok()) {
+        let ret = match v.and_then(|s| s.parse().ok()) {
            Some(0) => {
                *slot = std::thread::available_parallelism().map_or(1, NonZero::<usize>::get);
                true
@ -667,7 +668,11 @@ mod parse {
                true
            }
            None => false,
-        }
+        };
+        // We want to cap the number of threads here to avoid large numbers like 999999 and compiler panics.
+        // This solution was suggested here https://github.com/rust-lang/rust/issues/117638#issuecomment-1800925067
+        *slot = slot.clone().min(MAX_THREADS_CAP);
+        ret
    }

    /// Use this for any numeric option that has a static default.
--- a/compiler/rustc_trait_selection/src/error_reporting/traits/fulfillment_errors.rs
+++ b/compiler/rustc_trait_selection/src/error_reporting/traits/fulfillment_errors.rs
@ -471,6 +471,7 @@ impl<'a, 'tcx> TypeErrCtxt<'a, 'tcx> {
                        }

                        self.try_to_add_help_message(
+                            &root_obligation,
                            &obligation,
                            leaf_trait_predicate,
                            &mut err,
@ -2488,6 +2489,7 @@ impl<'a, 'tcx> TypeErrCtxt<'a, 'tcx> {

    fn try_to_add_help_message(
        &self,
+        root_obligation: &PredicateObligation<'tcx>,
        obligation: &PredicateObligation<'tcx>,
        trait_predicate: ty::PolyTraitPredicate<'tcx>,
        err: &mut Diag<'_>,
@ -2575,6 +2577,8 @@ impl<'a, 'tcx> TypeErrCtxt<'a, 'tcx> {
                impl_candidates.as_slice(),
                span,
            );
+
+            self.suggest_tuple_wrapping(err, root_obligation, obligation);
        }
    }

--- a/compiler/rustc_trait_selection/src/error_reporting/traits/suggestions.rs
+++ b/compiler/rustc_trait_selection/src/error_reporting/traits/suggestions.rs
@ -4452,6 +4452,41 @@ impl<'a, 'tcx> TypeErrCtxt<'a, 'tcx> {
        }
    }

+    /// If the type failed selection but the trait is implemented for `(T,)`, suggest that the user
+    /// creates a unary tuple
+    ///
+    /// This is a common gotcha when using libraries that emulate variadic functions with traits for tuples.
+    pub(super) fn suggest_tuple_wrapping(
+        &self,
+        err: &mut Diag<'_>,
+        root_obligation: &PredicateObligation<'tcx>,
+        obligation: &PredicateObligation<'tcx>,
+    ) {
+        let ObligationCauseCode::FunctionArg { arg_hir_id, .. } = obligation.cause.code() else {
+            return;
+        };
+
+        let Some(root_pred) = root_obligation.predicate.as_trait_clause() else { return };
+
+        let trait_ref = root_pred.map_bound(|root_pred| {
+            root_pred
+                .trait_ref
+                .with_self_ty(self.tcx, Ty::new_tup(self.tcx, &[root_pred.trait_ref.self_ty()]))
+        });
+
+        let obligation =
+            Obligation::new(self.tcx, obligation.cause.clone(), obligation.param_env, trait_ref);
+
+        if self.predicate_must_hold_modulo_regions(&obligation) {
+            let arg_span = self.tcx.hir().span(*arg_hir_id);
+            err.multipart_suggestion_verbose(
+                format!("use a unary tuple instead"),
+                vec![(arg_span.shrink_to_lo(), "(".into()), (arg_span.shrink_to_hi(), ",)".into())],
+                Applicability::MaybeIncorrect,
+            );
+        }
+    }
+
    pub(super) fn explain_hrtb_projection(
        &self,
        diag: &mut Diag<'_>,
--- a/compiler/rustc_trait_selection/src/traits/select/confirmation.rs
+++ b/compiler/rustc_trait_selection/src/traits/select/confirmation.rs
@ -951,18 +951,12 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
                });

                // We must additionally check that the return type impls `Future`.
-
-                // FIXME(async_closures): Investigate this before stabilization.
-                // We instantiate this binder eagerly because the `confirm_future_candidate`
-                // method doesn't support higher-ranked futures, which the `AsyncFn`
-                // traits expressly allow the user to write. To fix this correctly,
-                // we'd need to instantiate trait bounds before we get to selection,
-                // like the new trait solver does.
                let future_trait_def_id = tcx.require_lang_item(LangItem::Future, None);
-                let placeholder_output_ty = self.infcx.enter_forall_and_leak_universe(sig.output());
                nested.push(obligation.with(
                    tcx,
-                    ty::TraitRef::new(tcx, future_trait_def_id, [placeholder_output_ty]),
+                    sig.output().map_bound(|output_ty| {
+                        ty::TraitRef::new(tcx, future_trait_def_id, [output_ty])
+                    }),
                ));

                (trait_ref, Ty::from_closure_kind(tcx, ty::ClosureKind::Fn))
--- a/library/rustc-std-workspace-core/README.md
+++ b/library/rustc-std-workspace-core/README.md
@ -27,3 +27,6 @@ it'll look like

 when Cargo invokes the compiler, satisfying the implicit `extern crate core`
 directive injected by the compiler.
+
+The sources for the crates.io version can be found in
+[`src/rustc-std-workspace`](../../src/rustc-std-workspace).
--- a/src/rustc-std-workspace/README.md
+++ b/src/rustc-std-workspace/README.md
@ -0,0 +1,4 @@
+See [`library/rustc-std-workspace-core/README.md`](../../library/rustc-std-workspace-core/README.md) for context.
+
+These are the crates.io versions of these crates, as opposed to the versions
+in `library` which are the ones used inside the rustc workspace.
--- a/src/rustc-std-workspace/rustc-std-workspace-alloc/Cargo.toml
+++ b/src/rustc-std-workspace/rustc-std-workspace-alloc/Cargo.toml
@ -0,0 +1,11 @@
+[package]
+name = "rustc-std-workspace-alloc"
+version = "1.0.1"
+authors = ["Alex Crichton <alex@alexcrichton.com>"]
+edition = "2021"
+license = 'MIT/Apache-2.0'
+description = """
+crate for integration of crates.io crates into rust-lang/rust standard library workspace
+"""
+
+repository = "https://github.com/rust-lang/rust/tree/master/src/rustc-std-workspace"
--- a/src/rustc-std-workspace/rustc-std-workspace-alloc/src/lib.rs
+++ b/src/rustc-std-workspace/rustc-std-workspace-alloc/src/lib.rs
@ -0,0 +1,3 @@
+#![no_std]
+extern crate alloc as the_alloc;
+pub use the_alloc::*;
--- a/src/rustc-std-workspace/rustc-std-workspace-core/Cargo.toml
+++ b/src/rustc-std-workspace/rustc-std-workspace-core/Cargo.toml
@ -0,0 +1,11 @@
+[package]
+name = "rustc-std-workspace-core"
+version = "1.0.1"
+authors = ["Alex Crichton <alex@alexcrichton.com>"]
+edition = "2021"
+license = "MIT/Apache-2.0"
+description = """
+crate for integration of crates.io crates into rust-lang/rust standard library workspace
+"""
+
+repository = "https://github.com/rust-lang/rust/tree/master/src/rustc-std-workspace"
--- a/src/rustc-std-workspace/rustc-std-workspace-core/src/lib.rs
+++ b/src/rustc-std-workspace/rustc-std-workspace-core/src/lib.rs
@ -0,0 +1,3 @@
+#![no_std]
+extern crate core as the_core;
+pub use the_core::*;
--- a/src/rustc-std-workspace/rustc-std-workspace-std/Cargo.toml
+++ b/src/rustc-std-workspace/rustc-std-workspace-std/Cargo.toml
@ -0,0 +1,11 @@
+[package]
+name = "rustc-std-workspace-std"
+version = "1.0.1"
+authors = ["Alex Crichton <alex@alexcrichton.com>"]
+edition = "2021"
+license = "MIT/Apache-2.0"
+description = """
+crate for integration of crates.io crates into rust-lang/rust standard library workspace
+"""
+
+repository = "https://github.com/rust-lang/rust/tree/master/src/rustc-std-workspace"
--- a/src/rustc-std-workspace/rustc-std-workspace-std/src/lib.rs
+++ b/src/rustc-std-workspace/rustc-std-workspace-std/src/lib.rs
@ -0,0 +1 @@
+pub use std::*;
--- a/tests/ui-fulldeps/hash-stable-is-unstable.rs
+++ b/tests/ui-fulldeps/hash-stable-is-unstable.rs
@ -1,24 +1,25 @@
+//@ ignore-stage1 FIXME: this line can be removed once these new error messages are in stage 0 rustc
 //@ compile-flags: -Zdeduplicate-diagnostics=yes
 extern crate rustc_data_structures;
-//~^ use of unstable library feature 'rustc_private'
+//~^ use of unstable library feature `rustc_private`
 //~| NOTE: issue #27812 <https://github.com/rust-lang/rust/issues/27812> for more information
 //~| NOTE: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date
 extern crate rustc_macros;
-//~^ use of unstable library feature 'rustc_private'
+//~^ use of unstable library feature `rustc_private`
 //~| NOTE: see issue #27812 <https://github.com/rust-lang/rust/issues/27812> for more information
 //~| NOTE: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date
 extern crate rustc_query_system;
-//~^ use of unstable library feature 'rustc_private'
+//~^ use of unstable library feature `rustc_private`
 //~| NOTE: see issue #27812 <https://github.com/rust-lang/rust/issues/27812> for more information
 //~| NOTE: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date

 use rustc_macros::HashStable;
-//~^ use of unstable library feature 'rustc_private'
+//~^ use of unstable library feature `rustc_private`
 //~| NOTE: see issue #27812 <https://github.com/rust-lang/rust/issues/27812> for more information
 //~| NOTE: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date

 #[derive(HashStable)]
-//~^ use of unstable library feature 'rustc_private'
+//~^ use of unstable library feature `rustc_private`
 //~| NOTE: in this expansion of #[derive(HashStable)]
 //~| NOTE: in this expansion of #[derive(HashStable)]
 //~| NOTE: in this expansion of #[derive(HashStable)]
--- a/tests/ui-fulldeps/hash-stable-is-unstable.stderr
+++ b/tests/ui-fulldeps/hash-stable-is-unstable.stderr
@ -1,5 +1,5 @@
-error[E0658]: use of unstable library feature 'rustc_private': this crate is being loaded from the sysroot, an unstable location; did you mean to load this crate from crates.io via `Cargo.toml` instead?
-  --> $DIR/hash-stable-is-unstable.rs:2:1
+error[E0658]: use of unstable library feature `rustc_private`: this crate is being loaded from the sysroot, an unstable location; did you mean to load this crate from crates.io via `Cargo.toml` instead?
+  --> $DIR/hash-stable-is-unstable.rs:3:1
   |
 LL | extern crate rustc_data_structures;
   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
@ -8,8 +8,8 @@ LL | extern crate rustc_data_structures;
   = help: add `#![feature(rustc_private)]` to the crate attributes to enable
   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date

-error[E0658]: use of unstable library feature 'rustc_private': this crate is being loaded from the sysroot, an unstable location; did you mean to load this crate from crates.io via `Cargo.toml` instead?
-  --> $DIR/hash-stable-is-unstable.rs:6:1
+error[E0658]: use of unstable library feature `rustc_private`: this crate is being loaded from the sysroot, an unstable location; did you mean to load this crate from crates.io via `Cargo.toml` instead?
+  --> $DIR/hash-stable-is-unstable.rs:7:1
   |
 LL | extern crate rustc_macros;
   | ^^^^^^^^^^^^^^^^^^^^^^^^^^
@ -18,8 +18,8 @@ LL | extern crate rustc_macros;
   = help: add `#![feature(rustc_private)]` to the crate attributes to enable
   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date

-error[E0658]: use of unstable library feature 'rustc_private': this crate is being loaded from the sysroot, an unstable location; did you mean to load this crate from crates.io via `Cargo.toml` instead?
-  --> $DIR/hash-stable-is-unstable.rs:10:1
+error[E0658]: use of unstable library feature `rustc_private`: this crate is being loaded from the sysroot, an unstable location; did you mean to load this crate from crates.io via `Cargo.toml` instead?
+  --> $DIR/hash-stable-is-unstable.rs:11:1
   |
 LL | extern crate rustc_query_system;
   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
@ -28,8 +28,8 @@ LL | extern crate rustc_query_system;
   = help: add `#![feature(rustc_private)]` to the crate attributes to enable
   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date

-error[E0658]: use of unstable library feature 'rustc_private': this crate is being loaded from the sysroot, an unstable location; did you mean to load this crate from crates.io via `Cargo.toml` instead?
-  --> $DIR/hash-stable-is-unstable.rs:15:5
+error[E0658]: use of unstable library feature `rustc_private`: this crate is being loaded from the sysroot, an unstable location; did you mean to load this crate from crates.io via `Cargo.toml` instead?
+  --> $DIR/hash-stable-is-unstable.rs:16:5
   |
 LL | use rustc_macros::HashStable;
   |     ^^^^^^^^^^^^^^^^^^^^^^^^
@ -38,8 +38,8 @@ LL | use rustc_macros::HashStable;
   = help: add `#![feature(rustc_private)]` to the crate attributes to enable
   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date

-error[E0658]: use of unstable library feature 'rustc_private': this crate is being loaded from the sysroot, an unstable location; did you mean to load this crate from crates.io via `Cargo.toml` instead?
-  --> $DIR/hash-stable-is-unstable.rs:20:10
+error[E0658]: use of unstable library feature `rustc_private`: this crate is being loaded from the sysroot, an unstable location; did you mean to load this crate from crates.io via `Cargo.toml` instead?
+  --> $DIR/hash-stable-is-unstable.rs:21:10
   |
 LL | #[derive(HashStable)]
   |          ^^^^^^^^^^
--- a/tests/ui-fulldeps/pathless-extern-unstable.rs
+++ b/tests/ui-fulldeps/pathless-extern-unstable.rs
@ -1,9 +1,10 @@
+//@ ignore-stage1 FIXME: this line can be removed once these new error messages are in stage 0 rustc
 //@ edition:2018
 //@ compile-flags:--extern rustc_middle

 // Test that `--extern rustc_middle` fails with `rustc_private`.

 pub use rustc_middle;
-//~^ ERROR use of unstable library feature 'rustc_private'
+//~^ ERROR use of unstable library feature `rustc_private`

 fn main() {}
--- a/tests/ui-fulldeps/pathless-extern-unstable.stderr
+++ b/tests/ui-fulldeps/pathless-extern-unstable.stderr
@ -1,5 +1,5 @@
-error[E0658]: use of unstable library feature 'rustc_private': this crate is being loaded from the sysroot, an unstable location; did you mean to load this crate from crates.io via `Cargo.toml` instead?
-  --> $DIR/pathless-extern-unstable.rs:6:9
+error[E0658]: use of unstable library feature `rustc_private`: this crate is being loaded from the sysroot, an unstable location; did you mean to load this crate from crates.io via `Cargo.toml` instead?
+  --> $DIR/pathless-extern-unstable.rs:7:9
   |
 LL | pub use rustc_middle;
   |         ^^^^^^^^^^^^
--- a/tests/ui/associated-inherent-types/assoc-inherent-unstable.rs
+++ b/tests/ui/associated-inherent-types/assoc-inherent-unstable.rs
@ -4,6 +4,6 @@
 #![feature(inherent_associated_types)]
 #![allow(incomplete_features)]

-type Data = aux::Owner::Data; //~ ERROR use of unstable library feature 'data'
+type Data = aux::Owner::Data; //~ ERROR use of unstable library feature `data`

 fn main() {}
--- a/tests/ui/associated-inherent-types/assoc-inherent-unstable.stderr
+++ b/tests/ui/associated-inherent-types/assoc-inherent-unstable.stderr
@ -1,4 +1,4 @@
-error[E0658]: use of unstable library feature 'data'
+error[E0658]: use of unstable library feature `data`
  --> $DIR/assoc-inherent-unstable.rs:7:13
   |
 LL | type Data = aux::Owner::Data;
--- a/tests/ui/async-await/async-fn/edition-2015.rs
+++ b/tests/ui/async-await/async-fn/edition-2015.rs
@ -3,7 +3,7 @@ fn foo(x: impl async Fn()) -> impl async Fn() { x }
 //~| ERROR `async` trait bounds are only allowed in Rust 2018 or later
 //~| ERROR async closures are unstable
 //~| ERROR async closures are unstable
-//~| ERROR use of unstable library feature 'async_closure'
-//~| ERROR use of unstable library feature 'async_closure'
+//~| ERROR use of unstable library feature `async_closure`
+//~| ERROR use of unstable library feature `async_closure`

 fn main() {}
--- a/tests/ui/async-await/async-fn/edition-2015.stderr
+++ b/tests/ui/async-await/async-fn/edition-2015.stderr
@ -38,7 +38,7 @@ LL | fn foo(x: impl async Fn()) -> impl async Fn() { x }
   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date
   = help: to use an async block, remove the `||`: `async {`

-error[E0658]: use of unstable library feature 'async_closure'
+error[E0658]: use of unstable library feature `async_closure`
  --> $DIR/edition-2015.rs:1:42
   |
 LL | fn foo(x: impl async Fn()) -> impl async Fn() { x }
@ -48,7 +48,7 @@ LL | fn foo(x: impl async Fn()) -> impl async Fn() { x }
   = help: add `#![feature(async_closure)]` to the crate attributes to enable
   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date

-error[E0658]: use of unstable library feature 'async_closure'
+error[E0658]: use of unstable library feature `async_closure`
  --> $DIR/edition-2015.rs:1:22
   |
 LL | fn foo(x: impl async Fn()) -> impl async Fn() { x }
--- a/tests/ui/box/alloc-unstable-fail.rs
+++ b/tests/ui/box/alloc-unstable-fail.rs
@ -2,5 +2,5 @@ use std::boxed::Box;

 fn main() {
    let _boxed: Box<u32, _> = Box::new(10);
-    //~^ ERROR use of unstable library feature 'allocator_api'
+    //~^ ERROR use of unstable library feature `allocator_api`
 }
--- a/tests/ui/box/alloc-unstable-fail.stderr
+++ b/tests/ui/box/alloc-unstable-fail.stderr
@ -1,4 +1,4 @@
-error[E0658]: use of unstable library feature 'allocator_api'
+error[E0658]: use of unstable library feature `allocator_api`
  --> $DIR/alloc-unstable-fail.rs:4:26
   |
 LL |     let _boxed: Box<u32, _> = Box::new(10);
--- a/tests/ui/conditional-compilation/cfg_accessible-unstable.rs
+++ b/tests/ui/conditional-compilation/cfg_accessible-unstable.rs
@ -1,2 +1,2 @@
-#[cfg_accessible(std)] //~ ERROR use of unstable library feature 'cfg_accessible'
+#[cfg_accessible(std)] //~ ERROR use of unstable library feature `cfg_accessible`
 fn main() {}
--- a/tests/ui/conditional-compilation/cfg_accessible-unstable.stderr
+++ b/tests/ui/conditional-compilation/cfg_accessible-unstable.stderr
@ -1,4 +1,4 @@
-error[E0658]: use of unstable library feature 'cfg_accessible': `cfg_accessible` is not fully implemented
+error[E0658]: use of unstable library feature `cfg_accessible`: `cfg_accessible` is not fully implemented
  --> $DIR/cfg_accessible-unstable.rs:1:3
   |
 LL | #[cfg_accessible(std)]
--- a/tests/ui/consts/const-unstable-intrinsic.rs
+++ b/tests/ui/consts/const-unstable-intrinsic.rs
@ -15,16 +15,16 @@ const fn const_main() {
    let x = 42;
    unsafe {
        unstable_intrinsic::old_way::size_of_val(&x);
-        //~^ERROR: unstable library feature 'unstable'
+        //~^ERROR: unstable library feature `unstable`
        //~|ERROR: cannot call non-const intrinsic
        unstable_intrinsic::old_way::min_align_of_val(&x);
-        //~^ERROR: unstable library feature 'unstable'
+        //~^ERROR: unstable library feature `unstable`
        //~|ERROR: not yet stable as a const intrinsic
        unstable_intrinsic::new_way::size_of_val(&x);
-        //~^ERROR: unstable library feature 'unstable'
+        //~^ERROR: unstable library feature `unstable`
        //~|ERROR: cannot be (indirectly) exposed to stable
        unstable_intrinsic::new_way::min_align_of_val(&x);
-        //~^ERROR: unstable library feature 'unstable'
+        //~^ERROR: unstable library feature `unstable`
        //~|ERROR: not yet stable as a const intrinsic

        old_way::size_of_val(&x);
--- a/tests/ui/consts/const-unstable-intrinsic.stderr
+++ b/tests/ui/consts/const-unstable-intrinsic.stderr
@ -1,4 +1,4 @@
-error[E0658]: use of unstable library feature 'unstable'
+error[E0658]: use of unstable library feature `unstable`
  --> $DIR/const-unstable-intrinsic.rs:17:9
   |
 LL |         unstable_intrinsic::old_way::size_of_val(&x);
@ -8,7 +8,7 @@ LL |         unstable_intrinsic::old_way::size_of_val(&x);
   = help: add `#![feature(unstable)]` to the crate attributes to enable
   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date

-error[E0658]: use of unstable library feature 'unstable'
+error[E0658]: use of unstable library feature `unstable`
  --> $DIR/const-unstable-intrinsic.rs:20:9
   |
 LL |         unstable_intrinsic::old_way::min_align_of_val(&x);
@ -18,7 +18,7 @@ LL |         unstable_intrinsic::old_way::min_align_of_val(&x);
   = help: add `#![feature(unstable)]` to the crate attributes to enable
   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date

-error[E0658]: use of unstable library feature 'unstable'
+error[E0658]: use of unstable library feature `unstable`
  --> $DIR/const-unstable-intrinsic.rs:23:9
   |
 LL |         unstable_intrinsic::new_way::size_of_val(&x);
@ -28,7 +28,7 @@ LL |         unstable_intrinsic::new_way::size_of_val(&x);
   = help: add `#![feature(unstable)]` to the crate attributes to enable
   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date

-error[E0658]: use of unstable library feature 'unstable'
+error[E0658]: use of unstable library feature `unstable`
  --> $DIR/const-unstable-intrinsic.rs:26:9
   |
 LL |         unstable_intrinsic::new_way::min_align_of_val(&x);
--- a/tests/ui/derives/rustc-decodable-issue-123156.stderr
+++ b/tests/ui/derives/rustc-decodable-issue-123156.stderr
@ -1,5 +1,5 @@
 Future incompatibility report: Future breakage diagnostic:
-warning: use of unstable library feature 'rustc_encodable_decodable': derive macro for `rustc-serialize`; should not be used in new code
+warning: use of unstable library feature `rustc_encodable_decodable`: derive macro for `rustc-serialize`; should not be used in new code
  --> $DIR/rustc-decodable-issue-123156.rs:10:10
   |
 LL | #[derive(RustcDecodable)]
--- a/tests/ui/diagnostic_namespace/do_not_recommend/do_not_apply_attribute_without_feature_flag.stderr
+++ b/tests/ui/diagnostic_namespace/do_not_recommend/do_not_apply_attribute_without_feature_flag.stderr
@ -15,6 +15,10 @@ note: required by a bound in `check`
   |
 LL | fn check(a: impl Foo) {}
   |                  ^^^ required by this bound in `check`
+help: use a unary tuple instead
+   |
+LL |     check(((),));
+   |           +  ++

 error: aborting due to 1 previous error

--- a/tests/ui/diagnostic_namespace/do_not_recommend/supress_suggestions_in_help.current.stderr
+++ b/tests/ui/diagnostic_namespace/do_not_recommend/supress_suggestions_in_help.current.stderr
@ -12,6 +12,10 @@ note: required by a bound in `check`
   |
 LL | fn check(a: impl Foo) {}
   |                  ^^^ required by this bound in `check`
+help: use a unary tuple instead
+   |
+LL |     check(((),));
+   |           +  ++

 error: aborting due to 1 previous error

--- a/tests/ui/diagnostic_namespace/do_not_recommend/supress_suggestions_in_help.next.stderr
+++ b/tests/ui/diagnostic_namespace/do_not_recommend/supress_suggestions_in_help.next.stderr
@ -12,6 +12,10 @@ note: required by a bound in `check`
   |
 LL | fn check(a: impl Foo) {}
   |                  ^^^ required by this bound in `check`
+help: use a unary tuple instead
+   |
+LL |     check(((),));
+   |           +  ++

 error: aborting due to 1 previous error

--- a/tests/ui/explore-issue-38412.rs
+++ b/tests/ui/explore-issue-38412.rs
@ -18,7 +18,7 @@ fn main() {

    let Record { a_stable_pub: _, a_unstable_declared_pub: _, a_unstable_undeclared_pub: _, .. } =
        Record::new();
-    //~^^ ERROR use of unstable library feature 'unstable_undeclared'
+    //~^^ ERROR use of unstable library feature `unstable_undeclared`

    let r = Record::new();
    let t = Tuple::new();
--- a/tests/ui/explore-issue-38412.stderr
+++ b/tests/ui/explore-issue-38412.stderr
@ -1,4 +1,4 @@
-error[E0658]: use of unstable library feature 'unstable_undeclared'
+error[E0658]: use of unstable library feature `unstable_undeclared`
  --> $DIR/explore-issue-38412.rs:19:63
   |
 LL |     let Record { a_stable_pub: _, a_unstable_declared_pub: _, a_unstable_undeclared_pub: _, .. } =
@ -8,7 +8,7 @@ LL |     let Record { a_stable_pub: _, a_unstable_declared_pub: _, a_unstable_un
   = help: add `#![feature(unstable_undeclared)]` to the crate attributes to enable
   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date

-error[E0658]: use of unstable library feature 'unstable_undeclared'
+error[E0658]: use of unstable library feature `unstable_undeclared`
  --> $DIR/explore-issue-38412.rs:28:5
   |
 LL |     r.a_unstable_undeclared_pub;
@ -36,7 +36,7 @@ error[E0616]: field `d_priv` of struct `Record` is private
 LL |     r.d_priv;
   |       ^^^^^^ private field

-error[E0658]: use of unstable library feature 'unstable_undeclared'
+error[E0658]: use of unstable library feature `unstable_undeclared`
  --> $DIR/explore-issue-38412.rs:35:5
   |
 LL |     t.2;
@ -64,7 +64,7 @@ error[E0616]: field `5` of struct `pub_and_stability::Tuple` is private
 LL |     t.5;
   |       ^ private field

-error[E0658]: use of unstable library feature 'unstable_undeclared'
+error[E0658]: use of unstable library feature `unstable_undeclared`
  --> $DIR/explore-issue-38412.rs:42:7
   |
 LL |     r.unstable_undeclared_trait_method();
@ -74,7 +74,7 @@ LL |     r.unstable_undeclared_trait_method();
   = help: add `#![feature(unstable_undeclared)]` to the crate attributes to enable
   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date

-error[E0658]: use of unstable library feature 'unstable_undeclared'
+error[E0658]: use of unstable library feature `unstable_undeclared`
  --> $DIR/explore-issue-38412.rs:46:7
   |
 LL |     r.unstable_undeclared();
@ -117,7 +117,7 @@ LL |     r.private();
 LL |         fn private(&self) -> i32 { self.d_priv }
   |         ------------------------ private method defined here

-error[E0658]: use of unstable library feature 'unstable_undeclared'
+error[E0658]: use of unstable library feature `unstable_undeclared`
  --> $DIR/explore-issue-38412.rs:55:7
   |
 LL |     t.unstable_undeclared_trait_method();
@ -127,7 +127,7 @@ LL |     t.unstable_undeclared_trait_method();
   = help: add `#![feature(unstable_undeclared)]` to the crate attributes to enable
   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date

-error[E0658]: use of unstable library feature 'unstable_undeclared'
+error[E0658]: use of unstable library feature `unstable_undeclared`
  --> $DIR/explore-issue-38412.rs:59:7
   |
 LL |     t.unstable_undeclared();
--- a/tests/ui/feature-gates/bench.rs
+++ b/tests/ui/feature-gates/bench.rs
@ -1,9 +1,9 @@
 //@ edition:2018

-#[bench] //~ ERROR use of unstable library feature 'test'
+#[bench] //~ ERROR use of unstable library feature `test`
         //~| WARN this was previously accepted
 fn bench() {}

-use bench as _; //~ ERROR use of unstable library feature 'test'
+use bench as _; //~ ERROR use of unstable library feature `test`
                //~| WARN this was previously accepted
 fn main() {}
--- a/tests/ui/feature-gates/bench.stderr
+++ b/tests/ui/feature-gates/bench.stderr
@ -1,4 +1,4 @@
-error: use of unstable library feature 'test': `bench` is a part of custom test frameworks which are unstable
+error: use of unstable library feature `test`: `bench` is a part of custom test frameworks which are unstable
  --> $DIR/bench.rs:3:3
   |
 LL | #[bench]
@ -8,7 +8,7 @@ LL | #[bench]
   = note: for more information, see issue #64266 <https://github.com/rust-lang/rust/issues/64266>
   = note: `#[deny(soft_unstable)]` on by default

-error: use of unstable library feature 'test': `bench` is a part of custom test frameworks which are unstable
+error: use of unstable library feature `test`: `bench` is a part of custom test frameworks which are unstable
  --> $DIR/bench.rs:7:5
   |
 LL | use bench as _;
@ -20,7 +20,7 @@ LL | use bench as _;
 error: aborting due to 2 previous errors

 Future incompatibility report: Future breakage diagnostic:
-error: use of unstable library feature 'test': `bench` is a part of custom test frameworks which are unstable
+error: use of unstable library feature `test`: `bench` is a part of custom test frameworks which are unstable
  --> $DIR/bench.rs:3:3
   |
 LL | #[bench]
@ -31,7 +31,7 @@ LL | #[bench]
   = note: `#[deny(soft_unstable)]` on by default

 Future breakage diagnostic:
-error: use of unstable library feature 'test': `bench` is a part of custom test frameworks which are unstable
+error: use of unstable library feature `test`: `bench` is a part of custom test frameworks which are unstable
  --> $DIR/bench.rs:7:5
   |
 LL | use bench as _;
--- a/tests/ui/feature-gates/feature-gate-alloc-error-handler.rs
+++ b/tests/ui/feature-gates/feature-gate-alloc-error-handler.rs
@ -5,7 +5,7 @@

 use core::alloc::Layout;

-#[alloc_error_handler] //~ ERROR use of unstable library feature 'alloc_error_handler'
+#[alloc_error_handler] //~ ERROR use of unstable library feature `alloc_error_handler`
 fn oom(info: Layout) -> ! {
    loop {}
 }
--- a/tests/ui/feature-gates/feature-gate-alloc-error-handler.stderr
+++ b/tests/ui/feature-gates/feature-gate-alloc-error-handler.stderr
@ -1,4 +1,4 @@
-error[E0658]: use of unstable library feature 'alloc_error_handler'
+error[E0658]: use of unstable library feature `alloc_error_handler`
  --> $DIR/feature-gate-alloc-error-handler.rs:8:3
   |
 LL | #[alloc_error_handler]
--- a/tests/ui/feature-gates/feature-gate-autodiff-use.has_support.stderr
+++ b/tests/ui/feature-gates/feature-gate-autodiff-use.has_support.stderr
@ -1,4 +1,4 @@
-error[E0658]: use of unstable library feature 'autodiff'
+error[E0658]: use of unstable library feature `autodiff`
  --> $DIR/feature-gate-autodiff-use.rs:13:3
   |
 LL | #[autodiff(dfoo, Reverse)]
@ -8,7 +8,7 @@ LL | #[autodiff(dfoo, Reverse)]
   = help: add `#![feature(autodiff)]` to the crate attributes to enable
   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date

-error[E0658]: use of unstable library feature 'autodiff'
+error[E0658]: use of unstable library feature `autodiff`
  --> $DIR/feature-gate-autodiff-use.rs:9:5
   |
 LL | use std::autodiff::autodiff;
--- a/tests/ui/feature-gates/feature-gate-autodiff-use.no_support.stderr
+++ b/tests/ui/feature-gates/feature-gate-autodiff-use.no_support.stderr
@ -1,4 +1,4 @@
-error[E0658]: use of unstable library feature 'autodiff'
+error[E0658]: use of unstable library feature `autodiff`
  --> $DIR/feature-gate-autodiff-use.rs:13:3
   |
 LL | #[autodiff(dfoo, Reverse)]
@ -14,7 +14,7 @@ error: this rustc version does not support autodiff
 LL | #[autodiff(dfoo, Reverse)]
   | ^^^^^^^^^^^^^^^^^^^^^^^^^^

-error[E0658]: use of unstable library feature 'autodiff'
+error[E0658]: use of unstable library feature `autodiff`
  --> $DIR/feature-gate-autodiff-use.rs:9:5
   |
 LL | use std::autodiff::autodiff;
--- a/tests/ui/feature-gates/feature-gate-autodiff-use.rs
+++ b/tests/ui/feature-gates/feature-gate-autodiff-use.rs
@ -7,11 +7,11 @@
 #![crate_type = "lib"]

 use std::autodiff::autodiff;
-//[has_support]~^ ERROR use of unstable library feature 'autodiff'
-//[no_support]~^^ ERROR use of unstable library feature 'autodiff'
+//[has_support]~^ ERROR use of unstable library feature `autodiff`
+//[no_support]~^^ ERROR use of unstable library feature `autodiff`

 #[autodiff(dfoo, Reverse)]
-//[has_support]~^ ERROR use of unstable library feature 'autodiff' [E0658]
-//[no_support]~^^ ERROR use of unstable library feature 'autodiff' [E0658]
+//[has_support]~^ ERROR use of unstable library feature `autodiff` [E0658]
+//[no_support]~^^ ERROR use of unstable library feature `autodiff` [E0658]
 //[no_support]~| ERROR this rustc version does not support autodiff
 fn foo() {}
--- a/tests/ui/feature-gates/feature-gate-concat_bytes.rs
+++ b/tests/ui/feature-gates/feature-gate-concat_bytes.rs
@ -1,4 +1,4 @@
 fn main() {
-    let a = concat_bytes!(b'A', b"BC"); //~ ERROR use of unstable library feature 'concat_bytes'
+    let a = concat_bytes!(b'A', b"BC"); //~ ERROR use of unstable library feature `concat_bytes`
    assert_eq!(a, &[65, 66, 67]);
 }
--- a/tests/ui/feature-gates/feature-gate-concat_bytes.stderr
+++ b/tests/ui/feature-gates/feature-gate-concat_bytes.stderr
@ -1,4 +1,4 @@
-error[E0658]: use of unstable library feature 'concat_bytes'
+error[E0658]: use of unstable library feature `concat_bytes`
  --> $DIR/feature-gate-concat_bytes.rs:2:13
   |
 LL |     let a = concat_bytes!(b'A', b"BC");
--- a/tests/ui/feature-gates/feature-gate-concat_idents.stderr
+++ b/tests/ui/feature-gates/feature-gate-concat_idents.stderr
@ -1,4 +1,4 @@
-error[E0658]: use of unstable library feature 'concat_idents': `concat_idents` is not stable enough for use and is subject to change
+error[E0658]: use of unstable library feature `concat_idents`: `concat_idents` is not stable enough for use and is subject to change
  --> $DIR/feature-gate-concat_idents.rs:5:13
   |
 LL |     let a = concat_idents!(X, Y_1);
@ -8,7 +8,7 @@ LL |     let a = concat_idents!(X, Y_1);
   = help: add `#![feature(concat_idents)]` to the crate attributes to enable
   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date

-error[E0658]: use of unstable library feature 'concat_idents': `concat_idents` is not stable enough for use and is subject to change
+error[E0658]: use of unstable library feature `concat_idents`: `concat_idents` is not stable enough for use and is subject to change
  --> $DIR/feature-gate-concat_idents.rs:6:13
   |
 LL |     let b = concat_idents!(X, Y_2);
--- a/tests/ui/feature-gates/feature-gate-concat_idents2.stderr
+++ b/tests/ui/feature-gates/feature-gate-concat_idents2.stderr
@ -1,4 +1,4 @@
-error[E0658]: use of unstable library feature 'concat_idents': `concat_idents` is not stable enough for use and is subject to change
+error[E0658]: use of unstable library feature `concat_idents`: `concat_idents` is not stable enough for use and is subject to change
  --> $DIR/feature-gate-concat_idents2.rs:2:5
   |
 LL |     concat_idents!(a, b);
--- a/tests/ui/feature-gates/feature-gate-concat_idents3.stderr
+++ b/tests/ui/feature-gates/feature-gate-concat_idents3.stderr
@ -1,4 +1,4 @@
-error[E0658]: use of unstable library feature 'concat_idents': `concat_idents` is not stable enough for use and is subject to change
+error[E0658]: use of unstable library feature `concat_idents`: `concat_idents` is not stable enough for use and is subject to change
  --> $DIR/feature-gate-concat_idents3.rs:5:20
   |
 LL |     assert_eq!(10, concat_idents!(X, Y_1));
@ -8,7 +8,7 @@ LL |     assert_eq!(10, concat_idents!(X, Y_1));
   = help: add `#![feature(concat_idents)]` to the crate attributes to enable
   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date

-error[E0658]: use of unstable library feature 'concat_idents': `concat_idents` is not stable enough for use and is subject to change
+error[E0658]: use of unstable library feature `concat_idents`: `concat_idents` is not stable enough for use and is subject to change
  --> $DIR/feature-gate-concat_idents3.rs:6:20
   |
 LL |     assert_eq!(20, concat_idents!(X, Y_2));
--- a/tests/ui/feature-gates/feature-gate-custom_mir.stderr
+++ b/tests/ui/feature-gates/feature-gate-custom_mir.stderr
@ -7,7 +7,7 @@ LL | #[custom_mir(dialect = "built")]
   = help: add `#![feature(custom_mir)]` to the crate attributes to enable
   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date

-error[E0658]: use of unstable library feature 'custom_mir': MIR is an implementation detail and extremely unstable
+error[E0658]: use of unstable library feature `custom_mir`: MIR is an implementation detail and extremely unstable
  --> $DIR/feature-gate-custom_mir.rs:4:5
   |
 LL | use core::intrinsics::mir::*;
@ -16,7 +16,7 @@ LL | use core::intrinsics::mir::*;
   = help: add `#![feature(custom_mir)]` to the crate attributes to enable
   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date

-error[E0658]: use of unstable library feature 'custom_mir': MIR is an implementation detail and extremely unstable
+error[E0658]: use of unstable library feature `custom_mir`: MIR is an implementation detail and extremely unstable
  --> $DIR/feature-gate-custom_mir.rs:10:13
   |
 LL |             Return()
--- a/tests/ui/feature-gates/feature-gate-custom_test_frameworks.stderr
+++ b/tests/ui/feature-gates/feature-gate-custom_test_frameworks.stderr
@ -1,4 +1,4 @@
-error[E0658]: use of unstable library feature 'custom_test_frameworks': custom test frameworks are an unstable feature
+error[E0658]: use of unstable library feature `custom_test_frameworks`: custom test frameworks are an unstable feature
  --> $DIR/feature-gate-custom_test_frameworks.rs:3:3
   |
 LL | #[test_case]
--- a/tests/ui/feature-gates/feature-gate-derive-coerce-pointee.rs
+++ b/tests/ui/feature-gates/feature-gate-derive-coerce-pointee.rs
@ -1,6 +1,6 @@
-use std::marker::CoercePointee; //~ ERROR use of unstable library feature 'derive_coerce_pointee'
+use std::marker::CoercePointee; //~ ERROR use of unstable library feature `derive_coerce_pointee`

-#[derive(CoercePointee)] //~ ERROR use of unstable library feature 'derive_coerce_pointee'
+#[derive(CoercePointee)] //~ ERROR use of unstable library feature `derive_coerce_pointee`
 #[repr(transparent)]
 struct MyPointer<'a, #[pointee] T: ?Sized> {
    ptr: &'a T,
--- a/tests/ui/feature-gates/feature-gate-derive-coerce-pointee.stderr
+++ b/tests/ui/feature-gates/feature-gate-derive-coerce-pointee.stderr
@ -1,4 +1,4 @@
-error[E0658]: use of unstable library feature 'derive_coerce_pointee'
+error[E0658]: use of unstable library feature `derive_coerce_pointee`
  --> $DIR/feature-gate-derive-coerce-pointee.rs:3:10
   |
 LL | #[derive(CoercePointee)]
@ -8,7 +8,7 @@ LL | #[derive(CoercePointee)]
   = help: add `#![feature(derive_coerce_pointee)]` to the crate attributes to enable
   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date

-error[E0658]: use of unstable library feature 'derive_coerce_pointee'
+error[E0658]: use of unstable library feature `derive_coerce_pointee`
  --> $DIR/feature-gate-derive-coerce-pointee.rs:1:5
   |
 LL | use std::marker::CoercePointee;
--- a/tests/ui/feature-gates/feature-gate-format_args_nl.stderr
+++ b/tests/ui/feature-gates/feature-gate-format_args_nl.stderr
@ -1,4 +1,4 @@
-error[E0658]: use of unstable library feature 'format_args_nl': `format_args_nl` is only for internal language use and is subject to change
+error[E0658]: use of unstable library feature `format_args_nl`: `format_args_nl` is only for internal language use and is subject to change
  --> $DIR/feature-gate-format_args_nl.rs:2:5
   |
 LL |     format_args_nl!("");
--- a/tests/ui/feature-gates/feature-gate-log_syntax.stderr
+++ b/tests/ui/feature-gates/feature-gate-log_syntax.stderr
@ -1,4 +1,4 @@
-error[E0658]: use of unstable library feature 'log_syntax': `log_syntax!` is not stable enough for use and is subject to change
+error[E0658]: use of unstable library feature `log_syntax`: `log_syntax!` is not stable enough for use and is subject to change
  --> $DIR/feature-gate-log_syntax.rs:2:5
   |
 LL |     log_syntax!()
--- a/tests/ui/feature-gates/feature-gate-log_syntax2.stderr
+++ b/tests/ui/feature-gates/feature-gate-log_syntax2.stderr
@ -1,4 +1,4 @@
-error[E0658]: use of unstable library feature 'log_syntax': `log_syntax!` is not stable enough for use and is subject to change
+error[E0658]: use of unstable library feature `log_syntax`: `log_syntax!` is not stable enough for use and is subject to change
  --> $DIR/feature-gate-log_syntax2.rs:2:22
   |
 LL |     println!("{:?}", log_syntax!());
--- a/tests/ui/feature-gates/feature-gate-naked_functions.rs
+++ b/tests/ui/feature-gates/feature-gate-naked_functions.rs
@ -1,13 +1,13 @@
 //@ needs-asm-support

 use std::arch::naked_asm;
-//~^ ERROR use of unstable library feature 'naked_functions'
+//~^ ERROR use of unstable library feature `naked_functions`

 #[naked]
 //~^ the `#[naked]` attribute is an experimental feature
 extern "C" fn naked() {
    naked_asm!("")
-    //~^ ERROR use of unstable library feature 'naked_functions'
+    //~^ ERROR use of unstable library feature `naked_functions`
    //~| ERROR: requires unsafe
 }

@ -15,7 +15,7 @@ extern "C" fn naked() {
 //~^ the `#[naked]` attribute is an experimental feature
 extern "C" fn naked_2() -> isize {
    naked_asm!("")
-    //~^ ERROR use of unstable library feature 'naked_functions'
+    //~^ ERROR use of unstable library feature `naked_functions`
    //~| ERROR: requires unsafe
 }

--- a/tests/ui/feature-gates/feature-gate-naked_functions.stderr
+++ b/tests/ui/feature-gates/feature-gate-naked_functions.stderr
@ -1,4 +1,4 @@
-error[E0658]: use of unstable library feature 'naked_functions'
+error[E0658]: use of unstable library feature `naked_functions`
  --> $DIR/feature-gate-naked_functions.rs:9:5
   |
 LL |     naked_asm!("")
@ -8,7 +8,7 @@ LL |     naked_asm!("")
   = help: add `#![feature(naked_functions)]` to the crate attributes to enable
   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date

-error[E0658]: use of unstable library feature 'naked_functions'
+error[E0658]: use of unstable library feature `naked_functions`
  --> $DIR/feature-gate-naked_functions.rs:17:5
   |
 LL |     naked_asm!("")
@ -38,7 +38,7 @@ LL | #[naked]
   = help: add `#![feature(naked_functions)]` to the crate attributes to enable
   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date

-error[E0658]: use of unstable library feature 'naked_functions'
+error[E0658]: use of unstable library feature `naked_functions`
  --> $DIR/feature-gate-naked_functions.rs:3:5
   |
 LL | use std::arch::naked_asm;
--- a/tests/ui/feature-gates/feature-gate-rustc_encodable_decodable.rs
+++ b/tests/ui/feature-gates/feature-gate-rustc_encodable_decodable.rs
@ -5,11 +5,11 @@ extern crate rustc_serialize; //~ERROR can't find crate for `rustc_serialize`

 #[derive(
    RustcEncodable,
-    //~^   ERROR   use of unstable library feature 'rustc_encodable_decodable'
+    //~^   ERROR   use of unstable library feature `rustc_encodable_decodable`
    //~^^  WARNING this was previously accepted by the compiler
    //~^^^ WARNING use of deprecated macro `RustcEncodable`
    RustcDecodable,
-    //~^   ERROR   use of unstable library feature 'rustc_encodable_decodable'
+    //~^   ERROR   use of unstable library feature `rustc_encodable_decodable`
    //~^^  WARNING this was previously accepted by the compiler
    //~^^^ WARNING use of deprecated macro `RustcDecodable`
 )]
--- a/tests/ui/feature-gates/feature-gate-rustc_encodable_decodable.stderr
+++ b/tests/ui/feature-gates/feature-gate-rustc_encodable_decodable.stderr
@ -6,7 +6,7 @@ LL | extern crate rustc_serialize;
   |
   = help: maybe you need to install the missing components with: `rustup component add rust-src rustc-dev llvm-tools-preview`

-error: use of unstable library feature 'rustc_encodable_decodable': derive macro for `rustc-serialize`; should not be used in new code
+error: use of unstable library feature `rustc_encodable_decodable`: derive macro for `rustc-serialize`; should not be used in new code
  --> $DIR/feature-gate-rustc_encodable_decodable.rs:7:5
   |
 LL |     RustcEncodable,
@ -24,7 +24,7 @@ LL |     RustcEncodable,
   |
   = note: `#[warn(deprecated)]` on by default

-error: use of unstable library feature 'rustc_encodable_decodable': derive macro for `rustc-serialize`; should not be used in new code
+error: use of unstable library feature `rustc_encodable_decodable`: derive macro for `rustc-serialize`; should not be used in new code
  --> $DIR/feature-gate-rustc_encodable_decodable.rs:11:5
   |
 LL |     RustcDecodable,
@ -43,7 +43,7 @@ error: aborting due to 3 previous errors; 2 warnings emitted

 For more information about this error, try `rustc --explain E0463`.
 Future incompatibility report: Future breakage diagnostic:
-error: use of unstable library feature 'rustc_encodable_decodable': derive macro for `rustc-serialize`; should not be used in new code
+error: use of unstable library feature `rustc_encodable_decodable`: derive macro for `rustc-serialize`; should not be used in new code
  --> $DIR/feature-gate-rustc_encodable_decodable.rs:7:5
   |
 LL |     RustcEncodable,
@ -54,7 +54,7 @@ LL |     RustcEncodable,
   = note: `#[deny(soft_unstable)]` on by default

 Future breakage diagnostic:
-error: use of unstable library feature 'rustc_encodable_decodable': derive macro for `rustc-serialize`; should not be used in new code
+error: use of unstable library feature `rustc_encodable_decodable`: derive macro for `rustc-serialize`; should not be used in new code
  --> $DIR/feature-gate-rustc_encodable_decodable.rs:11:5
   |
 LL |     RustcDecodable,
--- a/tests/ui/feature-gates/feature-gate-trace_macros.stderr
+++ b/tests/ui/feature-gates/feature-gate-trace_macros.stderr
@ -1,4 +1,4 @@
-error[E0658]: use of unstable library feature 'trace_macros': `trace_macros` is not stable enough for use and is subject to change
+error[E0658]: use of unstable library feature `trace_macros`: `trace_macros` is not stable enough for use and is subject to change
  --> $DIR/feature-gate-trace_macros.rs:2:5
   |
 LL |     trace_macros!(true);
--- a/tests/ui/feature-gates/feature-gate-type_ascription.rs
+++ b/tests/ui/feature-gates/feature-gate-type_ascription.rs
@ -1,5 +1,5 @@
 // Type ascription is unstable

 fn main() {
-    let a = type_ascribe!(10, u8); //~ ERROR use of unstable library feature 'type_ascription': placeholder syntax for type ascription
+    let a = type_ascribe!(10, u8); //~ ERROR use of unstable library feature `type_ascription`: placeholder syntax for type ascription
 }
--- a/tests/ui/feature-gates/feature-gate-type_ascription.stderr
+++ b/tests/ui/feature-gates/feature-gate-type_ascription.stderr
@ -1,4 +1,4 @@
-error[E0658]: use of unstable library feature 'type_ascription': placeholder syntax for type ascription
+error[E0658]: use of unstable library feature `type_ascription`: placeholder syntax for type ascription
  --> $DIR/feature-gate-type_ascription.rs:4:13
   |
 LL |     let a = type_ascribe!(10, u8);
--- a/tests/ui/feature-gates/feature-gate-unboxed-closures-method-calls.rs
+++ b/tests/ui/feature-gates/feature-gate-unboxed-closures-method-calls.rs
@ -1,9 +1,9 @@
 #![allow(dead_code)]

 fn foo<F: Fn()>(mut f: F) {
-    f.call(()); //~ ERROR use of unstable library feature 'fn_traits'
-    f.call_mut(()); //~ ERROR use of unstable library feature 'fn_traits'
-    f.call_once(()); //~ ERROR use of unstable library feature 'fn_traits'
+    f.call(()); //~ ERROR use of unstable library feature `fn_traits`
+    f.call_mut(()); //~ ERROR use of unstable library feature `fn_traits`
+    f.call_once(()); //~ ERROR use of unstable library feature `fn_traits`
 }

 fn main() {}
--- a/tests/ui/feature-gates/feature-gate-unboxed-closures-method-calls.stderr
+++ b/tests/ui/feature-gates/feature-gate-unboxed-closures-method-calls.stderr
@ -1,4 +1,4 @@
-error[E0658]: use of unstable library feature 'fn_traits'
+error[E0658]: use of unstable library feature `fn_traits`
  --> $DIR/feature-gate-unboxed-closures-method-calls.rs:4:7
   |
 LL |     f.call(());
@ -8,7 +8,7 @@ LL |     f.call(());
   = help: add `#![feature(fn_traits)]` to the crate attributes to enable
   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date

-error[E0658]: use of unstable library feature 'fn_traits'
+error[E0658]: use of unstable library feature `fn_traits`
  --> $DIR/feature-gate-unboxed-closures-method-calls.rs:5:7
   |
 LL |     f.call_mut(());
@ -18,7 +18,7 @@ LL |     f.call_mut(());
   = help: add `#![feature(fn_traits)]` to the crate attributes to enable
   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date

-error[E0658]: use of unstable library feature 'fn_traits'
+error[E0658]: use of unstable library feature `fn_traits`
  --> $DIR/feature-gate-unboxed-closures-method-calls.rs:6:7
   |
 LL |     f.call_once(());
--- a/tests/ui/feature-gates/feature-gate-unboxed-closures-ufcs-calls.rs
+++ b/tests/ui/feature-gates/feature-gate-unboxed-closures-ufcs-calls.rs
@ -1,9 +1,9 @@
 #![allow(dead_code)]

 fn foo<F: Fn()>(mut f: F) {
-    Fn::call(&f, ()); //~ ERROR use of unstable library feature 'fn_traits'
-    FnMut::call_mut(&mut f, ()); //~ ERROR use of unstable library feature 'fn_traits'
-    FnOnce::call_once(f, ()); //~ ERROR use of unstable library feature 'fn_traits'
+    Fn::call(&f, ()); //~ ERROR use of unstable library feature `fn_traits`
+    FnMut::call_mut(&mut f, ()); //~ ERROR use of unstable library feature `fn_traits`
+    FnOnce::call_once(f, ()); //~ ERROR use of unstable library feature `fn_traits`
 }

 fn main() {}
--- a/tests/ui/feature-gates/feature-gate-unboxed-closures-ufcs-calls.stderr
+++ b/tests/ui/feature-gates/feature-gate-unboxed-closures-ufcs-calls.stderr
@ -1,4 +1,4 @@
-error[E0658]: use of unstable library feature 'fn_traits'
+error[E0658]: use of unstable library feature `fn_traits`
  --> $DIR/feature-gate-unboxed-closures-ufcs-calls.rs:4:5
   |
 LL |     Fn::call(&f, ());
@ -8,7 +8,7 @@ LL |     Fn::call(&f, ());
   = help: add `#![feature(fn_traits)]` to the crate attributes to enable
   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date

-error[E0658]: use of unstable library feature 'fn_traits'
+error[E0658]: use of unstable library feature `fn_traits`
  --> $DIR/feature-gate-unboxed-closures-ufcs-calls.rs:5:5
   |
 LL |     FnMut::call_mut(&mut f, ());
@ -18,7 +18,7 @@ LL |     FnMut::call_mut(&mut f, ());
   = help: add `#![feature(fn_traits)]` to the crate attributes to enable
   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date

-error[E0658]: use of unstable library feature 'fn_traits'
+error[E0658]: use of unstable library feature `fn_traits`
  --> $DIR/feature-gate-unboxed-closures-ufcs-calls.rs:6:5
   |
 LL |     FnOnce::call_once(f, ());
--- a/tests/ui/feature-gates/issue-49983-see-issue-0.stderr
+++ b/tests/ui/feature-gates/issue-49983-see-issue-0.stderr
@ -1,4 +1,4 @@
-error[E0658]: use of unstable library feature 'ptr_internals': use `NonNull` instead and consider `PhantomData<T>` (if you also use `#[may_dangle]`), `Send`, and/or `Sync`
+error[E0658]: use of unstable library feature `ptr_internals`: use `NonNull` instead and consider `PhantomData<T>` (if you also use `#[may_dangle]`), `Send`, and/or `Sync`
  --> $DIR/issue-49983-see-issue-0.rs:4:30
   |
 LL | #[allow(unused_imports)] use core::ptr::Unique;
--- a/tests/ui/feature-gates/rustc-private.rs
+++ b/tests/ui/feature-gates/rustc-private.rs
@ -1,5 +1,5 @@
 // gate-test-rustc_private

-extern crate cfg_if; //~ ERROR  use of unstable library feature 'rustc_private'
+extern crate cfg_if; //~ ERROR  use of unstable library feature `rustc_private`

 fn main() {}
--- a/tests/ui/feature-gates/rustc-private.stderr
+++ b/tests/ui/feature-gates/rustc-private.stderr
@ -1,4 +1,4 @@
-error[E0658]: use of unstable library feature 'rustc_private': this crate is being loaded from the sysroot, an unstable location; did you mean to load this crate from crates.io via `Cargo.toml` instead?
+error[E0658]: use of unstable library feature `rustc_private`: this crate is being loaded from the sysroot, an unstable location; did you mean to load this crate from crates.io via `Cargo.toml` instead?
  --> $DIR/rustc-private.rs:3:1
   |
 LL | extern crate cfg_if;
--- a/tests/ui/feature-gates/trace_macros-gate.stderr
+++ b/tests/ui/feature-gates/trace_macros-gate.stderr
@ -1,4 +1,4 @@
-error[E0658]: use of unstable library feature 'trace_macros': `trace_macros` is not stable enough for use and is subject to change
+error[E0658]: use of unstable library feature `trace_macros`: `trace_macros` is not stable enough for use and is subject to change
  --> $DIR/trace_macros-gate.rs:4:5
   |
 LL |     trace_macros!();
@ -14,7 +14,7 @@ error: trace_macros! accepts only `true` or `false`
 LL |     trace_macros!();
   |     ^^^^^^^^^^^^^^^

-error[E0658]: use of unstable library feature 'trace_macros': `trace_macros` is not stable enough for use and is subject to change
+error[E0658]: use of unstable library feature `trace_macros`: `trace_macros` is not stable enough for use and is subject to change
  --> $DIR/trace_macros-gate.rs:6:5
   |
 LL |     trace_macros!(true);
@ -24,7 +24,7 @@ LL |     trace_macros!(true);
   = help: add `#![feature(trace_macros)]` to the crate attributes to enable
   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date

-error[E0658]: use of unstable library feature 'trace_macros': `trace_macros` is not stable enough for use and is subject to change
+error[E0658]: use of unstable library feature `trace_macros`: `trace_macros` is not stable enough for use and is subject to change
  --> $DIR/trace_macros-gate.rs:7:5
   |
 LL |     trace_macros!(false);
@ -34,7 +34,7 @@ LL |     trace_macros!(false);
   = help: add `#![feature(trace_macros)]` to the crate attributes to enable
   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date

-error[E0658]: use of unstable library feature 'trace_macros': `trace_macros` is not stable enough for use and is subject to change
+error[E0658]: use of unstable library feature `trace_macros`: `trace_macros` is not stable enough for use and is subject to change
  --> $DIR/trace_macros-gate.rs:10:26
   |
 LL |         ($x: ident) => { trace_macros!($x) }
--- a/tests/ui/imports/issue-37887.stderr
+++ b/tests/ui/imports/issue-37887.stderr
@ -9,7 +9,7 @@ help: consider importing the `test` crate
 LL + extern crate test;
   |

-error[E0658]: use of unstable library feature 'test'
+error[E0658]: use of unstable library feature `test`
  --> $DIR/issue-37887.rs:2:5
   |
 LL |     extern crate test;
--- a/tests/ui/imports/resolve-other-libc.rs
+++ b/tests/ui/imports/resolve-other-libc.rs
@ -6,7 +6,7 @@
 // indicates that `libc` was wrongly resolved to `libc` shipped with the
 // compiler:
 //
-//   error[E0658]: use of unstable library feature 'rustc_private': \
+//   error[E0658]: use of unstable library feature `rustc_private`: \
 //           this crate is being loaded from the sysroot
 //
 extern crate libc; //~ ERROR: extern location for libc does not exist: test.rlib
--- a/tests/ui/inference/inference_unstable_forced.stderr
+++ b/tests/ui/inference/inference_unstable_forced.stderr
@ -1,4 +1,4 @@
-error[E0658]: use of unstable library feature 'ipu_flatten'
+error[E0658]: use of unstable library feature `ipu_flatten`
  --> $DIR/inference_unstable_forced.rs:11:20
   |
 LL |     assert_eq!('x'.ipu_flatten(), 0);
--- a/tests/ui/internal/internal-unstable-noallow.rs
+++ b/tests/ui/internal/internal-unstable-noallow.rs
@ -4,10 +4,10 @@
 // the // ~ form.

 //@ aux-build:internal_unstable.rs
-//@ error-pattern:use of unstable library feature 'function'
-//@ error-pattern:use of unstable library feature 'struct_field'
-//@ error-pattern:use of unstable library feature 'method'
-//@ error-pattern:use of unstable library feature 'struct2_field'
+//@ error-pattern:use of unstable library feature `function`
+//@ error-pattern:use of unstable library feature `struct_field`
+//@ error-pattern:use of unstable library feature `method`
+//@ error-pattern:use of unstable library feature `struct2_field`

 #[macro_use]
 extern crate internal_unstable;
--- a/tests/ui/internal/internal-unstable-noallow.stderr
+++ b/tests/ui/internal/internal-unstable-noallow.stderr
@ -1,4 +1,4 @@
-error[E0658]: use of unstable library feature 'function'
+error[E0658]: use of unstable library feature `function`
  --> $DIR/internal-unstable-noallow.rs:16:5
   |
 LL |     call_unstable_noallow!();
@ -8,7 +8,7 @@ LL |     call_unstable_noallow!();
   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date
   = note: this error originates in the macro `call_unstable_noallow` (in Nightly builds, run with -Z macro-backtrace for more info)

-error[E0658]: use of unstable library feature 'struct_field'
+error[E0658]: use of unstable library feature `struct_field`
  --> $DIR/internal-unstable-noallow.rs:18:5
   |
 LL |     construct_unstable_noallow!(0);
@ -18,7 +18,7 @@ LL |     construct_unstable_noallow!(0);
   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date
   = note: this error originates in the macro `construct_unstable_noallow` (in Nightly builds, run with -Z macro-backtrace for more info)

-error[E0658]: use of unstable library feature 'method'
+error[E0658]: use of unstable library feature `method`
  --> $DIR/internal-unstable-noallow.rs:20:35
   |
 LL |     |x: internal_unstable::Foo| { call_method_noallow!(x) };
@ -28,7 +28,7 @@ LL |     |x: internal_unstable::Foo| { call_method_noallow!(x) };
   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date
   = note: this error originates in the macro `call_method_noallow` (in Nightly builds, run with -Z macro-backtrace for more info)

-error[E0658]: use of unstable library feature 'struct2_field'
+error[E0658]: use of unstable library feature `struct2_field`
  --> $DIR/internal-unstable-noallow.rs:22:35
   |
 LL |     |x: internal_unstable::Bar| { access_field_noallow!(x) };
--- a/tests/ui/internal/internal-unstable-thread-local.stderr
+++ b/tests/ui/internal/internal-unstable-thread-local.stderr
@ -1,4 +1,4 @@
-error[E0658]: use of unstable library feature 'function'
+error[E0658]: use of unstable library feature `function`
  --> $DIR/internal-unstable-thread-local.rs:9:32
   |
 LL | thread_local!(static BAR: () = internal_unstable::unstable());
--- a/tests/ui/internal/internal-unstable.stderr
+++ b/tests/ui/internal/internal-unstable.stderr
@ -1,4 +1,4 @@
-error[E0658]: use of unstable library feature 'function'
+error[E0658]: use of unstable library feature `function`
  --> $DIR/internal-unstable.rs:48:25
   |
 LL |     pass_through_allow!(internal_unstable::unstable());
@ -7,7 +7,7 @@ LL |     pass_through_allow!(internal_unstable::unstable());
   = help: add `#![feature(function)]` to the crate attributes to enable
   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date

-error[E0658]: use of unstable library feature 'function'
+error[E0658]: use of unstable library feature `function`
  --> $DIR/internal-unstable.rs:50:27
   |
 LL |     pass_through_noallow!(internal_unstable::unstable());
@ -16,7 +16,7 @@ LL |     pass_through_noallow!(internal_unstable::unstable());
   = help: add `#![feature(function)]` to the crate attributes to enable
   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date

-error[E0658]: use of unstable library feature 'function'
+error[E0658]: use of unstable library feature `function`
  --> $DIR/internal-unstable.rs:54:22
   |
 LL |     println!("{:?}", internal_unstable::unstable());
@ -25,7 +25,7 @@ LL |     println!("{:?}", internal_unstable::unstable());
   = help: add `#![feature(function)]` to the crate attributes to enable
   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date

-error[E0658]: use of unstable library feature 'function'
+error[E0658]: use of unstable library feature `function`
  --> $DIR/internal-unstable.rs:56:10
   |
 LL |     bar!(internal_unstable::unstable());
@ -34,7 +34,7 @@ LL |     bar!(internal_unstable::unstable());
   = help: add `#![feature(function)]` to the crate attributes to enable
   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date

-error[E0658]: use of unstable library feature 'function'
+error[E0658]: use of unstable library feature `function`
  --> $DIR/internal-unstable.rs:18:9
   |
 LL |         internal_unstable::unstable();
--- a/tests/ui/intrinsics/unchecked_math_unstable.stderr
+++ b/tests/ui/intrinsics/unchecked_math_unstable.stderr
@ -1,4 +1,4 @@
-error[E0658]: use of unstable library feature 'core_intrinsics': intrinsics are unlikely to ever be stabilized, instead they should be used through stabilized interfaces in the rest of the standard library
+error[E0658]: use of unstable library feature `core_intrinsics`: intrinsics are unlikely to ever be stabilized, instead they should be used through stabilized interfaces in the rest of the standard library
  --> $DIR/unchecked_math_unstable.rs:4:19
   |
 LL |         let add = std::intrinsics::unchecked_add(x, y);
@ -7,7 +7,7 @@ LL |         let add = std::intrinsics::unchecked_add(x, y);
   = help: add `#![feature(core_intrinsics)]` to the crate attributes to enable
   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date

-error[E0658]: use of unstable library feature 'core_intrinsics': intrinsics are unlikely to ever be stabilized, instead they should be used through stabilized interfaces in the rest of the standard library
+error[E0658]: use of unstable library feature `core_intrinsics`: intrinsics are unlikely to ever be stabilized, instead they should be used through stabilized interfaces in the rest of the standard library
  --> $DIR/unchecked_math_unstable.rs:5:19
   |
 LL |         let sub = std::intrinsics::unchecked_sub(x, y);
@ -16,7 +16,7 @@ LL |         let sub = std::intrinsics::unchecked_sub(x, y);
   = help: add `#![feature(core_intrinsics)]` to the crate attributes to enable
   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date

-error[E0658]: use of unstable library feature 'core_intrinsics': intrinsics are unlikely to ever be stabilized, instead they should be used through stabilized interfaces in the rest of the standard library
+error[E0658]: use of unstable library feature `core_intrinsics`: intrinsics are unlikely to ever be stabilized, instead they should be used through stabilized interfaces in the rest of the standard library
  --> $DIR/unchecked_math_unstable.rs:6:19
   |
 LL |         let mul = std::intrinsics::unchecked_mul(x, y);
--- a/tests/ui/issues/issue-52489.rs
+++ b/tests/ui/issues/issue-52489.rs
@ -3,6 +3,6 @@
 //@ compile-flags:--extern issue_52489

 use issue_52489;
-//~^ ERROR use of unstable library feature 'issue_52489_unstable'
+//~^ ERROR use of unstable library feature `issue_52489_unstable`

 fn main() {}
--- a/tests/ui/issues/issue-52489.stderr
+++ b/tests/ui/issues/issue-52489.stderr
@ -1,4 +1,4 @@
-error[E0658]: use of unstable library feature 'issue_52489_unstable'
+error[E0658]: use of unstable library feature `issue_52489_unstable`
  --> $DIR/issue-52489.rs:5:5
   |
 LL | use issue_52489;
--- a/tests/ui/layout/rust-call-abi-not-a-tuple-ice-81974.stderr
+++ b/tests/ui/layout/rust-call-abi-not-a-tuple-ice-81974.stderr
@ -71,6 +71,10 @@ LL |     cachedcoso.call_once(1);
   |
 note: required by a bound in `call_once`
  --> $SRC_DIR/core/src/ops/function.rs:LL:COL
+help: use a unary tuple instead
+   |
+LL |     cachedcoso.call_once((1,));
+   |                          + ++

 error: aborting due to 6 previous errors

--- a/tests/ui/layout/thaw-transmute-invalid-enum.rs
+++ b/tests/ui/layout/thaw-transmute-invalid-enum.rs
@ -2,13 +2,13 @@

 mod assert {
    use std::mem::{Assume, TransmuteFrom};
-    //~^ ERROR: use of unstable library feature 'transmutability'
-    //~| ERROR: use of unstable library feature 'transmutability'
+    //~^ ERROR: use of unstable library feature `transmutability`
+    //~| ERROR: use of unstable library feature `transmutability`

    pub fn is_transmutable<Src, Dst>()
    where
        Dst: TransmuteFrom<Src>,
-        //~^ ERROR: use of unstable library feature 'transmutability'
+        //~^ ERROR: use of unstable library feature `transmutability`
    {
    }
 }
--- a/tests/ui/layout/thaw-transmute-invalid-enum.stderr
+++ b/tests/ui/layout/thaw-transmute-invalid-enum.stderr
@ -20,7 +20,7 @@ LL | |     V = 0xFF,
 LL | | }
   | |_- not a struct or union

-error[E0658]: use of unstable library feature 'transmutability'
+error[E0658]: use of unstable library feature `transmutability`
  --> $DIR/thaw-transmute-invalid-enum.rs:4:20
   |
 LL |     use std::mem::{Assume, TransmuteFrom};
@ -30,7 +30,7 @@ LL |     use std::mem::{Assume, TransmuteFrom};
   = help: add `#![feature(transmutability)]` to the crate attributes to enable
   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date

-error[E0658]: use of unstable library feature 'transmutability'
+error[E0658]: use of unstable library feature `transmutability`
  --> $DIR/thaw-transmute-invalid-enum.rs:4:28
   |
 LL |     use std::mem::{Assume, TransmuteFrom};
@ -40,7 +40,7 @@ LL |     use std::mem::{Assume, TransmuteFrom};
   = help: add `#![feature(transmutability)]` to the crate attributes to enable
   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date

-error[E0658]: use of unstable library feature 'transmutability'
+error[E0658]: use of unstable library feature `transmutability`
  --> $DIR/thaw-transmute-invalid-enum.rs:10:14
   |
 LL |         Dst: TransmuteFrom<Src>,
--- a/tests/ui/lint/expansion-time.rs
+++ b/tests/ui/lint/expansion-time.rs
@ -11,7 +11,7 @@ macro_rules! m { ($i) => {} } //~ WARN missing fragment specifier

 #[warn(soft_unstable)]
 mod benches {
-    #[bench] //~ WARN use of unstable library feature 'test'
+    #[bench] //~ WARN use of unstable library feature `test`
             //~| WARN this was previously accepted
    fn foo() {}
 }
--- a/tests/ui/lint/expansion-time.stderr
+++ b/tests/ui/lint/expansion-time.stderr
@ -26,7 +26,7 @@ note: the lint level is defined here
 LL | #[warn(missing_fragment_specifier)]
   |        ^^^^^^^^^^^^^^^^^^^^^^^^^^

-warning: use of unstable library feature 'test': `bench` is a part of custom test frameworks which are unstable
+warning: use of unstable library feature `test`: `bench` is a part of custom test frameworks which are unstable
  --> $DIR/expansion-time.rs:14:7
   |
 LL |     #[bench]
@ -70,7 +70,7 @@ LL | #[warn(missing_fragment_specifier)]
   |        ^^^^^^^^^^^^^^^^^^^^^^^^^^

 Future breakage diagnostic:
-warning: use of unstable library feature 'test': `bench` is a part of custom test frameworks which are unstable
+warning: use of unstable library feature `test`: `bench` is a part of custom test frameworks which are unstable
  --> $DIR/expansion-time.rs:14:7
   |
 LL |     #[bench]
--- a/tests/ui/lint/lint-output-format.stderr
+++ b/tests/ui/lint/lint-output-format.stderr
@ -1,4 +1,4 @@
-error[E0658]: use of unstable library feature 'unstable_test_feature'
+error[E0658]: use of unstable library feature `unstable_test_feature`
  --> $DIR/lint-output-format.rs:6:1
   |
 LL | extern crate lint_output_format;
@ -7,7 +7,7 @@ LL | extern crate lint_output_format;
   = help: add `#![feature(unstable_test_feature)]` to the crate attributes to enable
   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date

-error[E0658]: use of unstable library feature 'unstable_test_feature'
+error[E0658]: use of unstable library feature `unstable_test_feature`
  --> $DIR/lint-output-format.rs:7:26
   |
 LL | use lint_output_format::{foo, bar};
@ -16,7 +16,7 @@ LL | use lint_output_format::{foo, bar};
   = help: add `#![feature(unstable_test_feature)]` to the crate attributes to enable
   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date

-error[E0658]: use of unstable library feature 'unstable_test_feature'
+error[E0658]: use of unstable library feature `unstable_test_feature`
  --> $DIR/lint-output-format.rs:7:31
   |
 LL | use lint_output_format::{foo, bar};
@ -25,7 +25,7 @@ LL | use lint_output_format::{foo, bar};
   = help: add `#![feature(unstable_test_feature)]` to the crate attributes to enable
   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date

-error[E0658]: use of unstable library feature 'unstable_test_feature'
+error[E0658]: use of unstable library feature `unstable_test_feature`
  --> $DIR/lint-output-format.rs:12:14
   |
 LL |     let _y = bar();
--- a/tests/ui/lint/lint-stability-2.rs
+++ b/tests/ui/lint/lint-stability-2.rs
@ -66,15 +66,15 @@ mod cross_crate {
        <Foo>::trait_unstable(&foo); //~ ERROR use of unstable library feature

        foo.method_unstable_text();
-        //~^ ERROR use of unstable library feature 'unstable_test_feature': text
+        //~^ ERROR use of unstable library feature `unstable_test_feature`: text
        Foo::method_unstable_text(&foo);
-        //~^ ERROR use of unstable library feature 'unstable_test_feature': text
+        //~^ ERROR use of unstable library feature `unstable_test_feature`: text
        <Foo>::method_unstable_text(&foo);
-        //~^ ERROR use of unstable library feature 'unstable_test_feature': text
+        //~^ ERROR use of unstable library feature `unstable_test_feature`: text
        foo.trait_unstable_text();
-        //~^ ERROR use of unstable library feature 'unstable_test_feature': text
+        //~^ ERROR use of unstable library feature `unstable_test_feature`: text
        <Foo>::trait_unstable_text(&foo);
-        //~^ ERROR use of unstable library feature 'unstable_test_feature': text
+        //~^ ERROR use of unstable library feature `unstable_test_feature`: text

        stable();
        foo.method_stable();
@ -139,9 +139,9 @@ mod cross_crate {
        foo.trait_unstable(); //~ ERROR use of unstable library feature
        <Foo>::trait_unstable(&foo); //~ ERROR use of unstable library feature
        foo.trait_unstable_text();
-        //~^ ERROR use of unstable library feature 'unstable_test_feature': text
+        //~^ ERROR use of unstable library feature `unstable_test_feature`: text
        <Foo>::trait_unstable_text(&foo);
-        //~^ ERROR use of unstable library feature 'unstable_test_feature': text
+        //~^ ERROR use of unstable library feature `unstable_test_feature`: text
        foo.trait_stable();
        Trait::trait_stable(&foo);
        <Foo>::trait_stable(&foo);
@ -157,7 +157,7 @@ mod cross_crate {
        //~^ ERROR use of unstable library feature
        foo.trait_unstable(); //~ ERROR use of unstable library feature
        foo.trait_unstable_text();
-        //~^ ERROR use of unstable library feature 'unstable_test_feature': text
+        //~^ ERROR use of unstable library feature `unstable_test_feature`: text
        foo.trait_stable();
    }

--- a/tests/ui/lint/lint-stability-2.stderr
+++ b/tests/ui/lint/lint-stability-2.stderr
@ -1,4 +1,4 @@
-error[E0658]: use of unstable library feature 'unstable_test_feature'
+error[E0658]: use of unstable library feature `unstable_test_feature`
  --> $DIR/lint-stability-2.rs:40:13
   |
 LL |         foo.method_deprecated_unstable();
@ -7,7 +7,7 @@ LL |         foo.method_deprecated_unstable();
   = help: add `#![feature(unstable_test_feature)]` to the crate attributes to enable
   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date

-error[E0658]: use of unstable library feature 'unstable_test_feature'
+error[E0658]: use of unstable library feature `unstable_test_feature`
  --> $DIR/lint-stability-2.rs:42:9
   |
 LL |         Foo::method_deprecated_unstable(&foo);
@ -16,7 +16,7 @@ LL |         Foo::method_deprecated_unstable(&foo);
   = help: add `#![feature(unstable_test_feature)]` to the crate attributes to enable
   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date

-error[E0658]: use of unstable library feature 'unstable_test_feature'
+error[E0658]: use of unstable library feature `unstable_test_feature`
  --> $DIR/lint-stability-2.rs:44:9
   |
 LL |         <Foo>::method_deprecated_unstable(&foo);
@ -25,7 +25,7 @@ LL |         <Foo>::method_deprecated_unstable(&foo);
   = help: add `#![feature(unstable_test_feature)]` to the crate attributes to enable
   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date

-error[E0658]: use of unstable library feature 'unstable_test_feature'
+error[E0658]: use of unstable library feature `unstable_test_feature`
  --> $DIR/lint-stability-2.rs:46:13
   |
 LL |         foo.trait_deprecated_unstable();
@ -34,7 +34,7 @@ LL |         foo.trait_deprecated_unstable();
   = help: add `#![feature(unstable_test_feature)]` to the crate attributes to enable
   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date

-error[E0658]: use of unstable library feature 'unstable_test_feature'
+error[E0658]: use of unstable library feature `unstable_test_feature`
  --> $DIR/lint-stability-2.rs:48:9
   |
 LL |         <Foo>::trait_deprecated_unstable(&foo);
@ -43,7 +43,7 @@ LL |         <Foo>::trait_deprecated_unstable(&foo);
   = help: add `#![feature(unstable_test_feature)]` to the crate attributes to enable
   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date

-error[E0658]: use of unstable library feature 'unstable_test_feature'
+error[E0658]: use of unstable library feature `unstable_test_feature`
  --> $DIR/lint-stability-2.rs:51:13
   |
 LL |         foo.method_deprecated_unstable_text();
@ -52,7 +52,7 @@ LL |         foo.method_deprecated_unstable_text();
   = help: add `#![feature(unstable_test_feature)]` to the crate attributes to enable
   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date

-error[E0658]: use of unstable library feature 'unstable_test_feature'
+error[E0658]: use of unstable library feature `unstable_test_feature`
  --> $DIR/lint-stability-2.rs:53:9
   |
 LL |         Foo::method_deprecated_unstable_text(&foo);
@ -61,7 +61,7 @@ LL |         Foo::method_deprecated_unstable_text(&foo);
   = help: add `#![feature(unstable_test_feature)]` to the crate attributes to enable
   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date

-error[E0658]: use of unstable library feature 'unstable_test_feature'
+error[E0658]: use of unstable library feature `unstable_test_feature`
  --> $DIR/lint-stability-2.rs:55:9
   |
 LL |         <Foo>::method_deprecated_unstable_text(&foo);
@ -70,7 +70,7 @@ LL |         <Foo>::method_deprecated_unstable_text(&foo);
   = help: add `#![feature(unstable_test_feature)]` to the crate attributes to enable
   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date

-error[E0658]: use of unstable library feature 'unstable_test_feature'
+error[E0658]: use of unstable library feature `unstable_test_feature`
  --> $DIR/lint-stability-2.rs:57:13
   |
 LL |         foo.trait_deprecated_unstable_text();
@ -79,7 +79,7 @@ LL |         foo.trait_deprecated_unstable_text();
   = help: add `#![feature(unstable_test_feature)]` to the crate attributes to enable
   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date

-error[E0658]: use of unstable library feature 'unstable_test_feature'
+error[E0658]: use of unstable library feature `unstable_test_feature`
  --> $DIR/lint-stability-2.rs:59:9
   |
 LL |         <Foo>::trait_deprecated_unstable_text(&foo);
@ -88,7 +88,7 @@ LL |         <Foo>::trait_deprecated_unstable_text(&foo);
   = help: add `#![feature(unstable_test_feature)]` to the crate attributes to enable
   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date

-error[E0658]: use of unstable library feature 'unstable_test_feature'
+error[E0658]: use of unstable library feature `unstable_test_feature`
  --> $DIR/lint-stability-2.rs:62:13
   |
 LL |         foo.method_unstable();
@ -97,7 +97,7 @@ LL |         foo.method_unstable();
   = help: add `#![feature(unstable_test_feature)]` to the crate attributes to enable
   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date

-error[E0658]: use of unstable library feature 'unstable_test_feature'
+error[E0658]: use of unstable library feature `unstable_test_feature`
  --> $DIR/lint-stability-2.rs:63:9
   |
 LL |         Foo::method_unstable(&foo);
@ -106,7 +106,7 @@ LL |         Foo::method_unstable(&foo);
   = help: add `#![feature(unstable_test_feature)]` to the crate attributes to enable
   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date

-error[E0658]: use of unstable library feature 'unstable_test_feature'
+error[E0658]: use of unstable library feature `unstable_test_feature`
  --> $DIR/lint-stability-2.rs:64:9
   |
 LL |         <Foo>::method_unstable(&foo);
@ -115,7 +115,7 @@ LL |         <Foo>::method_unstable(&foo);
   = help: add `#![feature(unstable_test_feature)]` to the crate attributes to enable
   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date

-error[E0658]: use of unstable library feature 'unstable_test_feature'
+error[E0658]: use of unstable library feature `unstable_test_feature`
  --> $DIR/lint-stability-2.rs:65:13
   |
 LL |         foo.trait_unstable();
@ -124,7 +124,7 @@ LL |         foo.trait_unstable();
   = help: add `#![feature(unstable_test_feature)]` to the crate attributes to enable
   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date

-error[E0658]: use of unstable library feature 'unstable_test_feature'
+error[E0658]: use of unstable library feature `unstable_test_feature`
  --> $DIR/lint-stability-2.rs:66:9
   |
 LL |         <Foo>::trait_unstable(&foo);
@ -133,7 +133,7 @@ LL |         <Foo>::trait_unstable(&foo);
   = help: add `#![feature(unstable_test_feature)]` to the crate attributes to enable
   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date

-error[E0658]: use of unstable library feature 'unstable_test_feature': text
+error[E0658]: use of unstable library feature `unstable_test_feature`: text
  --> $DIR/lint-stability-2.rs:68:13
   |
 LL |         foo.method_unstable_text();
@ -142,7 +142,7 @@ LL |         foo.method_unstable_text();
   = help: add `#![feature(unstable_test_feature)]` to the crate attributes to enable
   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date

-error[E0658]: use of unstable library feature 'unstable_test_feature': text
+error[E0658]: use of unstable library feature `unstable_test_feature`: text
  --> $DIR/lint-stability-2.rs:70:9
   |
 LL |         Foo::method_unstable_text(&foo);
@ -151,7 +151,7 @@ LL |         Foo::method_unstable_text(&foo);
   = help: add `#![feature(unstable_test_feature)]` to the crate attributes to enable
   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date

-error[E0658]: use of unstable library feature 'unstable_test_feature': text
+error[E0658]: use of unstable library feature `unstable_test_feature`: text
  --> $DIR/lint-stability-2.rs:72:9
   |
 LL |         <Foo>::method_unstable_text(&foo);
@ -160,7 +160,7 @@ LL |         <Foo>::method_unstable_text(&foo);
   = help: add `#![feature(unstable_test_feature)]` to the crate attributes to enable
   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date

-error[E0658]: use of unstable library feature 'unstable_test_feature': text
+error[E0658]: use of unstable library feature `unstable_test_feature`: text
  --> $DIR/lint-stability-2.rs:74:13
   |
 LL |         foo.trait_unstable_text();
@ -169,7 +169,7 @@ LL |         foo.trait_unstable_text();
   = help: add `#![feature(unstable_test_feature)]` to the crate attributes to enable
   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date

-error[E0658]: use of unstable library feature 'unstable_test_feature': text
+error[E0658]: use of unstable library feature `unstable_test_feature`: text
  --> $DIR/lint-stability-2.rs:76:9
   |
 LL |         <Foo>::trait_unstable_text(&foo);
@ -178,7 +178,7 @@ LL |         <Foo>::trait_unstable_text(&foo);
   = help: add `#![feature(unstable_test_feature)]` to the crate attributes to enable
   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date

-error[E0658]: use of unstable library feature 'unstable_test_feature'
+error[E0658]: use of unstable library feature `unstable_test_feature`
  --> $DIR/lint-stability-2.rs:131:13
   |
 LL |         foo.trait_deprecated_unstable();
@ -187,7 +187,7 @@ LL |         foo.trait_deprecated_unstable();
   = help: add `#![feature(unstable_test_feature)]` to the crate attributes to enable
   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date

-error[E0658]: use of unstable library feature 'unstable_test_feature'
+error[E0658]: use of unstable library feature `unstable_test_feature`
  --> $DIR/lint-stability-2.rs:133:9
   |
 LL |         <Foo>::trait_deprecated_unstable(&foo);
@ -196,7 +196,7 @@ LL |         <Foo>::trait_deprecated_unstable(&foo);
   = help: add `#![feature(unstable_test_feature)]` to the crate attributes to enable
   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date

-error[E0658]: use of unstable library feature 'unstable_test_feature'
+error[E0658]: use of unstable library feature `unstable_test_feature`
  --> $DIR/lint-stability-2.rs:135:13
   |
 LL |         foo.trait_deprecated_unstable_text();
@ -205,7 +205,7 @@ LL |         foo.trait_deprecated_unstable_text();
   = help: add `#![feature(unstable_test_feature)]` to the crate attributes to enable
   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date

-error[E0658]: use of unstable library feature 'unstable_test_feature'
+error[E0658]: use of unstable library feature `unstable_test_feature`
  --> $DIR/lint-stability-2.rs:137:9
   |
 LL |         <Foo>::trait_deprecated_unstable_text(&foo);
@ -214,7 +214,7 @@ LL |         <Foo>::trait_deprecated_unstable_text(&foo);
   = help: add `#![feature(unstable_test_feature)]` to the crate attributes to enable
   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date

-error[E0658]: use of unstable library feature 'unstable_test_feature'
+error[E0658]: use of unstable library feature `unstable_test_feature`
  --> $DIR/lint-stability-2.rs:139:13
   |
 LL |         foo.trait_unstable();
@ -223,7 +223,7 @@ LL |         foo.trait_unstable();
   = help: add `#![feature(unstable_test_feature)]` to the crate attributes to enable
   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date

-error[E0658]: use of unstable library feature 'unstable_test_feature'
+error[E0658]: use of unstable library feature `unstable_test_feature`
  --> $DIR/lint-stability-2.rs:140:9
   |
 LL |         <Foo>::trait_unstable(&foo);
@ -232,7 +232,7 @@ LL |         <Foo>::trait_unstable(&foo);
   = help: add `#![feature(unstable_test_feature)]` to the crate attributes to enable
   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date

-error[E0658]: use of unstable library feature 'unstable_test_feature': text
+error[E0658]: use of unstable library feature `unstable_test_feature`: text
  --> $DIR/lint-stability-2.rs:141:13
   |
 LL |         foo.trait_unstable_text();
@ -241,7 +241,7 @@ LL |         foo.trait_unstable_text();
   = help: add `#![feature(unstable_test_feature)]` to the crate attributes to enable
   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date

-error[E0658]: use of unstable library feature 'unstable_test_feature': text
+error[E0658]: use of unstable library feature `unstable_test_feature`: text
  --> $DIR/lint-stability-2.rs:143:9
   |
 LL |         <Foo>::trait_unstable_text(&foo);
@ -250,7 +250,7 @@ LL |         <Foo>::trait_unstable_text(&foo);
   = help: add `#![feature(unstable_test_feature)]` to the crate attributes to enable
   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date

-error[E0658]: use of unstable library feature 'unstable_test_feature'
+error[E0658]: use of unstable library feature `unstable_test_feature`
  --> $DIR/lint-stability-2.rs:154:13
   |
 LL |         foo.trait_deprecated_unstable();
@ -259,7 +259,7 @@ LL |         foo.trait_deprecated_unstable();
   = help: add `#![feature(unstable_test_feature)]` to the crate attributes to enable
   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date

-error[E0658]: use of unstable library feature 'unstable_test_feature'
+error[E0658]: use of unstable library feature `unstable_test_feature`
  --> $DIR/lint-stability-2.rs:156:13
   |
 LL |         foo.trait_deprecated_unstable_text();
@ -268,7 +268,7 @@ LL |         foo.trait_deprecated_unstable_text();
   = help: add `#![feature(unstable_test_feature)]` to the crate attributes to enable
   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date

-error[E0658]: use of unstable library feature 'unstable_test_feature'
+error[E0658]: use of unstable library feature `unstable_test_feature`
  --> $DIR/lint-stability-2.rs:158:13
   |
 LL |         foo.trait_unstable();
@ -277,7 +277,7 @@ LL |         foo.trait_unstable();
   = help: add `#![feature(unstable_test_feature)]` to the crate attributes to enable
   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date

-error[E0658]: use of unstable library feature 'unstable_test_feature': text
+error[E0658]: use of unstable library feature `unstable_test_feature`: text
  --> $DIR/lint-stability-2.rs:159:13
   |
 LL |         foo.trait_unstable_text();
--- a/tests/ui/lint/lint-stability-fields.stderr
+++ b/tests/ui/lint/lint-stability-fields.stderr
@ -1,4 +1,4 @@
-error[E0658]: use of unstable library feature 'unstable_test_feature'
+error[E0658]: use of unstable library feature `unstable_test_feature`
  --> $DIR/lint-stability-fields.rs:56:17
   |
 LL |         let x = Unstable {
@ -7,7 +7,7 @@ LL |         let x = Unstable {
   = help: add `#![feature(unstable_test_feature)]` to the crate attributes to enable
   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date

-error[E0658]: use of unstable library feature 'unstable_test_feature'
+error[E0658]: use of unstable library feature `unstable_test_feature`
  --> $DIR/lint-stability-fields.rs:66:13
   |
 LL |         let Unstable {
@ -16,7 +16,7 @@ LL |         let Unstable {
   = help: add `#![feature(unstable_test_feature)]` to the crate attributes to enable
   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date

-error[E0658]: use of unstable library feature 'unstable_test_feature'
+error[E0658]: use of unstable library feature `unstable_test_feature`
  --> $DIR/lint-stability-fields.rs:72:13
   |
 LL |         let Unstable
@ -25,7 +25,7 @@ LL |         let Unstable
   = help: add `#![feature(unstable_test_feature)]` to the crate attributes to enable
   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date

-error[E0658]: use of unstable library feature 'unstable_test_feature'
+error[E0658]: use of unstable library feature `unstable_test_feature`
  --> $DIR/lint-stability-fields.rs:77:17
   |
 LL |         let x = reexport::Unstable2(1, 2, 3);
@ -34,7 +34,7 @@ LL |         let x = reexport::Unstable2(1, 2, 3);
   = help: add `#![feature(unstable_test_feature)]` to the crate attributes to enable
   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date

-error[E0658]: use of unstable library feature 'unstable_test_feature'
+error[E0658]: use of unstable library feature `unstable_test_feature`
  --> $DIR/lint-stability-fields.rs:79:17
   |
 LL |         let x = Unstable2(1, 2, 3);
@ -43,7 +43,7 @@ LL |         let x = Unstable2(1, 2, 3);
   = help: add `#![feature(unstable_test_feature)]` to the crate attributes to enable
   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date

-error[E0658]: use of unstable library feature 'unstable_test_feature'
+error[E0658]: use of unstable library feature `unstable_test_feature`
  --> $DIR/lint-stability-fields.rs:85:13
   |
 LL |         let Unstable2
@ -52,7 +52,7 @@ LL |         let Unstable2
   = help: add `#![feature(unstable_test_feature)]` to the crate attributes to enable
   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date

-error[E0658]: use of unstable library feature 'unstable_test_feature'
+error[E0658]: use of unstable library feature `unstable_test_feature`
  --> $DIR/lint-stability-fields.rs:90:13
   |
 LL |         let Unstable2
@ -61,7 +61,7 @@ LL |         let Unstable2
   = help: add `#![feature(unstable_test_feature)]` to the crate attributes to enable
   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date

-error[E0658]: use of unstable library feature 'unstable_test_feature'
+error[E0658]: use of unstable library feature `unstable_test_feature`
  --> $DIR/lint-stability-fields.rs:95:17
   |
 LL |         let x = Deprecated {
@ -70,7 +70,7 @@ LL |         let x = Deprecated {
   = help: add `#![feature(unstable_test_feature)]` to the crate attributes to enable
   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date

-error[E0658]: use of unstable library feature 'unstable_test_feature'
+error[E0658]: use of unstable library feature `unstable_test_feature`
  --> $DIR/lint-stability-fields.rs:105:13
   |
 LL |         let Deprecated {
@ -79,7 +79,7 @@ LL |         let Deprecated {
   = help: add `#![feature(unstable_test_feature)]` to the crate attributes to enable
   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date

-error[E0658]: use of unstable library feature 'unstable_test_feature'
+error[E0658]: use of unstable library feature `unstable_test_feature`
  --> $DIR/lint-stability-fields.rs:111:13
   |
 LL |         let Deprecated
@ -88,7 +88,7 @@ LL |         let Deprecated
   = help: add `#![feature(unstable_test_feature)]` to the crate attributes to enable
   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date

-error[E0658]: use of unstable library feature 'unstable_test_feature'
+error[E0658]: use of unstable library feature `unstable_test_feature`
  --> $DIR/lint-stability-fields.rs:115:17
   |
 LL |         let x = Deprecated2(1, 2, 3);
@ -97,7 +97,7 @@ LL |         let x = Deprecated2(1, 2, 3);
   = help: add `#![feature(unstable_test_feature)]` to the crate attributes to enable
   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date

-error[E0658]: use of unstable library feature 'unstable_test_feature'
+error[E0658]: use of unstable library feature `unstable_test_feature`
  --> $DIR/lint-stability-fields.rs:121:13
   |
 LL |         let Deprecated2
@ -106,7 +106,7 @@ LL |         let Deprecated2
   = help: add `#![feature(unstable_test_feature)]` to the crate attributes to enable
   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date

-error[E0658]: use of unstable library feature 'unstable_test_feature'
+error[E0658]: use of unstable library feature `unstable_test_feature`
  --> $DIR/lint-stability-fields.rs:126:13
   |
 LL |         let Deprecated2
@ -115,7 +115,7 @@ LL |         let Deprecated2
   = help: add `#![feature(unstable_test_feature)]` to the crate attributes to enable
   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date

-error[E0658]: use of unstable library feature 'unstable_test_feature'
+error[E0658]: use of unstable library feature `unstable_test_feature`
  --> $DIR/lint-stability-fields.rs:21:13
   |
 LL |             override1: 2,
@ -124,7 +124,7 @@ LL |             override1: 2,
   = help: add `#![feature(unstable_test_feature)]` to the crate attributes to enable
   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date

-error[E0658]: use of unstable library feature 'unstable_test_feature'
+error[E0658]: use of unstable library feature `unstable_test_feature`
  --> $DIR/lint-stability-fields.rs:22:13
   |
 LL |             override2: 3,
@ -133,7 +133,7 @@ LL |             override2: 3,
   = help: add `#![feature(unstable_test_feature)]` to the crate attributes to enable
   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date

-error[E0658]: use of unstable library feature 'unstable_test_feature'
+error[E0658]: use of unstable library feature `unstable_test_feature`
  --> $DIR/lint-stability-fields.rs:27:17
   |
 LL |         let _ = x.override1;
@ -142,7 +142,7 @@ LL |         let _ = x.override1;
   = help: add `#![feature(unstable_test_feature)]` to the crate attributes to enable
   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date

-error[E0658]: use of unstable library feature 'unstable_test_feature'
+error[E0658]: use of unstable library feature `unstable_test_feature`
  --> $DIR/lint-stability-fields.rs:28:17
   |
 LL |         let _ = x.override2;
@ -151,7 +151,7 @@ LL |         let _ = x.override2;
   = help: add `#![feature(unstable_test_feature)]` to the crate attributes to enable
   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date

-error[E0658]: use of unstable library feature 'unstable_test_feature'
+error[E0658]: use of unstable library feature `unstable_test_feature`
  --> $DIR/lint-stability-fields.rs:33:13
   |
 LL |             override1: _,
@ -160,7 +160,7 @@ LL |             override1: _,
   = help: add `#![feature(unstable_test_feature)]` to the crate attributes to enable
   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date

-error[E0658]: use of unstable library feature 'unstable_test_feature'
+error[E0658]: use of unstable library feature `unstable_test_feature`
  --> $DIR/lint-stability-fields.rs:34:13
   |
 LL |             override2: _,
@ -169,7 +169,7 @@ LL |             override2: _,
   = help: add `#![feature(unstable_test_feature)]` to the crate attributes to enable
   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date

-error[E0658]: use of unstable library feature 'unstable_test_feature'
+error[E0658]: use of unstable library feature `unstable_test_feature`
  --> $DIR/lint-stability-fields.rs:43:17
   |
 LL |         let _ = x.1;
@ -178,7 +178,7 @@ LL |         let _ = x.1;
   = help: add `#![feature(unstable_test_feature)]` to the crate attributes to enable
   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date

-error[E0658]: use of unstable library feature 'unstable_test_feature'
+error[E0658]: use of unstable library feature `unstable_test_feature`
  --> $DIR/lint-stability-fields.rs:44:17
   |
 LL |         let _ = x.2;
@ -187,7 +187,7 @@ LL |         let _ = x.2;
   = help: add `#![feature(unstable_test_feature)]` to the crate attributes to enable
   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date

-error[E0658]: use of unstable library feature 'unstable_test_feature'
+error[E0658]: use of unstable library feature `unstable_test_feature`
  --> $DIR/lint-stability-fields.rs:48:20
   |
 LL |                    _,
@ -196,7 +196,7 @@ LL |                    _,
   = help: add `#![feature(unstable_test_feature)]` to the crate attributes to enable
   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date

-error[E0658]: use of unstable library feature 'unstable_test_feature'
+error[E0658]: use of unstable library feature `unstable_test_feature`
  --> $DIR/lint-stability-fields.rs:49:20
   |
 LL |                    _,
@ -205,7 +205,7 @@ LL |                    _,
   = help: add `#![feature(unstable_test_feature)]` to the crate attributes to enable
   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date

-error[E0658]: use of unstable library feature 'unstable_test_feature'
+error[E0658]: use of unstable library feature `unstable_test_feature`
  --> $DIR/lint-stability-fields.rs:57:13
   |
 LL |             inherit: 1,
@ -214,7 +214,7 @@ LL |             inherit: 1,
   = help: add `#![feature(unstable_test_feature)]` to the crate attributes to enable
   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date

-error[E0658]: use of unstable library feature 'unstable_test_feature'
+error[E0658]: use of unstable library feature `unstable_test_feature`
  --> $DIR/lint-stability-fields.rs:59:13
   |
 LL |             override2: 3,
@ -223,7 +223,7 @@ LL |             override2: 3,
   = help: add `#![feature(unstable_test_feature)]` to the crate attributes to enable
   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date

-error[E0658]: use of unstable library feature 'unstable_test_feature'
+error[E0658]: use of unstable library feature `unstable_test_feature`
  --> $DIR/lint-stability-fields.rs:62:17
   |
 LL |         let _ = x.inherit;
@ -232,7 +232,7 @@ LL |         let _ = x.inherit;
   = help: add `#![feature(unstable_test_feature)]` to the crate attributes to enable
   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date

-error[E0658]: use of unstable library feature 'unstable_test_feature'
+error[E0658]: use of unstable library feature `unstable_test_feature`
  --> $DIR/lint-stability-fields.rs:64:17
   |
 LL |         let _ = x.override2;
@ -241,7 +241,7 @@ LL |         let _ = x.override2;
   = help: add `#![feature(unstable_test_feature)]` to the crate attributes to enable
   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date

-error[E0658]: use of unstable library feature 'unstable_test_feature'
+error[E0658]: use of unstable library feature `unstable_test_feature`
  --> $DIR/lint-stability-fields.rs:67:13
   |
 LL |             inherit: _,
@ -250,7 +250,7 @@ LL |             inherit: _,
   = help: add `#![feature(unstable_test_feature)]` to the crate attributes to enable
   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date

-error[E0658]: use of unstable library feature 'unstable_test_feature'
+error[E0658]: use of unstable library feature `unstable_test_feature`
  --> $DIR/lint-stability-fields.rs:69:13
   |
 LL |             override2: _
@ -259,7 +259,7 @@ LL |             override2: _
   = help: add `#![feature(unstable_test_feature)]` to the crate attributes to enable
   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date

-error[E0658]: use of unstable library feature 'unstable_test_feature'
+error[E0658]: use of unstable library feature `unstable_test_feature`
  --> $DIR/lint-stability-fields.rs:81:17
   |
 LL |         let _ = x.0;
@ -268,7 +268,7 @@ LL |         let _ = x.0;
   = help: add `#![feature(unstable_test_feature)]` to the crate attributes to enable
   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date

-error[E0658]: use of unstable library feature 'unstable_test_feature'
+error[E0658]: use of unstable library feature `unstable_test_feature`
  --> $DIR/lint-stability-fields.rs:83:17
   |
 LL |         let _ = x.2;
@ -277,7 +277,7 @@ LL |         let _ = x.2;
   = help: add `#![feature(unstable_test_feature)]` to the crate attributes to enable
   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date

-error[E0658]: use of unstable library feature 'unstable_test_feature'
+error[E0658]: use of unstable library feature `unstable_test_feature`
  --> $DIR/lint-stability-fields.rs:86:14
   |
 LL |             (_,
@ -286,7 +286,7 @@ LL |             (_,
   = help: add `#![feature(unstable_test_feature)]` to the crate attributes to enable
   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date

-error[E0658]: use of unstable library feature 'unstable_test_feature'
+error[E0658]: use of unstable library feature `unstable_test_feature`
  --> $DIR/lint-stability-fields.rs:88:14
   |
 LL |              _)
@ -295,7 +295,7 @@ LL |              _)
   = help: add `#![feature(unstable_test_feature)]` to the crate attributes to enable
   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date

-error[E0658]: use of unstable library feature 'unstable_test_feature'
+error[E0658]: use of unstable library feature `unstable_test_feature`
  --> $DIR/lint-stability-fields.rs:96:13
   |
 LL |             inherit: 1,
@ -304,7 +304,7 @@ LL |             inherit: 1,
   = help: add `#![feature(unstable_test_feature)]` to the crate attributes to enable
   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date

-error[E0658]: use of unstable library feature 'unstable_test_feature'
+error[E0658]: use of unstable library feature `unstable_test_feature`
  --> $DIR/lint-stability-fields.rs:98:13
   |
 LL |             override2: 3,
@ -313,7 +313,7 @@ LL |             override2: 3,
   = help: add `#![feature(unstable_test_feature)]` to the crate attributes to enable
   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date

-error[E0658]: use of unstable library feature 'unstable_test_feature'
+error[E0658]: use of unstable library feature `unstable_test_feature`
  --> $DIR/lint-stability-fields.rs:101:17
   |
 LL |         let _ = x.inherit;
@ -322,7 +322,7 @@ LL |         let _ = x.inherit;
   = help: add `#![feature(unstable_test_feature)]` to the crate attributes to enable
   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date

-error[E0658]: use of unstable library feature 'unstable_test_feature'
+error[E0658]: use of unstable library feature `unstable_test_feature`
  --> $DIR/lint-stability-fields.rs:103:17
   |
 LL |         let _ = x.override2;
@ -331,7 +331,7 @@ LL |         let _ = x.override2;
   = help: add `#![feature(unstable_test_feature)]` to the crate attributes to enable
   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date

-error[E0658]: use of unstable library feature 'unstable_test_feature'
+error[E0658]: use of unstable library feature `unstable_test_feature`
  --> $DIR/lint-stability-fields.rs:106:13
   |
 LL |             inherit: _,
@ -340,7 +340,7 @@ LL |             inherit: _,
   = help: add `#![feature(unstable_test_feature)]` to the crate attributes to enable
   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date

-error[E0658]: use of unstable library feature 'unstable_test_feature'
+error[E0658]: use of unstable library feature `unstable_test_feature`
  --> $DIR/lint-stability-fields.rs:108:13
   |
 LL |             override2: _
@ -349,7 +349,7 @@ LL |             override2: _
   = help: add `#![feature(unstable_test_feature)]` to the crate attributes to enable
   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date

-error[E0658]: use of unstable library feature 'unstable_test_feature'
+error[E0658]: use of unstable library feature `unstable_test_feature`
  --> $DIR/lint-stability-fields.rs:117:17
   |
 LL |         let _ = x.0;
@ -358,7 +358,7 @@ LL |         let _ = x.0;
   = help: add `#![feature(unstable_test_feature)]` to the crate attributes to enable
   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date

-error[E0658]: use of unstable library feature 'unstable_test_feature'
+error[E0658]: use of unstable library feature `unstable_test_feature`
  --> $DIR/lint-stability-fields.rs:119:17
   |
 LL |         let _ = x.2;
@ -367,7 +367,7 @@ LL |         let _ = x.2;
   = help: add `#![feature(unstable_test_feature)]` to the crate attributes to enable
   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date

-error[E0658]: use of unstable library feature 'unstable_test_feature'
+error[E0658]: use of unstable library feature `unstable_test_feature`
  --> $DIR/lint-stability-fields.rs:122:14
   |
 LL |             (_,
@ -376,7 +376,7 @@ LL |             (_,
   = help: add `#![feature(unstable_test_feature)]` to the crate attributes to enable
   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date

-error[E0658]: use of unstable library feature 'unstable_test_feature'
+error[E0658]: use of unstable library feature `unstable_test_feature`
  --> $DIR/lint-stability-fields.rs:124:14
   |
 LL |              _)
--- a/tests/ui/lint/lint-stability.rs
+++ b/tests/ui/lint/lint-stability.rs
@ -61,11 +61,11 @@ mod cross_crate {
        <Foo as Trait>::trait_unstable(&foo); //~ ERROR use of unstable library feature

        unstable_text();
-        //~^ ERROR use of unstable library feature 'unstable_test_feature': text
+        //~^ ERROR use of unstable library feature `unstable_test_feature`: text
        Trait::trait_unstable_text(&foo);
-        //~^ ERROR use of unstable library feature 'unstable_test_feature': text
+        //~^ ERROR use of unstable library feature `unstable_test_feature`: text
        <Foo as Trait>::trait_unstable_text(&foo);
-        //~^ ERROR use of unstable library feature 'unstable_test_feature': text
+        //~^ ERROR use of unstable library feature `unstable_test_feature`: text

        stable();
        foo.method_stable();
@ -152,9 +152,9 @@ mod cross_crate {
        Trait::trait_unstable(&foo); //~ ERROR use of unstable library feature
        <Foo as Trait>::trait_unstable(&foo); //~ ERROR use of unstable library feature
        Trait::trait_unstable_text(&foo);
-        //~^ ERROR use of unstable library feature 'unstable_test_feature': text
+        //~^ ERROR use of unstable library feature `unstable_test_feature`: text
        <Foo as Trait>::trait_unstable_text(&foo);
-        //~^ ERROR use of unstable library feature 'unstable_test_feature': text
+        //~^ ERROR use of unstable library feature `unstable_test_feature`: text
        foo.trait_stable();
        Trait::trait_stable(&foo);
        <Foo>::trait_stable(&foo);
--- a/tests/ui/lint/lint-stability.stderr
+++ b/tests/ui/lint/lint-stability.stderr
@ -1,4 +1,4 @@
-error[E0658]: use of unstable library feature 'unstable_test_feature'
+error[E0658]: use of unstable library feature `unstable_test_feature`
  --> $DIR/lint-stability.rs:17:5
   |
 LL |     extern crate stability_cfg2;
@ -7,7 +7,7 @@ LL |     extern crate stability_cfg2;
   = help: add `#![feature(unstable_test_feature)]` to the crate attributes to enable
   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date

-error[E0658]: use of unstable library feature 'unstable_test_feature'
+error[E0658]: use of unstable library feature `unstable_test_feature`
  --> $DIR/lint-stability.rs:45:9
   |
 LL |         deprecated_unstable();
@ -16,7 +16,7 @@ LL |         deprecated_unstable();
   = help: add `#![feature(unstable_test_feature)]` to the crate attributes to enable
   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date

-error[E0658]: use of unstable library feature 'unstable_test_feature'
+error[E0658]: use of unstable library feature `unstable_test_feature`
  --> $DIR/lint-stability.rs:47:9
   |
 LL |         Trait::trait_deprecated_unstable(&foo);
@ -25,7 +25,7 @@ LL |         Trait::trait_deprecated_unstable(&foo);
   = help: add `#![feature(unstable_test_feature)]` to the crate attributes to enable
   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date

-error[E0658]: use of unstable library feature 'unstable_test_feature'
+error[E0658]: use of unstable library feature `unstable_test_feature`
  --> $DIR/lint-stability.rs:49:9
   |
 LL |         <Foo as Trait>::trait_deprecated_unstable(&foo);
@ -34,7 +34,7 @@ LL |         <Foo as Trait>::trait_deprecated_unstable(&foo);
   = help: add `#![feature(unstable_test_feature)]` to the crate attributes to enable
   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date

-error[E0658]: use of unstable library feature 'unstable_test_feature'
+error[E0658]: use of unstable library feature `unstable_test_feature`
  --> $DIR/lint-stability.rs:52:9
   |
 LL |         deprecated_unstable_text();
@ -43,7 +43,7 @@ LL |         deprecated_unstable_text();
   = help: add `#![feature(unstable_test_feature)]` to the crate attributes to enable
   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date

-error[E0658]: use of unstable library feature 'unstable_test_feature'
+error[E0658]: use of unstable library feature `unstable_test_feature`
  --> $DIR/lint-stability.rs:54:9
   |
 LL |         Trait::trait_deprecated_unstable_text(&foo);
@ -52,7 +52,7 @@ LL |         Trait::trait_deprecated_unstable_text(&foo);
   = help: add `#![feature(unstable_test_feature)]` to the crate attributes to enable
   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date

-error[E0658]: use of unstable library feature 'unstable_test_feature'
+error[E0658]: use of unstable library feature `unstable_test_feature`
  --> $DIR/lint-stability.rs:56:9
   |
 LL |         <Foo as Trait>::trait_deprecated_unstable_text(&foo);
@ -61,7 +61,7 @@ LL |         <Foo as Trait>::trait_deprecated_unstable_text(&foo);
   = help: add `#![feature(unstable_test_feature)]` to the crate attributes to enable
   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date

-error[E0658]: use of unstable library feature 'unstable_test_feature'
+error[E0658]: use of unstable library feature `unstable_test_feature`
  --> $DIR/lint-stability.rs:59:9
   |
 LL |         unstable();
@ -70,7 +70,7 @@ LL |         unstable();
   = help: add `#![feature(unstable_test_feature)]` to the crate attributes to enable
   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date

-error[E0658]: use of unstable library feature 'unstable_test_feature'
+error[E0658]: use of unstable library feature `unstable_test_feature`
  --> $DIR/lint-stability.rs:60:9
   |
 LL |         Trait::trait_unstable(&foo);
@ -79,7 +79,7 @@ LL |         Trait::trait_unstable(&foo);
   = help: add `#![feature(unstable_test_feature)]` to the crate attributes to enable
   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date

-error[E0658]: use of unstable library feature 'unstable_test_feature'
+error[E0658]: use of unstable library feature `unstable_test_feature`
  --> $DIR/lint-stability.rs:61:9
   |
 LL |         <Foo as Trait>::trait_unstable(&foo);
@ -88,7 +88,7 @@ LL |         <Foo as Trait>::trait_unstable(&foo);
   = help: add `#![feature(unstable_test_feature)]` to the crate attributes to enable
   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date

-error[E0658]: use of unstable library feature 'unstable_test_feature': text
+error[E0658]: use of unstable library feature `unstable_test_feature`: text
  --> $DIR/lint-stability.rs:63:9
   |
 LL |         unstable_text();
@ -97,7 +97,7 @@ LL |         unstable_text();
   = help: add `#![feature(unstable_test_feature)]` to the crate attributes to enable
   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date

-error[E0658]: use of unstable library feature 'unstable_test_feature': text
+error[E0658]: use of unstable library feature `unstable_test_feature`: text
  --> $DIR/lint-stability.rs:65:9
   |
 LL |         Trait::trait_unstable_text(&foo);
@ -106,7 +106,7 @@ LL |         Trait::trait_unstable_text(&foo);
   = help: add `#![feature(unstable_test_feature)]` to the crate attributes to enable
   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date

-error[E0658]: use of unstable library feature 'unstable_test_feature': text
+error[E0658]: use of unstable library feature `unstable_test_feature`: text
  --> $DIR/lint-stability.rs:67:9
   |
 LL |         <Foo as Trait>::trait_unstable_text(&foo);
@ -115,7 +115,7 @@ LL |         <Foo as Trait>::trait_unstable_text(&foo);
   = help: add `#![feature(unstable_test_feature)]` to the crate attributes to enable
   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date

-error[E0658]: use of unstable library feature 'unstable_test_feature'
+error[E0658]: use of unstable library feature `unstable_test_feature`
  --> $DIR/lint-stability.rs:99:17
   |
 LL |         let _ = DeprecatedUnstableStruct {
@ -124,7 +124,7 @@ LL |         let _ = DeprecatedUnstableStruct {
   = help: add `#![feature(unstable_test_feature)]` to the crate attributes to enable
   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date

-error[E0658]: use of unstable library feature 'unstable_test_feature'
+error[E0658]: use of unstable library feature `unstable_test_feature`
  --> $DIR/lint-stability.rs:103:17
   |
 LL |         let _ = UnstableStruct { i: 0 };
@ -133,7 +133,7 @@ LL |         let _ = UnstableStruct { i: 0 };
   = help: add `#![feature(unstable_test_feature)]` to the crate attributes to enable
   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date

-error[E0658]: use of unstable library feature 'unstable_test_feature'
+error[E0658]: use of unstable library feature `unstable_test_feature`
  --> $DIR/lint-stability.rs:107:17
   |
 LL |         let _ = DeprecatedUnstableUnitStruct;
@ -142,7 +142,7 @@ LL |         let _ = DeprecatedUnstableUnitStruct;
   = help: add `#![feature(unstable_test_feature)]` to the crate attributes to enable
   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date

-error[E0658]: use of unstable library feature 'unstable_test_feature'
+error[E0658]: use of unstable library feature `unstable_test_feature`
  --> $DIR/lint-stability.rs:109:17
   |
 LL |         let _ = UnstableUnitStruct;
@ -151,7 +151,7 @@ LL |         let _ = UnstableUnitStruct;
   = help: add `#![feature(unstable_test_feature)]` to the crate attributes to enable
   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date

-error[E0658]: use of unstable library feature 'unstable_test_feature'
+error[E0658]: use of unstable library feature `unstable_test_feature`
  --> $DIR/lint-stability.rs:113:17
   |
 LL |         let _ = Enum::DeprecatedUnstableVariant;
@ -160,7 +160,7 @@ LL |         let _ = Enum::DeprecatedUnstableVariant;
   = help: add `#![feature(unstable_test_feature)]` to the crate attributes to enable
   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date

-error[E0658]: use of unstable library feature 'unstable_test_feature'
+error[E0658]: use of unstable library feature `unstable_test_feature`
  --> $DIR/lint-stability.rs:115:17
   |
 LL |         let _ = Enum::UnstableVariant;
@ -169,7 +169,7 @@ LL |         let _ = Enum::UnstableVariant;
   = help: add `#![feature(unstable_test_feature)]` to the crate attributes to enable
   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date

-error[E0658]: use of unstable library feature 'unstable_test_feature'
+error[E0658]: use of unstable library feature `unstable_test_feature`
  --> $DIR/lint-stability.rs:119:17
   |
 LL |         let _ = DeprecatedUnstableTupleStruct (1);
@ -178,7 +178,7 @@ LL |         let _ = DeprecatedUnstableTupleStruct (1);
   = help: add `#![feature(unstable_test_feature)]` to the crate attributes to enable
   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date

-error[E0658]: use of unstable library feature 'unstable_test_feature'
+error[E0658]: use of unstable library feature `unstable_test_feature`
  --> $DIR/lint-stability.rs:121:17
   |
 LL |         let _ = UnstableTupleStruct (1);
@ -187,7 +187,7 @@ LL |         let _ = UnstableTupleStruct (1);
   = help: add `#![feature(unstable_test_feature)]` to the crate attributes to enable
   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date

-error[E0658]: use of unstable library feature 'unstable_test_feature'
+error[E0658]: use of unstable library feature `unstable_test_feature`
  --> $DIR/lint-stability.rs:130:25
   |
 LL |         macro_test_arg!(deprecated_unstable_text());
@ -196,7 +196,7 @@ LL |         macro_test_arg!(deprecated_unstable_text());
   = help: add `#![feature(unstable_test_feature)]` to the crate attributes to enable
   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date

-error[E0658]: use of unstable library feature 'unstable_test_feature'
+error[E0658]: use of unstable library feature `unstable_test_feature`
  --> $DIR/lint-stability.rs:144:9
   |
 LL |         Trait::trait_deprecated_unstable(&foo);
@ -205,7 +205,7 @@ LL |         Trait::trait_deprecated_unstable(&foo);
   = help: add `#![feature(unstable_test_feature)]` to the crate attributes to enable
   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date

-error[E0658]: use of unstable library feature 'unstable_test_feature'
+error[E0658]: use of unstable library feature `unstable_test_feature`
  --> $DIR/lint-stability.rs:146:9
   |
 LL |         <Foo as Trait>::trait_deprecated_unstable(&foo);
@ -214,7 +214,7 @@ LL |         <Foo as Trait>::trait_deprecated_unstable(&foo);
   = help: add `#![feature(unstable_test_feature)]` to the crate attributes to enable
   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date

-error[E0658]: use of unstable library feature 'unstable_test_feature'
+error[E0658]: use of unstable library feature `unstable_test_feature`
  --> $DIR/lint-stability.rs:148:9
   |
 LL |         Trait::trait_deprecated_unstable_text(&foo);
@ -223,7 +223,7 @@ LL |         Trait::trait_deprecated_unstable_text(&foo);
   = help: add `#![feature(unstable_test_feature)]` to the crate attributes to enable
   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date

-error[E0658]: use of unstable library feature 'unstable_test_feature'
+error[E0658]: use of unstable library feature `unstable_test_feature`
  --> $DIR/lint-stability.rs:150:9
   |
 LL |         <Foo as Trait>::trait_deprecated_unstable_text(&foo);
@ -232,7 +232,7 @@ LL |         <Foo as Trait>::trait_deprecated_unstable_text(&foo);
   = help: add `#![feature(unstable_test_feature)]` to the crate attributes to enable
   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date

-error[E0658]: use of unstable library feature 'unstable_test_feature'
+error[E0658]: use of unstable library feature `unstable_test_feature`
  --> $DIR/lint-stability.rs:152:9
   |
 LL |         Trait::trait_unstable(&foo);
@ -241,7 +241,7 @@ LL |         Trait::trait_unstable(&foo);
   = help: add `#![feature(unstable_test_feature)]` to the crate attributes to enable
   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date

-error[E0658]: use of unstable library feature 'unstable_test_feature'
+error[E0658]: use of unstable library feature `unstable_test_feature`
  --> $DIR/lint-stability.rs:153:9
   |
 LL |         <Foo as Trait>::trait_unstable(&foo);
@ -250,7 +250,7 @@ LL |         <Foo as Trait>::trait_unstable(&foo);
   = help: add `#![feature(unstable_test_feature)]` to the crate attributes to enable
   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date

-error[E0658]: use of unstable library feature 'unstable_test_feature': text
+error[E0658]: use of unstable library feature `unstable_test_feature`: text
  --> $DIR/lint-stability.rs:154:9
   |
 LL |         Trait::trait_unstable_text(&foo);
@ -259,7 +259,7 @@ LL |         Trait::trait_unstable_text(&foo);
   = help: add `#![feature(unstable_test_feature)]` to the crate attributes to enable
   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date

-error[E0658]: use of unstable library feature 'unstable_test_feature': text
+error[E0658]: use of unstable library feature `unstable_test_feature`: text
  --> $DIR/lint-stability.rs:156:9
   |
 LL |         <Foo as Trait>::trait_unstable_text(&foo);
@ -268,7 +268,7 @@ LL |         <Foo as Trait>::trait_unstable_text(&foo);
   = help: add `#![feature(unstable_test_feature)]` to the crate attributes to enable
   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date

-error[E0658]: use of unstable library feature 'unstable_test_feature'
+error[E0658]: use of unstable library feature `unstable_test_feature`
  --> $DIR/lint-stability.rs:172:10
   |
 LL |     impl UnstableTrait for S { }
@ -277,7 +277,7 @@ LL |     impl UnstableTrait for S { }
   = help: add `#![feature(unstable_test_feature)]` to the crate attributes to enable
   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date

-error[E0658]: use of unstable library feature 'unstable_test_feature'
+error[E0658]: use of unstable library feature `unstable_test_feature`
  --> $DIR/lint-stability.rs:174:24
   |
 LL |     trait LocalTrait : UnstableTrait { }
@ -286,7 +286,7 @@ LL |     trait LocalTrait : UnstableTrait { }
   = help: add `#![feature(unstable_test_feature)]` to the crate attributes to enable
   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date

-error[E0658]: use of unstable library feature 'unstable_test_feature'
+error[E0658]: use of unstable library feature `unstable_test_feature`
  --> $DIR/lint-stability.rs:179:9
   |
 LL |         fn trait_unstable(&self) {}
@ -295,7 +295,7 @@ LL |         fn trait_unstable(&self) {}
   = help: add `#![feature(unstable_test_feature)]` to the crate attributes to enable
   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date

-error[E0658]: use of unstable library feature 'unstable_test_feature'
+error[E0658]: use of unstable library feature `unstable_test_feature`
  --> $DIR/lint-stability.rs:184:5
   |
 LL |     extern crate inherited_stability;
@ -304,7 +304,7 @@ LL |     extern crate inherited_stability;
   = help: add `#![feature(unstable_test_feature)]` to the crate attributes to enable
   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date

-error[E0658]: use of unstable library feature 'unstable_test_feature'
+error[E0658]: use of unstable library feature `unstable_test_feature`
  --> $DIR/lint-stability.rs:185:9
   |
 LL |     use self::inherited_stability::*;
@ -313,7 +313,7 @@ LL |     use self::inherited_stability::*;
   = help: add `#![feature(unstable_test_feature)]` to the crate attributes to enable
   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date

-error[E0658]: use of unstable library feature 'unstable_test_feature'
+error[E0658]: use of unstable library feature `unstable_test_feature`
  --> $DIR/lint-stability.rs:188:9
   |
 LL |         unstable();
@ -322,7 +322,7 @@ LL |         unstable();
   = help: add `#![feature(unstable_test_feature)]` to the crate attributes to enable
   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date

-error[E0658]: use of unstable library feature 'unstable_test_feature'
+error[E0658]: use of unstable library feature `unstable_test_feature`
  --> $DIR/lint-stability.rs:191:9
   |
 LL |         stable_mod::unstable();
@ -331,7 +331,7 @@ LL |         stable_mod::unstable();
   = help: add `#![feature(unstable_test_feature)]` to the crate attributes to enable
   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date

-error[E0658]: use of unstable library feature 'unstable_test_feature'
+error[E0658]: use of unstable library feature `unstable_test_feature`
  --> $DIR/lint-stability.rs:194:9
   |
 LL |         unstable_mod::deprecated();
@ -340,7 +340,7 @@ LL |         unstable_mod::deprecated();
   = help: add `#![feature(unstable_test_feature)]` to the crate attributes to enable
   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date

-error[E0658]: use of unstable library feature 'unstable_test_feature'
+error[E0658]: use of unstable library feature `unstable_test_feature`
  --> $DIR/lint-stability.rs:195:9
   |
 LL |         unstable_mod::unstable();
@ -349,7 +349,7 @@ LL |         unstable_mod::unstable();
   = help: add `#![feature(unstable_test_feature)]` to the crate attributes to enable
   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date

-error[E0658]: use of unstable library feature 'unstable_test_feature'
+error[E0658]: use of unstable library feature `unstable_test_feature`
  --> $DIR/lint-stability.rs:197:17
   |
 LL |         let _ = Unstable::UnstableVariant;
@ -358,7 +358,7 @@ LL |         let _ = Unstable::UnstableVariant;
   = help: add `#![feature(unstable_test_feature)]` to the crate attributes to enable
   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date

-error[E0658]: use of unstable library feature 'unstable_test_feature'
+error[E0658]: use of unstable library feature `unstable_test_feature`
  --> $DIR/lint-stability.rs:198:17
   |
 LL |         let _ = Unstable::StableVariant;
@ -367,7 +367,7 @@ LL |         let _ = Unstable::StableVariant;
   = help: add `#![feature(unstable_test_feature)]` to the crate attributes to enable
   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date

-error[E0658]: use of unstable library feature 'unstable_test_feature'
+error[E0658]: use of unstable library feature `unstable_test_feature`
  --> $DIR/lint-stability.rs:88:48
   |
 LL |         struct S1<T: TraitWithAssociatedTypes>(T::TypeUnstable);
@ -376,7 +376,7 @@ LL |         struct S1<T: TraitWithAssociatedTypes>(T::TypeUnstable);
   = help: add `#![feature(unstable_test_feature)]` to the crate attributes to enable
   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date

-error[E0658]: use of unstable library feature 'unstable_test_feature'
+error[E0658]: use of unstable library feature `unstable_test_feature`
  --> $DIR/lint-stability.rs:92:13
   |
 LL |             TypeUnstable = u8,
--- a/tests/ui/macros/macro-stability.rs
+++ b/tests/ui/macros/macro-stability.rs
@ -19,10 +19,10 @@ macro local_unstable_modern() {}
 macro_rules! local_deprecated{ () => () }

 fn main() {
-    local_unstable!(); //~ ERROR use of unstable library feature 'local_unstable'
-    local_unstable_modern!(); //~ ERROR use of unstable library feature 'local_unstable'
-    unstable_macro!(); //~ ERROR use of unstable library feature 'unstable_macros'
-    // unstable_macro_modern!(); // ERROR use of unstable library feature 'unstable_macros'
+    local_unstable!(); //~ ERROR use of unstable library feature `local_unstable`
+    local_unstable_modern!(); //~ ERROR use of unstable library feature `local_unstable`
+    unstable_macro!(); //~ ERROR use of unstable library feature `unstable_macros`
+    // unstable_macro_modern!(); // ERROR use of unstable library feature `unstable_macros`

    deprecated_macro!();
    //~^ WARN use of deprecated macro `deprecated_macro`: deprecation note
--- a/tests/ui/macros/macro-stability.stderr
+++ b/tests/ui/macros/macro-stability.stderr
@ -1,4 +1,4 @@
-error[E0658]: use of unstable library feature 'local_unstable'
+error[E0658]: use of unstable library feature `local_unstable`
  --> $DIR/macro-stability.rs:22:5
   |
 LL |     local_unstable!();
@ -7,7 +7,7 @@ LL |     local_unstable!();
   = help: add `#![feature(local_unstable)]` to the crate attributes to enable
   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date

-error[E0658]: use of unstable library feature 'local_unstable'
+error[E0658]: use of unstable library feature `local_unstable`
  --> $DIR/macro-stability.rs:23:5
   |
 LL |     local_unstable_modern!();
@ -16,7 +16,7 @@ LL |     local_unstable_modern!();
   = help: add `#![feature(local_unstable)]` to the crate attributes to enable
   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date

-error[E0658]: use of unstable library feature 'unstable_macros'
+error[E0658]: use of unstable library feature `unstable_macros`
  --> $DIR/macro-stability.rs:24:5
   |
 LL |     unstable_macro!();
--- a/tests/ui/offset-of/offset-of-unstable.stderr
+++ b/tests/ui/offset-of/offset-of-unstable.stderr
@ -1,4 +1,4 @@
-error[E0658]: use of unstable library feature 'unstable_test_feature'
+error[E0658]: use of unstable library feature `unstable_test_feature`
  --> $DIR/offset-of-unstable.rs:12:9
   |
 LL |         Unstable,
@ -7,7 +7,7 @@ LL |         Unstable,
   = help: add `#![feature(unstable_test_feature)]` to the crate attributes to enable
   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date

-error[E0658]: use of unstable library feature 'unstable_test_feature'
+error[E0658]: use of unstable library feature `unstable_test_feature`
  --> $DIR/offset-of-unstable.rs:21:9
   |
 LL |         UnstableWithStableFieldType,
@ -16,7 +16,7 @@ LL |         UnstableWithStableFieldType,
   = help: add `#![feature(unstable_test_feature)]` to the crate attributes to enable
   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date

-error[E0658]: use of unstable library feature 'unstable_test_feature'
+error[E0658]: use of unstable library feature `unstable_test_feature`
  --> $DIR/offset-of-unstable.rs:26:9
   |
 LL |         UnstableWithStableFieldType,
@ -25,7 +25,7 @@ LL |         UnstableWithStableFieldType,
   = help: add `#![feature(unstable_test_feature)]` to the crate attributes to enable
   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date

-error[E0658]: use of unstable library feature 'unstable_test_feature'
+error[E0658]: use of unstable library feature `unstable_test_feature`
  --> $DIR/offset-of-unstable.rs:10:5
   |
 LL | /     offset_of!(
@ -39,7 +39,7 @@ LL | |     );
   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date
   = note: this error originates in the macro `offset_of` (in Nightly builds, run with -Z macro-backtrace for more info)

-error[E0658]: use of unstable library feature 'unstable_test_feature'
+error[E0658]: use of unstable library feature `unstable_test_feature`
  --> $DIR/offset-of-unstable.rs:16:5
   |
 LL |     offset_of!(StableWithUnstableField, unstable);
@ -49,7 +49,7 @@ LL |     offset_of!(StableWithUnstableField, unstable);
   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date
   = note: this error originates in the macro `offset_of` (in Nightly builds, run with -Z macro-backtrace for more info)

-error[E0658]: use of unstable library feature 'unstable_test_feature'
+error[E0658]: use of unstable library feature `unstable_test_feature`
  --> $DIR/offset-of-unstable.rs:18:5
   |
 LL |     offset_of!(StableWithUnstableFieldType, stable.unstable);
@ -59,7 +59,7 @@ LL |     offset_of!(StableWithUnstableFieldType, stable.unstable);
   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date
   = note: this error originates in the macro `offset_of` (in Nightly builds, run with -Z macro-backtrace for more info)

-error[E0658]: use of unstable library feature 'unstable_test_feature'
+error[E0658]: use of unstable library feature `unstable_test_feature`
  --> $DIR/offset-of-unstable.rs:19:5
   |
 LL | /     offset_of!(
@ -73,7 +73,7 @@ LL | |     );
   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date
   = note: this error originates in the macro `offset_of` (in Nightly builds, run with -Z macro-backtrace for more info)

-error[E0658]: use of unstable library feature 'unstable_test_feature'
+error[E0658]: use of unstable library feature `unstable_test_feature`
  --> $DIR/offset-of-unstable.rs:24:5
   |
 LL | /     offset_of!(
--- a/tests/ui/on-unimplemented/suggest_tuple_wrap.rs
+++ b/tests/ui/on-unimplemented/suggest_tuple_wrap.rs
@ -0,0 +1,19 @@
+pub trait Argument {}
+impl Argument for u8 {}
+impl Argument for i8 {}
+impl Argument for String {}
+impl Argument for &str {}
+
+pub trait TupleArgs {}
+impl<A: Argument> TupleArgs for (A,) {}
+impl<A: Argument, B: Argument> TupleArgs for (A, B) {}
+impl<A: Argument, B: Argument, C: Argument> TupleArgs for (A, B, C) {}
+
+fn convert_into_tuple(_x: impl TupleArgs) {}
+
+fn main() {
+    convert_into_tuple(42_u8);
+    //~^ ERROR E0277
+    //~| HELP the following other types implement trait `TupleArgs`
+    //~| HELP use a unary tuple instead
+}
--- a/tests/ui/on-unimplemented/suggest_tuple_wrap.stderr
+++ b/tests/ui/on-unimplemented/suggest_tuple_wrap.stderr
@ -0,0 +1,25 @@
+error[E0277]: the trait bound `u8: TupleArgs` is not satisfied
+  --> $DIR/suggest_tuple_wrap.rs:15:24
+   |
+LL |     convert_into_tuple(42_u8);
+   |     ------------------ ^^^^^ the trait `TupleArgs` is not implemented for `u8`
+   |     |
+   |     required by a bound introduced by this call
+   |
+   = help: the following other types implement trait `TupleArgs`:
+             (A, B)
+             (A, B, C)
+             (A,)
+note: required by a bound in `convert_into_tuple`
+  --> $DIR/suggest_tuple_wrap.rs:12:32
+   |
+LL | fn convert_into_tuple(_x: impl TupleArgs) {}
+   |                                ^^^^^^^^^ required by this bound in `convert_into_tuple`
+help: use a unary tuple instead
+   |
+LL |     convert_into_tuple((42_u8,));
+   |                        +     ++
+
+error: aborting due to 1 previous error
+
+For more information about this error, try `rustc --explain E0277`.
--- a/tests/ui/on-unimplemented/suggest_tuple_wrap_root_obligation.rs
+++ b/tests/ui/on-unimplemented/suggest_tuple_wrap_root_obligation.rs
@ -0,0 +1,26 @@
+struct Tuple;
+
+impl From<(u8,)> for Tuple {
+    fn from(_: (u8,)) -> Self {
+        todo!()
+    }
+}
+impl From<(u8, u8)> for Tuple {
+    fn from(_: (u8, u8)) -> Self {
+        todo!()
+    }
+}
+impl From<(u8, u8, u8)> for Tuple {
+    fn from(_: (u8, u8, u8)) -> Self {
+        todo!()
+    }
+}
+
+fn convert_into_tuple(_x: impl Into<Tuple>) {}
+
+fn main() {
+    convert_into_tuple(42_u8);
+    //~^ ERROR E0277
+    //~| HELP use a unary tuple instead
+    //~| HELP the following other types implement trait `From<T>`
+}
--- a/tests/ui/on-unimplemented/suggest_tuple_wrap_root_obligation.stderr
+++ b/tests/ui/on-unimplemented/suggest_tuple_wrap_root_obligation.stderr
@ -0,0 +1,26 @@
+error[E0277]: the trait bound `Tuple: From<u8>` is not satisfied
+  --> $DIR/suggest_tuple_wrap_root_obligation.rs:22:24
+   |
+LL |     convert_into_tuple(42_u8);
+   |     ------------------ ^^^^^ the trait `From<u8>` is not implemented for `Tuple`
+   |     |
+   |     required by a bound introduced by this call
+   |
+   = help: the following other types implement trait `From<T>`:
+             `Tuple` implements `From<(u8, u8)>`
+             `Tuple` implements `From<(u8, u8, u8)>`
+             `Tuple` implements `From<(u8,)>`
+   = note: required for `u8` to implement `Into<Tuple>`
+note: required by a bound in `convert_into_tuple`
+  --> $DIR/suggest_tuple_wrap_root_obligation.rs:19:32
+   |
+LL | fn convert_into_tuple(_x: impl Into<Tuple>) {}
+   |                                ^^^^^^^^^^^ required by this bound in `convert_into_tuple`
+help: use a unary tuple instead
+   |
+LL |     convert_into_tuple((42_u8,));
+   |                        +     ++
+
+error: aborting due to 1 previous error
+
+For more information about this error, try `rustc --explain E0277`.
--- a/Show More
+++ b/Show More