Merging upstream version 1.66.0+dfsg1.

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

4 files changed, 778 insertions, 0 deletions

diff --git a/vendor/tracing-subscriber-0.3.3/src/field/debug.rs b/vendor/tracing-subscriber-0.3.3/src/field/debug.rs
new file mode 100644
index 000000000..cc67d29fe
--- /dev/null
+++ b/vendor/tracing-subscriber-0.3.3/src/field/debug.rs
@@ -0,0 +1,111 @@
+//! `MakeVisitor` wrappers for working with `fmt::Debug` fields.
+use super::{MakeVisitor, VisitFmt, VisitOutput};
+use tracing_core::field::{Field, Visit};
+
+use core::fmt;
+
+/// A visitor wrapper that ensures any `fmt::Debug` fields are formatted using
+/// the alternate (`:#`) formatter.
+#[derive(Debug, Clone)]
+pub struct Alt<V>(V);
+
+// TODO(eliza): When `error` as a primitive type is stable, add a
+// `DisplayErrors` wrapper...
+
+// === impl Alt ===
+//
+impl<V> Alt<V> {
+    /// Wraps the provided visitor so that any `fmt::Debug` fields are formatted
+    /// using the alternative (`:#`) formatter.
+    pub fn new(inner: V) -> Self {
+        Alt(inner)
+    }
+}
+
+impl<T, V> MakeVisitor<T> for Alt<V>
+where
+    V: MakeVisitor<T>,
+{
+    type Visitor = Alt<V::Visitor>;
+
+    #[inline]
+    fn make_visitor(&self, target: T) -> Self::Visitor {
+        Alt(self.0.make_visitor(target))
+    }
+}
+
+impl<V> Visit for Alt<V>
+where
+    V: Visit,
+{
+    #[inline]
+    fn record_f64(&mut self, field: &Field, value: f64) {
+        self.0.record_f64(field, value)
+    }
+
+    #[inline]
+    fn record_i64(&mut self, field: &Field, value: i64) {
+        self.0.record_i64(field, value)
+    }
+
+    #[inline]
+    fn record_u64(&mut self, field: &Field, value: u64) {
+        self.0.record_u64(field, value)
+    }
+
+    #[inline]
+    fn record_bool(&mut self, field: &Field, value: bool) {
+        self.0.record_bool(field, value)
+    }
+
+    /// Visit a string value.
+    fn record_str(&mut self, field: &Field, value: &str) {
+        self.0.record_str(field, value)
+    }
+
+    // TODO(eliza): add RecordError when stable
+    // fn record_error(&mut self, field: &Field, value: &(dyn std::error::Error + 'static)) {
+    //     self.record_debug(field, &format_args!("{}", value))
+    // }
+
+    #[inline]
+    fn record_debug(&mut self, field: &Field, value: &dyn fmt::Debug) {
+        self.0.record_debug(field, &format_args!("{:#?}", value))
+    }
+}
+
+impl<V, O> VisitOutput<O> for Alt<V>
+where
+    V: VisitOutput<O>,
+{
+    #[inline]
+    fn finish(self) -> O {
+        self.0.finish()
+    }
+}
+
+feature! {
+    #![feature = "std"]
+    use super::VisitWrite;
+    use std::io;
+
+    impl<V> VisitWrite for Alt<V>
+    where
+        V: VisitWrite,
+    {
+        #[inline]
+        fn writer(&mut self) -> &mut dyn io::Write {
+            self.0.writer()
+        }
+    }
+}
+
+impl<V> VisitFmt for Alt<V>
+where
+    V: VisitFmt,
+{
+    #[inline]
+    fn writer(&mut self) -> &mut dyn fmt::Write {
+        self.0.writer()
+    }
+}
diff --git a/vendor/tracing-subscriber-0.3.3/src/field/delimited.rs b/vendor/tracing-subscriber-0.3.3/src/field/delimited.rs
new file mode 100644
index 000000000..8c78c4b20
--- /dev/null
+++ b/vendor/tracing-subscriber-0.3.3/src/field/delimited.rs
@@ -0,0 +1,184 @@
+//! A `MakeVisitor` wrapper that separates formatted fields with a delimiter.
+use super::{MakeVisitor, VisitFmt, VisitOutput};
+
+use core::fmt;
+use tracing_core::field::{Field, Visit};
+
+/// A `MakeVisitor` wrapper that wraps a visitor that writes formatted output so
+/// that a delimiter is inserted between writing formatted field values.
+#[derive(Debug, Clone)]
+pub struct Delimited<D, V> {
+    delimiter: D,
+    inner: V,
+}
+
+/// A visitor wrapper that inserts a delimiter after the wrapped visitor formats
+/// a field value.
+#[derive(Debug)]
+pub struct VisitDelimited<D, V> {
+    delimiter: D,
+    seen: bool,
+    inner: V,
+    err: fmt::Result,
+}
+
+// === impl Delimited ===
+
+impl<D, V, T> MakeVisitor<T> for Delimited<D, V>
+where
+    D: AsRef<str> + Clone,
+    V: MakeVisitor<T>,
+    V::Visitor: VisitFmt,
+{
+    type Visitor = VisitDelimited<D, V::Visitor>;
+    fn make_visitor(&self, target: T) -> Self::Visitor {
+        let inner = self.inner.make_visitor(target);
+        VisitDelimited::new(self.delimiter.clone(), inner)
+    }
+}
+
+impl<D, V> Delimited<D, V> {
+    /// Returns a new [`MakeVisitor`] implementation that wraps `inner` so that
+    /// it will format each visited field separated by the provided `delimiter`.
+    ///
+    /// [`MakeVisitor`]: ../trait.MakeVisitor.html
+    pub fn new(delimiter: D, inner: V) -> Self {
+        Self { delimiter, inner }
+    }
+}
+
+// === impl VisitDelimited ===
+
+impl<D, V> VisitDelimited<D, V> {
+    /// Returns a new [`Visit`] implementation that wraps `inner` so that
+    /// each formatted field is separated by the provided `delimiter`.
+    ///
+    /// [`Visit`]: https://docs.rs/tracing-core/0.1.6/tracing_core/field/trait.Visit.html
+    pub fn new(delimiter: D, inner: V) -> Self {
+        Self {
+            delimiter,
+            inner,
+            seen: false,
+            err: Ok(()),
+        }
+    }
+
+    fn delimit(&mut self)
+    where
+        V: VisitFmt,
+        D: AsRef<str>,
+    {
+        if self.err.is_err() {
+            return;
+        }
+
+        if self.seen {
+            self.err = self.inner.writer().write_str(self.delimiter.as_ref());
+        }
+
+        self.seen = true;
+    }
+}
+
+impl<D, V> Visit for VisitDelimited<D, V>
+where
+    V: VisitFmt,
+    D: AsRef<str>,
+{
+    fn record_i64(&mut self, field: &Field, value: i64) {
+        self.delimit();
+        self.inner.record_i64(field, value);
+    }
+
+    fn record_u64(&mut self, field: &Field, value: u64) {
+        self.delimit();
+        self.inner.record_u64(field, value);
+    }
+
+    fn record_bool(&mut self, field: &Field, value: bool) {
+        self.delimit();
+        self.inner.record_bool(field, value);
+    }
+
+    fn record_str(&mut self, field: &Field, value: &str) {
+        self.delimit();
+        self.inner.record_str(field, value);
+    }
+
+    fn record_debug(&mut self, field: &Field, value: &dyn fmt::Debug) {
+        self.delimit();
+        self.inner.record_debug(field, value);
+    }
+}
+
+impl<D, V> VisitOutput<fmt::Result> for VisitDelimited<D, V>
+where
+    V: VisitFmt,
+    D: AsRef<str>,
+{
+    fn finish(self) -> fmt::Result {
+        self.err?;
+        self.inner.finish()
+    }
+}
+
+impl<D, V> VisitFmt for VisitDelimited<D, V>
+where
+    V: VisitFmt,
+    D: AsRef<str>,
+{
+    fn writer(&mut self) -> &mut dyn fmt::Write {
+        self.inner.writer()
+    }
+}
+
+#[cfg(test)]
+#[cfg(all(test, feature = "alloc"))]
+mod test {
+    use super::*;
+    use crate::field::test_util::*;
+
+    #[test]
+    fn delimited_visitor() {
+        let mut s = String::new();
+        let visitor = DebugVisitor::new(&mut s);
+        let mut visitor = VisitDelimited::new(", ", visitor);
+
+        TestAttrs1::with(|attrs| attrs.record(&mut visitor));
+        visitor.finish().unwrap();
+
+        assert_eq!(
+            s.as_str(),
+            "question=\"life, the universe, and everything\", tricky=true, can_you_do_it=true"
+        );
+    }
+
+    #[test]
+    fn delimited_new_visitor() {
+        let make = Delimited::new("; ", MakeDebug);
+
+        TestAttrs1::with(|attrs| {
+            let mut s = String::new();
+            {
+                let mut v = make.make_visitor(&mut s);
+                attrs.record(&mut v);
+            }
+            assert_eq!(
+                s.as_str(),
+                "question=\"life, the universe, and everything\"; tricky=true; can_you_do_it=true"
+            );
+        });
+
+        TestAttrs2::with(|attrs| {
+            let mut s = String::new();
+            {
+                let mut v = make.make_visitor(&mut s);
+                attrs.record(&mut v);
+            }
+            assert_eq!(
+                s.as_str(),
+                "question=None; question.answer=42; tricky=true; can_you_do_it=false"
+            );
+        });
+    }
+}
diff --git a/vendor/tracing-subscriber-0.3.3/src/field/display.rs b/vendor/tracing-subscriber-0.3.3/src/field/display.rs
new file mode 100644
index 000000000..e0bbc55ed
--- /dev/null
+++ b/vendor/tracing-subscriber-0.3.3/src/field/display.rs
@@ -0,0 +1,117 @@
+//! `MakeVisitor` wrappers for working with `fmt::Display` fields.
+use super::{MakeVisitor, VisitFmt, VisitOutput};
+use tracing_core::field::{Field, Visit};
+
+use core::fmt;
+
+/// A visitor wrapper that ensures any strings named "message" are formatted
+/// using `fmt::Display`
+#[derive(Debug, Clone)]
+pub struct Messages<V>(V);
+
+// TODO(eliza): When `error` as a primitive type is stable, add a
+// `DisplayErrors` wrapper...
+
+// === impl Messages ===
+//
+impl<V> Messages<V> {
+    /// Returns a new [`MakeVisitor`] implementation that will wrap `inner` so
+    /// that any strings named `message` are formatted using `fmt::Display`.
+    ///
+    /// [`MakeVisitor`]: ../trait.MakeVisitor.html
+    pub fn new(inner: V) -> Self {
+        Messages(inner)
+    }
+}
+
+impl<T, V> MakeVisitor<T> for Messages<V>
+where
+    V: MakeVisitor<T>,
+{
+    type Visitor = Messages<V::Visitor>;
+
+    #[inline]
+    fn make_visitor(&self, target: T) -> Self::Visitor {
+        Messages(self.0.make_visitor(target))
+    }
+}
+
+impl<V> Visit for Messages<V>
+where
+    V: Visit,
+{
+    #[inline]
+    fn record_f64(&mut self, field: &Field, value: f64) {
+        self.0.record_f64(field, value)
+    }
+
+    #[inline]
+    fn record_i64(&mut self, field: &Field, value: i64) {
+        self.0.record_i64(field, value)
+    }
+
+    #[inline]
+    fn record_u64(&mut self, field: &Field, value: u64) {
+        self.0.record_u64(field, value)
+    }
+
+    #[inline]
+    fn record_bool(&mut self, field: &Field, value: bool) {
+        self.0.record_bool(field, value)
+    }
+
+    /// Visit a string value.
+    fn record_str(&mut self, field: &Field, value: &str) {
+        if field.name() == "message" {
+            self.0.record_debug(field, &format_args!("{}", value))
+        } else {
+            self.0.record_str(field, value)
+        }
+    }
+
+    // TODO(eliza): add RecordError when stable
+    // fn record_error(&mut self, field: &Field, value: &(dyn std::error::Error + 'static)) {
+    //     self.record_debug(field, &format_args!("{}", value))
+    // }
+
+    #[inline]
+    fn record_debug(&mut self, field: &Field, value: &dyn fmt::Debug) {
+        self.0.record_debug(field, value)
+    }
+}
+
+impl<V, O> VisitOutput<O> for Messages<V>
+where
+    V: VisitOutput<O>,
+{
+    #[inline]
+    fn finish(self) -> O {
+        self.0.finish()
+    }
+}
+
+feature! {
+    #![feature = "std"]
+    use super::VisitWrite;
+    use std::io;
+
+    impl<V> VisitWrite for Messages<V>
+    where
+        V: VisitWrite,
+    {
+        #[inline]
+        fn writer(&mut self) -> &mut dyn io::Write {
+            self.0.writer()
+        }
+    }
+}
+
+impl<V> VisitFmt for Messages<V>
+where
+    V: VisitFmt,
+{
+    #[inline]
+    fn writer(&mut self) -> &mut dyn fmt::Write {
+        self.0.writer()
+    }
+}
diff --git a/vendor/tracing-subscriber-0.3.3/src/field/mod.rs b/vendor/tracing-subscriber-0.3.3/src/field/mod.rs
new file mode 100644
index 000000000..f7d03f2cc
--- /dev/null
+++ b/vendor/tracing-subscriber-0.3.3/src/field/mod.rs
@@ -0,0 +1,366 @@
+//! Utilities for working with [fields] and [field visitors].
+//!
+//! [fields]: tracing_core::field
+//! [field visitors]: tracing_core::field::Visit
+use core::{fmt, marker::PhantomData};
+pub use tracing_core::field::Visit;
+use tracing_core::{
+    span::{Attributes, Record},
+    Event,
+};
+pub mod debug;
+pub mod delimited;
+pub mod display;
+
+/// Creates new [visitors].
+///
+/// A type implementing `MakeVisitor` represents a composable factory for types
+/// implementing the [`Visit` trait][visitors]. The `MakeVisitor` trait defines
+/// a single function, `make_visitor`, which takes in a `T`-typed `target` and
+/// returns a type implementing `Visit` configured for that target. A target may
+/// be a string, output stream, or data structure that the visitor will record
+/// data to, configuration variables that determine the visitor's behavior, or
+/// `()` when no input is required to produce a visitor.
+///
+/// [visitors]: https://docs.rs/tracing-core/latest/tracing_core/field/trait.Visit.html
+pub trait MakeVisitor<T> {
+    /// The visitor type produced by this `MakeVisitor`.
+    type Visitor: Visit;
+
+    /// Make a new visitor for the provided `target`.
+    fn make_visitor(&self, target: T) -> Self::Visitor;
+}
+
+/// A [visitor] that produces output once it has visited a set of fields.
+///
+/// [visitor]: https://docs.rs/tracing-core/latest/tracing_core/field/trait.Visit.html
+pub trait VisitOutput<Out>: Visit {
+    /// Completes the visitor, returning any output.
+    ///
+    /// This is called once a full set of fields has been visited.
+    fn finish(self) -> Out;
+
+    /// Visit a set of fields, and return the output of finishing the visitor
+    /// once the fields have been visited.
+    fn visit<R>(mut self, fields: &R) -> Out
+    where
+        R: RecordFields,
+        Self: Sized,
+    {
+        fields.record(&mut self);
+        self.finish()
+    }
+}
+
+/// Extension trait implemented by types which can be recorded by a [visitor].
+///
+/// This allows writing code that is generic over `tracing_core`'s
+/// [`span::Attributes`][attr], [`span::Record`][rec], and [`Event`][event]
+/// types. These types all provide inherent `record` methods that allow a
+/// visitor to record their fields, but there is no common trait representing this.
+///
+/// With `RecordFields`, we can write code like this:
+/// ```
+/// use tracing_core::field::Visit;
+/// # use tracing_core::field::Field;
+/// use tracing_subscriber::field::RecordFields;
+///
+/// struct MyVisitor {
+///     // ...
+/// }
+/// # impl MyVisitor { fn new() -> Self { Self{} } }
+/// impl Visit for MyVisitor {
+///     // ...
+/// # fn record_debug(&mut self, _: &Field, _: &dyn std::fmt::Debug) {}
+/// }
+///
+/// fn record_with_my_visitor<R>(r: R)
+/// where
+///     R: RecordFields,
+/// {
+///     let mut visitor = MyVisitor::new();
+///     r.record(&mut visitor);
+/// }
+/// ```
+/// [visitor]: https://docs.rs/tracing-core/latest/tracing_core/field/trait.Visit.html
+/// [attr]: https://docs.rs/tracing-core/latest/tracing_core/span/struct.Attributes.html
+/// [rec]: https://docs.rs/tracing-core/latest/tracing_core/span/struct.Record.html
+/// [event]: https://docs.rs/tracing-core/latest/tracing_core/event/struct.Event.html
+pub trait RecordFields: crate::sealed::Sealed<RecordFieldsMarker> {
+    /// Record all the fields in `self` with the provided `visitor`.
+    fn record(&self, visitor: &mut dyn Visit);
+}
+
+/// Extension trait implemented for all `MakeVisitor` implementations that
+/// produce a visitor implementing `VisitOutput`.
+pub trait MakeOutput<T, Out>
+where
+    Self: MakeVisitor<T> + crate::sealed::Sealed<(T, Out)>,
+    Self::Visitor: VisitOutput<Out>,
+{
+    /// Visits all fields in `fields` with a new visitor constructed from
+    /// `target`.
+    fn visit_with<F>(&self, target: T, fields: &F) -> Out
+    where
+        F: RecordFields,
+    {
+        self.make_visitor(target).visit(fields)
+    }
+}
+
+feature! {
+    #![feature = "std"]
+    use std::io;
+
+    /// Extension trait implemented by visitors to indicate that they write to an
+    /// `io::Write` instance, and allow access to that writer.
+    pub trait VisitWrite: VisitOutput<Result<(), io::Error>> {
+        /// Returns the writer that this visitor writes to.
+        fn writer(&mut self) -> &mut dyn io::Write;
+    }
+}
+
+/// Extension trait implemented by visitors to indicate that they write to a
+/// `fmt::Write` instance, and allow access to that writer.
+pub trait VisitFmt: VisitOutput<fmt::Result> {
+    /// Returns the formatter that this visitor writes to.
+    fn writer(&mut self) -> &mut dyn fmt::Write;
+}
+
+/// Extension trait providing `MakeVisitor` combinators.
+pub trait MakeExt<T>
+where
+    Self: MakeVisitor<T> + Sized,
+    Self: crate::sealed::Sealed<MakeExtMarker<T>>,
+{
+    /// Wraps `self` so that any `fmt::Debug` fields are recorded using the
+    /// alternate formatter (`{:#?}`).
+    fn debug_alt(self) -> debug::Alt<Self> {
+        debug::Alt::new(self)
+    }
+
+    /// Wraps `self` so that any string fields named "message" are recorded
+    /// using `fmt::Display`.
+    fn display_messages(self) -> display::Messages<Self> {
+        display::Messages::new(self)
+    }
+
+    /// Wraps `self` so that when fields are formatted to a writer, they are
+    /// separated by the provided `delimiter`.
+    fn delimited<D>(self, delimiter: D) -> delimited::Delimited<D, Self>
+    where
+        D: AsRef<str> + Clone,
+        Self::Visitor: VisitFmt,
+    {
+        delimited::Delimited::new(delimiter, self)
+    }
+}
+
+// === impl RecordFields ===
+
+impl<'a> crate::sealed::Sealed<RecordFieldsMarker> for Event<'a> {}
+impl<'a> RecordFields for Event<'a> {
+    fn record(&self, visitor: &mut dyn Visit) {
+        Event::record(self, visitor)
+    }
+}
+
+impl<'a> crate::sealed::Sealed<RecordFieldsMarker> for Attributes<'a> {}
+impl<'a> RecordFields for Attributes<'a> {
+    fn record(&self, visitor: &mut dyn Visit) {
+        Attributes::record(self, visitor)
+    }
+}
+
+impl<'a> crate::sealed::Sealed<RecordFieldsMarker> for Record<'a> {}
+impl<'a> RecordFields for Record<'a> {
+    fn record(&self, visitor: &mut dyn Visit) {
+        Record::record(self, visitor)
+    }
+}
+
+impl<'a, F> crate::sealed::Sealed<RecordFieldsMarker> for &'a F where F: RecordFields {}
+impl<'a, F> RecordFields for &'a F
+where
+    F: RecordFields,
+{
+    fn record(&self, visitor: &mut dyn Visit) {
+        F::record(*self, visitor)
+    }
+}
+
+// === blanket impls ===
+
+impl<T, V, F> MakeVisitor<T> for F
+where
+    F: Fn(T) -> V,
+    V: Visit,
+{
+    type Visitor = V;
+    fn make_visitor(&self, target: T) -> Self::Visitor {
+        (self)(target)
+    }
+}
+
+impl<T, Out, M> crate::sealed::Sealed<(T, Out)> for M
+where
+    M: MakeVisitor<T>,
+    M::Visitor: VisitOutput<Out>,
+{
+}
+
+impl<T, Out, M> MakeOutput<T, Out> for M
+where
+    M: MakeVisitor<T>,
+    M::Visitor: VisitOutput<Out>,
+{
+}
+
+impl<T, M> crate::sealed::Sealed<MakeExtMarker<T>> for M where M: MakeVisitor<T> + Sized {}
+
+impl<T, M> MakeExt<T> for M
+where
+    M: MakeVisitor<T> + Sized,
+    M: crate::sealed::Sealed<MakeExtMarker<T>>,
+{
+}
+
+#[derive(Debug)]
+#[doc(hidden)]
+pub struct MakeExtMarker<T> {
+    _p: PhantomData<T>,
+}
+
+#[derive(Debug)]
+#[doc(hidden)]
+pub struct RecordFieldsMarker {
+    _p: (),
+}
+
+#[cfg(all(test, feature = "alloc"))]
+#[macro_use]
+pub(in crate::field) mod test_util {
+    use super::*;
+    pub(in crate::field) use alloc::string::String;
+    use tracing_core::{
+        callsite::Callsite,
+        field::{Field, Value},
+        metadata::{Kind, Level, Metadata},
+    };
+
+    pub(crate) struct TestAttrs1;
+    pub(crate) struct TestAttrs2;
+
+    impl TestAttrs1 {
+        pub(crate) fn with<T>(f: impl FnOnce(Attributes<'_>) -> T) -> T {
+            let fieldset = TEST_META_1.fields();
+            let values = &[
+                (
+                    &fieldset.field("question").unwrap(),
+                    Some(&"life, the universe, and everything" as &dyn Value),
+                ),
+                (&fieldset.field("question.answer").unwrap(), None),
+                (
+                    &fieldset.field("tricky").unwrap(),
+                    Some(&true as &dyn Value),
+                ),
+                (
+                    &fieldset.field("can_you_do_it").unwrap(),
+                    Some(&true as &dyn Value),
+                ),
+            ];
+            let valueset = fieldset.value_set(values);
+            let attrs = tracing_core::span::Attributes::new(&TEST_META_1, &valueset);
+            f(attrs)
+        }
+    }
+
+    impl TestAttrs2 {
+        pub(crate) fn with<T>(f: impl FnOnce(Attributes<'_>) -> T) -> T {
+            let fieldset = TEST_META_1.fields();
+            let none = tracing_core::field::debug(&Option::<&str>::None);
+            let values = &[
+                (
+                    &fieldset.field("question").unwrap(),
+                    Some(&none as &dyn Value),
+                ),
+                (
+                    &fieldset.field("question.answer").unwrap(),
+                    Some(&42 as &dyn Value),
+                ),
+                (
+                    &fieldset.field("tricky").unwrap(),
+                    Some(&true as &dyn Value),
+                ),
+                (
+                    &fieldset.field("can_you_do_it").unwrap(),
+                    Some(&false as &dyn Value),
+                ),
+            ];
+            let valueset = fieldset.value_set(values);
+            let attrs = tracing_core::span::Attributes::new(&TEST_META_1, &valueset);
+            f(attrs)
+        }
+    }
+
+    struct TestCallsite1;
+    static TEST_CALLSITE_1: &'static dyn Callsite = &TestCallsite1;
+    static TEST_META_1: Metadata<'static> = tracing_core::metadata! {
+        name: "field_test1",
+        target: module_path!(),
+        level: Level::INFO,
+        fields: &["question", "question.answer", "tricky", "can_you_do_it"],
+        callsite: TEST_CALLSITE_1,
+        kind: Kind::SPAN,
+    };
+
+    impl Callsite for TestCallsite1 {
+        fn set_interest(&self, _: tracing_core::subscriber::Interest) {
+            unimplemented!()
+        }
+
+        fn metadata(&self) -> &Metadata<'_> {
+            &TEST_META_1
+        }
+    }
+
+    pub(crate) struct MakeDebug;
+    pub(crate) struct DebugVisitor<'a> {
+        writer: &'a mut dyn fmt::Write,
+        err: fmt::Result,
+    }
+
+    impl<'a> DebugVisitor<'a> {
+        pub(crate) fn new(writer: &'a mut dyn fmt::Write) -> Self {
+            Self {
+                writer,
+                err: Ok(()),
+            }
+        }
+    }
+
+    impl<'a> Visit for DebugVisitor<'a> {
+        fn record_debug(&mut self, field: &Field, value: &dyn fmt::Debug) {
+            write!(&mut self.writer, "{}={:?}", field, value).unwrap();
+        }
+    }
+
+    impl<'a> VisitOutput<fmt::Result> for DebugVisitor<'a> {
+        fn finish(self) -> fmt::Result {
+            self.err
+        }
+    }
+
+    impl<'a> VisitFmt for DebugVisitor<'a> {
+        fn writer(&mut self) -> &mut dyn fmt::Write {
+            self.writer
+        }
+    }
+
+    impl<'a> MakeVisitor<&'a mut dyn fmt::Write> for MakeDebug {
+        type Visitor = DebugVisitor<'a>;
+        fn make_visitor(&self, w: &'a mut dyn fmt::Write) -> DebugVisitor<'a> {
+            DebugVisitor::new(w)
+        }
+    }
+}