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    /// Construct a `serde_json::Value` from a JSON literal.
    ///
    /// ```
    /// # use serde_json::json;
    /// #
    /// let value = json!({
    ///     "code": 200,
    ///     "success": true,
    ///     "payload": {
    ///         "features": [
    ///             "serde",
    ///             "json"
    ///         ]
    ///     }
    /// });
    /// ```
    ///
    /// Variables or expressions can be interpolated into the JSON literal. Any type
    /// interpolated into an array element or object value must implement Serde's
    /// `Serialize` trait, while any type interpolated into a object key must
    /// implement `Into<String>`. If the `Serialize` implementation of the
    /// interpolated type decides to fail, or if the interpolated type contains a
    /// map with non-string keys, the `json!` macro will panic.
    ///
    /// ```
    /// # use serde_json::json;
    /// #
    /// let code = 200;
    /// let features = vec!["serde", "json"];
    ///
    /// let value = json!({
    ///     "code": code,
    ///     "success": code == 200,
    ///     "payload": {
    ///         features[0]: features[1]
    ///     }
    /// });
    /// ```
    ///
    /// Trailing commas are allowed inside both arrays and objects.
    ///
    /// ```
    /// # use serde_json::json;
    /// #
    /// let value = json!([
    ///     "notice",
    ///     "the",
    ///     "trailing",
    ///     "comma -->",
    /// ]);
    /// ```
    #[macro_export(local_inner_macros)]
    macro_rules! json {
        // Hide distracting implementation details from the generated rustdoc.
        ($($json:tt)+) => {
            json_internal!($($json)+)
        };
    }

    // Rocket relies on this because they export their own `json!` with a different
    // doc comment than ours, and various Rust bugs prevent them from calling our
    // `json!` from their `json!` so they call `json_internal!` directly. Check with
    // @SergioBenitez before making breaking changes to this macro.
    //
    // Changes are fine as long as `json_internal!` does not call any new helper
    // macros and can still be invoked as `json_internal!($($json)+)`.
    #[macro_export(local_inner_macros)]
    #[doc(hidden)]
    macro_rules! json_internal {
        //////////////////////////////////////////////////////////////////////////
        // TT muncher for parsing the inside of an array [...]. Produces a vec![...]
        // of the elements.
        //
        // Must be invoked as: json_internal!(@array [] $($tt)*)
        //////////////////////////////////////////////////////////////////////////

        // Done with trailing comma.
        (@array [$($elems:expr,)*]) => {
            json_internal_vec![$($elems,)*]
        };

        // Done without trailing comma.
        (@array [$($elems:expr),*]) => {
            json_internal_vec![$($elems),*]
        };

        // Next element is `null`.
        (@array [$($elems:expr,)*] null $($rest:tt)*) => {
            json_internal!(@array [$($elems,)* json_internal!(null)] $($rest)*)
        };

        // Next element is `true`.
        (@array [$($elems:expr,)*] true $($rest:tt)*) => {
            json_internal!(@array [$($elems,)* json_internal!(true)] $($rest)*)
        };

        // Next element is `false`.
        (@array [$($elems:expr,)*] false $($rest:tt)*) => {
            json_internal!(@array [$($elems,)* json_internal!(false)] $($rest)*)
        };

        // Next element is an array.
        (@array [$($elems:expr,)*] [$($array:tt)*] $($rest:tt)*) => {
            json_internal!(@array [$($elems,)* json_internal!([$($array)*])] $($rest)*)
        };

        // Next element is a map.
        (@array [$($elems:expr,)*] {$($map:tt)*} $($rest:tt)*) => {
            json_internal!(@array [$($elems,)* json_internal!({$($map)*})] $($rest)*)
        };

        // Next element is an expression followed by comma.
        (@array [$($elems:expr,)*] $next:expr, $($rest:tt)*) => {
            json_internal!(@array [$($elems,)* json_internal!($next),] $($rest)*)
        };

        // Last element is an expression with no trailing comma.
        (@array [$($elems:expr,)*] $last:expr) => {
            json_internal!(@array [$($elems,)* json_internal!($last)])
        };

        // Comma after the most recent element.
        (@array [$($elems:expr),*] , $($rest:tt)*) => {
            json_internal!(@array [$($elems,)*] $($rest)*)
        };

        // Unexpected token after most recent element.
        (@array [$($elems:expr),*] $unexpected:tt $($rest:tt)*) => {
            json_unexpected!($unexpected)
        };

        //////////////////////////////////////////////////////////////////////////
        // TT muncher for parsing the inside of an object {...}. Each entry is
        // inserted into the given map variable.
        //
        // Must be invoked as: json_internal!(@object $map () ($($tt)*) ($($tt)*))
        //
        // We require two copies of the input tokens so that we can match on one
        // copy and trigger errors on the other copy.
        //////////////////////////////////////////////////////////////////////////

        // Done.
        (@object $object:ident () () ()) => {};

        // Insert the current entry followed by trailing comma.
        (@object $object:ident [$($key:tt)+] ($value:expr) , $($rest:tt)*) => {
            let _ = $object.insert(($($key)+).into(), $value);
            json_internal!(@object $object () ($($rest)*) ($($rest)*));
        };

        // Current entry followed by unexpected token.
        (@object $object:ident [$($key:tt)+] ($value:expr) $unexpected:tt $($rest:tt)*) => {
            json_unexpected!($unexpected);
        };

        // Insert the last entry without trailing comma.
        (@object $object:ident [$($key:tt)+] ($value:expr)) => {
            let _ = $object.insert(($($key)+).into(), $value);
        };

        // Next value is `null`.
        (@object $object:ident ($($key:tt)+) (: null $($rest:tt)*) $copy:tt) => {
            json_internal!(@object $object [$($key)+] (json_internal!(null)) $($rest)*);
        };

        // Next value is `true`.
        (@object $object:ident ($($key:tt)+) (: true $($rest:tt)*) $copy:tt) => {
            json_internal!(@object $object [$($key)+] (json_internal!(true)) $($rest)*);
        };

        // Next value is `false`.
        (@object $object:ident ($($key:tt)+) (: false $($rest:tt)*) $copy:tt) => {
            json_internal!(@object $object [$($key)+] (json_internal!(false)) $($rest)*);
        };

        // Next value is an array.
        (@object $object:ident ($($key:tt)+) (: [$($array:tt)*] $($rest:tt)*) $copy:tt) => {
            json_internal!(@object $object [$($key)+] (json_internal!([$($array)*])) $($rest)*);
        };

        // Next value is a map.
        (@object $object:ident ($($key:tt)+) (: {$($map:tt)*} $($rest:tt)*) $copy:tt) => {
            json_internal!(@object $object [$($key)+] (json_internal!({$($map)*})) $($rest)*);
        };

        // Next value is an expression followed by comma.
        (@object $object:ident ($($key:tt)+) (: $value:expr , $($rest:tt)*) $copy:tt) => {
            json_internal!(@object $object [$($key)+] (json_internal!($value)) , $($rest)*);
        };

        // Last value is an expression with no trailing comma.
        (@object $object:ident ($($key:tt)+) (: $value:expr) $copy:tt) => {
            json_internal!(@object $object [$($key)+] (json_internal!($value)));
        };

        // Missing value for last entry. Trigger a reasonable error message.
        (@object $object:ident ($($key:tt)+) (:) $copy:tt) => {
            // "unexpected end of macro invocation"
            json_internal!();
        };

        // Missing colon and value for last entry. Trigger a reasonable error
        // message.
        (@object $object:ident ($($key:tt)+) () $copy:tt) => {
            // "unexpected end of macro invocation"
            json_internal!();
        };

        // Misplaced colon. Trigger a reasonable error message.
        (@object $object:ident () (: $($rest:tt)*) ($colon:tt $($copy:tt)*)) => {
            // Takes no arguments so "no rules expected the token `:`".
            json_unexpected!($colon);
        };

        // Found a comma inside a key. Trigger a reasonable error message.
        (@object $object:ident ($($key:tt)*) (, $($rest:tt)*) ($comma:tt $($copy:tt)*)) => {
            // Takes no arguments so "no rules expected the token `,`".
            json_unexpected!($comma);
        };

        // Key is fully parenthesized. This avoids clippy double_parens false
        // positives because the parenthesization may be necessary here.
        (@object $object:ident () (($key:expr) : $($rest:tt)*) $copy:tt) => {
            json_internal!(@object $object ($key) (: $($rest)*) (: $($rest)*));
        };

        // Refuse to absorb colon token into key expression.
        (@object $object:ident ($($key:tt)*) (: $($unexpected:tt)+) $copy:tt) => {
            json_expect_expr_comma!($($unexpected)+);
        };

        // Munch a token into the current key.
        (@object $object:ident ($($key:tt)*) ($tt:tt $($rest:tt)*) $copy:tt) => {
            json_internal!(@object $object ($($key)* $tt) ($($rest)*) ($($rest)*));
        };

        //////////////////////////////////////////////////////////////////////////
        // The main implementation.
        //
        // Must be invoked as: json_internal!($($json)+)
        //////////////////////////////////////////////////////////////////////////

        (null) => {
            $crate::Value::Null
        };

        (true) => {
            $crate::Value::Bool(true)
        };

        (false) => {
            $crate::Value::Bool(false)
        };

        ([]) => {
            $crate::Value::Array(json_internal_vec![])
        };

        ([ $($tt:tt)+ ]) => {
            $crate::Value::Array(json_internal!(@array [] $($tt)+))
        };

        ({}) => {
            $crate::Value::Object($crate::Map::new())
        };

        ({ $($tt:tt)+ }) => {
            $crate::Value::Object({
                let mut object = $crate::Map::new();
                json_internal!(@object object () ($($tt)+) ($($tt)+));
                object
            })
        };

        // Any Serialize type: numbers, strings, struct literals, variables etc.
        // Must be below every other rule.
        ($other:expr) => {
            $crate::to_value(&$other).unwrap()
        };
    }

    // The json_internal macro above cannot invoke vec directly because it uses
    // local_inner_macros. A vec invocation there would resolve to $crate::vec.
    // Instead invoke vec here outside of local_inner_macros.
    #[macro_export]
    #[doc(hidden)]
    macro_rules! json_internal_vec {
        ($($content:tt)*) => {
            vec![$($content)*]
        };
    }

    #[macro_export]
    #[doc(hidden)]
    macro_rules! json_unexpected {
        () => {};
    }

    #[macro_export]
    #[doc(hidden)]
    macro_rules! json_expect_expr_comma {
        ($e:expr , $($tt:tt)*) => {};
    }