rust: quote: import crate

This is a subset of the Rust `quote` crate, version 1.0.40 (released
2025-03-12), licensed under "Apache-2.0 OR MIT", from:

    https://github.com/dtolnay/quote/raw/1.0.40/src

The files are copied as-is, with no modifications whatsoever (not even
adding the SPDX identifiers).

For copyright details, please see:

    https://github.com/dtolnay/quote/blob/1.0.40/README.md#license
    https://github.com/dtolnay/quote/blob/1.0.40/LICENSE-APACHE
    https://github.com/dtolnay/quote/blob/1.0.40/LICENSE-MIT

The next patch modifies these files as needed for use within the
kernel. This patch split allows reviewers to double-check the import
and to clearly see the differences introduced.

The following script may be used to verify the contents:

    for path in $(cd rust/quote/ && find . -type f -name '*.rs'); do
        curl --silent --show-error --location \
            https://github.com/dtolnay/quote/raw/1.0.40/src/$path \
            | diff --unified rust/quote/$path - && echo $path: OK
    done

Reviewed-by: Gary Guo <gary@garyguo.net>
Tested-by: Gary Guo <gary@garyguo.net>
Tested-by: Jesung Yang <y.j3ms.n@gmail.com>
Link: https://patch.msgid.link/20251124151837.2184382-12-ojeda@kernel.org
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>

1 files changed, 168 insertions, 0 deletions

diff --git a/rust/quote/format.rs b/rust/quote/format.rs
new file mode 100644
index 000000000000..ec0bbf38ba37
--- /dev/null
+++ b/rust/quote/format.rs
@@ -0,0 +1,168 @@
+/// Formatting macro for constructing `Ident`s.
+///
+/// <br>
+///
+/// # Syntax
+///
+/// Syntax is copied from the [`format!`] macro, supporting both positional and
+/// named arguments.
+///
+/// Only a limited set of formatting traits are supported. The current mapping
+/// of format types to traits is:
+///
+/// * `{}` ⇒ [`IdentFragment`]
+/// * `{:o}` ⇒ [`Octal`](std::fmt::Octal)
+/// * `{:x}` ⇒ [`LowerHex`](std::fmt::LowerHex)
+/// * `{:X}` ⇒ [`UpperHex`](std::fmt::UpperHex)
+/// * `{:b}` ⇒ [`Binary`](std::fmt::Binary)
+///
+/// See [`std::fmt`] for more information.
+///
+/// <br>
+///
+/// # IdentFragment
+///
+/// Unlike `format!`, this macro uses the [`IdentFragment`] formatting trait by
+/// default. This trait is like `Display`, with a few differences:
+///
+/// * `IdentFragment` is only implemented for a limited set of types, such as
+///   unsigned integers and strings.
+/// * [`Ident`] arguments will have their `r#` prefixes stripped, if present.
+///
+/// [`IdentFragment`]: crate::IdentFragment
+/// [`Ident`]: proc_macro2::Ident
+///
+/// <br>
+///
+/// # Hygiene
+///
+/// The [`Span`] of the first `Ident` argument is used as the span of the final
+/// identifier, falling back to [`Span::call_site`] when no identifiers are
+/// provided.
+///
+/// ```
+/// # use quote::format_ident;
+/// # let ident = format_ident!("Ident");
+/// // If `ident` is an Ident, the span of `my_ident` will be inherited from it.
+/// let my_ident = format_ident!("My{}{}", ident, "IsCool");
+/// assert_eq!(my_ident, "MyIdentIsCool");
+/// ```
+///
+/// Alternatively, the span can be overridden by passing the `span` named
+/// argument.
+///
+/// ```
+/// # use quote::format_ident;
+/// # const IGNORE_TOKENS: &'static str = stringify! {
+/// let my_span = /* ... */;
+/// # };
+/// # let my_span = proc_macro2::Span::call_site();
+/// format_ident!("MyIdent", span = my_span);
+/// ```
+///
+/// [`Span`]: proc_macro2::Span
+/// [`Span::call_site`]: proc_macro2::Span::call_site
+///
+/// <p><br></p>
+///
+/// # Panics
+///
+/// This method will panic if the resulting formatted string is not a valid
+/// identifier.
+///
+/// <br>
+///
+/// # Examples
+///
+/// Composing raw and non-raw identifiers:
+/// ```
+/// # use quote::format_ident;
+/// let my_ident = format_ident!("My{}", "Ident");
+/// assert_eq!(my_ident, "MyIdent");
+///
+/// let raw = format_ident!("r#Raw");
+/// assert_eq!(raw, "r#Raw");
+///
+/// let my_ident_raw = format_ident!("{}Is{}", my_ident, raw);
+/// assert_eq!(my_ident_raw, "MyIdentIsRaw");
+/// ```
+///
+/// Integer formatting options:
+/// ```
+/// # use quote::format_ident;
+/// let num: u32 = 10;
+///
+/// let decimal = format_ident!("Id_{}", num);
+/// assert_eq!(decimal, "Id_10");
+///
+/// let octal = format_ident!("Id_{:o}", num);
+/// assert_eq!(octal, "Id_12");
+///
+/// let binary = format_ident!("Id_{:b}", num);
+/// assert_eq!(binary, "Id_1010");
+///
+/// let lower_hex = format_ident!("Id_{:x}", num);
+/// assert_eq!(lower_hex, "Id_a");
+///
+/// let upper_hex = format_ident!("Id_{:X}", num);
+/// assert_eq!(upper_hex, "Id_A");
+/// ```
+#[macro_export]
+macro_rules! format_ident {
+    ($fmt:expr) => {
+        $crate::format_ident_impl!([
+            $crate::__private::Option::None,
+            $fmt
+        ])
+    };
+
+    ($fmt:expr, $($rest:tt)*) => {
+        $crate::format_ident_impl!([
+            $crate::__private::Option::None,
+            $fmt
+        ] $($rest)*)
+    };
+}
+
+#[macro_export]
+#[doc(hidden)]
+macro_rules! format_ident_impl {
+    // Final state
+    ([$span:expr, $($fmt:tt)*]) => {
+        $crate::__private::mk_ident(
+            &$crate::__private::format!($($fmt)*),
+            $span,
+        )
+    };
+
+    // Span argument
+    ([$old:expr, $($fmt:tt)*] span = $span:expr) => {
+        $crate::format_ident_impl!([$old, $($fmt)*] span = $span,)
+    };
+    ([$old:expr, $($fmt:tt)*] span = $span:expr, $($rest:tt)*) => {
+        $crate::format_ident_impl!([
+            $crate::__private::Option::Some::<$crate::__private::Span>($span),
+            $($fmt)*
+        ] $($rest)*)
+    };
+
+    // Named argument
+    ([$span:expr, $($fmt:tt)*] $name:ident = $arg:expr) => {
+        $crate::format_ident_impl!([$span, $($fmt)*] $name = $arg,)
+    };
+    ([$span:expr, $($fmt:tt)*] $name:ident = $arg:expr, $($rest:tt)*) => {
+        match $crate::__private::IdentFragmentAdapter(&$arg) {
+            arg => $crate::format_ident_impl!([$span.or(arg.span()), $($fmt)*, $name = arg] $($rest)*),
+        }
+    };
+
+    // Positional argument
+    ([$span:expr, $($fmt:tt)*] $arg:expr) => {
+        $crate::format_ident_impl!([$span, $($fmt)*] $arg,)
+    };
+    ([$span:expr, $($fmt:tt)*] $arg:expr, $($rest:tt)*) => {
+        match $crate::__private::IdentFragmentAdapter(&$arg) {
+            arg => $crate::format_ident_impl!([$span.or(arg.span()), $($fmt)*, arg] $($rest)*),
+        }
+    };
+}