rust: syn: import crate

This is a subset of the Rust `syn` crate, version 2.0.106 (released
2025-08-16), licensed under "Apache-2.0 OR MIT", from:

    https://github.com/dtolnay/syn/raw/2.0.106/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/syn/blob/2.0.106/README.md#license
    https://github.com/dtolnay/syn/blob/2.0.106/LICENSE-APACHE
    https://github.com/dtolnay/syn/blob/2.0.106/LICENSE-MIT

The next two patches modify 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 $(cd rust/syn/ && find . -type f -name '*.rs'); do
        curl --silent --show-error --location \
            https://github.com/dtolnay/syn/raw/2.0.106/src/$path \
            | diff --unified rust/syn/$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/20251124151837.2184382-16-ojeda@kernel.org
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>

1 files changed, 73 insertions, 0 deletions

diff --git a/rust/syn/export.rs b/rust/syn/export.rs
new file mode 100644
index 000000000000..b9ea5c747b75
--- /dev/null
+++ b/rust/syn/export.rs
@@ -0,0 +1,73 @@
+#[doc(hidden)]
+pub use std::clone::Clone;
+#[doc(hidden)]
+pub use std::cmp::{Eq, PartialEq};
+#[doc(hidden)]
+pub use std::concat;
+#[doc(hidden)]
+pub use std::default::Default;
+#[doc(hidden)]
+pub use std::fmt::Debug;
+#[doc(hidden)]
+pub use std::hash::{Hash, Hasher};
+#[doc(hidden)]
+pub use std::marker::Copy;
+#[doc(hidden)]
+pub use std::option::Option::{None, Some};
+#[doc(hidden)]
+pub use std::result::Result::{Err, Ok};
+#[doc(hidden)]
+pub use std::stringify;
+
+#[doc(hidden)]
+pub type Formatter<'a> = std::fmt::Formatter<'a>;
+#[doc(hidden)]
+pub type FmtResult = std::fmt::Result;
+
+#[doc(hidden)]
+pub type bool = std::primitive::bool;
+#[doc(hidden)]
+pub type str = std::primitive::str;
+
+#[cfg(feature = "printing")]
+#[doc(hidden)]
+pub use quote;
+
+#[doc(hidden)]
+pub type Span = proc_macro2::Span;
+#[doc(hidden)]
+pub type TokenStream2 = proc_macro2::TokenStream;
+
+#[cfg(feature = "parsing")]
+#[doc(hidden)]
+pub use crate::group::{parse_braces, parse_brackets, parse_parens};
+
+#[doc(hidden)]
+pub use crate::span::IntoSpans;
+
+#[cfg(all(feature = "parsing", feature = "printing"))]
+#[doc(hidden)]
+pub use crate::parse_quote::parse as parse_quote;
+
+#[cfg(feature = "parsing")]
+#[doc(hidden)]
+pub use crate::token::parsing::{peek_punct, punct as parse_punct};
+
+#[cfg(feature = "printing")]
+#[doc(hidden)]
+pub use crate::token::printing::punct as print_punct;
+
+#[cfg(feature = "parsing")]
+#[doc(hidden)]
+pub use crate::token::private::CustomToken;
+
+#[cfg(feature = "proc-macro")]
+#[doc(hidden)]
+pub type TokenStream = proc_macro::TokenStream;
+
+#[cfg(feature = "printing")]
+#[doc(hidden)]
+pub use quote::{ToTokens, TokenStreamExt};
+
+#[doc(hidden)]
+pub struct private(pub(crate) ());