rust: proc-macro2: import crate

This is a subset of the Rust `proc-macro2` crate, version 1.0.101
(released 2025-08-16), licensed under "Apache-2.0 OR MIT", from:

    https://github.com/dtolnay/proc-macro2/raw/1.0.101/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/proc-macro2/blob/1.0.101/README.md#license
    https://github.com/dtolnay/proc-macro2/blob/1.0.101/LICENSE-APACHE
    https://github.com/dtolnay/proc-macro2/blob/1.0.101/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 $(cd rust/proc-macro2/ && find . -type f -name '*.rs'); do
        curl --silent --show-error --location \
            https://github.com/dtolnay/proc-macro2/raw/1.0.101/src/$path \
            | diff --unified rust/proc-macro2/$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/20251124151837.2184382-7-ojeda@kernel.org
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>

1 files changed, 21 insertions, 0 deletions

diff --git a/rust/proc-macro2/probe/proc_macro_span_location.rs b/rust/proc-macro2/probe/proc_macro_span_location.rs
new file mode 100644
index 000000000000..79da34af54af
--- /dev/null
+++ b/rust/proc-macro2/probe/proc_macro_span_location.rs
@@ -0,0 +1,21 @@
+// The subset of Span's API stabilized in Rust 1.88.
+
+extern crate proc_macro;
+
+use proc_macro::Span;
+
+pub fn start(this: &Span) -> Span {
+    this.start()
+}
+
+pub fn end(this: &Span) -> Span {
+    this.end()
+}
+
+pub fn line(this: &Span) -> usize {
+    this.line()
+}
+
+pub fn column(this: &Span) -> usize {
+    this.column()
+}