rust: enable rustdoc's `--generate-link-to-definition`

In Rust 1.56.0 [1], rustdoc introduced the "jump to definition"
feature [2], i.e. the unstable flag `--generate-link-to-definition`.
It adds links to the source view of the documentation.

For instance, in the source view of `rust/kernel/sync.rs`, for this code:

    impl Default for LockClassKey {
        fn default() -> Self {
            Self::new()
        }
    }

It will add three hyperlinks:

  - `Default` points to the rendered "Trait `core::default::Default`"
    page (not the source view, since it goes to another crate, though
    this may change).

  - `LockClassKey` points to the `pub struct LockClassKey(...);` line
    in the same page, highlighting the line number.

  - `Self::new()` points to the `pub const fn new() -> Self { ... }`
    associated function, highlighting its line numbers (i.e. for the
    full function).

This makes the source view more useful and a bit closer to the experience
in e.g. the Elixir Cross Referencer [3].

I have provisionally enabled it for rust.docs.kernel.org [4] -- one can
take a look at the source view there for an example of how it looks like.

Thus enable it.

Cc: Guillaume Gomez <guillaume1.gomez@gmail.com>
Link: https://github.com/rust-lang/rust/pull/84176
Link: https://github.com/rust-lang/rust/issues/89095
Link: https://elixir.bootlin.com
Link: https://rust.docs.kernel.org
Reviewed-by: Gary Guo <gary@garyguo.net>
Link: https://lore.kernel.org/r/20240818141249.387166-1-ojeda@kernel.org
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>

diff --git a/rust/Makefile b/rust/Makefile
index c24c3689e7b4c06e51a1e38fb8a4d2c81b8c9aa2..e13d14ec5fe74c4f90c5e5f09d0e9ecfb8a5e171 100644 (file)
--- a/rust/Makefile
+++ b/rust/Makefile
@@ -63,6 +63,7 @@ quiet_cmd_rustdoc = RUSTDOC $(if $(rustdoc_host),H, ) $<
        OBJTREE=$(abspath $(objtree)) \
        $(RUSTDOC) $(if $(rustdoc_host),$(rust_common_flags),$(rust_flags)) \
                $(rustc_target_flags) -L$(objtree)/$(obj) \
+               -Zunstable-options --generate-link-to-definition \
                --output $(rustdoc_output) \
                --crate-name $(subst rustdoc-,,$@) \
                $(if $(rustdoc_host),,--sysroot=/dev/null) \