rust: macros: support proc-macro2, quote and syn

One of the two main uses cases for adding `proc-macro2`, `quote` and
`syn` is the `macros` crates (and the other `pin-init`).

Thus add the support for the crates in `macros` already.

Tested-by: Jesung Yang <y.j3ms.n@gmail.com>
Link: https://patch.msgid.link/20251124151837.2184382-21-ojeda@kernel.org
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>

rust/Makefile

@@ -184,7 +184,7 @@ rustdoc-syn: $(src)/syn/lib.rs rustdoc-clean rustdoc-quote FORCE
 
 rustdoc-macros: private rustdoc_host = yes
 rustdoc-macros: private rustc_target_flags = --crate-type proc-macro \
-    --extern proc_macro
+    --extern proc_macro --extern proc_macro2 --extern quote --extern syn
 rustdoc-macros: $(src)/macros/lib.rs rustdoc-clean rustdoc-proc_macro2 \
     rustdoc-quote rustdoc-syn FORCE
 	+$(call if_changed,rustdoc)
@@ -256,9 +256,11 @@ rusttestlib-syn: private rustc_target_flags = $(syn-flags)
 rusttestlib-syn: $(src)/syn/lib.rs rusttestlib-quote FORCE
 	+$(call if_changed,rustc_test_library)
 
-rusttestlib-macros: private rustc_target_flags = --extern proc_macro
+rusttestlib-macros: private rustc_target_flags = --extern proc_macro \
+    --extern proc_macro2 --extern quote --extern syn
 rusttestlib-macros: private rustc_test_library_proc = yes
-rusttestlib-macros: $(src)/macros/lib.rs FORCE
+rusttestlib-macros: $(src)/macros/lib.rs \
+    rusttestlib-proc_macro2 rusttestlib-quote rusttestlib-syn FORCE
 	+$(call if_changed,rustc_test_library)
 
 rusttestlib-pin_init_internal: private rustc_target_flags = --cfg kernel \
@@ -339,7 +341,8 @@ quiet_cmd_rustc_test = $(RUSTC_OR_CLIPPY_QUIET) T  $<
 rusttest: rusttest-macros
 
 rusttest-macros: private rustc_target_flags = --extern proc_macro \
-	--extern macros --extern kernel --extern pin_init
+    --extern macros --extern kernel --extern pin_init \
+    --extern proc_macro2 --extern quote --extern syn
 rusttest-macros: private rustdoc_test_target_flags = --crate-type proc-macro
 rusttest-macros: $(src)/macros/lib.rs \
     rusttestlib-macros rusttestlib-kernel rusttestlib-pin_init FORCE
@@ -529,6 +532,8 @@ quiet_cmd_rustc_procmacro = $(RUSTC_OR_CLIPPY_QUIET) P $@
 		@$(objtree)/include/generated/rustc_cfg $<
 
 # Procedural macros can only be used with the `rustc` that compiled it.
+$(obj)/$(libmacros_name): private rustc_target_flags = \
+    --extern proc_macro2 --extern quote --extern syn
 $(obj)/$(libmacros_name): $(src)/macros/lib.rs $(obj)/libproc_macro2.rlib \
     $(obj)/libquote.rlib $(obj)/libsyn.rlib FORCE
 	+$(call if_changed_dep,rustc_procmacro)

scripts/generate_rust_analyzer.py

@@ -110,7 +110,7 @@ def generate_crates(srctree, objtree, sysroot_src, external_src, cfgs, core_edit
     append_crate(
         "macros",
         srctree / "rust" / "macros" / "lib.rs",
-        ["std", "proc_macro"],
+        ["std", "proc_macro", "proc_macro2", "quote", "syn"],
         is_proc_macro=True,
     )