scripts: generate_rust_analyzer: add missing macros deps

[ Upstream commit 2e0f91a ]

The macros crate has depended on std and proc_macro since its
introduction in commit 1fbde52 ("rust: add `macros` crate"). These
dependencies were omitted from commit 8c4555c ("scripts: add
`generate_rust_analyzer.py`") resulting in missing go-to-definition and
autocomplete, and false-positive warnings emitted from rust-analyzer
such as:

  [{
  	"resource": "/Users/tamird/src/linux/rust/macros/module.rs",
  	"owner": "_generated_diagnostic_collection_name_#1",
  	"code": {
  		"value": "non_snake_case",
  		"target": {
  			"$mid": 1,
  			"path": "/rustc/",
  			"scheme": "https",
  			"authority": "doc.rust-lang.org",
  			"query": "search=non_snake_case"
  		}
  	},
  	"severity": 4,
  	"message": "Variable `None` should have snake_case name, e.g. `none`",
  	"source": "rust-analyzer",
  	"startLineNumber": 123,
  	"startColumn": 17,
  	"endLineNumber": 123,
  	"endColumn": 21
  }]

Add the missing dependencies to improve the developer experience.

  [ Fiona had a different approach (thanks!) at:

        https://lore.kernel.org/rust-for-linux/20241205115438.234221-1-me@kloenk.dev/

    But Tamir and Fiona agreed to this one. - Miguel ]

Fixes: 8c4555c ("scripts: add `generate_rust_analyzer.py`")
Reviewed-by: Fiona Behrens <me@kloenk.dev>
Diagnosed-by: Chayim Refael Friedman <chayimfr@gmail.com>
Link: rust-lang/rust-analyzer#17759 (comment)
Signed-off-by: Tamir Duberstein <tamird@gmail.com>
Tested-by: Andreas Hindborg <a.hindborg@kernel.org>
Link: https://lore.kernel.org/r/20250210-rust-analyzer-macros-core-dep-v3-1-45eb4836f218@gmail.com
[ Removed `return`. Changed tag name. Added Link. Slightly
  reworded. - Miguel ]
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>

Author: tamird

scripts/generate_rust_analyzer.py

@@ -49,14 +49,26 @@ def append_crate(display_name, root_module, deps, cfg=[], is_workspace_member=Tr
             }
         })
 
-    # First, the ones in `rust/` since they are a bit special.
-    append_crate(
-        "core",
-        sysroot_src / "core" / "src" / "lib.rs",
-        [],
-        cfg=crates_cfgs.get("core", []),
-        is_workspace_member=False,
-    )
+    def append_sysroot_crate(
+        display_name,
+        deps,
+        cfg=[],
+    ):
+        append_crate(
+            display_name,
+            sysroot_src / display_name / "src" / "lib.rs",
+            deps,
+            cfg,
+            is_workspace_member=False,
+        )
+
+    # NB: sysroot crates reexport items from one another so setting up our transitive dependencies
+    # here is important for ensuring that rust-analyzer can resolve symbols. The sources of truth
+    # for this dependency graph are `(sysroot_src / crate / "Cargo.toml" for crate in crates)`.
+    append_sysroot_crate("core", [], cfg=crates_cfgs.get("core", []))
+    append_sysroot_crate("alloc", ["core"])
+    append_sysroot_crate("std", ["alloc", "core"])
+    append_sysroot_crate("proc_macro", ["core", "std"])
 
     append_crate(
         "compiler_builtins",
@@ -67,7 +79,7 @@ def append_crate(display_name, root_module, deps, cfg=[], is_workspace_member=Tr
     append_crate(
         "macros",
         srctree / "rust" / "macros" / "lib.rs",
-        [],
+        ["std", "proc_macro"],
         is_proc_macro=True,
     )
     crates[-1]["proc_macro_dylib_path"] = f"{objtree}/rust/libmacros.so"