[PATCH 4/5] rust: backport deterministic DocLinkResMap serialisation

[sunilkumar.dora@windriver.com]

From: Sunil Dora <sunilkumar.dora@windriver.com>

Backport of rust-lang/rust commit f9d9939 by jprochazk and mejrs.
DocLinkResMap was an UnordMap, so its iteration order varied with the
build host and that order reached the encoded rmeta. An FxIndexMap keeps
it stable. The commit is in rust 1.99, so this only carries it until the
next rust upgrade.

[YOCTO #16376]

Signed-off-by: Sunil Dora <sunilkumar.dora@windriver.com>
---
 ...oc-link-metadata-order-deterministic.patch | 40 +++++++++++++++++++
 meta/recipes-devtools/rust/rust-source.inc    |  1 +
 2 files changed, 41 insertions(+)
 create mode 100644 meta/recipes-devtools/rust/files/0008-rustc-hir-make-doc-link-metadata-order-deterministic.patch

diff --git a/meta/recipes-devtools/rust/files/0008-rustc-hir-make-doc-link-metadata-order-deterministic.patch b/meta/recipes-devtools/rust/files/0008-rustc-hir-make-doc-link-metadata-order-deterministic.patch
new file mode 100644
index 0000000000..8cd64f21bb
--- /dev/null
+++ b/meta/recipes-devtools/rust/files/0008-rustc-hir-make-doc-link-metadata-order-deterministic.patch
@@ -0,0 +1,40 @@
+From 6630363e7bc9bc0926300e242aa538b8d92cdb95 Mon Sep 17 00:00:00 2001
+From: jprochazk <pjanv42@gmail.com>
+Date: Tue, 15 Sep 2026 17:05:36 +0530
+Subject: [PATCH] make DocLinkResMap an FxIndexMap
+
+DocLinkResMap was an UnordMap, so its iteration order varied with the build
+host and that order ended up in the encoded rmeta. An FxIndexMap keeps the
+serialisation stable. Only the code change is carried here, not the
+upstream run-make test.
+
+Upstream-Status: Backport [https://github.com/rust-lang/rust/commit/f9d9939467a5185a72f0ee8da778a0b71fc966ae]
+
+Signed-off-by: Sunil Dora <sunilkumar.dora@windriver.com>
+---
+ compiler/rustc_hir/src/def.rs | 6 ++++--
+ 1 file changed, 4 insertions(+), 2 deletions(-)
+
+diff --git a/compiler/rustc_hir/src/def.rs b/compiler/rustc_hir/src/def.rs
+index d0300d6..e903c0c 100644
+--- a/compiler/rustc_hir/src/def.rs
++++ b/compiler/rustc_hir/src/def.rs
+@@ -4,7 +4,7 @@ use std::fmt::Debug;
+ 
+ use rustc_ast as ast;
+ use rustc_ast::NodeId;
+-use rustc_data_structures::unord::UnordMap;
++use rustc_data_structures::fx::FxIndexMap;
+ use rustc_error_messages::{DiagArgValue, IntoDiagArg};
+ use rustc_macros::{Decodable, Encodable, StableHash};
+ use rustc_span::Symbol;
+@@ -969,4 +969,6 @@ pub enum LifetimeRes {
+     ElidedAnchor { start: NodeId, end: NodeId },
+ }
+ 
+-pub type DocLinkResMap = UnordMap<(Symbol, Namespace), Option<Res<NodeId>>>;
++// FxIndexMap is necessary because its data ends up in .rmeta files, so its
++// iteration order must be consistent. See #159677 for context.
++pub type DocLinkResMap = FxIndexMap<(Symbol, Namespace), Option<Res<NodeId>>>;
+-- 
+2.43.0
diff --git a/meta/recipes-devtools/rust/rust-source.inc b/meta/recipes-devtools/rust/rust-source.inc
index a294201c6e..a50a3fd001 100644
--- a/meta/recipes-devtools/rust/rust-source.inc
+++ b/meta/recipes-devtools/rust/rust-source.inc
@@ -10,6 +10,7 @@ SRC_URI += "https://static.rust-lang.org/dist/rustc-${RUST_VERSION}-src.tar.xz;n
             file://0004-Backport-commits-from-rust-Fix-selftest-llvm23.patch;patchdir=${RUSTSRC} \
             file://0005-rustc_codegen_llvm-Do-not-pass-amx-tf32-to-LLVM-23.patch;patchdir=${RUSTSRC} \
             file://0007-cargo-omit-host-triple-from-unit-metadata-hash.patch;patchdir=${RUSTSRC} \
+            file://0008-rustc-hir-make-doc-link-metadata-order-deterministic.patch;patchdir=${RUSTSRC} \
 "
 SRC_URI[rust.sha256sum] = "be1816e7f6c40abb90245ad6e024bed2a7e88d7dda4561e4d5470207df616b9f"
 
-- 
2.43.0