Bug 1878778 - Mark ICU4XDataStruct as dead code as it's never read from Rust. r=m_kato

Differential Revision: https://phabricator.services.mozilla.com/D200734

intl/icu4x-patches/004-dead-code.patch

@@ -0,0 +1,13 @@
+diff --git a/intl/icu_capi/src/data_struct.rs b/intl/icu_capi/src/data_struct.rs
+index d66e20b117b58..60765cec2419a 100644
+--- a/intl/icu_capi/src/data_struct.rs
++++ b/intl/icu_capi/src/data_struct.rs
+@@ -20,7 +20,7 @@ pub mod ffi {
+     ///
+     /// This can be used to construct a StructDataProvider.
+     #[diplomat::attr(dart, disable)]
+-    pub struct ICU4XDataStruct(pub(crate) AnyPayload);
++    pub struct ICU4XDataStruct(#[allow(dead_code)] AnyPayload);
+ 
+     impl ICU4XDataStruct {
+         /// Construct a new DecimalSymbolsV1 data struct.

intl/icu4x-patches/README

@@ -10,6 +10,10 @@ A patch for icu_capi for clang and static analysis.
 
 A patch for icu_capi to add explicit keyword
 
+### 004-dead-code.patch
+
+A patch for icu_capi to mark the ICU4XDataStruct as dead code as it's never read from Rust.
+
 ### empty.toml
 
 Empty toml data for trie_data for icu_segmenter_data.

intl/icu_capi/src/data_struct.rs

@@ -20,7 +20,7 @@ pub mod ffi {
     ///
     /// This can be used to construct a StructDataProvider.
     #[diplomat::attr(dart, disable)]
-    pub struct ICU4XDataStruct(pub(crate) AnyPayload);
+    pub struct ICU4XDataStruct(#[allow(dead_code)] AnyPayload);
 
     impl ICU4XDataStruct {
         /// Construct a new DecimalSymbolsV1 data struct.

intl/update-icu4x.sh

@@ -83,6 +83,7 @@ for patch in \
     001-Cargo.toml.patch \
     002-GH4109.patch \
     003-explicit.patch \
+    004-dead-code.patch \
 ; do
     patch -d ${top_src_dir} -p1 --no-backup-if-mismatch < ${top_src_dir}/intl/icu4x-patches/$patch
 done