From fffee9f0b59fbb36983b5d5f6bd0ebb1f2230a76 Mon Sep 17 00:00:00 2001
From: DanS <dan-s-dev@proton.me>
Date: Thu, 23 Jul 2026 21:30:16 -0500
Subject: [PATCH] build(lite-backend): pin the SDXL backend to rustc 1.63 via
 rust-toolchain.toml
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The pinned librustzcash / transitive crates (notably traitobject 0.1.0) rely on
pre-1.70 trait coherence and fail to compile on newer rustc (E0119), so the backend
must build with 1.63. Add a rust-toolchain.toml in the vendored backend so rustup
auto-selects 1.63 when cargo runs there — no more manual RUSTUP_TOOLCHAIN=1.63.0.
The pin is scoped to the backend tree (repo-root cargo keeps the default toolchain).
Also symlink the pin into the prepared build root so --silentdragonxlitelib-dir
builds honor it too.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
---
 scripts/build-lite-backend-artifact.sh               |  3 +++
 .../silentdragonxlite/lib/rust-toolchain.toml        | 12 ++++++++++++
 2 files changed, 15 insertions(+)
 create mode 100644 third_party/silentdragonxlite/lib/rust-toolchain.toml

diff --git a/scripts/build-lite-backend-artifact.sh b/scripts/build-lite-backend-artifact.sh
index f83072c..6e600ea 100755
--- a/scripts/build-lite-backend-artifact.sh
+++ b/scripts/build-lite-backend-artifact.sh
@@ -324,6 +324,9 @@ prepare_backend_source() {
     ln -s "$BACKEND_SOURCE_DIR/src" "$prepared_root/src"
     [[ -f "$BACKEND_SOURCE_DIR/Cargo.lock" ]] && ln -s "$BACKEND_SOURCE_DIR/Cargo.lock" "$prepared_root/Cargo.lock"
     [[ -d "$BACKEND_SOURCE_DIR/.cargo" ]] && ln -s "$BACKEND_SOURCE_DIR/.cargo" "$prepared_root/.cargo"
+    # Honor the pinned Rust toolchain (rust-toolchain.toml) inside the prepared root too,
+    # so builds using --silentdragonxlitelib-dir still select rustc 1.63.
+    [[ -f "$BACKEND_SOURCE_DIR/rust-toolchain.toml" ]] && ln -s "$BACKEND_SOURCE_DIR/rust-toolchain.toml" "$prepared_root/rust-toolchain.toml"
     [[ -d "$BACKEND_SOURCE_DIR/libsodium-mingw" ]] && ln -s "$BACKEND_SOURCE_DIR/libsodium-mingw" "$prepared_root/libsodium-mingw"
     # Vendored crate deps (offline builds): the .cargo/config.toml's vendored-sources directory is
     # "vendor" relative to the build root, so expose it inside the prepared root too.
diff --git a/third_party/silentdragonxlite/lib/rust-toolchain.toml b/third_party/silentdragonxlite/lib/rust-toolchain.toml
new file mode 100644
index 0000000..35f85f2
--- /dev/null
+++ b/third_party/silentdragonxlite/lib/rust-toolchain.toml
@@ -0,0 +1,12 @@
+# Rust toolchain pin for the vendored SilentDragonXLite (SDXL) backend.
+#
+# The pinned librustzcash + transitive crates (notably traitobject 0.1.0) rely on
+# pre-1.70 trait-coherence rules and fail to compile on newer rustc with
+#   error[E0119]: conflicting implementations of trait `Trait` for type `(dyn Send + Sync)`
+# so the backend must be built with 1.63 (the toolchain scripts/build-lite-backend-artifact.sh
+# and CLAUDE.md target). rustup auto-selects this when cargo runs in this tree, so no
+# RUSTUP_TOOLCHAIN / `cargo +1.63.0` is needed.
+#
+# Install it once with:  rustup toolchain install 1.63.0
+[toolchain]
+channel = "1.63.0"