gnu: rust: Install stdlib manifest with original checksums.

* gnu/packages/rust.scm (rust)[arguments]: Install stdlib manifest with
the original checksums.

Change-Id: I1100ffe4ff67c8e2026e802fc3902ec218e2efee
Signed-off-by: Efraim Flashner <efraim@flashner.co.il>

1 files changed, 17 insertions, 0 deletions

diff --git a/gnu/packages/rust.scm b/gnu/packages/rust.scm
index bf7eeb5fbf5..77441bc6237 100644
--- a/gnu/packages/rust.scm
+++ b/gnu/packages/rust.scm
@@ -1475,12 +1475,29 @@ safety and thread safety guarantees.")
                  (invoke "./x.py" "install" "clippy")
                  (invoke "./x.py" "install" "rust-analyzer")
                  (invoke "./x.py" "install" "rustfmt")))
+             (add-before 'patch-cargo-checksums 'save-old-library-manifest
+               (lambda _
+                 (copy-file "library/Cargo.lock" ".old-library-manifest")))
              (add-after 'install 'install-rust-src
                (lambda* (#:key outputs #:allow-other-keys)
                  (let ((out (assoc-ref outputs "rust-src"))
                        (dest "/lib/rustlib/src/rust"))
                    (mkdir-p (string-append out dest))
                    (copy-recursively "library" (string-append out dest "/library"))
+                   ;; rust-analyzer needs the original checksums; otherwise
+                   ;; it fails to cargo manifest in the stdlib, and then
+                   ;; analysis/inference involving stdlib structs doesn't work.
+                   ;;
+                   ;; For example, in the following trivial program:
+                   ;;
+                   ;; fn main() {
+                   ;;     let x = Vec::<usize>::new();
+                   ;; }
+                   ;;
+                   ;; rust-analyzer since version 1.82 can't infer
+                   ;; the type of x unless the following line is present.
+                   (copy-file ".old-library-manifest"
+                              (string-append out dest "/library/Cargo.lock"))
                    (copy-recursively "src" (string-append out dest "/src")))))
              (add-before 'install 'remove-uninstall-script
                (lambda _