gnu: Add ghc-unagi-chan.

* gnu/packages/haskell-xyz.scm (ghc-unagi-chan): New variable.

gnu/packages/haskell-xyz.scm

@@ -10628,6 +10628,37 @@ (define-public ghc-typed-process
 upon it.")
     (license license:expat)))
 
+(define-public ghc-unagi-chan
+  (package
+    (name "ghc-unagi-chan")
+    (version "0.4.1.2")
+    (source
+     (origin
+       (method url-fetch)
+       (uri (string-append "https://hackage.haskell.org/package/unagi-chan"
+                           "/unagi-chan-" version ".tar.gz"))
+       (sha256
+        (base32
+         "1lnl5n4jnjmm4chp461glcwkrrw63rjz3fvprwxcy3lkpbkrqvgn"))))
+    (build-system haskell-build-system)
+    (inputs
+     `(("ghc-atomic-primops" ,ghc-atomic-primops)
+       ("ghc-primitive" ,ghc-primitive)))
+    (arguments
+     `(#:tests? #f ; FIXME: Tests expect primitive 0.7
+       #:cabal-revision
+       ("1"
+        "09pqi867wskwgc5lpn197f895mbn1174ydgllvcppcsmrz2b6yr6")))
+    (home-page "http://hackage.haskell.org/package/unagi-chan")
+    (synopsis "Fast concurrent queues with a Chan-like API, and more")
+    (description
+     "This library provides implementations of concurrent FIFO queues (for
+both general boxed and primitive unboxed values) that are fast, perform well
+under contention, and offer a Chan-like interface.  The library may be of
+limited usefulness outside of x86 architectures where the fetch-and-add
+instruction is not available.")
+    (license license:bsd-3)))
+
 (define-public ghc-unbounded-delays
   (package
     (name "ghc-unbounded-delays")