[bug#66870] [PATCH 3/6] gnu: Add function2.

[Sughosha]

From: Sughosha <sughosha@proton.me>

* gnu/packages/cpp.scm (function2): New variable.

Change-Id: I29eb928aa943fa6b796d699271ca523075d44d38
---
 gnu/packages/cpp.scm | 33 +++++++++++++++++++++++++++++++++
 1 file changed, 33 insertions(+)

diff --git a/gnu/packages/cpp.scm b/gnu/packages/cpp.scm
index 7d91c72489..6c99f39639 100644
--- a/gnu/packages/cpp.scm
+++ b/gnu/packages/cpp.scm
@@ -2302,6 +2302,39 @@ (define-public bitsery
     (home-page "https://github.com/fraillt/bitsery";)
     (license license:expat)))
 
+(define-public function2
+  (package
+    (name "function2")
+    (version "4.2.3")
+    (source (origin
+              (method git-fetch)
+              (uri (git-reference
+                    (url "https://github.com/Naios/function2";)
+                    (commit version)
+                    ;; Tests require to compile googletest with custom
+                    ;; features.
+                    (recursive? #t)))
+              (file-name (git-file-name name version))
+              (sha256
+               (base32
+                "0zdi6jk3srjkx82kbmd9rfmj9c1rr2xlsz2hbdcjvcjp63vzzxd1"))))
+    (build-system cmake-build-system)
+    ;; The test size_match_layout fails on i586/i686. For more info:
+    ;; https://github.com/Naios/function2/issues/57
+    (arguments
+     (list #:tests? #f))
+    (synopsis "Improved implementations of std::function")
+    (description "This package provides the following implementations of
+std::function:
+@itemize
+@item copyable fu2::function
+@item move-only fu2::unique_function (capable of holding move only types)
+@item non-owning fu2::function_view (capable of referencing callables in a non
+owning way)
+@end itemize")
+    (home-page "https://naios.github.io/function2/";)
+    (license license:boost1.0)))
+
 (define-public cpp-mustache
   (package
     (name "cpp-mustache")
-- 
2.41.0