Prune unused constant expressions recursively.

[maleadt]

Fixes #680

[github-actions]

Your PR requires formatting changes to meet the project's style guidelines.
Please consider running Runic (git runic master) to apply these changes.

Click here to view the suggested changes.

diff --git a/src/utils.jl b/src/utils.jl
index cc03122..9798bef 100644
--- a/src/utils.jl
+++ b/src/utils.jl
@@ -148,4 +148,5 @@ function prune_constexpr_uses!(root::LLVM.Value)
             isempty(uses(val)) && LLVM.unsafe_destroy!(val)
         end
     end
+    return
 end