Use array type in cache key instead of element type

src/cache.jl

@@ -49,15 +49,15 @@ Base.copy(cache::JacobianCache) = JacobianCache(copy(cache.duals), cache.seeds)
 
 @eval function multithread_jacobian_cachefetch!{N}(x, chunk::Chunk{N}, usecache::Bool,
                                                    alt::Bool = false)
-    T, xlen = eltype(x), length(x)
+    T, S, xlen = typeof(x), eltype(x), length(x)
     if usecache
         result = get!(JACOBIAN_CACHE, (xlen, N, T, alt)) do
             construct_jacobian_caches(x, chunk)
         end
     else
         result = construct_jacobian_caches(x, chunk)
     end
-    return result::NTuple{$NTHREADS,JacobianCache{N,T,jacobian_dual_type(x, chunk)}}
+    return result::NTuple{$NTHREADS,JacobianCache{N,S,jacobian_dual_type(x, chunk)}}
 end
 
 jacobian_cachefetch!(args...) = multithread_jacobian_cachefetch!(args...)[compat_threadid()]
@@ -88,15 +88,15 @@ end
 Base.copy(cache::HessianCache) = HessianCache(copy(cache.duals), cache.inseeds, cache.outseeds)
 
 @eval function multithread_hessian_cachefetch!{N}(x, chunk::Chunk{N}, usecache::Bool)
-    T = eltype(x)
+    T, S = typeof(x), eltype(x)
     if usecache
         result = get!(HESSIAN_CACHE, (N, T)) do
             construct_hessian_caches(x, chunk)
         end
     else
         result = construct_hessian_caches(x, chunk)
     end
-    return result::NTuple{$NTHREADS,HessianCache{N,T,hessian_dual_type(x, chunk)}}
+    return result::NTuple{$NTHREADS,HessianCache{N,S,hessian_dual_type(x, chunk)}}
 end
 
 hessian_cachefetch!(args...) = multithread_hessian_cachefetch!(args...)[compat_threadid()]