done by FluxML/Zygote.jl#498

Michael Abbott · Michael Abbott · commit e8a79cf3fae5 · 2020-02-29T14:51:05.000+01:00
diff --git a/src/LazyStack.jl b/src/LazyStack.jl
@@ -369,10 +369,6 @@ end
     stack(gen), Δ -> error("not yet!")
 end
 
-@adjoint function Base.collect(x::Stacked)
-    collect(x), tuple
-end
-
 #===== CuArrays =====#
 # Send these to stack_iter, by testing  storage_type(first(xs)) <: Array
 
