diff --git a/src/tracker/array.jl b/src/tracker/array.jl index bb55ef73..89dcfac9 100644 --- a/src/tracker/array.jl +++ b/src/tracker/array.jl @@ -41,7 +41,7 @@ end Base.setindex!(xs::TrackedArray, v, i...) = error("Can't differentiate `setindex!`") -back!(::TrackedArray) = error("Use back!(x, Δ)") +back!(::TrackedArray) = error("Value is not scalar; use `back!(sum(x))` or `back!(x, Δ)`") # Fallthrough methods