Cumsum with list comprehension

question

#1

Why does this work:

julia> sum(i for i in 1:3)
6

but not this:

julia> cumsum(i for i in 1:3)
ERROR: MethodError: no method matching cumsum(::Base.Generator{UnitRange{Int64},##13#14})

#2

https://github.com/JuliaLang/julia/issues/21150