Sum with init doesn't work for empty iterable

[aplavin]

Documentation for sum says that The value returned for empty itr can be specified by init.. However, sum(i for i in 1:0, init=0) throws an error: ArgumentError: reducing over an empty collection is not allowed.
Same with sum(identity, i for i in 1:0, init=0).
This happens on both 1.6 and nightly. As I understand, empty collections were the whole point of introducing init= argument, is it just not implemented yet?

[kimikage]

Interestingly, it works with a semicolon.

julia> sum(i for i in 1:0; init=0)
0

julia> VERSION
v"1.6.0-rc1"

julia> @which sum(i for i in 1:0; init=0)
(::Base.var"#sum##kw")(::Any, ::typeof(sum), a) in Base at reduce.jl:528

julia> @which sum(i for i in 1:0, init=0)
sum(a; kw...) in Base at reduce.jl:528

[simeonschaub]

(i for i in 1:0, init=0) creates a two-dimensional generator, i.e. it's the same as (i for i in 1:0, init in 0), so init=0 is parsed as part of the generator, not as a keyword argument.