parametric vararg resumable function throws when called with no arguments

[singhharsh1708]

A parametric vararg resumable function throws when it's called with no arguments.

using ResumableFunctions

@resumable function res(a::T...) where T
    @yield length(a)
end

collect(res(1, 2))  # Any[2]
collect(res())      # UndefVarError: `T` not defined in static parameter matching

The plain function returns 0 there. The wrapper constructs the state machine as ##res_FSMI#...{T}, and an empty vararg leaves T unbound.

Recursion that peels arguments off hits it on the last step:

@resumable function peel(a::T...) where T
    if !isempty(a)
        @yield first(a)
        @yieldfrom peel(Base.tail(a)...)
    end
end

collect(peel(1, 2, 3))  # same UndefVarError

v1.0.7, same on julia 1.10.10, 1.11.9 and 1.12.7. On 1.10 the message is just UndefVarError: T not defined.