TypeError happens when constructing Fix2 struct with Vararg Tuple

[aviatesk]

master (70b6afa):

julia> isequal(Tuple{Vararg{Int, N}} where N)
julia> isequal(Tuple{Vararg{Int, N}} where N)
ERROR: TypeError: in new, expected DataType, got Type{Tuple{Vararg{Int64, N}} where N}
Stacktrace:
 [1] Base.Fix2(f::typeof(isequal), x::Type{Tuple{Vararg{Int64}}})
   @ Base ./operators.jl:1059
 [2] isequal(x::Type)
   @ Base ./operators.jl:1074
 [3] top-level scope
   @ none:1

1.6-rc1

julia> isequal(Tuple{Vararg{Int, N}} where N)
(::Base.Fix2{typeof(isequal), UnionAll}) (generic function with 1 method)

I confirmed this issue disappears after checking out to 3635f04, so I guess this is caused by 8fc5293 .

/cc @vtjnash

[vtjnash]

Duplicate of #35661