WeakKeyDict c-tor for Pairs is broken due to missing sizehint!

[kshyatt]

MWE:

julia> A = [1]; B = [2]; C = [3];

julia> WeakKeyDict{typeof(A), Int64}(Pair(A, 1), Pair(B, 2), Pair(C, 3))
hi
ERROR: MethodError: no method matching sizehint!(::WeakKeyDict{Array{Int64,1},Int64}, ::Int64)
Closest candidates are:
  sizehint!(::Array{T,1} where T, ::Integer) at array.jl:1092
  sizehint!(::IdDict, ::Any) at iddict.jl:59
  sizehint!(::Base.IdSet, ::Any) at idset.jl:23
  ...
Stacktrace:
 [1] WeakKeyDict{Array{Int64,1},Int64}(::Pair{Array{Int64,1},Int64}, ::Vararg{Pair{Array{Int64,1},Int64},N} where N) at ./weakkeydict.jl:45
 [2] top-level scope at REPL[2]:1

this is happening in this constructor which is currently untested.

[JeffBezanson]

Oof, good find. It just needs to pass sizehint! to the wrapped Dict.