Error DataType has no field ninitialized when saving Tuple

[jlapeyre]

julia> import JLD2

julia> JLD2.save("tst.jld2", "x", (1,2))
Error encountered while save FileIO.File{FileIO.DataFormat{:JLD2}, String}("tst.jld2").

Fatal error:
ERROR: type DataType has no field ninitialized
...

[033835bb] JLD2 v0.4.9

Julia: Version 1.7.0-DEV.1290, 6e8754337a*

EDIT:
The bug does not occur in
Julia 1.7.0-DEV.961, 2435f96f92*

[BoundaryValueProblems]

Yes, I have exactly the same problem.

[JonasIsensee]

As I mentioned in #320
Julia is changing internals too fast for me to keep up at the moment.

#320 (comment)

The way forward is to figure out what has changed in julia and change the code in JLD2 accordingly.
(Using @static if VERSION < v"1.7.0-A" blocks to keep compatibility to earlier versions)

[JonasIsensee]

This appears to be the culprit
JuliaLang/julia#41018

[PaulSoderlind]

another data point: same problem on Julia-1.7.0-beta2 when saving a Dict

using FileIO, JLD2
D = Dict("a"=>"Hazel")
save("test.jld2","D",D)

gives

Error encountered while save File{DataFormat{:JLD2}, String}("test.jld2").                          
                                                  
Fatal error:                                      
ERROR: LoadError: type DataType has no field ninitialized      ...