Change Dict to be ordered by default

[PallHaraldsson]

Fixes: #34265 Supersedes my #37804. See also my argument: #37761 (comment)

[EDIT: Based on @oxinabox code, OrderedDict from OrderedCollections.jl; as changing Dict to be ordered is unworkable for me, seems proven a breaking change, this PR is abandoned.]

[PallHaraldsson]

I fixed non-serious docs failures, and this also went away, a false alam unrelated to my stuff(?):

cp: cannot stat 'dist-extras/7z.*': No such file or directory

[tpapp]

As suggested in the discussion, please provide motivation for this. In particular, cf the discussions in #34265 and #10116.

Benchmarks would be interesting too.

[PallHaraldsson]

The motivation is in the discussion you linked, and Jeff, Stefan and a lot of others want ordered by default, see this thread/comment:
#10116 (comment)

[PallHaraldsson]

@JeffBezanson, this is probably ready for package eval, and it seems time sensitive for Julia 1.6.

I intentionally have Set unordered with older renamed Dict:

struct Set{T} <: AbstractSet{T}
    dict::UDict{T,Nothing}

It's something that could be changed later, seems not as important to me, unless you would want them in sync, both ordered (or not). I saw you can make some operation faster with ordered sets (while it wouldn't be with just Set changed to ordered).

EDIT2: I'll look into (while I've yet to see a connection to my change):

compiler/inference                 (5) |         failed at 2020-10-23T12:59:28.415
Test Failed at /buildworker/worker/tester_linux64/build/share/julia/test/compiler/inference.jl:1175
  Expression: Core.Compiler.invoke_api(linfo) == 2
   Evaluated: -1 == 2
Error During Test at /buildworker/worker/tester_linux64/build/share/julia/test/compiler/inference.jl:1201
  Expression evaluated to non-Boolean
  Expression: false || "Side effect expressions found $(ex)"
       Value: "Side effect expressions found Main.Test90Main_compiler_inference.fieldtype(Dict{Int64, Nothing}, :age)"
compiler/ssair                     (6) |     3.23 |   0.08 |  2.6 |     102.52 |   972.80
compiler/irpasses                  (6) |        started at 2020-10-23T12:59:28.547
compiler/irpasses                  (6) |     1.52 |   0.06 |  4.1 |     116.87 |   972.80
compiler/codegen                   (6) |        started at 2020-10-23T12:59:30.094
compiler/inline                    (8) |        started at 2020-10-23T12:59:38.034
compiler/codegen                   (6) |         failed at 2020-10-23T12:59:39.970
Test Failed at /buildworker/worker/tester_linux64/build/share/julia/test/compiler/codegen.jl:451
  Expression: success(`$(Base.julia_cmd()) --startup-file=no -e $str_36422`)
compiler/inline                    (8) |     1.83 |   0.02 |  1.3 |      94.67 |   310.91

EDIT: FYI, there are false alarms probably, but also:

dict                               (4) |         failed at 2020-10-23T13:01:44.303
Error During Test at /buildworker/worker/tester_linux64/build/share/julia/test/dict.jl:837
  Got exception outside of a @test
  Conversion to Dict is deprecated for unordered associative containers (in this case, WeakKeyDict{Any, Any}). Use an ordered or sorted associative type, such as SortedDict and Dict.
  Stacktrace:
    [1] depwarn(msg::String, funcsym::Symbol; force::Bool)
      @ Base ./deprecated.jl:82
    [2] depwarn(msg::String, funcsym::Symbol)
      @ Base ./deprecated.jl:80
    [3] convert(#unused#::Type{Dict{Any, Any}}, d::WeakKeyDict{Any, Any})
      @ Base ./ordered_dict.jl:92
    [4] macro expansion
      @ /buildworker/worker/tester_linux64/build/share/julia/test/dict.jl:847 [inlined]
    [5] macro expansion
      @ /buildworker/worker/package_linux64/build/usr/share/julia/stdlib/v1.6/Test/src/Test.jl:1144 [inlined]
    [6] top-level scope
      @ /buildworker/worker/tester_linux64/build/share/julia/test/dict.jl:838
    [7] include
      @ ./Base.jl:393 [inlined]
    [8] macro expansion
      @ /buildworker/worker/tester_linux64/build/share/julia/test/testdefs.jl:24 [inlined]
    [9] macro expansion
      @ /buildworker/worker/package_linux64/build/usr/share/julia/stdlib/v1.6/Test/src/Test.jl:1144 [inlined]
   [10] macro expansion
      @ /buildworker/worker/tester_linux64/build/share/julia/test/testdefs.jl:23 [inlined]
   [11] macro expansion
      @ ./timing.jl:343 [inlined]
   [12] runtests(name::String, path::String, isolate::Bool; seed::UInt128)
      @ Main /buildworker/worker/tester_linux64/build/share/julia/test/testdefs.jl:21
   [13] (::Distributed.var"#106#108"{Distributed.CallMsg{:call_fetch}})()
      @ Distributed /buildworker/worker/package_linux64/build/usr/share/julia/stdlib/v1.6/Distributed/src/process_messages.jl:278
   [14] run_work_thunk(thunk::Distributed.var"#106#108"{Distributed.CallMsg{:call_fetch}}, print_error::Bool)
      @ Distributed /buildworker/worker/package_linux64/build/usr/share/julia/stdlib/v1.6/Distributed/src/process_messages.jl:63
   [15] macro expansion
      @ /buildworker/worker/package_linux64/build/usr/share/julia/stdlib/v1.6/Distributed/src/process_messages.jl:278 [inlined]
   [16] (::Distributed.var"#105#107"{Distributed.CallMsg{:call_fetch}, Distributed.MsgHeader, Sockets.TCPSocket})()
      @ Distributed ./task.jl:395
Test Failed at /buildworker/worker/tester_linux64/build/share/julia/test/dict.jl:1038
  Expression: pop!(d)
    Expected: ArgumentError
      Thrown: BoundsError
iobuffer                          (10) |        started at 2020-10-23T13:01:53.120

EDIT3:
https://build.julialang.org/#/builders/39/builds/4436
Will change Set back as, otherwise I get error for:
no method matching ht_keyindex2!(::Dict{Vector{Int64}, Nothing}, ::Vector{Int64})
no method matching skip_deleted_floor!(::Dict{Int64, Nothing})

[PallHaraldsson]

EDIT: At least one actual failure (but also in the original where I took the code from), giving stack-overflow: JuliaCollections/OrderedCollections.jl#65 I'm actually not too sure it's a bug in the recursive deepcopy test code, and if, if we want to keep bug-compatibility.

The 3 so-far buildbot/tester_* failures (and 3 more coming?) seem like false alarms, or something I do not understand, related to:

ps = _spawn(cmds, spawn_opts_inherit(args...))
success(ps) || pipeline_error(ps)