Replacement for Dict, is anyone using isslotfilled?

General Usage
16

Yes, and no, I mean it already happened, and seems impossible to fix while keeping bug-compatibility.* I thought I was almost done with my PR and then realized the specific undefined order is depended upon, even by Julia itself, by the test-failures I was seeing.

E.g.

julia> using REPL.REPLCompletions

julia> REPLCompletions.latex_symbols
Dict{String, String} with 2500 entries:
  "\\sqrt"        => "√"
  "\\cbrt"        => "∛"
  "\\female"      => "♀"
[..]

julia> REPL.symbol_latex("√")
"\\surd"

before this returned “\sqrt”, but while both are in a sense right, I would have to fix test errors that rely on something specific, here that (or better yet fix the dict-using code to get “\sqrt” again), and the broken tests seem endless, 1000+ lines to go through.

If/since there’s a “bug” here relying on specific “randomized” generated order (unlike the dict above with my “fix”, having same order as the listing from the file generating it: https://github.com/JuliaLang/julia/blob/b8df95fe05fabd821e26edf38008470b703fa36d/stdlib/REPL/src/latex_symbols.jl#L95), then such could be also be relied on by users code:

Error in testset docs:
Test Failed at C:\buildbot\worker-tabularasa\tester_win64\build\share\julia\test\docs.jl:1002
  Expression: sprint(repl_latex, "√") == "\"√\" can be typed by \\sqrt<tab>\n\n"
   Evaluated: "\"√\" can be typed by \\surd<tab>\n\n" == "\"√\" can be typed by \\sqrt<tab>\n\n"

* @stevengj, I know how to “fix” that in a sense, keep using the old unordered dict for that specific thing (and it would even be brittle if hashing is changed later).

I suspect more test failures are because the undefined order is relied upon, E.g.:

This one also worrying (and other one with “attempt to access 10-element Vector{Int64} at index [16]”):

Error During Test at C:\buildbot\worker-tabularasa\tester_win64\build\share\julia\test\loading.jl:586
  Got exception outside of a @test
  BoundsError: attempt to access 105-element Vector{String} at index [241]
  Stacktrace:
    [1] getindex
      @ .\array.jl:809 [inlined]
    [2] rand(rng::MersenneTwister, sp::Random.SamplerSimple{Dict{String, Any}, Random.SamplerSimple{LinearIndices{1, Tuple{Base.OneTo{Int64}}}, Random.SamplerRangeNDL{UInt64, Int64}, Int64}, Pair{String, Any}})
      @ Random C:\buildbot\worker\package_win64\build\usr\share\julia\stdlib\v1.6\Random\src\generation.jl:403
    [3] rand!(rng::MersenneTwister, A::Vector{Pair{String, Any}}, sp::Random.SamplerSimple{Dict{String, Any}, Random.SamplerSimple{LinearIndices{1, Tuple{Base.OneTo{Int64}}}, Random.SamplerRangeNDL{UInt64, Int64}, Int64}, Pair{String, Any}})
      @ Random C:\buildbot\worker\package_win64\build\usr\share\julia\stdlib\v1.6\Random\src\Random.jl:271
    [4] rand!
      @ C:\buildbot\worker\package_win64\build\usr\share\julia\stdlib\v1.6\Random\src\Random.jl:266 [inlined]
    [5] rand
      @ C:\buildbot\worker\package_win64\build\usr\share\julia\stdlib\v1.6\Random\src\Random.jl:279 [inlined]
    [6] rand(X::Dict{String, Any}, dims::Tuple{Int64})
      @ Random C:\buildbot\worker\package_win64\build\usr\share\julia\stdlib\v1.6\Random\src\Random.jl:280
    [7] rand
      @ C:\buildbot\worker\package_win64\build\usr\share\julia\stdlib\v1.6\Random\src\Random.jl:283 [inlined]
    [8] macro expansion
      @ C:\buildbot\worker-tabularasa\tester_win64\build\share\julia\test\loading.jl:587 [inlined]
    [9] macro expansion
      @ C:\buildbot\worker\package_win64\build\usr\share\julia\stdlib\v1.6\Test\src\Test.jl:1144 [inlined]
   [10] top-level scope
      @ C:\buildbot\worker-tabularasa\tester_win64\build\share\julia\test\loading.jl:587
   [11] include
      @ .\Base.jl:393 [inlined]
   [12] macro expansion
      @ C:\buildbot\worker-tabularasa\tester_win64\build\share\julia\test\testdefs.jl:24 [inlined]
   [13] macro expansion
      @ C:\buildbot\worker\package_win64\build\usr\share\julia\stdlib\v1.6\Test\src\Test.jl:1144 [inlined]
   [14] macro expansion
      @ C:\buildbot\worker-tabularasa\tester_win64\build\share\julia\test\testdefs.jl:23 [inlined]
   [15] macro expansion
      @ .\timing.jl:343 [inlined]
   [16] runtests(name::String, path::String, isolate::Bool; seed::UInt128)
      @ Main C:\buildbot\worker-tabularasa\tester_win64\build\share\julia\test\testdefs.jl:21
   [17] (::Distributed.var"#106#108"{Distributed.CallMsg{:call_fetch}})()
      @ Distributed C:\buildbot\worker\package_win64\build\usr\share\julia\stdlib\v1.6\Distributed\src\process_messages.jl:278
   [18] run_work_thunk(thunk::Distributed.var"#106#108"{Distributed.CallMsg{:call_fetch}}, print_error::Bool)
      @ Distributed C:\buildbot\worker\package_win64\build\usr\share\julia\stdlib\v1.6\Distributed\src\process_messages.jl:63
   [19] macro expansion
      @ C:\buildbot\worker\package_win64\build\usr\share\julia\stdlib\v1.6\Distributed\src\process_messages.jl:278 [inlined]
   [20] (::Distributed.var"#105#107"{Distributed.CallMsg{:call_fetch}, Distributed.MsgHeader, Sockets.TCPSocket})()
      @ Distributed .\task.jl:395