non-boolean Missing found in boolean context (1/2 union split): goto %44 if not _4::Union{Missing, Bool}

[lgeissbauer-btig]

julia> function f()
           v = rand([["" => ""], nothing])
           println("$(v)")
       end
f (generic function with 1 method)

julia> JET.@report_call f()
═════ 2 possible errors found ═════
┌ @ REPL[22]:3 string(v)
│┌ @ strings/io.jl:185 Base.print_to_string(xs...)
││┌ @ strings/io.jl:144 print(s, x)
│││┌ @ strings/io.jl:35 show(io, x)
││││┌ @ arrayshow.jl:484 Base.show_vector(io, X)
│││││┌ @ arrayshow.jl:513 #self#(io, v, [, ])
││││││┌ @ arrayshow.jl:513 Base.typeinfo_prefix(io, v)
│││││││┌ @ arrayshow.jl:581 Base.typeinfo_implicit(eltype_X)
││││││││┌ @ arrayshow.jl:551 goto %44 if not _4
│││││││││ non-boolean `Missing` found in boolean context (1/2 union split): goto %44 if not _4::Union{Missing, Bool}
││││││││└────────────────────
│││││││┌ @ arrayshow.jl:581 goto %61 if not Base.typeinfo_implicit(eltype_X)
││││││││ non-boolean `Missing` found in boolean context (1/2 union split): goto %61 if not Base.typeinfo_implicit(eltype_X::Type{Pair{String, String}})::Union{Missing, Bool}
│││││││└────────────────────

[timholy]

Are you claiming this is a JET bug? (Without having looked at the code, the report seems plausible to me.) If not, wouldn't Julia itself be a better place to report this?

[timholy]

It might also be worth noting that not all JET reports require action. Take this one as an example: inference can't prove that some call doesn't return missing, and then gets used in a ::Bool-only context. But the "fix" would be to introduce an explicit error. The original code must look like this:

julia> x = missing
missing

julia> if x
           println("OK!")
       end
ERROR: TypeError: non-boolean (Missing) used in boolean context
Stacktrace:
 [1] top-level scope
   @ REPL[2]:1

and JET doesn't like the fact that x might be missing. The "fix" that would make JET happy is

julia> begin
           if !isa(x, Bool)
               error("x should be a Bool, got $x")
           end
           if x
               println("OK!")
           end
       end
ERROR: x should be a Bool, got missing
Stacktrace:
 [1] error(s::String)
   @ Base ./error.jl:35
 [2] top-level scope
   @ REPL[4]:3

But I think this is scarcely an improvement, so personally I would just ignore this report.

[timholy]

Since I don't think there's any action needed, let's close this.