Dump function fails for dicts of enums

[jakobnissen]

MWE:

julia> @enum Foo a b

julia> dump(Dict{Foo, Int}())
Dict{Foo, Int64}
  slots: Array{UInt8}((16,)) UInt8[0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00]
  keys: Array{Foo}((16,))
    1: Foo ERROR: KeyError: key 1742231696 not found

I can't tell if this can realistically be fixed or not. The issue is that the .keys field of the Dict is uninitialized, and thus contain invalid (and un-printable values).

One possible solution could be to wrap the show in dump in try-catch, but will that cause too undefined behaviour? What if the show method throws some other, unrelated error?

[vtjnash]

I think we should make this handled:

diff --git a/base/Enums.jl b/base/Enums.jl
index 06860402fb..de26dd4d77 100644
--- a/base/Enums.jl
+++ b/base/Enums.jl
@@ -23,7 +23,11 @@ Base.read(io::IO, ::Type{T}) where {T<:Enum} = T(read(io, basetype(T)))
 
 Base.isless(x::T, y::T) where {T<:Enum} = isless(basetype(T)(x), basetype(T)(y))
 
-Base.Symbol(x::Enum) = namemap(typeof(x))[Integer(x)]::Symbol
+function Base.Symbol(x::Enum)
+    names = namemap(typeof(x))
+    x = Integer(x)
+    return get(() -> Symbol("<invalid #$x>"), names, x)::Symbol
+end
 
 Base.print(io::IO, x::Enum) = print(io, Symbol(x))
 

julia> reinterpret(Foo, Int32(3))
<invalid #3>::Foo = 3

julia> dump(reinterpret(Foo, Int32(3)))
Foo Main.<invalid #3>

[JeffBezanson]

From triage: 👍 , but do the check in printing.