[julia-users] Re: Problems knowing when a promote_rule exists, and

['Bill Hart' via julia-users]

So here is an example of how broken this is. I have the following code:

      println(par_type, " ", T2, " ", Base.promote_rule(par_type, T2), " ", 
Base.promote_rule(par_type, T2) != par_type)
      if Base.promote_rule(par_type, T2) != par_type
         eval(:(Base.promote_rule(::Type{$par_type}, ::Type{$T2}) = 
$par_type))
      end


So it's supposed to check if the promote_rule already returns its first 
argument and omit defining the promote_rule if it does.

Here is what it prints:

Nemo.Poly{Nemo.fmpz_poly} Nemo.fmpz Union{} true
WARNING: Method definition promote_rule(Type{Nemo.Poly{Nemo.fmpz_poly}}, 
Type{Nemo.fmpz}) in module Nemo at 
/home/wbhart/.julia/v0.5/Nemo/src/generic/Poly.jl:1754 overwritten at 
/home/wbhart/.julia/v0.5/Nemo/src/generic/Poly.jl:1754.

In other words, it tells me that the promote_rule does not exist, so goes 
ahead and creates it, and then tells me that it already exists.

This is clearly totally broken. I strongly suspect this is a bug related to 
the equality problem I outlined in the first post.

Bill.