where-syntax accepts ; as separator in 0.6

[mauro3]

On 0.6 this works but shouldn't (note the ;):

julia> g(::T, ::Y) where {T;Y} = 1                   
g (generic function with 1 method)                   

julia> g(4,5)                                        
1                                                    

In 0.7 this errors as expected. Could this be back-ported to 0.6? This is a feature I plan to use in SimpleTraits.jl.

[StefanKarpinski]

How would one use the fact that it's a syntax error on 0.7? Are you asking to allow the semicolon on 0.7 or disallow it on 0.6?

[mauro3]

I think it's possible to allow to parse it but then throw an error later. This seems what's going on in 0.7:

julia> :(g(::T, ::Y) where {T;Y} = 1)                                                                                                                                                                              
:((g(::T, ::Y) where {T; Y}) = begin                                                                                                                                                                               
            #= REPL[2]:1 =#                                                                                                                                                                                        
            1                                                                                                                                                                                                      
        end)
                                                                                                                                                                                                                   
julia> g(::T, ::Y) where {T;Y} = 1                                                                                                                                                                                 
ERROR: syntax: invalid variable expression in "where"                                                                                                                                                              

That way the syntax can be used in macros.

[JeffBezanson]

This can't easily be backported since on 0.6 {a,b} and {a;b} parse the same.

[mauro3]

Ok, not to worry. I'll just have to drop 0.6 compatibility when moving to 0.7.

[StefanKarpinski]

That is what we will be encouraging all package maintainers to do once 0.7/1.0 is released.