Anonymous arguments aren't handled properly

[torfjelde]

julia> using DynamicPPL

julia> @model f(::Val{ispredict} = Val(false)) where {ispredict} = ispredict ? 0 : 1
ERROR: syntax: invalid "::" syntax around REPL[4]:1
Stacktrace:
 [1] top-level scope
   @ REPL[4]:1

julia> @macroexpand @model f(::Val{ispredict} = Val(false)) where {ispredict} = ispredict ? 0 : 1
quote
    function f(__model__::Model, __varinfo__::AbstractVarInfo, __context__::AbstractPPL.AbstractContext, ::Val{ispredict}; ) where ispredict
        #= REPL[5]:1 =#
        begin
            #= REPL[5]:1 =#
            begin
                #= /home/tor/Projects/public/DynamicPPL.jl/src/compiler.jl:529 =#
                var"##retval#275" = if ispredict
                        0
                    else
                        1
                    end
                #= /home/tor/Projects/public/DynamicPPL.jl/src/compiler.jl:530 =#
                return (var"##retval#275", __varinfo__)
            end
        end
    end
    begin
        $(Expr(:meta, :doc))
        function f(::Val{ispredict} = Val(false); ) where ispredict
            #= REPL[5]:1 =#
            return (Model)(:f, f, NamedTuple{($(QuoteNode(:(::Val{ispredict}))),)}((::Val{ispredict},)), NamedTuple{($(QuoteNode(:(::Val{ispredict}))),)}((Val(false),)))
        end
    end
end

But works fine if we give it a "name":

julia> @macroexpand @model f(isval::Val{ispredict} = Val(false)) where {ispredict} = ispredict ? 0 : 1
quote
    function f(__model__::Model, __varinfo__::AbstractVarInfo, __context__::AbstractPPL.AbstractContext, isval::Val{ispredict}; ) where ispredict
        #= REPL[6]:1 =#
        begin
            #= REPL[6]:1 =#
            begin
                #= /home/tor/Projects/public/DynamicPPL.jl/src/compiler.jl:529 =#
                var"##retval#276" = if ispredict
                        0
                    else
                        1
                    end
                #= /home/tor/Projects/public/DynamicPPL.jl/src/compiler.jl:530 =#
                return (var"##retval#276", __varinfo__)
            end
        end
    end
    begin
        $(Expr(:meta, :doc))
        function f(isval::Val{ispredict} = Val(false); ) where ispredict
            #= REPL[6]:1 =#
            return (Model)(:f, f, NamedTuple{(:isval,)}((isval,)), NamedTuple{(:isval,)}((Val(false),)))
        end
    end
end

[devmotion]

This reminds me of JuliaLang/julia#42220 which AFAICT is only fixed in Julia 1.8. Do you get the same error with Julia 1.8 or master?

[torfjelde]

Not fixed on Julia 1.8.0-beta1 (haven't tried master yet).

[devmotion]

I guess the problem might be that we only handle ::Type{T} in a special way but not something like ::Val{T}...

[devmotion]

DynamicPPL.jl/src/compiler.jl

Line 265 in f2eb635

(::Type{T_}) | (name_::Type{T_}) => T

[devmotion]

#394