No method matching metadatatype(..., ::Type{Type})

[baggepinnen]

Not sure if this is my fault or not, but can't seem to figure out why I get this error. MWE below

struct Particles{T} <: Real
    particles::Vector{T}
end

p = Particles(randn(10))

Base.:(^)(p::Particles,r) = Particles(p.particles.^r)
Base.:(>)(p::Particles, r) = Particles(map(>, p.particles, r))

function negsquare(x)
    x > 0 ? x^2 : -x^2
end
Base.promote_rule(::Type{Particles{T}}, ::Type{T}) where T = Particles{T}
Base.convert(::Type{Particles{T}}, f::T) where T<:Real = Particles{T}(fill(f,10))

using Cassette, IRTools
import Cassette: tag, untag, enabletagging, metadatatype, metadata, @context, overdub, prehook, recurse
@context Ctx;
metadatatype(::Type{<:Ctx}, ::Type{Particles{T}}) where T<:Real = T
ctx = enabletagging(Ctx(), negsquare)
tagged = tag(p, ctx, 1.)
function overdub(ctx::Ctx, f::typeof(>), p::Particles, r)
    recurse(ctx, f, mean(p.particles),r)
end

julia> res = overdub(ctx, negsquare, tagged)
ERROR: MethodError: no method matching metadatatype(::Type{Cassette.Context{nametype(Ctx),Nothing,Cassette.Tag{nametype(Ctx),0x56926ddf0ee5f009,Nothing},getfield(Cassette, Symbol("##PassType#373")),IdDict{Module,Dict{Symbol,Cassette.BindingMeta}},Nothing}}, ::Type{Type})

[vchuravy]

Can you describe a bit more about what you want to achieve?

If I use the definition:

metadatatype(::Type{<:Ctx}, ::Type{P}) where {T, P<:Particles{T}} = T
metadatatype(::Type{<:Ctx}, ::Type{<:Type}) = Cassette.NoMetaData

I get further, but I also encounter:

julia> overdub(ctx, negsquare, tagged)
ERROR: TypeError: non-boolean (Particles{Bool}) used in boolean context
Stacktrace:
 [1] overdub(::Cassette.Context{nametype(Ctx),Nothing,Cassette.Tag{nametype(Ctx),0xa8104ee550fd8595,Nothing},getfield(Cassette, Symbol("##PassType#365")),IdDict{Module,Dict{Symbol,Cassette.BindingMeta}},Nothing}, ::typeof(negsquare), ::Cassette.Tagged{Cassette.Tag{nametype(Ctx),0xa8104ee550fd8595,Nothing},Particles{Float64},Float64,NamedTuple{(:particles,),Tuple{Cassette.Immutable{Cassette.Meta{Cassette.NoMetaData,Array{Cassette.Meta{Cassette.NoMetaData,Cassette.NoMetaMeta},1}}}}},Cassette.Context{nametype(Ctx),Nothing,Cassette.Tag{nametype(Ctx),0xa8104ee550fd8595,Nothing},getfield(Cassette, Symbol("##PassType#365")),IdDict{Module,Dict{Symbol,Cassette.BindingMeta}},Nothing}}) at /home/vchuravy/ctx.jl:11
 [2] top-level scope at none:0

[baggepinnen]

Currently I'm just exploring the potential of Cassette and am trying some primitive things. I was using the Juliacon 2018 seminar by Jarrett as a documentation for the tagging mechanism and didn't really get it to work.

The problem you ended up in was what I was trying to get around. The final goal is to modify branches in code to allow a n-vector of bool appearing in a boolean context to execute the branching code n times, one for each element of the vector. I have a long way to go before I'm competent enough to pull that off though, these are just my first few steps into the unknown.

It's unclear to me why my signalture in metadatatype did not work, and why I also have to define the method metadatatype(::Type{<:Ctx}, ::Type{<:Type}) = Cassette.NoMetaData

[vchuravy]

Yeah that seems odd and may be a subtyping bug. @jrevels any suggestions?

[jarredbarber]

To fix the Boolean context issue you have to write an @pass macro to statically transform the conditional branches. It's quite a bit more complicated than just writing an overdub call.