JuliaDiff / JuliaDiff/Diffractor.jl

Mutating in closure

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Dominant language
Julia
Stars
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Forks
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Description

julia> using Diffractor

julia> D(f, x) = Diffractor.PrimeDerivativeFwd(f)(x)
D (generic function with 1 method)

julia> D(1) do x
         f(y) = (x = x*y)
         D(f, 1)
         D(f, 1)
       end
ERROR: MethodError: no method matching apply_type(::Type{Diffractor.PrimeDerivativeFwd}, ::Int64, ::Type{var"#f#12"})
Stacktrace:
  [1] ∂☆nomethd(args::Any)
    @ Diffractor ~/.julia/dev/Diffractor/src/stage1/recurse_fwd.jl:115

Example from a ForwardDiff issue by Mike Innes: https://github.com/JuliaDiff/ForwardDiff.jl/issues/443

Contributor guide

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First steps

  1. Read the whole issue, then the project's contributing guide.
  2. Comment on the issue to say you are picking it up — it saves two people doing the same work.
  3. Fork the repository and make your change on a branch.
  4. Open a pull request that references the issue number.

Research direction

Start by reproducing the Julia example in the issue, then inspect src/stage1/recurse_fwd.jl around line 115, where the stack trace reports the failure. Trace how Diffractor handles the mutating closure and compare the behavior with the ForwardDiff issue linked in the report. Done means the example no longer raises the reported MethodError.

Written by the indexing model from the issue text.

Assessment

Tech stack
julia
Domain
compilers
Issue type
Bug
Difficulty
4/5
Estimated time
3-5 days
Activity status
Stale
Clarity
Needs clarification
Newbie friendliness
35/100

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