subtypes function runs very slowly

[epatters]

The short version is this:

julia> @time subtypes(AbstractVector);
  0.136176 seconds (172.76 k allocations: 9.653 MiB)

julia> @time subtypes(AbstractVector);
  0.011419 seconds (6.24 k allocations: 879.953 KiB)

julia> import Catlab

julia> @time subtypes(AbstractVector);
 35.150647 seconds (1.54 M allocations: 126.430 MiB, 0.25% gc time)

julia> @time subtypes(AbstractVector);
  7.711600 seconds (169.09 k allocations: 16.685 MiB, 0.31% gc time)

julia> @time subtypes(AbstractVector);
  8.123479 seconds (169.09 k allocations: 16.685 MiB)

Context: The Documenter.jl builds for Catlab.jl and its dependers have been running very slowly for a while now. I finally tracked this down to the subtypes function, which Documenter calls once per Markdown element in the ExpandTemplates step. Issue JuliaDocs/Documenter.jl#1438 has been filed there (see also the older JuliaDocs/Documenter.jl#1261).

Unfortunately I cannot say what part of Catlab and/or Julia is responsible but I can point in the general direction. The problem arose during the development of data structures for C-sets, defined in the file CSetDataStructures.jl. This file makes heavy use of @generated methods for complex parameterized data types. My guess is that something related to that is causing the slowdown.