Inference issue with CthulhuInterpreter vs NativeInterpreter

[willtebbutt]

I've identified a situation in which the CthulhuInterpreter and NativeInterpreter yield different results:

using Cthulhu

# Specify function + args.
fargs = (Base._mapreduce_dim, Base.Fix1(view, [5.0, 4.0]), vcat, Float64[], [1:1, 2:2], :)
tt = typeof(fargs)

# Construct the relevant interpreters.
native_interp = Core.Compiler.NativeInterpreter();
cthulhu_interp = Cthulhu.CthulhuInterpreter();

# Correctly infers `Vector{Float64}`
julia> Base.code_typed_by_type(tt; optimize=true, interp=native_interp)
1-element Vector{Any}:
 CodeInfo(
1 ─ %1 = %new(Base.MappingRF{Base.Fix1{typeof(view), Vector{Float64}}, Base.BottomRF{typeof(vcat)}}, f, $(QuoteNode(Base.BottomRF{typeof(vcat)}(vcat))))::Base.MappingRF{Base.Fix1{typeof(view), Vector{Float64}}, Base.BottomRF{typeof(vcat)}}
│   %2 = invoke Base._foldl_impl(%1::Base.MappingRF{Base.Fix1{typeof(view), Vector{Float64}}, Base.BottomRF{typeof(vcat)}}, nt::Vector{Float64}, A::Vector{UnitRange{Int64}})::Vector{Float64}
└──      return %2
) => Vector{Float64}

# Sadly, infers `AbstractVector`:
julia> Base.code_typed_by_type(tt; optimize=true, interp=cthulhu_interp)
1-element Vector{Any}:
 CodeInfo(
1 ─ %1 = Base.mapfoldl_impl(f, op, nt, A)::AbstractVector
└──      return %1
) => AbstractVector

Info for reproduction:

julia> versioninfo()
Julia Version 1.10.5
Commit 6f3fdf7b362 (2024-08-27 14:19 UTC)
Build Info:
  Official https://julialang.org/ release
Platform Info:
  OS: macOS (x86_64-apple-darwin22.4.0)
  CPU: 12 × Intel(R) Core(TM) i7-9750H CPU @ 2.60GHz
  WORD_SIZE: 64
  LIBM: libopenlibm
  LLVM: libLLVM-15.0.7 (ORCJIT, skylake)
Threads: 6 default, 0 interactive, 3 GC (on 12 virtual cores)
Environment:
  JULIA_NUM_THREADS = 6

julia> Pkg.status()
Status `/private/var/folders/z7/0fkyw8ms795b7znc_3vbvrsw0000gn/T/jl_9hQ5av/Project.toml`
  [f68482b8] Cthulhu v2.14.0

Note that this is also an issue for (soon-to-be-renamed) Tapir.jl . I'll be attempting to debug what's going on to cause this in Tapir.jl, and will let you know if I manage to figure out what's going on, but you might figure it out before me!

[simeonschaub]

Probably better tracked in JuliaLang/julia#55638?