calling convention error with `hvp` + type params

[penelopeysm]

mwe

using Enzyme: hvp

struct MyDist{T}
    μ::T
end
struct MyOtherDist{T}
    μ::T
end
f(::MyDist, x) = x
f(::MyOtherDist, x) = x

dist = MyDist([0.0])
function g(x)
    y = f(dist, x)
    return y[1] + dist.μ[1]
end
g([0.0])
hvp(g, [0.0], [-1.0])

#= 
ERROR: LoadError: LLVM error: broken gc calling conv fix
DestTy too big for Trunc
  %131 = trunc i1 %.sroa.48.0.i.i to i8, !dbg !112
=#

env

The above error is on Julia 1.11.

On Julia 1.12 it complains saying that it needs runtime activity enabled, although I think that looks like the same issue as #2854.

(jl) pkg> st
Status `~/jl/Project.toml`
  [7da242da] Enzyme v0.13.140

julia> versioninfo()
Julia Version 1.11.9
Commit 53a02c0720c (2026-02-06 00:27 UTC)
Build Info:
  Official https://julialang.org/ release
Platform Info:
  OS: macOS (arm64-apple-darwin24.0.0)
  CPU: 10 × Apple M1 Pro
  WORD_SIZE: 64
  LLVM: libLLVM-16.0.6 (ORCJIT, apple-m1)
Threads: 1 default, 0 interactive, 1 GC (on 8 virtual cores)

full error dump + stack trace

Julia 1.11: https://gist.github.com/penelopeysm/9779a40dec1d854ac3911eff1c050696#file-1p11-txt

Julia 1.12: https://gist.github.com/penelopeysm/9779a40dec1d854ac3911eff1c050696#file-1p12-txt

minimised from...

rsenne/ParallelMCMC.jl#25

[penelopeysm]

Sorry, pressed submit before I finished typing, added the info I wanted to add now :)