regression in master: different return type and type instability in `count`

[matthias314]

In Julia 1.12.0, the return type of count is the type of init, if present:

julia> count(iszero, Int[]; init=Int8(0)) |> typeof
Int8

julia> count(iszero, Int[1]; init=Int8(0)) |> typeof
Int8

julia> count(Bool[]; init=Int8(0)) |> typeof
Int8

julia> count(Bool[1]; init=Int8(0)) |> typeof
Int8

For master this is not the case anymore. In particular, there is now a type instability:

julia> count(iszero, Int[]; init=Int8(0)) |> typeof
Int8

julia> count(iszero, Int[1]; init=Int8(0)) |> typeof
Int64

julia> count(Bool[]; init=Int8(0)) |> typeof
Int64

julia> count(Bool[1]; init=Int8(0)) |> typeof
Int64

Julia Version 1.13.0-DEV.1323
Commit c4f28781319 (2025-10-16 18:54 UTC)
Build Info:
  Official https://julialang.org release
Platform Info:
  OS: Linux (x86_64-linux-gnu)
  CPU: 4 × Intel(R) Core(TM) i3-10110U CPU @ 2.10GHz
  WORD_SIZE: 64
  LLVM: libLLVM-20.1.8 (ORCJIT, skylake)
  GC: Built with stock GC

[adienes]

almost definitely #58374

will it be fixed by #58241 ?