type inference regression in 1.10.0-alpha1 when using `@propagate_inbounds`

[matthias314]

I've noticed this in real code, but here is a MWE:

struct A{T<:Tuple} t::T; end

Base.@propagate_inbounds f(x, i, ii...) = f(f(x, i), ii...)   
Base.@propagate_inbounds f(::Type{A{T}}, i) where T = T.parameters[i]

g(T...) = A{Tuple{T...}}

h(x::T) where T = g(f(T, 1), f(T, 2, 1))

a = A((1, A((2.0, 'x'))))
@code_typed h(a)

With 1.10.0-alpha I get

=> Type{A{var"#s173"}} where var"#s173"<:Tuple{Int64, Vararg}

With 1.9.2 it's

=> Type{A{Tuple{Int64, Float64}}}

Without @propagate_inbounds the inference works also for 1.10.0-alpha1.

My understanding is that Julia's type inference capabilities are not guaranteed. So maybe you think this is a bug, maybe not.

Julia Version 1.10.0-alpha1
Commit f8ad15f7b16 (2023-07-06 10:36 UTC)
Platform Info:
  OS: Linux (x86_64-linux-gnu)
  CPU: 24 × Intel(R) Xeon(R) CPU E5-2430 0 @ 2.20GHz
  WORD_SIZE: 64
  LIBM: libopenlibm
  LLVM: libLLVM-15.0.7 (ORCJIT, sandybridge)
  Threads: 1 on 24 virtual cores

[maleadt]

Bisected to #48684 (cc @aviatesk).