suboptimal abstract return type inference involving `getindex(::Tuple)`

[nsajko]

julia> f(t::Tuple, n::Bool) = t[10 + n]
f (generic function with 1 method)

julia> Core.Compiler.return_type(f, Tuple{Tuple{Bool,String,Vararg{Int}},Bool})
Union{Bool, Int64, String}

julia> versioninfo()
Julia Version 1.12.0-DEV.unknown
Commit 0fdd655 (2024-07-17 15:39 UTC)

Ideally, the inferred return type would be Int. Proof: the index 10 + n is always either 10 or 11, thus the index is always greater than two.

Context, hypothesized solution approach using refinement types: https://discourse.julialang.org/t/would-it-make-sense-for-julia-to-adopt-refinement-types/113586/10

[JeffBezanson]

Ok good point, but this is pretty greedy 😄

[bvdmitri]

Proof: the index 10 + n is always either 10 or 11

→ julia
               _
   _       _ _(_)_     |  Documentation: https://docs.julialang.org
  (_)     | (_) (_)    |
   _ _   _| |_  __ _   |  Type "?" for help, "]?" for Pkg help.
  | | | | | | |/ _` |  |
  | | |_| | | | (_| |  |  Version 1.11.3 (2025-01-21)
 _/ |\__'_|_|_|\__'_|  |  Official https://julialang.org/ release
|__/                   |

julia> Base.:(+)(a::Int, b::Bool) = 42

julia> 10 + true
42

(P.S. thats a joke)