Unconsistent result when using sum or mean function on Complex{Int8} array

Description

julia> b = ones(Complex{Int8}, 100000) ;

julia> sum(b)
-96 + 0im

julia> mean(b)
-0.00096 + 0.0im

julia> a = ones(Int8, 100000) ;

julia> sum(a)
100000

julia> mean(a)
1.0

Contributor guide

Tech stack

None

Domain

data

Issue type

bug

DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.

3

Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.

half day

Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.

stale

ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.

clear

Prerequisites

Understanding integer overflowJulia's sum and mean functions

Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.

60

Research direction

Investigate the implementation of sum and mean for complex integer arrays in Julia's base library, likely in base/reduce.jl. Understand how type promotion is handled for Int8 and Complex{Int8} and propose a fix to ensure proper overflow prevention, similar to the scalar Int8 case mentioned in the issue.