Why does Tuple not have AbstractVector semantics?

Internals & Design
21

While I agree that making Tuple an abstract vector is probably misguided, the covariance of Tuples actually makes this easy to answer: T = typejoin(String, UInt, Char).

julia> Tuple{String, UInt, Char} <: NTuple{3, Base.typejoin(String, UInt, Char)}
true

The above typejoin happens to be Any, but that’s exactly what you also get when you use a vector as well.

julia> ["hi", UInt(1), 'c']
3-element Vector{Any}:
                   "hi"
 0x0000000000000001
                   'c': ASCII/Unicode U+0063 (category Ll: Letter, lowercase)

Though of course, NTuple{N, typejoin(...)} will disagree with Vector once you get into promotion, e.g.

julia> [1, 1.0-im]
2-element Vector{ComplexF64}:
 1.0 + 0.0im
 1.0 - 1.0im

julia> typejoin(Int, ComplexF64)
Number
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