Julia: Array allocation happens before type checking

[mattBrzezinski]

Julia v1.3.0 on OSX v10.15.4

a = Array[]

append!(a, "foo")
> ERROR: MethodError: Cannot `convert` an object of type Char to an object of type String

push!(a, "bar")
> 4-element Array{String,1}:
 #undef  
 #undef  
 #undef  
    "bar"

[christopher-dG]

https://github.com/JuliaLang/julia/blob/d6d5208d66be637543232bec4b0c79b2811ea1c6/base/array.jl#L986-L994

resize! happens before any setindex! is attempted.

[KlausC]

Would that do what you expect?

append!(a, iter) = for i in iter; push!(a, i) end

[jakobnissen]

Duplicate of https://github.com/JuliaLang/julia/issues/15868 and https://github.com/JuliaLang/julia/issues/7642, ref https://github.com/JuliaLang/julia/pull/7671.

Yes, this is annoying behaviour, but checking whether each element can convert is unacceptably slow.

[mattBrzezinski]

Would that do what you expect?

append!(a, iter) = for i in iter; push!(a, i) end

Yes it would. I was mainly surprised that a failed operation grew the array, this behaviour was unexpected.

Duplicate of #15868 and #7642, ref #7671.

Yes, this is annoying behaviour, but checking whether each element can convert is unacceptably slow.

That's fair! I'm closing this issue in favour of #15868.