Promote all values before constructing types?

[singularitti]

For example, in the following code:

e = EngineeringStrain([j == 1 ? 0.005 : 0 for j in 1:6]);

julia> eltype(e)
Real

e will have Real as its element type, not Float64. However, Real is not a bits type:

julia> isbitstype(Real)
false

which will cause the following error when setting indices:

julia> e[2] = 1
ERROR: setindex!() with non-isbitstype eltype is not supported by StaticArrays. Consider using SizedArray.
Stacktrace:
 [1] error(s::String)
   @ Base ./error.jl:35
 [2] setindex!
   @ ~/.julia/packages/StaticArrays/pTgFe/src/MArray.jl:39 [inlined]
 [3] setindex!(A::EngineeringStrain{Real}, v::Int64, i::Int64)
   @ LinearElasticityBase ~/.julia/dev/LinearElasticityBase/src/types.jl:79

So we must promote the element type before constructing any of EngineeringStrain, etc.

[singularitti]

We need to add promote in the following line.

[singularitti]

Similar issues: FluxML/Zygote.jl#686
JuliaArrays/StaticArrays.jl#799