cholesky! does not modify MMatrix

[mipals]

I am fairly new to using StaticArrays, so I do not know if this is intended or not but it caught me by surprise as this is different behaviour when compared to the standard cholesky! functionality from LinearAlgebra. I believe the reason for this behaviour can be found in the following line

StaticArrays.jl/src/cholesky.jl

Line 11 in 609aa34

@inline LinearAlgebra._chol!(A::StaticMatrix, ::Type{UpperTriangular}) = (cholesky(A).U, 0)

which can be seen to return a new data.

MWE:

# Standard LinearAlgebra
S = Matrix(2.0I(3))
cholesky!(S)
S # S is changed

# StaticArrays
T = MMatrix{3,3,Float64,9}(2I(3))
cholesky!(T)
T # T has not changed