using LinearAlgebra
julia> A = I(2)
2×2 Diagonal{Bool, Vector{Bool}}:
1 ⋅
⋅ 1
julia> inv(A) # correct, diagonal matrix
2×2 Diagonal{Float64, Vector{Float64}}:
1.0 ⋅
⋅ 1.0
julia> inv(Symmetric(A)) # dense matrix?
2×2 Matrix{Float64}:
1.0 0.0
0.0 1.0
possible fix:
inv(A::Symmetric{<:Any, <:Diagonal}) = inv(A.data)
I'd be happy to open a PR if this seems reasonable.