fix #191: too restrictive typeassert for MixedDestabilizer

[Fe-r-oz]

This now works and all the test passes as well:

julia> random_destabilizer(5,6) |> stabilizerview |> MixedDestabilizer
𝒟ℯ𝓈𝓉𝒶𝒷━━
+ Z_____
+ _Z____
+ __Z___
+ ___Z__
+ _____X
𝒳ₗ━━━━━━
+ ZZZZX_
𝒮𝓉𝒶𝒷━━━━
+ XZ_ZZ_
- ZX__Z_
+ __YZZ_
+ Z_ZXZ_
+ _____Z
𝒵ₗ━━━━━━
+ ____Z_

The JET errors does not increase as well. Hopefully, this is plausible.

• The code is properly formatted and commented.
• Substantial new functionality is documented within the docs.
• All new functionality is tested.
• All of the automated tests on github pass.

[Fe-r-oz]

The PR is ready for review. Thank you!

P.S. My bad for the rebase. Initially, I had used : after 191 in commit message which didn't pushed the issue to appear in Development. However, I noticed simply using #issue can make the issue appear in Development. So, I did the rebase using reword to remove : in hash191: . But the issue still didn't appear in Development...

[Krastanov]

Could you elaborate why this is necessary? Maybe add tests that would have failed without this change?

[Krastanov]

The proper fix for this probably requires better parameterization of the input argument. The issue is that the following T is not what is preserved:

MixedDestabilizer(::Stabilizer{T}) where {T}

Rather what is preserved is the T in here:

MixedDestabilizer(::Stabilizer{Tableau{P, <:AbstractMatrix{T}}}) where {P, T}

Maybe we should define eltype for these guys.

eltype(::Stabilizer{Tableau{P, <:AbstractMatrix{T}}}) where {P, T} = T