Epic: Deprecate nested slices

[vezenovm]

Handling for nested slices has already required a good amount of prep work but still has a few more tasks before it can be labelled fully complete.

The current status of nested slices is that a new pass has been introduced that fills nested slices with dummy data so that the internal types match up in size. The fill internal slices pass is necessary to get dynamic nested slices working in ACIR. This is the initial pass (#3258). However, this pass currently only works with one block and needs to be expanded to handle filling of dummy data in flattening. I have made this task list to better track what issues are leftover to complete.

#3187 is the initial work that prompted the fill internal slices pass.

Tasks

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1. feat(slices): Fill slice internal dummy data initial pass #3258
   +0
2. feat(acir): Handle dynamic array operations for nested slices #3187
   +0
3. SSA: Update merging slice values to handle nested slices #3188
   bug enhancement ssa +3
   
4. Enable using complex type inputs on dynamic slice intrinsics #3364
   E-MEDIUM P-HIGH acir-gen enhancement ssa +5
5. Enable dynamic index argument for slice insert and slice remove #2462
   E-MEDIUM P-HIGH acir-gen enhancement +4
   
6. Cannot access slice of slice in unconstrained environment #2909
   brillig bug ssa +3
   
7. Encountering "ERROR: ICE expected slice sizes" for slice members #3476
   bug +1
   
8. Slice of structs with slice members fails to be set coherently #3637
   bug +1

Ban nested slices tracker:

Tasks

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1. Ban nested slices #4017
   enhancement +1
   
2. Chore: Remove nested slice code #4019
   acir-gen enhancement ssa +3
   
3. Move BoundVec into the stdlib #4020
   enhancement +1

As per this comment this is a following task list of any remaining slice issues that need to be resolved to state that slices are fully stable:

Tasks

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1. Compiler panic when a slice is modified in multiple if statements. #4202
   bug +1
   
2. Sha512 cannot hash slices #3687
   bug +1
   
3. bug: non-numeric type variable Error #2540
   bug +1
   
4. Calling map on a slice panics #4220
   bug +1
   
5. The type [u32] cannot be represented in ACIR #2535
   bug +1
   

There is also issue #1344 for enabling printing of slices. This would be a more feature update and we might be able to tie into a general refactor of formatting strings in Noir.

[vezenovm]

After an internal meeting and the complexity introduced in #3979 we have decied to temporarily shelve nested slices. In the main issue a new tracklist has been created to mark their removal.

[kevaundray]

Once we merge the ban nested slices PR, can you check the bugs/issues/tasks that are related to slices to see if they are still relevant?

[vezenovm]

I will leave #528 to be closed once this issue is closed.

[vezenovm]

Closing this issue now that all tasks have been completed. Any new slice bugs can be separate from this issue.