Add clone instances for arenas

[hendrikvanantwerpen]

No description provided.

[github-actions]

Performance Summary

Comparing base acb0fab with head 3cce544 on microsoft/TypeScript@v4.9.5. For details see workflow artifacts. Note that performance is tested on the last commits with changes in stack-graphs, not on every commit.

Before

--------------------------------------------------------------------------------
Command:            base/target/release/tree-sitter-stack-graphs-typescript index -D base.sqlite --max-file-time=30 --hide-error-details -- test/src/compiler
Massif arguments:   --massif-out-file=perf.out
ms_print arguments: --x=72 --y=12 base-perf-results/perf.out
--------------------------------------------------------------------------------


    GB
1.170^            ##                                                          
     |            #                                                           
     |            #                                                           
     |            #                                                           
     |            #                                                           
     |            #                                                     ::    
     |            #        :               :                            :     
     |            #      ::: :      ::     :           :                :     
     |            #      : : :::    :  :::::         : :                :     
     |      ::  ::#      : : ::     :  : : :         :::             ::::     
     |    @@:   : # :::: : : ::     :  : : : ::    :::::   :       ::: ::     
     |    @ : : : # :::  : : :: ::: :  : : :::  :::: ::::  :  :: : : : :: @:::
   0 +----------------------------------------------------------------------->Gi
     0                                                                   186.7

After

--------------------------------------------------------------------------------
Command:            head/target/release/tree-sitter-stack-graphs-typescript index -D head.sqlite --max-file-time=30 --hide-error-details -- test/src/compiler
Massif arguments:   --massif-out-file=perf.out
ms_print arguments: --x=72 --y=12 head-perf-results/perf.out
--------------------------------------------------------------------------------


    GB
1.206^            #                                                           
     |            #                                                           
     |            #                                                           
     |            #                                                           
     |            #                  ::                                  :    
     |           @#                  :                                   :    
     |           @#                  :                                @ ::    
     |           @#       ::         :    ::                         :@ ::    
     |           @#       :  :       :  @ :           :              :@ ::    
     |     : @   @#   :  ::  ::      :  @::         :::    ::        :@ ::    
     |     ::@   @#  ::  ::  ::      :  @::        ::::    :     @ : :@::::@  
     |     ::@   @#: ::  ::  ::   ::::  @::  :   : ::::  ::: : ::@ :::@::::@  
   0 +----------------------------------------------------------------------->Gi
     0                                                                   190.6

[hendrikvanantwerpen]

Local testing showed that this approach is not correct. It can result in double-free panics. I wonder if this has something to do with the way strings are interned (symbols hold a &str)? Perhaps this will only be possible if we use the hashing arena's of #223? For now, I'm making this a draft again.

[hendrikvanantwerpen]

Closing this old experiment, which was not the right approach. If we ever want this, we need to rethink how strings are interned---perhaps using a proper deduplicating arena like in #223.