"attempt to index a nil value" error during type check

[svermeulen]

When using branch generics-regressions from #911, and also using teal language server, I find the server crashes sometimes due to a nil reference exception happening deep in the guts of teal:

  │ Error in handler for request with method 'textDocument/didChange': 'tl.lua:6188: attempt to index a nil value
  │ stack traceback:
  │ 	tl.lua:6188: in function 'rollback_symbol_list_scope'
  │ 	tl.lua:8260: in function 'rollback_scope_transaction'
  │ 	tl.lua:9980: in function 'check_poly_call'
  │ 	tl.lua:10048: in function 'type_check_function_call'
  │ 	tl.lua:10129: in function 'check_metamethod'
  │ 	tl.lua:13136: in function 'cbkind_after'
  │ 	tl.lua:5104: in function 'recurse'
  │ 	tl.lua:4889: in function 'fn'
  │ 	tl.lua:5096: in function 'recurse'
  │ 	tl.lua:4900: in function 'fn'
  │ 	tl.lua:5096: in function 'recurse'
  │ 	...
  │ 	tl.lua:5096: in function 'recurse_node'
  │ 	tl.lua:13896: in function 'type_check'
  │ 	teal_language_server/document.lua:141: in function 'get_result'

I should note that I've made some very minor modifications to tl.lua (just adding a few globals) which puts the line numbers out of sync with the branch. In my version, tl.lua:6188 refers to line while symbol_list[symbol_list_n].name ~= "@{" do in function collector.rollback_symbol_list_scope = function()

I tried to find a small reproducible example outside of my codebase but wasn't successful on first attempt. I can try again though if the above isn't enough information.

[hishamhm]

Ah, thanks! This shouldn't be hard to fix