Add debugging for issue erlang-ls#1288 (erlang-ls#1289)

apps/els_lsp/src/els_bound_var_in_pattern_diagnostics.erl

@@ -59,12 +59,22 @@ find_vars(Uri) ->
 find_vars_in_form(Form) ->
  case erl_syntax:type(Form) of
  function ->
- AnnotatedForm = erl_syntax_lib:annotate_bindings(Form, []),
- %% There are no bound variables in function heads or guards
- %% so lets descend straight into the bodies
- Clauses = erl_syntax:function_clauses(AnnotatedForm),
- ClauseBodies = lists:map(fun erl_syntax:clause_body/1, Clauses),
- fold_subtrees(ClauseBodies, []);
+ %% #1288: The try catch should allow us to understand the root cause
+ %% of the occasional crashes, which could be due to an incorrect mapping
+ %% between the erlfmt AST and erl_syntax AST
+ try
+ AnnotatedForm = erl_syntax_lib:annotate_bindings(Form, []),
+ %% There are no bound variables in function heads or guards
+ %% so lets descend straight into the bodies
+ Clauses = erl_syntax:function_clauses(AnnotatedForm),
+ ClauseBodies = lists:map(fun erl_syntax:clause_body/1, Clauses),
+ fold_subtrees(ClauseBodies, [])
+ catch C:E:St ->
+ ?LOG_ERROR("Error annotating bindings "
+ "[form=~p] [class=~p] [error=~p] [stacktrace=~p]",
+ [Form, C, E, St]),
+ []
+ end;
  _ ->
  []
  end.