fn remove_unit_reductions()

in cli/src/generate/build_tables/minimize_parse_table.rs [42:111]
66 lines of code
19 McCabe index (conditional complexity)

    fn remove_unit_reductions(&mut self) {
        let mut aliased_symbols = HashSet::new();
        for variable in &self.syntax_grammar.variables {
            for production in &variable.productions {
                for step in &production.steps {
                    if step.alias.is_some() {
                        aliased_symbols.insert(step.symbol);
                    }
                }
            }
        }

        let mut unit_reduction_symbols_by_state = HashMap::new();
        for (i, state) in self.parse_table.states.iter().enumerate() {
            let mut only_unit_reductions = true;
            let mut unit_reduction_symbol = None;
            for (_, entry) in &state.terminal_entries {
                for action in &entry.actions {
                    match action {
                        ParseAction::ShiftExtra => continue,
                        ParseAction::Reduce {
                            child_count: 1,
                            production_id: 0,
                            symbol,
                            ..
                        } => {
                            if !self.simple_aliases.contains_key(&symbol)
                                && !aliased_symbols.contains(&symbol)
                                && self.syntax_grammar.variables[symbol.index].kind
                                    != VariableType::Named
                                && (unit_reduction_symbol.is_none()
                                    || unit_reduction_symbol == Some(symbol))
                            {
                                unit_reduction_symbol = Some(symbol);
                                continue;
                            }
                        }
                        _ => {}
                    }
                    only_unit_reductions = false;
                    break;
                }

                if !only_unit_reductions {
                    break;
                }
            }

            if let Some(symbol) = unit_reduction_symbol {
                if only_unit_reductions {
                    unit_reduction_symbols_by_state.insert(i, *symbol);
                }
            }
        }

        for state in self.parse_table.states.iter_mut() {
            let mut done = false;
            while !done {
                done = true;
                state.update_referenced_states(|other_state_id, state| {
                    if let Some(symbol) = unit_reduction_symbols_by_state.get(&other_state_id) {
                        done = false;
                        state.nonterminal_entries[symbol]
                    } else {
                        other_state_id
                    }
                })
            }
        }
    }