231 lines
8.3 KiB
C
231 lines
8.3 KiB
C
#include "tree_sitter/parser/lr_parser.h"
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/*
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* Private
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*/
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static const ts_parse_action * actions_for_state(ts_lr_parser *parser, ts_state_id state) {
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return parser->config.parse_table + (state * parser->config.symbol_count);
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}
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void shift(ts_lr_parser *parser, ts_state_id parse_state) {
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ts_stack_push(&parser->stack, parse_state, parser->lookahead);
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parser->lookahead = parser->next_lookahead;
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parser->next_lookahead = NULL;
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}
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void reduce(ts_lr_parser *parser, ts_symbol symbol, size_t child_count) {
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parser->next_lookahead = parser->lookahead;
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parser->lookahead = ts_stack_reduce(&parser->stack,
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symbol,
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child_count,
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parser->config.hidden_symbol_flags,
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parser->config.ubiquitous_symbol_flags);
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}
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static size_t breakdown_stack(ts_lr_parser *parser, ts_input_edit *edit) {
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if (!edit) return 0;
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ts_stack *stack = &parser->stack;
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size_t position = 0;
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for (;;) {
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ts_tree *node = ts_stack_top_node(stack);
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if (!node) break;
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position = ts_stack_right_position(stack);
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size_t child_count;
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ts_tree **children = ts_tree_immediate_children(node, &child_count);
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if (position <= edit->position && !children) break;
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stack->size--;
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position -= ts_tree_total_size(node);
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for (size_t i = 0; i < child_count && position < edit->position; i++) {
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ts_tree *child = children[i];
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ts_state_id state = ts_stack_top_state(stack);
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ts_state_id next_state = actions_for_state(parser, state)[ts_tree_symbol(child)].data.to_state;
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ts_stack_push(stack, next_state, child);
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ts_tree_retain(child);
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position += ts_tree_total_size(child);
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}
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ts_tree_release(node);
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}
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return position;
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}
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ts_symbol * expected_symbols(ts_lr_parser *parser, size_t *count) {
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*count = 0;
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const ts_parse_action *actions = actions_for_state(parser, ts_stack_top_state(&parser->stack));
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for (size_t i = 0; i < parser->config.symbol_count; i++)
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if (actions[i].type != ts_parse_action_type_error)
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++(*count);
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size_t n = 0;
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ts_symbol *result = malloc(*count * sizeof(*result));
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for (ts_symbol i = 0; i < parser->config.symbol_count; i++)
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if (actions[i].type != ts_parse_action_type_error)
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result[n++] = i;
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return result;
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}
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int handle_error(ts_lr_parser *parser) {
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size_t count = 0;
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ts_tree *error = ts_tree_make_error(ts_lexer_lookahead_char(&parser->lexer),
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count,
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expected_symbols(parser, &count),
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0,
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0);
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for (;;) {
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ts_tree_release(parser->lookahead);
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size_t position = ts_lexer_position(&parser->lexer);
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parser->lookahead = parser->config.lex_fn(&parser->lexer, ts_lex_state_error);
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int at_end = 0;
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if (ts_lexer_position(&parser->lexer) == position)
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at_end = !ts_lexer_advance(&parser->lexer);
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if (at_end || ts_tree_symbol(parser->lookahead) == ts_builtin_sym_end) {
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ts_stack_push(&parser->stack, 0, error);
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return 0;
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}
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/*
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* Unwind the stack, looking for a state in which this token
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* may appear after an error.
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*/
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for (size_t j = 0; j < parser->stack.size; j++) {
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size_t i = parser->stack.size - 1 - j;
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ts_state_id stack_state = parser->stack.entries[i].state;
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ts_parse_action action_on_error = actions_for_state(parser, stack_state)[ts_builtin_sym_error];
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if (action_on_error.type == ts_parse_action_type_shift) {
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ts_state_id state_after_error = action_on_error.data.to_state;
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if (actions_for_state(parser, state_after_error)[ts_tree_symbol(parser->lookahead)].type != ts_parse_action_type_error) {
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ts_stack_shrink(&parser->stack, i + 1);
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ts_stack_push(&parser->stack, state_after_error, error);
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return 1;
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}
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}
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}
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}
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}
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ts_tree * get_tree_root(ts_lr_parser *parser) {
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ts_stack *stack = &parser->stack;
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ts_tree *top_node = ts_stack_top_node(stack);
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if (stack->size <= 1)
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return top_node;
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if (ts_tree_symbol(top_node) == ts_builtin_sym_error)
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return top_node;
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size_t immediate_child_count;
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ts_tree **immedate_children = ts_tree_immediate_children(top_node, &immediate_child_count);
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stack->size--;
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for (size_t i = 0; i < immediate_child_count; i++) {
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ts_tree *child = immedate_children[i];
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ts_tree_retain(child);
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ts_state_id state = ts_stack_top_state(stack);
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ts_state_id next_state = actions_for_state(parser, state)[ts_tree_symbol(child)].data.to_state;
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ts_stack_push(stack, next_state, child);
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}
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ts_tree *new_node = ts_stack_reduce(stack,
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ts_tree_symbol(top_node),
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stack->size,
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parser->config.hidden_symbol_flags,
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NULL);
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ts_tree_release(top_node);
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return new_node;
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}
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ts_parse_action get_next_action(ts_lr_parser *parser) {
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ts_state_id state = ts_stack_top_state(&parser->stack);
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if (!parser->lookahead)
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parser->lookahead = parser->config.lex_fn(&parser->lexer, parser->config.lex_states[state]);
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return actions_for_state(parser, state)[ts_tree_symbol(parser->lookahead)];
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}
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/*
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* Public API
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*/
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ts_lr_parser * ts_lr_parser_make(size_t symbol_count,
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const ts_parse_action *parse_table,
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const ts_state_id *lex_states,
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ts_tree * (* lex_fn)(ts_lexer *, ts_state_id),
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const int *hidden_symbol_flags,
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const int *ubiquitous_symbol_flags) {
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ts_lr_parser *result = malloc(sizeof(ts_lr_parser));
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*result = (ts_lr_parser) {
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.lexer = ts_lexer_make(),
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.stack = ts_stack_make(),
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.config = {
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.symbol_count = symbol_count,
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.parse_table = parse_table,
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.lex_states = lex_states,
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.lex_fn = lex_fn,
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.hidden_symbol_flags = hidden_symbol_flags,
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.ubiquitous_symbol_flags = ubiquitous_symbol_flags,
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},
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};
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return result;
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}
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void ts_lr_parser_free(void *data) {
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ts_lr_parser *parser = (ts_lr_parser *)data;
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if (parser->lookahead) ts_tree_release(parser->lookahead);
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if (parser->next_lookahead) ts_tree_release(parser->next_lookahead);
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ts_stack_delete(&parser->stack);
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free(parser);
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}
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void ts_lr_parser_initialize(ts_lr_parser *parser, ts_input input, ts_input_edit *edit) {
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if (!edit) ts_stack_shrink(&parser->stack, 0);
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parser->lookahead = NULL;
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parser->next_lookahead = NULL;
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size_t position = breakdown_stack(parser, edit);
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input.seek_fn(input.data, position);
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parser->lexer = ts_lexer_make();
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parser->lexer.input = input;
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ts_lexer_advance(&parser->lexer);
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}
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#ifdef TS_DEBUG_PARSE
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#include <stdio.h>
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#define DEBUG_PARSE(...) fprintf(stderr, "\n" __VA_ARGS__)
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#else
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#define DEBUG_PARSE(...)
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#endif
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ts_tree * ts_lr_parser_parse(ts_lr_parser *parser, const char **symbol_names) {
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ts_parse_action action = get_next_action(parser);
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DEBUG_PARSE("LOOKAHEAD %s", symbol_names[ts_tree_symbol(parser->lookahead)]);
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switch (action.type) {
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case ts_parse_action_type_shift:
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DEBUG_PARSE("SHIFT %d", action.data.to_state);
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shift(parser, action.data.to_state);
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return NULL;
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case ts_parse_action_type_reduce:
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DEBUG_PARSE("REDUCE %s %d", symbol_names[action.data.symbol], action.data.child_count);
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reduce(parser, action.data.symbol, action.data.child_count);
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return NULL;
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case ts_parse_action_type_accept:
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DEBUG_PARSE("ACCEPT");
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return get_tree_root(parser);
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case ts_parse_action_type_error:
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DEBUG_PARSE("ERROR");
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if (handle_error(parser))
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return NULL;
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else
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return get_tree_root(parser);
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default:
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return NULL;
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}
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}
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