two version of R2R are here HEAD master

1 files changed, 1354 insertions, 0 deletions

diff --git a/.venv/lib/python3.12/site-packages/lark/load_grammar.py b/.venv/lib/python3.12/site-packages/lark/load_grammar.py
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+++ b/.venv/lib/python3.12/site-packages/lark/load_grammar.py
@@ -0,0 +1,1354 @@
+"""Parses and creates Grammar objects"""
+import hashlib
+import os.path
+import sys
+from collections import namedtuple
+from copy import copy, deepcopy
+from io import open
+import pkgutil
+from ast import literal_eval
+from numbers import Integral
+
+from .utils import bfs, Py36, logger, classify_bool, is_id_continue, is_id_start, bfs_all_unique, small_factors
+from .lexer import Token, TerminalDef, PatternStr, PatternRE
+
+from .parse_tree_builder import ParseTreeBuilder
+from .parser_frontends import ParsingFrontend
+from .common import LexerConf, ParserConf
+from .grammar import RuleOptions, Rule, Terminal, NonTerminal, Symbol
+from .utils import classify, suppress, dedup_list, Str
+from .exceptions import GrammarError, UnexpectedCharacters, UnexpectedToken, ParseError
+
+from .tree import Tree, SlottedTree as ST
+from .visitors import Transformer, Visitor, v_args, Transformer_InPlace, Transformer_NonRecursive
+inline_args = v_args(inline=True)
+
+__path__ = os.path.dirname(__file__)
+IMPORT_PATHS = ['grammars']
+
+EXT = '.lark'
+
+_RE_FLAGS = 'imslux'
+
+_EMPTY = Symbol('__empty__')
+
+_TERMINAL_NAMES = {
+    '.' : 'DOT',
+    ',' : 'COMMA',
+    ':' : 'COLON',
+    ';' : 'SEMICOLON',
+    '+' : 'PLUS',
+    '-' : 'MINUS',
+    '*' : 'STAR',
+    '/' : 'SLASH',
+    '\\' : 'BACKSLASH',
+    '|' : 'VBAR',
+    '?' : 'QMARK',
+    '!' : 'BANG',
+    '@' : 'AT',
+    '#' : 'HASH',
+    '$' : 'DOLLAR',
+    '%' : 'PERCENT',
+    '^' : 'CIRCUMFLEX',
+    '&' : 'AMPERSAND',
+    '_' : 'UNDERSCORE',
+    '<' : 'LESSTHAN',
+    '>' : 'MORETHAN',
+    '=' : 'EQUAL',
+    '"' : 'DBLQUOTE',
+    '\'' : 'QUOTE',
+    '`' : 'BACKQUOTE',
+    '~' : 'TILDE',
+    '(' : 'LPAR',
+    ')' : 'RPAR',
+    '{' : 'LBRACE',
+    '}' : 'RBRACE',
+    '[' : 'LSQB',
+    ']' : 'RSQB',
+    '\n' : 'NEWLINE',
+    '\r\n' : 'CRLF',
+    '\t' : 'TAB',
+    ' ' : 'SPACE',
+}
+
+# Grammar Parser
+TERMINALS = {
+    '_LPAR': r'\(',
+    '_RPAR': r'\)',
+    '_LBRA': r'\[',
+    '_RBRA': r'\]',
+    '_LBRACE': r'\{',
+    '_RBRACE': r'\}',
+    'OP': '[+*]|[?](?![a-z])',
+    '_COLON': ':',
+    '_COMMA': ',',
+    '_OR': r'\|',
+    '_DOT': r'\.(?!\.)',
+    '_DOTDOT': r'\.\.',
+    'TILDE': '~',
+    'RULE': '!?[_?]?[a-z][_a-z0-9]*',
+    'TERMINAL': '_?[A-Z][_A-Z0-9]*',
+    'STRING': r'"(\\"|\\\\|[^"\n])*?"i?',
+    'REGEXP': r'/(?!/)(\\/|\\\\|[^/])*?/[%s]*' % _RE_FLAGS,
+    '_NL': r'(\r?\n)+\s*',
+    '_NL_OR': r'(\r?\n)+\s*\|',
+    'WS': r'[ \t]+',
+    'COMMENT': r'\s*//[^\n]*',
+    'BACKSLASH': r'\\[ ]*\n',
+    '_TO': '->',
+    '_IGNORE': r'%ignore',
+    '_OVERRIDE': r'%override',
+    '_DECLARE': r'%declare',
+    '_EXTEND': r'%extend',
+    '_IMPORT': r'%import',
+    'NUMBER': r'[+-]?\d+',
+}
+
+RULES = {
+    'start': ['_list'],
+    '_list':  ['_item', '_list _item'],
+    '_item':  ['rule', 'term', 'ignore', 'import', 'declare', 'override', 'extend', '_NL'],
+
+    'rule': ['RULE template_params _COLON expansions _NL',
+             'RULE template_params _DOT NUMBER _COLON expansions _NL'],
+    'template_params': ['_LBRACE _template_params _RBRACE',
+                        ''],
+    '_template_params': ['RULE',
+                         '_template_params _COMMA RULE'],
+    'expansions': ['_expansions'],
+    '_expansions': ['alias',
+                    '_expansions _OR alias',
+                    '_expansions _NL_OR alias'],
+
+    '?alias':     ['expansion _TO RULE', 'expansion'],
+    'expansion': ['_expansion'],
+
+    '_expansion': ['', '_expansion expr'],
+
+    '?expr': ['atom',
+              'atom OP',
+              'atom TILDE NUMBER',
+              'atom TILDE NUMBER _DOTDOT NUMBER',
+              ],
+
+    '?atom': ['_LPAR expansions _RPAR',
+              'maybe',
+              'value'],
+
+    'value': ['terminal',
+              'nonterminal',
+              'literal',
+              'range',
+              'template_usage'],
+
+    'terminal': ['TERMINAL'],
+    'nonterminal': ['RULE'],
+
+    '?name': ['RULE', 'TERMINAL'],
+
+    'maybe': ['_LBRA expansions _RBRA'],
+    'range': ['STRING _DOTDOT STRING'],
+
+    'template_usage': ['RULE _LBRACE _template_args _RBRACE'],
+    '_template_args': ['value',
+                       '_template_args _COMMA value'],
+
+    'term': ['TERMINAL _COLON expansions _NL',
+             'TERMINAL _DOT NUMBER _COLON expansions _NL'],
+    'override': ['_OVERRIDE rule',
+                 '_OVERRIDE term'],
+    'extend': ['_EXTEND rule',
+               '_EXTEND term'],
+    'ignore': ['_IGNORE expansions _NL'],
+    'declare': ['_DECLARE _declare_args _NL'],
+    'import': ['_IMPORT _import_path _NL',
+               '_IMPORT _import_path _LPAR name_list _RPAR _NL',
+               '_IMPORT _import_path _TO name _NL'],
+
+    '_import_path': ['import_lib', 'import_rel'],
+    'import_lib': ['_import_args'],
+    'import_rel': ['_DOT _import_args'],
+    '_import_args': ['name', '_import_args _DOT name'],
+
+    'name_list': ['_name_list'],
+    '_name_list': ['name', '_name_list _COMMA name'],
+
+    '_declare_args': ['name', '_declare_args name'],
+    'literal': ['REGEXP', 'STRING'],
+}
+
+
+# Value 5 keeps the number of states in the lalr parser somewhat minimal
+# It isn't optimal, but close to it. See PR #949
+SMALL_FACTOR_THRESHOLD = 5
+# The Threshold whether repeat via ~ are split up into different rules
+# 50 is chosen since it keeps the number of states low and therefore lalr analysis time low,
+# while not being to overaggressive and unnecessarily creating rules that might create shift/reduce conflicts.
+# (See PR #949)
+REPEAT_BREAK_THRESHOLD = 50
+
+
+@inline_args
+class EBNF_to_BNF(Transformer_InPlace):
+    def __init__(self):
+        self.new_rules = []
+        self.rules_cache = {}
+        self.prefix = 'anon'
+        self.i = 0
+        self.rule_options = None
+
+    def _name_rule(self, inner):
+        new_name = '__%s_%s_%d' % (self.prefix, inner, self.i)
+        self.i += 1
+        return new_name
+
+    def _add_rule(self, key, name, expansions):
+        t = NonTerminal(name)
+        self.new_rules.append((name, expansions, self.rule_options))
+        self.rules_cache[key] = t
+        return t
+
+    def _add_recurse_rule(self, type_, expr):
+        try:
+            return self.rules_cache[expr]
+        except KeyError:
+            new_name = self._name_rule(type_)
+            t = NonTerminal(new_name)
+            tree = ST('expansions', [
+                ST('expansion', [expr]),
+                ST('expansion', [t, expr])
+            ])
+            return self._add_rule(expr, new_name, tree)
+
+    def _add_repeat_rule(self, a, b, target, atom):
+        """Generate a rule that repeats target ``a`` times, and repeats atom ``b`` times.
+
+        When called recursively (into target), it repeats atom for x(n) times, where:
+            x(0) = 1
+            x(n) = a(n) * x(n-1) + b
+
+        Example rule when a=3, b=4:
+
+            new_rule: target target target atom atom atom atom
+
+        """
+        key = (a, b, target, atom)
+        try:
+            return self.rules_cache[key]
+        except KeyError:
+            new_name = self._name_rule('repeat_a%d_b%d' % (a, b))
+            tree = ST('expansions', [ST('expansion', [target] * a + [atom] * b)])
+            return self._add_rule(key, new_name, tree)
+
+    def _add_repeat_opt_rule(self, a, b, target, target_opt, atom):
+        """Creates a rule that matches atom 0 to (a*n+b)-1 times.
+
+        When target matches n times atom, and target_opt 0 to n-1 times target_opt,
+
+        First we generate target * i followed by target_opt, for i from 0 to a-1
+        These match 0 to n*a - 1 times atom
+
+        Then we generate target * a followed by atom * i, for i from 0 to b-1
+        These match n*a to n*a + b-1 times atom
+
+        The created rule will not have any shift/reduce conflicts so that it can be used with lalr
+
+        Example rule when a=3, b=4:
+
+            new_rule: target_opt
+                    | target target_opt
+                    | target target target_opt
+
+                    | target target target
+                    | target target target atom
+                    | target target target atom atom
+                    | target target target atom atom atom
+
+        """
+        key = (a, b, target, atom, "opt")
+        try:
+            return self.rules_cache[key]
+        except KeyError:
+            new_name = self._name_rule('repeat_a%d_b%d_opt' % (a, b))
+            tree = ST('expansions', [
+                ST('expansion', [target]*i + [target_opt]) for i in range(a)
+            ] + [
+                ST('expansion', [target]*a + [atom]*i) for i in range(b)
+            ])
+            return self._add_rule(key, new_name, tree)
+
+    def _generate_repeats(self, rule, mn, mx):
+        """Generates a rule tree that repeats ``rule`` exactly between ``mn`` to ``mx`` times.
+        """
+        # For a small number of repeats, we can take the naive approach
+        if mx < REPEAT_BREAK_THRESHOLD:
+            return ST('expansions', [ST('expansion', [rule] * n) for n in range(mn, mx + 1)])
+
+        # For large repeat values, we break the repetition into sub-rules. 
+        # We treat ``rule~mn..mx`` as ``rule~mn rule~0..(diff=mx-mn)``.
+        # We then use small_factors to split up mn and diff up into values [(a, b), ...]
+        # This values are used with the help of _add_repeat_rule and _add_repeat_rule_opt
+        # to generate a complete rule/expression that matches the corresponding number of repeats
+        mn_target = rule
+        for a, b in small_factors(mn, SMALL_FACTOR_THRESHOLD):
+            mn_target = self._add_repeat_rule(a, b, mn_target, rule)
+        if mx == mn:
+            return mn_target
+
+        diff = mx - mn + 1  # We add one because _add_repeat_opt_rule generates rules that match one less
+        diff_factors = small_factors(diff, SMALL_FACTOR_THRESHOLD)
+        diff_target = rule  # Match rule 1 times
+        diff_opt_target = ST('expansion', [])  # match rule 0 times (e.g. up to 1 -1 times)
+        for a, b in diff_factors[:-1]:
+            diff_opt_target = self._add_repeat_opt_rule(a, b, diff_target, diff_opt_target, rule)
+            diff_target = self._add_repeat_rule(a, b, diff_target, rule)
+
+        a, b = diff_factors[-1]
+        diff_opt_target = self._add_repeat_opt_rule(a, b, diff_target, diff_opt_target, rule)
+
+        return ST('expansions', [ST('expansion', [mn_target] + [diff_opt_target])])
+
+    def expr(self, rule, op, *args):
+        if op.value == '?':
+            empty = ST('expansion', [])
+            return ST('expansions', [rule, empty])
+        elif op.value == '+':
+            # a : b c+ d
+            #   -->
+            # a : b _c d
+            # _c : _c c | c;
+            return self._add_recurse_rule('plus', rule)
+        elif op.value == '*':
+            # a : b c* d
+            #   -->
+            # a : b _c? d
+            # _c : _c c | c;
+            new_name = self._add_recurse_rule('star', rule)
+            return ST('expansions', [new_name, ST('expansion', [])])
+        elif op.value == '~':
+            if len(args) == 1:
+                mn = mx = int(args[0])
+            else:
+                mn, mx = map(int, args)
+                if mx < mn or mn < 0:
+                    raise GrammarError("Bad Range for %s (%d..%d isn't allowed)" % (rule, mn, mx))
+
+            return self._generate_repeats(rule, mn, mx)
+
+        assert False, op
+
+    def maybe(self, rule):
+        keep_all_tokens = self.rule_options and self.rule_options.keep_all_tokens
+
+        def will_not_get_removed(sym):
+            if isinstance(sym, NonTerminal):
+                return not sym.name.startswith('_')
+            if isinstance(sym, Terminal):
+                return keep_all_tokens or not sym.filter_out
+            assert False
+
+        if any(rule.scan_values(will_not_get_removed)):
+            empty = _EMPTY
+        else:
+            empty = ST('expansion', [])
+
+        return ST('expansions', [rule, empty])
+
+
+class SimplifyRule_Visitor(Visitor):
+
+    @staticmethod
+    def _flatten(tree):
+        while tree.expand_kids_by_data(tree.data):
+            pass
+
+    def expansion(self, tree):
+        # rules_list unpacking
+        # a : b (c|d) e
+        #  -->
+        # a : b c e | b d e
+        #
+        # In AST terms:
+        # expansion(b, expansions(c, d), e)
+        #   -->
+        # expansions( expansion(b, c, e), expansion(b, d, e) )
+
+        self._flatten(tree)
+
+        for i, child in enumerate(tree.children):
+            if isinstance(child, Tree) and child.data == 'expansions':
+                tree.data = 'expansions'
+                tree.children = [self.visit(ST('expansion', [option if i == j else other
+                                                             for j, other in enumerate(tree.children)]))
+                                 for option in dedup_list(child.children)]
+                self._flatten(tree)
+                break
+
+    def alias(self, tree):
+        rule, alias_name = tree.children
+        if rule.data == 'expansions':
+            aliases = []
+            for child in tree.children[0].children:
+                aliases.append(ST('alias', [child, alias_name]))
+            tree.data = 'expansions'
+            tree.children = aliases
+
+    def expansions(self, tree):
+        self._flatten(tree)
+        # Ensure all children are unique
+        if len(set(tree.children)) != len(tree.children):
+            tree.children = dedup_list(tree.children)   # dedup is expensive, so try to minimize its use
+
+
+class RuleTreeToText(Transformer):
+    def expansions(self, x):
+        return x
+
+    def expansion(self, symbols):
+        return symbols, None
+
+    def alias(self, x):
+        (expansion, _alias), alias = x
+        assert _alias is None, (alias, expansion, '-', _alias)  # Double alias not allowed
+        return expansion, alias.value
+
+
+class PrepareAnonTerminals(Transformer_InPlace):
+    """Create a unique list of anonymous terminals. Attempt to give meaningful names to them when we add them"""
+
+    def __init__(self, terminals):
+        self.terminals = terminals
+        self.term_set = {td.name for td in self.terminals}
+        self.term_reverse = {td.pattern: td for td in terminals}
+        self.i = 0
+        self.rule_options = None
+
+    @inline_args
+    def pattern(self, p):
+        value = p.value
+        if p in self.term_reverse and p.flags != self.term_reverse[p].pattern.flags:
+            raise GrammarError(u'Conflicting flags for the same terminal: %s' % p)
+
+        term_name = None
+
+        if isinstance(p, PatternStr):
+            try:
+                # If already defined, use the user-defined terminal name
+                term_name = self.term_reverse[p].name
+            except KeyError:
+                # Try to assign an indicative anon-terminal name
+                try:
+                    term_name = _TERMINAL_NAMES[value]
+                except KeyError:
+                    if value and is_id_continue(value) and is_id_start(value[0]) and value.upper() not in self.term_set:
+                        term_name = value.upper()
+
+                if term_name in self.term_set:
+                    term_name = None
+
+        elif isinstance(p, PatternRE):
+            if p in self.term_reverse:  # Kind of a weird placement.name
+                term_name = self.term_reverse[p].name
+        else:
+            assert False, p
+
+        if term_name is None:
+            term_name = '__ANON_%d' % self.i
+            self.i += 1
+
+        if term_name not in self.term_set:
+            assert p not in self.term_reverse
+            self.term_set.add(term_name)
+            termdef = TerminalDef(term_name, p)
+            self.term_reverse[p] = termdef
+            self.terminals.append(termdef)
+
+        filter_out = False if self.rule_options and self.rule_options.keep_all_tokens else isinstance(p, PatternStr)
+
+        return Terminal(term_name, filter_out=filter_out)
+
+
+class _ReplaceSymbols(Transformer_InPlace):
+    """Helper for ApplyTemplates"""
+
+    def __init__(self):
+        self.names = {}
+
+    def value(self, c):
+        if len(c) == 1 and isinstance(c[0], Token) and c[0].value in self.names:
+            return self.names[c[0].value]
+        return self.__default__('value', c, None)
+
+    def template_usage(self, c):
+        if c[0] in self.names:
+            return self.__default__('template_usage', [self.names[c[0]].name] + c[1:], None)
+        return self.__default__('template_usage', c, None)
+
+
+class ApplyTemplates(Transformer_InPlace):
+    """Apply the templates, creating new rules that represent the used templates"""
+
+    def __init__(self, rule_defs):
+        self.rule_defs = rule_defs
+        self.replacer = _ReplaceSymbols()
+        self.created_templates = set()
+
+    def template_usage(self, c):
+        name = c[0]
+        args = c[1:]
+        result_name = "%s{%s}" % (name, ",".join(a.name for a in args))
+        if result_name not in self.created_templates:
+            self.created_templates.add(result_name)
+            (_n, params, tree, options) ,= (t for t in self.rule_defs if t[0] == name)
+            assert len(params) == len(args), args
+            result_tree = deepcopy(tree)
+            self.replacer.names = dict(zip(params, args))
+            self.replacer.transform(result_tree)
+            self.rule_defs.append((result_name, [], result_tree, deepcopy(options)))
+        return NonTerminal(result_name)
+
+
+def _rfind(s, choices):
+    return max(s.rfind(c) for c in choices)
+
+
+def eval_escaping(s):
+    w = ''
+    i = iter(s)
+    for n in i:
+        w += n
+        if n == '\\':
+            try:
+                n2 = next(i)
+            except StopIteration:
+                raise GrammarError("Literal ended unexpectedly (bad escaping): `%r`" % s)
+            if n2 == '\\':
+                w += '\\\\'
+            elif n2 not in 'Uuxnftr':
+                w += '\\'
+            w += n2
+    w = w.replace('\\"', '"').replace("'", "\\'")
+
+    to_eval = "u'''%s'''" % w
+    try:
+        s = literal_eval(to_eval)
+    except SyntaxError as e:
+        raise GrammarError(s, e)
+
+    return s
+
+
+def _literal_to_pattern(literal):
+    v = literal.value
+    flag_start = _rfind(v, '/"')+1
+    assert flag_start > 0
+    flags = v[flag_start:]
+    assert all(f in _RE_FLAGS for f in flags), flags
+
+    if literal.type == 'STRING' and '\n' in v:
+        raise GrammarError('You cannot put newlines in string literals')
+
+    if literal.type == 'REGEXP' and '\n' in v and 'x' not in flags:
+        raise GrammarError('You can only use newlines in regular expressions '
+                           'with the `x` (verbose) flag')
+
+    v = v[:flag_start]
+    assert v[0] == v[-1] and v[0] in '"/'
+    x = v[1:-1]
+
+    s = eval_escaping(x)
+
+    if s == "":
+        raise GrammarError("Empty terminals are not allowed (%s)" % literal)
+
+    if literal.type == 'STRING':
+        s = s.replace('\\\\', '\\')
+        return PatternStr(s, flags, raw=literal.value)
+    elif literal.type == 'REGEXP':
+        return PatternRE(s, flags, raw=literal.value)
+    else:
+        assert False, 'Invariant failed: literal.type not in ["STRING", "REGEXP"]'
+
+
+@inline_args
+class PrepareLiterals(Transformer_InPlace):
+    def literal(self, literal):
+        return ST('pattern', [_literal_to_pattern(literal)])
+
+    def range(self, start, end):
+        assert start.type == end.type == 'STRING'
+        start = start.value[1:-1]
+        end = end.value[1:-1]
+        assert len(eval_escaping(start)) == len(eval_escaping(end)) == 1
+        regexp = '[%s-%s]' % (start, end)
+        return ST('pattern', [PatternRE(regexp)])
+
+
+def _make_joined_pattern(regexp, flags_set):
+    # In Python 3.6, a new syntax for flags was introduced, that allows us to restrict the scope
+    # of flags to a specific regexp group. We are already using it in `lexer.Pattern._get_flags`
+    # However, for prior Python versions, we still need to use global flags, so we have to make sure
+    # that there are no flag collisions when we merge several terminals.
+    flags = ()
+    if not Py36:
+        if len(flags_set) > 1:
+            raise GrammarError("Lark doesn't support joining terminals with conflicting flags in python <3.6!")
+        elif len(flags_set) == 1:
+            flags ,= flags_set
+
+    return PatternRE(regexp, flags)
+
+class TerminalTreeToPattern(Transformer_NonRecursive):
+    def pattern(self, ps):
+        p ,= ps
+        return p
+
+    def expansion(self, items):
+        assert items
+        if len(items) == 1:
+            return items[0]
+
+        pattern = ''.join(i.to_regexp() for i in items)
+        return _make_joined_pattern(pattern, {i.flags for i in items})
+
+    def expansions(self, exps):
+        if len(exps) == 1:
+            return exps[0]
+
+        # Do a bit of sorting to make sure that the longest option is returned
+        # (Python's re module otherwise prefers just 'l' when given (l|ll) and both could match)
+        exps.sort(key=lambda x: (-x.max_width, -x.min_width, -len(x.value)))
+
+        pattern = '(?:%s)' % ('|'.join(i.to_regexp() for i in exps))
+        return _make_joined_pattern(pattern, {i.flags for i in exps})
+
+    def expr(self, args):
+        inner, op = args[:2]
+        if op == '~':
+            if len(args) == 3:
+                op = "{%d}" % int(args[2])
+            else:
+                mn, mx = map(int, args[2:])
+                if mx < mn:
+                    raise GrammarError("Bad Range for %s (%d..%d isn't allowed)" % (inner, mn, mx))
+                op = "{%d,%d}" % (mn, mx)
+        else:
+            assert len(args) == 2
+        return PatternRE('(?:%s)%s' % (inner.to_regexp(), op), inner.flags)
+
+    def maybe(self, expr):
+        return self.expr(expr + ['?'])
+
+    def alias(self, t):
+        raise GrammarError("Aliasing not allowed in terminals (You used -> in the wrong place)")
+
+    def value(self, v):
+        return v[0]
+
+
+class PrepareSymbols(Transformer_InPlace):
+    def value(self, v):
+        v ,= v
+        if isinstance(v, Tree):
+            return v
+        elif v.type == 'RULE':
+            return NonTerminal(Str(v.value))
+        elif v.type == 'TERMINAL':
+            return Terminal(Str(v.value), filter_out=v.startswith('_'))
+        assert False
+
+
+def nr_deepcopy_tree(t):
+    """Deepcopy tree `t` without recursion"""
+    return Transformer_NonRecursive(False).transform(t)
+
+
+class Grammar:
+    def __init__(self, rule_defs, term_defs, ignore):
+        self.term_defs = term_defs
+        self.rule_defs = rule_defs
+        self.ignore = ignore
+
+    def compile(self, start, terminals_to_keep):
+        # We change the trees in-place (to support huge grammars)
+        # So deepcopy allows calling compile more than once.
+        term_defs = [(n, (nr_deepcopy_tree(t), p)) for n, (t, p) in self.term_defs]
+        rule_defs = [(n, p, nr_deepcopy_tree(t), o) for n, p, t, o in self.rule_defs]
+
+        # ===================
+        #  Compile Terminals
+        # ===================
+
+        # Convert terminal-trees to strings/regexps
+
+        for name, (term_tree, priority) in term_defs:
+            if term_tree is None:  # Terminal added through %declare
+                continue
+            expansions = list(term_tree.find_data('expansion'))
+            if len(expansions) == 1 and not expansions[0].children:
+                raise GrammarError("Terminals cannot be empty (%s)" % name)
+
+        transformer = PrepareLiterals() * TerminalTreeToPattern()
+        terminals = [TerminalDef(name, transformer.transform(term_tree), priority)
+                     for name, (term_tree, priority) in term_defs if term_tree]
+
+        # =================
+        #  Compile Rules
+        # =================
+
+        # 1. Pre-process terminals
+        anon_tokens_transf = PrepareAnonTerminals(terminals)
+        transformer = PrepareLiterals() * PrepareSymbols() * anon_tokens_transf  # Adds to terminals
+
+        # 2. Inline Templates
+
+        transformer *= ApplyTemplates(rule_defs)
+
+        # 3. Convert EBNF to BNF (and apply step 1 & 2)
+        ebnf_to_bnf = EBNF_to_BNF()
+        rules = []
+        i = 0
+        while i < len(rule_defs):  # We have to do it like this because rule_defs might grow due to templates
+            name, params, rule_tree, options = rule_defs[i]
+            i += 1
+            if len(params) != 0:  # Dont transform templates
+                continue
+            rule_options = RuleOptions(keep_all_tokens=True) if options and options.keep_all_tokens else None
+            ebnf_to_bnf.rule_options = rule_options
+            ebnf_to_bnf.prefix = name
+            anon_tokens_transf.rule_options = rule_options
+            tree = transformer.transform(rule_tree)
+            res = ebnf_to_bnf.transform(tree)
+            rules.append((name, res, options))
+        rules += ebnf_to_bnf.new_rules
+
+        assert len(rules) == len({name for name, _t, _o in rules}), "Whoops, name collision"
+
+        # 4. Compile tree to Rule objects
+        rule_tree_to_text = RuleTreeToText()
+
+        simplify_rule = SimplifyRule_Visitor()
+        compiled_rules = []
+        for rule_content in rules:
+            name, tree, options = rule_content
+            simplify_rule.visit(tree)
+            expansions = rule_tree_to_text.transform(tree)
+
+            for i, (expansion, alias) in enumerate(expansions):
+                if alias and name.startswith('_'):
+                    raise GrammarError("Rule %s is marked for expansion (it starts with an underscore) and isn't allowed to have aliases (alias=%s)"% (name, alias))
+
+                empty_indices = [x==_EMPTY for x in expansion]
+                if any(empty_indices):
+                    exp_options = copy(options) or RuleOptions()
+                    exp_options.empty_indices = empty_indices
+                    expansion = [x for x in expansion if x!=_EMPTY]
+                else:
+                    exp_options = options
+
+                for sym in expansion:
+                    assert isinstance(sym, Symbol)
+                    if sym.is_term and exp_options and exp_options.keep_all_tokens:
+                        sym.filter_out = False
+                rule = Rule(NonTerminal(name), expansion, i, alias, exp_options)
+                compiled_rules.append(rule)
+
+        # Remove duplicates of empty rules, throw error for non-empty duplicates
+        if len(set(compiled_rules)) != len(compiled_rules):
+            duplicates = classify(compiled_rules, lambda x: x)
+            for dups in duplicates.values():
+                if len(dups) > 1:
+                    if dups[0].expansion:
+                        raise GrammarError("Rules defined twice: %s\n\n(Might happen due to colliding expansion of optionals: [] or ?)"
+                                           % ''.join('\n  * %s' % i for i in dups))
+
+                    # Empty rule; assert all other attributes are equal
+                    assert len({(r.alias, r.order, r.options) for r in dups}) == len(dups)
+
+            # Remove duplicates
+            compiled_rules = list(set(compiled_rules))
+
+        # Filter out unused rules
+        while True:
+            c = len(compiled_rules)
+            used_rules = {s for r in compiled_rules
+                            for s in r.expansion
+                            if isinstance(s, NonTerminal)
+                            and s != r.origin}
+            used_rules |= {NonTerminal(s) for s in start}
+            compiled_rules, unused = classify_bool(compiled_rules, lambda r: r.origin in used_rules)
+            for r in unused:
+                logger.debug("Unused rule: %s", r)
+            if len(compiled_rules) == c:
+                break
+
+        # Filter out unused terminals
+        if terminals_to_keep != '*':
+            used_terms = {t.name for r in compiled_rules
+                                 for t in r.expansion
+                                 if isinstance(t, Terminal)}
+            terminals, unused = classify_bool(terminals, lambda t: t.name in used_terms or t.name in self.ignore or t.name in terminals_to_keep)
+            if unused:
+                logger.debug("Unused terminals: %s", [t.name for t in unused])
+
+        return terminals, compiled_rules, self.ignore
+
+
+PackageResource = namedtuple('PackageResource', 'pkg_name path')
+
+
+class FromPackageLoader(object):
+    """
+    Provides a simple way of creating custom import loaders that load from packages via ``pkgutil.get_data`` instead of using `open`.
+    This allows them to be compatible even from within zip files.
+
+    Relative imports are handled, so you can just freely use them.
+
+    pkg_name: The name of the package. You can probably provide `__name__` most of the time
+    search_paths: All the path that will be search on absolute imports.
+    """
+    def __init__(self, pkg_name, search_paths=("", )):
+        self.pkg_name = pkg_name
+        self.search_paths = search_paths
+
+    def __repr__(self):
+        return "%s(%r, %r)" % (type(self).__name__, self.pkg_name, self.search_paths)
+
+    def __call__(self, base_path, grammar_path):
+        if base_path is None:
+            to_try = self.search_paths
+        else:
+            # Check whether or not the importing grammar was loaded by this module.
+            if not isinstance(base_path, PackageResource) or base_path.pkg_name != self.pkg_name:
+                # Technically false, but FileNotFound doesn't exist in python2.7, and this message should never reach the end user anyway
+                raise IOError()
+            to_try = [base_path.path]
+        for path in to_try:
+            full_path = os.path.join(path, grammar_path)
+            try:
+                text = pkgutil.get_data(self.pkg_name, full_path)
+            except IOError:
+                continue
+            else:
+                return PackageResource(self.pkg_name, full_path), text.decode()
+        raise IOError()
+
+
+stdlib_loader = FromPackageLoader('lark', IMPORT_PATHS)
+
+
+
+def resolve_term_references(term_dict):
+    # TODO Solve with transitive closure (maybe)
+
+    while True:
+        changed = False
+        for name, token_tree in term_dict.items():
+            if token_tree is None:  # Terminal added through %declare
+                continue
+            for exp in token_tree.find_data('value'):
+                item ,= exp.children
+                if isinstance(item, Token):
+                    if item.type == 'RULE':
+                        raise GrammarError("Rules aren't allowed inside terminals (%s in %s)" % (item, name))
+                    if item.type == 'TERMINAL':
+                        try:
+                            term_value = term_dict[item]
+                        except KeyError:
+                            raise GrammarError("Terminal used but not defined: %s" % item)
+                        assert term_value is not None
+                        exp.children[0] = term_value
+                        changed = True
+        if not changed:
+            break
+
+    for name, term in term_dict.items():
+        if term:    # Not just declared
+            for child in term.children:
+                ids = [id(x) for x in child.iter_subtrees()]
+                if id(term) in ids:
+                    raise GrammarError("Recursion in terminal '%s' (recursion is only allowed in rules, not terminals)" % name)
+
+
+def options_from_rule(name, params, *x):
+    if len(x) > 1:
+        priority, expansions = x
+        priority = int(priority)
+    else:
+        expansions ,= x
+        priority = None
+    params = [t.value for t in params.children] if params is not None else []  # For the grammar parser
+
+    keep_all_tokens = name.startswith('!')
+    name = name.lstrip('!')
+    expand1 = name.startswith('?')
+    name = name.lstrip('?')
+
+    return name, params, expansions, RuleOptions(keep_all_tokens, expand1, priority=priority,
+                                                 template_source=(name if params else None))
+
+
+def symbols_from_strcase(expansion):
+    return [Terminal(x, filter_out=x.startswith('_')) if x.isupper() else NonTerminal(x) for x in expansion]
+
+
+@inline_args
+class PrepareGrammar(Transformer_InPlace):
+    def terminal(self, name):
+        return name
+
+    def nonterminal(self, name):
+        return name
+
+
+def _find_used_symbols(tree):
+    assert tree.data == 'expansions'
+    return {t for x in tree.find_data('expansion')
+              for t in x.scan_values(lambda t: t.type in ('RULE', 'TERMINAL'))}
+
+
+def _get_parser():
+    try:
+        return _get_parser.cache
+    except AttributeError:
+        terminals = [TerminalDef(name, PatternRE(value)) for name, value in TERMINALS.items()]
+
+        rules = [options_from_rule(name, None, x) for name, x in RULES.items()]
+        rules = [Rule(NonTerminal(r), symbols_from_strcase(x.split()), i, None, o)
+                 for r, _p, xs, o in rules for i, x in enumerate(xs)]
+        callback = ParseTreeBuilder(rules, ST).create_callback()
+        import re
+        lexer_conf = LexerConf(terminals, re, ['WS', 'COMMENT', 'BACKSLASH'])
+        parser_conf = ParserConf(rules, callback, ['start'])
+        lexer_conf.lexer_type = 'standard'
+        parser_conf.parser_type = 'lalr'
+        _get_parser.cache = ParsingFrontend(lexer_conf, parser_conf, None)
+        return _get_parser.cache
+
+GRAMMAR_ERRORS = [
+        ('Incorrect type of value', ['a: 1\n']),
+        ('Unclosed parenthesis', ['a: (\n']),
+        ('Unmatched closing parenthesis', ['a: )\n', 'a: [)\n', 'a: (]\n']),
+        ('Expecting rule or terminal definition (missing colon)', ['a\n', 'A\n', 'a->\n', 'A->\n', 'a A\n']),
+        ('Illegal name for rules or terminals', ['Aa:\n']),
+        ('Alias expects lowercase name', ['a: -> "a"\n']),
+        ('Unexpected colon', ['a::\n', 'a: b:\n', 'a: B:\n', 'a: "a":\n']),
+        ('Misplaced operator', ['a: b??', 'a: b(?)', 'a:+\n', 'a:?\n', 'a:*\n', 'a:|*\n']),
+        ('Expecting option ("|") or a new rule or terminal definition', ['a:a\n()\n']),
+        ('Terminal names cannot contain dots', ['A.B\n']),
+        ('Expecting rule or terminal definition', ['"a"\n']),
+        ('%import expects a name', ['%import "a"\n']),
+        ('%ignore expects a value', ['%ignore %import\n']),
+    ]
+
+def _translate_parser_exception(parse, e):
+        error = e.match_examples(parse, GRAMMAR_ERRORS, use_accepts=True)
+        if error:
+            return error
+        elif 'STRING' in e.expected:
+            return "Expecting a value"
+
+def _parse_grammar(text, name, start='start'):
+    try:
+        tree = _get_parser().parse(text + '\n', start)
+    except UnexpectedCharacters as e:
+        context = e.get_context(text)
+        raise GrammarError("Unexpected input at line %d column %d in %s: \n\n%s" %
+                           (e.line, e.column, name, context))
+    except UnexpectedToken as e:
+        context = e.get_context(text)
+        error = _translate_parser_exception(_get_parser().parse, e)
+        if error:
+            raise GrammarError("%s, at line %s column %s\n\n%s" % (error, e.line, e.column, context))
+        raise
+
+    return PrepareGrammar().transform(tree)
+
+
+def _error_repr(error):
+    if isinstance(error, UnexpectedToken):
+        error2 = _translate_parser_exception(_get_parser().parse, error)
+        if error2:
+            return error2
+        expected = ', '.join(error.accepts or error.expected)
+        return "Unexpected token %r. Expected one of: {%s}" % (str(error.token), expected)
+    else:
+        return str(error)
+
+def _search_interactive_parser(interactive_parser, predicate):
+    def expand(node):
+        path, p = node
+        for choice in p.choices():
+            t = Token(choice, '')
+            try:
+                new_p = p.feed_token(t)
+            except ParseError:    # Illegal
+                pass
+            else:
+                yield path + (choice,), new_p
+
+    for path, p in bfs_all_unique([((), interactive_parser)], expand):
+        if predicate(p):
+            return path, p
+
+def find_grammar_errors(text, start='start'):
+    errors = []
+    def on_error(e):
+        errors.append((e, _error_repr(e)))
+
+        # recover to a new line
+        token_path, _ = _search_interactive_parser(e.interactive_parser.as_immutable(), lambda p: '_NL' in p.choices())
+        for token_type in token_path:
+            e.interactive_parser.feed_token(Token(token_type, ''))
+        e.interactive_parser.feed_token(Token('_NL', '\n'))
+        return True
+
+    _tree = _get_parser().parse(text + '\n', start, on_error=on_error)
+
+    errors_by_line = classify(errors, lambda e: e[0].line)
+    errors = [el[0] for el in errors_by_line.values()]      # already sorted
+
+    for e in errors:
+        e[0].interactive_parser = None
+    return errors
+
+
+def _get_mangle(prefix, aliases, base_mangle=None):
+    def mangle(s):
+        if s in aliases:
+            s = aliases[s]
+        else:
+            if s[0] == '_':
+                s = '_%s__%s' % (prefix, s[1:])
+            else:
+                s = '%s__%s' % (prefix, s)
+        if base_mangle is not None:
+            s = base_mangle(s)
+        return s
+    return mangle
+
+def _mangle_exp(exp, mangle):
+    if mangle is None:
+        return exp
+    exp = deepcopy(exp) # TODO: is this needed
+    for t in exp.iter_subtrees():
+        for i, c in enumerate(t.children):
+            if isinstance(c, Token) and c.type in ('RULE', 'TERMINAL'):
+                t.children[i] = Token(c.type, mangle(c.value))
+    return exp
+
+
+
+class GrammarBuilder:
+    def __init__(self, global_keep_all_tokens=False, import_paths=None, used_files=None):
+        self.global_keep_all_tokens = global_keep_all_tokens
+        self.import_paths = import_paths or []
+        self.used_files = used_files or {}
+
+        self._definitions = {}
+        self._ignore_names = []
+
+    def _is_term(self, name):
+        # Imported terminals are of the form `Path__to__Grammar__file__TERMINAL_NAME`
+        # Only the last part is the actual name, and the rest might contain mixed case
+        return name.rpartition('__')[-1].isupper()
+
+    def _grammar_error(self, msg, *names):
+        args = {}
+        for i, name in enumerate(names, start=1):
+            postfix = '' if i == 1 else str(i)
+            args['name' + postfix] = name
+            args['type' + postfix] = lowercase_type = ("rule", "terminal")[self._is_term(name)]
+            args['Type' + postfix] = lowercase_type.title()
+        raise GrammarError(msg.format(**args))
+
+    def _check_options(self, name, options):
+        if self._is_term(name):
+            if options is None:
+                options = 1
+            # if we don't use Integral here, we run into python2.7/python3 problems with long vs int
+            elif not isinstance(options, Integral):
+                raise GrammarError("Terminal require a single int as 'options' (e.g. priority), got %s" % (type(options),))
+        else:
+            if options is None:
+                options = RuleOptions()
+            elif not isinstance(options, RuleOptions):
+                raise GrammarError("Rules require a RuleOptions instance as 'options'")
+            if self.global_keep_all_tokens:
+                options.keep_all_tokens = True
+        return options
+
+
+    def _define(self, name, exp, params=(), options=None, override=False):
+        if name in self._definitions:
+            if not override:
+                self._grammar_error("{Type} '{name}' defined more than once", name)
+        elif override:
+            self._grammar_error("Cannot override a nonexisting {type} {name}", name)
+
+        if name.startswith('__'):
+            self._grammar_error('Names starting with double-underscore are reserved (Error at {name})', name)
+
+        self._definitions[name] = (params, exp, self._check_options(name, options))
+
+    def _extend(self, name, exp, params=(), options=None):
+        if name not in self._definitions:
+            self._grammar_error("Can't extend {type} {name} as it wasn't defined before", name)
+        if tuple(params) != tuple(self._definitions[name][0]):
+            self._grammar_error("Cannot extend {type} with different parameters: {name}", name)
+        # TODO: think about what to do with 'options'
+        base = self._definitions[name][1]
+
+        assert isinstance(base, Tree) and base.data == 'expansions'
+        base.children.insert(0, exp)
+
+    def _ignore(self, exp_or_name):
+        if isinstance(exp_or_name, str):
+            self._ignore_names.append(exp_or_name)
+        else:
+            assert isinstance(exp_or_name, Tree)
+            t = exp_or_name
+            if t.data == 'expansions' and len(t.children) == 1:
+                t2 ,= t.children
+                if t2.data=='expansion' and len(t2.children) == 1:
+                    item ,= t2.children
+                    if item.data == 'value':
+                        item ,= item.children
+                        if isinstance(item, Token) and item.type == 'TERMINAL':
+                            self._ignore_names.append(item.value)
+                            return
+
+            name = '__IGNORE_%d'% len(self._ignore_names)
+            self._ignore_names.append(name)
+            self._definitions[name] = ((), t, 1)
+
+    def _declare(self, *names):
+        for name in names:
+            self._define(name, None)
+
+    def _unpack_import(self, stmt, grammar_name):
+        if len(stmt.children) > 1:
+            path_node, arg1 = stmt.children
+        else:
+            path_node, = stmt.children
+            arg1 = None
+
+        if isinstance(arg1, Tree):  # Multi import
+            dotted_path = tuple(path_node.children)
+            names = arg1.children
+            aliases = dict(zip(names, names))  # Can't have aliased multi import, so all aliases will be the same as names
+        else:  # Single import
+            dotted_path = tuple(path_node.children[:-1])
+            if not dotted_path:
+                name ,= path_node.children
+                raise GrammarError("Nothing was imported from grammar `%s`" % name)
+            name = path_node.children[-1]  # Get name from dotted path
+            aliases = {name.value: (arg1 or name).value}  # Aliases if exist
+
+        if path_node.data == 'import_lib':  # Import from library
+            base_path = None
+        else:  # Relative import
+            if grammar_name == '<string>':  # Import relative to script file path if grammar is coded in script
+                try:
+                    base_file = os.path.abspath(sys.modules['__main__'].__file__)
+                except AttributeError:
+                    base_file = None
+            else:
+                base_file = grammar_name  # Import relative to grammar file path if external grammar file
+            if base_file:
+                if isinstance(base_file, PackageResource):
+                    base_path = PackageResource(base_file.pkg_name, os.path.split(base_file.path)[0])
+                else:
+                    base_path = os.path.split(base_file)[0]
+            else:
+                base_path = os.path.abspath(os.path.curdir)
+
+        return dotted_path, base_path, aliases
+
+    def _unpack_definition(self, tree, mangle):
+        if tree.data == 'rule':
+            name, params, exp, opts = options_from_rule(*tree.children)
+        else:
+            name = tree.children[0].value
+            params = ()     # TODO terminal templates
+            opts = int(tree.children[1]) if len(tree.children) == 3 else 1 # priority
+            exp = tree.children[-1]
+
+        if mangle is not None:
+            params = tuple(mangle(p) for p in params)
+            name = mangle(name)
+
+        exp = _mangle_exp(exp, mangle)
+        return name, exp, params, opts
+
+
+    def load_grammar(self, grammar_text, grammar_name="<?>", mangle=None):
+        tree = _parse_grammar(grammar_text, grammar_name)
+
+        imports = {}
+        for stmt in tree.children:
+            if stmt.data == 'import':
+                dotted_path, base_path, aliases = self._unpack_import(stmt, grammar_name)
+                try:
+                    import_base_path, import_aliases = imports[dotted_path]
+                    assert base_path == import_base_path, 'Inconsistent base_path for %s.' % '.'.join(dotted_path)
+                    import_aliases.update(aliases)
+                except KeyError:
+                    imports[dotted_path] = base_path, aliases
+
+        for dotted_path, (base_path, aliases) in imports.items():
+            self.do_import(dotted_path, base_path, aliases, mangle)
+
+        for stmt in tree.children:
+            if stmt.data in ('term', 'rule'):
+                self._define(*self._unpack_definition(stmt, mangle))
+            elif stmt.data == 'override':
+                r ,= stmt.children
+                self._define(*self._unpack_definition(r, mangle), override=True)
+            elif stmt.data == 'extend':
+                r ,= stmt.children
+                self._extend(*self._unpack_definition(r, mangle))
+            elif stmt.data == 'ignore':
+                # if mangle is not None, we shouldn't apply ignore, since we aren't in a toplevel grammar
+                if mangle is None:
+                    self._ignore(*stmt.children)
+            elif stmt.data == 'declare':
+                names = [t.value for t in stmt.children]
+                if mangle is None:
+                    self._declare(*names)
+                else:
+                    self._declare(*map(mangle, names))
+            elif stmt.data == 'import':
+                pass
+            else:
+                assert False, stmt
+
+
+        term_defs = { name: exp
+            for name, (_params, exp, _options) in self._definitions.items()
+            if self._is_term(name)
+        }
+        resolve_term_references(term_defs)
+
+
+    def _remove_unused(self, used):
+        def rule_dependencies(symbol):
+            if self._is_term(symbol):
+                return []
+            try:
+                params, tree,_ = self._definitions[symbol]
+            except KeyError:
+                return []
+            return _find_used_symbols(tree) - set(params)
+
+        _used = set(bfs(used, rule_dependencies))
+        self._definitions = {k: v for k, v in self._definitions.items() if k in _used}
+
+
+    def do_import(self, dotted_path, base_path, aliases, base_mangle=None):
+        assert dotted_path
+        mangle = _get_mangle('__'.join(dotted_path), aliases, base_mangle)
+        grammar_path = os.path.join(*dotted_path) + EXT
+        to_try = self.import_paths + ([base_path] if base_path is not None else []) + [stdlib_loader]
+        for source in to_try:
+            try:
+                if callable(source):
+                    joined_path, text = source(base_path, grammar_path)
+                else:
+                    joined_path = os.path.join(source, grammar_path)
+                    with open(joined_path, encoding='utf8') as f:
+                        text = f.read()
+            except IOError:
+                continue
+            else:
+                h = hashlib.md5(text.encode('utf8')).hexdigest()
+                if self.used_files.get(joined_path, h) != h:
+                    raise RuntimeError("Grammar file was changed during importing")
+                self.used_files[joined_path] = h
+                    
+                gb = GrammarBuilder(self.global_keep_all_tokens, self.import_paths, self.used_files)
+                gb.load_grammar(text, joined_path, mangle)
+                gb._remove_unused(map(mangle, aliases))
+                for name in gb._definitions:
+                    if name in self._definitions:
+                        raise GrammarError("Cannot import '%s' from '%s': Symbol already defined." % (name, grammar_path))
+
+                self._definitions.update(**gb._definitions)
+                break
+        else:
+            # Search failed. Make Python throw a nice error.
+            open(grammar_path, encoding='utf8')
+            assert False, "Couldn't import grammar %s, but a corresponding file was found at a place where lark doesn't search for it" % (dotted_path,)
+
+
+    def validate(self):
+        for name, (params, exp, _options) in self._definitions.items():
+            for i, p in enumerate(params):
+                if p in self._definitions:
+                    raise GrammarError("Template Parameter conflicts with rule %s (in template %s)" % (p, name))
+                if p in params[:i]:
+                    raise GrammarError("Duplicate Template Parameter %s (in template %s)" % (p, name))
+
+            if exp is None: # Remaining checks don't apply to abstract rules/terminals
+                continue
+
+            for temp in exp.find_data('template_usage'):
+                sym = temp.children[0]
+                args = temp.children[1:]
+                if sym not in params:
+                    if sym not in self._definitions:
+                        self._grammar_error("Template '%s' used but not defined (in {type} {name})" % sym, name)
+                    if len(args) != len(self._definitions[sym][0]):
+                        expected, actual = len(self._definitions[sym][0]), len(args)
+                        self._grammar_error("Wrong number of template arguments used for {name} "
+                                            "(expected %s, got %s) (in {type2} {name2})" % (expected, actual), sym, name)
+
+            for sym in _find_used_symbols(exp):
+                if sym not in self._definitions and sym not in params:
+                    self._grammar_error("{Type} '{name}' used but not defined (in {type2} {name2})", sym, name)
+
+        if not set(self._definitions).issuperset(self._ignore_names):
+            raise GrammarError("Terminals %s were marked to ignore but were not defined!" % (set(self._ignore_names) - set(self._definitions)))
+
+    def build(self):
+        self.validate()
+        rule_defs = []
+        term_defs = []
+        for name, (params, exp, options) in self._definitions.items():
+            if self._is_term(name):
+                assert len(params) == 0
+                term_defs.append((name, (exp, options)))
+            else:
+                rule_defs.append((name, params, exp, options))
+        # resolve_term_references(term_defs)
+        return Grammar(rule_defs, term_defs, self._ignore_names)
+
+
+def verify_used_files(file_hashes):
+    for path, old in file_hashes.items():
+        text = None
+        if isinstance(path, str) and os.path.exists(path):
+            with open(path, encoding='utf8') as f:
+                text = f.read()
+        elif isinstance(path, PackageResource):
+            with suppress(IOError):
+                text = pkgutil.get_data(*path).decode('utf-8')
+        if text is None: # We don't know how to load the path. ignore it.
+            continue
+            
+        current = hashlib.md5(text.encode()).hexdigest()
+        if old != current:
+            logger.info("File %r changed, rebuilding Parser" % path)
+            return False
+    return True
+
+def list_grammar_imports(grammar, import_paths=[]):
+    "Returns a list of paths to the lark grammars imported by the given grammar (recursively)"
+    builder = GrammarBuilder(False, import_paths)
+    builder.load_grammar(grammar, '<string>')
+    return list(builder.used_files.keys())
+
+def load_grammar(grammar, source, import_paths, global_keep_all_tokens):
+    builder = GrammarBuilder(global_keep_all_tokens, import_paths)
+    builder.load_grammar(grammar, source)
+    return builder.build(), builder.used_files