Added `accepts` attribute to `UnexpectedToken` and update stubs

lark-stubs/exceptions.pyi

@@ -1,6 +1,6 @@
 # -*- coding: utf-8 -*-
 
-from typing import Dict, Iterable, Callable, Union, TypeVar, Tuple
+from typing import Dict, Iterable, Callable, Union, TypeVar, Tuple, Any, List, Set
 from .tree import Tree
 from .lexer import Token
 
@@ -25,7 +25,10 @@ T = TypeVar('T')
 
 
 class UnexpectedInput(LarkError):
+    line: int
+    column: int
     pos_in_stream: int
+    state: Any
 
     def get_context(self, text: str, span: int = ...):
         ...
@@ -41,12 +44,14 @@ class UnexpectedInput(LarkError):
 
 
 class UnexpectedToken(ParseError, UnexpectedInput):
-    pass
-
+    expected: List[str]
+    considered_rules: Set[str]
+    puppet: Any
+    accepts: List[str]
 
 class UnexpectedCharacters(LexError, UnexpectedInput):
-    line: int
-    column: int
+    allowed: Set[str]
+    considered_tokens: Set[Any]
 
 
 class VisitError(LarkError):

lark/exceptions.py

@@ -105,7 +105,7 @@ class UnexpectedCharacters(LexError, UnexpectedInput):
 
 
 class UnexpectedToken(ParseError, UnexpectedInput):
-    def __init__(self, token, expected, considered_rules=None, state=None, puppet=None):
+    def __init__(self, token, expected, considered_rules=None, state=None, puppet=None, accepts=None):
         self.token = token
         self.expected = expected     # XXX str shouldn't necessary
         self.line = getattr(token, 'line', '?')
@@ -114,10 +114,11 @@ class UnexpectedToken(ParseError, UnexpectedInput):
         self.state = state
         self.pos_in_stream = getattr(token, 'pos_in_stream', None)
         self.puppet = puppet
+        self.accepts = accepts
 
         message = ("Unexpected token %r at line %s, column %s.\n"
                    "Expected one of: \n\t* %s\n"
-                   % (token, self.line, self.column, '\n\t* '.join(self.expected)))
+                   % (token, self.line, self.column, '\n\t* '.join(self.accepts or self.expected)))
 
         super(UnexpectedToken, self).__init__(message)
 

lark/parsers/lalr_parser.py

@@ -62,9 +62,18 @@ class _Parser:
                 expected = [s for s in states[state].keys() if s.isupper()]
                 try:
                     puppet = ParserPuppet(self, state_stack, value_stack, start, stream, set_state)
+                    accepts = []
+                    for t in expected:
+                        new_puppet = puppet.copy()
+                        try:
+                            new_puppet.feed_token(Token(t, ''))
+                        except KeyError:
+                            pass
+                        else:
+                            accepts.append(t)
                 except NameError:
-                    puppet = None
-                raise UnexpectedToken(token, expected, state=state, puppet=puppet)
+                    puppet = accepts = None
+                raise UnexpectedToken(token, expected, state=state, puppet=puppet, accepts=accepts)
 
         def reduce(rule):
             size = len(rule.expansion)