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      1 """Fixer for it.next() -> next(it), per PEP 3114."""
      2 # Author: Collin Winter
      3 
      4 # Things that currently aren't covered:
      5 #   - listcomp "next" names aren't warned
      6 #   - "with" statement targets aren't checked
      7 
      8 # Local imports
      9 from ..pgen2 import token
     10 from ..pygram import python_symbols as syms
     11 from .. import fixer_base
     12 from ..fixer_util import Name, Call, find_binding
     13 
     14 bind_warning = "Calls to builtin next() possibly shadowed by global binding"
     15 
     16 
     17 class FixNext(fixer_base.BaseFix):
     18     BM_compatible = True
     19     PATTERN = """
     20     power< base=any+ trailer< '.' attr='next' > trailer< '(' ')' > >
     21     |
     22     power< head=any+ trailer< '.' attr='next' > not trailer< '(' ')' > >
     23     |
     24     classdef< 'class' any+ ':'
     25               suite< any*
     26                      funcdef< 'def'
     27                               name='next'
     28                               parameters< '(' NAME ')' > any+ >
     29                      any* > >
     30     |
     31     global=global_stmt< 'global' any* 'next' any* >
     32     """
     33 
     34     order = "pre" # Pre-order tree traversal
     35 
     36     def start_tree(self, tree, filename):
     37         super(FixNext, self).start_tree(tree, filename)
     38 
     39         n = find_binding(u'next', tree)
     40         if n:
     41             self.warning(n, bind_warning)
     42             self.shadowed_next = True
     43         else:
     44             self.shadowed_next = False
     45 
     46     def transform(self, node, results):
     47         assert results
     48 
     49         base = results.get("base")
     50         attr = results.get("attr")
     51         name = results.get("name")
     52 
     53         if base:
     54             if self.shadowed_next:
     55                 attr.replace(Name(u"__next__", prefix=attr.prefix))
     56             else:
     57                 base = [n.clone() for n in base]
     58                 base[0].prefix = u""
     59                 node.replace(Call(Name(u"next", prefix=node.prefix), base))
     60         elif name:
     61             n = Name(u"__next__", prefix=name.prefix)
     62             name.replace(n)
     63         elif attr:
     64             # We don't do this transformation if we're assigning to "x.next".
     65             # Unfortunately, it doesn't seem possible to do this in PATTERN,
     66             #  so it's being done here.
     67             if is_assign_target(node):
     68                 head = results["head"]
     69                 if "".join([str(n) for n in head]).strip() == u'__builtin__':
     70                     self.warning(node, bind_warning)
     71                 return
     72             attr.replace(Name(u"__next__"))
     73         elif "global" in results:
     74             self.warning(node, bind_warning)
     75             self.shadowed_next = True
     76 
     77 
     78 ### The following functions help test if node is part of an assignment
     79 ###  target.
     80 
     81 def is_assign_target(node):
     82     assign = find_assign(node)
     83     if assign is None:
     84         return False
     85 
     86     for child in assign.children:
     87         if child.type == token.EQUAL:
     88             return False
     89         elif is_subtree(child, node):
     90             return True
     91     return False
     92 
     93 def find_assign(node):
     94     if node.type == syms.expr_stmt:
     95         return node
     96     if node.type == syms.simple_stmt or node.parent is None:
     97         return None
     98     return find_assign(node.parent)
     99 
    100 def is_subtree(root, node):
    101     if root == node:
    102         return True
    103     return any(is_subtree(c, node) for c in root.children)
    104