1 files changed, 104 insertions, 0 deletions
diff --git a/Lib/lib2to3/fixes/fix_next.py b/Lib/lib2to3/fixes/fix_next.py
new file mode 100644
index 0000000..adbc962
--- /dev/null
+++ b/Lib/lib2to3/fixes/fix_next.py
@@ -0,0 +1,104 @@
+"""Fixer for it.next() -> next(it), per PEP 3114."""
+# Author: Collin Winter
+
+# Things that currently aren't covered:
+#   - listcomp "next" names aren't warned
+#   - "with" statement targets aren't checked
+
+# Local imports
+from ..pgen2 import token
+from ..pygram import python_symbols as syms
+from . import basefix
+from .util import Name, Call, find_binding, any
+
+bind_warning = "Calls to builtin next() possibly shadowed by global binding"
+
+
+class FixNext(basefix.BaseFix):
+    PATTERN = """
+    power< base=any+ trailer< '.' attr='next' > trailer< '(' ')' > >
+    |
+    power< head=any+ trailer< '.' attr='next' > not trailer< '(' ')' > >
+    |
+    classdef< 'class' any+ ':'
+              suite< any*
+                     funcdef< 'def'
+                              name='next'
+                              parameters< '(' NAME ')' > any+ >
+                     any* > >
+    |
+    global=global_stmt< 'global' any* 'next' any* >
+    |
+    mod=file_input< any+ >
+    """
+
+    order = "pre" # Pre-order tree traversal
+
+    def start_tree(self, tree, filename):
+        super(FixNext, self).start_tree(tree, filename)
+        self.shadowed_next = False
+
+    def transform(self, node, results):
+        assert results
+
+        base = results.get("base")
+        attr = results.get("attr")
+        name = results.get("name")
+        mod = results.get("mod")
+
+        if base:
+          if self.shadowed_next:
+              attr.replace(Name("__next__", prefix=attr.get_prefix()))
+          else:
+              base = [n.clone() for n in base]
+              base[0].set_prefix("")
+              node.replace(Call(Name("next", prefix=node.get_prefix()), base))
+        elif name:
+            n = Name("__next__", prefix=name.get_prefix())
+            name.replace(n)
+        elif attr:
+            # We don't do this transformation if we're assigning to "x.next".
+            # Unfortunately, it doesn't seem possible to do this in PATTERN,
+            #  so it's being done here.
+            if is_assign_target(node):
+                head = results["head"]
+                if "".join([str(n) for n in head]).strip() == '__builtin__':
+                    self.warning(node, bind_warning)
+                return
+            attr.replace(Name("__next__"))
+        elif "global" in results:
+            self.warning(node, bind_warning)
+            self.shadowed_next = True
+        elif mod:
+            n = find_binding('next', mod)
+            if n:
+                self.warning(n, bind_warning)
+                self.shadowed_next = True
+
+
+### The following functions help test if node is part of an assignment
+###  target.
+
+def is_assign_target(node):
+    assign = find_assign(node)
+    if assign is None:
+        return False
+
+    for child in assign.children:
+        if child.type == token.EQUAL:
+            return False
+        elif is_subtree(child, node):
+            return True
+    return False
+
+def find_assign(node):
+    if node.type == syms.expr_stmt:
+        return node
+    if node.type == syms.simple_stmt or node.parent is None:
+        return None
+    return find_assign(node.parent)
+
+def is_subtree(root, node):
+    if root == node:
+        return True
+    return any([is_subtree(c, node) for c in root.children])