Fix 3.2 for/if loopback bug

problem was handling in Python 3.2

 for ...
    if ...
    else:
      ....
      jump for
    come from if
    jump for

In later Python 3's a "come from" is removed.

Also, start to DRY parser{,2,3} grammar rules.

test/simple_source/looping/10_for_if_loopback.py

@@ -0,0 +1,23 @@
+# In Python 3.2 JUMP_ABSOLUTE's (which can
+# turn into COME_FROM's) are not optimized as
+# they are in later Python's.
+#
+# So an if statement can jump to the end of a for loop
+# which in turn jump's back to the beginning of that loop.
+#
+# Should handle in Python 3.2
+#
+#          98	JUMP_BACK         '16' statement after: names.append(name) to loop head
+#       101_0	COME_FROM         '50' statement: if name == ...to fictional "end if"
+#         101	JUMP_BACK         '16' jump as before to loop head
+
+def _slotnames(cls):
+    names = []
+    for c in cls.__mro__:
+        if "__slots__" in c.__dict__:
+            slots = c.__dict__['__slots__']
+            for name in slots:
+                if name == "__dict__":
+                    continue
+                else:
+                    names.append(name) # 3.2 bug here jumping to outer for

uncompyle6/parser.py

@@ -161,6 +161,27 @@ class PythonParser(GenericASTBuilder):
         assign3 ::= expr expr expr ROT_THREE ROT_TWO designator designator designator
         '''
 
+    def p_forstmt(self, args):
+        """
+        _for ::= GET_ITER FOR_ITER
+        _for ::= LOAD_CONST FOR_LOOP
+
+        for_block ::= l_stmts_opt JUMP_BACK
+        for_block ::= return_stmts _come_from
+
+        forstmt ::= SETUP_LOOP expr _for designator
+                for_block POP_BLOCK _come_from
+
+        forelsestmt ::= SETUP_LOOP expr _for designator
+                for_block POP_BLOCK else_suite COME_FROM
+
+        forelselaststmt ::= SETUP_LOOP expr _for designator
+                for_block POP_BLOCK else_suitec COME_FROM
+
+        forelselaststmtl ::= SETUP_LOOP expr _for designator
+                for_block POP_BLOCK else_suitel COME_FROM
+        """
+
     def p_import20(self, args):
         '''
         stmt ::= importstmt

uncompyle6/parsers/parse2.py

@@ -344,25 +344,6 @@ class Python2Parser(PythonParser):
                 l_stmts_opt JUMP_BACK
                 POP_BLOCK
                 else_suitec COME_FROM
-
-        _for ::= GET_ITER FOR_ITER
-        _for ::= LOAD_CONST FOR_LOOP
-
-        for_block ::= l_stmts_opt JUMP_BACK
-        for_block ::= return_stmts _come_from
-
-        forstmt ::= SETUP_LOOP expr _for designator
-                for_block POP_BLOCK COME_FROM
-
-        forelsestmt ::= SETUP_LOOP expr _for designator
-                for_block POP_BLOCK else_suite COME_FROM
-
-        forelselaststmt ::= SETUP_LOOP expr _for designator
-                for_block POP_BLOCK else_suitec COME_FROM
-
-        forelselaststmtl ::= SETUP_LOOP expr _for designator
-                for_block POP_BLOCK else_suitel COME_FROM
-
         '''
 
     def p_expr2(self, args):

uncompyle6/parsers/parse3.py

@@ -350,26 +350,21 @@ class Python3Parser(PythonParser):
                 l_stmts_opt JUMP_BACK
                 POP_BLOCK
                 else_suitec COME_FROM
-
-        _for ::= GET_ITER FOR_ITER
-        _for ::= LOAD_CONST FOR_LOOP
-
-        for_block ::= l_stmts_opt JUMP_BACK
-        for_block ::= return_stmts _come_from
-
-        forstmt ::= SETUP_LOOP expr _for designator
-                for_block POP_BLOCK _come_from
-
-        forelsestmt ::= SETUP_LOOP expr _for designator
-                for_block POP_BLOCK else_suite COME_FROM
-
-        forelselaststmt ::= SETUP_LOOP expr _for designator
-                for_block POP_BLOCK else_suitec COME_FROM
-
-        forelselaststmtl ::= SETUP_LOOP expr _for designator
-                for_block POP_BLOCK else_suitel COME_FROM
         '''
 
+    def p_for3(self, args):
+        """
+        # In Python 3.2 JUMP_ABSOLUTE's (which can
+        # turn into COME_FROM's) are not optimized as
+        # they are in later Python's.
+        #
+        # So an if statement can jump to the end of a for loop
+        # which in turn jump's back to the beginning of that loop.
+        #
+        # Therefore we allow COME_FROM JUMP_BACK below.
+        for_block ::= l_stmts_opt COME_FROM JUMP_BACK
+        """
+
     def p_genexpr3(self, args):
         '''
         load_genexpr ::= LOAD_GENEXPR

uncompyle6/scanners/scanner32.py

@@ -2,9 +2,9 @@
 """
 Python 3.2 bytecode scanner/deparser
 
-This overlaps Python's 3.2's dis module, but it can be run from
-Python 2 and other versions of Python. Also, we save token information
-for later use in deparsing.
+This overlaps various Python3.2's dis module, but it can be run from
+Python versions other than the version running this code. Notably,
+run from Python version 2. See doc comments in scanner3.py for more information.
 """
 
 from __future__ import print_function