Python 3.7+ optimized if in comprehension

test/simple_source/bug30/06_listcomp.py

@@ -22,3 +22,11 @@ def columnize(l):
     return [i for i in range(len(l))
             if not isinstance(l[i], str)]
 assert [0, 2] == columnize([1, 'a', 2])
+
+# From 3.7 test_generators
+# Bug was in handling the way list_if is optimized in 3.7+;
+# We need list_if37 and compare_chained37.
+def init_board(c):
+    return [io for io in c if 3 <= io < 5]
+
+assert init_board(list(range(6))) == [3, 4]

uncompyle6/parsers/parse37.py

@@ -656,6 +656,7 @@ class Python37Parser(Python37BaseParser):
         testtrue         ::= compare_chained37
         testfalse        ::= compare_chained37_false
 
+        compare_chained     ::= compare_chained37
 
         compare_chained37   ::= expr compare_chained1a_37
         compare_chained37   ::= expr compare_chained1b_37
@@ -668,7 +669,8 @@ class Python37Parser(Python37BaseParser):
         compare_chained1a_37      ::= expr DUP_TOP ROT_THREE COMPARE_OP POP_JUMP_IF_FALSE
                                       compare_chained2a_37 COME_FROM POP_TOP COME_FROM
         compare_chained1b_37      ::= expr DUP_TOP ROT_THREE COMPARE_OP POP_JUMP_IF_FALSE
-                                      compare_chained2b_37 POP_TOP JUMP_FORWARD COME_FROM
+                                      compare_chained2b_37 POP_TOP _jump COME_FROM
+
         compare_chained1c_37      ::= expr DUP_TOP ROT_THREE COMPARE_OP POP_JUMP_IF_FALSE
                                       compare_chained2a_37 POP_TOP
 
@@ -697,6 +699,8 @@ class Python37Parser(Python37BaseParser):
 
         jmp_false37                ::= POP_JUMP_IF_FALSE COME_FROM
         list_if                    ::= expr jmp_false37 list_iter
+        list_iter                  ::= list_if37
+        list_if37                  ::= compare_chained37 list_iter
 
         _ifstmts_jump              ::= c_stmts_opt come_froms
 

uncompyle6/semantics/customize3.py

@@ -143,9 +143,14 @@ def customize_for_version3(self, version):
                         list_ifs.append([1])
                     n = n[2]
                     pass
+                elif n == "list_if37":
+                    list_ifs.append(n)
+                    n = n[-1]
+                    pass
                 pass
 
             assert n == "lc_body", ast
+
             self.preorder(n[0])
 
         # FIXME: add indentation around "for"'s and "in"'s

uncompyle6/semantics/customize37.py

@@ -67,6 +67,7 @@ def customize_for_version37(self, version):
             '%[3]{pattr.replace("-", " ")} %p %p', (0, 19), (6, 19) ),
         'if_exp_37a': ( '%p if %p else %p', (1, 'expr', 27), (0, 27), (4, 'expr', 27) ),
         'if_exp_37b': ( '%p if %p else %p', (2, 'expr', 27), (0, 'expr', 27), (5, 'expr', 27) ),
+        'list_if37':  ( " if %p%c", (0, 27), 1 ),
         'testfalse_not_or': ( "not %c or %c",
                               (0, "expr"),
                               (2, "expr")  ),

uncompyle6/semantics/pysource.py

@@ -1263,6 +1263,7 @@ class SourceWalker(GenericASTTraversal, object):
         if self.version != 3.0:
             assert n.kind in (
                 "lc_body",
+                "list_if37",
                 "comp_body",
                 "set_comp_func",
                 "set_comp_body",
@@ -1369,7 +1370,11 @@ class SourceWalker(GenericASTTraversal, object):
                     list_if = n
                 else:
                     list_if = n[1]
-                n = n[2]
+                n = n[-1]
+                pass
+            elif n == "list_if37":
+                list_ifs.append(n)
+                n = n[-1]
                 pass
             pass