Start to reduce singleton reductions

uncompyle6/parser.py

@@ -45,6 +45,10 @@ class PythonParser(GenericASTBuilder):
             ]
         self.collect = frozenset(nt_list)
 
+        # Reduce singleton reductions in these nonterminals:
+        self.singleton = frozenset(('str', 'joined_str', 'expr', 'store',
+                                    'inplace_op'))
+
     def ast_first_offset(self, ast):
         if hasattr(ast, 'offset'):
             return ast.offset
@@ -154,7 +158,13 @@ class PythonParser(GenericASTBuilder):
         return token.kind
 
     def nonterminal(self, nt, args):
-        if nt in self.collect and len(args) > 1:
+        n = len(args)
+
+        # Use this to find lots of singleton rule
+        # if n == 1 and nt not in self.singleton:
+        #     print("XXX", nt)
+
+        if nt in self.collect and n > 1:
             #
             #  Collect iterated thingies together. That is rather than
             #  stmts -> stmts stmt -> stmts stmt -> ...
@@ -162,6 +172,8 @@ class PythonParser(GenericASTBuilder):
             #
             rv = args[0]
             rv.append(args[1])
+        elif n == 1 and args[0] in self.singleton:
+            rv = GenericASTBuilder.nonterminal(self, nt, args[0])
         else:
             rv = GenericASTBuilder.nonterminal(self, nt, args)
         return rv

uncompyle6/semantics/pysource.py

@@ -898,11 +898,13 @@ class SourceWalker(GenericASTTraversal, object):
         """
         self.write(self.indent, 'exec ')
         self.preorder(node[0])
-        if not node[1][0].isNone():
+
+        if not node[1].isNone():
             sep = ' in '
             for subnode in node[1]:
                 self.write(sep); sep = ", "
                 self.preorder(subnode)
+
         self.println()
         self.prune() # stop recursing
 
@@ -1316,8 +1318,8 @@ class SourceWalker(GenericASTTraversal, object):
                 pass
             pass
         else:
-            ast = ast[0][0]
+            list_comp = ast[0]
-            n = ast[iter_index]
+            n = list_comp[iter_index]
             assert n == 'list_iter', n
 
         # FIXME: I'm not totally sure this is right.
@@ -1406,8 +1408,9 @@ class SourceWalker(GenericASTTraversal, object):
         if node == 'set_comp':
             ast = ast[0][0][0]
         else:
-            ast = ast[0][0][0][0][0]
+            ast = ast[0][0][0][0]
 
+        assert ast == 'list_comp'
         n = ast[1]
         collection = node[-3]
         list_if = None