Preliminary support for nested scopes

XXX Still doesn't work right for classes
XXX Still doesn't do sufficient error checking

3 files changed, 396 insertions, 89 deletions

diff --git a/Lib/compiler/pyassem.py b/Lib/compiler/pyassem.py
index 43bf6f4..447a8e7 100644
--- a/Lib/compiler/pyassem.py
+++ b/Lib/compiler/pyassem.py
@@ -99,12 +99,6 @@ class FlowGraph:
         if not self.exit in order:
             order.append(self.exit)
 
-##        for b in order:
-##            print repr(b)
-##            print "\t", b.get_children()
-##            print b
-##            print
-            
         return order
 
     def getBlocks(self):
@@ -222,6 +216,7 @@ CO_OPTIMIZED = 0x0001
 CO_NEWLOCALS = 0x0002
 CO_VARARGS = 0x0004
 CO_VARKEYWORDS = 0x0008
+CO_NESTED = 0x0010
 
 # the FlowGraph is transformed in place; it exists in one of these states
 RAW = "RAW"
@@ -245,6 +240,15 @@ class PyFlowGraph(FlowGraph):
             self.flags = 0
         self.consts = []
         self.names = []
+        # Free variables found by the symbol table scan, including
+        # variables used only in nested scopes, are included here.
+        self.freevars = []
+        self.cellvars = []
+        # The closure list is used to track the order of cell
+        # variables and free variables in the resulting code object.
+        # The offsets used by LOAD_CLOSURE/LOAD_DEREF refer to both
+        # kinds of variables.
+        self.closure = []
         self.varnames = list(args) or []
         for i in range(len(self.varnames)):
             var = self.varnames[i]
@@ -260,6 +264,12 @@ class PyFlowGraph(FlowGraph):
         if flag == CO_VARARGS:
             self.argcount = self.argcount - 1
 
+    def setFreeVars(self, names):
+        self.freevars = list(names)
+
+    def setCellVars(self, names):
+        self.cellvars = names
+
     def getCode(self):
         """Get a Python code object"""
         if self.stage == RAW:
@@ -335,6 +345,7 @@ class PyFlowGraph(FlowGraph):
         """Convert arguments from symbolic to concrete form"""
         assert self.stage == FLAT
         self.consts.insert(0, self.docstring)
+        self.sort_cellvars()
         for i in range(len(self.insts)):
             t = self.insts[i]
             if len(t) == 2:
@@ -345,6 +356,19 @@ class PyFlowGraph(FlowGraph):
                     self.insts[i] = opname, conv(self, oparg)
         self.stage = CONV
 
+    def sort_cellvars(self):
+        """Sort cellvars in the order of varnames and prune from freevars.
+        """
+        cells = {}
+        for name in self.cellvars:
+            cells[name] = 1
+        self.cellvars = [name for name in self.varnames
+                         if cells.has_key(name)]
+        for name in self.cellvars:
+            del cells[name]
+        self.cellvars = self.cellvars + cells.keys()
+        self.closure = self.cellvars + self.freevars
+
     def _lookupName(self, name, list):
         """Return index of name in list, appending if necessary"""
         t = type(name)
@@ -382,6 +406,17 @@ class PyFlowGraph(FlowGraph):
     _convert_STORE_GLOBAL = _convert_NAME
     _convert_DELETE_GLOBAL = _convert_NAME
 
+    def _convert_DEREF(self, arg):
+        self._lookupName(arg, self.names)
+        self._lookupName(arg, self.varnames)
+        return self._lookupName(arg, self.closure)
+    _convert_LOAD_DEREF = _convert_DEREF
+    _convert_STORE_DEREF = _convert_DEREF
+
+    def _convert_LOAD_CLOSURE(self, arg):
+        self._lookupName(arg, self.varnames)
+        return self._lookupName(arg, self.closure)
+
     _cmp = list(dis.cmp_op)
     def _convert_COMPARE_OP(self, arg):
         return self._cmp.index(arg)
@@ -432,7 +467,8 @@ class PyFlowGraph(FlowGraph):
                         self.lnotab.getCode(), self.getConsts(),
                         tuple(self.names), tuple(self.varnames),
                         self.filename, self.name, self.lnotab.firstline,
-                        self.lnotab.getTable())
+                        self.lnotab.getTable(), tuple(self.freevars),
+                        tuple(self.cellvars))
 
     def getConsts(self):
         """Return a tuple for the const slot of the code object
diff --git a/Lib/compiler/pycodegen.py b/Lib/compiler/pycodegen.py
index 3ba31e4..2d4564a 100644
--- a/Lib/compiler/pycodegen.py
+++ b/Lib/compiler/pycodegen.py
@@ -9,8 +9,10 @@ import types
 from cStringIO import StringIO
 
 from compiler import ast, parse, walk
-from compiler import pyassem, misc, future
-from compiler.pyassem import CO_VARARGS, CO_VARKEYWORDS, CO_NEWLOCALS, TupleArg
+from compiler import pyassem, misc, future, symbols
+from compiler.consts import SC_LOCAL, SC_GLOBAL, SC_FREE, SC_CELL
+from compiler.pyassem import CO_VARARGS, CO_VARKEYWORDS, CO_NEWLOCALS,\
+     CO_NESTED, TupleArg
 
 # Do we have Python 1.x or Python 2.x?
 try:
@@ -46,7 +48,7 @@ class Module:
         tree = parse(self.source)
         root, filename = os.path.split(self.filename)
         if "nested_scopes" in future.find_futures(tree):
-            gen = NestedScopeCodeGenerator(filename)
+            gen = NestedScopeModuleCodeGenerator(filename)
         else:
             gen = ModuleCodeGenerator(filename)
         walk(tree, gen, 1)
@@ -70,14 +72,71 @@ class Module:
         mtime = struct.pack('i', mtime)
         return self.MAGIC + mtime
 
+class LocalNameFinder:
+    """Find local names in scope"""
+    def __init__(self, names=()):
+        self.names = misc.Set()
+        self.globals = misc.Set()
+        for name in names:
+            self.names.add(name)
+
+    # XXX list comprehensions and for loops
+
+    def getLocals(self):
+        for elt in self.globals.elements():
+            if self.names.has_elt(elt):
+                self.names.remove(elt)
+        return self.names
+
+    def visitDict(self, node):
+        pass
+
+    def visitGlobal(self, node):
+        for name in node.names:
+            self.globals.add(name)
+
+    def visitFunction(self, node):
+        self.names.add(node.name)
+
+    def visitLambda(self, node):
+        pass
+
+    def visitImport(self, node):
+        for name, alias in node.names:
+            self.names.add(alias or name)
+
+    def visitFrom(self, node):
+        for name, alias in node.names:
+            self.names.add(alias or name)
+
+    def visitClass(self, node):
+        self.names.add(node.name)
+
+    def visitAssName(self, node):
+        self.names.add(node.name)
+
 class CodeGenerator:
+    """Defines basic code generator for Python bytecode
+
+    This class is an abstract base class.  Concrete subclasses must
+    define an __init__() that defines self.graph and then calls the
+    __init__() defined in this class.
+
+    The concrete class must also define the class attributes
+    NameFinder, FunctionGen, and ClassGen.  These attributes can be
+    defined in the initClass() method, which is a hook for
+    initializing these methods after all the classes have been
+    defined. 
+    """
 
     optimized = 0 # is namespace access optimized?
+    __initialized = None
 
     def __init__(self, filename):
-## Subclasses must define a constructor that intializes self.graph
-## before calling this init function, e.g.
-##         self.graph = pyassem.PyFlowGraph()
+        if self.__initialized is None:
+            self.initClass()
+            self.__class__.__initialized = 1
+        self.checkClass()
         self.filename = filename
         self.locals = misc.Stack()
         self.loops = misc.Stack()
@@ -86,6 +145,20 @@ class CodeGenerator:
         self.last_lineno = None
         self._setupGraphDelegation()
 
+    def initClass(self):
+        """This method is called once for each class"""
+
+    def checkClass(self):
+        """Verify that class is constructed correctly"""
+        try:
+            assert hasattr(self, 'graph')
+            assert getattr(self, 'NameFinder')
+            assert getattr(self, 'FunctionGen')
+            assert getattr(self, 'ClassGen')
+        except AssertionError, msg:
+            intro = "Bad class construction for %s" % self.__class__.__name__
+            raise AssertionError, intro
+
     def _setupGraphDelegation(self):
         self.emit = self.graph.emit
         self.newBlock = self.graph.newBlock
@@ -139,10 +212,15 @@ class CodeGenerator:
         return 0
 
     # The first few visitor methods handle nodes that generator new
-    # code objects 
+    # code objects.  They use class attributes to determine what
+    # specialized code generators to use.
+
+    NameFinder = LocalNameFinder
+    FunctionGen = None
+    ClassGen = None
 
     def visitModule(self, node):
-        lnf = walk(node.node, LocalNameFinder(), 0)
+        lnf = walk(node.node, self.NameFinder(), 0)
         self.locals.push(lnf.getLocals())
         if node.doc:
             self.fixDocstring(node.node)
@@ -159,8 +237,8 @@ class CodeGenerator:
     def visitLambda(self, node):
         self._visitFuncOrLambda(node, isLambda=1)
 
-    def _visitFuncOrLambda(self, node, isLambda):
-        gen = FunctionCodeGenerator(node, self.filename, isLambda)
+    def _visitFuncOrLambda(self, node, isLambda=0):
+        gen = self.FunctionGen(node, self.filename, self.scopes, isLambda)
         walk(node.code, gen)
         gen.finish()
         self.set_lineno(node)
@@ -170,7 +248,7 @@ class CodeGenerator:
         self.emit('MAKE_FUNCTION', len(node.defaults))
 
     def visitClass(self, node):
-        gen = ClassCodeGenerator(node, self.filename)
+        gen = self.ClassGen(node, self.filename, self.scopes)
         if node.doc:
             self.fixDocstring(node.code)
         walk(node.code, gen)
@@ -180,7 +258,7 @@ class CodeGenerator:
         for base in node.bases:
             self.visit(base)
         self.emit('BUILD_TUPLE', len(node.bases))
-        self.emit('LOAD_CONST', gen.getCode())
+        self.emit('LOAD_CONST', gen)
         self.emit('MAKE_FUNCTION', 0)
         self.emit('CALL_FUNCTION', 0)
         self.emit('BUILD_CLASS')
@@ -883,34 +961,114 @@ class CodeGenerator:
             self.visit(k)
             self.emit('STORE_SUBSCR')
 
-class ModuleCodeGenerator(CodeGenerator):
-    __super_init = CodeGenerator.__init__
+class NestedScopeCodeGenerator(CodeGenerator):
     __super_visitModule = CodeGenerator.visitModule
-    
-    def __init__(self, filename):
-        # XXX <module> is ? in compile.c
-        self.graph = pyassem.PyFlowGraph("<module>", filename)
-        self.__super_init(filename)
-        self.symbols = None
+    __super_visitClass = CodeGenerator.visitClass
+    __super__visitFuncOrLambda = CodeGenerator._visitFuncOrLambda
+
+    def parseSymbols(self, tree):
+        s = symbols.SymbolVisitor()
+        walk(tree, s)
+        return s.scopes
 
     def visitModule(self, node):
-        self.symbols = self.parseSymbols(node)
+        self.scopes = self.parseSymbols(node)
+        self.scope = self.scopes[node]
         self.__super_visitModule(node)
 
-    def parseSymbols(self, node):
-        # XXX not implemented
-        return None
+    def _nameOp(self, prefix, name):
+        scope = self.scope.check_name(name)
+        if scope == SC_LOCAL:
+            if not self.optimized:
+                self.emit(prefix + '_NAME', name)
+            else:
+                self.emit(prefix + '_FAST', name)
+        elif scope == SC_GLOBAL:
+            self.emit(prefix + '_GLOBAL', name)
+        elif scope == SC_FREE or scope == SC_CELL:
+            self.emit(prefix + '_DEREF', name)
+        else:
+            raise RuntimeError, "unsupported scope for var %s: %d" % \
+                  (name, scope)
 
-class NestedScopeCodeGenerator(ModuleCodeGenerator):
-    pass
+    def _visitFuncOrLambda(self, node, isLambda=0):
+        gen = self.FunctionGen(node, self.filename, self.scopes, isLambda)
+        walk(node.code, gen)
+        gen.finish()
+        self.set_lineno(node)
+        for default in node.defaults:
+            self.visit(default)
+        frees = gen.scope.get_free_vars()
+        if frees:
+            for name in frees:
+                self.emit('LOAD_CLOSURE', name)
+            self.emit('LOAD_CONST', gen)
+            self.emit('MAKE_CLOSURE', len(node.defaults))
+        else:
+            self.emit('LOAD_CONST', gen)
+            self.emit('MAKE_FUNCTION', len(node.defaults))
 
-class FunctionCodeGenerator(CodeGenerator):
-    super_init = CodeGenerator.__init__
+    def visitClass(self, node):
+        gen = self.ClassGen(node, self.filename, self.scopes)
+        if node.doc:
+            self.fixDocstring(node.code)
+        walk(node.code, gen)
+        gen.finish()
+        self.set_lineno(node)
+        self.emit('LOAD_CONST', node.name)
+        for base in node.bases:
+            self.visit(base)
+        self.emit('BUILD_TUPLE', len(node.bases))
+        frees = gen.scope.get_free_vars()
+        for name in frees:
+            self.emit('LOAD_CLOSURE', name)
+        self.emit('LOAD_CONST', gen)
+        if frees:
+            self.emit('MAKE_CLOSURE', 0)
+        else:
+            self.emit('MAKE_FUNCTION', 0)
+        self.emit('CALL_FUNCTION', 0)
+        self.emit('BUILD_CLASS')
+        self.storeName(node.name)
+        
+
+class LGBScopeMixin:
+    """Defines initClass() for Python 2.1-compatible scoping"""
+    def initClass(self):
+        self.__class__.NameFinder = LocalNameFinder
+        self.__class__.FunctionGen = FunctionCodeGenerator
+        self.__class__.ClassGen = ClassCodeGenerator
+
+class NestedScopeMixin:
+    """Defines initClass() for nested scoping (Python 2.2-compatible)"""
+    def initClass(self):
+        self.__class__.NameFinder = LocalNameFinder
+        self.__class__.FunctionGen = NestedFunctionCodeGenerator
+        self.__class__.ClassGen = NestedClassCodeGenerator
+
+class ModuleCodeGenerator(LGBScopeMixin, CodeGenerator):
+    __super_init = CodeGenerator.__init__
 
+    scopes = None
+    
+    def __init__(self, filename):
+        self.graph = pyassem.PyFlowGraph("<module>", filename)
+        self.__super_init(filename)
+
+class NestedScopeModuleCodeGenerator(NestedScopeMixin,
+                                     NestedScopeCodeGenerator):
+    __super_init = CodeGenerator.__init__
+    
+    def __init__(self, filename):
+        self.graph = pyassem.PyFlowGraph("<module>", filename)
+        self.__super_init(filename)
+        self.graph.setFlag(CO_NESTED)
+
+class AbstractFunctionCode:
     optimized = 1
     lambdaCount = 0
 
-    def __init__(self, func, filename, isLambda=0):
+    def __init__(self, func, filename, scopes, isLambda):
         if isLambda:
             klass = FunctionCodeGenerator
             name = "<lambda.%d>" % klass.lambdaCount
@@ -926,7 +1084,7 @@ class FunctionCodeGenerator(CodeGenerator):
         if not isLambda and func.doc:
             self.setDocstring(func.doc)
 
-        lnf = walk(func.code, LocalNameFinder(args), 0)
+        lnf = walk(func.code, self.NameFinder(args), 0)
         self.locals.push(lnf.getLocals())
         if func.varargs:
             self.graph.setFlag(CO_VARARGS)
@@ -963,14 +1121,32 @@ class FunctionCodeGenerator(CodeGenerator):
 
     unpackTuple = unpackSequence
 
-class ClassCodeGenerator(CodeGenerator):
-    super_init = CodeGenerator.__init__
+class FunctionCodeGenerator(LGBScopeMixin, AbstractFunctionCode,
+                            CodeGenerator): 
+    super_init = CodeGenerator.__init__ # call be other init
+    scopes = None
+
+class NestedFunctionCodeGenerator(AbstractFunctionCode,
+                                  NestedScopeMixin,
+                                  NestedScopeCodeGenerator):
+    super_init = NestedScopeCodeGenerator.__init__ # call be other init
+    __super_init = AbstractFunctionCode.__init__
+
+    def __init__(self, func, filename, scopes, isLambda):
+        self.scopes = scopes
+        self.scope = scopes[func]
+        self.__super_init(func, filename, scopes, isLambda)
+        self.graph.setFreeVars(self.scope.get_free_vars())
+        self.graph.setCellVars(self.scope.get_cell_vars())
+        self.graph.setFlag(CO_NESTED)
+
+class AbstractClassCode:
 
-    def __init__(self, klass, filename):
+    def __init__(self, klass, filename, scopes):
         self.graph = pyassem.PyFlowGraph(klass.name, filename,
                                            optimized=0)
         self.super_init(filename)
-        lnf = walk(klass.code, LocalNameFinder(), 0)
+        lnf = walk(klass.code, self.NameFinder(), 0)
         self.locals.push(lnf.getLocals())
         self.graph.setFlag(CO_NEWLOCALS)
         if klass.doc:
@@ -981,6 +1157,24 @@ class ClassCodeGenerator(CodeGenerator):
         self.emit('LOAD_LOCALS')
         self.emit('RETURN_VALUE')
 
+class ClassCodeGenerator(LGBScopeMixin, AbstractClassCode, CodeGenerator):
+    super_init = CodeGenerator.__init__
+    scopes = None
+
+class NestedClassCodeGenerator(AbstractClassCode,
+                               NestedScopeMixin,
+                               NestedScopeCodeGenerator):
+    super_init = NestedScopeCodeGenerator.__init__ # call be other init
+    __super_init = AbstractClassCode.__init__
+
+    def __init__(self, klass, filename, scopes):
+        self.scopes = scopes
+        self.scope = scopes[klass]
+        self.__super_init(klass, filename, scopes)
+        self.graph.setFreeVars(self.scope.get_free_vars())
+        self.graph.setCellVars(self.scope.get_cell_vars())
+        self.graph.setFlag(CO_NESTED)
+
 def generateArgList(arglist):
     """Generate an arg list marking TupleArgs"""
     args = []
@@ -997,49 +1191,6 @@ def generateArgList(arglist):
             raise ValueError, "unexpect argument type:", elt
     return args + extra, count
 
-class LocalNameFinder:
-    """Find local names in scope"""
-    def __init__(self, names=()):
-        self.names = misc.Set()
-        self.globals = misc.Set()
-        for name in names:
-            self.names.add(name)
-
-    # XXX list comprehensions and for loops
-
-    def getLocals(self):
-        for elt in self.globals.elements():
-            if self.names.has_elt(elt):
-                self.names.remove(elt)
-        return self.names
-
-    def visitDict(self, node):
-        pass
-
-    def visitGlobal(self, node):
-        for name in node.names:
-            self.globals.add(name)
-
-    def visitFunction(self, node):
-        self.names.add(node.name)
-
-    def visitLambda(self, node):
-        pass
-
-    def visitImport(self, node):
-        for name, alias in node.names:
-            self.names.add(alias or name)
-
-    def visitFrom(self, node):
-        for name, alias in node.names:
-            self.names.add(alias or name)
-
-    def visitClass(self, node):
-        self.names.add(node.name)
-
-    def visitAssName(self, node):
-        self.names.add(node.name)
-
 def findOp(node):
     """Find the op (DELETE, LOAD, STORE) in an AssTuple tree"""
     v = OpFinder()
diff --git a/Lib/compiler/symbols.py b/Lib/compiler/symbols.py
index 3ab72f3..cde937b 100644
--- a/Lib/compiler/symbols.py
+++ b/Lib/compiler/symbols.py
@@ -1,8 +1,11 @@
 """Module symbol-table generator"""
 
 from compiler import ast
+from compiler.consts import SC_LOCAL, SC_GLOBAL, SC_FREE, SC_CELL, SC_UNKNOWN
 import types
 
+import sys
+
 MANGLE_LEN = 256
 
 class Scope:
@@ -14,7 +17,12 @@ class Scope:
         self.uses = {}
         self.globals = {}
         self.params = {}
+        self.frees = {}
+        self.cells = {}
         self.children = []
+        # nested is true if the class could contain free variables,
+        # i.e. if it is nested within another function.
+        self.nested = None
         self.klass = None
         if klass is not None:
             for i in range(len(klass)):
@@ -70,13 +78,112 @@ class Scope:
     def get_children(self):
         return self.children
 
+    def DEBUG(self):
+        return
+        print >> sys.stderr, self.name, self.nested and "nested" or ""
+        print >> sys.stderr, "\tglobals: ", self.globals
+        print >> sys.stderr, "\tcells: ", self.cells
+        print >> sys.stderr, "\tdefs: ", self.defs
+        print >> sys.stderr, "\tuses: ", self.uses
+        print >> sys.stderr, "\tfrees:", self.frees
+
+    def check_name(self, name):
+        """Return scope of name.
+
+        The scope of a name could be LOCAL, GLOBAL, FREE, or CELL.
+        """
+        if self.globals.has_key(name):
+            return SC_GLOBAL
+        if self.cells.has_key(name):
+            return SC_CELL
+        if self.defs.has_key(name):
+            return SC_LOCAL
+        if self.nested and (self.frees.has_key(name) or
+                            self.uses.has_key(name)):
+            return SC_FREE
+        if self.nested:
+            return SC_UNKNOWN
+        else:
+            return SC_GLOBAL
+
+    def get_free_vars(self):
+        if not self.nested:
+            return ()
+        free = {}
+        free.update(self.frees)
+        for name in self.uses.keys():
+            if not (self.defs.has_key(name) or
+                    self.globals.has_key(name)):
+                free[name] = 1
+        return free.keys()
+
+    def handle_children(self):
+        for child in self.children:
+            frees = child.get_free_vars()
+            globals = self.add_frees(frees)
+            for name in globals:
+                child.force_global(name)
+
+    def force_global(self, name):
+        """Force name to be global in scope.
+
+        Some child of the current node had a free reference to name.
+        When the child was processed, it was labelled a free
+        variable.  Now that all its enclosing scope have been
+        processed, the name is known to be a global or builtin.  So
+        walk back down the child chain and set the name to be global
+        rather than free.
+
+        Be careful to stop if a child does not think the name is
+        free. 
+        """
+        self.globals[name] = 1
+        if self.frees.has_key(name):
+            del self.frees[name]
+        for child in self.children:
+            if child.check_name(name) == SC_FREE:
+                child.force_global(name)
+
+    def add_frees(self, names):
+        """Process list of free vars from nested scope.
+
+        Returns a list of names that are either 1) declared global in the
+        parent or 2) undefined in a top-level parent.  In either case,
+        the nested scope should treat them as globals.
+        """
+        child_globals = []
+        for name in names:
+            sc = self.check_name(name)
+            if self.nested:
+                if sc == SC_UNKNOWN or sc == SC_FREE \
+                   or isinstance(self, ClassScope):
+                    self.frees[name] = 1
+                elif sc == SC_GLOBAL:
+                    child_globals.append(name)
+                elif isinstance(self, FunctionScope) and sc == SC_LOCAL:
+                    self.cells[name] = 1
+                else:
+                    child_globals.append(name)
+            else:
+                if sc == SC_LOCAL:
+                    self.cells[name] = 1
+                else:
+                    child_globals.append(name)
+        return child_globals
+
+    def get_cell_vars(self):
+        return self.cells.keys()
+
 class ModuleScope(Scope):
     __super_init = Scope.__init__
     
     def __init__(self):
         self.__super_init("global", self)
 
-class LambdaScope(Scope):
+class FunctionScope(Scope):
+    pass
+
+class LambdaScope(FunctionScope):
     __super_init = Scope.__init__
 
     __counter = 1
@@ -86,9 +193,6 @@ class LambdaScope(Scope):
         self.__counter += 1
         self.__super_init("lambda.%d" % i, module, klass)
 
-class FunctionScope(Scope):
-    pass
-
 class ClassScope(Scope):
     __super_init = Scope.__init__
 
@@ -111,17 +215,24 @@ class SymbolVisitor:
         for n in node.defaults:
             self.visit(n, parent)
         scope = FunctionScope(node.name, self.module, self.klass)
+        if parent.nested or isinstance(parent, FunctionScope):
+            scope.nested = 1
         self.scopes[node] = scope
         self._do_args(scope, node.argnames)
         self.visit(node.code, scope)
-
+        self.handle_free_vars(scope, parent)
+        scope.DEBUG()
+        
     def visitLambda(self, node, parent):
         for n in node.defaults:
             self.visit(n, parent)
         scope = LambdaScope(self.module, self.klass)
+        if parent.nested or isinstance(parent, FunctionScope):
+            scope.nested = 1
         self.scopes[node] = scope
         self._do_args(scope, node.argnames)
         self.visit(node.code, scope)
+        self.handle_free_vars(scope, parent)
 
     def _do_args(self, scope, args):
         for name in args:
@@ -130,16 +241,25 @@ class SymbolVisitor:
             else:
                 scope.add_param(name)
 
+    def handle_free_vars(self, scope, parent):
+        parent.add_child(scope)
+        if scope.children:
+            scope.DEBUG()
+        scope.handle_children()
+
     def visitClass(self, node, parent):
         parent.add_def(node.name)
         for n in node.bases:
             self.visit(n, parent)
         scope = ClassScope(node.name, self.module)
+        if parent.nested or isinstance(parent, FunctionScope):
+            scope.nested = 1
         self.scopes[node] = scope
         prev = self.klass
         self.klass = node.name
         self.visit(node.code, scope)
         self.klass = prev
+        self.handle_free_vars(scope, parent)
 
     # name can be a def or a use