From 4011a3eb9ef22fe4361c413bfe38b6333a40366a Mon Sep 17 00:00:00 2001
From: Anthony Scopatz <scopatz@gmail.com>
Date: Wed, 11 Feb 2015 00:33:40 -0600
Subject: [PATCH] some ast fixes

---
 xonsh/ast.py    | 29 ++++++++++++++++++++++++-----
 xonsh/execer.py |  6 +++++-
 2 files changed, 29 insertions(+), 6 deletions(-)

diff --git a/xonsh/ast.py b/xonsh/ast.py
index c0392a59f..9747a639c 100644
--- a/xonsh/ast.py
+++ b/xonsh/ast.py
@@ -34,7 +34,7 @@ class CtxAwareTransformer(NodeTransformer):
     a subprocess.
     """
 
-    def __init__(self, pasrer):
+    def __init__(self, parser):
         """Parameters
         ----------
         parser : xonsh.Parser
@@ -74,6 +74,12 @@ class CtxAwareTransformer(NodeTransformer):
     def ctxadd(value):
         self.contexts[-1].add(value)
 
+    def ctxremove(value):
+        for ctx in self.contexts[::-1]:
+            if value in ctx:
+                ctx.remove(value)
+                break
+
     def visit_Expr(self, node):
         lname = leftmostname(node)
         inscope = False
@@ -127,16 +133,29 @@ class CtxAwareTransformer(NodeTransformer):
             self.ctxupdate(map(leftmostname, targ.elts))
         else:
             self.ctxadd(leftmostname(targ))
+        self.generic_visit(node)
         return node
 
     def visit_FunctionDef(self, node):
-        assert False
+        self.ctxadd(node.name)
+        self.generic_visit(node)
+        return node
 
     def visit_ClassDef(self, node):
-        assert False
+        self.ctxadd(node.name)
+        self.generic_visit(node)
+        return node
 
     def visit_Delete(self, node):
-        assert False
+        for targ in node.targets:
+            if isinstance(targ, Name):
+                self.ctxremove(targ.id)
+        self.generic_visit(node)
+        return node
 
     def visit_Try(self, node):
-        assert False
+        for handler in node.handlers:
+            if handler.name is not None:
+                self.ctxadd(handler.name)
+        self.generic_visit(node)
+        return node
diff --git a/xonsh/execer.py b/xonsh/execer.py
index 3c0256127..e858e8da2 100644
--- a/xonsh/execer.py
+++ b/xonsh/execer.py
@@ -26,12 +26,16 @@ class Execer(object):
         self.parser = Parser(**parser_args)
         self.filename = filename
         self.debug_level = debug_level
-        self.ctxtransformer = ast.CtxAwareTransformer(parser)
+        self.ctxtransformer = ast.CtxAwareTransformer(self.parser)
 
     def parse(self, input, ctx):
         """Parses xonsh code in a context-aware fashion. For context-free
         parsing, please use the Parser class directly.
         """
+        if ctx is None:
+            ctx = set()
+        elif isinstance(ctx, Mapping):
+            ctx = set(ctx.keys())
         # Parsing actually happens in a couple of phases. The first is a
         # shortcut for a context-free parser. Nomrally, all subprocess
         # lines should be wrapped in $(), to indicate that they are a