Analyzer throws exception when analyzing list comprehension as argument

[gene1wood]

The analyzer has difficulty with code like this

x = ''.join('a' for y in [1,2,3])

For example in an app like this

from chalice import Chalice, Response

app = Chalice(app_name='example')

@app.route('/')
def index():
    body = '<h1>test</h1>'
    x = ''.join('a' for y in [1,2,3])
    return Response(body=body,
                    status_code=200,
                    headers={'Content-Type': 'text/html'})

Expected Results

chalice gen-policy or chalice deploy should generate a policy or deploy the app

Actual Results

$ chalice gen-policy
Traceback (most recent call last):
  File "/usr/local/bin/chalice", line 11, in <module>
    load_entry_point('chalice==0.6.0', 'console_scripts', 'chalice')()
  File "/usr/local/lib/python2.7/dist-packages/chalice/cli/__init__.py", line 298, in main
    return cli(obj={})
  File "/usr/local/lib/python2.7/dist-packages/click/core.py", line 716, in __call__
    return self.main(*args, **kwargs)
  File "/usr/local/lib/python2.7/dist-packages/click/core.py", line 696, in main
    rv = self.invoke(ctx)
  File "/usr/local/lib/python2.7/dist-packages/click/core.py", line 1060, in invoke
    return _process_result(sub_ctx.command.invoke(sub_ctx))
  File "/usr/local/lib/python2.7/dist-packages/click/core.py", line 889, in invoke
    return ctx.invoke(self.callback, **ctx.params)
  File "/usr/local/lib/python2.7/dist-packages/click/core.py", line 534, in invoke
    return callback(*args, **kwargs)
  File "/usr/local/lib/python2.7/dist-packages/click/decorators.py", line 17, in new_func
    return f(get_current_context(), *args, **kwargs)
  File "/usr/local/lib/python2.7/dist-packages/chalice/cli/__init__.py", line 214, in gen_policy
    generated = policy.policy_from_source_code(contents)
  File "/usr/local/lib/python2.7/dist-packages/chalice/policy.py", line 20, in policy_from_source_code
    client_calls = get_client_calls_for_app(source_code)
  File "/usr/local/lib/python2.7/dist-packages/chalice/analyzer.py", line 74, in get_client_calls_for_app
    binder = t.bind_types()
  File "/usr/local/lib/python2.7/dist-packages/chalice/analyzer.py", line 331, in bind_types
    self.visit(self._current_ast_namespace)
  File "/usr/local/lib/python2.7/dist-packages/chalice/analyzer.py", line 540, in visit
    return ast.NodeVisitor.visit(self, node)
  File "/usr/lib/python2.7/ast.py", line 241, in visit
    return visitor(node)
  File "/usr/lib/python2.7/ast.py", line 249, in generic_visit
    self.visit(item)
  File "/usr/local/lib/python2.7/dist-packages/chalice/analyzer.py", line 540, in visit
    return ast.NodeVisitor.visit(self, node)
  File "/usr/lib/python2.7/ast.py", line 241, in visit
    return visitor(node)
  File "/usr/local/lib/python2.7/dist-packages/chalice/analyzer.py", line 390, in visit_Assign
    self.generic_visit(node)
  File "/usr/lib/python2.7/ast.py", line 251, in generic_visit
    self.visit(value)
  File "/usr/local/lib/python2.7/dist-packages/chalice/analyzer.py", line 540, in visit
    return ast.NodeVisitor.visit(self, node)
  File "/usr/lib/python2.7/ast.py", line 241, in visit
    return visitor(node)
  File "/usr/local/lib/python2.7/dist-packages/chalice/analyzer.py", line 424, in visit_Call
    self.generic_visit(node)
  File "/usr/lib/python2.7/ast.py", line 249, in generic_visit
    self.visit(item)
  File "/usr/local/lib/python2.7/dist-packages/chalice/analyzer.py", line 540, in visit
    return ast.NodeVisitor.visit(self, node)
  File "/usr/lib/python2.7/ast.py", line 241, in visit
    return visitor(node)
  File "/usr/lib/python2.7/ast.py", line 249, in generic_visit
    self.visit(item)
  File "/usr/local/lib/python2.7/dist-packages/chalice/analyzer.py", line 540, in visit
    return ast.NodeVisitor.visit(self, node)
  File "/usr/lib/python2.7/ast.py", line 241, in visit
    return visitor(node)
  File "/usr/lib/python2.7/ast.py", line 251, in generic_visit
    self.visit(value)
  File "/usr/local/lib/python2.7/dist-packages/chalice/analyzer.py", line 540, in visit
    return ast.NodeVisitor.visit(self, node)
  File "/usr/lib/python2.7/ast.py", line 241, in visit
    return visitor(node)
  File "/usr/local/lib/python2.7/dist-packages/chalice/analyzer.py", line 381, in visit_Name
    self._symbol_table.get_inferred_type(node.id)
  File "/usr/local/lib/python2.7/dist-packages/chalice/analyzer.py", line 241, in get_inferred_type
    symbol = self._local_table.lookup(name)
  File "/usr/lib/python2.7/symtable.py", line 100, in lookup
    flags = self._table.symbols[name]
KeyError: 'y'

[jamesls]

Confirmed bug, thanks for reporting.