Crash on super call in function with type variable

[ddfisher]

#2193 causes a crash when calling super in function which takes a generic argument (even if the generic argument is unused). Here's the minimum reproducer I've found:

from typing import TypeVar

T = TypeVar('T', int, str)

class A:
    pass

class B(A):
    def __init__(self, arg):
        # type: (T) -> None
        super(B, self).__init__()

@JukkaL @elazarg could you take a look?

[ddfisher]

Here's the traceback (it's for the last line of the file):

Traceback (most recent call last):
  File "/usr/local/Cellar/python3/3.5.2_1/Frameworks/Python.framework/Versions/3.5/lib/python3.5/runpy.py", line 184, in _run_module_as_main
    "__main__", mod_spec)
  File "/usr/local/Cellar/python3/3.5.2_1/Frameworks/Python.framework/Versions/3.5/lib/python3.5/runpy.py", line 85, in _run_code
    exec(code, run_globals)
  File "/Users/ddfisher/src/mypy/mypy/__main__.py", line 5, in <module>
    main(None)
  File "/Users/ddfisher/src/mypy/mypy/main.py", line 41, in main
    res = type_check_only(sources, bin_dir, options)
  File "/Users/ddfisher/src/mypy/mypy/main.py", line 86, in type_check_only
    options=options)
  File "/Users/ddfisher/src/mypy/mypy/build.py", line 180, in build
    dispatch(sources, manager)
  File "/Users/ddfisher/src/mypy/mypy/build.py", line 1509, in dispatch
    process_graph(graph, manager)
  File "/Users/ddfisher/src/mypy/mypy/build.py", line 1689, in process_graph
    process_stale_scc(graph, scc)
  File "/Users/ddfisher/src/mypy/mypy/build.py", line 1768, in process_stale_scc
    graph[id].type_check_first_pass()
  File "/Users/ddfisher/src/mypy/mypy/build.py", line 1437, in type_check_first_pass
    self.type_checker.check_first_pass()
  File "/Users/ddfisher/src/mypy/mypy/checker.py", line 178, in check_first_pass
    self.accept(d)
  File "/Users/ddfisher/src/mypy/mypy/checker.py", line 237, in accept
    typ = node.accept(self)
  File "/Users/ddfisher/src/mypy/mypy/nodes.py", line 709, in accept
    return visitor.visit_class_def(self)
  File "/Users/ddfisher/src/mypy/mypy/checker.py", line 977, in visit_class_def
    self.accept(defn.defs)
  File "/Users/ddfisher/src/mypy/mypy/checker.py", line 237, in accept
    typ = node.accept(self)
  File "/Users/ddfisher/src/mypy/mypy/nodes.py", line 770, in accept
    return visitor.visit_block(self)
  File "/Users/ddfisher/src/mypy/mypy/checker.py", line 1069, in visit_block
    self.accept(s)
  File "/Users/ddfisher/src/mypy/mypy/checker.py", line 237, in accept
    typ = node.accept(self)
  File "/Users/ddfisher/src/mypy/mypy/nodes.py", line 531, in accept
    return visitor.visit_func_def(self)
  File "/Users/ddfisher/src/mypy/mypy/checker.py", line 448, in visit_func_def
    self.check_func_item(defn, name=defn.name())
  File "/Users/ddfisher/src/mypy/mypy/checker.py", line 511, in check_func_item
    self.check_func_def(defn, typ, name)
  File "/Users/ddfisher/src/mypy/mypy/checker.py", line 633, in check_func_def
    self.accept(item.body)
  File "/Users/ddfisher/src/mypy/mypy/checker.py", line 237, in accept
    typ = node.accept(self)
  File "/Users/ddfisher/src/mypy/mypy/nodes.py", line 770, in accept
    return visitor.visit_block(self)
  File "/Users/ddfisher/src/mypy/mypy/checker.py", line 1069, in visit_block
    self.accept(s)
  File "/Users/ddfisher/src/mypy/mypy/checker.py", line 237, in accept
    typ = node.accept(self)
  File "/Users/ddfisher/src/mypy/mypy/nodes.py", line 784, in accept
    return visitor.visit_expression_stmt(self)
  File "/Users/ddfisher/src/mypy/mypy/checker.py", line 1502, in visit_expression_stmt
    self.accept(s.expr)
  File "/Users/ddfisher/src/mypy/mypy/checker.py", line 237, in accept
    typ = node.accept(self)
  File "/Users/ddfisher/src/mypy/mypy/nodes.py", line 1246, in accept
    return visitor.visit_call_expr(self)
  File "/Users/ddfisher/src/mypy/mypy/checker.py", line 1933, in visit_call_expr
    return self.expr_checker.visit_call_expr(e)
  File "/Users/ddfisher/src/mypy/mypy/checkexpr.py", line 170, in visit_call_expr
    callee_type = self.accept(e.callee)
  File "/Users/ddfisher/src/mypy/mypy/checkexpr.py", line 1759, in accept
    return self.chk.accept(node, context)
  File "/Users/ddfisher/src/mypy/mypy/checker.py", line 237, in accept
    typ = node.accept(self)
  File "/Users/ddfisher/src/mypy/mypy/nodes.py", line 1474, in accept
    return visitor.visit_super_expr(self)
  File "/Users/ddfisher/src/mypy/mypy/checker.py", line 2069, in visit_super_expr
    return self.expr_checker.visit_super_expr(e)
  File "/Users/ddfisher/src/mypy/mypy/checkexpr.py", line 1587, in visit_super_expr
    t = self.analyze_super(e, False)
  File "/Users/ddfisher/src/mypy/mypy/checkexpr.py", line 1617, in analyze_super
    original_type=declared_self)
  File "/Users/ddfisher/src/mypy/mypy/checkmember.py", line 185, in analyze_member_access
    return msg.has_no_attr(original_type, name, node)
  File "/Users/ddfisher/src/mypy/mypy/messages.py", line 355, in has_no_attr
    self.fail('{} has no attribute "{}"'.format(self.format(typ),
  File "/Users/ddfisher/src/mypy/mypy/messages.py", line 150, in format
    s = self.format_simple(typ, verbosity)
  File "/Users/ddfisher/src/mypy/mypy/messages.py", line 269, in format_simple
    raise RuntimeError('Type is None')
RuntimeError: Type is None

[elazarg]

Ouch. I think it's what we discussed here. But I will dig deeper.

[elazarg]

Reverting mypy/checkexpr:1612 to typ=fill_typevars(e.info) avoids the crash. Of course it doesn't mean that's the right fix.

[JukkaL]

This seems to work now.