Crash when attempting a generic NamedTuple

[gnprice]

This program causes mypy to crash:

from typing import TypeVar, NamedTuple, Generic

T = TypeVar('T')

class C(NamedTuple('C', [('x', T),]), Generic[T]):
    def get(self):
        # type: () -> T
        pass

Traceback (most recent call last):
  File "/home/gregprice/w/mypy/env/bin/mypy", line 12, in <module>
    exec(compile(open(__file__).read(), __file__, 'exec'))
  File "/home/gregprice/w/mypy/scripts/mypy", line 6, in <module>
    main(__file__)
  File "/home/gregprice/w/mypy/env/lib/python3.4/site-packages/mypy/main.py", line 54, in main
    res = type_check_only(sources, bin_dir, options)
  File "/home/gregprice/w/mypy/env/lib/python3.4/site-packages/mypy/main.py", line 102, in type_check_only
    python_path=options.python_path)
  File "/home/gregprice/w/mypy/env/lib/python3.4/site-packages/mypy/build.py", line 211, in build
    dispatch(sources, manager)
  File "/home/gregprice/w/mypy/env/lib/python3.4/site-packages/mypy/build.py", line 1336, in dispatch
    process_graph(graph, manager)
  File "/home/gregprice/w/mypy/env/lib/python3.4/site-packages/mypy/build.py", line 1467, in process_graph
    process_stale_scc(graph, scc)
  File "/home/gregprice/w/mypy/env/lib/python3.4/site-packages/mypy/build.py", line 1493, in process_stale_scc
    graph[id].semantic_analysis()
  File "/home/gregprice/w/mypy/env/lib/python3.4/site-packages/mypy/build.py", line 1303, in semantic_analysis
    self.manager.semantic_analyzer.visit_file(self.tree, self.xpath)
  File "/home/gregprice/w/mypy/env/lib/python3.4/site-packages/mypy/semanal.py", line 247, in visit_file
    self.accept(d)
  File "/home/gregprice/w/mypy/env/lib/python3.4/site-packages/mypy/semanal.py", line 2283, in accept
    node.accept(self)
  File "/home/gregprice/w/mypy/env/lib/python3.4/site-packages/mypy/nodes.py", line 650, in accept
    return visitor.visit_class_def(self)
  File "/home/gregprice/w/mypy/env/lib/python3.4/site-packages/mypy/semanal.py", line 567, in visit_class_def
    defn.defs.accept(self)
  File "/home/gregprice/w/mypy/env/lib/python3.4/site-packages/mypy/nodes.py", line 715, in accept
    return visitor.visit_block(self)
  File "/home/gregprice/w/mypy/env/lib/python3.4/site-packages/mypy/semanal.py", line 1018, in visit_block
    self.accept(s)
  File "/home/gregprice/w/mypy/env/lib/python3.4/site-packages/mypy/semanal.py", line 2283, in accept
    node.accept(self)
  File "/home/gregprice/w/mypy/env/lib/python3.4/site-packages/mypy/nodes.py", line 462, in accept
    return visitor.visit_func_def(self)
  File "/home/gregprice/w/mypy/env/lib/python3.4/site-packages/mypy/semanal.py", line 322, in visit_func_def
    self.analyze_function(defn)
  File "/home/gregprice/w/mypy/env/lib/python3.4/site-packages/mypy/semanal.py", line 474, in analyze_function
    defn.type = self.anal_type(defn.type)
  File "/home/gregprice/w/mypy/env/lib/python3.4/site-packages/mypy/semanal.py", line 1043, in anal_type
    return t.accept(a)
  File "/home/gregprice/w/mypy/env/lib/python3.4/site-packages/mypy/types.py", line 496, in accept
    return visitor.visit_callable_type(self)
  File "/home/gregprice/w/mypy/env/lib/python3.4/site-packages/mypy/typeanal.py", line 189, in visit_callable_type
    return t.copy_modified(arg_types=self.anal_array(t.arg_types),
  File "/home/gregprice/w/mypy/env/lib/python3.4/site-packages/mypy/typeanal.py", line 259, in anal_array
    res.append(t.accept(self))
  File "/home/gregprice/w/mypy/env/lib/python3.4/site-packages/mypy/types.py", line 637, in accept
    return visitor.visit_tuple_type(self)
  File "/home/gregprice/w/mypy/env/lib/python3.4/site-packages/mypy/typeanal.py", line 203, in visit_tuple_type
    return TupleType(self.anal_array(t.items), fallback, t.line)
  File "/home/gregprice/w/mypy/env/lib/python3.4/site-packages/mypy/typeanal.py", line 259, in anal_array
    res.append(t.accept(self))
  File "/home/gregprice/w/mypy/env/lib/python3.4/site-packages/mypy/types.py", line 340, in accept
    return visitor.visit_type_var(self)
  File "/home/gregprice/w/mypy/env/lib/python3.4/site-packages/mypy/typeanal.py", line 186, in visit_type_var
    raise RuntimeError('TypeVarType is already analyzed')
RuntimeError: TypeVarType is already analyzed

*** INTERNAL ERROR ***

/tmp/foo.py:6: error: Internal error -- please report a bug at https://github.com/python/mypy/issues

This looks a lot like #685 originally did, but the repro there no longer crashes.

Spotted this in python/typeshed#236 -- this repro is a reduction of that code. The difference from the repros in #658 that no longer crash seems to be the method definition.

[elazarg]

It does not crash anymore. Instead It gives

error: 'T' is a type variable and only valid in type context

[ilevkivskyi]

Yes, this no longer crashes, and we have #685 to track the error. So that I am closing this.