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overwriting None from Tuple[AnyStr]'s only item causes PartialType-related crash #1587

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overwriting None from Tuple[AnyStr]'s only item causes PartialType-related crash#1587
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ddfisher
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crashpriority-0-high

Description

@ddfisher
ddfisher
opened on May 27, 2016
import os.path

x = None
if 0:
    _, x = os.path.split("blah")

results in:

Traceback (most recent call last):
  File "/usr/local/bin/mypy", line 6, in <module>
    main(__file__)
  File "/usr/local/lib/python3.5/site-packages/mypy/main.py", line 54, in main
    res = type_check_only(sources, bin_dir, options)
  File "/usr/local/lib/python3.5/site-packages/mypy/main.py", line 102, in type_check_only
    python_path=options.python_path)
  File "/usr/local/lib/python3.5/site-packages/mypy/build.py", line 209, in build
    dispatch(sources, manager)
  File "/usr/local/lib/python3.5/site-packages/mypy/build.py", line 1325, in dispatch
    process_graph(graph, manager)
  File "/usr/local/lib/python3.5/site-packages/mypy/build.py", line 1456, in process_graph
    process_stale_scc(graph, scc)
  File "/usr/local/lib/python3.5/site-packages/mypy/build.py", line 1486, in process_stale_scc
    graph[id].type_check()
  File "/usr/local/lib/python3.5/site-packages/mypy/build.py", line 1305, in type_check
    manager.type_checker.visit_file(self.tree, self.xpath)
  File "/usr/local/lib/python3.5/site-packages/mypy/checker.py", line 424, in visit_file
    self.accept(d)
  File "/usr/local/lib/python3.5/site-packages/mypy/checker.py", line 465, in accept
    typ = node.accept(self)
  File "/usr/local/lib/python3.5/site-packages/mypy/nodes.py", line 862, in accept
    return visitor.visit_if_stmt(self)
  File "/usr/local/lib/python3.5/site-packages/mypy/checker.py", line 1661, in visit_if_stmt
    self.accept(b)
  File "/usr/local/lib/python3.5/site-packages/mypy/checker.py", line 465, in accept
    typ = node.accept(self)
  File "/usr/local/lib/python3.5/site-packages/mypy/nodes.py", line 715, in accept
    return visitor.visit_block(self)
  File "/usr/local/lib/python3.5/site-packages/mypy/checker.py", line 1149, in visit_block
    self.accept(s)
  File "/usr/local/lib/python3.5/site-packages/mypy/checker.py", line 465, in accept
    typ = node.accept(self)
  File "/usr/local/lib/python3.5/site-packages/mypy/nodes.py", line 753, in accept
    return visitor.visit_assignment_stmt(self)
  File "/usr/local/lib/python3.5/site-packages/mypy/checker.py", line 1158, in visit_assignment_stmt
    self.check_assignment(s.lvalues[-1], s.rvalue, s.type is None)
  File "/usr/local/lib/python3.5/site-packages/mypy/checker.py", line 1175, in check_assignment
    infer_lvalue_type)
  File "/usr/local/lib/python3.5/site-packages/mypy/checker.py", line 1244, in check_assignment_to_multiple_lvalues
    self.check_multi_assignment(lvalues, rvalue, context, infer_lvalue_type)
  File "/usr/local/lib/python3.5/site-packages/mypy/checker.py", line 1277, in check_multi_assignment
    context, undefined_rvalue, infer_lvalue_type)
  File "/usr/local/lib/python3.5/site-packages/mypy/checker.py", line 1297, in check_multi_assignment_from_tuple
    rvalue_type = cast(TupleType, self.accept(rvalue, lvalue_type))
  File "/usr/local/lib/python3.5/site-packages/mypy/checker.py", line 465, in accept
    typ = node.accept(self)
  File "/usr/local/lib/python3.5/site-packages/mypy/nodes.py", line 1185, in accept
    return visitor.visit_call_expr(self)
  File "/usr/local/lib/python3.5/site-packages/mypy/checker.py", line 1997, in visit_call_expr
    return self.expr_checker.visit_call_expr(e)
  File "/usr/local/lib/python3.5/site-packages/mypy/checkexpr.py", line 141, in visit_call_expr
    return self.check_call_expr_with_callee_type(callee_type, e)
  File "/usr/local/lib/python3.5/site-packages/mypy/checkexpr.py", line 192, in check_call_expr_with_callee_type
    e.arg_names, callable_node=e.callee)[0]
  File "/usr/local/lib/python3.5/site-packages/mypy/checkexpr.py", line 230, in check_call
    callee, context)
  File "/usr/local/lib/python3.5/site-packages/mypy/checkexpr.py", line 370, in infer_function_type_arguments_using_context
    args = infer_type_arguments(callable.type_var_ids(), ret_type, erased_ctx)
  File "/usr/local/lib/python3.5/site-packages/mypy/infer.py", line 43, in infer_type_arguments
    return solve_constraints(type_var_ids, constraints)
  File "/usr/local/lib/python3.5/site-packages/mypy/solve.py", line 50, in solve_constraints
    top = meet_types(top, c.target)
  File "/usr/local/lib/python3.5/site-packages/mypy/meet.py", line 22, in meet_types
    return t.accept(TypeMeetVisitor(s))
  File "/usr/local/lib/python3.5/site-packages/mypy/types.py", line 763, in accept
    return visitor.visit_partial_type(self)
  File "/usr/local/lib/python3.5/site-packages/mypy/meet.py", line 208, in visit_partial_type
    assert False, 'Internal error'
AssertionError: Internal error

*** INTERNAL ERROR ***

test.py:5: error: Internal error -- please report a bug at https://github.com/python/mypy/issues

NOTE: you can use "mypy --pdb ..." to drop into the debugger when this happens.

We might want to fix this before releasing.

Activity

  1. gvanrossum
    added
    crash
    on May 27, 2016

  2. ddfisher commented on May 27, 2016

    @ddfisher
    ddfisher
    on May 27, 2016
    CollaboratorAuthor

    Here's a simpler repro which produces a similar error:

    from typing import AnyStr, Tuple

def split() -> Tuple[int, AnyStr]: ...
x = None
_, x = split()

  3. gvanrossum commented on May 27, 2016

    @gvanrossum
    gvanrossum
    on May 27, 2016 via email
    Member

  4. euresti commented on Jun 2, 2016

    @euresti
    euresti
    on Jun 2, 2016
    Contributor

    I can hit this using mkstemp with an overload that returns AnyStr. It only happens if the variable is defined as None beforehand and not annotated.

    import tempfile
from typing import Any

def fine_test():
    # type: () -> Any
    # Annotated
    hash_set_path = None  # type: Any
    try:
        fd, hash_set_path = tempfile.mkstemp(dir=u"blah")
    except Exception:
        print("Ack moving on")
    return hash_set_path

def fine_test2():
    # type: () -> Any
    # Not annotated but not overloaded
    hash_set_path = None
    try:
        fd, hash_set_path = tempfile.mkstemp()
    except Exception:
        print("Ack moving on")
    return hash_set_path

def fine_test3():
    # type: () -> Any
    # Variable not defined beforehand
    try:
        fd, hash_set_path = tempfile.mkstemp()
    except Exception:
        print("Ack moving on")
        return None
    return hash_set_path

def crashes_test():
    # type: () -> Any
    hash_set_path = None
    try:
        fd, hash_set_path = tempfile.mkstemp(dir=u"blah")
    except Exception:
        print("Ack moving on")
    return hash_set_path
  5. ddfisher
    self-assigned this
    on Jun 3, 2016
  6. gvanrossum
    added this to the milestone on Jul 8, 2016

  7. gvanrossum commented on Oct 10, 2016

    @gvanrossum
    gvanrossum
    on Oct 10, 2016
    Member

    Simpler repro (similar to #1587 (comment) but without the confusing "output-only type var"):

    from typing import AnyStr, Tuple
def f(a: AnyStr) -> Tuple[AnyStr]: pass
x = None
(x,) = f('')
  8. gvanrossum
    changed the title [-]simple construct causes PartialType-related crash[/-] [+]overwriting None from Tuple[AnyStr]'s only item causes PartialType-related crash[/+] on Oct 10, 2016
  9. gvanrossum
    added
    priority-0-high
    on Jan 6, 2017
  10. gvanrossum
    closed this as completedin #2772on Feb 6, 2017
  11. gvanrossum
    added a commit that references this issue on Feb 6, 2017

    Fix crash when assigning to partial type (#2772)

    351d2af
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