Error with lambda in a line containing unicode identifiers

[lucaswiman]

.filter(lambda ...) fails when used on a line with unicode identifiers prior to the lambda declaration. For example:

from hypothesis import given
import hypothesis.strategies as st
π = 3.1415

@given(st.floats(min_value=-π, max_value=π).filter(lambda x: abs(x) > 1e-5))
def test_foo(bar):
    pass

This seems to be an off-by-two error with this example (source is 'mbda x: abs(x) > 1e-5))'), so I'm guessing it's probably that col_offset is computed on the bytes of the original file (UTF-8 encoded in this case):

(Pdb) orig_source.encode('utf-8')[lambda_ast.col_offset :]
b'lambda x: abs(x) > 1e-5))'

Testing conditions

Python 3.6 and 3.7; hypothesis==3.83.2, pytest==4.0.2.

Full error

$ python3.6 -m pytest test2.py --tb=short
pyenv-implicit: found multiple python3.6 in pyenv. Use version 3.6.
================================================================ test session starts ================================================================
platform darwin -- Python 3.6.5, pytest-4.0.2, py-1.7.0, pluggy-0.8.0
hypothesis profile 'default' -> database=DirectoryBasedExampleDatabase('/Users/lwiman/personal/nerdsniped/sine_testing/.hypothesis/examples')
rootdir: /Users/lwiman/personal/nerdsniped/sine_testing, inifile:
plugins: hypothesis-3.83.2
collected 1 item                                                                                                                                    

test2.py F                                                                                                                                    [100%]

===================================================================== FAILURES ======================================================================
_____________________________________________________________________ test_foo ______________________________________________________________________
../../../.pyenv/versions/3.6/lib/python3.6/site-packages/hypothesis/internal/conjecture/engine.py:174: in test_function
    self._test_function(data)
../../../.pyenv/versions/3.6/lib/python3.6/site-packages/hypothesis/core.py:625: in evaluate_test_data
    escalate_hypothesis_internal_error()
../../../.pyenv/versions/3.6/lib/python3.6/site-packages/hypothesis/core.py:605: in evaluate_test_data
    result = self.execute(data)
../../../.pyenv/versions/3.6/lib/python3.6/site-packages/hypothesis/core.py:574: in execute
    result = self.test_runner(data, run)
../../../.pyenv/versions/3.6/lib/python3.6/site-packages/hypothesis/executors.py:56: in default_new_style_executor
    return function(data)
../../../.pyenv/versions/3.6/lib/python3.6/site-packages/hypothesis/core.py:551: in run
    args, kwargs = data.draw(self.search_strategy)
../../../.pyenv/versions/3.6/lib/python3.6/site-packages/hypothesis/internal/conjecture/data.py:224: in draw
    return self.__draw(strategy, label=label)
../../../.pyenv/versions/3.6/lib/python3.6/site-packages/hypothesis/internal/conjecture/data.py:239: in __draw
    return strategy.do_draw(self)
../../../.pyenv/versions/3.6/lib/python3.6/site-packages/hypothesis/searchstrategy/collections.py:55: in do_draw
    return tuple(data.draw(e) for e in self.element_strategies)
../../../.pyenv/versions/3.6/lib/python3.6/site-packages/hypothesis/searchstrategy/collections.py:55: in <genexpr>
    return tuple(data.draw(e) for e in self.element_strategies)
../../../.pyenv/versions/3.6/lib/python3.6/site-packages/hypothesis/internal/conjecture/data.py:224: in draw
    return self.__draw(strategy, label=label)
../../../.pyenv/versions/3.6/lib/python3.6/site-packages/hypothesis/internal/conjecture/data.py:233: in __draw
    return strategy.do_draw(self)
../../../.pyenv/versions/3.6/lib/python3.6/site-packages/hypothesis/searchstrategy/strategies.py:576: in do_draw
    result = self.pack(data.draw(self.mapped_strategy))
../../../.pyenv/versions/3.6/lib/python3.6/site-packages/hypothesis/internal/conjecture/data.py:224: in draw
    return self.__draw(strategy, label=label)
../../../.pyenv/versions/3.6/lib/python3.6/site-packages/hypothesis/internal/conjecture/data.py:233: in __draw
    return strategy.do_draw(self)
../../../.pyenv/versions/3.6/lib/python3.6/site-packages/hypothesis/searchstrategy/lazy.py:156: in do_draw
    return data.draw(self.wrapped_strategy)
../../../.pyenv/versions/3.6/lib/python3.6/site-packages/hypothesis/internal/conjecture/data.py:224: in draw
    return self.__draw(strategy, label=label)
../../../.pyenv/versions/3.6/lib/python3.6/site-packages/hypothesis/internal/conjecture/data.py:233: in __draw
    return strategy.do_draw(self)
../../../.pyenv/versions/3.6/lib/python3.6/site-packages/hypothesis/searchstrategy/strategies.py:576: in do_draw
    result = self.pack(data.draw(self.mapped_strategy))
../../../.pyenv/versions/3.6/lib/python3.6/site-packages/hypothesis/internal/conjecture/data.py:224: in draw
    return self.__draw(strategy, label=label)
../../../.pyenv/versions/3.6/lib/python3.6/site-packages/hypothesis/internal/conjecture/data.py:233: in __draw
    return strategy.do_draw(self)
../../../.pyenv/versions/3.6/lib/python3.6/site-packages/hypothesis/searchstrategy/collections.py:55: in do_draw
    return tuple(data.draw(e) for e in self.element_strategies)
../../../.pyenv/versions/3.6/lib/python3.6/site-packages/hypothesis/searchstrategy/collections.py:55: in <genexpr>
    return tuple(data.draw(e) for e in self.element_strategies)
../../../.pyenv/versions/3.6/lib/python3.6/site-packages/hypothesis/internal/conjecture/data.py:224: in draw
    return self.__draw(strategy, label=label)
../../../.pyenv/versions/3.6/lib/python3.6/site-packages/hypothesis/internal/conjecture/data.py:233: in __draw
    return strategy.do_draw(self)
../../../.pyenv/versions/3.6/lib/python3.6/site-packages/hypothesis/searchstrategy/strategies.py:633: in do_draw
    data.note_event("Aborted test because unable to satisfy %r" % (self,))
../../../.pyenv/versions/3.6/lib/python3.6/site-packages/hypothesis/searchstrategy/strategies.py:610: in __repr__
    get_pretty_function_description(self.condition),
../../../.pyenv/versions/3.6/lib/python3.6/site-packages/hypothesis/internal/reflection.py:375: in get_pretty_function_description
    result = extract_lambda_source(f)
../../../.pyenv/versions/3.6/lib/python3.6/site-packages/hypothesis/internal/reflection.py:348: in extract_lambda_source
    source = source[source.index("lambda") :]
E   ValueError: substring not found

During handling of the above exception, another exception occurred:
test2.py:7: in test_foo
    ???
../../../.pyenv/versions/3.6/lib/python3.6/site-packages/hypothesis/internal/lazyformat.py:29: in __str__
    return self.__format_string % self.__args
../../../.pyenv/versions/3.6/lib/python3.6/site-packages/hypothesis/searchstrategy/strategies.py:610: in __repr__
    get_pretty_function_description(self.condition),
../../../.pyenv/versions/3.6/lib/python3.6/site-packages/hypothesis/internal/reflection.py:375: in get_pretty_function_description
    result = extract_lambda_source(f)
../../../.pyenv/versions/3.6/lib/python3.6/site-packages/hypothesis/internal/reflection.py:348: in extract_lambda_source
    source = source[source.index("lambda") :]
E   ValueError: substring not found
-------------------------------------------------------------------- Hypothesis ---------------------------------------------------------------------
You can add @seed(306900588268218898824024975885321058451) to this test or run pytest with --hypothesis-seed=306900588268218898824024975885321058451 to reproduce this failure.
============================================================= 1 failed in 0.32 seconds ==============================================================