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Description
We perform some manual fiddling with positions for attribute lookups at afewdifferentpoints in the compiler. However, the extended position information for these locations can be nonsensical in some edge cases. Here is one (admittedly contrived) example:
>>>deffoo():... (bar....baz)...>>>forinstructionindis.get_instructions(foo):...print(instruction.positions,instruction.opname)...Positions(lineno=1,end_lineno=1,col_offset=0,end_col_offset=0)RESUMEPositions(lineno=2,end_lineno=2,col_offset=5,end_col_offset=8)LOAD_GLOBALPositions(lineno=3,end_lineno=3,col_offset=5,end_col_offset=3)LOAD_ATTRPositions(lineno=3,end_lineno=3,col_offset=5,end_col_offset=3)POP_TOPPositions(lineno=3,end_lineno=3,col_offset=5,end_col_offset=3)LOAD_CONSTPositions(lineno=3,end_lineno=3,col_offset=5,end_col_offset=3)RETURN_VALUE
The last four instructions claim to be located on line 3, starting with at column 5 and ending at column 3 (which doesn't make sense).
A slight variation (using a method call) is even weirder:
>>>deffoo():... (bar....baz(... ))...>>>forinstructionindis.get_instructions(foo):...print(instruction.positions,instruction.opname)...Positions(lineno=1,end_lineno=1,col_offset=0,end_col_offset=0)RESUMEPositions(lineno=2,end_lineno=2,col_offset=5,end_col_offset=8)LOAD_GLOBALPositions(lineno=3,end_lineno=3,col_offset=None,end_col_offset=None)LOAD_ATTRPositions(lineno=3,end_lineno=4,col_offset=None,end_col_offset=1)CALLPositions(lineno=3,end_lineno=4,col_offset=None,end_col_offset=1)POP_TOPPositions(lineno=3,end_lineno=4,col_offset=None,end_col_offset=1)LOAD_CONSTPositions(lineno=3,end_lineno=4,col_offset=None,end_col_offset=1)RETURN_VALUE
Here thecol_offset is totally nonexistent, even in cases whereend_col_offset is set! I suspect that this may be because the column math just happened to underflow the valid column range (>=0) and end up at-1, which is a special value we use to mean "missing".