python / python/cpython

some instructions in __annotate__ have incorrect code positions

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interpreter-core topic-typing type-bug
Dominant language
Python
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Description

Bug report

Bug description:

The following code shows the incorrect positions:

from dis import Bytecode

src = """\
22
333
__dataclass_fields__: ClassVar
"""

code = compile(src, "<string>", "exec")
print(code.co_consts)
annotate_code = code.co_consts[1]

for bc in Bytecode(annotate_code):
    print(bc.positions, bc.opname)

output (Python 3.14.0b3+):

(0, <code object __annotate__ at 0x7fcda674f940, file "<string>", line 1>, None)
Positions(lineno=1, end_lineno=1, col_offset=0, end_col_offset=0) RESUME       
Positions(lineno=1, end_lineno=1, col_offset=0, end_col_offset=2) LOAD_FAST_BORROW         # incorrect
Positions(lineno=1, end_lineno=1, col_offset=0, end_col_offset=2) LOAD_SMALL_INT           # incorrect
Positions(lineno=1, end_lineno=1, col_offset=0, end_col_offset=2) COMPARE_OP               # incorrect
Positions(lineno=1, end_lineno=1, col_offset=0, end_col_offset=2) POP_JUMP_IF_FALSE        # incorrect
Positions(lineno=1, end_lineno=1, col_offset=0, end_col_offset=2) NOT_TAKEN                # incorrect
Positions(lineno=1, end_lineno=1, col_offset=0, end_col_offset=2) LOAD_COMMON_CONSTANT     # incorrect
Positions(lineno=1, end_lineno=1, col_offset=0, end_col_offset=2) RAISE_VARARGS            # incorrect
Positions(lineno=1, end_lineno=1, col_offset=0, end_col_offset=2) BUILD_MAP                # incorrect
Positions(lineno=3, end_lineno=3, col_offset=0, end_col_offset=30) LOAD_SMALL_INT
Positions(lineno=3, end_lineno=3, col_offset=0, end_col_offset=30) LOAD_GLOBAL
Positions(lineno=3, end_lineno=3, col_offset=0, end_col_offset=30) CONTAINS_OP
Positions(lineno=3, end_lineno=3, col_offset=0, end_col_offset=30) POP_JUMP_IF_FALSE
Positions(lineno=3, end_lineno=3, col_offset=0, end_col_offset=30) NOT_TAKEN
Positions(lineno=3, end_lineno=3, col_offset=22, end_col_offset=30) LOAD_GLOBAL
Positions(lineno=3, end_lineno=3, col_offset=0, end_col_offset=30) COPY
Positions(lineno=3, end_lineno=3, col_offset=0, end_col_offset=30) LOAD_CONST
Positions(lineno=1, end_lineno=1, col_offset=0, end_col_offset=2) STORE_SUBSCR
Positions(lineno=1, end_lineno=1, col_offset=0, end_col_offset=2) RETURN_VALUE

The statements after RESUME have the position of the first ast-node in the module. I think it would be correct if they had the same code position as RESUME. I assume they are part of a general code that is part of every __annotate__ and are not associated with a specific ast-node.

I hope this can be fixed, as it makes it difficult for projects like executing to work with these code locations.

CPython versions tested on:

3.14

Operating systems tested on:

Linux

Linked PRs
  • gh-135814
  • gh-136543

Contributor guide

Open the contributing guide

First steps

  1. Read the whole issue, then the project's contributing guide.
  2. Comment on the issue to say you are picking it up — it saves two people doing the same work.
  3. Fork the repository and make your change on a branch.
  4. Open a pull request that references the issue number.

Research direction

Start with the supplied Python 3.14 reproducer using dis.Bytecode and inspect how code positions are assigned for annotate. Compare the instructions after RESUME with the expected position behavior described in the report; done means the general instructions no longer inherit the first AST node's position. Linked PRs gh-135814 and gh-136543 indicate that work is already underway.

Written by the indexing model from the issue text.

Assessment

Tech stack
python
Domain
compilers
Issue type
Bug
Difficulty
4/5
Estimated time
3-5 days
Activity status
Stale
Clarity
Mostly clear
Newbie friendliness
25/100

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