The AST for dict and set displays has the lineno of the first value

[PCManticore]

BPO	25131
Nosy	@terryjreedy, @vstinner, @benjaminp, @PCManticore, @NeilGirdhar

^{Note: these values reflect the state of the issue at the time it was migrated and might not reflect the current state.}

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GitHub fields:

assignee = None
closed_at = <Date 2015-09-26.05:46:24.811>
created_at = <Date 2015-09-15.18:28:25.885>
labels = ['type-bug', 'library']
title = 'The AST for dict and set displays has the lineno of the first value'
updated_at = <Date 2015-09-26.05:46:24.809>
user = 'https://github.com/PCManticore'

bugs.python.org fields:

activity = <Date 2015-09-26.05:46:24.809>
actor = 'python-dev'
assignee = 'none'
closed = True
closed_date = <Date 2015-09-26.05:46:24.811>
closer = 'python-dev'
components = ['Library (Lib)']
creation = <Date 2015-09-15.18:28:25.885>
creator = 'Claudiu.Popa'
dependencies = []
files = []
hgrepos = []
issue_num = 25131
keywords = ['3.5regression']
message_count = 4.0
messages = ['250790', '250793', '251041', '251636']
nosy_count = 6.0
nosy_names = ['terry.reedy', 'vstinner', 'benjamin.peterson', 'Claudiu.Popa', 'python-dev', 'NeilGirdhar']
pr_nums = []
priority = 'normal'
resolution = 'fixed'
stage = 'resolved'
status = 'closed'
superseder = None
type = 'behavior'
url = 'https://bugs.python.org/issue25131'
versions = ['Python 3.5', 'Python 3.6']

[PCManticore]

Hi,

In Python 3.5, the lineno for dict and set display ASTs is the line number of the first value, not the line number of the display character, as it was until 3.5. Here's an example:

  from ast import parse
  module = parse('''{
           '1':'2',
  }
  ''')
  dict_display = module.body[0].value
  print(dict_display.lineno)

I don't seem to find anything related to this in the documentation, but I presume this is a side effect of the new parser changes. It would nice to have this fixed or at least documented.

[vstinner]

Using hg bisect, I found the revision a65f685ba8c0:

changeset: 95886:a65f685ba8c0
user: Benjamin Peterson <benjamin@python.org>
date: Tue May 05 20:16:41 2015 -0400
files: Grammar/Grammar Include/Python-ast.h Include/dictobject.h Include/opcode.h Lib/importlib/_bootstrap_external.py Lib/opcode.py Lib/test/test_ast.py Lib/test/test_extcall.py Lib/test/test_grammar.py Lib/test/test_parser.py Lib/test/test_syntax.py Lib/test/test_unpack_ex.py Misc/ACKS Misc/NEWS Modules/parsermodule.c Objects/dictobject.c Parser/Python.asdl Python/Python-ast.c Python/ast.c Python/ceval.c Python/compile.c Python/graminit.c Python/importlib_external.h Python/opcode_targets.h Python/symtable.c Tools/parser/unparse.py
description:
PEP-448: additional unpacking generalizations (closes bpo-2292)

Patch by Neil Girdhar.

[terryjreedy]

A fix should include a new ast test, such as
self.assertEqual(parse("{\n1:2}").body[0].value.lineno, 1)
I verified that the equivalent assert passes on 3.4.3, fails on 3.5.0.

[python-dev]

New changeset 4f14afc959df by Benjamin Peterson in branch '3.5':
make opening brace of container literals and comprehensions correspond to the line number and col offset of the AST node (closes bpo-25131)
https://hg.python.org/cpython/rev/4f14afc959df

New changeset 9d895c09c08a by Benjamin Peterson in branch 'default':
merge 3.5 (bpo-25131)
https://hg.python.org/cpython/rev/9d895c09c08a