Commit Graph

209 Commits

Author SHA1 Message Date
Victor Stinner d36d6a9c18
bpo-43244: Remove Yield macro from pycore_ast.h (GH-25243)
* pycore_ast.h no longer defines the Yield macro.
* Fix a compiler warning on Windows: "warning C4005: 'Yield': macro
  redefinition".
* Python-ast.c now defines directly functions with their real
  _Py_xxx() name, rather than xxx().
* Remove "#undef Yield" in C files including pycore_ast.h.
2021-04-07 13:01:09 +02:00
Victor Stinner 8370e07e1e
bpo-43244: Remove the pyarena.h header (GH-25007)
Remove the pyarena.h header file with functions:

* PyArena_New()
* PyArena_Free()
* PyArena_Malloc()
* PyArena_AddPyObject()

These functions were undocumented, excluded from the limited C API,
and were only used internally by the compiler.

Add pycore_pyarena.h header. Rename functions:

* PyArena_New() => _PyArena_New()
* PyArena_Free() => _PyArena_Free()
* PyArena_Malloc() => _PyArena_Malloc()
* PyArena_AddPyObject() => _PyArena_AddPyObject()
2021-03-24 02:23:01 +01:00
Victor Stinner 94faa0724f
bpo-43244: Remove ast.h, asdl.h, Python-ast.h headers (GH-24933)
These functions were undocumented and excluded from the limited C
API.

Most names defined by these header files were not prefixed by "Py"
and so could create names conflicts. For example, Python-ast.h
defined a "Yield" macro which was conflict with the "Yield" name used
by the Windows <winbase.h> header.

Use the Python ast module instead.

* Move Include/asdl.h to Include/internal/pycore_asdl.h.
* Move Include/Python-ast.h to Include/internal/pycore_ast.h.
* Remove ast.h header file.
* pycore_symtable.h no longer includes Python-ast.h.
2021-03-23 20:47:40 +01:00
Victor Stinner e0bf70d08c
bpo-43244: Fix test_peg_generator for PyAST_Validate() (GH-24912)
test_peg_generator now defines _Py_TEST_PEGEN macro when building C
code to not call PyAST_Validate() in Parser/pegen.c. Moreover, it
defines Py_BUILD_CORE_MODULE macro to get access to the internal
C API.

Remove "global_ast_state" from Python-ast.c when it's built by
test_peg_generator: always get the AST state from the current interpreter.
2021-03-18 02:46:06 +01:00
Victor Stinner b4536e1c6a
bpo-43244: Rename pycore_ast.h to pycore_ast_state.h (GH-24907) 2021-03-17 23:11:03 +01:00
Brandt Bucher 145bf269df
bpo-42128: Structural Pattern Matching (PEP 634) (GH-22917)
Co-authored-by: Guido van Rossum <guido@python.org>
Co-authored-by: Talin <viridia@gmail.com>
Co-authored-by: Pablo Galindo <pablogsal@gmail.com>
2021-02-26 14:51:55 -08:00
Victor Stinner 18ce7f1d0a
bpo-1635741: _ast uses PyModule_AddObjectRef() (GH-23146)
Replace PyModule_AddObject() with PyModule_AddObjectRef() in the _ast
module (Python-ast.c).
2020-11-04 16:37:07 +01:00
Victor Stinner fd957c124c
bpo-41796: Call _PyAST_Fini() earlier to fix a leak (GH-23131)
Call _PyAST_Fini() on all interpreters, not only on the main
interpreter. Also, call it ealier to fix a reference leak.

Python types contain a reference to themselves in in their
PyTypeObject.tp_mro member. _PyAST_Fini() must called before the last
GC collection to destroy AST types.

_PyInterpreterState_Clear() now calls _PyAST_Fini(). It now also
calls _PyWarnings_Fini() on subinterpeters, not only on the main
interpreter.

Add an assertion in AST init_types() to ensure that the _ast module
is no longer used after _PyAST_Fini() has been called.
2020-11-03 18:07:15 +01:00
Victor Stinner 5cf4782a26
bpo-41796: Make _ast module state per interpreter (GH-23024)
The ast module internal state is now per interpreter.

* Rename "astmodulestate" to "struct ast_state"
* Add pycore_ast.h internal header: the ast_state structure is now
  declared in pycore_ast.h.
* Add PyInterpreterState.ast (struct ast_state)
* Remove get_ast_state()
* Rename get_global_ast_state() to get_ast_state()
* PyAST_obj2mod() now handles get_ast_state() failures
2020-11-02 22:03:28 +01:00
Pablo Galindo a5634c4067
bpo-41746: Add type information to asdl_seq objects (GH-22223)
* Add new capability to the PEG parser to type variable assignments. For instance:
```
       | a[asdl_stmt_seq*]=';'.small_stmt+ [';'] NEWLINE { a }
```

* Add new sequence types from the asdl definition (automatically generated)
* Make `asdl_seq` type a generic aliasing pointer type.
* Create a new `asdl_generic_seq` for the generic case using `void*`.
* The old `asdl_seq_GET`/`ast_seq_SET` macros now are typed.
* New `asdl_seq_GET_UNTYPED`/`ast_seq_SET_UNTYPED` macros for dealing with generic sequences.
* Changes all possible `asdl_seq` types to use specific versions everywhere.
2020-09-16 19:42:00 +01:00
Victor Stinner e5fbe0cbd4
bpo-41631: _ast module uses again a global state (#21961)
Partially revert commit ac46eb4ad6662cf6d771b20d8963658b2186c48c:
"bpo-38113: Update the Python-ast.c generator to PEP384 (gh-15957)".

Using a module state per module instance is causing subtle practical
problems.

For example, the Mercurial project replaces the __import__() function
to implement lazy import, whereas Python expected that "import _ast"
always return a fully initialized _ast module.

Add _PyAST_Fini() to clear the state at exit.

The _ast module has no state (set _astmodule.m_size to 0). Remove
astmodule_traverse(), astmodule_clear() and astmodule_free()
functions.
2020-09-15 18:03:34 +02:00
Victor Stinner 1f76453173
bpo-41204: Fix compiler warning in ast_type_init() (GH-21307) 2020-07-04 23:18:15 +02:00
Victor Stinner b1cc6ba73a
bpo-41194: Convert _ast extension to PEP 489 (GH-21293)
Convert the _ast extension module to PEP 489 "Multiphase
initialization". Replace the global _ast state with a module state.
2020-07-03 20:01:46 +02:00
Victor Stinner 91e1bc18bd
bpo-41194: The _ast module cannot be loaded more than once (GH-21290)
Fix a crash in the _ast module: it can no longer be loaded more than
once. It now uses a global state rather than a module state.

* Move _ast module state: use a global state instead.
* Set _astmodule.m_size to -1, so the extension cannot be loaded more
  than once.
2020-07-03 14:15:53 +02:00
Victor Stinner 74419f0c64
bpo-41194: Pass module state in Python-ast.c (GH-21284)
Rework asdl_c.py to pass the module state to functions in
Python-ast.c, instead of using astmodulestate_global.

Handle also PyState_AddModule() failure in init_types().
2020-07-03 11:35:37 +02:00
Pablo Galindo 1cf15af9a6 bpo-40217: Ensure Py_VISIT(Py_TYPE(self)) is always called for PyType_FromSpec types (reverts GH-19414) (GH-20264)
Heap types now always visit the type in tp_traverse. See added docs for details.

This reverts commit 0169d3003b.

Automerge-Triggered-By: @encukou
2020-05-27 02:03:38 -07:00
Rémi Lapeyre c73914a562
bpo-36290: Fix keytword collision handling in AST node constructors (GH-12382) 2020-05-24 22:12:57 +01:00
Batuhan Taskaya 091951a67c
bpo-40528: Improve and clear several aspects of the ASDL definition code for the AST (GH-19952) 2020-05-06 15:29:32 +01:00
Victor Stinner 4a21e57fe5
bpo-40268: Remove unused structmember.h includes (GH-19530)
If only offsetof() is needed: include stddef.h instead.

When structmember.h is used, add a comment explaining that
PyMemberDef is used.
2020-04-15 02:35:41 +02:00
Pablo Galindo 168660b547
bpo-40141: Add line and column information to ast.keyword nodes (GH-19283) 2020-04-02 00:47:39 +01:00
Serhiy Storchaka bace59d8b8
bpo-39999: Improve compatibility of the ast module. (GH-19056)
* Re-add removed classes Suite, slice, Param, AugLoad and AugStore.
* Add docstrings for dummy classes.
* Add docstrings for attribute aliases.
* Set __module__ to "ast" instead of "_ast".
2020-03-22 20:33:34 +02:00
Serhiy Storchaka 6b97598fb6
bpo-39988: Remove ast.AugLoad and ast.AugStore node classes. (GH-19038) 2020-03-17 23:41:08 +02:00
Batuhan Taşkaya 4ab362cec6
bpo-39638: Keep ASDL signatures in the AST nodes (GH-18515) 2020-03-16 10:12:53 +02:00
Batuhan Taşkaya 8689209e03
bpo-39969: Remove ast.Param node class as is no longer used (GH-19020) 2020-03-15 19:32:17 +00:00
Serhiy Storchaka 13d52c2686
bpo-34822: Simplify AST for subscription. (GH-9605)
* Remove the slice type.
* Make Slice a kind of the expr type instead of the slice type.
* Replace ExtSlice(slices) with Tuple(slices, Load()).
* Replace Index(value) with a value itself.

All non-terminal nodes in AST for expressions are now of the expr type.
2020-03-10 18:52:34 +02:00
Serhiy Storchaka b7e9525f9c
bpo-36287: Make ast.dump() not output optional fields and attributes with default values. (GH-18843)
The default values for optional fields and attributes of AST nodes are now set
as class attributes (e.g. Constant.kind is set to None).
2020-03-10 00:07:47 +02:00
Batuhan Taşkaya d82e469048
bpo-39639: Remove the AST "Suite" node and associated code (GH-18513)
The AST "Suite" node is no longer used and it can be removed from the ASDL definition and related structures (compiler, visitors, ...).

Co-Authored-By: Victor Stinner <vstinner@python.org>
Co-authored-by: Brett Cannon <54418+brettcannon@users.noreply.github.com>
Co-authored-by: Pablo Galindo <Pablogsal@gmail.com>
2020-03-04 16:16:46 +00:00
Brandt Bucher d2f9667264
bpo-38823: Fix refleaks in _ast initialization error path (GH-17276) 2020-02-06 15:45:46 +01:00
Max Bernstein bdac32e9fe closes bpo-38648: Remove double tp_free slot in Python-ast.c. (GH-17002)
This looks like a typo due to copy-paste.
2019-10-30 18:08:06 -07:00
Dong-hee Na a05fcd3c7a bpo-38425: Fix ‘res’ may be used uninitialized warning (GH-16688) 2019-10-10 09:41:26 +02:00
Eddie Elizondo 3368f3c6ae bpo-38140: Make dict and weakref offsets opaque for C heap types (#16076)
* Make dict and weakref offsets opaque for C heap types

* Add news
2019-09-19 17:29:05 +01:00
Eddie Elizondo 0247e80f3c Fix leaks in Python-ast.c (#16127) 2019-09-14 14:38:17 +01:00
Dino Viehland ac46eb4ad6 bpo-38113: Update the Python-ast.c generator to PEP384 (gh-15957)
Summary: This mostly migrates Python-ast.c to PEP384 and removes all statics from the whole file. This modifies the generator itself that generates the Python-ast.c. It leaves in the usage of _PyObject_LookupAttr even though it's not fully PEP384 compatible (this could always be shimmed in by anyone who needs it).
2019-09-11 18:16:34 +01:00
Serhiy Storchaka 43c9731334 bpo-38083: Minor improvements in asdl_c.py and Python-ast.c. (GH-15824)
* Use the const qualifier for constant C strings.
* Intern field and attribute names.
* Temporary incref a borrowed reference to a list item.
2019-09-10 03:02:30 -07:00
Pablo Galindo cd6e83b481 bpo-37593: Swap the positions of posonlyargs and args in the constructor of ast.parameters nodes (GH-14778)
https://bugs.python.org/issue37593
2019-07-14 16:32:18 -07:00
Victor Stinner 022ac0a497
bpo-37253: Remove PyAST_obj2mod_ex() function (GH-14020)
PyAST_obj2mod_ex() is similar to PyAST_obj2mod() with an additional
'feature_version' parameter which is unused.
2019-06-13 09:18:45 +02:00
Jeroen Demeyer 530f506ac9 bpo-36974: tp_print -> tp_vectorcall_offset and tp_reserved -> tp_as_async (GH-13464)
Automatically replace
tp_print -> tp_vectorcall_offset
tp_compare -> tp_as_async
tp_reserved -> tp_as_async
2019-05-30 19:13:39 -07:00
Eric V. Smith 6f6ff8a565
bpo-37050: Remove expr_text from FormattedValue ast node, use Constant node instead (GH-13597)
When using the "=" debug functionality of f-strings, use another Constant node (or a merged constant node) instead of adding expr_text to the FormattedValue node.
2019-05-27 15:31:52 -04:00
Steve Dower b82e17e626
bpo-36842: Implement PEP 578 (GH-12613)
Adds sys.audit, sys.addaudithook, io.open_code, and associated C APIs.
2019-05-23 08:45:22 -07:00
Michael J. Sullivan 933e1509ec bpo-36878: Track extra text added to 'type: ignore' in the AST (GH-13479)
GH-13238 made extra text after a # type: ignore accepted by the parser.
This finishes the job and actually plumbs the extra text through the
parser and makes it available in the AST.
2019-05-22 15:54:20 +01:00
Matthias Bussonnier 565b4f1ac7 bpo-34616: Add PyCF_ALLOW_TOP_LEVEL_AWAIT to allow top-level await (GH-13148)
Co-Authored-By: Yury Selivanov <yury@magic.io>
2019-05-21 16:12:02 -04:00
Eric V. Smith 9a4135e939
bpo-36817: Add f-string debugging using '='. (GH-13123)
If a "=" is specified a the end of an f-string expression, the f-string will evaluate to the text of the expression, followed by '=', followed by the repr of the value of the expression.
2019-05-08 16:28:48 -04:00
Pablo Galindo 8c77b8cb91
bpo-36540: PEP 570 -- Implementation (GH-12701)
This commit contains the implementation of PEP570: Python positional-only parameters.

* Update Grammar/Grammar with new typedarglist and varargslist

* Regenerate grammar files

* Update and regenerate AST related files

* Update code object

* Update marshal.c

* Update compiler and symtable

* Regenerate importlib files

* Update callable objects

* Implement positional-only args logic in ceval.c

* Regenerate frozen data

* Update standard library to account for positional-only args

* Add test file for positional-only args

* Update other test files to account for positional-only args

* Add News entry

* Update inspect module and related tests
2019-04-29 13:36:57 +01:00
Guido van Rossum 10f8ce6688 bpo-36280: Add Constant.kind field (GH-12295)
The value is a string for string and byte literals, None otherwise.
It is 'u' for u"..." literals, 'b' for b"..." literals, '' for "..." literals.
The 'r' (raw) prefix is ignored.
Does not apply to f-strings.

This appears sufficient to make mypy capable of using the stdlib ast module instead of typed_ast (assuming a mypy patch I'm working on).

WIP: I need to make the tests pass. @ilevkivskyi @serhiy-storchaka 



https://bugs.python.org/issue36280
2019-03-13 13:00:46 -07:00
Guido van Rossum 495da29225 bpo-35975: Support parsing earlier minor versions of Python 3 (GH-12086)
This adds a `feature_version` flag to `ast.parse()` (documented) and `compile()` (hidden) that allow tweaking the parser to support older versions of the grammar. In particular if `feature_version` is 5 or 6, the hacks for the `async` and `await` keyword from PEP 492 are reinstated. (For 7 or higher, these are unconditionally treated as keywords, but they are still special tokens rather than `NAME` tokens that the parser driver recognizes.)



https://bugs.python.org/issue35975
2019-03-07 12:38:08 -08:00
Serhiy Storchaka d8b3a98c90
bpo-36187: Remove NamedStore. (GH-12167)
NamedStore has been replaced with Store. The difference between
NamedStore and Store is handled when precess the NamedExpr node
one level upper.
2019-03-05 20:42:06 +02:00
Guido van Rossum 3a32e3bf88
bpo-35766 follow-up: Kill half-support for FunctionType in PyAST_obj2mod (#11714)
See 229874c612 (r252631862)

https://bugs.python.org/issue35766
2019-02-01 11:37:34 -08:00
Guido van Rossum dcfcd146f8 bpo-35766: Merge typed_ast back into CPython (GH-11645) 2019-01-31 12:40:27 +01:00
Emily Morehouse 8f59ee01be
bpo-35224: PEP 572 Implementation (#10497)
* Add tokenization of :=
- Add token to Include/token.h. Add token to documentation in Doc/library/token.rst.
- Run `./python Lib/token.py` to regenerate Lib/token.py.
- Update Parser/tokenizer.c: add case to handle `:=`.

* Add initial usage of := in grammar.

* Update Python.asdl to match the grammar updates. Regenerated Include/Python-ast.h and Python/Python-ast.c

* Update AST and compiler files in Python/ast.c and Python/compile.c. Basic functionality, this isn't scoped properly

* Regenerate Lib/symbol.py using `./python Lib/symbol.py`

* Tests - Fix failing tests in test_parser.py due to changes in token numbers for internal representation

* Tests - Add simple test for := token

* Tests - Add simple tests for named expressions using expr and suite

* Tests - Update number of levels for nested expressions to prevent stack overflow

* Update symbol table to handle NamedExpr

* Update Grammar to allow assignment expressions in if statements.
Regenerate Python/graminit.c accordingly using `make regen-grammar`

* Tests - Add additional tests for named expressions in RoundtripLegalSyntaxTestCase, based on examples and information directly from PEP 572

Note: failing tests are currently commented out (4 out of 24 tests currently fail)

* Tests - Add temporary syntax test failure tests in test_parser.py

Note: There is an outstanding TODO for this -- syntax tests need to be
moved to a different file (presumably test_syntax.py), but this is
covering what needs to be tested at the moment, and it's more convenient
to run a single test for the time being

* Add support for allowing assignment expressions as function argument annotations. Uncomment tests for these cases because they all pass now!

* Tests - Move existing syntax tests out of test_parser.py and into test_named_expressions.py. Refactor syntax tests to use unittest

* Add TargetScopeError exception to extend SyntaxError

Note: This simply creates the TargetScopeError exception, it is not yet
used anywhere

* Tests - Update tests per PEP 572

Continue refactoring test suite:
The named expression test suite now checks for any invalid cases that
throw exceptions (no longer limited to SyntaxErrors), assignment tests
to ensure that variables are properly assigned, and scope tests to
ensure that variable availability and values are correct

Note:
- There are still tests that are marked to skip, as they are not yet
implemented
- There are approximately 300 lines of the PEP that have not yet been
addressed, though these may be deferred

* Documentation - Small updates to XXX/todo comments

- Remove XXX from child description in ast.c
- Add comment with number of previously supported nested expressions for
3.7.X in test_parser.py

* Fix assert in seq_for_testlist()

* Cleanup - Denote "Not implemented -- No keyword args" on failing test case. Fix PEP8 error for blank lines at beginning of test classes in test_parser.py

* Tests - Wrap all file opens in `with...as` to ensure files are closed

* WIP: handle f(a := 1)

* Tests and Cleanup - No longer skips keyword arg test. Keyword arg test now uses a simpler test case and does not rely on an external file. Remove print statements from ast.c

* Tests - Refactor last remaining test case that relied on on external file to use a simpler test case without the dependency

* Tests - Add better description of remaning skipped tests. Add test checking scope when using assignment expression in a function argument

* Tests - Add test for nested comprehension, testing value and scope. Fix variable name in skipped comprehension scope test

* Handle restriction of LHS for named expressions - can only assign to LHS of type NAME. Specifically, restrict assignment to tuples

This adds an alternative set_context specifically for named expressions,
set_namedexpr_context. Thus, context is now set differently for standard
assignment versus assignment for named expressions in order to handle
restrictions.

* Tests - Update negative test case for assigning to lambda to match new error message. Add negative test case for assigning to tuple

* Tests - Reorder test cases to group invalid syntax cases and named assignment target errors

* Tests - Update test case for named expression in function argument - check that result and variable are set correctly

* Todo - Add todo for TargetScopeError based on Guido's comment (2b3acd37bd (r30472562))

* Tests - Add named expression tests for assignment operator in function arguments

Note: One of two tests are skipped, as function arguments are currently treating
an assignment expression inside of parenthesis as one child, which does
not properly catch the named expression, nor does it count arguments
properly

* Add NamedStore to expr_context. Regenerate related code with `make regen-ast`

* Add usage of NamedStore to ast_for_named_expr in ast.c. Update occurances of checking for Store to also handle NamedStore where appropriate

* Add ste_comprehension to _symtable_entry to track if the namespace is a comprehension. Initialize ste_comprehension to 0. Set set_comprehension to 1 in symtable_handle_comprehension

* s/symtable_add_def/symtable_add_def_helper. Add symtable_add_def to handle grabbing st->st_cur and passing it to symtable_add_def_helper. This now allows us to call the original code from symtable_add_def by instead calling symtable_add_def_helper with a different ste.

* Refactor symtable_record_directive to take lineno and col_offset as arguments instead of stmt_ty. This allows symtable_record_directive to be used for stmt_ty and expr_ty

* Handle elevating scope for named expressions in comprehensions.

* Handle error for usage of named expression inside a class block

* Tests - No longer skip scope tests. Add additional scope tests

* Cleanup - Update error message for named expression within a comprehension within a class. Update comments. Add assert for symtable_extend_namedexpr_scope to validate that we always find at least a ModuleScope if we don't find a Class or FunctionScope

* Cleanup - Add missing case for NamedStore in expr_context_name. Remove unused var in set_namedexpr_content

* Refactor - Consolidate set_context and set_namedexpr_context to reduce duplicated code. Special cases for named expressions are handled by checking if ctx is NamedStore

* Cleanup - Add additional use cases for ast_for_namedexpr in usage comment. Fix multiple blank lines in test_named_expressions

* Tests - Remove unnecessary test case. Renumber test case function names

* Remove TargetScopeError for now. Will add back if needed

* Cleanup - Small comment nit for consistency

* Handle positional argument check with named expression

* Add TargetScopeError exception definition. Add documentation for TargetScopeError in c-api docs. Throw TargetScopeError instead of SyntaxError when using a named expression in a comprehension within a class scope

* Increase stack size for parser by 200. This is a minimal change (approx. 5kb) and should not have an impact on any systems. Update parser test to allow 99 nested levels again

* Add TargetScopeError to exception_hierarchy.txt for test_baseexception.py_

* Tests - Major update for named expression tests, both in test_named_expressions and test_parser

- Add test for TargetScopeError
- Add tests for named expressions in comprehension scope and edge cases
- Add tests for named expressions in function arguments (declarations
and call sites)
- Reorganize tests to group them more logically

* Cleanup - Remove unnecessary comment

* Cleanup - Comment nitpicks

* Explicitly disallow assignment expressions to a name inside parentheses, e.g.: ((x) := 0)

- Add check for LHS types to detect a parenthesis then a name (see note)
- Add test for this scenario
- Update tests for changed error message for named assignment to a tuple
(also, see note)

Note: This caused issues with the previous error handling for named assignment
to a LHS that contained an expression, such as a tuple. Thus, the check
for the LHS of a named expression must be changed to be more specific if
we wish to maintain the previous error messages

* Cleanup - Wrap lines more strictly in test file

* Revert "Explicitly disallow assignment expressions to a name inside parentheses, e.g.: ((x) := 0)"

This reverts commit f1531400ca7d7a2d148830c8ac703f041740896d.

* Add NEWS.d entry

* Tests - Fix error in test_pickle.test_exceptions by adding TargetScopeError to list of exceptions

* Tests - Update error message tests to reflect improved messaging convention (s/can't/cannot)

* Remove cases that cannot be reached in compile.c. Small linting update.

* Update Grammar/Tokens to add COLONEQUAL. Regenerate all files

* Update TargetScopeError PRE_INIT and POST_INIT, as this was purposefully left out when fixing rebase conflicts

* Add NamedStore back and regenerate files

* Pass along line number and end col info for named expression

* Simplify News entry

* Fix compiler warning and explicity mark fallthrough
2019-01-24 16:49:56 -07:00
Ivan Levkivskyi 9932a22897
bpo-33416: Add end positions to Python AST (GH-11605)
The majority of this PR is tediously passing `end_lineno` and `end_col_offset` everywhere. Here are non-trivial points:
* It is not possible to reconstruct end positions in AST "on the fly", some information is lost after an AST node is constructed, so we need two more attributes for every AST node `end_lineno` and `end_col_offset`.
* I add end position information to both CST and AST.  Although it may be technically possible to avoid adding end positions to CST, the code becomes more cumbersome and less efficient.
* Since the end position is not known for non-leaf CST nodes while the next token is added, this requires a bit of extra care (see `_PyNode_FinalizeEndPos`). Unless I made some mistake, the algorithm should be linear.
* For statements, I "trim" the end position of suites to not include the terminal newlines and dedent (this seems to be what people would expect), for example in
  ```python
  class C:
      pass

  pass
  ```
  the end line and end column for the class definition is (2, 8).
* For `end_col_offset` I use the common Python convention for indexing, for example for `pass` the `end_col_offset` is 4 (not 3), so that `[0:4]` gives one the source code that corresponds to the node.
* I added a helper function `ast.get_source_segment()`, to get source text segment corresponding to a given AST node. It is also useful for testing.

An (inevitable) downside of this PR is that AST now takes almost 25% more memory. I think however it is probably justified by the benefits.
2019-01-22 11:18:22 +00:00