The invalid assignment rules are very delicate since the parser can
easily raise an invalid assignment when a keyword argument is provided.
As they are very deep into the grammar tree, is very difficult to
specify in which contexts these rules can be used and in which don't.
For that, we need to use a different version of the rule that doesn't do
error checking in those situations where we don't want the rule to raise
(keyword arguments and generator expressions).
We also need to check if we are in left-recursive rule, as those can try
to eagerly advance the parser even if the parse will fail at the end of
the expression. Failing to do this allows the parser to start parsing a
call as a tuple and incorrectly identify a keyword argument as an
invalid assignment, before it realizes that it was not a tuple after all.
To improve the user experience understanding what part of the error messages associated with SyntaxErrors is wrong, we can highlight the whole error range and not only place the caret at the first character. In this way:
>>> foo(x, z for z in range(10), t, w)
File "<stdin>", line 1
foo(x, z for z in range(10), t, w)
^
SyntaxError: Generator expression must be parenthesized
becomes
>>> foo(x, z for z in range(10), t, w)
File "<stdin>", line 1
foo(x, z for z in range(10), t, w)
^^^^^^^^^^^^^^^^^^^^
SyntaxError: Generator expression must be parenthesized
* Add source location attributes to alias.
* Move alias star construction to pegen helper.
Co-authored-by: blurb-it[bot] <43283697+blurb-it[bot]@users.noreply.github.com>
Co-authored-by: Pablo Galindo <Pablogsal@gmail.com>
Rename AST functions of pycore_ast.h to use the "_PyAST_" prefix.
Remove macros creating aliases without prefix. For example, Module()
becomes _PyAST_Module(). Update Grammar/python.gram to use
_PyAST_xxx() functions.
* Add to the peg generator a new directive ('&&') that allows to expect
a token and hard fail the parsing if the token is not found. This
allows to quickly emmit syntax errors for missing tokens.
* Use the new grammar element to hard-fail if the ':' is missing before
suites.
This is only there so that alternative implementations written in statically-typed languages can use this grammar without
having type errors in the way.
Automerge-Triggered-By: GH:lysnikolaou
Currently walruses are not allowerd in set literals and set comprehensions:
>>> {y := 4, 4**2, 3**3}
File "<stdin>", line 1
{y := 4, 4**2, 3**3}
^
SyntaxError: invalid syntax
but they should be allowed as well per PEP 572
* Implement running the parser a second time for the errors messages
The first parser run is only responsible for detecting whether
there is a `SyntaxError` or not. If there isn't the AST gets returned.
Otherwise, the parser is run a second time with all the `invalid_*`
rules enabled so that all the customized error messages get produced.
* 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.
This program can segfault the parser by stack overflow:
```
import ast
code = "f(" + ",".join(['a' for _ in range(100000)]) + ")"
print("Ready!")
ast.parse(code)
```
the reason is that the rule for arguments has a simple recursion when collecting args:
args[expr_ty]:
[...]
| a=named_expression b=[',' c=args { c }] {
[...] }
`GET_INVALID_TARGET` might unexpectedly return `NULL`, which if not
caught will cause a SEGFAULT. Therefore, this commit introduces a new
inline function `RAISE_SYNTAX_ERROR_INVALID_TARGET` that always
checks for `GET_INVALID_TARGET` returning NULL and can be used in
the grammar, replacing the long C ternary operation used till now.
The following error messages get produced:
- `cannot delete ...` for invalid `del` targets
- `... is an illegal 'for' target` for invalid targets in for
statements
- `... is an illegal 'with' target` for invalid targets in
with statements
Additionally, a few `cut`s were added in various places before the
invocation of the `invalid_*` rule, in order to speed things
up.
Co-authored-by: Pablo Galindo <Pablogsal@gmail.com>
It no longer serves a purpose (there's only one parser) and having "new" in any name will eventually look odd. Also, it impinges on a potential sub-namespace, `__new_...__`.
Pablo Galindo
Lysandros Nikolaou
Brandt Bucher
Nick Coghlan
Matthew Suozzo
Victor Stinner
Brandt Bucher
Batuhan Taskaya
Guido van Rossum