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Issue #27999: Make "global after use" a SyntaxError, and ditto for nonlocal. 

Patch by Ivan Levkivskyi.
This commit is contained in:
Guido van Rossum 2016-09-09 09:36:26 -07:00
parent 95e502e7a6
commit 6cff8744a0
4 changed files with 59 additions and 71 deletions
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5
Doc/reference/simple_stmts.rst
View File

@ -903,11 +903,12 @@ block textually preceding that :keyword:`global` statement.
Names listed in a :keyword:`global` statement must not be defined as formal
parameters or in a :keyword:`for` loop control target, :keyword:`class`
definition, function definition, or :keyword:`import` statement.
definition, function definition, :keyword:`import` statement, or variable
annotation.
.. impl-detail::
The current implementation does not enforce the two restrictions, but
The current implementation does not enforce some of these restriction, but
programs should not abuse this freedom, as future implementations may enforce
them or silently change the meaning of the program.

18
Lib/test/test_syntax.py
View File

@ -366,7 +366,23 @@ build. The number of blocks must be greater than CO_MAXBLOCKS. SF #1565514
...
SyntaxError: too many statically nested blocks
Misuse of the nonlocal statement can lead to a few unique syntax errors.
Misuse of the nonlocal and global statement can lead to a few unique syntax errors.
>>> def f():
... x = 1
... global x
Traceback (most recent call last):
...
SyntaxError: name 'x' is assigned to before global declaration
>>> def f():
... x = 1
... def g():
... print(x)
... nonlocal x
Traceback (most recent call last):
...
SyntaxError: name 'x' is used prior to nonlocal declaration
>>> def f(x):
... nonlocal x

3
Misc/NEWS
View File

@ -10,6 +10,9 @@ What's New in Python 3.6.0 beta 1
Core and Builtins
-----------------
- Issue #27999: Make "global after use" a SyntaxError, and ditto for nonlocal.
Patch by Ivan Levkivskyi.
- Issue #28003: Implement PEP 525 -- Asynchronous Generators.
- Issue #27985: Implement PEP 526 -- Syntax for Variable Annotations.

104
Python/symtable.c
View File

@ -6,16 +6,22 @@
/* error strings used for warnings */
#define GLOBAL_AFTER_ASSIGN \
"name '%.400s' is assigned to before global declaration"
"name '%U' is assigned to before global declaration"
#define NONLOCAL_AFTER_ASSIGN \
"name '%.400s' is assigned to before nonlocal declaration"
"name '%U' is assigned to before nonlocal declaration"
#define GLOBAL_AFTER_USE \
"name '%.400s' is used prior to global declaration"
"name '%U' is used prior to global declaration"
#define NONLOCAL_AFTER_USE \
"name '%.400s' is used prior to nonlocal declaration"
"name '%U' is used prior to nonlocal declaration"
#define GLOBAL_ANNOT \
"annotated name '%U' can't be global"
#define NONLOCAL_ANNOT \
"annotated name '%U' can't be nonlocal"
#define IMPORT_STAR_WARNING "import * only allowed at module level"
@ -161,7 +167,6 @@ PyTypeObject PySTEntry_Type = {
};
static int symtable_analyze(struct symtable *st);
static int symtable_warn(struct symtable *st, const char *msg, int lineno);
static int symtable_enter_block(struct symtable *st, identifier name,
_Py_block_ty block, void *ast, int lineno,
int col_offset);
@ -907,27 +912,6 @@ symtable_analyze(struct symtable *st)
return r;
}
static int
symtable_warn(struct symtable *st, const char *msg, int lineno)
{
PyObject *message = PyUnicode_FromString(msg);
if (message == NULL)
return 0;
if (PyErr_WarnExplicitObject(PyExc_SyntaxWarning, message, st->st_filename,
lineno, NULL, NULL) < 0) {
Py_DECREF(message);
if (PyErr_ExceptionMatches(PyExc_SyntaxWarning)) {
PyErr_SetString(PyExc_SyntaxError, msg);
PyErr_SyntaxLocationObject(st->st_filename, st->st_cur->ste_lineno,
st->st_cur->ste_col_offset);
}
return 0;
}
Py_DECREF(message);
return 1;
}
/* symtable_enter_block() gets a reference via ste_new.
This reference is released when the block is exited, via the DECREF
in symtable_exit_block().
@ -1212,9 +1196,8 @@ symtable_visit_stmt(struct symtable *st, stmt_ty s)
if ((cur & (DEF_GLOBAL | DEF_NONLOCAL))
&& s->v.AnnAssign.simple) {
PyErr_Format(PyExc_SyntaxError,
"annotated name '%U' can't be %s",
e_name->v.Name.id,
cur & DEF_GLOBAL ? "global" : "nonlocal");
cur & DEF_GLOBAL ? GLOBAL_ANNOT : NONLOCAL_ANNOT,
e_name->v.Name.id);
PyErr_SyntaxLocationObject(st->st_filename,
s->lineno,
s->col_offset);
@ -1297,31 +1280,24 @@ symtable_visit_stmt(struct symtable *st, stmt_ty s)
long cur = symtable_lookup(st, name);
if (cur < 0)
VISIT_QUIT(st, 0);
if (cur & DEF_ANNOT) {
if (cur & (DEF_LOCAL | USE | DEF_ANNOT)) {
char* msg;
if (cur & DEF_ANNOT) {
msg = GLOBAL_ANNOT;
}
if (cur & DEF_LOCAL) {
msg = GLOBAL_AFTER_ASSIGN;
}
else {
msg = GLOBAL_AFTER_USE;
}
PyErr_Format(PyExc_SyntaxError,
"annotated name '%U' can't be global",
name);
msg, name);
PyErr_SyntaxLocationObject(st->st_filename,
s->lineno,
s->col_offset);
VISIT_QUIT(st, 0);
}
if (cur & (DEF_LOCAL | USE)) {
char buf[256];
char *c_name = _PyUnicode_AsString(name);
if (!c_name)
return 0;
if (cur & DEF_LOCAL)
PyOS_snprintf(buf, sizeof(buf),
GLOBAL_AFTER_ASSIGN,
c_name);
else
PyOS_snprintf(buf, sizeof(buf),
GLOBAL_AFTER_USE,
c_name);
if (!symtable_warn(st, buf, s->lineno))
VISIT_QUIT(st, 0);
}
if (!symtable_add_def(st, name, DEF_GLOBAL))
VISIT_QUIT(st, 0);
if (!symtable_record_directive(st, name, s))
@ -1337,31 +1313,23 @@ symtable_visit_stmt(struct symtable *st, stmt_ty s)
long cur = symtable_lookup(st, name);
if (cur < 0)
VISIT_QUIT(st, 0);
if (cur & DEF_ANNOT) {
PyErr_Format(PyExc_SyntaxError,
"annotated name '%U' can't be nonlocal",
name);
if (cur & (DEF_LOCAL | USE | DEF_ANNOT)) {
char* msg;
if (cur & DEF_ANNOT) {
msg = NONLOCAL_ANNOT;
}
if (cur & DEF_LOCAL) {
msg = NONLOCAL_AFTER_ASSIGN;
}
else {
msg = NONLOCAL_AFTER_USE;
}
PyErr_Format(PyExc_SyntaxError, msg, name);
PyErr_SyntaxLocationObject(st->st_filename,
s->lineno,
s->col_offset);
VISIT_QUIT(st, 0);
}
if (cur & (DEF_LOCAL | USE)) {
char buf[256];
char *c_name = _PyUnicode_AsString(name);
if (!c_name)
return 0;
if (cur & DEF_LOCAL)
PyOS_snprintf(buf, sizeof(buf),
NONLOCAL_AFTER_ASSIGN,
c_name);
else
PyOS_snprintf(buf, sizeof(buf),
NONLOCAL_AFTER_USE,
c_name);
if (!symtable_warn(st, buf, s->lineno))
VISIT_QUIT(st, 0);
}
if (!symtable_add_def(st, name, DEF_NONLOCAL))
VISIT_QUIT(st, 0);
if (!symtable_record_directive(st, name, s))