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-rw-r--r--Python/symtable.c121
1 files changed, 97 insertions, 24 deletions
diff --git a/Python/symtable.c b/Python/symtable.c
index 668cc21b2d..e48baa808d 100644
--- a/Python/symtable.c
+++ b/Python/symtable.c
@@ -32,7 +32,16 @@
#define IMPORT_STAR_WARNING "import * only allowed at module level"
#define NAMED_EXPR_COMP_IN_CLASS \
-"named expression within a comprehension cannot be used in a class body"
+"assignment expression within a comprehension cannot be used in a class body"
+
+#define NAMED_EXPR_COMP_CONFLICT \
+"assignment expression cannot rebind comprehension iteration variable '%U'"
+
+#define NAMED_EXPR_COMP_INNER_LOOP_CONFLICT \
+"comprehension inner loop cannot rebind assignment expression target '%U'"
+
+#define NAMED_EXPR_COMP_ITER_EXPR \
+"assignment expression cannot be used in a comprehension iterable expression"
static PySTEntryObject *
ste_new(struct symtable *st, identifier name, _Py_block_ty block,
@@ -81,6 +90,8 @@ ste_new(struct symtable *st, identifier name, _Py_block_ty block,
ste->ste_comprehension = 0;
ste->ste_returns_value = 0;
ste->ste_needs_class_closure = 0;
+ ste->ste_comp_iter_target = 0;
+ ste->ste_comp_iter_expr = 0;
ste->ste_symbols = PyDict_New();
ste->ste_varnames = PyList_New(0);
@@ -373,14 +384,21 @@ PySymtable_Lookup(struct symtable *st, void *key)
return (PySTEntryObject *)v;
}
-int
-PyST_GetScope(PySTEntryObject *ste, PyObject *name)
+static long
+_PyST_GetSymbol(PySTEntryObject *ste, PyObject *name)
{
PyObject *v = PyDict_GetItem(ste->ste_symbols, name);
if (!v)
return 0;
assert(PyLong_Check(v));
- return (PyLong_AS_LONG(v) >> SCOPE_OFFSET) & SCOPE_MASK;
+ return PyLong_AS_LONG(v);
+}
+
+int
+PyST_GetScope(PySTEntryObject *ste, PyObject *name)
+{
+ long symbol = _PyST_GetSymbol(ste, name);
+ return (symbol >> SCOPE_OFFSET) & SCOPE_MASK;
}
static int
@@ -955,6 +973,13 @@ symtable_enter_block(struct symtable *st, identifier name, _Py_block_ty block,
return 0;
}
prev = st->st_cur;
+ /* bpo-37757: For now, disallow *all* assignment expressions in the
+ * outermost iterator expression of a comprehension, even those inside
+ * a nested comprehension or a lambda expression.
+ */
+ if (prev) {
+ ste->ste_comp_iter_expr = prev->ste_comp_iter_expr;
+ }
/* The entry is owned by the stack. Borrow it for st_cur. */
Py_DECREF(ste);
st->st_cur = ste;
@@ -971,15 +996,10 @@ symtable_enter_block(struct symtable *st, identifier name, _Py_block_ty block,
static long
symtable_lookup(struct symtable *st, PyObject *name)
{
- PyObject *o;
PyObject *mangled = _Py_Mangle(st->st_private, name);
if (!mangled)
return 0;
- o = PyDict_GetItem(st->st_cur->ste_symbols, mangled);
- Py_DECREF(mangled);
- if (!o)
- return 0;
- return PyLong_AsLong(o);
+ return _PyST_GetSymbol(st->st_cur, mangled);
}
static int
@@ -1012,6 +1032,22 @@ symtable_add_def_helper(struct symtable *st, PyObject *name, int flag, struct _s
else {
val = flag;
}
+ if (ste->ste_comp_iter_target) {
+ /* This name is an iteration variable in a comprehension,
+ * so check for a binding conflict with any named expressions.
+ * Otherwise, mark it as an iteration variable so subsequent
+ * named expressions can check for conflicts.
+ */
+ if (val & (DEF_GLOBAL | DEF_NONLOCAL)) {
+ PyErr_Format(PyExc_SyntaxError,
+ NAMED_EXPR_COMP_INNER_LOOP_CONFLICT, name);
+ PyErr_SyntaxLocationObject(st->st_filename,
+ ste->ste_lineno,
+ ste->ste_col_offset + 1);
+ goto error;
+ }
+ val |= DEF_COMP_ITER;
+ }
o = PyLong_FromLong(val);
if (o == NULL)
goto error;
@@ -1392,7 +1428,9 @@ static int
symtable_extend_namedexpr_scope(struct symtable *st, expr_ty e)
{
assert(st->st_stack);
+ assert(e->kind == Name_kind);
+ PyObject *target_name = e->v.Name.id;
Py_ssize_t i, size;
struct _symtable_entry *ste;
size = PyList_GET_SIZE(st->st_stack);
@@ -1402,32 +1440,42 @@ symtable_extend_namedexpr_scope(struct symtable *st, expr_ty e)
for (i = size - 1; i >= 0; i--) {
ste = (struct _symtable_entry *) PyList_GET_ITEM(st->st_stack, i);
- /* If our current entry is a comprehension, skip it */
+ /* If we find a comprehension scope, check for a target
+ * binding conflict with iteration variables, otherwise skip it
+ */
if (ste->ste_comprehension) {
+ long target_in_scope = _PyST_GetSymbol(ste, target_name);
+ if (target_in_scope & DEF_COMP_ITER) {
+ PyErr_Format(PyExc_SyntaxError, NAMED_EXPR_COMP_CONFLICT, target_name);
+ PyErr_SyntaxLocationObject(st->st_filename,
+ e->lineno,
+ e->col_offset);
+ VISIT_QUIT(st, 0);
+ }
continue;
}
/* If we find a FunctionBlock entry, add as NONLOCAL/LOCAL */
if (ste->ste_type == FunctionBlock) {
- if (!symtable_add_def(st, e->v.Name.id, DEF_NONLOCAL))
+ if (!symtable_add_def(st, target_name, DEF_NONLOCAL))
VISIT_QUIT(st, 0);
- if (!symtable_record_directive(st, e->v.Name.id, e->lineno, e->col_offset))
+ if (!symtable_record_directive(st, target_name, e->lineno, e->col_offset))
VISIT_QUIT(st, 0);
- return symtable_add_def_helper(st, e->v.Name.id, DEF_LOCAL, ste);
+ return symtable_add_def_helper(st, target_name, DEF_LOCAL, ste);
}
/* If we find a ModuleBlock entry, add as GLOBAL */
if (ste->ste_type == ModuleBlock) {
- if (!symtable_add_def(st, e->v.Name.id, DEF_GLOBAL))
+ if (!symtable_add_def(st, target_name, DEF_GLOBAL))
VISIT_QUIT(st, 0);
- if (!symtable_record_directive(st, e->v.Name.id, e->lineno, e->col_offset))
+ if (!symtable_record_directive(st, target_name, e->lineno, e->col_offset))
VISIT_QUIT(st, 0);
- return symtable_add_def_helper(st, e->v.Name.id, DEF_GLOBAL, ste);
+ return symtable_add_def_helper(st, target_name, DEF_GLOBAL, ste);
}
/* Disallow usage in ClassBlock */
if (ste->ste_type == ClassBlock) {
- PyErr_Format(PyExc_TargetScopeError, NAMED_EXPR_COMP_IN_CLASS, e->v.Name.id);
+ PyErr_Format(PyExc_SyntaxError, NAMED_EXPR_COMP_IN_CLASS);
PyErr_SyntaxLocationObject(st->st_filename,
e->lineno,
e->col_offset);
@@ -1443,6 +1491,26 @@ symtable_extend_namedexpr_scope(struct symtable *st, expr_ty e)
}
static int
+symtable_handle_namedexpr(struct symtable *st, expr_ty e)
+{
+ if (st->st_cur->ste_comp_iter_expr > 0) {
+ /* Assignment isn't allowed in a comprehension iterable expression */
+ PyErr_Format(PyExc_SyntaxError, NAMED_EXPR_COMP_ITER_EXPR);
+ PyErr_SyntaxLocationObject(st->st_filename,
+ e->lineno,
+ e->col_offset);
+ VISIT_QUIT(st, 0);
+ }
+ if (st->st_cur->ste_comprehension) {
+ /* Inside a comprehension body, so find the right target scope */
+ if (!symtable_extend_namedexpr_scope(st, e->v.NamedExpr.target))
+ VISIT_QUIT(st, 0);
+ }
+ VISIT(st, expr, e->v.NamedExpr.value);
+ VISIT(st, expr, e->v.NamedExpr.target);
+}
+
+static int
symtable_visit_expr(struct symtable *st, expr_ty e)
{
if (++st->recursion_depth > st->recursion_limit) {
@@ -1452,12 +1520,7 @@ symtable_visit_expr(struct symtable *st, expr_ty e)
}
switch (e->kind) {
case NamedExpr_kind:
- if (st->st_cur->ste_comprehension) {
- if (!symtable_extend_namedexpr_scope(st, e->v.NamedExpr.target))
- VISIT_QUIT(st, 0);
- }
- VISIT(st, expr, e->v.NamedExpr.value);
- VISIT(st, expr, e->v.NamedExpr.target);
+ symtable_handle_namedexpr(st, e);
break;
case BoolOp_kind:
VISIT_SEQ(st, expr, e->v.BoolOp.values);
@@ -1739,8 +1802,12 @@ symtable_visit_alias(struct symtable *st, alias_ty a)
static int
symtable_visit_comprehension(struct symtable *st, comprehension_ty lc)
{
+ st->st_cur->ste_comp_iter_target = 1;
VISIT(st, expr, lc->target);
+ st->st_cur->ste_comp_iter_target = 0;
+ st->st_cur->ste_comp_iter_expr++;
VISIT(st, expr, lc->iter);
+ st->st_cur->ste_comp_iter_expr--;
VISIT_SEQ(st, expr, lc->ifs);
if (lc->is_async) {
st->st_cur->ste_coroutine = 1;
@@ -1788,7 +1855,9 @@ symtable_handle_comprehension(struct symtable *st, expr_ty e,
comprehension_ty outermost = ((comprehension_ty)
asdl_seq_GET(generators, 0));
/* Outermost iterator is evaluated in current scope */
+ st->st_cur->ste_comp_iter_expr++;
VISIT(st, expr, outermost->iter);
+ st->st_cur->ste_comp_iter_expr--;
/* Create comprehension scope for the rest */
if (!scope_name ||
!symtable_enter_block(st, scope_name, FunctionBlock, (void *)e,
@@ -1805,7 +1874,11 @@ symtable_handle_comprehension(struct symtable *st, expr_ty e,
symtable_exit_block(st, (void *)e);
return 0;
}
+ /* Visit iteration variable target, and mark them as such */
+ st->st_cur->ste_comp_iter_target = 1;
VISIT(st, expr, outermost->target);
+ st->st_cur->ste_comp_iter_target = 0;
+ /* Visit the rest of the comprehension body */
VISIT_SEQ(st, expr, outermost->ifs);
VISIT_SEQ_TAIL(st, comprehension, generators, 1);
if (value)
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