[Python-checkins] bpo-42374: Allow unparenthesized walrus in genexps (GH-23319)

Mon Nov 16 18:08:39 EST 2020

https://github.com/python/cpython/commit/cb3e5ed0716114393696ec7201e51fe0595eab4f
commit: cb3e5ed0716114393696ec7201e51fe0595eab4f
branch: master
author: Lysandros Nikolaou <lisandrosnik at gmail.com>
committer: miss-islington <31488909+miss-islington at users.noreply.github.com>
date: 2020年11月16日T15:08:35-08:00
summary:
bpo-42374: Allow unparenthesized walrus in genexps (GH-23319)
This fixes a regression that was introduced by the new parser.
Automerge-Triggered-By: GH:lysnikolaou
files:
A Misc/NEWS.d/next/Core and Builtins/2020-11-16-17-57-09.bpo-42374.t7np1E.rst
M Grammar/python.gram
M Lib/test/test_named_expressions.py
M Parser/parser.c

diff --git a/Grammar/python.gram b/Grammar/python.gram
index ae5e4b5d4ca64..91ce520be1ce7 100644
--- a/Grammar/python.gram
+++ b/Grammar/python.gram
@@ -517,7 +517,7 @@ group[expr_ty]:
 | '(' a=(yield_expr | named_expression) ')' { a }
 | invalid_group
 genexp[expr_ty]:
- | '(' a=expression ~ b=for_if_clauses ')' { _Py_GeneratorExp(a, b, EXTRA) }
+ | '(' a=named_expression ~ b=for_if_clauses ')' { _Py_GeneratorExp(a, b, EXTRA) }
 | invalid_comprehension
 set[expr_ty]: '{' a=expressions_list '}' { _Py_Set(a, EXTRA) }
 setcomp[expr_ty]:
diff --git a/Lib/test/test_named_expressions.py b/Lib/test/test_named_expressions.py
index c813830ce6d3c..d614f3267fad3 100644
--- a/Lib/test/test_named_expressions.py
+++ b/Lib/test/test_named_expressions.py
@@ -513,6 +513,15 @@ def g():
 self.assertEqual(nonlocal_var, None)
 f()
 
+ def test_named_expression_scope_in_genexp(self):
+ a = 1
+ b = [1, 2, 3, 4]
+ genexp = (c := i + a for i in b)
+
+ self.assertNotIn("c", locals())
+ for idx, elem in enumerate(genexp):
+ self.assertEqual(elem, b[idx] + a)
+
 
 if __name__ == "__main__":
 unittest.main()
diff --git a/Misc/NEWS.d/next/Core and Builtins/2020-11-16-17-57-09.bpo-42374.t7np1E.rst b/Misc/NEWS.d/next/Core and Builtins/2020-11-16-17-57-09.bpo-42374.t7np1E.rst
new file mode 100644
index 0000000000000..d86d038c8425c
--- /dev/null
+++ b/Misc/NEWS.d/next/Core and Builtins/2020-11-16-17-57-09.bpo-42374.t7np1E.rst	
@@ -0,0 +1,2 @@
+Fix a regression introduced by the new parser, where an unparenthesized walrus operator
+was not allowed within generator expressions.
\ No newline at end of file
diff --git a/Parser/parser.c b/Parser/parser.c
index 48ebfe65aedaf..94e265881984c 100644
--- a/Parser/parser.c
+++ b/Parser/parser.c
@@ -11357,7 +11357,7 @@ group_rule(Parser *p)
 return _res;
 }
 
-// genexp: '(' expression ~ for_if_clauses ')' | invalid_comprehension
+// genexp: '(' named_expression ~ for_if_clauses ')' | invalid_comprehension
 static expr_ty
 genexp_rule(Parser *p)
 {
@@ -11377,12 +11377,12 @@ genexp_rule(Parser *p)
 UNUSED(_start_lineno); // Only used by EXTRA macro
 int _start_col_offset = p->tokens[_mark]->col_offset;
 UNUSED(_start_col_offset); // Only used by EXTRA macro
- { // '(' expression ~ for_if_clauses ')'
+ { // '(' named_expression ~ for_if_clauses ')'
 if (p->error_indicator) {
 D(p->level--);
 return NULL;
 }
- D(fprintf(stderr, "%*c> genexp[%d-%d]: %s\n", p->level, ' ', _mark, p->mark, "'(' expression ~ for_if_clauses ')'"));
+ D(fprintf(stderr, "%*c> genexp[%d-%d]: %s\n", p->level, ' ', _mark, p->mark, "'(' named_expression ~ for_if_clauses ')'"));
 int _cut_var = 0;
 Token * _literal;
 Token * _literal_1;
@@ -11391,7 +11391,7 @@ genexp_rule(Parser *p)
 if (
 (_literal = _PyPegen_expect_token(p, 7)) // token='('
 &&
- (a = expression_rule(p)) // expression
+ (a = named_expression_rule(p)) // named_expression
 &&
 (_cut_var = 1)
 &&
@@ -11400,7 +11400,7 @@ genexp_rule(Parser *p)
 (_literal_1 = _PyPegen_expect_token(p, 8)) // token=')'
 )
 {
- D(fprintf(stderr, "%*c+ genexp[%d-%d]: %s succeeded!\n", p->level, ' ', _mark, p->mark, "'(' expression ~ for_if_clauses ')'"));
+ D(fprintf(stderr, "%*c+ genexp[%d-%d]: %s succeeded!\n", p->level, ' ', _mark, p->mark, "'(' named_expression ~ for_if_clauses ')'"));
 Token *_token = _PyPegen_get_last_nonnwhitespace_token(p);
 if (_token == NULL) {
 D(p->level--);
@@ -11420,7 +11420,7 @@ genexp_rule(Parser *p)
 }
 p->mark = _mark;
 D(fprintf(stderr, "%*c%s genexp[%d-%d]: %s failed!\n", p->level, ' ',
- p->error_indicator ? "ERROR!" : "-", _mark, p->mark, "'(' expression ~ for_if_clauses ')'"));
+ p->error_indicator ? "ERROR!" : "-", _mark, p->mark, "'(' named_expression ~ for_if_clauses ')'"));
 if (_cut_var) {
 D(p->level--);
 return NULL;
