bpo-30858: Improve error location for expressions with assignments (GH-23753)
Co-authored-by: Lysandros Nikolaou <lisandrosnik@gmail.com>
diff --git a/Grammar/python.gram b/Grammar/python.gram
index 9f47094..4915cc4 100644
--- a/Grammar/python.gram
+++ b/Grammar/python.gram
@@ -646,7 +646,7 @@
RAISE_SYNTAX_ERROR_KNOWN_LOCATION(a, "Generator expression must be parenthesized") }
| a=args ',' args { _PyPegen_arguments_parsing_error(p, a) }
invalid_kwarg:
- | a=expression '=' {
+ | expression a='=' {
RAISE_SYNTAX_ERROR_KNOWN_LOCATION(
a, "expression cannot contain assignment, perhaps you meant \"==\"?") }
invalid_named_expression:
diff --git a/Lib/test/test_exceptions.py b/Lib/test/test_exceptions.py
index 1bdd3f2..e752ab7 100644
--- a/Lib/test/test_exceptions.py
+++ b/Lib/test/test_exceptions.py
@@ -252,7 +252,7 @@ def baz():
check('from __future__ import doesnt_exist', 1, 1)
check('from __future__ import braces', 1, 1)
check('x=1\nfrom __future__ import division', 2, 1)
- check('foo(1=2)', 1, 5)
+ check('foo(1=2)', 1, 6)
check('def f():\n x, y: int', 2, 3)
check('[*x for x in xs]', 1, 2)
check('foo(x for x in range(10), 100)', 1, 5)
diff --git a/Lib/test/test_syntax.py b/Lib/test/test_syntax.py
index 91ca1db..d825560 100644
--- a/Lib/test/test_syntax.py
+++ b/Lib/test/test_syntax.py
@@ -802,6 +802,13 @@ def _check_error(self, code, errtext,
else:
self.fail("compile() did not raise SyntaxError")
+ def test_expression_with_assignment(self):
+ self._check_error(
+ "print(end1 + end2 = ' ')",
+ 'expression cannot contain assignment, perhaps you meant "=="?',
+ offset=19
+ )
+
def test_curly_brace_after_primary_raises_immediately(self):
self._check_error("f{", "invalid syntax", mode="single")
diff --git a/Misc/NEWS.d/next/Core and Builtins/2020-12-13-15-23-09.bpo-30858.-f9G4z.rst b/Misc/NEWS.d/next/Core and Builtins/2020-12-13-15-23-09.bpo-30858.-f9G4z.rst
new file mode 100644
index 0000000..f2d06c3
--- /dev/null
+++ b/Misc/NEWS.d/next/Core and Builtins/2020-12-13-15-23-09.bpo-30858.-f9G4z.rst
@@ -0,0 +1,2 @@
+Improve error location in expressions that contain assignments. Patch by
+Pablo Galindo and Lysandros Nikolaou.
diff --git a/Parser/parser.c b/Parser/parser.c
index b6c0495..2559969 100644
--- a/Parser/parser.c
+++ b/Parser/parser.c
@@ -14562,12 +14562,12 @@ invalid_kwarg_rule(Parser *p)
return NULL;
}
D(fprintf(stderr, "%*c> invalid_kwarg[%d-%d]: %s\n", p->level, ' ', _mark, p->mark, "expression '='"));
- Token * _literal;
- expr_ty a;
+ Token * a;
+ expr_ty expression_var;
if (
- (a = expression_rule(p)) // expression
+ (expression_var = expression_rule(p)) // expression
&&
- (_literal = _PyPegen_expect_token(p, 22)) // token='='
+ (a = _PyPegen_expect_token(p, 22)) // token='='
)
{
D(fprintf(stderr, "%*c+ invalid_kwarg[%d-%d]: %s succeeded!\n", p->level, ' ', _mark, p->mark, "expression '='"));