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--- a/Lib/test/test_exceptions.py
+++ b/Lib/test/test_exceptions.py
@@ -337,7 +337,6 @@ def baz():
check('x=1\nfrom __future__ import division', 2, 1)
check('foo(1=2)', 1, 5)
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)
check('for 1 in []: pass', 1, 5)
check('(yield i) = 2', 1, 2)
@@ -2433,7 +2432,8 @@ def test_encodings(self):
)
err = run_script(source.encode('cp437'))
self.assertEqual(err[-3], ' "¢¢¢¢¢¢" + f(4, x for x in range(1))')
- self.assertEqual(err[-2], ' ^^^')
+ self.assertEqual(err[-2], ' ^^^^^^^^^^^^^^^^^^^')
+ self.assertEqual(err[-1], 'SyntaxError: Generator expression must be parenthesized')
# Check backwards tokenizer errors
source = '# -*- coding: ascii -*-\n\n(\n'
diff --git a/Lib/test/test_unpack_ex.py b/Lib/test/test_unpack_ex.py
--- a/Lib/test/test_unpack_ex.py
+++ b/Lib/test/test_unpack_ex.py
@@ -141,54 +141,214 @@
>>> {0:1, **{0:2}, 0:3, 0:4}
{0: 4}
-List comprehension element unpacking
+Comprehension element unpacking
>>> a, b, c = [0, 1, 2], 3, 4
>>> [*a, b, c]
[0, 1, 2, 3, 4]
>>> l = [a, (3, 4), {5}, {6: None}, (i for i in range(7, 10))]
>>> [*item for item in l]
+ [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]
+
+ >>> [*[0, 1] for i in range(5)]
+ [0, 1, 0, 1, 0, 1, 0, 1, 0, 1]
+
+ >>> [*'a' for i in range(5)]
+ ['a', 'a', 'a', 'a', 'a']
+
+ >>> [*[] for i in range(10)]
+ []
+
+ >>> [*(x*2) for x in [[1, 2, 3], [], 'cat']]
+ [1, 2, 3, 1, 2, 3, 'c', 'a', 't', 'c', 'a', 't']
+
+ >>> {**{} for a in [1]}
+ {}
+
+ >>> {**{7: i} for i in range(10)}
+ {7: 9}
+
+ >>> dicts = [{1: 2}, {3: 4}, {5: 6, 7: 8}, {}, {9: 10}, {1: 0}]
+ >>> {**d for d in dicts}
+ {1: 0, 3: 4, 5: 6, 7: 8, 9: 10}
+
+ >>> gen = (*(0, 1) for i in range(5))
+ >>> next(gen)
+ 0
+ >>> list(gen)
+ [1, 0, 1, 0, 1, 0, 1, 0, 1]
+
+Comprehension unpacking with conditionals and double loops
+
+ >>> [*[i, i+1] for i in range(5) if i % 2 == 0]
+ [0, 1, 2, 3, 4, 5]
+
+ >>> [*y for x in [[[0], [1, 2, 3], [], [4, 5]], [[6, 7]]] for y in x]
+ [0, 1, 2, 3, 4, 5, 6, 7]
+
+ >>> [*y for x in [[[0], [1, 2, 3], [], [4, 5]], [[6, 7]]] for y in x if y and y[0]>0]
+ [1, 2, 3, 4, 5, 6, 7]
+
+ >>> dicts = [{1: 2}, {3: 4}, {5: 6, 7: 8}, {}, {9: 10}, {1: 0}]
+ >>> {**d for d in dicts if len(d) != 2}
+ {1: 0, 3: 4, 9: 10}
+
+Scoping of assignment expressions in comprehensions
+
+ >>> [*((y := i**2), 2*y) for i in range(4)]
+ [0, 0, 1, 2, 4, 8, 9, 18]
+ >>> y
+ 9
+
+ >>> [*(y := [i, i+1, i+2]) for i in range(4)]
+ [0, 1, 2, 1, 2, 3, 2, 3, 4, 3, 4, 5]
+ >>> y
+ [3, 4, 5]
+
+ >>> g = (*(z := [i, i+1, i+2]) for i in range(4))
+ >>> z
Traceback (most recent call last):
...
- SyntaxError: iterable unpacking cannot be used in comprehension
+ NameError: name 'z' is not defined
+ >>> next(g)
+ 0
+ >>> z
+ [0, 1, 2]
+ >>> next(g)
+ 1
+ >>> z
+ [0, 1, 2]
+ >>> next(g)
+ 2
+ >>> z
+ [0, 1, 2]
+ >>> next(g)
+ 1
+ >>> z
+ [1, 2, 3]
+
+ >>> x = [1, 2, 3]
+ >>> y = [4, 5, 6]
+ >>> def f(*args):
+ ... print(args)
+
+ >>> f(*x if x else y)
+ (1, 2, 3)
+
+
+Malformed comperehension element unpacking
+
+ >>> [*x for x in [1, 2, 3]]
+ Traceback (most recent call last):
+ ...
+ [*x for x in [1, 2, 3]]
+ ^^
+ TypeError: Value after * must be an iterable, not int
+
+
+Error messages for specific failure modes of unpacking
- >>> [*[0, 1] for i in range(10)]
+ >>> [*x if x else y for x in z]
Traceback (most recent call last):
...
- SyntaxError: iterable unpacking cannot be used in comprehension
+ [*x if x else y for x in z]
+ ^^^^^^^^^^^^^^
+ SyntaxError: invalid starred expression. Did you forget to wrap the conditional expression in parentheses?
- >>> [*'a' for i in range(10)]
+ >>> [*x if x else y]
Traceback (most recent call last):
...
- SyntaxError: iterable unpacking cannot be used in comprehension
+ [*x if x else y]
+ ^^^^^^^^^^^^^^
+ SyntaxError: invalid starred expression. Did you forget to wrap the conditional expression in parentheses?
- >>> [*[] for i in range(10)]
+ >>> [x if x else *y for x in z]
Traceback (most recent call last):
...
- SyntaxError: iterable unpacking cannot be used in comprehension
+ [x if x else *y for x in z]
+ ^
+ SyntaxError: cannot unpack only part of a conditional expression
- >>> {**{} for a in [1]}
+ >>> [x if x else *y]
Traceback (most recent call last):
...
- SyntaxError: dict unpacking cannot be used in dict comprehension
+ [x if x else *y]
+ ^
+ SyntaxError: cannot unpack only part of a conditional expression
-# Pegen is better here.
-# Generator expression in function arguments
+ >>> {**x if x else y}
+ Traceback (most recent call last):
+ ...
+ {**x if x else y}
+ ^^^^^^^^^^^^^^^^
+ SyntaxError: invalid double starred expression. Did you forget to wrap the conditional expression in parentheses?
+ >>> {x if x else **y}
+ Traceback (most recent call last):
+ ...
+ {x if x else **y}
+ ^^
+ SyntaxError: cannot use dict unpacking on only part of a conditional expression
-# >>> list(*x for x in (range(5) for i in range(3)))
-# Traceback (most recent call last):
-# ...
-# list(*x for x in (range(5) for i in range(3)))
-# ^
-# SyntaxError: invalid syntax
+ >>> [**x for x in [{1: 2}]]
+ Traceback (most recent call last):
+ ...
+ [**x for x in [{1: 2}]]
+ ^^^
+ SyntaxError: cannot use dict unpacking in list comprehension
+
+ >>> (**x for x in [{1:2}])
+ Traceback (most recent call last):
+ ...
+ (**x for x in [{1:2}])
+ ^^^
+ SyntaxError: cannot use dict unpacking in generator expression
>>> dict(**x for x in [{1:2}])
Traceback (most recent call last):
...
dict(**x for x in [{1:2}])
- ^
- SyntaxError: invalid syntax
+ ^^^
+ SyntaxError: cannot use dict unpacking in generator expression
+
+ >>> {*a: b for a, b in {1: 2}.items()}
+ Traceback (most recent call last):
+ ...
+ {*a: b for a, b in {1: 2}.items()}
+ ^^
+ SyntaxError: cannot use a starred expression in a dictionary key
+
+ >>> {**a: b for a, b in {1: 2}.items()}
+ Traceback (most recent call last):
+ ...
+ {**a: b for a, b in {1: 2}.items()}
+ ^^^
+ SyntaxError: cannot use dict unpacking in a dictionary key
+
+ >>> {a: *b for a, b in {1: 2}.items()}
+ Traceback (most recent call last):
+ ...
+ {a: *b for a, b in {1: 2}.items()}
+ ^^
+ SyntaxError: cannot use a starred expression in a dictionary value
+
+ >>> {a: **b for a, b in {1: 2}.items()}
+ Traceback (most recent call last):
+ ...
+ {a: **b for a, b in {1: 2}.items()}
+ ^^^
+ SyntaxError: cannot use dict unpacking in a dictionary value
+
+
+# Generator expression in function arguments
+
+ >>> list(*x for x in (range(5) for i in range(3)))
+ [0, 1, 2, 3, 4, 0, 1, 2, 3, 4, 0, 1, 2, 3, 4]
+
+ >>> def f(arg):
+ ... print(type(arg), list(arg), list(arg))
+ >>> f(*x for x in [[1,2,3]])
+ <class 'generator'> [1, 2, 3] []
Iterable argument unpacking
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