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Merged
msullivan merged 7 commits into from
Oct 18, 2020
Merged

Allow assignment to an empty tuple #5617

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2993591
remove check and update tests
Sep 13, 2018
52e44cb
remove extra line
Sep 13, 2018
622ec8f
Merge branch 'master' into assign-empty-tuple
Jan 2, 2019
28aae4b
add the tests I would like to have
Jan 3, 2019
25fab94
remove failing tests
Jan 3, 2019
a223964
Merge branch 'master' into assign-empty-tuple
msullivan Oct 18, 2020
a3dd53b
cleanup, add test
msullivan Oct 18, 2020
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3 changes: 0 additions & 3 deletions mypy/semanal.py
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Original file line number Diff line number Diff line change
Expand Up @@ -2636,9 +2636,6 @@ def analyze_lvalue(self,
self.fail('Unexpected type declaration', lval)
lval.accept(self)
elif isinstance(lval, TupleExpr):
items = lval.items
if len(items) == 0 and isinstance(lval, TupleExpr):
self.fail("can't assign to ()", lval)
self.analyze_tuple_or_list_lvalue(lval, explicit_type)
elif isinstance(lval, StarExpr):
if nested:
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3 changes: 2 additions & 1 deletion test-data/unit/README.md
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Expand Up @@ -7,7 +7,8 @@ Quick Start

To add a simple unit test for a new feature you developed, open or create a
`test-data/unit/check-*.test` file with a name that roughly relates to the
feature you added.
feature you added. If you added a new `check-*.test` file, add it to the list
of files in `mypy/test/testcheck.py`.

Add the test in this format anywhere in the file:

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12 changes: 12 additions & 0 deletions test-data/unit/check-tuples.test
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Expand Up @@ -1458,3 +1458,15 @@ x7, x8, y7, y8 = *points2, *points3 # E: Contiguous iterable with same type expe

x9, y9, x10, y10, z5 = *points2, 1, *points2 # E: Contiguous iterable with same type expected
[builtins fixtures/tuple.pyi]

[case testAssignEmptyPy36]
# flags: --python-version 3.6
() = []

[case testAssignEmptyPy27]
# flags: --python-version 2.7
() = [] # E: can't assign to ()

[case testAssignEmptyBogus]
() = 1 # E: 'Literal[1]?' object is not iterable
[builtins fixtures/tuple.pyi]
5 changes: 0 additions & 5 deletions test-data/unit/semanal-errors.test
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Expand Up @@ -377,11 +377,6 @@ main:1: error: can't assign to literal
[out]
main:1: error: can't assign to literal

[case testInvalidLvalues5]
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@JelleZijlstra JelleZijlstra Sep 13, 2018

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Shouldn't this still be an error saying 1 is not iterable or similar?

Also, I would like to see a new test that does things like () = [] or a, () = list() and asserts that there are no errors.

() = 1
[out]
main:1: error: can't assign to ()

[case testInvalidLvalues6]
x = y = z = 1 # ok
x, (y, 1) = 1
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