Add test cases for python#14209

test-data/unit/check-possibly-undefined.test

@@ -1043,3 +1043,230 @@ def foo(x: Union[int, str]) -> None:
         assert_never(x)
     f  # OK
 [builtins fixtures/tuple.pyi]
+
+[case testForLoopIndexMayBeUndefined]
+# flags: --enable-error-code possibly-undefined
+class Iterable:
+    def __iter__(self): ...
+
+for i in Iterable():
+    pass
+
+i  # E: Name "i" may be undefined  # if iterable was empty
+
+[case testForLoopBodyMayNotBeExecuted]
+# flags: --enable-error-code possibly-undefined
+# Regression test for https://github.com/python/mypy/issues/14209
+class Iterable:
+    def __iter__(self): ...
+
+for _ in Iterable():
+    a = 1
+
+a  # E: Name "a" may be undefined  # if iterable was empty
+
+[case testWhileLoopBodyMayNotBeExecuted]
+# flags: --enable-error-code possibly-undefined
+# Regression test for https://github.com/python/mypy/issues/14209
+def condition() -> bool: ...
+
+while condition():
+    a = 1
+
+a  # E: Name "a" may be undefined  # if `condition()` was `False` on first call
+
+[case testForLoopBodyOrElseIsExecuted]
+# flags: --enable-error-code possibly-undefined
+# Regression test for https://github.com/python/mypy/issues/14209
+class Iterable:
+    def __iter__(self): ...
+
+for _ in Iterable():
+    a = 1
+else:
+    a = 1  # if iterable is empty
+
+a  # OK
+
+[case testWhileLoopBodyOrElseIsExecuted]
+# flags: --enable-error-code possibly-undefined
+# Regression test for https://github.com/python/mypy/issues/14209
+def condition() -> bool: ...
+
+while condition():
+    a = 1
+else:
+    a = 1  # if `condition()` was `False` on first call
+
+a  # OK
+
+[case testForLoopBreakAsLastStatement]
+# flags: --enable-error-code possibly-undefined
+# Regression test for https://github.com/python/mypy/issues/14209
+class Iterable:
+    def __iter__(self): ...
+
+for i in Iterable():
+    a = 1
+    break
+else:
+    a = 1  # if iterable is empty
+
+a  # OK
+
+[case testForLoopBreakAsOnlyStatementOfCondition]
+# flags: --enable-error-code possibly-undefined
+# Regression test for https://github.com/python/mypy/issues/14209
+def condition() -> bool: ...
+class Iterable:
+    def __iter__(self): ...
+
+for i in Iterable():
+    a = 1
+    if condition():
+        break
+else:
+    a = 1  # if iterable is empty
+
+a  # OK
+
+[case testForLoopBreakAfterConditionalDefinition]
+# flags: --enable-error-code possibly-undefined
+# Regression test for https://github.com/python/mypy/issues/14209
+def condition() -> bool: ...
+class Iterable:
+    def __iter__(self): ...
+
+for i in Iterable():
+    if condition():
+        a = 1
+        break
+else:
+    a = 1  # if iterable is empty
+
+a  # OK
+[case testWhileLoopBreakAsLastStatement]
+# flags: --enable-error-code possibly-undefined
+# Regression test for https://github.com/python/mypy/issues/14209
+def condition() -> bool: ...
+
+while condition():
+    a = 1
+    break
+else:
+    a = 1  # if `condition()` was `False` on first call
+
+a  # OK
+
+[case testWhileLoopBreakAsOnlyStatementOfCondition]
+# flags: --enable-error-code possibly-undefined
+# Regression test for https://github.com/python/mypy/issues/14209
+def condition() -> bool: ...
+
+while condition():
+    a = 1
+    if condition():
+        break
+else:
+    a = 1  # if `condition()` was `False` on first call
+
+a  # OK
+
+[case testWhileLoopBreakAfterConditionalDefinition]
+# flags: --enable-error-code possibly-undefined
+# Regression test for https://github.com/python/mypy/issues/14209
+def condition() -> bool: ...
+
+while condition():
+    if condition():
+        a = 1
+        break
+else:
+    a = 1  # if `condition()` was `False` on first call, and if not `break`
+
+a  # OK
+
+[case testForLoopElseRaiseAsOnlyStatement]
+# flags: --enable-error-code possibly-undefined
+# Regression test for https://github.com/python/mypy/issues/14209
+class Iterable:
+    def __iter__(self): ...
+
+for _ in Iterable():
+    a = 1
+else:
+    raise Exception()  # if iterable is empty
+
+a  # OK
+[builtins fixtures/exception.pyi]
+
+[case testForLoopElseNoReturnAsOnlyStatement]
+# flags: --enable-error-code possibly-undefined
+# Regression test for https://github.com/python/mypy/issues/14209
+from typing import NoReturn
+def fail() -> NoReturn: ...
+class Iterable:
+    def __iter__(self): ...
+
+for _ in Iterable():
+    a = 1
+else:
+    fail()  # if iterable is empty
+
+a  # OK
+
+[case testForLoopElseReturnAsOnlyStatement]
+# flags: --enable-error-code possibly-undefined
+# Regression test for https://github.com/python/mypy/issues/14209
+class Iterable:
+    def __iter__(self): ...
+
+def f() -> int:
+    for _ in Iterable():
+        a = 1
+    else:
+        return 1  # if iterable is empty
+
+    return a  # OK
+
+[case testWhileLoopElseRaiseAsOnlyStatement]
+# flags: --enable-error-code possibly-undefined
+# Regression test for https://github.com/python/mypy/issues/14209
+def condition() -> bool: ...
+class Iterable:
+    def __iter__(self): ...
+
+while condition():
+    a = 1
+else:
+    raise Exception()  # if `condition()` was `False` on first call
+
+a  # OK
+[builtins fixtures/exception.pyi]
+
+[case testWhileLoopElseNoReturnAsOnlyStatement]
+# flags: --enable-error-code possibly-undefined
+# Regression test for https://github.com/python/mypy/issues/14209
+from typing import NoReturn
+def fail() -> NoReturn: ...
+def condition() -> bool: ...
+
+while condition():
+    a = 1
+else:
+    fail()  # if `condition()` was `False` on first call
+
+a  # OK
+
+[case testWhileLoopElseReturnAsOnlyStatement]
+# flags: --enable-error-code possibly-undefined
+# Regression test for https://github.com/python/mypy/issues/14209
+def condition() -> bool: ...
+
+def f() -> int:
+    while condition():
+        a = 1
+    else:
+        return 1  # if `condition()` was `False` on first call
+
+    return a  # OK