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Checks module bodies to be reachable #11361

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Merged
merged 6 commits into from
Oct 31, 2021
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Checks module bodies to be reachable #11361

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8f8e9b6
Very naive attempt to fix #11331
sobolevn Oct 19, 2021
582e6f9
Very naive attempt to fix #11331
sobolevn Oct 19, 2021
c165a58
Very naive attempt to fix #11331
sobolevn Oct 19, 2021
8333ae6
Fixes existing test
sobolevn Oct 19, 2021
ba9c53a
Fixes existing test
sobolevn Oct 19, 2021
2d51fb8
Addresses review
sobolevn Oct 22, 2021
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5 changes: 5 additions & 0 deletions mypy/checker.py
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Original file line number Diff line number Diff line change
Expand Up @@ -307,6 +307,11 @@ def check_first_pass(self) -> None:
with self.tscope.module_scope(self.tree.fullname):
with self.enter_partial_types(), self.binder.top_frame_context():
for d in self.tree.defs:
if (self.binder.is_unreachable()
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self.accept(Block(self.tree.defs)) didn't work. Let's try explicit condition.

and self.should_report_unreachable_issues()
and not self.is_raising_or_empty(d)):
self.msg.unreachable_statement(d)
break
self.accept(d)

assert not self.current_node_deferred
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30 changes: 28 additions & 2 deletions test-data/unit/check-unreachable-code.test
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Expand Up @@ -754,35 +754,46 @@ if sys.version_info[0] >= 2:
reveal_type('') # N: Revealed type is "Literal['']?"
[builtins fixtures/ops.pyi]

[case testUnreachableFlagWithBadControlFlow]
[case testUnreachableFlagWithBadControlFlow1]
# flags: --warn-unreachable
a: int
if isinstance(a, int):
reveal_type(a) # N: Revealed type is "builtins.int"
else:
reveal_type(a) # E: Statement is unreachable
[builtins fixtures/isinstancelist.pyi]

[case testUnreachableFlagWithBadControlFlow2]
# flags: --warn-unreachable
b: int
while isinstance(b, int):
reveal_type(b) # N: Revealed type is "builtins.int"
else:
reveal_type(b) # E: Statement is unreachable
[builtins fixtures/isinstancelist.pyi]

[case testUnreachableFlagWithBadControlFlow3]
# flags: --warn-unreachable
def foo(c: int) -> None:
reveal_type(c) # N: Revealed type is "builtins.int"
assert not isinstance(c, int)
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Could be a clearer statement of intent to explicitly raise an exception here. This will not make the code below unreachable if run with assertions disabled, which you can do in Python.

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Nope, because we already have tests for explicit raise. Here we test assert False

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Ah, I see. I guess my point is that assert False isn't a safe way to block off code. But whether mypy recognizes that or not is a more high level design decision, and not a subject for this PR.

reveal_type(c) # E: Statement is unreachable
[builtins fixtures/isinstancelist.pyi]

[case testUnreachableFlagWithBadControlFlow4]
# flags: --warn-unreachable
d: int
if False:
reveal_type(d) # E: Statement is unreachable
[builtins fixtures/isinstancelist.pyi]

[case testUnreachableFlagWithBadControlFlow5]
# flags: --warn-unreachable
e: int
if True:
reveal_type(e) # N: Revealed type is "builtins.int"
else:
reveal_type(e) # E: Statement is unreachable

[builtins fixtures/isinstancelist.pyi]

[case testUnreachableFlagStatementAfterReturn]
Expand Down Expand Up @@ -1390,3 +1401,18 @@ def f() -> None:
if nope():
x = 1 # E: Statement is unreachable
[builtins fixtures/dict.pyi]

[case testUnreachableModuleBody1]
# flags: --warn-unreachable
from typing import NoReturn
def foo() -> NoReturn:
raise Exception("foo")
foo()
x = 1 # E: Statement is unreachable
[builtins fixtures/exception.pyi]

[case testUnreachableModuleBody2]
# flags: --warn-unreachable
raise Exception
x = 1 # E: Statement is unreachable
[builtins fixtures/exception.pyi]