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Preserve block unreachablility when checking function definitions with constrained TypeVars #18217

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Merged
merged 2 commits into from
Dec 2, 2024
Merged

Preserve block unreachablility when checking function definitions with constrained TypeVars #18217

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efa9481
Preserve value of Block.is_unreachable in TransformVisitor
brianschubert Nov 30, 2024
f2b8e12
Add `is_unreachable` to `Block.__init__`
brianschubert Dec 1, 2024
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4 changes: 3 additions & 1 deletion mypy/treetransform.py
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Original file line number Diff line number Diff line change
Expand Up @@ -276,7 +276,9 @@ def visit_nonlocal_decl(self, node: NonlocalDecl) -> NonlocalDecl:
return NonlocalDecl(node.names.copy())

def visit_block(self, node: Block) -> Block:
return Block(self.statements(node.body))
new = Block(self.statements(node.body))
new.is_unreachable = node.is_unreachable
return new

def visit_decorator(self, node: Decorator) -> Decorator:
# Note that a Decorator must be transformed to a Decorator.
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10 changes: 10 additions & 0 deletions test-data/unit/check-unreachable-code.test
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Expand Up @@ -1000,6 +1000,16 @@ class Test4(Generic[T3]):

[builtins fixtures/isinstancelist.pyi]

[case testUnreachableBlockStaysUnreachableWithTypeVarConstraints]
# flags: --always-false COMPILE_TIME_FALSE
from typing import TypeVar
COMPILE_TIME_FALSE = False
T = TypeVar("T", int, str)
def foo(x: T) -> T:
if COMPILE_TIME_FALSE:
return "bad"
return x

[case testUnreachableFlagContextManagersNoSuppress]
# flags: --warn-unreachable
from contextlib import contextmanager
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