check-unreachable-code.test

-- Type checker test cases for conditional checks that result in some
-- blocks classified as unreachable (they are not type checked or semantically
-- analyzed).
--
-- For example, we skip blocks that will not be executed on the active
-- Python version.

[case testConditionalTypeAliasPY3]
import typing
def f(): pass
PY3 = f()
if PY3:
    t = int
    x = object() + 'x' # E: Unsupported left operand type for + ("object")
else:
    t = str
    y = 'x' / 1
x
z = 1 # type: t

[case testConditionalAssignmentPY2]
import typing
def f(): pass
PY2 = f()
if PY2:
    x = object() + 'x'
else:
    y = 'x' / 1 # E: Unsupported left operand type for / ("str")
y

[case testConditionalImport]
import typing
def f(): pass
PY2 = f()
if PY2:
    import fuzzybar
    from barbar import *
    from pawwaw import a, bc
else:
    import m
[file m.py]
import typing
x = 1
if int():
    x = 'a'
[out]
tmp/m.py:4: error: Incompatible types in assignment (expression has type "str", variable has type "int")

[case testNegatedMypyConditional]
import typing
MYPY = 0
if not MYPY:
    import xyz753
else:
    import pow123 # E
[builtins fixtures/bool.pyi]
[out]
main:6: error: Cannot find implementation or library stub for module named "pow123"
main:6: note: See https://mypy.readthedocs.io/en/stable/running_mypy.html#missing-imports

[case testMypyConditional]
import typing
MYPY = 0
if MYPY:
    None + 1 # E: Unsupported left operand type for + ("None")
else:
    None + ''
[builtins fixtures/bool.pyi]

[case testTypeCheckingConditional]
import typing
if typing.TYPE_CHECKING:
    import pow123 # E
else:
    import xyz753
[typing fixtures/typing-medium.pyi]
[out]
main:3: error: Cannot find implementation or library stub for module named "pow123"
main:3: note: See https://mypy.readthedocs.io/en/stable/running_mypy.html#missing-imports

[case testTypeCheckingConditionalFromImport]
from typing import TYPE_CHECKING
if TYPE_CHECKING:
    import pow123 # E
else:
    import xyz753
[typing fixtures/typing-medium.pyi]
[out]
main:3: error: Cannot find implementation or library stub for module named "pow123"
main:3: note: See https://mypy.readthedocs.io/en/stable/running_mypy.html#missing-imports

[case testNegatedTypeCheckingConditional]
import typing
if not typing.TYPE_CHECKING:
    import pow123 # E
else:
    import xyz753
[builtins fixtures/bool.pyi]
[typing fixtures/typing-medium.pyi]
[out]
main:5: error: Cannot find implementation or library stub for module named "xyz753"
main:5: note: See https://mypy.readthedocs.io/en/stable/running_mypy.html#missing-imports

[case testUndefinedTypeCheckingConditional]
if not TYPE_CHECKING: # E
    import pow123
else:
    import xyz753
[builtins fixtures/bool.pyi]
[out]
main:1: error: Name "TYPE_CHECKING" is not defined
main:4: error: Cannot find implementation or library stub for module named "xyz753"
main:4: note: See https://mypy.readthedocs.io/en/stable/running_mypy.html#missing-imports

[case testConditionalClassDefPY3]
def f(): pass
PY3 = f()
if PY3:
    pass
else:
    class X(object):
        pass

[case testUnreachabilityAndElifPY3]
def f(): pass
PY3 = f()
if PY3:
    pass
elif bool():
    import nonexistent
    1 + ''
else:
    import bad_name
    1 + ''
[builtins fixtures/bool.pyi]
[out]

[case testSysVersionInfo]
import sys
if sys.version_info[0] >= 3:
    def foo() -> int: return 0
else:
    def foo() -> str: return ''
reveal_type(foo())  # N: Revealed type is "builtins.int"
[builtins fixtures/ops.pyi]
[out]

[case testSysVersionInfoReversedOperandsOrder]
import sys
if (3,) <= sys.version_info:
    def foo() -> int: return 0
else:
    def foo() -> str: return ''
reveal_type(foo())  # N: Revealed type is "builtins.int"
[builtins fixtures/ops.pyi]
[out]

[case testSysVersionInfoNegated]
import sys
if not (sys.version_info[0] < 3):
    def foo() -> int: return 0
else:
    def foo() -> str: return ''
reveal_type(foo())  # N: Revealed type is "builtins.int"
[builtins fixtures/ops.pyi]
[out]

[case testSysVersionInfoSliced1]
import sys
if sys.version_info[:1] >= (3,):
    def foo() -> int: return 0
else:
    def foo() -> str: return ''
foo() + 0
[builtins fixtures/ops.pyi]
[out]

[case testSysVersionInfoSliced2]
import sys
if sys.version_info[:2] >= (3, 0):
    def foo() -> int: return 0
else:
    def foo() -> str: return ''
foo() + 0
[builtins fixtures/ops.pyi]
[out]

[case testSysVersionInfoSliced3]
import sys
if sys.version_info[:] >= (3, 0):
    def foo() -> int: return 0
else:
    def foo() -> str: return ''
foo() + 0
[builtins fixtures/ops.pyi]
[out]

[case testSysVersionInfoSliced4]
import sys
if sys.version_info[0:2] >= (3, 0):
    def foo() -> int: return 0
else:
    def foo() -> str: return ''
foo() + 0
[builtins fixtures/ops.pyi]
[out]

[case testSysVersionInfoSliced5]
import sys
if sys.version_info[0:] >= (3,):
    def foo() -> int: return 0
else:
    def foo() -> str: return ''
foo() + 0
[builtins fixtures/ops.pyi]
[out]

[case testSysVersionInfoSliced6]
import sys
if sys.version_info[1:] >= (5,):
    def foo() -> int: return 0
else:
    def foo() -> str: return ''
foo() + 0
[builtins fixtures/ops.pyi]
[out]

[case testSysVersionInfoSliced7]
import sys
if sys.version_info >= (3, 5):
    def foo() -> int: return 0
else:
    def foo() -> str: return ''
foo() + 0
[builtins fixtures/ops.pyi]
[out]

[case testSysVersionInfoSliced8]
# Our pyversion only has (major, minor),
# so testing for (major, minor, bugfix) is unsupported.
import sys
if sys.version_info >= (3, 5, 0):
    def foo() -> int: return 0
else:
    def foo() -> str: return ''  # E: All conditional function variants must have identical signatures \
                                 # N: Original: \
                                 # N:     def foo() -> int \
                                 # N: Redefinition: \
                                 # N:     def foo() -> str
[builtins fixtures/ops.pyi]
[out]

[case testSysVersionInfoSliced9]
# Our pyversion only has (major, minor),
# so testing for (minor, bugfix) is unsupported (also it's silly :-).
import sys
if sys.version_info[1:] >= (5, 0):
    def foo() -> int: return 0
else:
    def foo() -> str: return ''  # E: All conditional function variants must have identical signatures \
                                 # N: Original: \
                                 # N:     def foo() -> int \
                                 # N: Redefinition: \
                                 # N:     def foo() -> str
[builtins fixtures/ops.pyi]
[out]

[case testSysPlatform1]
import sys
if sys.platform == 'fictional':
    def foo() -> int: return 0
else:
    def foo() -> str: return ''
foo() + ''
[builtins fixtures/ops.pyi]
[out]

[case testSysPlatform2]
import sys
if sys.platform != 'fictional':
    def foo() -> int: return 0
else:
    def foo() -> str: return ''
foo() + 0
[builtins fixtures/ops.pyi]
[out]

[case testSysPlatformNegated]
import sys
if not (sys.platform == 'fictional'):
    def foo() -> int: return 0
else:
    def foo() -> str: return ''
foo() + 0
[builtins fixtures/ops.pyi]
[out]

[case testSysVersionInfoClass]
import sys
if sys.version_info < (3, 5):
    class C:
        pass
else:
    class C:
        def foo(self) -> int: return 0
C().foo() + 0
[builtins fixtures/ops.pyi]
[out]

[case testSysVersionInfoImport]
import sys
if sys.version_info >= (3, 5):
    import collections
else:
    collections = None
Pt = collections.namedtuple('Pt', 'x y z')
[builtins fixtures/ops.pyi]
[out]

[case testSysVersionInfoVariable]
import sys
if sys.version_info >= (3, 5):
    x = ''
else:
    x = 0
x + ''
[builtins fixtures/ops.pyi]
[out]

[case testSysVersionInfoInClass]
import sys
class C:
    if sys.version_info >= (3, 5):
        def foo(self) -> int: return 0
    else:
        def foo(self) -> str: return ''
reveal_type(C().foo())  # N: Revealed type is "builtins.int"
[builtins fixtures/ops.pyi]
[out]

[case testSysVersionInfoInFunction]
import sys
def foo() -> None:
    if sys.version_info >= (3, 5):
        x = ''
    else:
        x = 0
    reveal_type(x)  # N: Revealed type is "builtins.str"
[builtins fixtures/ops.pyi]
[out]

[case testSysPlatformInMethod]
import sys
class C:
    def foo(self) -> None:
        if sys.platform != 'fictional':
            x = ''
        else:
            x = 0
        reveal_type(x)  # N: Revealed type is "builtins.str"
[builtins fixtures/ops.pyi]
[out]

[case testSysPlatformInFunctionImport1]
import sys
def foo() -> None:
    if sys.platform != 'fictional':
        import a
    else:
        import b as a
    a.x
[file a.py]
x = 1
[builtins fixtures/ops.pyi]
[out]

[case testSysPlatformInFunctionImport2]
import sys
def foo() -> None:
    if sys.platform == 'fictional':
        import b as a
    else:
        import a
    a.x
[file a.py]
x = 1
[builtins fixtures/ops.pyi]
[out]

[case testSysPlatformInFunctionImport3]
from typing import Callable
import sys

def idf(x: Callable[[], None]) -> Callable[[], None]: return x

@idf
def foo() -> None:
    if sys.platform == 'fictional':
        import b as a
    else:
        import a
    a.x
[file a.py]
x = 1
[builtins fixtures/ops.pyi]
[out]


[case testSysPlatformInMethodImport2]

import sys
class A:
    def foo(self) -> None:
        if sys.platform == 'fictional':
            import b as a
        else:
            import a
        a.x
[file a.py]
x = 1
[builtins fixtures/ops.pyi]
[out]

[case testCustomSysVersionInfo]
# flags: --python-version 3.11
import sys
if sys.version_info >= (3, 11):
    x = "foo"
else:
    x = 3
reveal_type(x)  # N: Revealed type is "builtins.str"
[builtins fixtures/ops.pyi]

[case testCustomSysVersionInfo2]
# flags: --python-version 3.11
import sys
if sys.version_info >= (3, 12):
    x = "foo"
else:
    x = 3
reveal_type(x)  # N: Revealed type is "builtins.int"
[builtins fixtures/ops.pyi]

[case testCustomSysPlatform]
# flags: --platform linux
import sys
if sys.platform == 'linux':
    x = "foo"
else:
    x = 3
reveal_type(x)  # N: Revealed type is "builtins.str"
[builtins fixtures/ops.pyi]
[out]

[case testCustomSysPlatform2]
# flags: --platform win32
import sys
if sys.platform == 'linux':
    x = "foo"
else:
    x = 3
reveal_type(x)  # N: Revealed type is "builtins.int"
[builtins fixtures/ops.pyi]
[out]

[case testCustomSysPlatformStartsWith]
# flags: --platform win32
import sys
if sys.platform.startswith('win'):
    x = "foo"
else:
    x = 3
reveal_type(x)  # N: Revealed type is "builtins.str"
[builtins fixtures/ops.pyi]
[out]

[case testShortCircuitInExpression]
import typing
def make() -> bool: pass
PY2 = PY3 = make()

a = PY2 and str()
b = PY3 and str()
c = PY2 or str()
d = PY3 or str()
e = (PY2 or PY3) and str()
f = (PY3 or PY2) and str()
g = (PY2 or PY3) or str()
h = (PY3 or PY2) or str()
reveal_type(a)  # N: Revealed type is "builtins.bool"
reveal_type(b)  # N: Revealed type is "builtins.str"
reveal_type(c)  # N: Revealed type is "builtins.str"
reveal_type(d)  # N: Revealed type is "builtins.bool"
reveal_type(e)  # N: Revealed type is "builtins.str"
reveal_type(f)  # N: Revealed type is "builtins.str"
reveal_type(g)  # N: Revealed type is "builtins.bool"
reveal_type(h)  # N: Revealed type is "builtins.bool"
[builtins fixtures/ops.pyi]
[out]

[case testConditionalValuesBinaryOps]
# flags: --platform linux
import sys

t_and_t = (sys.platform == 'linux' and sys.platform == 'linux') and str()
t_or_t = (sys.platform == 'linux' or sys.platform == 'linux') and str()
t_and_f = (sys.platform == 'linux' and sys.platform == 'windows') and str()
t_or_f = (sys.platform == 'linux' or sys.platform == 'windows') and str()
f_and_t = (sys.platform == 'windows' and sys.platform == 'linux') and str()
f_or_t = (sys.platform == 'windows' or sys.platform == 'linux') and str()
f_and_f = (sys.platform == 'windows' and sys.platform == 'windows') and str()
f_or_f = (sys.platform == 'windows' or sys.platform == 'windows') and str()
reveal_type(t_and_t) # N: Revealed type is "builtins.str"
reveal_type(t_or_t) # N: Revealed type is "builtins.str"
reveal_type(f_and_t) # N: Revealed type is "builtins.bool"
reveal_type(f_or_t) # N: Revealed type is "builtins.str"
reveal_type(t_and_f) # N: Revealed type is "builtins.bool"
reveal_type(t_or_f) # N: Revealed type is "builtins.str"
reveal_type(f_and_f) # N: Revealed type is "builtins.bool"
reveal_type(f_or_f) # N: Revealed type is "builtins.bool"
[builtins fixtures/ops.pyi]

[case testConditionalValuesNegation]
# flags: --platform linux
import sys

not_t = not sys.platform == 'linux' and str()
not_f = not sys.platform == 'windows' and str()
not_and_t = not (sys.platform == 'linux' and sys.platform == 'linux') and str()
not_and_f = not (sys.platform == 'linux' and sys.platform == 'windows') and str()
not_or_t = not (sys.platform == 'linux' or sys.platform == 'linux') and str()
not_or_f = not (sys.platform == 'windows' or sys.platform == 'windows') and str()
reveal_type(not_t) # N: Revealed type is "builtins.bool"
reveal_type(not_f) # N: Revealed type is "builtins.str"
reveal_type(not_and_t) # N: Revealed type is "builtins.bool"
reveal_type(not_and_f) # N: Revealed type is "builtins.str"
reveal_type(not_or_t) # N: Revealed type is "builtins.bool"
reveal_type(not_or_f) # N: Revealed type is "builtins.str"
[builtins fixtures/ops.pyi]

[case testConditionalValuesUnsupportedOps]
# flags: --platform linux
import sys

unary_minus = -(sys.platform == 'linux') and str()
binary_minus = ((sys.platform == 'linux') - (sys.platform == 'linux')) and str()
reveal_type(unary_minus) # N: Revealed type is "Literal[0] | builtins.str"
reveal_type(binary_minus) # N: Revealed type is "Literal[0] | builtins.str"
[builtins fixtures/ops.pyi]

[case testMypyFalseValuesInBinaryOps_no_empty]
# flags: --platform linux
import sys
from typing import TYPE_CHECKING

MYPY = 0

if TYPE_CHECKING and sys.platform == 'linux':
    def foo1() -> int: ...
if sys.platform == 'linux' and TYPE_CHECKING:
    def foo2() -> int: ...
if MYPY and sys.platform == 'linux':
    def foo3() -> int: ...
if sys.platform == 'linux' and MYPY:
    def foo4() -> int: ...

if TYPE_CHECKING or sys.platform == 'linux':
    def bar1() -> int: ...  # E: Missing return statement
if sys.platform == 'linux' or TYPE_CHECKING:
    def bar2() -> int: ...  # E: Missing return statement
if MYPY or sys.platform == 'linux':
    def bar3() -> int: ...  # E: Missing return statement
if sys.platform == 'linux' or MYPY:
    def bar4() -> int: ...  # E: Missing return statement
[builtins fixtures/ops.pyi]

[case testShortCircuitAndWithConditionalAssignment]
# flags: --platform linux
import sys

def f(): pass
PY2 = f()
if PY2 and sys.platform == 'linux':
    x = 'foo'
else:
    x = 3
reveal_type(x)  # N: Revealed type is "builtins.int"
if sys.platform == 'linux' and PY2:
    y = 'foo'
else:
    y = 3
reveal_type(y)  # N: Revealed type is "builtins.int"
[builtins fixtures/ops.pyi]

[case testShortCircuitOrWithConditionalAssignment]
# flags: --platform linux
import sys

def f(): pass
PY2 = f()
if PY2 or sys.platform == 'linux':
    x = 'foo'
else:
    x = 3
reveal_type(x)  # N: Revealed type is "builtins.str"
if sys.platform == 'linux' or PY2:
    y = 'foo'
else:
    y = 3
reveal_type(y)  # N: Revealed type is "builtins.str"
[builtins fixtures/ops.pyi]

[case testShortCircuitNoEvaluation]
# flags: --platform linux --always-false COMPILE_TIME_FALSE
import sys

if sys.platform == 'darwin':
    mac_only = 'junk'

# `mac_only` should not be evaluated
if sys.platform == 'darwin' and mac_only:
    pass
if sys.platform == 'linux' or mac_only:
    pass

COMPILE_TIME_FALSE = 'junk'

if COMPILE_TIME_FALSE:
    compile_time_false_only = 'junk'

# `compile_time_false_only` should not be evaluated
if COMPILE_TIME_FALSE and compile_time_false_only:
    pass
if not COMPILE_TIME_FALSE or compile_time_false_only:
    pass

MYPY = False

if not MYPY:
    mypy_only = 'junk'

# `mypy_only` should not be evaluated
if not MYPY and mypy_only:
    pass
if MYPY or mypy_only:
    pass
[builtins fixtures/ops.pyi]

[case testSemanticAnalysisFalseButTypeNarrowingTrue]
# flags: --always-false COMPILE_TIME_FALSE
from typing import Literal

indeterminate: str
COMPILE_TIME_FALSE: Literal[True]  # type-narrowing: mapped in 'if' only
a = COMPILE_TIME_FALSE or indeterminate
reveal_type(a)  # N: Revealed type is "builtins.str"
b = indeterminate or COMPILE_TIME_FALSE
reveal_type(b)  # N: Revealed type is "builtins.str | Literal[True]"
[typing fixtures/typing-medium.pyi]

[case testSemanticAnalysisTrueButTypeNarrowingFalse]
# flags: --always-true COMPILE_TIME_TRUE
from typing import Literal

indeterminate: str
COMPILE_TIME_TRUE: Literal[False]  # type narrowed to `else` only
a = COMPILE_TIME_TRUE or indeterminate
reveal_type(a)  # N: Revealed type is "Literal[False]"
b = indeterminate or COMPILE_TIME_TRUE
reveal_type(b)  # N: Revealed type is "builtins.str | Literal[False]"

[typing fixtures/typing-medium.pyi]
[case testConditionalAssertWithoutElse]
import typing

class A: pass
class B(A): pass

x = A()
reveal_type(x)  # N: Revealed type is "__main__.A"

if typing.TYPE_CHECKING:
    assert isinstance(x, B)
    reveal_type(x)  # N: Revealed type is "__main__.B"

reveal_type(x)  # N: Revealed type is "__main__.B"

[builtins fixtures/isinstancelist.pyi]
[typing fixtures/typing-medium.pyi]

[case testUnreachableWhenSuperclassIsAny]
from typing import Any

# This can happen if we're importing a class from a missing module
Parent: Any
class Child(Parent):
    def foo(self) -> int:
        reveal_type(self)       # N: Revealed type is "__main__.Child"
        if self is None:
            reveal_type(self)
            return None
        reveal_type(self)       # N: Revealed type is "__main__.Child"
        return 3

    def bar(self) -> int:
        if 1:
            self = super(Child, self).something()
            reveal_type(self)       # N: Revealed type is "__main__.Child"
            if self is None:
                reveal_type(self)
                return None
            reveal_type(self)       # N: Revealed type is "__main__.Child"
            return 3
[builtins fixtures/isinstance.pyi]

[case testUnreachableWhenSuperclassIsAnyNoStrictOptional]
# flags: --no-strict-optional
from typing import Any

Parent: Any
class Child(Parent):
    def foo(self) -> int:
        reveal_type(self)       # N: Revealed type is "__main__.Child"
        if self is None:
            reveal_type(self)   # N: Revealed type is "None"
            return None
        reveal_type(self)       # N: Revealed type is "__main__.Child"
        return 3
[builtins fixtures/isinstance.pyi]

[case testUnreachableAfterToplevelAssert]
import sys
reveal_type(0)  # N: Revealed type is "Literal[0]?"
assert sys.platform == 'lol'
reveal_type('')  # No error here :-)
[builtins fixtures/ops.pyi]

[case testUnreachableAfterToplevelAssert2]
import sys
reveal_type(0)  # N: Revealed type is "Literal[0]?"
assert sys.version_info[0] == 1
reveal_type('')  # No error here :-)
[builtins fixtures/ops.pyi]

[case testUnreachableAfterToplevelAssert3]
reveal_type(0)  # N: Revealed type is "Literal[0]?"
MYPY = False
assert not MYPY
reveal_type('')  # No error here :-)
[builtins fixtures/ops.pyi]

[case testUnreachableAfterToplevelAssert4]
# flags: --always-false NOPE
reveal_type(0)  # N: Revealed type is "Literal[0]?"
NOPE = False
assert NOPE
reveal_type('')  # No error here :-)
[builtins fixtures/ops.pyi]

[case testUnreachableAfterToplevelAssertImport]
import foo
foo.bar()  # E: "object" has no attribute "bar"
[file foo.py]
import sys
assert sys.platform == 'lol'
def bar() -> None: pass
[builtins fixtures/ops.pyi]

[case testUnreachableAfterToplevelAssertImport2]
# flags: --platform lol
import foo
foo.bar()  # No error :-)
[file foo.py]
import sys
assert sys.platform == 'lol'
def bar() -> None: pass
[builtins fixtures/ops.pyi]

[case testUnreachableAfterToplevelAssertImportThirdParty]
# flags: --platform unknown
import sys
assert sys.platform == 'linux'
import does_not_exist
[builtins fixtures/ops.pyi]

[case testUnreachableAfterToplevelAssertImportThirdParty2]
# flags: --platform unknown
import sys
import bad; assert sys.platform == 'linux'; import does_not_exist
[builtins fixtures/ops.pyi]
[out]
main:3: error: Cannot find implementation or library stub for module named "bad"
main:3: note: See https://mypy.readthedocs.io/en/stable/running_mypy.html#missing-imports

[case testUnreachableAfterToplevelAssertNotInsideIf]
import sys
if sys.version_info[0] >= 2:
    assert sys.platform == 'lol'
    reveal_type('')  # N: Revealed type is "Literal['']?"
reveal_type('')  # N: Revealed type is "Literal['']?"
[builtins fixtures/ops.pyi]

[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)
    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]
# flags: --warn-unreachable
def foo(x: int) -> None:
    reveal_type(x)  # N: Revealed type is "builtins.int"
    return
    reveal_type(x)  # E: Statement is unreachable

[case testUnreachableFlagTryBlocks]
# flags: --warn-unreachable

def foo(x: int) -> int:
    try:
        reveal_type(x)      # N: Revealed type is "builtins.int"
        return x
        reveal_type(x)      # E: Statement is unreachable
    finally:
        reveal_type(x)      # N: Revealed type is "builtins.int"
        if True:
            reveal_type(x)  # N: Revealed type is "builtins.int"
        else:
            reveal_type(x)  # E: Statement is unreachable

def bar(x: int) -> int:
    try:
        if True:
            raise Exception()
        reveal_type(x)      # E: Statement is unreachable
    except:
        reveal_type(x)      # N: Revealed type is "builtins.int"
        return x
    else:
        reveal_type(x)      # E: Statement is unreachable

def baz(x: int) -> int:
    try:
        reveal_type(x)      # N: Revealed type is "builtins.int"
    except:
        # Mypy assumes all lines could throw an exception
        reveal_type(x)      # N: Revealed type is "builtins.int"
        return x
    else:
        reveal_type(x)      # N: Revealed type is "builtins.int"
        return x
[builtins fixtures/exception.pyi]

[case testUnreachableFlagIgnoresSemanticAnalysisUnreachable]
# flags: --warn-unreachable --python-version 3.9 --platform win32 --always-false FOOBAR
import sys
from typing import TYPE_CHECKING

def f1(x: int) -> None:
    if TYPE_CHECKING:
        reveal_type(x)  # N: Revealed type is "builtins.int"
    else:
        reveal_type(x)

def f2(x: int) -> None:
    if not TYPE_CHECKING:
        reveal_type(x)
    else:
        reveal_type(x)  # N: Revealed type is "builtins.int"

def f3(x: int) -> None:
    if sys.platform == 'darwin':
        reveal_type(x)
    else:
        reveal_type(x)  # N: Revealed type is "builtins.int"

def f4(x: int) -> None:
    if sys.platform == 'win32':
        reveal_type(x)  # N: Revealed type is "builtins.int"
    else:
        reveal_type(x)

def f5(x: int) -> None:
    if sys.version_info == (2, 7):
        reveal_type(x)
    else:
        reveal_type(x)  # N: Revealed type is "builtins.int"

def f6(x: int) -> None:
    if sys.version_info >= (3, 9):
        reveal_type(x)  # N: Revealed type is "builtins.int"
    else:
        reveal_type(x)

    if sys.version_info >= (3, 10):
        reveal_type(x)
    else:
        reveal_type(x)  # N: Revealed type is "builtins.int"

def f7(x: int) -> None:
    FOOBAR = ""
    if FOOBAR:
        reveal_type(x)
    else:
        reveal_type(x)  # N: Revealed type is "builtins.int"
[builtins fixtures/ops.pyi]
[typing fixtures/typing-medium.pyi]

[case testUnreachableFlagIgnoresSemanticAnalysisExprUnreachable]
# flags: --warn-unreachable --always-false FOOBAR
import sys
from typing import TYPE_CHECKING

FOOBAR = ""

def foo() -> bool: ...

lst = [1, 2, 3]

a = FOOBAR and foo()
b = (not FOOBAR) or foo()
c = 1 if FOOBAR else 2
d = [x for x in lst if FOOBAR]
[builtins fixtures/list.pyi]
[typing fixtures/typing-medium.pyi]

[case testUnreachableFlagOkWithDeadStatements]
# flags: --warn-unreachable
from typing import NoReturn
def assert_never(x: NoReturn) -> NoReturn:
    assert False

def nonthrowing_assert_never(x: NoReturn) -> None: ...

def expect_str(x: str) -> str: pass

x: int
if False:
    assert False
    reveal_type(x)  # E: Statement is unreachable

if False:
    raise Exception()
    reveal_type(x)  # E: Statement is unreachable

if False:
    assert_never(x)
    reveal_type(x)  # E: Statement is unreachable

if False:
    nonthrowing_assert_never(x)  # E: Statement is unreachable
    reveal_type(x)

if False:
    # Ignore obvious type errors
    assert_never(expect_str(x))
    reveal_type(x)  # E: Statement is unreachable
[builtins fixtures/exception.pyi]

[case testNeverVariants]
from typing import Never
from typing_extensions import Never as TENever
from typing import NoReturn
from typing_extensions import NoReturn as TENoReturn
from mypy_extensions import NoReturn as MENoReturn

bottom1: Never
reveal_type(bottom1)  # N: Revealed type is "Never"
bottom2: TENever
reveal_type(bottom2)  # N: Revealed type is "Never"
bottom3: NoReturn
reveal_type(bottom3)  # N: Revealed type is "Never"
bottom4: TENoReturn
reveal_type(bottom4)  # N: Revealed type is "Never"
bottom5: MENoReturn
reveal_type(bottom5)  # N: Revealed type is "Never"

[builtins fixtures/tuple.pyi]

[case testUnreachableFlagExpressions]
# flags: --warn-unreachable
def foo() -> bool: ...

lst = [1, 2, 3, 4]

a = True or foo()                        # E: Right operand of "or" is never evaluated
b = 42 or False                          # E: Right operand of "or" is never evaluated
d = False and foo()                      # E: Right operand of "and" is never evaluated
e = True or (True or (True or foo()))    # E: Right operand of "or" is never evaluated
f = (True or foo()) or (True or foo())   # E: Right operand of "or" is never evaluated

k = [x for x in lst if isinstance(x, int) or foo()]  # E: Right operand of "or" is never evaluated
[builtins fixtures/isinstancelist.pyi]

[case testUnreachableFlagMiscTestCaseMissingMethod]
# flags: --warn-unreachable

class Case1:
    def test1(self) -> bool:
        return False and self.missing()  # E: Right operand of "and" is never evaluated

    def test2(self) -> bool:
        return not self.property_decorator_missing and self.missing()  # E: Function "property_decorator_missing" could always be true in boolean context \
            # E: Right operand of "and" is never evaluated

    def property_decorator_missing(self) -> bool:
        return True
[builtins fixtures/bool.pyi]

[case testUnreachableFlagWithGenerics]
# flags: --warn-unreachable
from typing import TypeVar, Generic

T1 = TypeVar('T1', bound=int)
T2 = TypeVar('T2', int, str)
T3 = TypeVar('T3', None, str)

def test1(x: T1) -> T1:
    if isinstance(x, int):
        reveal_type(x)  # N: Revealed type is "T1`-1"
    else:
        reveal_type(x)  # E: Statement is unreachable
    return x

def test2(x: T2) -> T2:
    if isinstance(x, int):
        reveal_type(x)  # N: Revealed type is "builtins.int"
    else:
        reveal_type(x)  # N: Revealed type is "builtins.str"

    if False:
        # This is unreachable, but we don't report an error, unfortunately.
        # The presence of the TypeVar with values unfortunately currently shuts
        # down type-checking for this entire function.
        # TODO: Find a way of removing this limitation
        reveal_type(x)

    return x

class Test3(Generic[T2]):
    x: T2

    def func(self) -> None:
        if isinstance(self.x, int):
            reveal_type(self.x)  # N: Revealed type is "builtins.int"
        else:
            reveal_type(self.x)  # N: Revealed type is "builtins.str"

        if False:
            # Same issue as above
            reveal_type(self.x)


class Test4(Generic[T3]):
    def __init__(self, x: T3):
        # https://github.com/python/mypy/issues/9456
        # On TypeVars with value restrictions, we currently have no way
        # of checking a statement for all the type expansions.
        # Thus unreachable warnings are disabled
        if x and False:
            pass
        # This test should fail after this limitation is removed.
        if False and x:
            pass

[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
from typing import Literal, Optional, Iterator, Any
class DoesNotSuppress1:
    def __enter__(self) -> int: ...
    def __exit__(self, exctype: object, excvalue: object, traceback: object) -> Optional[bool]: ...

class DoesNotSuppress2:
    def __enter__(self) -> int: ...
    def __exit__(self, exctype: object, excvalue: object, traceback: object) -> Literal[False]: ...

class DoesNotSuppress3:
    def __enter__(self) -> int: ...
    def __exit__(self, exctype: object, excvalue: object, traceback: object) -> Any: ...

class DoesNotSuppress4:
    def __enter__(self) -> int: ...
    def __exit__(self, exctype: object, excvalue: object, traceback: object) -> None: ...

@contextmanager
def simple() -> Iterator[int]:
    yield 3

def cond() -> bool: ...

def noop() -> None: ...

def f_no_suppress_1a() -> int:
    with DoesNotSuppress1():
        return 3
    noop()              # E: Statement is unreachable

def f_no_suppress_1b() -> int:
    with DoesNotSuppress1():
        if cond():
            return 3
        else:
            return 3
    noop()                  # E: Statement is unreachable

def f_no_suppress_2() -> int:
    with DoesNotSuppress2():
        return 3
    noop()                  # E: Statement is unreachable

def f_no_suppress_3() -> int:
    with DoesNotSuppress3():
        return 3
    noop()                  # E: Statement is unreachable

def f_no_suppress_4() -> int:
    with DoesNotSuppress4():
        return 3
    noop()                  # E: Statement is unreachable

def f_no_suppress_5() -> int:
    with simple():
        return 3
    noop()                  # E: Statement is unreachable

[typing fixtures/typing-medium.pyi]
[builtins fixtures/tuple.pyi]

[case testUnreachableFlagContextManagersSuppressed]
# flags: --warn-unreachable
from contextlib import contextmanager
from typing import Optional, Iterator, Literal, Any

class DoesNotSuppress:
    def __enter__(self) -> int: ...
    def __exit__(self, exctype: object, excvalue: object, traceback: object) -> Optional[bool]: ...

class Suppresses1:
    def __enter__(self) -> int: ...
    def __exit__(self, exctype: object, excvalue: object, traceback: object) -> bool: ...

class Suppresses2:
    def __enter__(self) -> int: ...
    def __exit__(self, exctype: object, excvalue: object, traceback: object) -> Literal[True]: ...

def cond() -> bool: ...

def noop() -> None: ...

def f_suppress_1a() -> int:  # E: Missing return statement
    with Suppresses1():
        return 3
    noop()

def f_suppress_1b() -> int:  # E: Missing return statement
    with Suppresses1():
        if cond():
            return 3
        else:
            return 3
    noop()

def f_suppress_2() -> int:  # E: Missing return statement
    with Suppresses2():
        return 3
    noop()

def f_mix() -> int:         # E: Missing return statement
    with DoesNotSuppress(), Suppresses1(), DoesNotSuppress():
        return 3
    noop()
[typing fixtures/typing-medium.pyi]
[builtins fixtures/tuple.pyi]

[case testUnreachableFlagContextManagersSuppressedNoStrictOptional]
# flags: --warn-unreachable --no-strict-optional
from contextlib import contextmanager
from typing import Optional, Iterator, Literal, Any

class DoesNotSuppress1:
    def __enter__(self) -> int: ...
    def __exit__(self, exctype: object, excvalue: object, traceback: object) -> Optional[bool]: ...

# Normally, this should suppress. But when strict-optional mode is disabled, we can't
# necessarily distinguish between bool and Optional[bool]. So we default to assuming
# no suppression, since that's what most context managers will do.
class DoesNotSuppress2:
    def __enter__(self) -> int: ...
    def __exit__(self, exctype: object, excvalue: object, traceback: object) -> bool: ...

# But if we see Literal[True], it's pretty unlikely the return type is actually meant to
# be 'Optional[Literal[True]]'. So, we optimistically assume this is meant to be suppressing.
class Suppresses:
    def __enter__(self) -> int: ...
    def __exit__(self, exctype: object, excvalue: object, traceback: object) -> Literal[True]: ...

def noop() -> None: ...

def f_no_suppress_1() -> int:
    with DoesNotSuppress1():
        return 3
    noop()  # E: Statement is unreachable

def f_no_suppress_2() -> int:
    with DoesNotSuppress1():
        return 3
    noop()  # E: Statement is unreachable

def f_suppress() -> int:  # E: Missing return statement
    with Suppresses():
        return 3
    noop()
[typing fixtures/typing-medium.pyi]
[builtins fixtures/tuple.pyi]

[case testUnreachableFlagContextAsyncManagersNoSuppress]
# flags: --warn-unreachable
from contextlib import asynccontextmanager
from typing import Optional, AsyncIterator, Literal, Any

class DoesNotSuppress1:
    async def __aenter__(self) -> int: ...
    async def __aexit__(self, exctype: object, excvalue: object, traceback: object) -> Optional[bool]: ...

class DoesNotSuppress2:
    async def __aenter__(self) -> int: ...
    async def __aexit__(self, exctype: object, excvalue: object, traceback: object) -> Literal[False]: ...

class DoesNotSuppress3:
    async def __aenter__(self) -> int: ...
    async def __aexit__(self, exctype: object, excvalue: object, traceback: object) -> Any: ...

class DoesNotSuppress4:
    async def __aenter__(self) -> int: ...
    async def __aexit__(self, exctype: object, excvalue: object, traceback: object) -> None: ...

@asynccontextmanager
async def simple() -> AsyncIterator[int]:
    yield 3

def cond() -> bool: ...

def noop() -> None: ...

async def f_no_suppress_1a() -> int:
    async with DoesNotSuppress1():
        return 3
    noop()              # E: Statement is unreachable

async def f_no_suppress_1b() -> int:
    async with DoesNotSuppress1():
        if cond():
            return 3
        else:
            return 3
    noop()                  # E: Statement is unreachable

async def f_no_suppress_2() -> int:
    async with DoesNotSuppress2():
        return 3
    noop()                  # E: Statement is unreachable

async def f_no_suppress_3() -> int:
    async with DoesNotSuppress3():
        return 3
    noop()                  # E: Statement is unreachable

async def f_no_suppress_4() -> int:
    async with DoesNotSuppress4():
        return 3
    noop()                  # E: Statement is unreachable

async def f_no_suppress_5() -> int:
    async with simple():
        return 3
    noop()                  # E: Statement is unreachable

[typing fixtures/typing-full.pyi]
[builtins fixtures/tuple.pyi]

[case testUnreachableFlagContextAsyncManagersSuppressed]
# flags: --warn-unreachable
from contextlib import asynccontextmanager
from typing import Optional, AsyncIterator, Literal, Any

class DoesNotSuppress:
    async def __aenter__(self) -> int: ...
    async def __aexit__(self, exctype: object, excvalue: object, traceback: object) -> Optional[bool]: ...

class Suppresses1:
    async def __aenter__(self) -> int: ...
    async def __aexit__(self, exctype: object, excvalue: object, traceback: object) -> bool: ...

class Suppresses2:
    async def __aenter__(self) -> int: ...
    async def __aexit__(self, exctype: object, excvalue: object, traceback: object) -> Literal[True]: ...

def cond() -> bool: ...

def noop() -> None: ...

async def f_suppress_1() -> int:  # E: Missing return statement
    async with Suppresses1():
        return 3
    noop()

async def f_suppress_2() -> int:  # E: Missing return statement
    async with Suppresses1():
        if cond():
            return 3
        else:
            return 3
    noop()

async def f_suppress_3() -> int:  # E: Missing return statement
    async with Suppresses2():
        return 3
    noop()

async def f_mix() -> int:         # E: Missing return statement
    async with DoesNotSuppress(), Suppresses1(), DoesNotSuppress():
        return 3
    noop()
[typing fixtures/typing-full.pyi]
[builtins fixtures/tuple.pyi]

[case testUnreachableFlagContextAsyncManagersAbnormal]
# flags: --warn-unreachable
from contextlib import asynccontextmanager
from typing import Optional, AsyncIterator, Literal, Any

class RegularManager:
    def __enter__(self) -> int: ...
    def __exit__(self, exctype: object, excvalue: object, traceback: object) -> bool: ...

class AsyncManager:
    async def __aenter__(self) -> int: ...
    async def __aexit__(self, exctype: object, excvalue: object, traceback: object) -> bool: ...

def noop() -> None: ...

async def f_bad_1() -> int:
    async with RegularManager():  # E: "RegularManager" has no attribute "__aenter__"; maybe "__enter__"? \
                                  # E: "RegularManager" has no attribute "__aexit__"; maybe "__exit__"?
        return 3
    noop()                        # E: Statement is unreachable

def f_bad_2() -> int:
    with AsyncManager():  # E: "AsyncManager" has no attribute "__enter__"; maybe "__aenter__"? \
                          # E: "AsyncManager" has no attribute "__exit__"; maybe "__aexit__"?
        return 3
    noop()                # E: Statement is unreachable

# TODO: We should consider reporting an error when the user tries using
# context manager with malformed signatures instead of silently continuing.

class RegularManagerMalformedSignature:
    def __enter__(self) -> int: ...
    def __exit__(self, exctype: object, excvalue: object, traceback: object) -> object: ...

class AsyncManagerMalformedSignature:
    async def __aenter__(self) -> int: ...
    async def __aexit__(self, exctype: object, excvalue: object, traceback: object) -> object: ...

def f_malformed_1() -> int:
    with RegularManagerMalformedSignature():
        return 3
    noop()                  # E: Statement is unreachable

async def f_malformed_2() -> int:
    async with AsyncManagerMalformedSignature():
        return 3
    noop()                  # E: Statement is unreachable

[typing fixtures/typing-full.pyi]
[builtins fixtures/tuple.pyi]

[case testUnreachableUntypedFunction]
# flags: --warn-unreachable

def test_untyped_fn(obj):
    assert obj.prop is True

    obj.update(prop=False)
    obj.reload()

    assert obj.prop is False
    reveal_type(obj.prop)

def test_typed_fn(obj) -> None:
    assert obj.prop is True

    obj.update(prop=False)
    obj.reload()

    assert obj.prop is False
    reveal_type(obj.prop)  # E: Statement is unreachable

[case testUnreachableCheckedUntypedFunction]
# flags: --warn-unreachable --check-untyped-defs

def test_untyped_fn(obj):
    assert obj.prop is True

    obj.update(prop=False)
    obj.reload()

    assert obj.prop is False
    reveal_type(obj.prop)  # E: Statement is unreachable

[case testConditionalTypeVarException]
# every part of this test case was necessary to trigger the crash
import sys
from typing import TypeVar

T = TypeVar("T", int, str)

def f(t: T) -> None:
    if sys.platform == "lol":
        try:
            pass
        except BaseException as e:
            pass
[builtins fixtures/dict.pyi]


[case testUnreachableLiteral]
# flags: --warn-unreachable
from typing import Literal

def nope() -> Literal[False]: ...

def f() -> None:
    if nope():
        x = 1  # E: Statement is unreachable
[builtins fixtures/dict.pyi]

[case testUnreachableLiteralFrom__bool__]
# flags: --warn-unreachable
from typing import Literal

class Truth:
    def __bool__(self) -> Literal[True]: ...

class Lie:
    def __bool__(self) -> Literal[False]: ...

class Maybe:
    def __bool__(self) -> Literal[True | False]: ...

t = Truth()
if t:
    x = 1
else:
    x = 2  # E: Statement is unreachable

if Lie():
    x = 3  # E: Statement is unreachable

if Maybe():
    x = 4


def foo() -> bool: ...

y = Truth() or foo()  # E: Right operand of "or" is never evaluated
z = Lie() and foo()  # E: Right operand of "and" is never evaluated
[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]

[case testUnreachableNoReturnBinaryOps]
# flags: --warn-unreachable
from typing import NoReturn

a: NoReturn
a and 1  # E: Right operand of "and" is never evaluated
a or 1  # E: Right operand of "or" is never evaluated
a or a  # E: Right operand of "or" is never evaluated
1 and a and 1  # E: Right operand of "and" is never evaluated
a and a  # E: Right operand of "and" is never evaluated
[builtins fixtures/exception.pyi]

[case testUnreachableFlagWithTerminalBranchInDeferredNode]
# flags: --warn-unreachable
from typing import NoReturn

def assert_never(x: NoReturn) -> NoReturn: ...

def force_forward_ref() -> int:
    return 4

def f(value: None) -> None:
    x
    if value is not None:
        assert_never(value)

x = force_forward_ref()
[builtins fixtures/exception.pyi]

[case testSetitemNoReturn]
# flags: --warn-unreachable
from typing import NoReturn
class Foo:
    def __setitem__(self, key: str, value: str) -> NoReturn:
        raise Exception
Foo()['a'] = 'a'
x = 0  # E: Statement is unreachable
[builtins fixtures/exception.pyi]

[case TestNoImplicNoReturnFromError]
# flags: --warn-unreachable
from typing import TypeVar

T = TypeVar("T")
class Foo:
    def __setitem__(self, key: str, value: str) -> T:  # E: A function returning TypeVar should receive at least one argument containing the same TypeVar
        raise Exception

def f() -> None:
    Foo()['a'] = 'a'
    x = 0 # This should not be reported as unreachable
[builtins fixtures/exception.pyi]

[case testIntentionallyEmptyGeneratorFunction]
# flags: --warn-unreachable
from typing import Generator

def f() -> Generator[None, None, None]:
    return
    yield

[case testIntentionallyEmptyGeneratorFunction_None]
# flags: --warn-unreachable
from typing import Generator

def f() -> Generator[None, None, None]:
    return None
    yield None

[case testLambdaNoReturn]
# flags: --warn-unreachable
from typing import Callable, NoReturn

def foo() -> NoReturn:
    raise

f1 = lambda: foo()
x = 0  # not unreachable

f2: Callable[[], NoReturn] = lambda: foo()
x = 0  # not unreachable

[case testAttributeNoReturn]
# flags: --warn-unreachable
from typing import Optional, NoReturn, TypeVar

def foo() -> NoReturn:
    raise

T = TypeVar("T")
def bar(x: Optional[list[T]] = None) -> T:
    ...

reveal_type(bar().attr)  # N: Revealed type is "Never"
1  # not unreachable
reveal_type(foo().attr)  # N: Revealed type is "Never"
1  # E: Statement is unreachable

[case testIgnoreReturningNotImplemented]
# flags: --warn-unreachable

class C:
    def __add__(self, o: C) -> C:
        if not isinstance(o, C):
            return NotImplemented
        return C()
    def __sub__(self, o: C) -> C:
        if isinstance(o, C):
            return C()
        return NotImplemented
    def __mul__(self, o: C) -> C:
        if isinstance(o, C):
            return C()
        else:
            return NotImplemented
[builtins fixtures/isinstance.pyi]

[case testIgnoreReturningNotImplementedSimple]
# flags: --warn-unreachable
-- This behavior may or may not actually be desirable.
-- This test just serves to document mypy's current behavior.
-- And mypy's handling of NotImplemented has long been known
-- to be suboptimal, eg https://github.com/python/mypy/issues/363.
-- If you change this behavior, please change the corresponding docs
-- https://mypy.readthedocs.io/en/stable/command_line.html#cmdoption-mypy-warn-unreachable
def foo() -> None:
    return None
    return NotImplemented #no error
    return None # E: Statement is unreachable
[builtins fixtures/isinstance.pyi]

[case testPassAndEllipsisUnreachable]
# flags: --warn-unreachable
def f() -> None:
    return
    pass  # E: Statement is unreachable

def g() -> None:
    return
    ...  # E: Statement is unreachable
[builtins fixtures/isinstance.pyi]

[case testUnreachableStatementPrettyHighlighting]
# flags: --warn-unreachable --pretty
def x() -> None:
    assert False
    if 5:
        pass
[out]
main:4: error: Statement is unreachable
        if 5:
        ^~~~~

[case testReachableEqualityNarrowingAny]
# flags: --warn-unreachable
# https://github.com/python/mypy/issues/20532
from __future__ import annotations
from typing import Any

def print(s: str): pass

def main(contents: Any, commit: str | None) -> None:
    if (
        contents.get("commit") == commit
        and (commit is not None or print("can_be_reached"))
    ):
        pass

main({"commit": None}, None)
[builtins fixtures/tuple.pyi]