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

[case testDefinedInOneBranch]
# flags: --enable-error-code possibly-undefined
if int():
    a = 1
else:
    x = 2
z = a + 1  # E: Name "a" may be undefined
z = a + 1  # We only report the error on first occurrence.

[case testElif]
# flags: --enable-error-code possibly-undefined
if int():
    a = 1
elif int():
    a = 2
else:
    x = 3

z = a + 1  # E: Name "a" may be undefined

[case testUsedInIf]
# flags: --enable-error-code possibly-undefined
if int():
    y = 1
if int():
    x = y  # E: Name "y" may be undefined

[case testDefinedInAllBranches]
# flags: --enable-error-code possibly-undefined
if int():
    a = 1
elif int():
    a = 2
else:
    a = 3
z = a + 1

[case testOmittedElse]
# flags: --enable-error-code possibly-undefined
if int():
    a = 1
z = a + 1  # E: Name "a" may be undefined

[case testUpdatedInIf]
# flags: --enable-error-code possibly-undefined
# Variable a is already defined. Just updating it in an "if" is acceptable.
a = 1
if int():
    a = 2
z = a + 1

[case testNestedIf]
# flags: --enable-error-code possibly-undefined
if int():
    if int():
        a = 1
        x = 1
        x = x + 1
    else:
        a = 2
    b = a + x  # E: Name "x" may be undefined
    b = b + 1
else:
    b = 2
z = a + b  # E: Name "a" may be undefined

[case testVeryNestedIf]
# flags: --enable-error-code possibly-undefined
if int():
    if int():
        if int():
            a = 1
        else:
            a = 2
        x = a
    else:
        a = 2
    b = a
else:
    b = 2
z = a + b  # E: Name "a" may be undefined

[case testTupleUnpack]
# flags: --enable-error-code possibly-undefined

if int():
    (x, y) = (1, 2)
else:
    [y, z] = [1, 2]
a = y + x  # E: Name "x" may be undefined
a = y + z  # E: Name "z" may be undefined

[case testIndexExpr]
# flags: --enable-error-code possibly-undefined

if int():
    *x, y = (1, 2)
else:
    x = [1, 2]
a = x  # No error.
b = y  # E: Name "y" may be undefined

[case testRedefined]
# flags: --enable-error-code possibly-undefined
y = 3
if int():
    if int():
        y = 2
    x = y + 2
else:
    if int():
        y = 2
    x = y + 2

x = y + 2

[case testFunction]
# flags: --enable-error-code possibly-undefined
def f0() -> None:
    if int():
        def some_func() -> None:
            pass

    some_func()  # E: Name "some_func" may be undefined

def f1() -> None:
    if int():
        def some_func() -> None:
            pass
    else:
        def some_func() -> None:
            pass

    some_func()  # No error.

[case testLambda]
# flags: --enable-error-code possibly-undefined
def f0(b: bool) -> None:
    if b:
        fn = lambda: 2
    y = fn   # E: Name "fn" may be undefined

[case testUsedBeforeDefClass]
# flags: --enable-error-code possibly-undefined --enable-error-code used-before-def
def f(x: A):  # No error here.
    pass
y = A()  # E: Name "A" is used before definition
class A: pass

[case testClassScope]
# flags: --enable-error-code possibly-undefined --enable-error-code used-before-def
class C:
    x = 0
    def f0(self) -> None: pass

    def f2(self) -> None:
        f0()  # No error.
        self.f0()  # No error.

f0()  # E: Name "f0" is used before definition
def f0() -> None: pass
y = x  # E: Name "x" is used before definition
x = 1

[case testClassInsideFunction]
# flags: --enable-error-code possibly-undefined --enable-error-code used-before-def
def f() -> None:
    class C: pass

c = C()  # E: Name "C" is used before definition
class C: pass

[case testUsedBeforeDefFunc]
# flags: --enable-error-code possibly-undefined --enable-error-code used-before-def
foo() # E: Name "foo" is used before definition
def foo(): pass
[case testGenerator]
# flags: --enable-error-code possibly-undefined
if int():
    a = 3
s = [a + 1 for a in [1, 2, 3]]
x = a  # E: Name "a" may be undefined

[case testScope]
# flags: --enable-error-code possibly-undefined
def foo() -> None:
    if int():
        y = 2

if int():
    y = 3
x = y  # E: Name "y" may be undefined

[case testVarDefinedInOuterScopeUpdated]
# flags: --enable-error-code possibly-undefined --enable-error-code used-before-def
def f0() -> None:
    global x
    y = x
    x = 1  # No error.

x = 2

[case testNonlocalVar]
# flags: --enable-error-code possibly-undefined --enable-error-code used-before-def
def f0() -> None:
    x = 2

    def inner() -> None:
        nonlocal x
        y = x
        x = 1  # No error.

[case testGlobalDeclarationAfterUsage]
# flags: --enable-error-code possibly-undefined --enable-error-code used-before-def
def f0() -> None:
    y = x  # E: Name "x" is used before definition
    global x
    x = 1  # No error.

x = 2

[case testVarDefinedInOuterScope]
# flags: --enable-error-code possibly-undefined --enable-error-code used-before-def
def f0() -> None:
  global x
  y = x  # We do not detect such errors right now.

f0()
x = 1

[case testDefinedInOuterScopeNoError]
# flags: --enable-error-code possibly-undefined --enable-error-code used-before-def
def foo() -> None:
    bar()

def bar() -> None:
    foo()

[case testClassFromOuterScopeRedefined]
# flags: --enable-error-code possibly-undefined --enable-error-code used-before-def
class c: pass

def f0() -> None:
    s = c()  # E: Name "c" is used before definition
    class c: pass

def f1() -> None:
    s = c()  # No error.

def f2() -> None:
    s = c()  # E: Name "c" is used before definition
    if int():
        class c: pass

glob = c()
def f3(x: c = glob) -> None:
    glob = 123

[case testVarFromOuterScopeRedefined]
# flags: --enable-error-code possibly-undefined --enable-error-code used-before-def
x = 0

def f0() -> None:
    y = x  # E: Name "x" is used before definition
    x = 0

def f1() -> None:
    y = x  # No error.

def f2() -> None:
    y = x  # E: Name "x" is used before definition
    global x

def f3() -> None:
    global x
    y = x  # No error.

def f4() -> None:
    if int():
        x = 0
    y = x  # E: Name "x" may be undefined

[case testFuncParams]
# flags: --enable-error-code possibly-undefined
def foo(a: int) -> None:
    if int():
        a = 2
    x = a

[case testWhile]
# flags: --enable-error-code possibly-undefined
while int():
    a = 1

x = a  # E: Name "a" may be undefined

while int():
    b = 1
else:
    b = 2

y = b  # No error.

while True:
    c = 1
    if int():
        break
y = c  # No error.

# This while loop doesn't have a `break` inside, so we know that the else must always get executed.
while int():
    pass
else:
    d = 1
y = d  # No error.

while int():
    if int():
        break
else:
    e = 1
# If a while loop has a `break`, it's possible that the else didn't get executed.
y = e  # E: Name "e" may be undefined

while int():
    while int():
        if int():
            break
    else:
        f = 1
else:
    g = 2

y = f  # E: Name "f" may be undefined
y = g

[case testForLoop]
# flags: --enable-error-code possibly-undefined
for x in [1, 2, 3]:
    if x:
        x = 1
    y = x
else:
    z = 2

a = z + y  # E: Name "y" may be undefined

[case testReturn]
# flags: --enable-error-code possibly-undefined
def f1() -> int:
    if int():
        x = 1
    else:
        return 0
    return x

def f2() -> int:
    if int():
        x = 1
    elif int():
        return 0
    else:
        x = 2
    return x

def f3() -> int:
    if int():
        x = 1
    elif int():
        return 0
    else:
        y = 2
    return x  # E: Name "x" may be undefined

def f4() -> int:
    if int():
        x = 1
    elif int():
        return 0
    else:
        return 0
    return x

def f5() -> int:
    # This is a test against crashes.
    if int():
        return 1
    if int():
        return 2
    else:
        return 3
    return 1

def f6() -> int:
    if int():
        x = 0
        return x
    return x  # E: Name "x" may be undefined

[case testDefinedDifferentBranchUsedBeforeDef]
# flags: --enable-error-code possibly-undefined --enable-error-code used-before-def

def f0() -> None:
    if int():
        x = 0
    else:
        y = x  # E: Name "x" is used before definition
        z = x  # E: Name "x" is used before definition

def f1() -> None:
    x = 1
    if int():
        x = 0
    else:
        y = x  # No error.

def f2() -> None:
    if int():
        x = 0
    elif int():
        y = x  # E: Name "x" is used before definition
    else:
        y = x  # E: Name "x" is used before definition
        if int():
            z = x  # E: Name "x" is used before definition
            x = 1
        else:
            x = 2
        w = x  # No error.

[case testPossiblyUndefinedLoop]
# flags: --enable-error-code possibly-undefined --enable-error-code used-before-def

def f0() -> None:
    first_iter = True
    for i in [0, 1]:
        if first_iter:
            first_iter = False
            x = 0
        elif int():
            # This is technically a false positive but mypy isn't smart enough for this yet.
            y = x  # E: Name "x" may be undefined
        else:
            y = x  # E: Name "x" may be undefined
            if int():
                z = x  # E: Name "x" may be undefined
                x = 1
            else:
                x = 2
            w = x  # No error.

def f1() -> None:
    while True:
        if int():
            x = 0
        else:
            y = x  # E: Name "x" may be undefined
            z = x  # E: Name "x" may be undefined

def f2() -> None:
    for i in [0, 1]:
        x = i
    else:
        y = x  # E: Name "x" may be undefined

def f3() -> None:
    while int():
        x = 1
    else:
        y = x  # E: Name "x" may be undefined

def f4() -> None:
    while int():
        y = x  # E: Name "x" may be undefined
        x: int = 1

[case testAssert]
# flags: --enable-error-code possibly-undefined
def f1() -> int:
    if int():
        x = 1
    else:
        assert False, "something something"
    return x

def f2() -> int:
    if int():
        x = 1
    elif int():
        assert False
    else:
        y = 2
    return x  # E: Name "x" may be undefined

[case testRaise]
# flags: --enable-error-code possibly-undefined
def f1() -> int:
    if int():
        x = 1
    else:
        raise BaseException("something something")
    return x

def f2() -> int:
    if int():
        x = 1
    elif int():
        raise BaseException("something something")
    else:
        y = 2
    return x  # E: Name "x" may be undefined
[builtins fixtures/exception.pyi]

[case testContinue]
# flags: --enable-error-code possibly-undefined
def f1() -> int:
    while int():
        if int():
            x = 1
        else:
            continue
        y = x
    else:
        x = 2
    return x

def f2() -> int:
    while int():
        if int():
            x = 1
        elif int():
            pass
        else:
            continue
        y = x  # E: Name "x" may be undefined
    return x  # E: Name "x" may be undefined

def f3() -> None:
    while True:
        if int():
            x = 2
        elif int():
            continue
        else:
            continue
        y = x

[case testBreak]
# flags: --enable-error-code possibly-undefined
def f1() -> None:
    while int():
        if int():
            x = 1
        else:
            break
        y = x  # No error -- x is always defined.

def f2() -> None:
    while int():
        if int():
            x = 1
        elif int():
            pass
        else:
            break
        y = x  # E: Name "x" may be undefined

def f3() -> None:
    while int():
        x = 1
        while int():
            if int():
                x = 2
            else:
                break
        y = x
    z = x  # E: Name "x" may be undefined

[case testTryBasic]
# flags: --enable-error-code possibly-undefined --enable-error-code used-before-def
def f1() -> int:
    try:
        x = 1
    except:
        pass
    return x  # E: Name "x" may be undefined

def f2() -> int:
    try:
        pass
    except:
        x = 1
    return x  # E: Name "x" may be undefined

def f3() -> int:
    try:
        x = 1
    except:
        y = x  # E: Name "x" may be undefined
    return x  # E: Name "x" may be undefined

def f4() -> int:
    try:
        x = 1
    except:
        return 0
    return x

def f5() -> int:
    try:
        x = 1
    except:
        raise
    return x

def f6() -> None:
    try:
        pass
    except BaseException as exc:
        x = exc  # No error.
        exc = BaseException()
    # This case is covered by the other check, not by possibly undefined check.
    y = exc # E: Trying to read deleted variable "exc"

def f7() -> int:
    try:
        if int():
            x = 1
        assert False
    except:
        pass
    return x  # E: Name "x" may be undefined
[builtins fixtures/exception.pyi]

[case testTryMultiExcept]
# flags: --enable-error-code possibly-undefined
def f1() -> int:
    try:
        x = 1
    except BaseException:
        x = 2
    except:
        x = 3
    return x

def f2() -> int:
    try:
        x = 1
    except BaseException:
        pass
    except:
        x = 3
    return x  # E: Name "x" may be undefined
[builtins fixtures/exception.pyi]

[case testTryFinally]
# flags: --enable-error-code possibly-undefined --enable-error-code used-before-def
def f1() -> int:
    try:
        x = 1
    finally:
        x = 2
    return x

def f2() -> int:
    try:
        pass
    except:
        pass
    finally:
        x = 2
    return x

def f3() -> int:
    try:
        x = 1
    except:
        pass
    finally:
        y = x  # E: Name "x" may be undefined
    return x

def f4() -> int:
    try:
        x = 0
    except BaseException:
        raise
    finally:
        y = x  # E: Name "x" may be undefined
    return y

def f5() -> int:
    try:
        if int():
            x = 1
        else:
            return 0
    finally:
        pass
    return x  # No error.

def f6() -> int:
    try:
        if int():
            x = 1
        else:
            return 0
    finally:
        a = x  # E: Name "x" may be undefined
    return a
[builtins fixtures/exception.pyi]

[case testTryElse]
# flags: --enable-error-code possibly-undefined
def f1() -> int:
    try:
        return 0
    except BaseException:
        x = 1
    else:
        x = 2
    finally:
        y = x
    return y

def f2() -> int:
    try:
        pass
    except:
        x = 1
    else:
        x = 2
    return x

def f3() -> int:
    try:
        pass
    except:
        x = 1
    else:
        pass
    return x  # E: Name "x" may be undefined

def f4() -> int:
    try:
        x = 1
    except:
        x = 2
    else:
        pass
    return x

def f5() -> int:
    try:
        pass
    except:
        x = 1
    else:
        return 1
    return x
[builtins fixtures/exception.pyi]

[case testNoReturn]
# flags: --enable-error-code possibly-undefined

from typing import NoReturn
def fail() -> NoReturn:
    assert False

def f() -> None:
    if int():
        x = 1
    elif int():
        x = 2
        y = 3
    else:
        # This has a NoReturn type, so we can skip it.
        fail()
    z = y  # E: Name "y" may be undefined
    z = x

[case testDictComprehension]
# flags: --enable-error-code possibly-undefined

def f() -> None:
    for _ in [1, 2]:
        key = 2
        val = 2

    x = (
        key,  # E: Name "key" may be undefined
        val,  # E: Name "val" may be undefined
    )

    d = [(0, "a"), (1, "b")]
    {val: key for key, val in d}
[builtins fixtures/dict.pyi]

[case testWithStmt]
# flags: --enable-error-code possibly-undefined
from contextlib import contextmanager

@contextmanager
def ctx(*args):
    yield 1

def f() -> None:
    if int():
        a = b = 1
        x = 1

    with ctx() as a, ctx(a) as b, ctx(x) as x:  # E: Name "x" may be undefined
        c = a
        c = b
    d = a
    d = b
[builtins fixtures/tuple.pyi]

[case testUnreachable]
# flags: --enable-error-code possibly-undefined --enable-error-code used-before-def
import typing

def f0() -> None:
    if typing.TYPE_CHECKING:
        x = 1
    elif int():
        y = 1
    else:
        y = 2
    a = x

def f1() -> None:
    if not typing.TYPE_CHECKING:
        pass
    else:
        z = 1
    a = z

def f2() -> None:
    if typing.TYPE_CHECKING:
        x = 1
    else:
        y = x
[typing fixtures/typing-medium.pyi]

[case testUsedBeforeDef]
# flags: --enable-error-code used-before-def

def f0() -> None:
    x = y  # E: Name "y" is used before definition
    y: int = 1

def f2() -> None:
    if int():
        pass
    else:
        # No used-before-def error.
        y = z  # E: Name "z" is not defined

    def inner2() -> None:
        z = 0

def f3() -> None:
    if int():
        pass
    else:
        y = z  # E: Name "z" is used before definition
    z: int = 2

def f4() -> None:
    if int():
        pass
    else:
        y = z  # E: Name "z" is used before definition
        x = z  # E: Name "z" is used before definition
    z: int = 2

[case testUsedBeforeDefImportsBasicImportNoError]
# flags: --enable-error-code used-before-def --enable-error-code possibly-undefined --disable-error-code no-redef
import foo  # type: ignore

a = foo  # No error.
foo: int = 1

[case testUsedBeforeDefImportsDotImport]
# flags: --enable-error-code used-before-def --enable-error-code possibly-undefined --disable-error-code no-redef
import x.y  # type: ignore

a = y  # E: Name "y" is used before definition
y: int = 1

b = x  # No error.
x: int = 1

c = x.y  # No error.
x: int = 1

[case testUsedBeforeDefImportBasicRename]
# flags: --enable-error-code used-before-def --disable-error-code=no-redef
import x.y as z  # type: ignore
from typing import Any

a = z  # No error.
z: int = 1

a = x  # E: Name "x" is used before definition
x: int = 1

a = y  # E: Name "y" is used before definition
y: int = 1

[case testUsedBeforeDefImportFrom]
# flags: --enable-error-code used-before-def --disable-error-code no-redef
from foo import x  # type: ignore

a = x  # No error.
x: int = 1

[case testUsedBeforeDefImportFromRename]
# flags: --enable-error-code used-before-def --disable-error-code no-redef
from foo import x as y  # type: ignore

a = y  # No error.
y: int = 1

a = x  # E: Name "x" is used before definition
x: int = 1

[case testUsedBeforeDefFunctionDeclarations]
# flags: --enable-error-code used-before-def

def f0() -> None:
    def inner() -> None:
        pass

    inner()  # No error.
    inner = lambda: None

[case testUsedBeforeDefBuiltinsFunc]
# flags: --enable-error-code used-before-def

def f0() -> None:
    s = type(123)  # E: Name "type" is used before definition
    type = "abc"
    a = type

def f1() -> None:
    s = type(123)

[case testUsedBeforeDefBuiltinsGlobal]
# flags: --enable-error-code used-before-def

s = type(123)
type = "abc"
a = type

[case testUsedBeforeDefBuiltinsClass]
# flags: --enable-error-code used-before-def

class C:
    s = type
    type = s

[case testUsedBeforeDefBuiltinsGenerator]
# flags: --enable-error-code used-before-def

def f0() -> None:
    _ = [type for type in [type("a"), type(1)]]

[case testUsedBeforeDefBuiltinsMultipass]
# flags: --enable-error-code used-before-def

# When doing multiple passes, mypy resolves references slightly differently.
# In this case, it would refer the earlier `type` call to the range class defined below.
_type = type  # No error
_C = C  # E: Name "C" is used before definition
class type: pass
class C: pass

[case testUsedBeforeDefImplicitModuleAttrs]
# flags: --enable-error-code used-before-def
a = __name__  # No error.
__name__ = "abc"

[case testUntypedDef]
# flags: --enable-error-code possibly-undefined --enable-error-code used-before-def

def f():
    if int():
        x = 0
    z = y  # No used-before-def error because def is untyped.
    y = x  # No possibly-undefined error because def is untyped.

[case testUntypedDefCheckUntypedDefs]
# flags: --enable-error-code possibly-undefined --enable-error-code used-before-def --check-untyped-defs

def f():
    if int():
        x = 0
    z = y  # E: Name "y" is used before definition
    y: int = x  # E: Name "x" may be undefined

[case testClassBody]
# flags: --enable-error-code possibly-undefined --enable-error-code used-before-def

class A:
    # The following should not only trigger an error from semantic analyzer, but not the used-before-def check.
    y = x + 1  # E: Name "x" is not defined
    x = 0
    # Same as above but in a loop, which should trigger a possibly-undefined error.
    for _ in [1, 2, 3]:
        b = a + 1  # E: Name "a" is not defined
        a = 0


class B:
    if int():
        x = 0
    else:
        # This type of check is not caught by the semantic analyzer. If we ever update it to catch such issues,
        # we should make sure that errors are not double-reported.
        y = x  # E: Name "x" is used before definition
    for _ in [1, 2, 3]:
        if int():
            a = 0
        else:
            # Same as above but in a loop.
            b = a  # E: Name "a" may be undefined