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Always infer in operator as returning bool #5688

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merged 4 commits into from Feb 1, 2019
Merged

Always infer in operator as returning bool #5688

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5eec1e3
Always infer `in` operator as returning `bool`
Sep 28, 2018
593d423
Fix type error in checkexpr.py
Sep 28, 2018
c97d4dc
Add extra type checking for `in` operator
Sep 29, 2018
a763a44
Merge branch 'master' into in_return_bool
msullivan Feb 1, 2019
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13 changes: 7 additions & 6 deletions mypy/checkexpr.py
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Expand Up @@ -1686,6 +1686,8 @@ def visit_ellipsis(self, e: EllipsisExpr) -> Type:

def visit_op_expr(self, e: OpExpr) -> Type:
"""Type check a binary operator expression."""
if e.op == 'in':
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Does this mean that we won't check type errors within the subexpressions of the in expressions?

Concretely, does mypy still report an error on code like 1 in ([1] + ['x'])?

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The example you gave still produces an error, but just to be on the safe side, I've added some extra type checking, and a test to make sure this is still an error.

return self.bool_type()
if e.op == 'and' or e.op == 'or':
return self.check_boolean_op(e, e)
if e.op == '*' and isinstance(e.left, ListExpr):
Expand Down Expand Up @@ -1718,7 +1720,8 @@ def visit_comparison_expr(self, e: ComparisonExpr) -> Type:
Comparison expressions are type checked consecutive-pair-wise
That is, 'a < b > c == d' is check as 'a < b and b > c and c == d'
"""
result = None # type: Optional[Type]
result = None # type: Optional[Type]
sub_result = None # type: Optional[Type]

# Check each consecutive operand pair and their operator
for left, right, operator in zip(e.operands, e.operands[1:], e.operators):
Expand All @@ -1733,8 +1736,9 @@ def visit_comparison_expr(self, e: ComparisonExpr) -> Type:
# are just to verify whether something is valid typing wise).
local_errors = self.msg.copy()
local_errors.disable_count = 0
sub_result, method_type = self.check_op_local_by_name('__contains__', right_type,
left, e, local_errors)
_, method_type = self.check_op_local_by_name('__contains__', right_type,
left, e, local_errors)
sub_result = self.bool_type()
if isinstance(right_type, PartialType):
# We don't really know if this is an error or not, so just shut up.
pass
Expand All @@ -1748,13 +1752,10 @@ def visit_comparison_expr(self, e: ComparisonExpr) -> Type:
[None],
self.bool_type(),
self.named_type('builtins.function'))
sub_result = self.bool_type()
if not is_subtype(left_type, itertype):
self.msg.unsupported_operand_types('in', left_type, right_type, e)
else:
self.msg.add_errors(local_errors)
if operator == 'not in':
sub_result = self.bool_type()
elif operator in nodes.op_methods:
method = self.get_operator_method(operator)
sub_result, method_type = self.check_op(method, left_type, right, e,
Expand Down
2 changes: 1 addition & 1 deletion test-data/unit/check-dynamic-typing.test
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Expand Up @@ -122,7 +122,7 @@ n = 0

a and d
a or d
c = a in d
c = a in d # E: Incompatible types in assignment (expression has type "bool", variable has type "C")
c = b and d # E: Incompatible types in assignment (expression has type "Union[bool, Any]", variable has type "C")
c = b or d # E: Incompatible types in assignment (expression has type "Union[bool, Any]", variable has type "C")
b = a + d
Expand Down
9 changes: 6 additions & 3 deletions test-data/unit/check-expressions.test
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Expand Up @@ -406,15 +406,18 @@ main:6: error: Unsupported operand types for in ("B" and "D")

[case testNonBooleanContainsReturnValue]

a, b = None, None # type: (A, bool)
a, b, c = None, None, None # type: (A, bool, int)
b = a not in a
b = a in a
c = a not in a # Fail
c = a in a # Fail

class A:
def __contains__(self, x: 'A') -> object: pass
def __contains__(self, x: 'A') -> int: pass
[builtins fixtures/bool.pyi]
[out]
main:4: error: Incompatible types in assignment (expression has type "object", variable has type "bool")
main:5: error: Incompatible types in assignment (expression has type "bool", variable has type "int")
main:6: error: Incompatible types in assignment (expression has type "bool", variable has type "int")

[case testEq]

Expand Down
3 changes: 2 additions & 1 deletion test-data/unit/deps-expressions.test
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Expand Up @@ -303,8 +303,9 @@ class A:
def __contains__(self, x: B) -> int: pass
class B: pass

def f() -> int:
def f() -> bool:
return B() in A()
[builtins fixtures/bool.pyi]
[out]
<m.A.__contains__> -> m.f
<m.A.__init__> -> m.f
Expand Down