def _infer_unaryop(
self: nodes.UnaryOp,
context: InferenceContext | None = None
) -> Generator[InferenceResult | util.BadUnaryOperationMessage, None, None]:
"""Infer what an UnaryOp should return when evaluated."""
for operand in self.operand.infer(context):
try:
yield operand.infer_unary_op(self.op)
except TypeError as exc:
# The operand doesn't support this operation.
yield util.BadUnaryOperationMessage(operand, self.op, exc)
except AttributeError as exc:
meth = protocols.UNARY_OP_METHOD[self.op]
if meth is None:
# `not node`. Determine node's boolean
# value and negate its result, unless it is
# Uninferable, which will be returned as is.
bool_value = operand.bool_value()
if bool_value is not util.Uninferable:
yield nodes.const_factory(not bool_value)
else:
yield util.Uninferable
else:
if not isinstance(operand, (bases.Instance, nodes.ClassDef)):
# The operation was used on something which
# doesn't support it.
yield util.BadUnaryOperationMessage(operand, self.op, exc)
continue
try:
try:
methods = dunder_lookup.lookup(operand, meth)
except AttributeInferenceError:
yield util.BadUnaryOperationMessage(
operand, self.op, exc)
continue
meth = methods[0]
inferred = next(meth.infer(context=context), None)
if inferred is util.Uninferable or not inferred.callable():
continue
context = copy_context(context)
context.boundnode = operand
context.callcontext = CallContext(args=[], callee=inferred)
call_results = inferred.infer_call_result(self,
context=context)
result = next(call_results, None)
if result is None:
# Failed to infer, return the same type.
yield operand
else:
yield result
except AttributeInferenceError as inner_exc:
# The unary operation special method was not found.
yield util.BadUnaryOperationMessage(
operand, self.op, inner_exc)
except InferenceError:
yield util.Uninferable
def infer_call(
self: nodes.Call,
context: InferenceContext | None = None,
**kwargs: Any) -> Generator[InferenceResult, None, InferenceErrorInfo]:
"""infer a Call node by trying to guess what the function returns"""
callcontext = copy_context(context)
callcontext.boundnode = None
if context is not None:
callcontext.extra_context = _populate_context_lookup(
self, context.clone())
for callee in self.func.infer(context):
if callee is util.Uninferable:
yield callee
continue
try:
if hasattr(callee, "infer_call_result"):
callcontext.callcontext = CallContext(args=self.args,
keywords=self.keywords,
callee=callee)
yield from callee.infer_call_result(caller=self,
context=callcontext)
except InferenceError:
continue
return InferenceErrorInfo(node=self, context=context)
def from_call(cls, call_node, context: InferenceContext | None = None):
"""Get a CallSite object from the given Call node.
context will be used to force a single inference path.
"""
# Determine the callcontext from the given `context` object if any.
context = context or InferenceContext()
callcontext = CallContext(call_node.args, call_node.keywords)
return cls(callcontext, context=context)
def _get_binop_contexts(context, left, right):
"""Get contexts for binary operations.
This will return two inference contexts, the first one
for x.__op__(y), the other one for y.__rop__(x), where
only the arguments are inversed.
"""
# The order is important, since the first one should be
# left.__op__(right).
for arg in (right, left):
new_context = context.clone()
new_context.callcontext = CallContext(args=[arg])
new_context.boundnode = None
yield new_context
def getitem(self, index, context=None):
new_context = bind_context_to_node(context, self)
if not context:
context = new_context
method = next(self.igetattr("__getitem__", context=context), None)
# Create a new CallContext for providing index as an argument.
new_context.callcontext = CallContext(args=[index], callee=method)
if not isinstance(method, BoundMethod):
raise InferenceError("Could not find __getitem__ for {node!r}.",
node=self,
context=context)
if len(method.args.arguments) != 2: # (self, index)
raise AstroidTypeError(
"__getitem__ for {node!r} does not have correct signature",
node=self,
context=context,
)
return next(method.infer_call_result(self, new_context), None)
def _infer_method_result_truth(instance, method_name, context):
# Get the method from the instance and try to infer
# its return's truth value.
meth = next(instance.igetattr(method_name, context=context), None)
if meth and hasattr(meth, "infer_call_result"):
if not meth.callable():
return Uninferable
try:
context.callcontext = CallContext(args=[], callee=meth)
for value in meth.infer_call_result(instance, context=context):
if value is Uninferable:
return value
try:
inferred = next(value.infer(context=context))
except StopIteration as e:
raise InferenceError(context=context) from e
return inferred.bool_value()
except InferenceError:
pass
return Uninferable
def class_instance_as_index(node):
"""Get the value as an index for the given instance.
If an instance provides an __index__ method, then it can
be used in some scenarios where an integer is expected,
for instance when multiplying or subscripting a list.
"""
context = InferenceContext()
try:
for inferred in node.igetattr("__index__", context=context):
if not isinstance(inferred, bases.BoundMethod):
continue
context.boundnode = node
context.callcontext = CallContext(args=[], callee=inferred)
for result in inferred.infer_call_result(node, context=context):
if isinstance(result, nodes.Const) and isinstance(
result.value, int):
return result
except InferenceError:
pass
return None