If options.check_variable_types is set, the following code should fail:

    a: List[int] = []
    a.append("hello")

Also adds some test cases in bugs/mutation.py for TODOs.

PiperOrigin-RevId: 314239043

…den.

Exceptions (treated as ambiguous) are:
- booleans
- numeric types
- classes overriding __bool__ (__nonzero__ in python2)
- classes overriding __len__

Provably empty builtin containers continue to be treated as False.

PiperOrigin-RevId: 314390311

New output format example:

File "third_party/py/pytype/bugs/mutation.py", line 19, in <module>: New container type does not match type annotation [container-type-mismatch]
  Annotation: Dict[str, str] (type parameters Dict[_K, _V])
  Contained types:
    _K: str
    _V: str
  New contained types:
    _K: Union[int, str]
    _V: Union[float, str]

PiperOrigin-RevId: 314422487

Adds a new option, --check-attribute-types, that will make pytype type-check
attribute assignments against annotations, e.g.,

class Foo:
  x: int
  def foo(self):
    self.x = 'hello, world'  # annotation-type-mismatch

I've left a couple of features for future CLs:
* Making annotations take precedence over instance attribute values when
  generating pyi files.
* Handling attribute type comments in __new__ and __init__.

Also puts container mutation checking behind its own flag,
--check-container-types, rather than reusing --check-variable-types. Having
this many flags is rather ugly and redundant, but they'll go away as we release
various things, and they make the release process a bit easier.

PiperOrigin-RevId: 314483072

A corner case where an alias can point to two separate annotated args via
different code paths has been left as a TODO

PiperOrigin-RevId: 314763912

Used in error messages when reporting container type annotation mismatches.

PiperOrigin-RevId: 314791344

Showed up when attempting to analyze
//apps/intelligence/cody/tools/codylab:testit.

PiperOrigin-RevId: 314814112

PiperOrigin-RevId: 315326106

…biguous.

Allows for the fact that __new__ might be called from a subclass of Foo, and
that checking that we are not in the base class is a common idiom.

PiperOrigin-RevId: 315538618

…aph.

PiperOrigin-RevId: 315564137

import is a keyword and therefore is not a valid module name in Python.

PiperOrigin-RevId: 315965683

PiperOrigin-RevId: 315968839

Prior to this change _get_match_location produced false-positive match
when the name being matched occurred as a prefix of some other imported
name, e.g.

  import foo as f

PiperOrigin-RevId: 316128150

PiperOrigin-RevId: 316139475

With this change,
  v: int = 0
  v = ''
will also be an error. I already cleaned up all new findings introduced by this
change as of about a week ago.

PiperOrigin-RevId: 316170169

For python/typeshed#4224.

We really need a better pyi parser...

PiperOrigin-RevId: 316171517