This one demonstrates a bug in the current CFG. In a dictionary
comprehension `{k: v for k, v in d.items()}`, we evaluate the value
before the key, which is incorrect. (A fix for this bug has been
implemented in a separate PR.)
These use the annotated, self-verifying test files to check various
consistency requirements.
Some of these may be expressing the same thing in different ways, but
it's fairly cheap to keep them around, so I have not attempted to
produce a minimal set of queries for this.
These tests consist of various Python constructions (hopefully a
somewhat comprehensive set) with specific timestamp annotations
scattered throughout. When the tests are run using the Python 3
interpreter, these annotations are checked and compared to the "current
timestamp" to see that they are in agreement. This is what makes the
tests "self-validating".
There are a few different kinds of annotations: the basic `t[4]` style
(meaning this is executed at timestamp 4), the `t[dead(4)]` variant
(meaning this _would_ happen at timestamp 4, but it is in a dead
branch), and `t[never]` (meaning this is never executed at all).
In addition to this, there is a query, MissingAnnotations, which checks
whether we have applied these annotations maximally. Many expression
nodes are not actually annotatable, so there is a sizeable list of
excluded nodes for that query.
