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- 6 commits
- 42 files changed
- 1 contributor
Commits on Apr 16, 2026
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Python: Add self-validating CFG tests
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.
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Python: Add some CFG-validation queries
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.
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Python: Add BasicBlockOrdering test
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.) -
Python: Add NeverReachable test
This looks for nodes annotated with `t.never` in the test that are reachable in the CFG. This should not happen (it messes with various queries, e.g. the "mixed returns" query), but the test shows that in a few particular cases (involving the `match` statement where all cases contain `return`s), we _do_ have reachable nodes that shouldn't be.
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Python: Add ConsecutiveTimestamps test
This one is potentially a bit iffy -- it checks for a very powerful propetry (that implies many of the other queries), but as the test results show, it can produce false positives when there is in fact no problem. We may want to get rid of it entirely, if it becomes too noisy.
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