Moves the existing points-to predicates to the newly added class
`ControlFlowNodeWithPointsTo` which resides in the `LegacyPointsTo`
module.
(Existing code that uses these predicates should import this module, and
references to `ControlFlowNode` should be changed to
`ControlFlowNodeWithPointsTo`.)
Also updates all existing points-to based code to do just this.
Excluded for now: unnecassary-delete; since the pattern is often intentional to break reference cycles, which the query doesn't account for; so uncertain about its claim of high precision
Fixes the false positive reported in
https://github.com/github/codeql/issues/18910
Adds a new `Annotation` class (subclass of `Expr`) which encompasses all
possible kinds of annotations in Python.
Using this, we look for string literals which are part of an annotation,
and which have the same content as the name of a (potentially) unused
global variable, and in that case we do not produce an alert.
In future, we may want to support inspecting such string literals more
deeply (e.g. to support stuff like "list[unused_var]"), but I think for
now this level of support is sufficient.
This is only a temporary fix, as indicated by the TODO comment.
The real underlying issue is the fact that `isUnused` is defined in
terms of the underlying SSA variables (as these are only created
for variables that are actually used), and the fact that annotated
assignments are always considered to redefine their targets, which may
not actually be the case.
Thus, the correct fix would be to change the extractor to _disregard_
mere type annotations for the purposes of figuring out whether an
SSA variable should be created or not.
However, in the short term the present fix is likely sufficient.
Original code:
exists(Expr e, For forloop | forloop = loop and e.pointsTo(_, _, capturing) |
not loop.contains(e)
)
The new version will preserve the same semantics. The problem with the first
rewrite was that `not loop.(For).somethingMore` would hold for any AstNode that
was not a For
