This `select` clause had become very slow after we started caching
`ElementBase::toString` because the query used string concatenation to
produce alert messages, and those string concatenations were done very
early in the pipeline, producing lots of strings that would be discarded
moments later.
By using `$@` to interpolate elements into strings, the concatenation is
done outside of QL.
Testing on a Chromium snapshot, this commit takes us from
#select#ff ................ 6m2s
to
#select#cpe#134#fff ....... 15.2s
These changes should not affect semantics since these uses of
`LocalScopeVariable` were already constrained to stack variables by
their use of SSA or def-use.
This query is not producing good enough results to justify `@precision
high`. It's fundamentally looking for a pattern that should correlate
with memory management errors, but it doesn't look for the errors
themselves.
