This commit tweaks the interface of `CheckerRegistry::addChecker` to
make it more practical for plugins and tests:
- The parameter `IsHidden` now defaults to `false` even in the
non-templated overload (because setting it to true is unusual,
especially in plugins).
- The parameter `DocsUri` defaults to the dummy placeholder string
`"NoDocsUri"` because (as of now) nothing queries its value from the
checker registry (it's only used by the logic that generates the
clang-tidy documentation, but that loads it directly from `Checkers.td`
without involving the `CheckerRegistry`), so there is no reason to
demand specifying this value.
In addition to propagating these changes, this commit clarifies,
corrects and extends lots of comments and performs various minor code
quality improvements in the code of unit tests and example plugins.
I originally wrote the bulk of this commit when I was planning to add an
extra parameter to `addChecker` in order to implement some technical
details of the CheckerFamily framework. At the end I decided against
adding that extra parameter, so this cleanup was left out of the PR
https://github.com/llvm/llvm-project/pull/139256 and I'm merging it now
as a separate commit (after minor tweaks).
This commit is mostly NFC: the only functional change is that the
analyzer will be compatible with plugins that rely on the default
argument values and don't specify `IsHidden` or `DocsUri`. (But existing
plugin code will remain valid as well.)
In `VisitObjCForCollectionStmt`, the function does `evalLocation` for
the current element at the original source state `Pred`. The evaluation
may result in a new state, say `PredNew`. I.e., there is a transition:
`Pred -> PredNew`, though it is a very rare case that `Pred` is NOT
identical to `PredNew`. (This explains why the bug exists for many years
but no one noticed until recently a crash observed downstream.) Later,
the original code does NOT use `PredNew` as the new source state in
`StmtNodeBuilder` for next transitions. In cases `Pred != PredNew`, the
program ill behaves.
(rdar://143280254)
