[PATCH] D40737: [clang-tidy] Resubmit hicpp-multiway-paths-covered without breaking test

[Aaron Ballman via Phabricator via cfe-commits]

aaron.ballman accepted this revision.
aaron.ballman added a comment.
This revision is now accepted and ready to land.

LGTM!



================
Comment at: clang-tidy/hicpp/MultiwayPathsCoveredCheck.cpp:119
+  if (!SwitchHasDefault && SwitchCaseCount == 0) {
+    diag(Switch->getLocStart(), "degenerated switch without labels");
+    return;
----------------
JonasToth wrote:
> aaron.ballman wrote:
> > I think a better way to phrase this one is: "switch statement without labels has no effect" and perhaps have a fix-it to replace the entire switch construct with its predicate?
> The fixit would only aim for the sideeffects the predicate has, right? I would consider such a switch as a bug or are there reasonable things to accomplish? Given its most likely unintended code i dont think a fixit is good.
> 
> Fixing the code removes the warning and might introduce a bug.
This code pattern comes up with machine-generated code with some frequency, so I was thinking it would be nice to automatically fix that code. However, I think you're right that "fixing" the code may introduce bugs because you don't want to keep around non-side effecting operations and that's complicated. e.g.,
```
switch (i) { // Don't replace this with i;
}

switch (some_function_call()) { // Maybe replace this with some_function_call()?
}

switch (i = 12) { // Should definitely be replaced with i = 12;
}
```
Perhaps only diagnosing is the best option.


Repository:
  rCTE Clang Tools Extra

https://reviews.llvm.org/D40737