[PATCH] D30158: [clang-tidy] modernize: Find usage of random_shuffle and replace it with shuffle.

[Aaron Ballman via Phabricator via cfe-commits]

aaron.ballman added inline comments.


================
Comment at: clang-tidy/modernize/ReplaceRandomShuffleCheck.cpp:77
+
+  auto Diag = [=]() {
+    std::string Message = ReplaceMessage;
----------------
madsravn wrote:
> aaron.ballman wrote:
> > madsravn wrote:
> > > aaron.ballman wrote:
> > > > Is there a reason this needs to capture everything by copy? Also, no need for the empty parens. Actually, is the lambda even necessary at all?
> > > Is it OK to capture by reference then? Or how do we want it in llvm? 
> > > 
> > > We need the lambda, because first I need to create the diag with a message based on the count of arguments and then I need to find fixits based on the same count. Example: 
> > > 
> > > 
> > > ```
> > > string message = "Message for 2 arguments";
> > > if(argumentCount == 3) {
> > >   message = "Message for 3 arguments";
> > > }
> > > auto Diag = diag(startLoc(), message);
> > > if(argumentCount == 3) {
> > >   Diag << FixitHint::FixForThreeArguments();
> > > } else {
> > >   Diag << FixitHint::FixForTwoArguments();
> > > }
> > > ```
> > > 
> > > So the idea with the lambda is to avoid doing the same if-statement twice. 
> > But you call the lambda immediately rather than store it and reuse it? It seems like you should be able to hoist a `DiagnosticBuilder` variable outside of the if statement and skip the lambda entirely.
> I am not sure what you mean by this. Can you elaborate? Can you give a short example how I would hoist a `DiagnosticBuilder` out?
> 
> I think I tried something like that, but it was not an option. 
It's entirely possible I'm missing something (I'm distracted with meetings this week), but I was envisioning:
```
DiagnosticBuilder Diag;
if (MatchedCallExpr->getNumArgs() == 3) {
  Diag =
      diag(MatchedCallExpr->getLocStart(),
           "'std::random_shuffle' has been removed in C++17; use "
           "'std::shuffle' and an alternative random mechanism instead");
  Diag << FixItHint::CreateReplacement(
      MatchedArgumentThree->getSourceRange(),
      "std::mt19937(std::random_device()())");
} else {
  Diag = diag(MatchedCallExpr->getLocStart(),
                    "'std::random_shuffle' has been removed in C++17; use "
                    "'std::shuffle' instead");
  Diag << FixItHint::CreateInsertion(
      MatchedCallExpr->getRParenLoc(),
      ", std::mt19937(std::random_device()())");
}
```


https://reviews.llvm.org/D30158