[PATCH] D97889: [clang-tidy] Fix assert in modernize-loop-convert

[Nathan James via Phabricator via cfe-commits]

njames93 added inline comments.


================
Comment at: clang-tools-extra/clang-tidy/modernize/LoopConvertCheck.cpp:316-317
     return nullptr;
+  if (!Member->getMemberDecl()->getDeclName().isIdentifier())
+    return nullptr;
   StringRef Name = Member->getMemberDecl()->getName();
----------------
njames93 wrote:
> aaron.ballman wrote:
> > It's really strange to me that we're even getting to this point in the check -- the only way for the assertion to fail is for the member call expression to be on something without a name. The cases I can think of for that would be something like `foo.operator+(RHS)` or something similarly nonsensical within this context (we're looking for things named `begin` or `end`). I think it'd make more sense to handle this at the matcher level (or early in the call chain) so that we never get here.
> > 
> > I think having a test case would be really useful to trying to understand what changes are appropriate. I don't think these changes are wrong so much as I wonder if we're in the wrong place to make them (and we'll hit other confused code elsewhere).
> It is very strange. At the matcher level we are looking for calls to methods named `begin` or `end` or (c/r) variants. 
> I'm gonna try and put some debug prints and see if I can figure out the code actually causing the assert in the first place.
> 
> In the mean time, I have a patch in the works that moves a lot of the logic into the matchers and this whole function is removed in there, however a few creases still need to be ironed out in there.
So I put some debugprints in there and managed to find the cause of the crash
```
  // llvm/lib/Option/OptTable.cpp:150
  for (StringSet<>::const_iterator I = PrefixesUnion.begin(),
                                   E = PrefixesUnion.end(); I != E; ++I) {
    StringRef Prefix = I->getKey();
    for (StringRef::const_iterator C = Prefix.begin(), CE = Prefix.end();
                                   C != CE; ++C)
      if (!is_contained(PrefixChars, *C))
        PrefixChars.push_back(*C);
  }```
However I'm still not 100% sure of the cause of the crash. Its nothing to do with `begin()` being a member of the bast class StringMap. I tried testing with inherited begin/end methods and no crash.
My best guess is Prefix.begin() returns `StringMapIterator<>`, that class contains a conversion operator to `StringMapConstIterator<>`. Conversion operators names aren't Identifiers so that would explain the assert.
If that is the case, the actual issue is in `digThroughConstructors` being fooled by the `CXXMemberCallExpr` that's just a conversion operator.

The other patch in the works doesn't use that function so the bug is not present there, maybe its easier to just get that ready. WDYT?


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  https://reviews.llvm.org/D97889/new/

https://reviews.llvm.org/D97889