[PATCH] D66847: [analyzer] Fix analyzer warnings.

[Artem Dergachev via Phabricator via cfe-commits]

NoQ added a comment.

In D66847#1648209 <https://reviews.llvm.org/D66847#1648209>, @Szelethus wrote:

>   if (isa<FunctionDecl>(D)) {
>     const auto *FD = dyn_cast<FunctionDecl>(D); // warn: D is known to be a FunctionDecl, prefer using cast<>
>     // ...
>   }
>




In D66847#1648339 <https://reviews.llvm.org/D66847#1648339>, @Szelethus wrote:

>   if (A) {
>     const auto *B = dyn_cast_or_null<FunctionDecl>(A); // warn: A is known to be non-null, prefer dyn_cast
>   }
>


Both of these are must-problems. They are hard to solve via symbolic execution because all execution paths need to be taken into account simultaneously. Eg.:

  if (isa<FunctionDecl>(D)) {
    if (coin)
      D = getDecl(); // Maybe not a FunctionDecl.
  
    // It's not enough to know that D is a FunctionDecl assuming coin is false.
    const auto *FD = dyn_cast<FunctionDecl>(D); // no-warning:
  }

We could maybe make a syntactic checker or a data flow checker to find these anti-patterns. @Charusso also had an idea for a clang-tidy checker that emits fixits for code like `dyn_cast<T>(x)->foo()` ("use 'cast' instead").


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https://reviews.llvm.org/D66847