[PATCH] D139705: [clang] fix zero-initialization fix-it for variable template

[Tomasz Kamiński via Phabricator via cfe-commits]

tomasz-kaminski-sonarsource added a comment.

In D139705#4216417 <https://reviews.llvm.org/D139705#4216417>, @erichkeane wrote:

> In D139705#4215653 <https://reviews.llvm.org/D139705#4215653>, @tomasz-kaminski-sonarsource wrote:
>
>> As a downstream, we have concerns with this change. From what I saw it breaks the behavior of the fix-it that wants to remove the whole variable definition (including the initializer). For example, I have unused, that I want to remove variable `x` and unnecessary explicit specialization `temp<double>`:
>>
>>   template<typename T>
>>   T temp = 1;
>>   
>>   int x  = 10;
>>   template<> double temp<double> = 1;
>>
>> Previously, this could be handled (in case of single variable declaration) by simply removing up the `var->getSourceRange()` with succeeding coma. However, after the change, such code does not work, and in general if `getSourceRange()` is used on `VarDecl` (or even `Decl`), special consideration needs to be taken for the situation when `VarDecl` refers to variable template specialization.
>>
>> As an alternative, I would suggest introducing an additional function to `VarDecl` (which could be moved up in the hierarchy), that would report a source range that corresponds to //declarator-id//, i.e. for template variable it would include template arguments.
>
> Hmm... I'm being a little dense here I guess, I don't understand what you mean?  Does this result in one of our fixits being wrong here?  With the old range, wouldn't it have left the `<double>` in that case, and now is removing it?  Or what am I missing?

Before the change, for both `x` and `temp<double>`, prior the change the `getSourceRange()` on the `VarDecl` that represents them include initializer (they end just before `;`). But now for the variable template specialization, we end up just after template arguments. This means that fixit/report that previously covered the whole definition, will now not include initializer.
Or in our example:

  `
  template<typename T>
  T temp = 1;
       // v getSourceRange() ends on this token before and after the change
  int x = 10;
                                // v getSourceRange() ends on this token prior the change, consistently with normal variables
  template<> double temp<double> = 1;
                            // ^ getSurceRange() ends on this token after the change, making it inconsistient
  `


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