[PATCH] D134928: [Sema] Don't treat a non-null template argument as if it were null.

[Eli Friedman via Phabricator via cfe-commits]

efriedma added inline comments.


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Comment at: clang/test/CXX/temp/temp.arg/temp.arg.nontype/p1-11.cpp:31
 IP<&tl> ip7; // expected-error{{non-type template argument of type 'int *' is not a constant expression}}
+IP<(int*)1> ip8; // expected-error {{non-type template argument does not refer to any declaration}}
 
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erichkeane wrote:
> shafik wrote:
> > shafik wrote:
> > > It looks like in C++17 mode we catch this case: https://godbolt.org/z/s43oE5qWE
> > Another case to check for:
> > 
> > ```
> > IP<(int*)(1-1)> ip9;
> > ```
> > 
> > In C++11 the wording use to allow `integer constant expressions`
> The new diagnostic here is unfortunate.  That 'does not refer to any declaration' doesn't really let me know that it is illegal because that isn't a NPE.  
> 
> The 'treat it as a null ptr' here is obviously awful, but I find myself wondering if we can do better on this diagnostic trivially enough?
It's easy enough to use a different message; we just need to detect the particular case we're considering, print an error, and return NPV_Error.  But I'm not sure what a better diagnostic looks like.   "standard C++ does not allow using '(int*)1' as a non-type template argument"?  (The fact that null is allowed isn't really relevant here.)


Repository:
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CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D134928/new/

https://reviews.llvm.org/D134928