[PATCH] D55433: [clang-tidy] Adding a new modernize use nodiscard checker

[Jonas Toth via Phabricator via cfe-commits]

JonasToth added inline comments.


================
Comment at: test/clang-tidy/modernize-use-nodiscard.cpp:126
+template<class T>
+class Bar
+{
----------------
MyDeveloperDay wrote:
> curdeius wrote:
> > JonasToth wrote:
> > > I think the template tests should be improved.
> > > What happens for `T empty()`, `typename T::value_type empty()` and so on. THe same for the parameters for functions/methods (including function templates).
> > > 
> > > Thinking of it, it might be a good idea to ignore functions where the heuristic depends on the template-paramters.
> > It might be a good idea to add a note in the documentation about handling of function templates and functions in class templates.
> I think I need some help to determine if the parameter is a template parameter (specially a const T & or a const_reference)
> 
> I'm trying to remove functions which have any type of Template parameter (at least for now)
> 
> I've modified the hasNonConstReferenceOrPointerArguments matcher to use isTemplateTypeParamType()
> 
> but this doesn't seem to work though an Alias or even just with a const &
> 
> ```
>   return llvm::any_of(Node.parameters(), [](const ParmVarDecl *Par) {
>     QualType ParType = Par->getType();
> 
>     if (ParType->isTemplateTypeParmType())
>       return true;
> 
>     if (ParType->isPointerType() || isNonConstReferenceType(ParType))
>       return true;
> 
>     return false;
>   });
> ```
> 
> mostly the tests cases work for  T and T&  (see below)
> 
> but it does not seem to work for const T&, or const_reference, where it still wants to add the [[nodiscard]]
> 
> Could anyone give me any pointers, or somewhere I can look to learn?  I was thinking I needed to look at the getUnqualifiedDeSugared() but it didn't seem to work the way I expected.
> 
> ```
> template<class T>
> class Bar
> {
>     public:
>     using value_type = T;
>     using reference = value_type&;
>     using const_reference = const value_type&;
> 
>     bool empty() const;
>     // CHECK-MESSAGES: :[[@LINE-1]]:5: warning: function 'empty' should be marked NO_DISCARD [modernize-use-nodiscard]
>     // CHECK-FIXES: NO_DISCARD bool empty() const;
> 
>     // we cannot assume that the template parameter isn't a pointer
>     bool f25(value_type) const;
>     // CHECK-MESSAGES-NOT: warning:
>     // CHECK-FIXES: bool f25(value_type) const;
> 
>     bool f27(reference) const;
>     // CHECK-MESSAGES-NOT: warning:
>     // CHECK-FIXES: bool f27(reference) const
> 
>     typename T::value_type f35() const;
>     // CHECK-MESSAGES: :[[@LINE-1]]:5: warning: function 'f35' should be marked NO_DISCARD [modernize-use-nodiscard]
>     // CHECK-FIXES: NO_DISCARD typename T::value_type f35() const
> 
>     T f34() const;
>     // CHECK-MESSAGES: :[[@LINE-1]]:5: warning: function 'f34' should be marked NO_DISCARD [modernize-use-nodiscard]
>     // CHECK-FIXES: NO_DISCARD T f34() const
> 
>     bool f31(T) const;
>     // CHECK-MESSAGES-NOT: warning:
>     // CHECK-FIXES: bool f31(T) const
> 
>     bool f33(T&) const;
>     // CHECK-MESSAGES-NOT: warning:
>     // CHECK-FIXES: bool f33(T&) const
> 
>     // -------------  FIXME TESTS BELOW FAIL ------------- //
>     bool f26(const_reference) const;
>     // CHECK-MESSAGES-NOT: warning:
>     // CHECK-FIXES: bool f26(const_reference) const;
> 
>     bool f32(const T&) const;
>     // CHECK-MESSAGES-NOT: warning:
>     // CHECK-FIXES: bool f32(const T&) const
> };
> 
> ```
> 
> 
> 
> 
> 
> 
Is this resolved, as you marked it done?


CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D55433/new/

https://reviews.llvm.org/D55433