[Clang] Diagnose invalid member variable with template parameters

[cor3ntin]

Summary

Fixes https://github.com/llvm/llvm-project/issues/54151

[cor3ntin]

Fix Formatting.

[aaron.ballman]

Thanks for looking into this, that's a rather amusing bug.

clang/lib/Sema/SemaDeclCXX.cpp

3398–3399

No need to look at isInstField, it's already tested above on line 3365.

clang/test/SemaCXX/class.cpp

219 ↗

(On Diff #412654)

Can you also add test cases for:

static int k<12>;
void f<12>();

To make sure we diagnose it the same way, both in a non-template class and within a templated class.

[cor3ntin]

• Fix redundant check
• move test to p17.cpp which seems more approriate
• add a couple of tests

[erichkeane]

Do we have a test somewhere to check the variable template specialization case to make sure that didn't break? Otherwise LGTM.

[cor3ntin]

In D120881#3357015, @erichkeane wrote:

Do we have a test somewhere to check the variable template specialization case to make sure that didn't break? Otherwise LGTM.

Thanks for the review.
It seems fairly well covered in clang/test/SemaCXX/cxx1y-variable-templates_in_class.cpp

[aaron.ballman]

LGTM (I'm a bit sad about the diagnostic differences, but I understand why they're different a bit better now, so this is fine.)

clang/include/clang/Basic/DiagnosticSemaKinds.td

 def ext_variable_template : ExtWarn<"variable templates are a C++14 extension">,
   InGroup<CXX14>;
 def warn_cxx11_compat_variable_template : Warning<
   "variable templates are incompatible with C++ standards before C++14">,
   InGroup<CXXPre14Compat>, DefaultIgnore;
 def err_template_variable_noparams : Error<
   "extraneous 'template<>' in declaration of variable %0">;
 def err_template_member : Error<"member %0 declared as a template">;
+def err_member_with_template_arguments : Error<"member %0 cannot have template arguments">;
 def err_template_member_noparams : Error<
   "extraneous 'template<>' in declaration of member %0">;
 def err_template_tag_noparams : Error<
   "extraneous 'template<>' in declaration of %0 %1">;
 
 def warn_cxx17_compat_adl_only_template_id : Warning<
   "use of function template name with no prior function template "
   "declaration in function call with explicit template arguments "

clang/lib/Sema/SemaDeclCXX.cpp

if (TemplateParameterLists.size()) {
             diag::err_template_member_noparams)
             << II
             << SourceRange(TemplateParams->getTemplateLoc(),
                 TemplateParams->getRAngleLoc());
       }
       return nullptr;
     }
 
+    if (D.getName().getKind() == UnqualifiedIdKind::IK_TemplateId) {
+      Diag(D.getIdentifierLoc(), diag::err_member_with_template_arguments)
+          << II
+          << SourceRange(D.getName().TemplateId->LAngleLoc,
+                         D.getName().TemplateId->RAngleLoc)
+          << D.getName().TemplateId->LAngleLoc;
+    }
+
     if (SS.isSet() && !SS.isInvalid()) {
       // The user provided a superfluous scope specifier inside a class
       // definition:
       //
       // class X {
       //   int X::member;
       // };
       if (DeclContext *DC = computeDeclContext(SS, false))

clang/test/CXX/temp/temp.spec/temp.expl.spec/p17.cpp

public:
     static int foo;
     static int bar;    
   };
 
   typedef A<double> AB;
   template <> int AB::foo = 0; // expected-error{{extraneous 'template<>'}}
   int AB::bar = 1;
 }
+
+namespace GH54151 {
+
+struct S {
+  int i<0>;   // expected-error  {{member 'i' cannot have template arguments}}
+  int j<int>; // expected-error  {{member 'j' cannot have template arguments}}
+
+  static int k<12>; // expected-error {{template specialization requires 'template<>'}} \
+                       expected-error{{no variable template matches specialization}}
+  void f<12>();     // expected-error {{template specialization requires 'template<>'}} \
+                    // expected-error {{no function template matches function template specialization 'f'}}
+};
+
+template <typename T, int N>
+struct U {
+  int i<N>; // expected-error {{member 'i' cannot have template arguments}}
+  int j<T>; // expected-error {{member 'j' cannot have template arguments}}
+};
+
+} // namespace GH54151