[Clang] accept @tparam on variable template partial specializations (#147219)

Fixes #144775

--- 

This patch addresses a false-positive `-Wdocumentation` warning on
`@tparam` comments attached to _variable template partial
specializations_

Author: a-tarasyuk

clang/docs/ReleaseNotes.rst

@@ -675,6 +675,8 @@ Improvements to Clang's diagnostics
   false positives in exception-heavy code, though only simple patterns
   are currently recognized.
 
+- Clang now accepts ``@tparam`` comments on variable template partial
+  specializations. (#GH144775)
 
 Improvements to Clang's time-trace
 ----------------------------------

clang/lib/AST/Comment.cpp

@@ -291,6 +291,13 @@ void DeclInfo::fill() {
     TemplateParameters = CTPSD->getTemplateParameters();
     break;
   }
+  case Decl::VarTemplatePartialSpecialization: {
+    const auto *VTPSD = cast<VarTemplatePartialSpecializationDecl>(CommentDecl);
+    Kind = VariableKind;
+    TemplateKind = TemplatePartialSpecialization;
+    TemplateParameters = VTPSD->getTemplateParameters();
+    break;
+  }
   case Decl::ClassTemplateSpecialization:
     Kind = ClassKind;
     TemplateKind = TemplateSpecialization;

clang/test/Sema/warn-documentation.cpp

@@ -1524,3 +1524,15 @@ F &f = FF; ///< \return none
 // expected-warning@-1 {{'\return' command used in a comment that is not attached to a function or method declaration}}
 
 } // namespace PR42844
+
+#if __cplusplus >= 201402L
+namespace GH144775 {
+/// @brief primary template
+/// @tparam T type
+template <class T, class = void> constexpr auto var = T{};
+
+/// @brief variable template partial specialization
+/// @tparam T type
+template <typename T> constexpr auto var<T> = T{};
+} // namespace GH144775
+#endif