[clangd] Find reference to template parameter in 'sizeof...' expression

[nridge]

Fixes https://github.com/clangd/clangd/issues/213

[ilya-biryukov]

Thanks! Could you also handle this in targetDecl and add the corresponding test?

[nridge]

Address review comment

[ilya-biryukov]

Could you add another test for findExplicitReferences too? Those tests are right after targetDecl.
These two functions kinda duplicate each other a lot, but that's intentional - those two functions do a somewhat similar thing and we want to keep them in sync (put another way, we want to fix bugs in both simultaneously)

[nridge]

Add FindExplicitReferences test

[ilya-biryukov]

LGTM! Many thanks!

clang-tools-extra/clangd/FindTarget.cpp

struct Visitor : ConstStmtVisitor<Visitor> {
 
     void VisitOverloadExpr(const OverloadExpr *E) {
       Refs.push_back(ReferenceLoc{E->getQualifierLoc(),
                                   E->getNameInfo().getLoc(),
                                   /*IsDecl=*/false,
                                   llvm::SmallVector<const NamedDecl *, 1>(
                                       E->decls().begin(), E->decls().end())});
     }
+
+    void VisitSizeOfPackExpr(const SizeOfPackExpr *E) {
+      Refs.push_back(ReferenceLoc{NestedNameSpecifierLoc(),
+                                  E->getPackLoc(),
+                                  /*IsDecl=*/false,
+                                  {E->getPack()}});
+    }
   };
 
   Visitor V;
   V.Visit(E);
   return V.Refs;
 }
 
 llvm::SmallVector<ReferenceLoc, 2> refInTypeLoc(TypeLoc L) {

clang-tools-extra/clangd/unittests/SemanticHighlightingTests.cpp

$InactiveCode[[]]      #endif
       int $Variable[[Active1]];
       #endif
 
 $InactiveCode[[]]      #ifdef $Macro[[test]]
 $InactiveCode[[]]      int Inactive3;
 $InactiveCode[[]]      #else
       int $Variable[[Active2]];
       #endif
+    )cpp",
+      // Argument to 'sizeof...'
+      R"cpp(
+      template <typename... $TemplateParameter[[Elements]]>
+      struct $Class[[TupleSize]] {
+        static const int $StaticField[[size]] = sizeof...($TemplateParameter[[Elements]]);
+      };
     )cpp"};
   for (const auto &TestCase : TestCases) {
     checkHighlightings(TestCase);
   }
 
   checkHighlightings(R"cpp(
     class $Class[[A]] {
       #include "imp.h"