[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 : public ConstStmtVisitor<Visitor> {
                 llvm::dyn_cast<UsingShadowDecl>(ME->getFoundDecl().getDecl()))
           D = USD;
         Outer.add(D, Flags);
       }
       void VisitOverloadExpr(const OverloadExpr *OE) {
         for (auto *D : OE->decls())
           Outer.add(D, Flags);
       }
+      void VisitSizeOfPackExpr(const SizeOfPackExpr *SE) {
+        Outer.add(SE->getPack(), Flags);
+      }
       void VisitCXXConstructExpr(const CXXConstructExpr *CCE) {
         Outer.add(CCE->getConstructor(), Flags);
       }
       void VisitDesignatedInitExpr(const DesignatedInitExpr *DIE) {
         for (const DesignatedInitExpr::Designator &D :
              llvm::reverse(DIE->designators()))
           if (D.isFieldDesignator()) {
             Outer.add(D.getField(), Flags);
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/FindTargetTests.cpp

TEST_F(TargetDeclTest, Types) {
   EXPECT_DECLS("DecltypeTypeLoc", {"struct S", Rel::Underlying});
 
   Code = R"cpp(
     struct S{};
     [[auto]] X = S{};
   )cpp";
   // FIXME: deduced type missing in AST. https://llvm.org/PR42914
   EXPECT_DECLS("AutoTypeLoc");
+
+  Code = R"cpp(
+    template <typename... E>
+    struct S {
+      static const int size = sizeof...([[E]]);
+    };
+  )cpp";
+  // FIXME: We don't do a good job printing TemplateTypeParmDecls, apparently!
+  EXPECT_DECLS("SizeOfPackExpr", "");
 }
 
 TEST_F(TargetDeclTest, ClassTemplate) {
   Code = R"cpp(
     // Implicit specialization.
     template<int x> class Foo{};
     [[Foo<42>]] B;
   )cpp";
for (unsigned I = 0; I < Refs.size(); ++I)
       DumpedReferences += llvm::formatv("{0}: {1}\n", I, Refs[I]);
 
     return AllRefs{std::move(AnnotatedCode), std::move(DumpedReferences)};
   }
 };
 
 TEST_F(FindExplicitReferencesTest, All) {
   std::pair</*Code*/ llvm::StringRef, /*References*/ llvm::StringRef> Cases[] =
-      {
-          // Simple expressions.
-          {R"cpp(
+      {// Simple expressions.
         int global;
         int func();
         void foo(int param) {
           $0^global = $1^param + $2^func();
         }
         )cpp",
-           "0: targets = {global}\n"
-           "1: targets = {param}\n"
-           "2: targets = {func}\n"},
-          {R"cpp(
         struct X { int a; };
         void foo(X x) {
           $0^x.$1^a = 10;
         }
         )cpp",
-           "0: targets = {x}\n"
-           "1: targets = {X::a}\n"},
-          // Namespaces and aliases.
-          {R"cpp(
           namespace ns {}
           namespace alias = ns;
           void foo() {
             using namespace $0^ns;
             using namespace $1^alias;
           }
         )cpp",
-           "0: targets = {ns}\n"
-           "1: targets = {alias}\n"},
-          // Using declarations.
-          {R"cpp(
           namespace ns { int global; }
           void foo() {
             using $0^ns::$1^global;
           }
         )cpp",
-           "0: targets = {ns}\n"
-           "1: targets = {ns::global}, qualifier = 'ns::'\n"},
-          // Simple types.
-          {R"cpp(
          struct Struct { int a; };
          using Typedef = int;
          void foo() {
            $0^Struct $1^x;
            $2^Typedef $3^y;
            static_cast<$4^Struct*>(0);
          }
        )cpp",
-           "0: targets = {Struct}\n"
-           "1: targets = {x}, decl\n"
-           "2: targets = {Typedef}\n"
-           "3: targets = {y}, decl\n"
-           "4: targets = {Struct}\n"},
-          // Name qualifiers.
-          {R"cpp(
          namespace a { namespace b { struct S { typedef int type; }; } }
          void foo() {
            $0^a::$1^b::$2^S $3^x;
            using namespace $4^a::$5^b;
            $6^S::$7^type $8^y;
          }
         )cpp",
-           "0: targets = {a}\n"
-           "1: targets = {a::b}, qualifier = 'a::'\n"
-           "2: targets = {a::b::S}, qualifier = 'a::b::'\n"
-           "3: targets = {x}, decl\n"
-           "4: targets = {a}\n"
-           "5: targets = {a::b}, qualifier = 'a::'\n"
-           "6: targets = {a::b::S}\n"
-           "7: targets = {a::b::S::type}, qualifier = 'struct S::'\n"
-           "8: targets = {y}, decl\n"},
-          // Simple templates.
-          {R"cpp(
           template <class T> struct vector { using value_type = T; };
           template <> struct vector<bool> { using value_type = bool; };
           void foo() {
             $0^vector<int> $1^vi;
             $2^vector<bool> $3^vb;
           }
         )cpp",
-           "0: targets = {vector<int>}\n"
-           "1: targets = {vi}, decl\n"
-           "2: targets = {vector<bool>}\n"
-           "3: targets = {vb}, decl\n"},
-          // Template type aliases.
-          {R"cpp(
             template <class T> struct vector { using value_type = T; };
             template <> struct vector<bool> { using value_type = bool; };
             template <class T> using valias = vector<T>;
             void foo() {
               $0^valias<int> $1^vi;
               $2^valias<bool> $3^vb;
             }
           )cpp",
-           "0: targets = {valias}\n"
-           "1: targets = {vi}, decl\n"
-           "2: targets = {valias}\n"
-           "3: targets = {vb}, decl\n"},
-          // MemberExpr should know their using declaration.
-          {R"cpp(
             struct X { void func(int); }
             struct Y : X {
               using X::func;
             };
             void foo(Y y) {
               $0^y.$1^func(1);
             }
         )cpp",
-           "0: targets = {y}\n"
-           "1: targets = {Y::func}\n"},
-          // DeclRefExpr should know their using declaration.
-          {R"cpp(
             namespace ns { void bar(int); }
             using ns::bar;
 
             void foo() {
               $0^bar(10);
             }
         )cpp",
-           "0: targets = {bar}\n"},
-          // References from a macro.
-          {R"cpp(
             #define FOO a
             #define BAR b
 
             void foo(int a, int b) {
               $0^FOO+$1^BAR;
             }
         )cpp",
-           "0: targets = {a}\n"
-           "1: targets = {b}\n"},
-          // No references from implicit nodes.
-          {R"cpp(
             struct vector {
               int *begin();
               int *end();
             };
 
             void foo() {
               for (int $0^x : $1^vector()) {
                 $2^x = 10;
               }
             }
         )cpp",
-           "0: targets = {x}, decl\n"
-           "1: targets = {vector}\n"
-           "2: targets = {x}\n"},
-          // Handle UnresolvedLookupExpr.
-          {R"cpp(
             namespace ns1 { void func(char*); }
             namespace ns2 { void func(int*); }
             using namespace ns1;
             using namespace ns2;
 
             template <class T>
             void foo(T t) {
               $0^func($1^t);
             }
         )cpp",
-           "0: targets = {ns1::func, ns2::func}\n"
-           "1: targets = {t}\n"},
-          // Handle UnresolvedMemberExpr.
-          {R"cpp(
             struct X {
               void func(char*);
               void func(int*);
             };
 
             template <class T>
             void foo(X x, T t) {
               $0^x.$1^func($2^t);
             }
         )cpp",
-           "0: targets = {x}\n"
-           "1: targets = {X::func, X::func}\n"
-           "2: targets = {t}\n"},
-          // Type template parameters.
-          {R"cpp(
             template <class T>
             void foo() {
               static_cast<$0^T>(0);
               $1^T();
               $2^T $3^t;
             }
         )cpp",
-           "0: targets = {T}\n"
-           "1: targets = {T}\n"
-           "2: targets = {T}\n"
-           "3: targets = {t}, decl\n"},
-          // Non-type template parameters.
-          {R"cpp(
             template <int I>
             void foo() {
               int $0^x = $1^I;
             }
         )cpp",
-           "0: targets = {x}, decl\n"
-           "1: targets = {I}\n"},
-          // Template template parameters.
-          {R"cpp(
             template <class T> struct vector {};
 
             template <template<class> class TT, template<class> class ...TP>
             void foo() {
               $0^TT<int> $1^x;
               $2^foo<$3^TT>();
               $4^foo<$5^vector>()
               $6^foo<$7^TP...>();
             }
         )cpp",
-           "0: targets = {TT}\n"
-           "1: targets = {x}, decl\n"
-           "2: targets = {foo}\n"
-           "3: targets = {TT}\n"
-           "4: targets = {foo}\n"
-           "5: targets = {vector}\n"
-           "6: targets = {foo}\n"
-           "7: targets = {TP}\n"},
-          // Non-type template parameters with declarations.
-          {R"cpp(
             int func();
             template <int(*)()> struct wrapper {};
 
             template <int(*FuncParam)()>
             void foo() {
               $0^wrapper<$1^func> $2^w;
               $3^FuncParam();
             }
         )cpp",
-           "0: targets = {wrapper<&func>}\n"
-           "1: targets = {func}\n"
-           "2: targets = {w}, decl\n"
-           "3: targets = {FuncParam}\n"},
-          // declaration references.
-          {R"cpp(
              namespace ns {}
              class S {};
              void foo() {
                class $0^Foo { $1^Foo(); ~$2^Foo(); int $3^field; };
                int $4^Var;
                enum $5^E { $6^ABC };
                typedef int $7^INT;
                using $8^INT2 = int;
                namespace $9^NS = $10^ns;
              }
            )cpp",
-           "0: targets = {Foo}, decl\n"
-           "1: targets = {foo()::Foo::Foo}, decl\n"
-           "2: targets = {Foo}\n"
-           "3: targets = {foo()::Foo::field}, decl\n"
-           "4: targets = {Var}, decl\n"
-           "5: targets = {E}, decl\n"
-           "6: targets = {foo()::ABC}, decl\n"
-           "7: targets = {INT}, decl\n"
-           "8: targets = {INT2}, decl\n"
-           "9: targets = {NS}, decl\n"
-           "10: targets = {ns}\n"},
-          // cxx constructor initializer.
-          {R"cpp(
              class Base {};
              void foo() {
                // member initializer
                class $0^X {
                  int $1^abc;
                  $2^X(): $3^abc() {}
                };
                // base initializer
                class $4^Derived : public $5^Base {
                  $6^Base $7^B;
                  $8^Derived() : $9^Base() {}
                };
                // delegating initializer
                class $10^Foo {
                  $11^Foo(int);
                  $12^Foo(): $13^Foo(111) {}
                };
              }
            )cpp",
-           "0: targets = {X}, decl\n"
-           "1: targets = {foo()::X::abc}, decl\n"
-           "2: targets = {foo()::X::X}, decl\n"
-           "3: targets = {foo()::X::abc}\n"
-           "4: targets = {Derived}, decl\n"
-           "5: targets = {Base}\n"
-           "6: targets = {Base}\n"
-           "7: targets = {foo()::Derived::B}, decl\n"
-           "8: targets = {foo()::Derived::Derived}, decl\n"
-           "9: targets = {Base}\n"
-           "10: targets = {Foo}, decl\n"
-           "11: targets = {foo()::Foo::Foo}, decl\n"
-           "12: targets = {foo()::Foo::Foo}, decl\n"
-           "13: targets = {Foo}\n"},
-          // Anonymous entities should not be reported.
-          {
-              R"cpp(
              void foo() {
               class {} $0^x;
               int (*$1^fptr)(int $2^a, int) = nullptr;
              }
            )cpp",
-              "0: targets = {x}, decl\n"
-              "1: targets = {fptr}, decl\n"
-              "2: targets = {a}, decl\n"},
-          // Namespace aliases should be handled properly.
-          {
-              R"cpp(
                 namespace ns { struct Type {} }
                 namespace alias = ns;
                 namespace rec_alias = alias;
 
                 void foo() {
                   $0^ns::$1^Type $2^a;
                   $3^alias::$4^Type $5^b;
                   $6^rec_alias::$7^Type $8^c;
                 }
            )cpp",
-              "0: targets = {ns}\n"
-              "1: targets = {ns::Type}, qualifier = 'ns::'\n"
-              "2: targets = {a}, decl\n"
-              "3: targets = {alias}\n"
-              "4: targets = {ns::Type}, qualifier = 'alias::'\n"
-              "5: targets = {b}, decl\n"
-              "6: targets = {rec_alias}\n"
-              "7: targets = {ns::Type}, qualifier = 'rec_alias::'\n"
-              "8: targets = {c}, decl\n"},
+       // Handle SizeOfPackExpr.
+       {
+           R"cpp(
+                template <typename... E>
+                void foo() {
+                  constexpr int $0^size = sizeof...($1^E);
                 };
+            )cpp",
+           "0: targets = {size}, decl\n"
+           "1: targets = {E}\n"}};
 
   for (const auto &C : Cases) {
     llvm::StringRef ExpectedCode = C.first;
     llvm::StringRef ExpectedRefs = C.second;
 
     auto Actual =
         annotateReferencesInFoo(llvm::Annotations(ExpectedCode).code());
     EXPECT_EQ(ExpectedCode, Actual.AnnotatedCode);
     EXPECT_EQ(ExpectedRefs, Actual.DumpedReferences) << ExpectedCode;
   }
 }
 
 } // namespace
 } // namespace clangd
 } // namespace clang

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"