[clangd] Use canonical declarations in ReferenceFinder.

[hokein]

Summary

handleDeclOccurrencce reports a canonical declartion, so stick to use
canonical declarations to determine whether a declaration is in the
target set.

Also fix a previous ref test which misses a matched label (it fails without this
patch).

[sammccall]

Nice catch!

unittests/clangd/XRefsTests.cpp

1185

hmm, it looks like the "foo" labels on the ranges don't need to be there, and they hurt readability.

Want to remove them from all the tests, rather than add them to the method call test where they're missing?

[hokein]

Remove unnecessary labels.

clangd/XRefs.cpp

 }
 
 namespace {
 
 /// Collects references to symbols within the main file.
 class ReferenceFinder : public index::IndexDataConsumer {
 public:
   struct Reference {
-    const Decl *Target;
+    const Decl *CanonicalTarget;
     SourceLocation Loc;
     index::SymbolRoleSet Role;
   };
 
   ReferenceFinder(ASTContext &AST, Preprocessor &PP,
                   const std::vector<const Decl *> &TargetDecls)
       : AST(AST) {
     for (const Decl *D : TargetDecls)
-      Targets.insert(D);
+      CanonicalTargets.insert(D->getCanonicalDecl());
   }
 
   std::vector<Reference> take() && {
     std::sort(References.begin(), References.end(),
               [](const Reference &L, const Reference &R) {
-                return std::tie(L.Loc, L.Target, L.Role) <
-                       std::tie(R.Loc, R.Target, R.Role);
+                return std::tie(L.Loc, L.CanonicalTarget, L.Role) <
+                       std::tie(R.Loc, R.CanonicalTarget, R.Role);
               });
     // We sometimes see duplicates when parts of the AST get traversed twice.
-    References.erase(std::unique(References.begin(), References.end(),
-                                 [](const Reference &L, const Reference &R) {
-                                   return std::tie(L.Target, L.Loc, L.Role) ==
-                                          std::tie(R.Target, R.Loc, R.Role);
-                                 }),
-                     References.end());
+    References.erase(
+        std::unique(References.begin(), References.end(),
+                      return std::tie(L.CanonicalTarget, L.Loc, L.Role) ==
+                             std::tie(R.CanonicalTarget, R.Loc, R.Role);
     return std::move(References);
   }
 
   bool
   handleDeclOccurence(const Decl *D, index::SymbolRoleSet Roles,
                       ArrayRef<index::SymbolRelation> Relations,
                       SourceLocation Loc,
                       index::IndexDataConsumer::ASTNodeInfo ASTNode) override {
+    assert(D->isCanonicalDecl() && "expect D to be a canonical declaration");
     const SourceManager &SM = AST.getSourceManager();
     Loc = SM.getFileLoc(Loc);
-    if (SM.isWrittenInMainFile(Loc) && Targets.count(D))
+    if (SM.isWrittenInMainFile(Loc) && CanonicalTargets.count(D))
       References.push_back({D, Loc, Roles});
     return true;
   }
 
 private:
-  llvm::SmallSet<const Decl *, 4> Targets;
+  llvm::SmallSet<const Decl *, 4> CanonicalTargets;
   std::vector<Reference> References;
   const ASTContext &AST;
 };
 
 std::vector<ReferenceFinder::Reference>
 findRefs(const std::vector<const Decl *> &Decls, ParsedAST &AST) {
   ReferenceFinder RefFinder(AST.getASTContext(), AST.getPreprocessor(), Decls);
   index::IndexingOptions IndexOpts;

unittests/clangd/XRefsTests.cpp

EXPECT_THAT(
       cantFail(runFindDefinitions(Server, FooCpp, FooWithoutHeader.point())),
       ElementsAre(Location{FooCppUri, FooWithoutHeader.range()}));
 }
 
 TEST(FindReferences, WithinAST) {
   const char *Tests[] = {
       R"cpp(// Local variable
         int main() {
-          int $foo[[foo]];
-          $foo[[^foo]] = 2;
-          int test1 = $foo[[foo]];
+          int [[foo]];
+          [[^foo]] = 2;
+          int test1 = [[foo]];
         }
       )cpp",
 
       R"cpp(// Struct
         namespace ns1 {
-        struct $foo[[Foo]] {};
+        struct [[Foo]] {};
         } // namespace ns1
         int main() {
-          ns1::$foo[[Fo^o]]* Params;
+          ns1::[[Fo^o]]* Params;
+        }
+      )cpp",
+
+      R"cpp(// Forward declaration
+        class [[Foo]];
+        class [[Foo]] {}
+        int main() {
+          [[Fo^o]] foo;
         }
       )cpp",
 
       R"cpp(// Function
-        int $foo[[foo]](int) {}
+        int [[foo]](int) {}
         int main() {
-          auto *X = &$foo[[^foo]];
-          $foo[[foo]](42)
+          auto *X = &[[^foo]];
+          [[foo]](42)
         }
       )cpp",
 
       R"cpp(// Field
         struct Foo {
-          int $foo[[foo]];
-          Foo() : $foo[[foo]](0) {}
+          int [[foo]];
+          Foo() : [[foo]](0) {}
         };
         int main() {
           Foo f;
-          f.$foo[[f^oo]] = 1;
+          f.[[f^oo]] = 1;
         }
       )cpp",
 
       R"cpp(// Method call
         struct Foo { int [[foo]](); };
         int Foo::[[foo]]() {}
         int main() {
           Foo f;
-          f.^foo();
+          f.[[^foo]]();
         }
       )cpp",
 
       R"cpp(// Typedef
-        typedef int $foo[[Foo]];
+        typedef int [[Foo]];
         int main() {
-          $foo[[^Foo]] bar;
+          [[^Foo]] bar;
         }
       )cpp",
 
       R"cpp(// Namespace
-        namespace $foo[[ns]] {
+        namespace [[ns]] {
         struct Foo {};
         } // namespace ns
-        int main() { $foo[[^ns]]::Foo foo; }
+        int main() { [[^ns]]::Foo foo; }
       )cpp",
   };
   for (const char *Test : Tests) {
     Annotations T(Test);
     auto AST = TestTU::withCode(T.code()).build();
     std::vector<Matcher<Location>> ExpectedLocations;
-    for (const auto &R : T.ranges("foo"))
+    for (const auto &R : T.ranges())
       ExpectedLocations.push_back(RangeIs(R));
     EXPECT_THAT(findReferences(AST, T.point()),
                 ElementsAreArray(ExpectedLocations))
         << Test;
   }
 }
 
 TEST(FindReferences, NeedsIndex) {