[clangd] Added highlighting for the targets in typedefs.

[jvikstrom]

Summary

In typedef int A the A was not highlighted previously.

This patch gives A the same kind of highlighting that the underlying type has (class/enum) (which in this example is no special highlighting because builtins are not handled yet)
Will add highlightings for built ins in another patch.

[hokein]

clang-tools-extra/clangd/SemanticHighlighting.cpp

88

Do we plan to support the type alias using Y = X; as well? TypedefNameDecl should cover both cases.

[jvikstrom]

Add support for using A = ....

clang-tools-extra/clangd/SemanticHighlighting.cpp

if (Ref->getNameInfo().getName().getNameKind() !=
         DeclarationName::Identifier)
       // Only want to highlight identifiers.
       return true;
 
     addToken(Ref->getLocation(), Ref->getDecl());
     return true;
   }
 
+  bool VisitTypedefDecl(TypedefDecl *TD) {
+    if(const auto *TSI = TD->getTypeSourceInfo())
+      addTypeLoc(TD->getLocation(), TSI->getTypeLoc());
+    return true;
+  }
+
   bool VisitTypeLoc(TypeLoc &TL) {
     // This check is for not getting two entries when there are anonymous
     // structs. It also makes us not highlight certain namespace qualifiers
     // twice. For elaborated types the actual type is highlighted as an inner
     // TypeLoc.
     if (TL.getTypeLocClass() == TypeLoc::TypeLocClass::Elaborated)
       return true;
 
-    if (const Type *TP = TL.getTypePtr())
-      if (const TagDecl *TD = TP->getAsTagDecl())
-        addToken(TL.getBeginLoc(), TD);
+    addTypeLoc(TL.getBeginLoc(), TL);
     return true;
   }
 
   bool TraverseNestedNameSpecifierLoc(NestedNameSpecifierLoc NNSLoc) {
     if (NestedNameSpecifier *NNS = NNSLoc.getNestedNameSpecifier())
       if (NNS->getKind() == NestedNameSpecifier::Namespace ||
           NNS->getKind() == NestedNameSpecifier::NamespaceAlias)
         addToken(NNSLoc.getLocalBeginLoc(), HighlightingKind::Namespace);
 
     return RecursiveASTVisitor<
         HighlightingTokenCollector>::TraverseNestedNameSpecifierLoc(NNSLoc);
   }
 
 private:
+  void addTypeLoc(SourceLocation Loc, const TypeLoc &TL) {
+    if (const Type *TP = TL.getTypePtr())
+      if (const TagDecl *TD = TP->getAsTagDecl())
+        addToken(Loc, TD);
+  }
+
   void addToken(SourceLocation Loc, const NamedDecl *D) {
     if (D->getDeclName().isIdentifier() && D->getName().empty())
       // Don't add symbols that don't have any length.
       return;
     // We highlight class decls, constructor decls and destructor decls as
     // `Class` type. The destructor decls are handled in `VisitTypeLoc` (we will
     // visit a TypeLoc where the underlying Type is a CXXRecordDecl).
     if (isa<RecordDecl>(D)) {

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

R"cpp(
           T $Field[[t]];
         };
       }
       template<typename T>
       struct $Class[[C]] : $Namespace[[abc]]::A<T> {
         typename T::A* $Field[[D]];
       };
       $Namespace[[abc]]::$Class[[A]]<int> $Variable[[AA]];
-      typedef $Namespace[[abc]]::$Class[[A]]<int> AAA;
+      typedef $Namespace[[abc]]::$Class[[A]]<int> $Class[[AAA]];
       struct $Class[[B]] {
         $Class[[B]]();
         ~$Class[[B]]();
         void operator<<($Class[[B]]);
         $Class[[AAA]] $Field[[AA]];
       };
       $Class[[B]]::$Class[[B]]() {}
       $Class[[B]]::~$Class[[B]]() {}
R"cpp(
       };
       void $Function[[foo]]() {
         $Class[[A]] $Variable[[AA]];
         $Variable[[AA]].$Field[[B]] += 2;
         $Variable[[AA]].$Method[[foo]]();
         $Variable[[AA]].$Field[[E]].$Field[[C]];
         $Class[[A]]::$Variable[[S]] = 90;
       }
+    )cpp",
+    R"cpp(
+      namespace $Namespace[[a]] {
+        struct $Class[[A]] {};
+      }
+      typedef $Namespace[[a]]::$Class[[A]] $Class[[B]];
+      enum class $Enum[[E]] {};
+      typedef $Enum[[E]] $Enum[[C]];
+      typedef $Enum[[C]] $Enum[[CC]];
+      $Enum[[CC]] $Function[[f]]($Class[[B]]);
     )cpp"};
   for (const auto &TestCase : TestCases) {
     checkHighlightings(TestCase);
   }
 }
 
 TEST(SemanticHighlighting, GeneratesHighlightsWhenFileChange) {
   class HighlightingsCounterDiagConsumer : public DiagnosticsConsumer {