[clangd] Handle the missing injectedClassNameType in targetDecl.

[merge_guards_bot]

Unit tests: pass. 62057 tests passed, 0 failed and 784 were skipped.

clang-tidy: unknown.

clang-format: pass.

Build artifacts: diff.json, clang-format.patch, CMakeCache.txt, console-log.txt, test-results.xml

clang-tools-extra/clangd/FindTarget.cpp

void add(QualType T, RelSet Flags) {
     struct Visitor : public TypeVisitor<Visitor> {
       TargetFinder &Outer;
       RelSet Flags;
       Visitor(TargetFinder &Outer, RelSet Flags) : Outer(Outer), Flags(Flags) {}
 
       void VisitTagType(const TagType *TT) {
         Outer.add(TT->getAsTagDecl(), Flags);
       }
+
+      void VisitInjectedClassNameType(const InjectedClassNameType *ICNT) {
+        Outer.add(ICNT->getDecl(), Flags);
+      }
+
       void VisitDecltypeType(const DecltypeType *DTT) {
         Outer.add(DTT->getUnderlyingType(), Flags | Rel::Underlying);
       }
       void VisitDeducedType(const DeducedType *DT) {
         // FIXME: In practice this doesn't work: the AutoType you find inside
         // TypeLoc never has a deduced type. https://llvm.org/PR42914
         Outer.add(DT->getDeducedType(), Flags | Rel::Underlying);
       }

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

TEST_F(TargetDeclTest, Types) {
   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", "");
+
+  Code = R"cpp(
+    template <typename T>
+    class Foo {
+      void f([[Foo]] x);
+    };
+  )cpp";
+  EXPECT_DECLS("InjectedClassNameTypeLoc", "class Foo");
 }
 
 TEST_F(TargetDeclTest, ClassTemplate) {
   Code = R"cpp(
     // Implicit specialization.
     template<int x> class Foo{};
     [[Foo<42>]] B;
   )cpp";