[clangd] Handle a few more diag kinds in include fixer.

[sammccall]

Nice!

clangd/IncludeFixer.cpp

for (unsigned Idx = 0; Idx < Info.getNumArgs(); ++Idx) {
       }
     }
     break;
   case diag::err_unknown_typename:
   case diag::err_unknown_typename_suggest:
   case diag::err_typename_nested_not_found:
   case diag::err_no_template:
   case diag::err_no_template_suggest:
+  case diag::err_undeclared_use:
+  case diag::err_undeclared_use_suggest:
+  case diag::err_undeclared_var_use:
+  case diag::err_undeclared_var_use_suggest:
+  case diag::err_no_member: // Could be no member in namespace.
+  case diag::err_no_member_suggest:
     if (LastUnresolvedName) {
       // Try to fix unresolved name caused by missing declaraion.
       // E.g.
       //   clang::SourceManager SM;
       //          ~~~~~~~~~~~~~
       //          UnresolvedName
       //   or
       //   namespace clang {  SourceManager SM; }

unittests/clangd/DiagnosticsTests.cpp

EXPECT_THAT(TU.build().getDiagnostics(),
                   Diag(Test.range("access"),
                        "member access into incomplete type 'ns::X'")));
 }
 
 TEST(IncludeFixerTest, Typo) {
   Annotations Test(R"cpp(
 $insert[[]]namespace ns {
 void foo() {
-  $unqualified[[X]] x;
+  $unqualified1[[X]] x;
+  $unqualified2[[X]]::Nested n;
 }
 }
 void bar() {
-  ns::$qualified[[X]] x; // ns:: is valid.
+  ns::$qualified1[[X]] x; // ns:: is valid.
+  ns::$qualified2[[X]](); // Error: no member in namespace
+
   ::$global[[Global]] glob;
 }
   )cpp");
   auto TU = TestTU::withCode(Test.code());
   auto Index = buildIndexWithSymbol(
       {SymbolWithHeader{"ns::X", "unittest:///x.h", "\"x.h\""},
        SymbolWithHeader{"Global", "unittest:///global.h", "\"global.h\""}});
   TU.ExternalIndex = Index.get();
 
   EXPECT_THAT(
       TU.build().getDiagnostics(),
       UnorderedElementsAre(
-          AllOf(Diag(Test.range("unqualified"), "unknown type name 'X'"),
+          AllOf(Diag(Test.range("unqualified1"), "unknown type name 'X'"),
+                WithFix(Fix(Test.range("insert"), "#include \"x.h\"\n",
+                            "Add include \"x.h\" for symbol ns::X"))),
+          AllOf(Diag(Test.range("unqualified2"),
+                     "use of undeclared identifier 'X'"),
                 WithFix(Fix(Test.range("insert"), "#include \"x.h\"\n",
                             "Add include \"x.h\" for symbol ns::X"))),
-          AllOf(Diag(Test.range("qualified"),
+          AllOf(Diag(Test.range("qualified1"),
                      "no type named 'X' in namespace 'ns'"),
                 WithFix(Fix(Test.range("insert"), "#include \"x.h\"\n",
                             "Add include \"x.h\" for symbol ns::X"))),
+          AllOf(Diag(Test.range("qualified2"),
+                     "no member named 'X' in namespace 'ns'"),
+                WithFix(Fix(Test.range("insert"), "#include \"x.h\"\n",
+                            "Add include \"x.h\" for symbol ns::X"))),
           AllOf(Diag(Test.range("global"),
                      "no type named 'Global' in the global namespace"),
                 WithFix(Fix(Test.range("insert"), "#include \"global.h\"\n",
                             "Add include \"global.h\" for symbol Global")))));
 }
 
 TEST(IncludeFixerTest, MultipleMatchedSymbols) {
   Annotations Test(R"cpp(