Index: unittests/clangd/SymbolCollectorTests.cpp
===================================================================
--- unittests/clangd/SymbolCollectorTests.cpp
+++ unittests/clangd/SymbolCollectorTests.cpp
@@ -325,9 +325,6 @@
     // Namespace alias
     namespace baz = bar;
 
-    // FIXME: using declaration is not supported as the IndexAction will ignore
-    // implicit declarations (the implicit using shadow declaration) by default,
-    // and there is no way to customize this behavior at the moment.
     using bar::v2;
     } // namespace foo
   )";
@@ -354,6 +351,7 @@
                    AllOf(QName("foo::int32_t"), ForCodeCompletion(true)),
                    AllOf(QName("foo::v1"), ForCodeCompletion(true)),
                    AllOf(QName("foo::bar::v2"), ForCodeCompletion(true)),
+                   AllOf(QName("foo::v2"), ForCodeCompletion(true)),
                    AllOf(QName("foo::baz"), ForCodeCompletion(true))}));
 }
 
@@ -1118,6 +1116,17 @@
                   AllOf(QName("Public"), Not(ImplementationDetail()))));
 }
 
+TEST_F(SymbolCollectorTest, UsingDecl) {
+  const std::string Header = R"(
+  void foo();
+  namespace std {
+    using ::foo;
+  }
+  )";
+  runSymbolCollector(Header, /**/ "");
+  EXPECT_THAT(Symbols, Contains(QName("std::foo")));
+}
+
 } // namespace
 } // namespace clangd
 } // namespace clang
Index: unittests/clangd/SymbolInfoTests.cpp
===================================================================
--- unittests/clangd/SymbolInfoTests.cpp
+++ unittests/clangd/SymbolInfoTests.cpp
@@ -167,7 +167,8 @@
         )cpp",
               {CreateExpectedSymbolDetails("foo", "", "c:@F@foo#"),
                CreateExpectedSymbolDetails("foo", "", "c:@F@foo#b#"),
-               CreateExpectedSymbolDetails("foo", "", "c:@F@foo#I#")}},
+               CreateExpectedSymbolDetails("foo", "", "c:@F@foo#I#"),
+               CreateExpectedSymbolDetails("foo", "bar::", "c:@N@bar@UD@foo")}},
           {
               R"cpp( // Multiple symbols returned - implicit conversion
           struct foo {};