3 files changed, 78 insertions, 2 deletions
diff --git a/clang-tools-extra/test/clang-tidy/Inputs/absl/external-file.h b/clang-tools-extra/test/clang-tidy/Inputs/absl/external-file.h
index 94f6687b501..11e2e4aa96c 100644
--- a/clang-tools-extra/test/clang-tidy/Inputs/absl/external-file.h
+++ b/clang-tools-extra/test/clang-tidy/Inputs/absl/external-file.h
@@ -1 +1,6 @@
-namespace absl {}
+namespace absl {
+namespace base_internal {
+void InternalFunction() {}
+} // namespace base_internal 
+} //namespace absl
+void DirectAccess2() { absl::base_internal::InternalFunction(); }
diff --git a/clang-tools-extra/test/clang-tidy/Inputs/absl/strings/internal-file.h b/clang-tools-extra/test/clang-tidy/Inputs/absl/strings/internal-file.h
index 94f6687b501..6014278e260 100644
--- a/clang-tools-extra/test/clang-tidy/Inputs/absl/strings/internal-file.h
+++ b/clang-tools-extra/test/clang-tidy/Inputs/absl/strings/internal-file.h
@@ -1 +1,33 @@
-namespace absl {}
+namespace std {
+struct string {
+  string(const char *);
+  ~string();
+};
+} // namespace std
+
+namespace absl {
+std::string StringsFunction(std::string s1) { return s1; }
+class SomeContainer {};
+namespace strings_internal {
+void InternalFunction() {}
+template <class P> P InternalTemplateFunction(P a) {}
+} // namespace strings_internal
+
+namespace container_internal {
+struct InternalStruct {};
+} // namespace container_internal
+} // namespace absl
+
+// should not trigger warnings because inside Abseil files
+void DirectAcessInternal() {
+  absl::strings_internal::InternalFunction();
+  absl::strings_internal::InternalTemplateFunction<std::string>("a");
+}
+
+class FriendUsageInternal {
+  friend struct absl::container_internal::InternalStruct;
+};
+
+namespace absl {
+void OpeningNamespaceInternally() { strings_internal::InternalFunction(); }
+} // namespace absl
diff --git a/clang-tools-extra/test/clang-tidy/abseil-no-internal-dependencies.cpp b/clang-tools-extra/test/clang-tidy/abseil-no-internal-dependencies.cpp
new file mode 100644
index 00000000000..bd56cb04df7
--- /dev/null
+++ b/clang-tools-extra/test/clang-tidy/abseil-no-internal-dependencies.cpp
@@ -0,0 +1,39 @@
+// RUN: %check_clang_tidy %s abseil-no-internal-dependencies %t,  -- -- -I %S/Inputs
+// RUN: clang-tidy -checks='-*, abseil-no-internal-dependencies' -header-filter='.*' %s -- -I %S/Inputs 2>&1 | FileCheck %s
+
+#include "absl/strings/internal-file.h"
+// CHECK-NOT: warning:
+
+#include "absl/external-file.h"
+// CHECK: absl/external-file.h:6:24: warning: do not reference any 'internal' namespaces; those implementation details are reserved to Abseil [abseil-no-internal-dependencies]
+
+void DirectAcess() {
+  absl::strings_internal::InternalFunction();
+  // CHECK-MESSAGES: :[[@LINE-1]]:3: warning: do not reference any 'internal' namespaces; those implementation details are reserved to Abseil
+
+  absl::strings_internal::InternalTemplateFunction<std::string>("a");
+  // CHECK-MESSAGES: :[[@LINE-1]]:3: warning: do not reference any 'internal' namespaces; those implementation details are reserved to Abseil
+}
+
+class FriendUsage {
+  friend struct absl::container_internal::InternalStruct;
+  // CHECK-MESSAGES: :[[@LINE-1]]:17: warning: do not reference any 'internal' namespaces; those implementation details are reserved to Abseil
+};
+
+namespace absl {
+void OpeningNamespace() {
+  strings_internal::InternalFunction();
+  // CHECK-MESSAGES: :[[@LINE-1]]:3: warning: do not reference any 'internal' namespaces; those implementation details are reserved to Abseil
+}
+} // namespace absl
+
+// should not trigger warnings
+void CorrectUsage() {
+  std::string Str = absl::StringsFunction("a");
+  absl::SomeContainer b;
+}
+
+namespace absl {
+SomeContainer b;
+std::string Str = absl::StringsFunction("a");
+} // namespace absl