Index: include/clang/Basic/DiagnosticSemaKinds.td
===================================================================
--- include/clang/Basic/DiagnosticSemaKinds.td
+++ include/clang/Basic/DiagnosticSemaKinds.td
@@ -730,6 +730,9 @@
 def warn_pragma_unused_undeclared_var : Warning<
   "undeclared variable %0 used as an argument for '#pragma unused'">,
   InGroup<IgnoredPragmas>;
+def warn_atl_uuid_deprecated : Warning<
+  "specifying uuid as ATL attribute is deprecated, use __declspec instead">,
+  InGroup<DeprecatedDeclarations>;
 def warn_pragma_unused_expected_var_arg : Warning<
   "only variables can be arguments to '#pragma unused'">,
   InGroup<IgnoredPragmas>;
Index: lib/Parse/ParseDeclCXX.cpp
===================================================================
--- lib/Parse/ParseDeclCXX.cpp
+++ lib/Parse/ParseDeclCXX.cpp
@@ -4151,8 +4151,6 @@
   }
 
   if (!T.consumeClose()) {
-    // FIXME: Warn that this syntax is deprecated, with a Fix-It suggesting
-    // using __declspec(uuid()) instead.
     Attrs.addNew(UuidIdent, SourceRange(UuidLoc, T.getCloseLocation()), nullptr,
                  SourceLocation(), ArgExprs.data(), ArgExprs.size(),
                  AttributeList::AS_Microsoft);
Index: lib/Sema/SemaDeclAttr.cpp
===================================================================
--- lib/Sema/SemaDeclAttr.cpp
+++ lib/Sema/SemaDeclAttr.cpp
@@ -5079,6 +5079,15 @@
     }
   }
 
+  // FIXME: It'd be nice to also emit a fixit removing uuid(...) (and, if it's
+  // the only thing in the [] list, the [] too), and add an insertion of
+  // __declspec(uuid(...)).  But sadly, neither the SourceLocs of the commas
+  // separating attributes nor of the [ and the ] are in the AST.
+  // Cf "SourceLocations of attribute list delimiters – [[ ... , ... ]] etc"
+  // on cfe-dev.
+  if (Attr.isMicrosoftAttribute()) // Check for [uuid(...)] spelling.
+    S.Diag(Attr.getLoc(), diag::warn_atl_uuid_deprecated);
+
   UuidAttr *UA = S.mergeUuidAttr(D, Attr.getRange(),
                                  Attr.getAttributeSpellingListIndex(), StrRef);
   if (UA)
Index: test/Parser/MicrosoftExtensions.cpp
===================================================================
--- test/Parser/MicrosoftExtensions.cpp
+++ test/Parser/MicrosoftExtensions.cpp
@@ -60,7 +60,7 @@
 struct __declspec(uuid("000000A0-0000-0000-C000-000000000049"))
 struct_with_uuid2;
 
-[uuid("000000A0-0000-0000-C000-000000000049")] struct struct_with_uuid3;
+[uuid("000000A0-0000-0000-C000-000000000049")] struct struct_with_uuid3; // expected-warning{{specifying uuid as ATL attribute is deprecated, use __declspec instead}}
 
 struct
 struct_with_uuid2 {} ;
Index: test/Parser/ms-square-bracket-attributes.mm
===================================================================
--- test/Parser/ms-square-bracket-attributes.mm
+++ test/Parser/ms-square-bracket-attributes.mm
@@ -1,4 +1,4 @@
-// RUN: %clang_cc1 -fsyntax-only -std=c++14 -verify -fms-extensions %s
+// RUN: %clang_cc1 -fsyntax-only -std=c++14 -verify -fms-extensions %s -Wno-deprecated-declarations
 
 typedef struct _GUID {
   unsigned long Data1;
Index: test/SemaCXX/ms-uuid.cpp
===================================================================
--- test/SemaCXX/ms-uuid.cpp
+++ test/SemaCXX/ms-uuid.cpp
@@ -1,4 +1,4 @@
-// RUN: %clang_cc1 -fsyntax-only -verify -fms-extensions %s
+// RUN: %clang_cc1 -fsyntax-only -verify -fms-extensions %s -Wno-deprecated-declarations
 
 typedef struct _GUID {
   unsigned long Data1;