Index: mlir/include/mlir/IR/DialectBase.td
===================================================================
--- mlir/include/mlir/IR/DialectBase.td
+++ mlir/include/mlir/IR/DialectBase.td
@@ -13,17 +13,28 @@
 #ifndef DIALECTBASE_TD
 #define DIALECTBASE_TD
 
+// Helper for marking deprecated classes or defs. To mark a def as deprecated,
+// mix in the `Deprecate` class with a reason.
+class Deprecated<string reason> {
+  string odsDeprecated = reason;
+}
+
 //===----------------------------------------------------------------------===//
 // Dialect definitions
 //===----------------------------------------------------------------------===//
 
+class EmitFolderBase;
 // Generate 'fold' method with 'ArrayRef<Attribute>' parameter.
 // New code should prefer using 'kEmitFoldAdaptorFolder' and
 // consider 'kEmitRawAttributesFolder' deprecated and to be
 // removed in the future.
-defvar kEmitRawAttributesFolder = 0;
+def kEmitRawAttributesFolder : EmitFolderBase, Deprecated<
+  "'useFoldAPI' of 'kEmitRawAttributesFolder' (default) has been deprecated "
+  # "and is pending removal. Please switch to 'kEmitFoldAdaptorFolder'. See "
+  # "https://discourse.llvm.org/t/psa-new-improved-fold-method-signature-has-landed-please-update-your-downstream-projects/67618"
+> {}
 // Generate 'fold' method with 'FoldAdaptor' parameter.
-defvar kEmitFoldAdaptorFolder = 1;
+def kEmitFoldAdaptorFolder : EmitFolderBase {}
 
 class Dialect {
   // The name of the dialect.
@@ -95,7 +106,7 @@
   bit isExtensible = 0;
 
   // Fold API to use for operations in this dialect.
-  int useFoldAPI = kEmitRawAttributesFolder;
+  EmitFolderBase useFoldAPI = kEmitRawAttributesFolder;
 }
 
 #endif // DIALECTBASE_TD
Index: mlir/include/mlir/IR/OpBase.td
===================================================================
--- mlir/include/mlir/IR/OpBase.td
+++ mlir/include/mlir/IR/OpBase.td
@@ -40,12 +40,6 @@
   string result = r;
 }
 
-// Helper for marking deprecated classes or defs. To mark a def as deprecated,
-// mix in the `Deprecate` class with a reason.
-class Deprecated<string reason> {
-  string odsDeprecated = reason;
-}
-
 //===----------------------------------------------------------------------===//
 // Predicate definitions
 //===----------------------------------------------------------------------===//
Index: mlir/lib/TableGen/Dialect.cpp
===================================================================
--- mlir/lib/TableGen/Dialect.cpp
+++ mlir/lib/TableGen/Dialect.cpp
@@ -11,6 +11,7 @@
 //===----------------------------------------------------------------------===//
 
 #include "mlir/TableGen/Dialect.h"
+#include "llvm/ADT/StringSwitch.h"
 #include "llvm/TableGen/Error.h"
 #include "llvm/TableGen/Record.h"
 
@@ -103,13 +104,18 @@
 }
 
 Dialect::FolderAPI Dialect::getFolderAPI() const {
-  int64_t value = def->getValueAsInt("useFoldAPI");
-  if (value < static_cast<int64_t>(FolderAPI::RawAttributes) ||
-      value > static_cast<int64_t>(FolderAPI::FolderAdaptor))
+  llvm::Record *value = def->getValueAsDef("useFoldAPI");
+  auto converted =
+      llvm::StringSwitch<std::optional<Dialect::FolderAPI>>(value->getName())
+          .Case("kEmitRawAttributesFolder", FolderAPI::RawAttributes)
+          .Case("kEmitFoldAdaptorFolder", FolderAPI::FolderAdaptor)
+          .Default(std::nullopt);
+
+  if (!converted)
     llvm::PrintFatalError(def->getLoc(),
                           "Invalid value for dialect field `useFoldAPI`");
 
-  return static_cast<FolderAPI>(value);
+  return *converted;
 }
 
 bool Dialect::operator==(const Dialect &other) const {
Index: mlir/lib/Tools/mlir-tblgen/MlirTblgenMain.cpp
===================================================================
--- mlir/lib/Tools/mlir-tblgen/MlirTblgenMain.cpp
+++ mlir/lib/Tools/mlir-tblgen/MlirTblgenMain.cpp
@@ -78,11 +78,6 @@
         // Skip anonymous defs.
         if (jt.second->isAnonymous())
           continue;
-        // Skip all outside main file to avoid flagging redundantly.
-        unsigned buf =
-            SrcMgr.FindBufferContainingLoc(jt.second->getLoc().front());
-        if (buf != SrcMgr.getMainFileID())
-          continue;
 
         if (findUse(*jt.second, it.second->getDefInit(), hasUse)) {
           PrintWarning(jt.second->getLoc(),
Index: mlir/test/mlir-tblgen/has-fold-invalid-values.td
===================================================================
--- mlir/test/mlir-tblgen/has-fold-invalid-values.td
+++ mlir/test/mlir-tblgen/has-fold-invalid-values.td
@@ -2,10 +2,12 @@
 
 include "mlir/IR/OpBase.td"
 
+def Bad : EmitFolderBase;
+
 def Test_Dialect : Dialect {
   let name = "test";
   let cppNamespace = "NS";
-  let useFoldAPI = 3;
+  let useFoldAPI = Bad;
 }
 
 def InvalidValue_Op : Op<Test_Dialect, "invalid_op"> {