diff --git a/mlir/lib/Tools/PDLL/Parser/Parser.cpp b/mlir/lib/Tools/PDLL/Parser/Parser.cpp
--- a/mlir/lib/Tools/PDLL/Parser/Parser.cpp
+++ b/mlir/lib/Tools/PDLL/Parser/Parser.cpp
@@ -955,6 +955,12 @@
   if (failed(parseToken(Token::semicolon,
                         "expected `;` after native declaration")))
     return failure();
+  // TODO: PDL should be able to support constraint results in certain
+  // situations, we should revise this.
+  if (std::is_same<ast::UserConstraintDecl, T>::value && !results.empty()) {
+    return emitError(
+        "native Constraints currently do not support returning results");
+  }
   return T::createNative(ctx, name, arguments, results, optCodeStr, resultType);
 }
 
diff --git a/mlir/test/mlir-pdll/Parser/constraint-failure.pdll b/mlir/test/mlir-pdll/Parser/constraint-failure.pdll
--- a/mlir/test/mlir-pdll/Parser/constraint-failure.pdll
+++ b/mlir/test/mlir-pdll/Parser/constraint-failure.pdll
@@ -116,22 +116,22 @@
 // -----
 
 // CHECK: cannot create a single-element tuple with an element label
-Constraint Foo() -> result: Value;
+Constraint Foo() -> result: Value {}
 
 // -----
 
 // CHECK: cannot create a single-element tuple with an element label
-Constraint Foo() -> (result: Value);
+Constraint Foo() -> (result: Value) {}
 
 // -----
 
 // CHECK: expected identifier constraint
-Constraint Foo() -> ();
+Constraint Foo() -> () {}
 
 // -----
 
 // CHECK: expected `:` before result constraint
-Constraint Foo() -> (result{};
+Constraint Foo() -> (result {};
 
 // -----
 
@@ -141,7 +141,7 @@
 // -----
 
 // CHECK: inline `Attr`, `Value`, and `ValueRange` type constraints are not permitted on arguments or results
-Constraint Foo() -> Value<type>){}
+Constraint Foo() -> Value<type>) {}
 
 // -----
 
@@ -158,3 +158,8 @@
 
 // CHECK: expected `;` after native declaration
 Constraint Foo() [{}]
+
+// -----
+
+// CHECK: native Constraints currently do not support returning results
+Constraint Foo() -> Op;