[dart2js] new-rti: debug print of named type variable miss

Change-Id: Ib344442c1dc15136408df761852e901abf4b80c3
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/127221
Reviewed-by: Mayank Patke <fishythefish@google.com>
Commit-Queue: Stephen Adams <sra@google.com>

Author: rakudrama

sdk/lib/_internal/js_runtime/lib/rti.dart

@@ -1443,6 +1443,9 @@ class _Universe {
     Object rule = _Universe.findRule(universe, interfaceName);
     assert(rule != null);
     String recipe = TypeRule.lookupTypeVariable(rule, name);
+    if (recipe == null) {
+      throw 'No "$name" in "${Rti._getCanonicalRecipe(environment)}"';
+    }
     return _Universe.evalInEnvironment(universe, environment, recipe);
   }
 

sdk_nnbd/lib/_internal/js_runtime/lib/rti.dart

@@ -1443,6 +1443,9 @@ class _Universe {
     Object rule = _Universe.findRule(universe, interfaceName);
     assert(rule != null);
     String recipe = TypeRule.lookupTypeVariable(rule, name);
+    if (recipe == null) {
+      throw 'No "$name" in "${Rti._getCanonicalRecipe(environment)}"';
+    }
     return _Universe.evalInEnvironment(universe, environment, recipe);
   }