spotting where type check should happen

Author: henriquepaes1

x-pack/plugin/ml/src/main/java/org/elasticsearch/xpack/ml/queries/TextExpansionQueryBuilder.java

@@ -38,6 +38,7 @@
 import java.io.IOException;
 import java.util.List;
 import java.util.Objects;
+import java.util.Set;
 
 import static org.elasticsearch.xpack.core.ClientHelper.ML_ORIGIN;
 import static org.elasticsearch.xpack.core.ClientHelper.executeAsyncWithOrigin;
@@ -59,6 +60,8 @@ public class TextExpansionQueryBuilder extends AbstractQueryBuilder<TextExpansio
     private SetOnce<TextExpansionResults> weightedTokensSupplier;
     private final TokenPruningConfig tokenPruningConfig;
 
+    private static final Set<String> ALLOWED_FIELD_TYPES = Set.of("sparse_vector", "rank_features");
+
     private static final DeprecationLogger deprecationLogger = DeprecationLogger.getLogger(ParseField.class);
     public static final String TEXT_EXPANSION_DEPRECATION_MESSAGE = NAME + " is deprecated. Use sparse_vector instead.";
 
@@ -158,6 +161,8 @@ protected QueryBuilder doRewrite(QueryRewriteContext queryRewriteContext) {
             return weightedTokensToQuery(fieldName, weightedTokensSupplier.get());
         }
 
+        // Do field type check if query won't be rewritten as a WeightedTokensQuery
+
         CoordinatedInferenceAction.Request inferRequest = CoordinatedInferenceAction.Request.forTextInput(
             modelId,
             List.of(modelText),