Allow type generalizations in if

2 files changed, 20 insertions, 6 deletions

diff --git a/searchlib/src/main/java/com/yahoo/searchlib/rankingexpression/RankingExpression.java b/searchlib/src/main/java/com/yahoo/searchlib/rankingexpression/RankingExpression.java
index 1ec6ea4693b..c8d90e8c4e8 100755
--- a/searchlib/src/main/java/com/yahoo/searchlib/rankingexpression/RankingExpression.java
+++ b/searchlib/src/main/java/com/yahoo/searchlib/rankingexpression/RankingExpression.java
@@ -8,6 +8,8 @@ import com.yahoo.searchlib.rankingexpression.parser.RankingExpressionParser;
 import com.yahoo.searchlib.rankingexpression.parser.TokenMgrError;
 import com.yahoo.searchlib.rankingexpression.rule.ExpressionNode;
 import com.yahoo.searchlib.rankingexpression.rule.SerializationContext;
+import com.yahoo.tensor.TensorType;
+import com.yahoo.tensor.evaluation.TypeContext;
 
 import java.io.File;
 import java.io.FileNotFoundException;
@@ -265,6 +267,16 @@ public class RankingExpression implements Serializable {
     }
 
     /**
+     * Validates the type correctness of the given expression with the given context and
+     * returns the type this expression will produce from the given type context
+     *
+     * @throws IllegalArgumentException if this expression is not type correct in this context
+     */
+    public TensorType type(TypeContext context) {
+        return root.type(context);
+    }
+
+    /**
      * Returns the value of evaluating this expression over the given context.
      *
      * @param context The variable bindings to use for this evaluation.
diff --git a/searchlib/src/main/java/com/yahoo/searchlib/rankingexpression/rule/IfNode.java b/searchlib/src/main/java/com/yahoo/searchlib/rankingexpression/rule/IfNode.java
index 076df327044..4f0ebc1c7e5 100755
--- a/searchlib/src/main/java/com/yahoo/searchlib/rankingexpression/rule/IfNode.java
+++ b/searchlib/src/main/java/com/yahoo/searchlib/rankingexpression/rule/IfNode.java
@@ -49,7 +49,7 @@ public final class IfNode extends CompositeNode {
 
     @Override
     public List<ExpressionNode> children() {
-        List<ExpressionNode> children = new ArrayList<ExpressionNode>(4);
+        List<ExpressionNode> children = new ArrayList<>(4);
         children.add(condition);
         children.add(trueExpression);
         children.add(falseExpression);
@@ -78,11 +78,13 @@ public final class IfNode extends CompositeNode {
     public TensorType type(TypeContext context) {
         TensorType trueType = trueExpression.type(context);
         TensorType falseType = falseExpression.type(context);
-        if ( ! trueType.equals(falseType))
-            throw new IllegalArgumentException("An if expression must produce a value of the same type in both " +
-                                               "alternatives, but the 'true' type is " + trueType + " while the " +
-                                               "'false' type is " + falseType);
-        return trueType;
+
+        // Types of each branch must be compatible; the resulting type is the most general
+        if (trueType.isAssignableTo(falseType)) return falseType;
+        if (falseType.isAssignableTo(trueType)) return trueType;
+        throw new IllegalArgumentException("An if expression must produce compatible types in both " +
+                                           "alternatives, but the 'true' type is " + trueType + " while the " +
+                                           "'false' type is " + falseType);
     }
 
     @Override