Handle argument bindings

16 files changed, 277 insertions, 86 deletions

diff --git a/config-model/src/main/java/com/yahoo/searchdefinition/FeatureNames.java b/config-model/src/main/java/com/yahoo/searchdefinition/FeatureNames.java
index a55ce0982dd..649d7bddcc2 100644
--- a/config-model/src/main/java/com/yahoo/searchdefinition/FeatureNames.java
+++ b/config-model/src/main/java/com/yahoo/searchdefinition/FeatureNames.java
@@ -5,6 +5,8 @@
  */
 package com.yahoo.searchdefinition;
 
+import com.yahoo.searchlib.rankingexpression.rule.ReferenceNode;
+
 import java.util.Arrays;
 import java.util.List;
 import java.util.Optional;
@@ -69,7 +71,7 @@ public class FeatureNames {
                            feature.substring(endParenthesis));
     }
 
-    /** Canomicalizes a single argument */
+    /** Canonicalizes a single argument */
     private static String canonicalizeArgument(String argument) {
         if (argument.startsWith("'")) {
             if ( ! argument.endsWith("'"))
@@ -89,20 +91,20 @@ public class FeatureNames {
             return "\"" + argument + "\"";
     }
 
-    public static String asConstantFeature(String constantName) {
-        return canonicalize("constant(\"" + constantName + "\")");
+    public static ReferenceNode.Reference asConstantFeature(String constantName) {
+        return ReferenceNode.Reference.simple("constant", constantName);
     }
 
-    public static String asAttributeFeature(String attributeName) {
-        return canonicalize("attribute(\"" + attributeName + "\")");
+    public static ReferenceNode.Reference asAttributeFeature(String attributeName) {
+        return ReferenceNode.Reference.simple("attribute", attributeName);
     }
 
-    public static String asQueryFeature(String propertyName) {
-        return canonicalize("query(\"" + propertyName + "\")");
+    public static ReferenceNode.Reference asQueryFeature(String propertyName) {
+        return ReferenceNode.Reference.simple("query", propertyName);
     }
 
-    /** Returns true if this is a cpomstant, attribute, or query feature */
-    public static boolean isFeature(String feature) {
+    /** Returns true if this is a constant, attribute, or query feature */
+    public static boolean isSimpleFeature(String feature) {
         return FeatureNames.isConstantFeature(feature) ||
                FeatureNames.isAttributeFeature(feature) ||
                FeatureNames.isQueryFeature(feature);
diff --git a/config-model/src/main/java/com/yahoo/searchdefinition/MapEvaluationTypeContext.java b/config-model/src/main/java/com/yahoo/searchdefinition/MapEvaluationTypeContext.java
index 38a0a23f48a..bf6a95f10c1 100644
--- a/config-model/src/main/java/com/yahoo/searchdefinition/MapEvaluationTypeContext.java
+++ b/config-model/src/main/java/com/yahoo/searchdefinition/MapEvaluationTypeContext.java
@@ -3,12 +3,10 @@ package com.yahoo.searchdefinition;
 
 import com.yahoo.searchlib.rankingexpression.ExpressionFunction;
 import com.yahoo.searchlib.rankingexpression.rule.Arguments;
-import com.yahoo.searchlib.rankingexpression.rule.EvaluationTypeContext;
 import com.yahoo.searchlib.rankingexpression.rule.ExpressionNode;
 import com.yahoo.searchlib.rankingexpression.rule.FunctionReferenceContext;
 import com.yahoo.searchlib.rankingexpression.rule.ReferenceNode;
 import com.yahoo.tensor.TensorType;
-import com.yahoo.tensor.evaluation.MapEvaluationContext;
 import com.yahoo.tensor.evaluation.TypeContext;
 
 import java.util.Collection;
@@ -26,9 +24,9 @@ import java.util.Optional;
  *
  * @author bratseth
  */
-public class MapEvaluationTypeContext extends FunctionReferenceContext implements EvaluationTypeContext {
+public class MapEvaluationTypeContext extends FunctionReferenceContext implements TypeContext {
 
-    private final Map<String, TensorType> featureTypes = new HashMap<>();
+    private final Map<ReferenceNode.Reference, TensorType> featureTypes = new HashMap<>();
 
     public MapEvaluationTypeContext(Collection<ExpressionFunction> functions) {
         super(functions);
@@ -36,33 +34,34 @@ public class MapEvaluationTypeContext extends FunctionReferenceContext implement
 
     public MapEvaluationTypeContext(Map<String, ExpressionFunction> functions,
                                     Map<String, String> bindings,
-                                    Map<String, TensorType> featureTypes) {
+                                    Map<ReferenceNode.Reference, TensorType> featureTypes) {
         super(functions, bindings);
         this.featureTypes.putAll(featureTypes);
     }
 
-    public void setType(String name, TensorType type) {
-        featureTypes.put(FeatureNames.canonicalize(name), type);
+    public void setType(Name name, TensorType type) {
+        // TODO: Use a type parameter if we do this both here and in getType ...
+        if ( ! (name instanceof ReferenceNode.Reference))
+            throw new IllegalArgumentException("Not expecting unstructured names here");
+        featureTypes.put((ReferenceNode.Reference)name, type);
     }
 
-    // TODO: Remove?
     @Override
-    public TensorType getType(String name) {
-        if (FeatureNames.isFeature(name))
-            return featureTypes.get(FeatureNames.canonicalize(name));
-        else
-            return TensorType.empty; // we do not have type information for these. Correct would be either empty or null
-    }
-
-    @Override
-    public TensorType getType(String name, Arguments arguments, String output) {
-        Optional<String> simpleFeature = simpleFeature(name, arguments); // (all simple feature outputs return the same type)
-        if (simpleFeature.isPresent())
-            return featureTypes.get(simpleFeature.get());
-
-        Optional<ExpressionFunction> function = functionInvocation(name, output);
+    public TensorType getType(Name name) {
+        if ( ! (name instanceof ReferenceNode.Reference))
+            throw new IllegalArgumentException("Not expecting unstructured names here");
+        ReferenceNode.Reference reference = (ReferenceNode.Reference)name;
+
+        if (isSimpleFeature(reference)) {
+            // The argument may be a local identifier bound to the actual value
+            String argument = simpleArgument(reference.arguments()).get();
+            reference = ReferenceNode.Reference.simple(reference.name(), bindings.getOrDefault(argument, argument));
+            return featureTypes.get(reference);
+        }
+
+        Optional<ExpressionFunction> function = functionInvocation(reference);
         if (function.isPresent())
-            return function.get().getBody().type(this.withBindings(bind(function.get().arguments())));
+            return function.get().getBody().type(this.withBindings(bind(function.get().arguments(), reference.arguments())));
 
         // We do not know what this is - since we do not have complete knowledge abut the match features
         // in Java we must assume this is a match feature and return the double type - which is the type of all
@@ -71,18 +70,33 @@ public class MapEvaluationTypeContext extends FunctionReferenceContext implement
     }
 
     /**
-     * If the arguments makes a simple feature ("attribute(name)", "constant(name)" or "query(name)",
+     * Return whether the reference (discarding the output) is a simple feature
+     * ("attribute(name)", "constant(name)" or "query(name)").
+     * We disregard the output because all outputs under a simple feature have the same type.
+     */
+    private boolean isSimpleFeature(ReferenceNode.Reference reference) {
+        Optional<String> argument = simpleArgument(reference.arguments());
+        if ( ! argument.isPresent()) return false;
+        return reference.name().equals("attribute") ||
+               reference.name().equals("constant") ||
+               reference.name().equals("query");
+    }
+
+    /**
+     * If the reference (discarding the output) is a simple feature
+     * ("attribute(name)", "constant(name)" or "query(name)"),
      * it is returned. Otherwise empty is returned.
+     * We disregard the output because all outputs under a simple feature have the same type.
      */
-    private Optional<String> simpleFeature(String name, Arguments arguments) {
-        Optional<String> argument = simpleArgument(arguments);
+    private Optional<String> simpleFeature(ReferenceNode.Reference reference) {
+        Optional<String> argument = simpleArgument(reference.arguments());
         if ( ! argument.isPresent()) return Optional.empty();
 
         // The argument may be a "local value" bound to another value, or else it is the "global" argument of the feature
         String actualArgument = bindings.getOrDefault(argument.get(), argument.get());
 
-        String feature = asFeatureString(name, actualArgument);
-        if (FeatureNames.isFeature(feature))
+        String feature = asFeatureString(reference.name(), actualArgument);
+        if (FeatureNames.isSimpleFeature(feature))
             return Optional.of(feature);
         else
             return Optional.empty();
@@ -108,20 +122,24 @@ public class MapEvaluationTypeContext extends FunctionReferenceContext implement
         return Optional.of(refArgument.getName());
     }
 
-    private Optional<ExpressionFunction> functionInvocation(String name, String output) {
-        if (output != null) return Optional.empty();
-        return Optional.ofNullable(functions().get(name));
+    private Optional<ExpressionFunction> functionInvocation(ReferenceNode.Reference reference) {
+        if (reference.output() != null) return Optional.empty();
+        return Optional.ofNullable(functions().get(reference.name()));
     }
 
     /** Binds the given list of formal arguments to their actual values */
-    private Map<String, String> bind(List<String> arguments) {
-        Map<String, String> bindings = new HashMap<>(arguments.size());
-        for (String formalArgument : arguments)
-            bindings.put(formalArgument, null); // TODO
+    private Map<String, String> bind(List<String> formalArguments,
+                                     Arguments invocationArguments) {
+        // TODO: What is our position on argument overloading/argument count differences?
+        Map<String, String> bindings = new HashMap<>(formalArguments.size());
+        for (int i = 0; i < formalArguments.size(); i++)
+            bindings.put(formalArguments.get(i), invocationArguments.expressions().get(i).toString()); // TODO: toString does not work generally
         return bindings;
     }
 
-    public Map<String, TensorType> featureTypes() { return Collections.unmodifiableMap(featureTypes); }
+    public Map<ReferenceNode.Reference, TensorType> featureTypes() {
+        return Collections.unmodifiableMap(featureTypes);
+    }
 
     @Override
     public MapEvaluationTypeContext withBindings(Map<String, String> bindings) {
diff --git a/config-model/src/main/java/com/yahoo/searchdefinition/RankProfile.java b/config-model/src/main/java/com/yahoo/searchdefinition/RankProfile.java
index 51c7618acff..0b0c0c9e0ca 100644
--- a/config-model/src/main/java/com/yahoo/searchdefinition/RankProfile.java
+++ b/config-model/src/main/java/com/yahoo/searchdefinition/RankProfile.java
@@ -32,6 +32,7 @@ import java.util.LinkedHashMap;
 import java.util.LinkedHashSet;
 import java.util.List;
 import java.util.Map;
+import java.util.Optional;
 import java.util.Set;
 import java.util.stream.Collectors;
 
@@ -357,14 +358,14 @@ public class RankProfile implements Serializable, Cloneable {
 
     /** Returns a read-only view of the summary features to use in this profile. This is never null */
     public Set<ReferenceNode> getSummaryFeatures() {
-        if (summaryFeatures!=null) return Collections.unmodifiableSet(summaryFeatures);
-        if (getInherited()!=null) return getInherited().getSummaryFeatures();
+        if (summaryFeatures != null) return Collections.unmodifiableSet(summaryFeatures);
+        if (getInherited() != null) return getInherited().getSummaryFeatures();
         return Collections.emptySet();
     }
 
     public void addSummaryFeature(ReferenceNode feature) {
-        if (summaryFeatures==null)
-            summaryFeatures=new LinkedHashSet<>();
+        if (summaryFeatures == null)
+            summaryFeatures = new LinkedHashSet<>();
         summaryFeatures.add(feature);
     }
 
@@ -766,16 +767,18 @@ public class RankProfile implements Serializable, Cloneable {
         for (QueryProfileType queryProfileType : queryProfiles.getTypeRegistry().allComponents()) {
             for (FieldDescription field : queryProfileType.declaredFields().values()) {
                 TensorType type = field.getType().asTensorType();
-                if ( ! FeatureNames.isQueryFeature(field.getName())) continue;
-                String feature = FeatureNames.canonicalize(field.getName());
-                TensorType existingType = context.getType(feature);
+                Optional<ReferenceNode.Reference> feature = ReferenceNode.Reference.simple(field.getName());
+                if ( ! feature.isPresent() || ! feature.get().name().equals("query")) continue;
+
+                TensorType existingType = context.getType(feature.get());
                 if (existingType != null)
                     type = existingType.dimensionwiseGeneralizationWith(type).orElseThrow( () ->
                         new IllegalArgumentException(queryProfileType + " contains query feature " + feature +
                                                      " with type " + field.getType().asTensorType() +
                                                      ", but this is already defined " +
-                                                     "in another query profile with type " + context.getType(feature)));
-                context.setType(feature, type);
+                                                     "in another query profile with type " +
+                                                     context.getType(feature.get())));
+                context.setType(feature.get(), type);
             }
         }
 
diff --git a/config-model/src/main/java/com/yahoo/searchdefinition/SearchBuilder.java b/config-model/src/main/java/com/yahoo/searchdefinition/SearchBuilder.java
index 469f29098ad..e7cd21ac834 100644
--- a/config-model/src/main/java/com/yahoo/searchdefinition/SearchBuilder.java
+++ b/config-model/src/main/java/com/yahoo/searchdefinition/SearchBuilder.java
@@ -18,6 +18,7 @@ import com.yahoo.searchdefinition.parser.TokenMgrError;
 import com.yahoo.searchdefinition.processing.Processing;
 import com.yahoo.vespa.documentmodel.DocumentModel;
 import com.yahoo.vespa.model.container.search.QueryProfiles;
+import com.yahoo.yolean.Exceptions;
 
 import java.io.File;
 import java.io.IOException;
@@ -153,7 +154,7 @@ public class SearchBuilder {
         } catch (TokenMgrError e) {
             throw new ParseException("Unknown symbol: " + e.getMessage());
         } catch (ParseException pe) {
-            throw new ParseException(stream.formatException(pe.getMessage()));
+            throw new ParseException(stream.formatException(Exceptions.toMessageString(pe)));
         }
         return importRawSearch(search);
     }
diff --git a/config-model/src/test/java/com/yahoo/searchdefinition/FeatureNamesTestCase.java b/config-model/src/test/java/com/yahoo/searchdefinition/FeatureNamesTestCase.java
index 1f60ad870ec..182aaba5be8 100644
--- a/config-model/src/test/java/com/yahoo/searchdefinition/FeatureNamesTestCase.java
+++ b/config-model/src/test/java/com/yahoo/searchdefinition/FeatureNamesTestCase.java
@@ -42,17 +42,20 @@ public class FeatureNamesTestCase {
 
     @Test
     public void testConstantFeature() {
-        assertEquals("constant(\"foo/bar\")", FeatureNames.asConstantFeature("foo/bar"));
+        assertEquals("constant(\"foo/bar\")",
+                     FeatureNames.asConstantFeature("foo/bar").toString());
     }
 
     @Test
     public void testAttributeFeature() {
-        assertEquals("attribute(foo)", FeatureNames.asAttributeFeature("foo"));
+        assertEquals("attribute(foo)",
+                     FeatureNames.asAttributeFeature("foo").toString());
     }
 
     @Test
     public void testQueryFeature() {
-        assertEquals("query(\"foo.bar\")", FeatureNames.asQueryFeature("foo.bar"));
+        assertEquals("query(\"foo.bar\")",
+                     FeatureNames.asQueryFeature("foo.bar").toString());
     }
 
 }
diff --git a/config-model/src/test/java/com/yahoo/searchdefinition/processing/RankingExpressionTypeValidatorTestCase.java b/config-model/src/test/java/com/yahoo/searchdefinition/processing/RankingExpressionTypeValidatorTestCase.java
index db3b12db1bf..b8117178c74 100644
--- a/config-model/src/test/java/com/yahoo/searchdefinition/processing/RankingExpressionTypeValidatorTestCase.java
+++ b/config-model/src/test/java/com/yahoo/searchdefinition/processing/RankingExpressionTypeValidatorTestCase.java
@@ -1,22 +1,33 @@
 // Copyright 2018 Yahoo Holdings. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
 package com.yahoo.searchdefinition.processing;
 
+import com.yahoo.searchdefinition.RankProfile;
 import com.yahoo.searchdefinition.RankProfileRegistry;
+import com.yahoo.searchdefinition.Search;
 import com.yahoo.searchdefinition.SearchBuilder;
+import com.yahoo.searchlib.rankingexpression.rule.ReferenceNode;
+import com.yahoo.tensor.TensorType;
 import com.yahoo.yolean.Exceptions;
 import org.junit.Test;
+
+import java.util.Map;
+import java.util.stream.Collectors;
+
 import static com.yahoo.config.model.test.TestUtil.joinLines;
 import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.fail;
 
+/**
+ * @author bratseth
+ */
 public class RankingExpressionTypeValidatorTestCase {
 
     @Test
     public void tensorFirstPhaseMustProduceDouble() throws Exception {
         try {
             RankProfileRegistry rankProfileRegistry = new RankProfileRegistry();
-            SearchBuilder searchBuilder = new SearchBuilder(rankProfileRegistry);
-            searchBuilder.importString(joinLines(
+            SearchBuilder builder = new SearchBuilder(rankProfileRegistry);
+            builder.importString(joinLines(
                     "search test {",
                     "  document test { ",
                     "    field a type tensor(x[],y[]) {",
@@ -30,7 +41,7 @@ public class RankingExpressionTypeValidatorTestCase {
                     "  }",
                     "}"
             ));
-            searchBuilder.build();
+            builder.build();
             fail("Expected exception");
         }
         catch (IllegalArgumentException expected) {
@@ -43,8 +54,8 @@ public class RankingExpressionTypeValidatorTestCase {
     public void tensorSecondPhaseMustProduceDouble() throws Exception {
         try {
             RankProfileRegistry rankProfileRegistry = new RankProfileRegistry();
-            SearchBuilder searchBuilder = new SearchBuilder(rankProfileRegistry);
-            searchBuilder.importString(joinLines(
+            SearchBuilder builder = new SearchBuilder(rankProfileRegistry);
+            builder.importString(joinLines(
                     "search test {",
                     "  document test { ",
                     "    field a type tensor(x[],y[]) {",
@@ -61,7 +72,7 @@ public class RankingExpressionTypeValidatorTestCase {
                     "  }",
                     "}"
             ));
-            searchBuilder.build();
+            builder.build();
             fail("Expected exception");
         }
         catch (IllegalArgumentException expected) {
@@ -101,4 +112,42 @@ public class RankingExpressionTypeValidatorTestCase {
         }
     }
 
+    @Test
+    public void testMacroInvocationTypes() throws Exception {
+        RankProfileRegistry rankProfileRegistry = new RankProfileRegistry();
+        SearchBuilder builder = new SearchBuilder(rankProfileRegistry);
+        builder.importString(joinLines(
+                "search test {",
+                "  document test { ",
+                "    field a type tensor(x[],y[]) {",
+                "      indexing: attribute",
+                "    }",
+                "    field b type tensor(z[10]) {",
+                "      indexing: attribute",
+                "    }",
+                "  }",
+                "  rank-profile my_rank_profile {",
+                "    macro macro1(attribute_to_use) {",
+                "      expression: attribute(attribute_to_use)",
+                "    }",
+                "    summary-features {",
+                "      macro1(a)",
+                "      macro1(b)",
+                "    }",
+                "  }",
+                "}"
+        ));
+        builder.build();
+        RankProfile profile =
+                builder.getRankProfileRegistry().getRankProfile(builder.getSearch(), "my_rank_profile");
+        assertEquals(TensorType.fromSpec("tensor(x[],y[])"),
+                     summaryFeatures(profile).get("macro1(a)").type(profile.typeContext(builder.getQueryProfileRegistry())));
+        assertEquals(TensorType.fromSpec("tensor(z[10])"),
+                     summaryFeatures(profile).get("macro1(b)").type(profile.typeContext(builder.getQueryProfileRegistry())));
+    }
+
+    private Map<String, ReferenceNode> summaryFeatures(RankProfile profile) {
+        return profile.getSummaryFeatures().stream().collect(Collectors.toMap(f -> f.toString(), f -> f));
+    }
+
 }
diff --git a/searchlib/src/main/java/com/yahoo/searchlib/rankingexpression/FeatureList.java b/searchlib/src/main/java/com/yahoo/searchlib/rankingexpression/FeatureList.java
index 49466f1974d..f0532d9d433 100755
--- a/searchlib/src/main/java/com/yahoo/searchlib/rankingexpression/FeatureList.java
+++ b/searchlib/src/main/java/com/yahoo/searchlib/rankingexpression/FeatureList.java
@@ -91,8 +91,8 @@ public class FeatureList implements Iterable<ReferenceNode> {
     /**
      * Returns the feature at the given index.
      *
-     * @param i The index of the feature to return.
-     * @return The featuer at the given index.
+     * @param i the index of the feature to return.
+     * @return the feature at the given index.
      */
     public ReferenceNode get(int i) {
         return features.get(i);
@@ -137,4 +137,5 @@ public class FeatureList implements Iterable<ReferenceNode> {
     public Iterator<ReferenceNode> iterator() {
         return features.iterator();
     }
+
 }
diff --git a/searchlib/src/main/java/com/yahoo/searchlib/rankingexpression/evaluation/ArrayContext.java b/searchlib/src/main/java/com/yahoo/searchlib/rankingexpression/evaluation/ArrayContext.java
index 5f8daa69ecf..486affe9371 100644
--- a/searchlib/src/main/java/com/yahoo/searchlib/rankingexpression/evaluation/ArrayContext.java
+++ b/searchlib/src/main/java/com/yahoo/searchlib/rankingexpression/evaluation/ArrayContext.java
@@ -82,8 +82,8 @@ public class ArrayContext extends AbstractArrayContext implements Cloneable {
     }
 
     @Override
-    public TensorType getType(String name) {
-        Integer index = nameToIndex().get(name);
+    public TensorType getType(Name name) {
+        Integer index = nameToIndex().get(name.toString());
         if (index == null) return null;
         return values[index].type();
     }
diff --git a/searchlib/src/main/java/com/yahoo/searchlib/rankingexpression/evaluation/DoubleOnlyArrayContext.java b/searchlib/src/main/java/com/yahoo/searchlib/rankingexpression/evaluation/DoubleOnlyArrayContext.java
index 0625e8506cc..01b8bffe995 100644
--- a/searchlib/src/main/java/com/yahoo/searchlib/rankingexpression/evaluation/DoubleOnlyArrayContext.java
+++ b/searchlib/src/main/java/com/yahoo/searchlib/rankingexpression/evaluation/DoubleOnlyArrayContext.java
@@ -68,7 +68,7 @@ public class DoubleOnlyArrayContext extends AbstractArrayContext {
     }
 
     @Override
-    public TensorType getType(String name) { return TensorType.empty; }
+    public TensorType getType(Name name) { return TensorType.empty; }
 
     /** Perform a slow lookup by name */
     @Override
diff --git a/searchlib/src/main/java/com/yahoo/searchlib/rankingexpression/evaluation/MapContext.java b/searchlib/src/main/java/com/yahoo/searchlib/rankingexpression/evaluation/MapContext.java
index a81d0c89f8f..c7679ea9e55 100644
--- a/searchlib/src/main/java/com/yahoo/searchlib/rankingexpression/evaluation/MapContext.java
+++ b/searchlib/src/main/java/com/yahoo/searchlib/rankingexpression/evaluation/MapContext.java
@@ -42,7 +42,7 @@ public class MapContext extends Context {
 
     /** Returns the type of the given value key, or null if it is not bound. */
     @Override
-    public TensorType getType(String key) {
+    public TensorType getType(Name key) {
         Value value = bindings.get(key);
         if (value == null) return null;
         return value.type();
diff --git a/searchlib/src/main/java/com/yahoo/searchlib/rankingexpression/evaluation/MapTypeContext.java b/searchlib/src/main/java/com/yahoo/searchlib/rankingexpression/evaluation/MapTypeContext.java
index d461ae52cbe..2ddc8213d94 100644
--- a/searchlib/src/main/java/com/yahoo/searchlib/rankingexpression/evaluation/MapTypeContext.java
+++ b/searchlib/src/main/java/com/yahoo/searchlib/rankingexpression/evaluation/MapTypeContext.java
@@ -15,18 +15,18 @@ import java.util.Map;
  */
 public class MapTypeContext implements TypeContext {
 
-    private final Map<String, TensorType> featureTypes = new HashMap<>();
+    private final Map<Name, TensorType> featureTypes = new HashMap<>();
 
     public void setType(String name, TensorType type) {
-        featureTypes.put(name, type);
+        featureTypes.put(new Name(name), type);
     }
 
     @Override
-    public TensorType getType(String name) {
+    public TensorType getType(Name name) {
         return featureTypes.get(name);
     }
 
     /** Returns an unmodifiable map of the bindings in this */
-    public Map<String, TensorType> bindings() { return Collections.unmodifiableMap(featureTypes); }
+    public Map<Name, TensorType> bindings() { return Collections.unmodifiableMap(featureTypes); }
 
 }
diff --git a/searchlib/src/main/java/com/yahoo/searchlib/rankingexpression/rule/Arguments.java b/searchlib/src/main/java/com/yahoo/searchlib/rankingexpression/rule/Arguments.java
index fb9a7cb9ad7..d7163fe9166 100644
--- a/searchlib/src/main/java/com/yahoo/searchlib/rankingexpression/rule/Arguments.java
+++ b/searchlib/src/main/java/com/yahoo/searchlib/rankingexpression/rule/Arguments.java
@@ -13,7 +13,8 @@ import java.util.List;
 
 /**
  * A set of argument expressions to a function or feature.
- * This is immutable.
+ * This is a value object.
+ *.
  *
  * @author bratseth
  */
@@ -22,7 +23,11 @@ public final class Arguments implements Serializable {
     private final ImmutableList<ExpressionNode> expressions;
 
     public Arguments() {
-        this(null);
+        this(ImmutableList.of());
+    }
+
+    public Arguments(ExpressionNode singleArgument) {
+        this(ImmutableList.of(singleArgument));
     }
 
     public Arguments(List<? extends ExpressionNode> expressions) {
@@ -62,8 +67,9 @@ public final class Arguments implements Serializable {
     }
 
     @Override
-    public boolean equals(Object rhs) {
-        return rhs instanceof Arguments && expressions.equals(((Arguments)rhs).expressions);
+    public boolean equals(Object other) {
+        if (other == this) return true;
+        return other instanceof Arguments && expressions.equals(((Arguments)other).expressions);
     }
 
     @Override
diff --git a/searchlib/src/main/java/com/yahoo/searchlib/rankingexpression/rule/ReferenceNode.java b/searchlib/src/main/java/com/yahoo/searchlib/rankingexpression/rule/ReferenceNode.java
index ebfef21a815..e121fa12b5f 100755
--- a/searchlib/src/main/java/com/yahoo/searchlib/rankingexpression/rule/ReferenceNode.java
+++ b/searchlib/src/main/java/com/yahoo/searchlib/rankingexpression/rule/ReferenceNode.java
@@ -9,8 +9,13 @@ import com.yahoo.tensor.TensorType;
 import com.yahoo.tensor.evaluation.TypeContext;
 
 import java.util.ArrayDeque;
+import java.util.Arrays;
 import java.util.Deque;
 import java.util.List;
+import java.util.Objects;
+import java.util.Optional;
+import java.util.regex.Pattern;
+import java.util.stream.Collectors;
 
 /**
  * A node referring either to a value in the context or to a named ranking expression (function aka macro).
@@ -31,6 +36,7 @@ public final class ReferenceNode extends CompositeNode {
     }
 
     public ReferenceNode(String name, List<? extends ExpressionNode> arguments, String output) {
+        Objects.requireNonNull(name, "name cannot be null");
         this.name = name;
         this.arguments = arguments != null ? new Arguments(arguments) : new Arguments();
         this.output = output;
@@ -119,11 +125,10 @@ public final class ReferenceNode extends CompositeNode {
 
     @Override
     public TensorType type(TypeContext context) {
-        String feature = toString(new SerializationContext(), null, false);
-        TensorType type = context.getType(feature);
-        // TensorType type = context.getType(name, arguments, output); TODO
+        TensorType type = context.getType(new Reference(name, arguments, output,
+                                                        toString(new SerializationContext(), null, true)));
         if (type == null)
-            throw new IllegalArgumentException("Unknown feature '" + feature + "'");
+            throw new IllegalArgumentException("Unknown feature '" + toString() + "'");
         return type;
     }
 
@@ -139,4 +144,82 @@ public final class ReferenceNode extends CompositeNode {
         return new ReferenceNode(name, newChildren, output);
     }
 
+    /** Wraps the content of this in a form which can be passed to a type context */
+    // TODO: Extract to top level?
+    public static class Reference extends TypeContext.Name {
+
+        private static final Pattern identifierRegexp = Pattern.compile("[A-Za-z0-9_][A-Za-z0-9_-]*");
+
+        private final String name;
+        private final Arguments arguments;
+
+        /** The output, or null if none */
+        private final String output;
+
+        public Reference(String name, Arguments arguments, String output, String stringForm) {
+            super(stringForm);
+            Objects.requireNonNull(name, "name cannot be null");
+            Objects.requireNonNull(arguments, "arguments cannot be null");
+            Objects.requireNonNull(stringForm, "stringForm cannot be null");
+            this.name = name;
+            this.arguments = arguments;
+            this.output = output;
+        }
+
+        public String name() { return name; }
+        public Arguments arguments() { return arguments; }
+        public String output() { return output; }
+
+        /** Creates a reference to a simple feature consisting of a name and a single argument */
+        public static Reference simple(String name, String argumentValue) {
+            return new Reference(name,
+                                 new Arguments(new ReferenceNode(argumentValue)),
+                                 null,
+                                 name + "(" + quoteIfNecessary(argumentValue) + ")");
+        }
+
+        /**
+         * Returns the given simple feature as a reference, or empty if it is not a valid simple
+         * feature string on the form name(argument).
+         */
+        public static Optional<Reference> simple(String feature) {
+            int startParenthesis = feature.indexOf('(');
+            if (startParenthesis < 0)
+                return Optional.empty();
+            int endParenthesis = feature.lastIndexOf(')');
+            String featureName = feature.substring(0, startParenthesis);
+            if (startParenthesis < 1 || endParenthesis < startParenthesis) return Optional.empty();
+            String argument = feature.substring(startParenthesis + 1, endParenthesis);
+            if (argument.startsWith("'") || argument.startsWith("\""))
+                argument = argument.substring(1);
+            if (argument.endsWith("'") || argument.endsWith("\""))
+                argument = argument.substring(0, argument.length() - 1);
+            return Optional.of(simple(featureName, argument));
+        }
+
+        private static String quoteIfNecessary(String s) {
+            if (identifierRegexp.matcher(s).matches())
+                return s;
+            else
+                return "\"" + s + "\"";
+        }
+
+        @Override
+        public boolean equals(Object o) {
+            if (o == this) return true;
+            if ( ! (o instanceof Reference)) return false;
+            Reference other = (Reference)o;
+            if ( ! Objects.equals(other.name, this.name)) return false;
+            if ( ! Objects.equals(other.arguments, this.arguments)) return false;
+            if ( ! Objects.equals(other.output, this.output)) return false;
+            return true;
+        }
+
+        @Override
+        public int hashCode() {
+            return Objects.hash(name, arguments, output);
+        }
+
+    }
+
 }
diff --git a/vespajlib/src/main/java/com/yahoo/tensor/evaluation/MapEvaluationContext.java b/vespajlib/src/main/java/com/yahoo/tensor/evaluation/MapEvaluationContext.java
index 9fe6b7d053f..078f2e39815 100644
--- a/vespajlib/src/main/java/com/yahoo/tensor/evaluation/MapEvaluationContext.java
+++ b/vespajlib/src/main/java/com/yahoo/tensor/evaluation/MapEvaluationContext.java
@@ -20,8 +20,8 @@ public class MapEvaluationContext implements EvaluationContext {
     public void put(String name, Tensor tensor) { bindings.put(name, tensor); }
 
     @Override
-    public TensorType getType(String name) {
-        Tensor tensor = bindings.get(name);
+    public TensorType getType(Name name) {
+        Tensor tensor = bindings.get(name.toString());
         if (tensor == null) return null;
         return tensor.type();
     }
diff --git a/vespajlib/src/main/java/com/yahoo/tensor/evaluation/TypeContext.java b/vespajlib/src/main/java/com/yahoo/tensor/evaluation/TypeContext.java
index 760a225efdf..ecb3a801324 100644
--- a/vespajlib/src/main/java/com/yahoo/tensor/evaluation/TypeContext.java
+++ b/vespajlib/src/main/java/com/yahoo/tensor/evaluation/TypeContext.java
@@ -16,6 +16,31 @@ public interface TypeContext {
      * @return returns the type of the tensor which will be returned by calling getTensor(name)
      *         or null if getTensor will return null.
      */
-    TensorType getType(String name);
+    TensorType getType(Name name);
+
+    /** A name which is just a string. Names are value objects. */
+    class Name {
+
+        private final String name;
+
+        public Name(String name) {
+            this.name = name;
+        }
+
+        @Override
+        public String toString() { return name; }
+
+        @Override
+        public int hashCode() { return name.hashCode(); }
+
+        @Override
+        public boolean equals(Object other) {
+            if (other == this) return true;
+            if ( ! (other instanceof Name)) return false;
+            return ((Name)other).name.equals(this.name);
+        }
+
+    }
+
 
 }
diff --git a/vespajlib/src/main/java/com/yahoo/tensor/evaluation/VariableTensor.java b/vespajlib/src/main/java/com/yahoo/tensor/evaluation/VariableTensor.java
index 34beb465d4c..5f809a3d2b1 100644
--- a/vespajlib/src/main/java/com/yahoo/tensor/evaluation/VariableTensor.java
+++ b/vespajlib/src/main/java/com/yahoo/tensor/evaluation/VariableTensor.java
@@ -45,7 +45,7 @@ public class VariableTensor extends PrimitiveTensorFunction {
 
     @Override
     public TensorType type(TypeContext context) {
-        TensorType givenType = context.getType(name);
+        TensorType givenType = context.getType(new TypeContext.Name(name));
         if (givenType == null) return null;
         verifyType(givenType);
         return givenType;