Resolve slice dimension

40 files changed, 195 insertions, 94 deletions

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 fef7ff56763..08475813317 100644
--- a/config-model/src/main/java/com/yahoo/searchdefinition/MapEvaluationTypeContext.java
+++ b/config-model/src/main/java/com/yahoo/searchdefinition/MapEvaluationTypeContext.java
@@ -104,7 +104,6 @@ public class MapEvaluationTypeContext extends FunctionReferenceContext implement
     @Override
     public TensorType getType(Reference reference) {
         // computeIfAbsent without concurrent modification due to resolve adding more resolved entries:
-
         boolean canBeResolvedGlobally = referenceCanBeResolvedGlobally(reference);
 
         TensorType resolvedType = resolvedTypes.get(reference);
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 5b842b002bd..49c52b21907 100644
--- a/config-model/src/main/java/com/yahoo/searchdefinition/RankProfile.java
+++ b/config-model/src/main/java/com/yahoo/searchdefinition/RankProfile.java
@@ -998,7 +998,8 @@ public class RankProfile implements Cloneable {
         return featureTypes;
     }
     
-    public MapEvaluationTypeContext typeContext(QueryProfileRegistry queryProfiles, Map<Reference, TensorType> featureTypes) {
+    public MapEvaluationTypeContext typeContext(QueryProfileRegistry queryProfiles,
+                                                Map<Reference, TensorType> featureTypes) {
         MapEvaluationTypeContext context = new MapEvaluationTypeContext(getExpressionFunctions(), featureTypes);
 
         // Add small and large constants, respectively
diff --git a/config-model/src/main/java/com/yahoo/searchdefinition/derived/RawRankProfile.java b/config-model/src/main/java/com/yahoo/searchdefinition/derived/RawRankProfile.java
index 75703c33f07..9370075bcf3 100644
--- a/config-model/src/main/java/com/yahoo/searchdefinition/derived/RawRankProfile.java
+++ b/config-model/src/main/java/com/yahoo/searchdefinition/derived/RawRankProfile.java
@@ -63,8 +63,8 @@ public class RawRankProfile implements RankProfilesConfig.Producer {
                           QueryProfileRegistry queryProfiles, ImportedMlModels importedModels,
                           AttributeFields attributeFields, ModelContext.Properties deployProperties) {
         this.name = rankProfile.name();
-        compressedProperties = compress(new Deriver(rankProfile.compile(queryProfiles, importedModels),
-                                                    attributeFields, deployProperties).derive(largeExpressions));
+        compressedProperties = compress(new Deriver(rankProfile.compile(queryProfiles, importedModels), attributeFields, deployProperties, queryProfiles)
+                                                .derive(largeExpressions));
     }
 
     private Compressor.Compression compress(List<Pair<String, String>> properties) {
@@ -156,7 +156,10 @@ public class RawRankProfile implements RankProfilesConfig.Producer {
         /**
          * Creates a raw rank profile from the given rank profile
          */
-        Deriver(RankProfile compiled, AttributeFields attributeFields, ModelContext.Properties deployProperties) {
+        Deriver(RankProfile compiled,
+                AttributeFields attributeFields,
+                ModelContext.Properties deployProperties,
+                QueryProfileRegistry queryProfiles) {
             rankprofileName = compiled.name();
             attributeTypes = compiled.getAttributeTypes();
             queryFeatureTypes = compiled.getQueryFeatureTypes();
@@ -179,7 +182,9 @@ public class RawRankProfile implements RankProfilesConfig.Producer {
             Map<String, RankProfile.RankingExpressionFunction> functions = compiled.getFunctions();
             List<ExpressionFunction> functionExpressions = functions.values().stream().map(f -> f.function()).collect(Collectors.toList());
             Map<String, String> functionProperties = new LinkedHashMap<>();
-            SerializationContext functionSerializationContext = new SerializationContext(functionExpressions);
+            SerializationContext functionSerializationContext = new SerializationContext(functionExpressions,
+                                                                                         Map.of(),
+                                                                                         compiled.typeContext(queryProfiles));
 
             if (firstPhaseRanking != null) {
                 functionProperties.putAll(firstPhaseRanking.getRankProperties(functionSerializationContext));
@@ -201,8 +206,8 @@ public class RawRankProfile implements RankProfilesConfig.Producer {
         }
 
         private void derivePropertiesAndFeaturesFromFunctions(Map<String, RankProfile.RankingExpressionFunction> functions,
-                                                                     Map<String, String> functionProperties,
-                                                                     SerializationContext functionContext) {
+                                                              Map<String, String> functionProperties,
+                                                              SerializationContext functionContext) {
             if (functions.isEmpty()) return;
 
             replaceFunctionFeatures(summaryFeatures, functionContext);
diff --git a/config-model/src/test/derived/slice/rank-profiles.cfg b/config-model/src/test/derived/slice/rank-profiles.cfg
new file mode 100644
index 00000000000..75725b81ecf
--- /dev/null
+++ b/config-model/src/test/derived/slice/rank-profiles.cfg
@@ -0,0 +1,25 @@
+rankprofile[].name "default"
+rankprofile[].fef.property[].name "vespa.type.query.myTensor"
+rankprofile[].fef.property[].value "tensor<float>(key{})"
+rankprofile[].name "unranked"
+rankprofile[].fef.property[].name "vespa.rank.firstphase"
+rankprofile[].fef.property[].value "value(0)"
+rankprofile[].fef.property[].name "vespa.hitcollector.heapsize"
+rankprofile[].fef.property[].value "0"
+rankprofile[].fef.property[].name "vespa.hitcollector.arraysize"
+rankprofile[].fef.property[].value "0"
+rankprofile[].fef.property[].name "vespa.dump.ignoredefaultfeatures"
+rankprofile[].fef.property[].value "true"
+rankprofile[].fef.property[].name "vespa.type.query.myTensor"
+rankprofile[].fef.property[].value "tensor<float>(key{})"
+rankprofile[].name "parent"
+rankprofile[].fef.property[].name "rankingExpression(mySlice@77dee0712164ce73).rankingScript"
+rankprofile[].fef.property[].value "query(myTensor){key:MY_KEY2}"
+rankprofile[].fef.property[].name "rankingExpression(myFunction).rankingScript"
+rankprofile[].fef.property[].value "4 * query(myTensor){key:MY_KEY1} * rankingExpression(mySlice@77dee0712164ce73)"
+rankprofile[].fef.property[].name "rankingExpression(myValue).rankingScript"
+rankprofile[].fef.property[].value "4"
+rankprofile[].fef.property[].name "rankingExpression(mySlice).rankingScript"
+rankprofile[].fef.property[].value "myTensor{key:MY_KEY2}"
+rankprofile[].fef.property[].name "vespa.type.query.myTensor"
+rankprofile[].fef.property[].value "tensor<float>(key{})"
diff --git a/config-model/src/test/derived/slice/test.sd b/config-model/src/test/derived/slice/test.sd
index fbb581d1b1d..c2060300785 100644
--- a/config-model/src/test/derived/slice/test.sd
+++ b/config-model/src/test/derived/slice/test.sd
@@ -5,8 +5,8 @@ search test {
 
     rank-profile parent {
 
-        function inline cpmScore() {
-            expression: myValue * mySlice(query(myTensor))
+        function inline myFunction() {
+            expression: myValue * query(myTensor){MY_KEY1} * mySlice(query(myTensor))
         }
 
         function inline myValue() {
@@ -14,7 +14,9 @@ search test {
         }
 
         function inline mySlice(myTensor) {
-            expression: myTensor{"NULL"}
+            # TODO: We are missing type resolving across function calls in serialization,
+            #       so using the short form (without 'key') here will fail
+            expression: myTensor{key:MY_KEY2}
         }
     }
 
diff --git a/container-search/src/main/java/com/yahoo/prelude/fastsearch/DocsumDefinitionSet.java b/container-search/src/main/java/com/yahoo/prelude/fastsearch/DocsumDefinitionSet.java
index df87de2a12b..b3d2e6451f3 100644
--- a/container-search/src/main/java/com/yahoo/prelude/fastsearch/DocsumDefinitionSet.java
+++ b/container-search/src/main/java/com/yahoo/prelude/fastsearch/DocsumDefinitionSet.java
@@ -51,7 +51,7 @@ public final class DocsumDefinitionSet {
         }
         if (ds == null) {
             throw new ConfigurationException("Fetched hit with summary class " + summaryClass +
-                                             ", but this summary class is not in current summary config (" + toString() + ")" +
+                                             ", but this summary class is not in current summary config (" + this + ")" +
                                              " (that is, you asked for something unknown, and no default was found)");
         }
         return ds;
@@ -66,7 +66,7 @@ public final class DocsumDefinitionSet {
      * @return Error message or null on success.
      * @throws ConfigurationException if the summary class of this hit is missing
      */
-    public final String lazyDecode(String summaryClass, byte[] data, FastHit hit) {
+    public String lazyDecode(String summaryClass, byte[] data, FastHit hit) {
         ByteBuffer buffer = ByteBuffer.wrap(data);
         buffer.order(ByteOrder.LITTLE_ENDIAN);
         long docsumClassId = buffer.getInt();
@@ -83,6 +83,7 @@ public final class DocsumDefinitionSet {
         return null;
     }
 
+    @Override
     public String toString() {
         StringBuilder sb = new StringBuilder();
         for (Map.Entry<String, DocsumDefinition> e : definitionsByName.entrySet() ) {
diff --git a/searchlib/abi-spec.json b/searchlib/abi-spec.json
index 2d7daf2300e..5d7e281df87 100644
--- a/searchlib/abi-spec.json
+++ b/searchlib/abi-spec.json
@@ -1611,8 +1611,10 @@
       "public void <init>(java.util.Collection)",
       "public void <init>(java.util.Map)",
       "public void <init>(java.util.Collection, java.util.Map)",
-      "public void <init>(java.util.Collection, java.util.Map, java.util.Map)",
+      "public void <init>(java.util.Collection, java.util.Map, com.yahoo.tensor.evaluation.TypeContext)",
+      "public java.util.Optional typeContext()",
       "public void <init>(java.util.Map, java.util.Map, java.util.Map)",
+      "public void <init>(java.util.Map, java.util.Map, java.util.Optional, java.util.Map)",
       "public void <init>(com.google.common.collect.ImmutableMap, java.util.Map, java.util.Map)",
       "public void addFunctionSerialization(java.lang.String, java.lang.String)",
       "public void addArgumentTypeSerialization(java.lang.String, java.lang.String, com.yahoo.tensor.TensorType)",
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 fe22a5b1267..e770e6ac038 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
@@ -15,7 +15,9 @@ import java.util.List;
  * @author bratseth
  */
 public final class Arguments implements Serializable {
+
     public static final Arguments EMPTY = new Arguments();
+
     private final ImmutableList<ExpressionNode> expressions;
 
     public Arguments() {
@@ -47,9 +49,9 @@ public final class Arguments implements Serializable {
 
     /** Evaluate all arguments in this */
     public Value[] evaluate(Context context) {
-        Value[] values=new Value[expressions.size()];
-        for (int i=0; i<expressions.size(); i++)
-            values[i]=expressions.get(i).evaluate(context);
+        Value[] values = new Value[expressions.size()];
+        for (int i = 0; i < expressions.size(); i++)
+            values[i] = expressions.get(i).evaluate(context);
         return values;
     }
 
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 93b8b8aca5e..8ac1829b16b 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
@@ -42,9 +42,11 @@ public final class ReferenceNode extends CompositeNode {
         return reference.name();
     }
 
+    @Override
     public int hashCode() {
         return reference.hashCode();
     }
+
     /** Returns the arguments, never null */
     public Arguments getArguments() { return reference.arguments(); }
 
@@ -118,7 +120,7 @@ public final class ReferenceNode extends CompositeNode {
             throw new IllegalArgumentException(reference + " is invalid", e);
         }
         if (type == null)
-            throw new IllegalArgumentException("Unknown feature '" + toString() + "'");
+            throw new IllegalArgumentException("Unknown feature '" + this + "'");
         return type;
     }
 
diff --git a/searchlib/src/main/java/com/yahoo/searchlib/rankingexpression/rule/SerializationContext.java b/searchlib/src/main/java/com/yahoo/searchlib/rankingexpression/rule/SerializationContext.java
index 535ad013caf..1f3203f2e35 100644
--- a/searchlib/src/main/java/com/yahoo/searchlib/rankingexpression/rule/SerializationContext.java
+++ b/searchlib/src/main/java/com/yahoo/searchlib/rankingexpression/rule/SerializationContext.java
@@ -4,13 +4,16 @@ package com.yahoo.searchlib.rankingexpression.rule;
 import com.google.common.collect.ImmutableMap;
 import com.yahoo.searchlib.rankingexpression.ExpressionFunction;
 import com.yahoo.searchlib.rankingexpression.RankingExpression;
+import com.yahoo.searchlib.rankingexpression.Reference;
 import com.yahoo.tensor.TensorType;
+import com.yahoo.tensor.evaluation.TypeContext;
 
 import java.util.Collection;
 import java.util.Collections;
 import java.util.HashMap;
 import java.util.LinkedHashMap;
 import java.util.Map;
+import java.util.Optional;
 
 /**
  * Context needed to serialize an expression to a string. This has the lifetime of a single serialization
@@ -22,6 +25,8 @@ public class SerializationContext extends FunctionReferenceContext {
     /** Serialized form of functions indexed by name */
     private final Map<String, String> serializedFunctions;
 
+    private final Optional<TypeContext<Reference>> typeContext;
+
     /** Create a context for a single serialization task */
     public SerializationContext() {
         this(Collections.emptyList());
@@ -29,7 +34,7 @@ public class SerializationContext extends FunctionReferenceContext {
 
     /** Create a context for a single serialization task */
     public SerializationContext(Collection<ExpressionFunction> functions) {
-        this(functions, Collections.emptyMap(), new LinkedHashMap<>());
+        this(functions, Collections.emptyMap(), Optional.empty(), new LinkedHashMap<>());
     }
 
     /** Create a context for a single serialization task */
@@ -39,7 +44,13 @@ public class SerializationContext extends FunctionReferenceContext {
 
     /** Create a context for a single serialization task */
     public SerializationContext(Collection<ExpressionFunction> functions, Map<String, String> bindings) {
-        this(functions, bindings, new LinkedHashMap<>());
+        this(functions, bindings, Optional.empty(), new LinkedHashMap<>());
+    }
+
+    /** Create a context for a single serialization task */
+    public SerializationContext(Collection<ExpressionFunction> functions, Map<String, String> bindings,
+                                TypeContext<Reference> typeContext) {
+        this(functions, bindings, Optional.of(typeContext), new LinkedHashMap<>());
     }
 
     /**
@@ -47,14 +58,19 @@ public class SerializationContext extends FunctionReferenceContext {
      *
      * @param functions the functions of this
      * @param bindings the arguments of this
+     * @param typeContext the type context of this: Serialization may depend on type resolution
      * @param serializedFunctions a cache of serializedFunctions - the ownership of this map
      *        is <b>transferred</b> to this and will be modified in it
      */
-    public SerializationContext(Collection<ExpressionFunction> functions, Map<String, String> bindings,
+    private SerializationContext(Collection<ExpressionFunction> functions, Map<String, String> bindings,
+                                Optional<TypeContext<Reference>> typeContext,
                                 Map<String, String> serializedFunctions) {
-        this(toMap(functions), bindings, serializedFunctions);
+        this(toMap(functions), bindings, typeContext, serializedFunctions);
     }
 
+    /** Returns the type context of this, if it is able to resolve types. */
+    public Optional<TypeContext<Reference>> typeContext() { return typeContext; }
+
     private static Map<String, ExpressionFunction> toMap(Collection<ExpressionFunction> list) {
         Map<String,ExpressionFunction> mapBuilder = new HashMap<>();
         for (ExpressionFunction function : list)
@@ -70,9 +86,16 @@ public class SerializationContext extends FunctionReferenceContext {
      * @param serializedFunctions a cache of serializedFunctions - the ownership of this map
      *        is <b>transferred</b> to this and will be modified in it
      */
+    public SerializationContext(Map<String, ExpressionFunction> functions, Map<String, String> bindings,
+                                Map<String, String> serializedFunctions) {
+        this(functions, bindings, Optional.empty(), serializedFunctions);
+    }
+
     public SerializationContext(Map<String,ExpressionFunction> functions, Map<String, String> bindings,
+                                Optional<TypeContext<Reference>> typeContext,
                                 Map<String, String> serializedFunctions) {
         super(functions, bindings);
+        this.typeContext = typeContext;
         this.serializedFunctions = serializedFunctions;
     }
 
@@ -88,7 +111,7 @@ public class SerializationContext extends FunctionReferenceContext {
         serializedFunctions.put(name, expressionString);
     }
 
-    /** Adds the serialization of the an argument type to a function */
+    /** Adds the serialization of the argument type to a function */
     public void addArgumentTypeSerialization(String functionName, String argumentName, TensorType type) {
         serializedFunctions.put("rankingExpression(" + functionName + ")." + argumentName + ".type", type.toString());
     }
diff --git a/searchlib/src/main/java/com/yahoo/searchlib/rankingexpression/rule/TensorFunctionNode.java b/searchlib/src/main/java/com/yahoo/searchlib/rankingexpression/rule/TensorFunctionNode.java
index d873963bb6e..52d54c9163e 100644
--- a/searchlib/src/main/java/com/yahoo/searchlib/rankingexpression/rule/TensorFunctionNode.java
+++ b/searchlib/src/main/java/com/yahoo/searchlib/rankingexpression/rule/TensorFunctionNode.java
@@ -168,8 +168,8 @@ public class TensorFunctionNode extends CompositeNode {
         }
 
         @Override
-        public String toString(ToStringContext c) {
-            ToStringContext outermost = c;
+        public String toString(ToStringContext<Reference> c) {
+            ToStringContext<Reference> outermost = c;
             while (outermost.parent() != null)
                 outermost = outermost.parent();
 
@@ -251,15 +251,17 @@ public class TensorFunctionNode extends CompositeNode {
         }
 
         @Override
-        public String toString(ToStringContext c) {
-            ToStringContext outermost = c;
+        public String toString(ToStringContext<Reference> c) {
+            ToStringContext<Reference> outermost = c;
             while (outermost.parent() != null)
                 outermost = outermost.parent();
 
             if (outermost instanceof ExpressionToStringContext) {
                 ExpressionToStringContext context = (ExpressionToStringContext)outermost;
                 return expression.toString(new StringBuilder(),
-                                           new ExpressionToStringContext(context.wrappedSerializationContext, c, context.path, context.parent),
+                                           new ExpressionToStringContext(context.wrappedSerializationContext, c,
+                                                                         context.path,
+                                                                         context.parent),
                                            context.path,
                                            context.parent)
                                                    .toString();
@@ -281,9 +283,9 @@ public class TensorFunctionNode extends CompositeNode {
      * to add more context, we need to keep track of both these contexts here separately and map between
      * contexts as seen in the toString methods of the function classes above.
      */
-    private static class ExpressionToStringContext extends SerializationContext implements ToStringContext {
+    private static class ExpressionToStringContext extends SerializationContext implements ToStringContext<Reference> {
 
-        private final ToStringContext wrappedToStringContext;
+        private final ToStringContext<Reference> wrappedToStringContext;
         private final SerializationContext wrappedSerializationContext;
         private final Deque<String> path;
         private final CompositeNode parent;
@@ -297,7 +299,7 @@ public class TensorFunctionNode extends CompositeNode {
         }
 
         ExpressionToStringContext(SerializationContext wrappedSerializationContext,
-                                  ToStringContext wrappedToStringContext,
+                                  ToStringContext<Reference> wrappedToStringContext,
                                   Deque<String> path,
                                   CompositeNode parent) {
             this.wrappedSerializationContext = wrappedSerializationContext;
@@ -328,6 +330,12 @@ public class TensorFunctionNode extends CompositeNode {
         /** Returns a function or null if it isn't defined in this context */
         public ExpressionFunction getFunction(String name) { return wrappedSerializationContext.getFunction(name); }
 
+        /** Returns the type context of this, or empty if none. */
+        @Override
+        public Optional<TypeContext<Reference>> typeContext() {
+            return wrappedSerializationContext.typeContext();
+        }
+
         /** @deprecated Use {@link #getFunctions()} instead */
         @SuppressWarnings("removal")
         @Deprecated(forRemoval = true, since = "7")
@@ -335,9 +343,10 @@ public class TensorFunctionNode extends CompositeNode {
             return ImmutableMap.copyOf(wrappedSerializationContext.getFunctions());
         }
 
-        @Override protected Map<String, ExpressionFunction> getFunctions() { return wrappedSerializationContext.getFunctions(); }
+        @Override
+        protected Map<String, ExpressionFunction> getFunctions() { return wrappedSerializationContext.getFunctions(); }
 
-        public ToStringContext parent() { return wrappedToStringContext; }
+        public ToStringContext<Reference> parent() { return wrappedToStringContext; }
 
         /** Returns the resolution of an identifier, or null if it isn't defined in this context */
         @Override
@@ -361,6 +370,7 @@ public class TensorFunctionNode extends CompositeNode {
             SerializationContext serializationContext = new SerializationContext(getFunctions(), null, serializedFunctions());
             return new ExpressionToStringContext(serializationContext, null, path, parent);
         }
+
     }
 
     /** Turns an EvaluationContext into a Context */
diff --git a/vespajlib/abi-spec.json b/vespajlib/abi-spec.json
index 71e6c0f28f4..a30ee055538 100644
--- a/vespajlib/abi-spec.json
+++ b/vespajlib/abi-spec.json
@@ -2658,8 +2658,7 @@
       "public java.util.Optional dimension()",
       "public java.util.Optional label()",
       "public java.util.Optional index()",
-      "public java.lang.String toString()",
-      "public java.lang.String toString(com.yahoo.tensor.functions.ToStringContext)"
+      "public java.lang.String toString()"
     ],
     "fields": []
   },
@@ -2744,6 +2743,7 @@
     "methods": [
       "public static com.yahoo.tensor.functions.ToStringContext empty()",
       "public abstract java.lang.String getBinding(java.lang.String)",
+      "public java.util.Optional typeContext()",
       "public abstract com.yahoo.tensor.functions.ToStringContext parent()"
     ],
     "fields": []
diff --git a/vespajlib/src/main/java/com/yahoo/tensor/TypeResolver.java b/vespajlib/src/main/java/com/yahoo/tensor/TypeResolver.java
index 457cfcbfa5f..3b12b6bdba1 100644
--- a/vespajlib/src/main/java/com/yahoo/tensor/TypeResolver.java
+++ b/vespajlib/src/main/java/com/yahoo/tensor/TypeResolver.java
@@ -57,7 +57,7 @@ public class TypeResolver {
 
     static public TensorType peek(TensorType inputType, List<String> peekDimensions) {
         if (peekDimensions.isEmpty()) {
-            throw new IllegalArgumentException("peeking no dimensions makes no sense");
+            throw new IllegalArgumentException("Peeking no dimensions makes no sense");
         }
         Map<String, Dimension> map = new HashMap<>();
         for (Dimension dim : inputType.dimensions()) {
@@ -67,7 +67,7 @@ public class TypeResolver {
             if (map.containsKey(name)) {
                 map.remove(name);
             } else {
-                throw new IllegalArgumentException("peeking non-existing dimension "+name+" in type "+inputType);
+                throw new IllegalArgumentException("Peeking non-existing dimension '" + name + "'");
             }
         }
         if (map.isEmpty()) {
@@ -79,10 +79,10 @@ public class TypeResolver {
 
     static public TensorType rename(TensorType inputType, List<String> from, List<String> to) {
         if (from.isEmpty()) {
-            throw new IllegalArgumentException("renaming no dimensions");
+            throw new IllegalArgumentException("Renaming no dimensions");
         }
         if (from.size() != to.size()) {
-            throw new IllegalArgumentException("bad rename, from size "+from.size()+" != to.size "+to.size());
+            throw new IllegalArgumentException("Bad rename, from size "+from.size()+" != to.size "+to.size());
         }
         Map<String,Dimension> oldDims = new HashMap<>();
         for (Dimension dim : inputType.dimensions()) {
@@ -96,7 +96,7 @@ public class TypeResolver {
                 var dim = oldDims.remove(oldName);
                 newDims.put(newName, dim.withName(newName));
             } else {
-                logger.log(Level.WARNING, "renaming non-existing dimension "+oldName+" in type "+inputType);
+                logger.log(Level.WARNING, "Renaming non-existing dimension "+oldName+" in type "+inputType);
                 // throw new IllegalArgumentException("bad rename, dimension  "+oldName+" not found");
             }
         }
@@ -106,13 +106,13 @@ public class TypeResolver {
         if (inputType.dimensions().size() == newDims.size()) {
             return new TensorType(inputType.valueType(), newDims.values());
         } else {
-            throw new IllegalArgumentException("bad rename, lost some dimenions");
+            throw new IllegalArgumentException("Bad rename, lost some dimensions");
         }
     }
 
     static public TensorType cell_cast(TensorType inputType, Value toCellType) {
         if (toCellType != Value.DOUBLE && inputType.dimensions().isEmpty()) {
-            throw new IllegalArgumentException("cannot cast "+inputType+" to valueType"+toCellType);
+            throw new IllegalArgumentException("Cannot cast "+inputType+" to valueType"+toCellType);
         }
         return new TensorType(toCellType, inputType.dimensions());
     }
@@ -188,7 +188,7 @@ public class TypeResolver {
         if (allOk) {
             return join(lhs, rhs);
         } else {
-            throw new IllegalArgumentException("types in merge() dimensions mismatch: "+lhs+" != "+rhs);                
+            throw new IllegalArgumentException("Types in merge() dimensions mismatch: "+lhs+" != "+rhs);
         }
     }
 
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 a376536015a..dbc8396d701 100644
--- a/vespajlib/src/main/java/com/yahoo/tensor/evaluation/VariableTensor.java
+++ b/vespajlib/src/main/java/com/yahoo/tensor/evaluation/VariableTensor.java
@@ -58,7 +58,7 @@ public class VariableTensor<NAMETYPE extends Name> extends PrimitiveTensorFuncti
     }
 
     @Override
-    public String toString(ToStringContext context) {
+    public String toString(ToStringContext<NAMETYPE> context) {
         return name;
     }
 
diff --git a/vespajlib/src/main/java/com/yahoo/tensor/functions/Argmax.java b/vespajlib/src/main/java/com/yahoo/tensor/functions/Argmax.java
index 16ca7104f8d..55dd8a7bc8a 100644
--- a/vespajlib/src/main/java/com/yahoo/tensor/functions/Argmax.java
+++ b/vespajlib/src/main/java/com/yahoo/tensor/functions/Argmax.java
@@ -48,7 +48,7 @@ public class Argmax<NAMETYPE extends Name> extends CompositeTensorFunction<NAMET
     }
 
     @Override
-    public String toString(ToStringContext context) {
+    public String toString(ToStringContext<NAMETYPE> context) {
         return "argmax(" + argument.toString(context) + Reduce.commaSeparated(dimensions) + ")";
     }
 
diff --git a/vespajlib/src/main/java/com/yahoo/tensor/functions/Argmin.java b/vespajlib/src/main/java/com/yahoo/tensor/functions/Argmin.java
index fcdc1233550..f1f0b9d67b0 100644
--- a/vespajlib/src/main/java/com/yahoo/tensor/functions/Argmin.java
+++ b/vespajlib/src/main/java/com/yahoo/tensor/functions/Argmin.java
@@ -48,7 +48,7 @@ public class Argmin<NAMETYPE extends Name> extends CompositeTensorFunction<NAMET
     }
 
     @Override
-    public String toString(ToStringContext context) {
+    public String toString(ToStringContext<NAMETYPE> context) {
         return "argmin(" + argument.toString(context) + Reduce.commaSeparated(dimensions) + ")";
     }
 
diff --git a/vespajlib/src/main/java/com/yahoo/tensor/functions/CellCast.java b/vespajlib/src/main/java/com/yahoo/tensor/functions/CellCast.java
index 8c6c27e171a..09f84e6747e 100644
--- a/vespajlib/src/main/java/com/yahoo/tensor/functions/CellCast.java
+++ b/vespajlib/src/main/java/com/yahoo/tensor/functions/CellCast.java
@@ -107,7 +107,7 @@ public class CellCast<NAMETYPE extends Name> extends PrimitiveTensorFunction<NAM
     }
 
     @Override
-    public String toString(ToStringContext context) {
+    public String toString(ToStringContext<NAMETYPE> context) {
         return "cell_cast(" + argument.toString(context) + ", " + valueType + ")";
     }
 
diff --git a/vespajlib/src/main/java/com/yahoo/tensor/functions/Concat.java b/vespajlib/src/main/java/com/yahoo/tensor/functions/Concat.java
index 32a4c8cd2ff..6d4b15be991 100644
--- a/vespajlib/src/main/java/com/yahoo/tensor/functions/Concat.java
+++ b/vespajlib/src/main/java/com/yahoo/tensor/functions/Concat.java
@@ -285,7 +285,7 @@ public class Concat<NAMETYPE extends Name> extends PrimitiveTensorFunction<NAMET
     }
 
     @Override
-    public String toString(ToStringContext context) {
+    public String toString(ToStringContext<NAMETYPE> context) {
         return "concat(" + argumentA.toString(context) + ", " + argumentB.toString(context) + ", " + dimension + ")";
     }
 
diff --git a/vespajlib/src/main/java/com/yahoo/tensor/functions/ConstantTensor.java b/vespajlib/src/main/java/com/yahoo/tensor/functions/ConstantTensor.java
index 1544369ba2f..a0fd9272f54 100644
--- a/vespajlib/src/main/java/com/yahoo/tensor/functions/ConstantTensor.java
+++ b/vespajlib/src/main/java/com/yahoo/tensor/functions/ConstantTensor.java
@@ -47,6 +47,6 @@ public class ConstantTensor<NAMETYPE extends Name> extends PrimitiveTensorFuncti
     public Tensor evaluate(EvaluationContext<NAMETYPE> context) { return constant; }
 
     @Override
-    public String toString(ToStringContext context) { return constant.toString(); }
+    public String toString(ToStringContext<NAMETYPE> context) { return constant.toString(); }
 
 }
diff --git a/vespajlib/src/main/java/com/yahoo/tensor/functions/Diag.java b/vespajlib/src/main/java/com/yahoo/tensor/functions/Diag.java
index 2c0fa483021..92d89ec68f7 100644
--- a/vespajlib/src/main/java/com/yahoo/tensor/functions/Diag.java
+++ b/vespajlib/src/main/java/com/yahoo/tensor/functions/Diag.java
@@ -41,7 +41,7 @@ public class Diag<NAMETYPE extends Name> extends CompositeTensorFunction<NAMETYP
     }
 
     @Override
-    public String toString(ToStringContext context) {
+    public String toString(ToStringContext<NAMETYPE> context) {
         return "diag(" + dimensionNames().collect(Collectors.joining(",")) + ")" + diagFunction;
     }
 
diff --git a/vespajlib/src/main/java/com/yahoo/tensor/functions/DynamicTensor.java b/vespajlib/src/main/java/com/yahoo/tensor/functions/DynamicTensor.java
index 97126ad88a7..46992115c23 100644
--- a/vespajlib/src/main/java/com/yahoo/tensor/functions/DynamicTensor.java
+++ b/vespajlib/src/main/java/com/yahoo/tensor/functions/DynamicTensor.java
@@ -46,11 +46,11 @@ public abstract class DynamicTensor<NAMETYPE extends Name> extends PrimitiveTens
     TensorType type() { return type; }
 
     @Override
-    public String toString(ToStringContext context) {
+    public String toString(ToStringContext<NAMETYPE> context) {
         return type().toString() + ":" + contentToString(context);
     }
 
-    abstract String contentToString(ToStringContext context);
+    abstract String contentToString(ToStringContext<NAMETYPE> context);
 
     /** Creates a dynamic tensor function. The cell addresses must match the type. */
     public static <NAMETYPE extends Name> DynamicTensor<NAMETYPE> from(TensorType type, Map<TensorAddress, ScalarFunction<NAMETYPE>> cells) {
@@ -80,7 +80,7 @@ public abstract class DynamicTensor<NAMETYPE extends Name> extends PrimitiveTens
         }
 
         @Override
-        String contentToString(ToStringContext context) {
+        String contentToString(ToStringContext<NAMETYPE> context) {
             if (type().dimensions().isEmpty()) {
                 if (cells.isEmpty()) return "{}";
                 return "{" + cells.values().iterator().next().toString(context) + "}";
@@ -121,7 +121,7 @@ public abstract class DynamicTensor<NAMETYPE extends Name> extends PrimitiveTens
         }
 
         @Override
-        String contentToString(ToStringContext context) {
+        String contentToString(ToStringContext<NAMETYPE> context) {
             if (type().dimensions().isEmpty()) {
                 if (cells.isEmpty()) return "{}";
                 return "{" + cells.get(0).toString(context) + "}";
diff --git a/vespajlib/src/main/java/com/yahoo/tensor/functions/Expand.java b/vespajlib/src/main/java/com/yahoo/tensor/functions/Expand.java
index 8fc246a7d9d..c049e5d41da 100644
--- a/vespajlib/src/main/java/com/yahoo/tensor/functions/Expand.java
+++ b/vespajlib/src/main/java/com/yahoo/tensor/functions/Expand.java
@@ -41,7 +41,7 @@ public class Expand<NAMETYPE extends Name> extends CompositeTensorFunction<NAMET
     }
 
     @Override
-    public String toString(ToStringContext context) {
+    public String toString(ToStringContext<NAMETYPE> context) {
         return "expand(" + argument.toString(context) + ", " + dimensionName + ")";
     }
 
diff --git a/vespajlib/src/main/java/com/yahoo/tensor/functions/Generate.java b/vespajlib/src/main/java/com/yahoo/tensor/functions/Generate.java
index 89e981df49e..54e83fa472f 100644
--- a/vespajlib/src/main/java/com/yahoo/tensor/functions/Generate.java
+++ b/vespajlib/src/main/java/com/yahoo/tensor/functions/Generate.java
@@ -117,9 +117,9 @@ public class Generate<NAMETYPE extends Name> extends PrimitiveTensorFunction<NAM
     }
 
     @Override
-    public String toString(ToStringContext context) { return type + "(" + generatorToString(context) + ")"; }
+    public String toString(ToStringContext<NAMETYPE> context) { return type + "(" + generatorToString(context) + ")"; }
 
-    private String generatorToString(ToStringContext context) {
+    private String generatorToString(ToStringContext<NAMETYPE> context) {
         if (freeGenerator != null)
             return freeGenerator.toString();
         else
@@ -183,11 +183,11 @@ public class Generate<NAMETYPE extends Name> extends PrimitiveTensorFunction<NAM
     }
 
     /** A context which adds the bindings of the generate dimension names to the given context. */
-    private class GenerateToStringContext implements ToStringContext {
+    private class GenerateToStringContext implements ToStringContext<NAMETYPE> {
 
-        private final ToStringContext context;
+        private final ToStringContext<NAMETYPE> context;
 
-        public GenerateToStringContext(ToStringContext context) {
+        public GenerateToStringContext(ToStringContext<NAMETYPE> context) {
             this.context = context;
         }
 
@@ -200,7 +200,7 @@ public class Generate<NAMETYPE extends Name> extends PrimitiveTensorFunction<NAM
         }
 
         @Override
-        public ToStringContext parent() { return context; }
+        public ToStringContext<NAMETYPE> parent() { return context; }
 
     }
 
diff --git a/vespajlib/src/main/java/com/yahoo/tensor/functions/Join.java b/vespajlib/src/main/java/com/yahoo/tensor/functions/Join.java
index 0d4aeb5c37d..52bef482fb4 100644
--- a/vespajlib/src/main/java/com/yahoo/tensor/functions/Join.java
+++ b/vespajlib/src/main/java/com/yahoo/tensor/functions/Join.java
@@ -75,7 +75,7 @@ public class Join<NAMETYPE extends Name> extends PrimitiveTensorFunction<NAMETYP
     }
 
     @Override
-    public String toString(ToStringContext context) {
+    public String toString(ToStringContext<NAMETYPE> context) {
         return "join(" + argumentA.toString(context) + ", " + argumentB.toString(context) + ", " + combinator + ")";
     }
 
diff --git a/vespajlib/src/main/java/com/yahoo/tensor/functions/L1Normalize.java b/vespajlib/src/main/java/com/yahoo/tensor/functions/L1Normalize.java
index 903d0b2dcd9..f47202d1b9f 100644
--- a/vespajlib/src/main/java/com/yahoo/tensor/functions/L1Normalize.java
+++ b/vespajlib/src/main/java/com/yahoo/tensor/functions/L1Normalize.java
@@ -39,7 +39,7 @@ public class L1Normalize<NAMETYPE extends Name> extends CompositeTensorFunction<
     }
 
     @Override
-    public String toString(ToStringContext context) {
+    public String toString(ToStringContext<NAMETYPE> context) {
         return "l1_normalize(" + argument.toString(context) + ", " + dimension + ")";
     }
 
diff --git a/vespajlib/src/main/java/com/yahoo/tensor/functions/L2Normalize.java b/vespajlib/src/main/java/com/yahoo/tensor/functions/L2Normalize.java
index c862aa4eaf6..8f4e2f466d4 100644
--- a/vespajlib/src/main/java/com/yahoo/tensor/functions/L2Normalize.java
+++ b/vespajlib/src/main/java/com/yahoo/tensor/functions/L2Normalize.java
@@ -41,7 +41,7 @@ public class L2Normalize<NAMETYPE extends Name> extends CompositeTensorFunction<
     }
 
     @Override
-    public String toString(ToStringContext context) {
+    public String toString(ToStringContext<NAMETYPE> context) {
         return "l2_normalize(" + argument.toString(context) + ", " + dimension + ")";
     }
 
diff --git a/vespajlib/src/main/java/com/yahoo/tensor/functions/Map.java b/vespajlib/src/main/java/com/yahoo/tensor/functions/Map.java
index 40620cb95fe..46772d8cbff 100644
--- a/vespajlib/src/main/java/com/yahoo/tensor/functions/Map.java
+++ b/vespajlib/src/main/java/com/yahoo/tensor/functions/Map.java
@@ -71,7 +71,7 @@ public class Map<NAMETYPE extends Name> extends PrimitiveTensorFunction<NAMETYPE
     }
 
     @Override
-    public String toString(ToStringContext context) {
+    public String toString(ToStringContext<NAMETYPE> context) {
         return "map(" + argument.toString(context) + ", " + mapper + ")";
     }
 
diff --git a/vespajlib/src/main/java/com/yahoo/tensor/functions/Matmul.java b/vespajlib/src/main/java/com/yahoo/tensor/functions/Matmul.java
index 810e01011fe..8ac6d711c48 100644
--- a/vespajlib/src/main/java/com/yahoo/tensor/functions/Matmul.java
+++ b/vespajlib/src/main/java/com/yahoo/tensor/functions/Matmul.java
@@ -45,7 +45,7 @@ public class Matmul<NAMETYPE extends Name> extends CompositeTensorFunction<NAMET
     }
 
     @Override
-    public String toString(ToStringContext context) {
+    public String toString(ToStringContext<NAMETYPE> context) {
         return "matmul(" + argument1.toString(context) + ", " + argument2.toString(context) + ", " + dimension + ")";
     }
 
diff --git a/vespajlib/src/main/java/com/yahoo/tensor/functions/Merge.java b/vespajlib/src/main/java/com/yahoo/tensor/functions/Merge.java
index bd42e95a59e..adc84225a63 100644
--- a/vespajlib/src/main/java/com/yahoo/tensor/functions/Merge.java
+++ b/vespajlib/src/main/java/com/yahoo/tensor/functions/Merge.java
@@ -70,7 +70,7 @@ public class Merge<NAMETYPE extends Name> extends PrimitiveTensorFunction<NAMETY
     }
 
     @Override
-    public String toString(ToStringContext context) {
+    public String toString(ToStringContext<NAMETYPE> context) {
         return "merge(" + argumentA.toString(context) + ", " + argumentB.toString(context) + ", " + merger + ")";
     }
 
diff --git a/vespajlib/src/main/java/com/yahoo/tensor/functions/Random.java b/vespajlib/src/main/java/com/yahoo/tensor/functions/Random.java
index 8cf1964585a..18c5db8e3a7 100644
--- a/vespajlib/src/main/java/com/yahoo/tensor/functions/Random.java
+++ b/vespajlib/src/main/java/com/yahoo/tensor/functions/Random.java
@@ -38,7 +38,7 @@ public class Random<NAMETYPE extends Name> extends CompositeTensorFunction<NAMET
     }
 
     @Override
-    public String toString(ToStringContext context) {
+    public String toString(ToStringContext<NAMETYPE> context) {
         return "random(" + dimensionNames().collect(Collectors.joining(",")) + ")";
     }
 
diff --git a/vespajlib/src/main/java/com/yahoo/tensor/functions/Range.java b/vespajlib/src/main/java/com/yahoo/tensor/functions/Range.java
index 7d5b11d6672..45b827db900 100644
--- a/vespajlib/src/main/java/com/yahoo/tensor/functions/Range.java
+++ b/vespajlib/src/main/java/com/yahoo/tensor/functions/Range.java
@@ -42,7 +42,7 @@ public class Range<NAMETYPE extends Name> extends CompositeTensorFunction<NAMETY
     }
 
     @Override
-    public String toString(ToStringContext context) {
+    public String toString(ToStringContext<NAMETYPE> context) {
         return "range(" + dimensionNames().collect(Collectors.joining(",")) + ")" + rangeFunction;
     }
 
diff --git a/vespajlib/src/main/java/com/yahoo/tensor/functions/Reduce.java b/vespajlib/src/main/java/com/yahoo/tensor/functions/Reduce.java
index 79209fd8f09..8841cff15e9 100644
--- a/vespajlib/src/main/java/com/yahoo/tensor/functions/Reduce.java
+++ b/vespajlib/src/main/java/com/yahoo/tensor/functions/Reduce.java
@@ -86,7 +86,7 @@ public class Reduce<NAMETYPE extends Name> extends PrimitiveTensorFunction<NAMET
     }
 
     @Override
-    public String toString(ToStringContext context) {
+    public String toString(ToStringContext<NAMETYPE> context) {
         return "reduce(" + argument.toString(context) + ", " + aggregator + commaSeparated(dimensions) + ")";
     }
 
diff --git a/vespajlib/src/main/java/com/yahoo/tensor/functions/ReduceJoin.java b/vespajlib/src/main/java/com/yahoo/tensor/functions/ReduceJoin.java
index 9b56fefb5f0..7505355beed 100644
--- a/vespajlib/src/main/java/com/yahoo/tensor/functions/ReduceJoin.java
+++ b/vespajlib/src/main/java/com/yahoo/tensor/functions/ReduceJoin.java
@@ -314,7 +314,7 @@ public class ReduceJoin<NAMETYPE extends Name> extends CompositeTensorFunction<N
     }
 
     @Override
-    public String toString(ToStringContext context) {
+    public String toString(ToStringContext<NAMETYPE> context) {
         return "reduce_join(" + argumentA.toString(context) + ", " +
                                 argumentB.toString(context) + ", " +
                                 combinator + ", " +
@@ -324,8 +324,8 @@ public class ReduceJoin<NAMETYPE extends Name> extends CompositeTensorFunction<N
 
     private static class MultiDimensionIterator {
 
-        private long[] bounds;
-        private long[] iterator;
+        private final long[] bounds;
+        private final long[] iterator;
         private int remaining;
 
         MultiDimensionIterator(TensorType type) {
@@ -364,9 +364,11 @@ public class ReduceJoin<NAMETYPE extends Name> extends CompositeTensorFunction<N
             remaining -= 1;
         }
 
+        @Override
         public String toString() {
             return Arrays.toString(iterator);
         }
+
     }
 
 }
diff --git a/vespajlib/src/main/java/com/yahoo/tensor/functions/Rename.java b/vespajlib/src/main/java/com/yahoo/tensor/functions/Rename.java
index 67ede7f6540..a434ecba5cc 100644
--- a/vespajlib/src/main/java/com/yahoo/tensor/functions/Rename.java
+++ b/vespajlib/src/main/java/com/yahoo/tensor/functions/Rename.java
@@ -128,7 +128,7 @@ public class Rename<NAMETYPE extends Name> extends PrimitiveTensorFunction<NAMET
     }
 
     @Override
-    public String toString(ToStringContext context) {
+    public String toString(ToStringContext<NAMETYPE> context) {
         return "rename(" + argument.toString(context) + ", " +
                        toVectorString(fromDimensions) + ", " + toVectorString(toDimensions) + ")";
     }
diff --git a/vespajlib/src/main/java/com/yahoo/tensor/functions/ScalarFunction.java b/vespajlib/src/main/java/com/yahoo/tensor/functions/ScalarFunction.java
index 11e52aad73e..0e0dc9a9aa8 100644
--- a/vespajlib/src/main/java/com/yahoo/tensor/functions/ScalarFunction.java
+++ b/vespajlib/src/main/java/com/yahoo/tensor/functions/ScalarFunction.java
@@ -20,6 +20,6 @@ public interface ScalarFunction<NAMETYPE extends Name> extends Function<Evaluati
     /** Returns this as a tensor function, or empty if it cannot be represented as a tensor function */
     default Optional<TensorFunction<NAMETYPE>> asTensorFunction() { return Optional.empty(); }
 
-    default String toString(ToStringContext context) { return toString(); }
+    default String toString(ToStringContext<NAMETYPE> context) { return toString(); }
 
 }
diff --git a/vespajlib/src/main/java/com/yahoo/tensor/functions/Slice.java b/vespajlib/src/main/java/com/yahoo/tensor/functions/Slice.java
index 09bfb8b996b..da7581c39f9 100644
--- a/vespajlib/src/main/java/com/yahoo/tensor/functions/Slice.java
+++ b/vespajlib/src/main/java/com/yahoo/tensor/functions/Slice.java
@@ -121,8 +121,8 @@ public class Slice<NAMETYPE extends Name> extends PrimitiveTensorFunction<NAMETY
 
     private TensorType resultType(TensorType argumentType) {
         List<String> peekDimensions;
-        // Special case where a single indexed or mapped dimension is sliced
         if (subspaceAddress.size() == 1 && subspaceAddress.get(0).dimension().isEmpty()) {
+            // Special case where a single indexed or mapped dimension is sliced
             if (subspaceAddress.get(0).index().isPresent()) {
                 peekDimensions = findDimensions(argumentType.dimensions(), TensorType.Dimension::isIndexed);
                 if (peekDimensions.size() > 1) {
@@ -140,22 +140,28 @@ public class Slice<NAMETYPE extends Name> extends PrimitiveTensorFunction<NAMETY
         else { // general slicing
             peekDimensions = subspaceAddress.stream().map(d -> d.dimension().get()).collect(Collectors.toList());
         }
-        if (peekDimensions.isEmpty())
-            throw new IllegalArgumentException(this + " cannot slice " + argumentType + ": No dimensions to slice");
-        return TypeResolver.peek(argumentType, peekDimensions);
+        try {
+            return TypeResolver.peek(argumentType, peekDimensions);
+        }
+        catch (IllegalArgumentException e) {
+            throw new IllegalArgumentException(this + " cannot slice type " + argumentType, e);
+        }
     }
 
     @Override
-    public String toString(ToStringContext context) {
+    public String toString(ToStringContext<NAMETYPE> context) {
         StringBuilder b = new StringBuilder(argument.toString(context));
-        if (subspaceAddress.size() == 1 && subspaceAddress.get(0).dimension().isEmpty()) {
+        if (context.typeContext().isEmpty()
+            && subspaceAddress.size() == 1 && subspaceAddress.get(0).dimension().isEmpty()) { // use short forms
             if (subspaceAddress.get(0).index().isPresent())
                 b.append("[").append(subspaceAddress.get(0).index().get().toString(context)).append("]");
             else
                 b.append("{").append(subspaceAddress.get(0).label().get()).append("}");
         }
-        else {
-            b.append("{").append(subspaceAddress.stream().map(i -> i.toString(context)).collect(Collectors.joining(", "))).append("}");
+        else { // general form
+            b.append("{").append(subspaceAddress.stream()
+                                                .map(i -> i.toString(context, this))
+                                                .collect(Collectors.joining(", "))).append("}");
         }
         return b.toString();
     }
@@ -222,12 +228,22 @@ public class Slice<NAMETYPE extends Name> extends PrimitiveTensorFunction<NAMETY
 
         @Override
         public String toString() {
-            return toString(ToStringContext.empty());
+            return toString(null, null);
         }
 
-        public String toString(ToStringContext context) {
+        String toString(ToStringContext<NAMETYPE> context, Slice<NAMETYPE> owner) {
             StringBuilder b = new StringBuilder();
-            dimension.ifPresent(d -> b.append(d).append(":"));
+            Optional<String> dimensionName = dimension;
+            if (context != null && dimensionName.isEmpty()) { // This isn't just toString(): Output canonical form or fail
+                TensorType type = context.typeContext().isPresent() ? owner.argument.type(context.typeContext().get()) : null;
+                if (type == null || type.dimensions().size() != 1)
+                    throw new IllegalArgumentException("The tensor dimension name being sliced by " + owner +
+                                                       " cannot be uniquely resolved. Use the full form " +
+                                                       "slice{myDimensionName: ...");
+                else
+                    dimensionName = Optional.of(type.dimensions().get(0).name());
+            }
+            dimensionName.ifPresent(d -> b.append(d).append(":"));
             if (label != null)
                 b.append(label);
             else
diff --git a/vespajlib/src/main/java/com/yahoo/tensor/functions/Softmax.java b/vespajlib/src/main/java/com/yahoo/tensor/functions/Softmax.java
index 13420a12e8f..9ea9040831b 100644
--- a/vespajlib/src/main/java/com/yahoo/tensor/functions/Softmax.java
+++ b/vespajlib/src/main/java/com/yahoo/tensor/functions/Softmax.java
@@ -46,7 +46,7 @@ public class Softmax<NAMETYPE extends Name> extends CompositeTensorFunction<NAME
     }
 
     @Override
-    public String toString(ToStringContext context) {
+    public String toString(ToStringContext<NAMETYPE> context) {
         return "softmax(" + argument.toString(context) + ", " + dimension + ")";
     }
 
diff --git a/vespajlib/src/main/java/com/yahoo/tensor/functions/TensorFunction.java b/vespajlib/src/main/java/com/yahoo/tensor/functions/TensorFunction.java
index 81d3692bd94..1e1d1d3b5b9 100644
--- a/vespajlib/src/main/java/com/yahoo/tensor/functions/TensorFunction.java
+++ b/vespajlib/src/main/java/com/yahoo/tensor/functions/TensorFunction.java
@@ -60,7 +60,7 @@ public abstract class TensorFunction<NAMETYPE extends Name> {
      *
      * @param context a context which must be passed to all nested functions when requesting the string value
      */
-    public abstract String toString(ToStringContext context);
+    public abstract String toString(ToStringContext<NAMETYPE> context);
 
     /** Returns this as a scalar function, or empty if it cannot be represented as a scalar function */
     public Optional<ScalarFunction<NAMETYPE>> asScalarFunction() { return Optional.empty(); }
diff --git a/vespajlib/src/main/java/com/yahoo/tensor/functions/ToStringContext.java b/vespajlib/src/main/java/com/yahoo/tensor/functions/ToStringContext.java
index 1c8da9a1dca..233779fcebe 100644
--- a/vespajlib/src/main/java/com/yahoo/tensor/functions/ToStringContext.java
+++ b/vespajlib/src/main/java/com/yahoo/tensor/functions/ToStringContext.java
@@ -1,31 +1,42 @@
 // Copyright Yahoo. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
 package com.yahoo.tensor.functions;
 
+import com.yahoo.tensor.evaluation.Name;
+import com.yahoo.tensor.evaluation.TypeContext;
+
+import java.util.Optional;
+
 /**
  * A context which is passed down to all nested functions when returning a string representation.
  *
  * @author bratseth
  */
-public interface ToStringContext {
+public interface ToStringContext<NAMETYPE extends Name> {
 
-    static ToStringContext empty() { return new EmptyStringContext(); }
+    static <NAMETYPE extends Name> ToStringContext<NAMETYPE> empty() { return new EmptyStringContext<NAMETYPE>(); }
 
     /** Returns the name an identifier is bound to, or null if not bound in this context */
     String getBinding(String name);
 
     /**
+     * Returns the context used to resolve types in this, if present.
+     * In some functions serialization depends on type information.
+     */
+    default Optional<TypeContext<NAMETYPE>> typeContext() { return Optional.empty(); }
+
+    /**
      * Returns the parent context of this (the context we're in scope of when this is created),
      * or null if this is the root.
      */
-    ToStringContext parent();
+    ToStringContext<NAMETYPE> parent();
 
-    class EmptyStringContext implements ToStringContext {
+    class EmptyStringContext<NAMETYPE extends Name> implements ToStringContext<NAMETYPE> {
 
         @Override
         public String getBinding(String name) { return null; }
 
         @Override
-        public ToStringContext parent() { return null; }
+        public ToStringContext<NAMETYPE> parent() { return null; }
 
     }
 
diff --git a/vespajlib/src/main/java/com/yahoo/tensor/functions/XwPlusB.java b/vespajlib/src/main/java/com/yahoo/tensor/functions/XwPlusB.java
index 112a0d43796..0223ad4d588 100644
--- a/vespajlib/src/main/java/com/yahoo/tensor/functions/XwPlusB.java
+++ b/vespajlib/src/main/java/com/yahoo/tensor/functions/XwPlusB.java
@@ -44,7 +44,7 @@ public class XwPlusB<NAMETYPE extends Name> extends CompositeTensorFunction<NAME
     }
 
     @Override
-    public String toString(ToStringContext context) {
+    public String toString(ToStringContext<NAMETYPE> context) {
         return "xw_plus_b(" + x.toString(context) + ", " +
                w.toString(context) + ", " +
                b.toString(context) + ", " +