better tensor lambda type errors

- report actual return type when not double
- import type errors from lambda function type resolving

2 files changed, 16 insertions, 6 deletions

diff --git a/eval/src/tests/eval/node_types/node_types_test.cpp b/eval/src/tests/eval/node_types/node_types_test.cpp
index cabae6307eb..8eaa7a80a81 100644
--- a/eval/src/tests/eval/node_types/node_types_test.cpp
+++ b/eval/src/tests/eval/node_types/node_types_test.cpp
@@ -223,7 +223,7 @@ TEST("require that merge resolves to the appropriate type") {
     TEST_DO(verify(strfmt(pattern, "tensor<float>(x[5])", "double"), "error"));
 }
 
-TEST("require that lambda tensor resolves correct type") {
+TEST("require that static tensor lambda resolves correct type") {
     TEST_DO(verify("tensor(x[5])(1.0)", "tensor(x[5])"));
     TEST_DO(verify("tensor(x[5],y[10])(1.0)", "tensor(x[5],y[10])"));
     TEST_DO(verify("tensor(x[5],y[10],z[15])(1.0)", "tensor(x[5],y[10],z[15])"));
@@ -242,11 +242,12 @@ TEST("require that tensor create resolves correct type") {
     TEST_DO(verify("tensor(x[3]):{{x:0}:double,{x:1}:error,{x:2}:double}", "error"));
 }
 
-TEST("require that tensor lambda resolves correct type") {
+TEST("require that dynamic tensor lambda resolves correct type") {
     TEST_DO(verify("tensor(x[3])(error)", "error"));
     TEST_DO(verify("tensor(x[3])(double)", "tensor(x[3])"));
     TEST_DO(verify("tensor<float>(x[3])(double)", "tensor<float>(x[3])"));
     TEST_DO(verify("tensor(x[3])(tensor(x[2]))", "error"));
+    TEST_DO(verify("tensor(x[3])(reduce(tensor(x[2])+tensor(x[4]),sum))", "error"));
 }
 
 TEST("require that tensor peek resolves correct type") {
diff --git a/eval/src/vespa/eval/eval/node_types.cpp b/eval/src/vespa/eval/eval/node_types.cpp
index 924de97c470..5fe441b7a4e 100644
--- a/eval/src/vespa/eval/eval/node_types.cpp
+++ b/eval/src/vespa/eval/eval/node_types.cpp
@@ -83,7 +83,13 @@ struct TypeResolver : public NodeVisitor, public NodeTraverser {
         return state.type(node);
     }
 
-    void import(const NodeTypes &types) {
+    void import_errors(const NodeTypes &types) {
+        for (const auto &err: types.errors()) {
+            state.add_error(fmt("[lambda]: %s", err.c_str()));
+        }
+    }
+
+    void import_types(const NodeTypes &types) {
         types.each([&](const Node &node, const ValueType &type)
                    {
                        state.bind(type, node);
@@ -189,10 +195,13 @@ struct TypeResolver : public NodeVisitor, public NodeTraverser {
             arg_types.push_back(param_type(binding));
         }
         NodeTypes lambda_types(node.lambda(), arg_types);
-        if (!lambda_types.get_type(node.lambda().root()).is_double()) {
-            return fail(node, "lambda function produces non-double result", false);
+        const ValueType &lambda_type = lambda_types.get_type(node.lambda().root());
+        if (!lambda_type.is_double()) {
+            import_errors(lambda_types);
+            return fail(node, fmt("lambda function has non-double result type: %s",
+                                  lambda_type.to_spec().c_str()), false);
         }
-        import(lambda_types);
+        import_types(lambda_types);
         bind(node.type(), node);
     }
     void visit(const TensorPeek &node) override {