From a1d279e81d4c8c702bfc860adcb38113dcbca679 Mon Sep 17 00:00:00 2001
From: Rich FitzJohn <r.fitzjohn@imperial.ac.uk>
Date: Tue, 15 Oct 2024 07:45:55 +0100
Subject: [PATCH] Fix error thrown while throwing error

---
 R/filter-support.R           | 2 +-
 tests/testthat/test-filter.R | 8 ++++++++
 2 files changed, 9 insertions(+), 1 deletion(-)

diff --git a/R/filter-support.R b/R/filter-support.R
index fc3635c8..7cb7774f 100644
--- a/R/filter-support.R
+++ b/R/filter-support.R
@@ -1,5 +1,5 @@
 check_generator_for_filter <- function(generator, what, call = NULL) {
-  check_is_dust_system_generator(generator)
+  check_is_dust_system_generator(generator, substitute(generator))
   if (!generator$properties$has_compare) {
     cli::cli_abort(
       paste("Can't create {what}; the '{generator$name}' system does",
diff --git a/tests/testthat/test-filter.R b/tests/testthat/test-filter.R
index de0ab29c..b649cfa2 100644
--- a/tests/testthat/test-filter.R
+++ b/tests/testthat/test-filter.R
@@ -649,3 +649,11 @@ test_that("can run continuous-time filter", {
     "Can't use 'dust_filter_create()' with continuous-time models",
     fixed = TRUE)
 })
+
+
+test_that("sensible error when given unevaluated generator", {
+  d <- data.frame(time = c(4, 8, 12, 16), incidence = c(1, 2, 3, 4))
+  expect_error(
+    dust_filter_create(sir, 0, d, 200),
+    "Expected 'generator' to be a 'dust_system_generator' object")
+})