feat: add stop gradient functions, if reset is provided so must stop

.github/workflows/ci.yml

@@ -33,13 +33,14 @@ jobs:
   unit-tests:
     name: ${{ matrix.basename }} - ${{ matrix.os }} - ${{ matrix.llvm[0] }} - ${{ matrix.features }}
     runs-on: ${{ matrix.os }}
-    continue-on-error: ${{ matrix.experimental }}
+    continue-on-error: ${{ matrix.experimental || matrix.llvm[0] != '17.0' }}
     strategy:
         matrix:
           llvm:
             - ["15.0", "15-0", "150"]
             - ["16.0", "16-0", "160"]
             - ["17.0", "17-0", "170"]
+            - ["18.1", "18-1", "181"]
             - ["19.1", "19-1", "191", "19"]
             - ["20.1", "20-1", "201", "20"]
             - ["21.1", "21-1", "211", "21"]
@@ -62,26 +63,6 @@ jobs:
             - Tests
 
           include:
-            - toolchain: stable
-              os: ubuntu-latest
-              llvm: ["18.1", "18-1", "181"]
-              features: "rayon cranelift external_f64"
-              tests: true
-              clippy: false
-              rustdoc: false
-              experimental: true
-              basename: Tests
-
-            - toolchain: stable
-              os: macos-latest
-              llvm: ["18.1", "18-1", "181"]
-              features: "rayon cranelift external_f64"
-              tests: true
-              clippy: false
-              rustdoc: false
-              experimental: true
-              basename: Tests
-
             - toolchain: stable
               os: windows-latest
               llvm: ""

diffsl/src/discretise/discrete_model.rs

@@ -615,6 +615,12 @@ impl<'s> DiscreteModel<'s> {
                 Self::check_match(reset, &ret.state, span, &mut env);
             }
         }
+        if ret.reset.is_some() && ret.stop.is_none() {
+            env.errs_mut().push(ValidationError::new(
+                "reset requires stop to also be defined".to_string(),
+                span_reset.flatten(),
+            ));
+        }
 
         let map_dep = |deps: &Vec<NonZero>| -> Vec<(usize, usize)> {
             deps.iter()
@@ -1722,6 +1728,32 @@ mod tests {
         );
     }
 
+    #[test]
+    fn test_reset_requires_stop() {
+        let text = "
+        u_i {
+            y = 1,
+        }
+        F_i {
+            y,
+        }
+        reset_i {
+            2 * y,
+        }
+        ";
+        let model_ds = parse_ds_string(text).unwrap();
+        let model = DiscreteModel::build("$name", &model_ds);
+        assert!(
+            model.is_err(),
+            "reset_i should require stop_i to also be defined"
+        );
+        let errs = model.unwrap_err();
+        assert!(
+            errs.has_error_contains("reset requires stop to also be defined"),
+            "expected missing stop validation error"
+        );
+    }
+
     #[test]
     fn test_no_out() {
         let text = "