1 files changed, 28 insertions, 2 deletions
diff --git a/src/checker_signature.rs b/src/checker_signature.rs
index 8e99d3c..bf04308 100644
--- a/src/checker_signature.rs
+++ b/src/checker_signature.rs
@@ -241,8 +241,34 @@ impl CheckerState {
                             Box::new(element),
                         ))
                     }
-                    Instance::For { .. } => {
-                        todo!("app for")
+                    Instance::For { params, body } => {
+                        if params.is_empty() {
+                            panic!(
+                                "It should have been impossible to construct a For with no params, but here we are"
+                            );
+                        }
+                        let mut ctx = self.clone();
+                        for (idx, param) in params.iter().enumerate() {
+                            let Param {
+                                name: param_name,
+                                set: param_set,
+                            } = param.clone();
+                            if idx == 0 {
+                                let element = self.check_element(&*element, &param_set)?;
+                                ctx.make_element_definition(param_name, element, param_set)?;
+                            } else {
+                                ctx.make_element_binding(param_name, param_set)?;
+                            }
+                        }
+                        let instance = ctx.check_instance(body, signature)?;
+                        if params.len() == 1 {
+                            Ok(instance)
+                        } else {
+                            Ok(Instance::For {
+                                params: params[1..].iter().map(|p| p.clone()).collect(),
+                                body: Box::new(instance),
+                            })
+                        }
                     }
                     Instance::Record(_) | Instance::SetCoerce(_) => {
                         Err(CheckerError::NonFunctionalInstance {