Validate method substitution before definition updates and execution

crates/core/src/eval.rs

@@ -166,14 +166,29 @@ impl Vm {
         for value in arguments {
             self.validate_value(value)?;
         }
+        let receiver = arguments
+            .first()
+            .or_else(|| {
+                if required == 0 {
+                    data.defaults().first()
+                } else {
+                    None
+                }
+            })
+            .and_then(|value| match value {
+                Value::Object(receiver) => Some(*receiver),
+                _ => None,
+            });
+        if self.source_type_checks
+            && let Some(receiver) = receiver
+        {
+            self.objects
+                .check_method_override_call(function, receiver)?;
+        }
         let mut return_type = None;
         if self.source_type_checks
             && let Some(signature) = executable.source_signature()
         {
-            let receiver = arguments.first().and_then(|value| match value {
-                Value::Object(object) => Some(*object),
-                _ => None,
-            });
             for (index, expected_name) in signature.parameters.iter().enumerate() {
                 let value = arguments
                     .get(index)
@@ -262,6 +277,12 @@ impl Vm {
         for argument in arguments {
             self.validate_value(argument)?;
         }
+        if self.source_type_checks
+            && let Some(Value::Object(receiver)) = arguments.first()
+        {
+            self.objects
+                .check_method_override_call(function, *receiver)?;
+        }
         if let Some(arity) = self.objects.call_arity(function)?
             && !arity.accepts(arguments.len())
         {