feat: throw compile error if read/write public state from private (#2804

)

Currently if accessing public state from private functions you will only
get an error at runtime. This pr changes such that you will receive a
compile-time error instead.

yarn-project/aztec-nr/aztec/src/state_vars/public_state.nr

@@ -6,6 +6,7 @@ use dep::std::option::Option;
 
 // docs:start:public_state_struct
 struct PublicState<T, T_SERIALIZED_LEN> {
+    context: Context,
     storage_slot: Field,
     serialization_methods: TypeSerializationInterface<T, T_SERIALIZED_LEN>,
 }
@@ -15,12 +16,13 @@ impl<T, T_SERIALIZED_LEN> PublicState<T, T_SERIALIZED_LEN> {
     // docs:start:public_state_struct_new
     pub fn new(
         // Note: Passing the contexts to new(...) just to have an interface compatible with a Map.
-        _: Context,
+        context: Context,
         storage_slot: Field,
         serialization_methods: TypeSerializationInterface<T, T_SERIALIZED_LEN>,
     ) -> Self {
         assert(storage_slot != 0, "Storage slot 0 not allowed. Storage slots must start from 1.");
         PublicState {
+            context,
             storage_slot,
             serialization_methods,
         }
@@ -29,12 +31,14 @@ impl<T, T_SERIALIZED_LEN> PublicState<T, T_SERIALIZED_LEN> {
 
     // docs:start:public_state_struct_read
     pub fn read(self) -> T {
+        assert(self.context.private.is_none(), "Public state writes only supported in public functions");
         storage_read(self.storage_slot, self.serialization_methods.deserialize)
     }
     // docs:end:public_state_struct_read
 
     // docs:start:public_state_struct_write
     pub fn write(self, value: T) {
+        assert(self.context.private.is_none(), "Public state writes only supported in public functions");
         let serialize = self.serialization_methods.serialize;
         let fields = serialize(value);
         storage_write(self.storage_slot, fields);