fix signal error message and add tests (#2118)

packages/generational-box/tests/errors.rs

@@ -0,0 +1,99 @@
+use std::cell::{Ref, RefMut};
+
+use generational_box::{
+    AlreadyBorrowedError, AlreadyBorrowedMutError, AnyStorage, BorrowError, BorrowMutError,
+    GenerationalBox, GenerationalRef, GenerationalRefMut, Owner, UnsyncStorage, ValueDroppedError,
+};
+
+#[track_caller]
+fn read_at_location(
+    value: GenerationalBox<i32>,
+) -> (
+    GenerationalRef<Ref<'static, i32>>,
+    &'static std::panic::Location<'static>,
+) {
+    let location = std::panic::Location::caller();
+    let read = value.read();
+    (read, location)
+}
+
+#[track_caller]
+fn write_at_location(
+    value: GenerationalBox<i32>,
+) -> (
+    GenerationalRefMut<RefMut<'static, i32>>,
+    &'static std::panic::Location<'static>,
+) {
+    let location = std::panic::Location::caller();
+    let write = value.write();
+    (write, location)
+}
+
+#[track_caller]
+fn create_at_location(
+    owner: &Owner,
+) -> (GenerationalBox<i32>, &'static std::panic::Location<'static>) {
+    let location = std::panic::Location::caller();
+    let value = owner.insert(1);
+    (value, location)
+}
+
+#[test]
+fn read_while_writing_error() {
+    let owner = UnsyncStorage::owner();
+    let value = owner.insert(1);
+
+    let (write, location) = write_at_location(value);
+
+    assert_eq!(
+        value.try_read().err(),
+        Some(BorrowError::AlreadyBorrowedMut(
+            AlreadyBorrowedMutError::new(location)
+        ))
+    );
+    drop(write);
+}
+
+#[test]
+fn read_after_dropped_error() {
+    let owner = UnsyncStorage::owner();
+    let (value, location) = create_at_location(&owner);
+    drop(owner);
+    assert_eq!(
+        value.try_read().err(),
+        Some(BorrowError::Dropped(ValueDroppedError::new(location)))
+    );
+}
+
+#[test]
+fn write_while_writing_error() {
+    let owner = UnsyncStorage::owner();
+    let value = owner.insert(1);
+
+    let (write, location) = write_at_location(value);
+
+    assert_eq!(
+        value.try_write().err(),
+        Some(BorrowMutError::AlreadyBorrowedMut(
+            AlreadyBorrowedMutError::new(location)
+        ))
+    );
+    drop(write);
+}
+
+#[test]
+fn write_while_reading_error() {
+    let owner = UnsyncStorage::owner();
+    let value = owner.insert(1);
+
+    let (read, location) = read_at_location(value);
+
+    assert_eq!(
+        value.try_write().err(),
+        Some(BorrowMutError::AlreadyBorrowed(AlreadyBorrowedError::new(
+            vec![location]
+        )))
+    );
+
+    drop(read);
+}