fix signal error message and add tests (#2118)

packages/generational-box/src/error.rs

@@ -2,7 +2,7 @@ use std::error::Error;
 use std::fmt::Debug;
 use std::fmt::Display;
 
-#[derive(Debug, Clone)]
+#[derive(Debug, Clone, PartialEq)]
 /// An error that can occur when trying to borrow a value.
 pub enum BorrowError {
     /// The value was dropped.
@@ -22,7 +22,7 @@ impl Display for BorrowError {
 
 impl Error for BorrowError {}
 
-#[derive(Debug, Clone)]
+#[derive(Debug, Clone, PartialEq)]
 /// An error that can occur when trying to borrow a value mutably.
 pub enum BorrowMutError {
     /// The value was dropped.
@@ -46,12 +46,23 @@ impl Display for BorrowMutError {
 impl Error for BorrowMutError {}
 
 /// An error that can occur when trying to use a value that has been dropped.
-#[derive(Debug, Copy, Clone)]
+#[derive(Debug, Copy, Clone, PartialEq)]
 pub struct ValueDroppedError {
     #[cfg(any(debug_assertions, feature = "debug_ownership"))]
     pub(crate) created_at: &'static std::panic::Location<'static>,
 }
 
+impl ValueDroppedError {
+    /// Create a new `ValueDroppedError`.
+    #[allow(unused)]
+    pub fn new(created_at: &'static std::panic::Location<'static>) -> Self {
+        Self {
+            #[cfg(any(debug_assertions, feature = "debug_ownership"))]
+            created_at,
+        }
+    }
+}
+
 impl Display for ValueDroppedError {
     fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
         f.write_str("Failed to borrow because the value was dropped.")?;
@@ -64,12 +75,23 @@ impl Display for ValueDroppedError {
 impl std::error::Error for ValueDroppedError {}
 
 /// An error that can occur when trying to borrow a value that has already been borrowed mutably.
-#[derive(Debug, Copy, Clone)]
+#[derive(Debug, Copy, Clone, PartialEq)]
 pub struct AlreadyBorrowedMutError {
     #[cfg(any(debug_assertions, feature = "debug_borrows"))]
     pub(crate) borrowed_mut_at: &'static std::panic::Location<'static>,
 }
 
+impl AlreadyBorrowedMutError {
+    /// Create a new `AlreadyBorrowedMutError`.
+    #[allow(unused)]
+    pub fn new(borrowed_mut_at: &'static std::panic::Location<'static>) -> Self {
+        Self {
+            #[cfg(any(debug_assertions, feature = "debug_borrows"))]
+            borrowed_mut_at,
+        }
+    }
+}
+
 impl Display for AlreadyBorrowedMutError {
     fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
         f.write_str("Failed to borrow because the value was already borrowed mutably.")?;
@@ -82,12 +104,23 @@ impl Display for AlreadyBorrowedMutError {
 impl std::error::Error for AlreadyBorrowedMutError {}
 
 /// An error that can occur when trying to borrow a value mutably that has already been borrowed immutably.
-#[derive(Debug, Clone)]
+#[derive(Debug, Clone, PartialEq)]
 pub struct AlreadyBorrowedError {
     #[cfg(any(debug_assertions, feature = "debug_borrows"))]
     pub(crate) borrowed_at: Vec<&'static std::panic::Location<'static>>,
 }
 
+impl AlreadyBorrowedError {
+    /// Create a new `AlreadyBorrowedError`.
+    #[allow(unused)]
+    pub fn new(borrowed_at: Vec<&'static std::panic::Location<'static>>) -> Self {
+        Self {
+            #[cfg(any(debug_assertions, feature = "debug_borrows"))]
+            borrowed_at,
+        }
+    }
+}
+
 impl Display for AlreadyBorrowedError {
     fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
         f.write_str("Failed to borrow mutably because the value was already borrowed immutably.")?;