From f3b24a7f76297ff548c779b3f7eb74faea59e36c Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Adam=20Wagenh=C3=A4user?=
 <adam.wagenhaeuser@fath-mechatronics.de>
Date: Tue, 25 Mar 2025 14:48:54 +0100
Subject: [PATCH] Make the heapless to alloc Vec conversion fallible as well.

This allows to catch OOM errors.
---
 CHANGELOG.md   |  4 ++--
 src/vec/mod.rs | 23 ++++++++++++++++++++---
 2 files changed, 22 insertions(+), 5 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index b4df7eeb..c29d8608 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -42,8 +42,8 @@ and this project adheres to [Semantic Versioning](http://semver.org/).
 - Make `String::from_utf8_unchecked` const.
 - Implemented `PartialEq` and `Eq` for `Deque`.
 - Added `alloc` feature to enable `alloc`-Vec interoperability.
-- Added `From<alloc::vec::Vec>` impl for `Vec`.
-- Added `From<Vec>` impl for `alloc::vec::Vec`.
+- Added `TryFrom<alloc::vec::Vec>` impl for `Vec`.
+- Added `TryFrom<Vec>` impl for `alloc::vec::Vec`.
 
 ### Changed
 
diff --git a/src/vec/mod.rs b/src/vec/mod.rs
index fd3c85be..40ddf98a 100644
--- a/src/vec/mod.rs
+++ b/src/vec/mod.rs
@@ -1232,6 +1232,7 @@ impl<T, const N: usize> TryFrom<alloc::vec::Vec<T>> for Vec<T, N> {
         let mut vec = Vec::new();
 
         for e in alloc_vec {
+            // Push each element individually to allow handling capacity errors.
             vec.push(e).map_err(|_| ())?;
         }
 
@@ -1241,10 +1242,26 @@ impl<T, const N: usize> TryFrom<alloc::vec::Vec<T>> for Vec<T, N> {
 
 #[cfg(feature = "alloc")]
 /// Converts the given `Vec<T, N>` into an `alloc::vec::Vec<T>`.
-impl<T, const N: usize> From<Vec<T, N>> for alloc::vec::Vec<T> {
+impl<T, const N: usize> TryFrom<Vec<T, N>> for alloc::vec::Vec<T> {
+    type Error = ();
+
     /// Converts the given `Vec<T, N>` into an `alloc::vec::Vec<T>`.
-    fn from(vec: Vec<T, N>) -> Self {
-        alloc::vec::Vec::from_iter(vec.into_iter())
+    ///
+    /// # Errors
+    ///
+    /// Returns `Err` if the `alloc::vec::Vec` fails to allocate memory.
+    fn try_from(vec: Vec<T, N>) -> Result<Self, Self::Error> {
+        let mut alloc_vec = alloc::vec::Vec::new();
+
+        // Allocate enough space for the elements, return an error if the
+        // allocation fails.
+        alloc_vec.try_reserve(vec.len()).map_err(|_| ())?;
+
+        // Transfer the elements, since we reserved enough space above, this
+        // should not fail due to OOM.
+        alloc_vec.extend(vec);
+
+        Ok(alloc_vec)
     }
 }