From 8aa10b819c465eb17b3fd4558512469cfab6cd98 Mon Sep 17 00:00:00 2001
From: Benjamin Saunders <ben.e.saunders@gmail.com>
Date: Sat, 11 Jun 2022 11:07:24 -0700
Subject: [PATCH] Implement `cast` for `Unit<Vector<T, D, S>>`

Currently, `cast` is resolved via `Unit`'s `Deref` impl, which leads
to it confusingly stripping the `Unit` from `UnitVector`s. Add an
inherent impl which takes precedence, similar to the existing
specialization for `UnitQuaternion`.
---
 src/base/matrix.rs | 25 +++++++++++++++++++++++++
 1 file changed, 25 insertions(+)

diff --git a/src/base/matrix.rs b/src/base/matrix.rs
index 8f8786c1..d9294c9e 100644
--- a/src/base/matrix.rs
+++ b/src/base/matrix.rs
@@ -2186,3 +2186,28 @@ where
         }
     }
 }
+
+impl<T, D, S> Unit<Vector<T, D, S>>
+where
+    T: Scalar,
+    D: Dim,
+    S: RawStorage<T, D, U1>,
+{
+    /// Cast the components of `self` to another type.
+    ///
+    /// # Example
+    /// ```
+    /// # use nalgebra::Vector3;
+    /// let v = Vector3::<f64>::y_axis();
+    /// let v2 = v.cast::<f32>();
+    /// assert_eq!(v2, Vector3::<f32>::y_axis());
+    /// ```
+    pub fn cast<T2: Scalar>(self) -> Unit<OVector<T2, D>>
+    where
+        T: Scalar,
+        OVector<T2, D>: SupersetOf<Vector<T, D, S>>,
+        DefaultAllocator: Allocator<T2, D, U1>,
+    {
+        Unit::new_unchecked(crate::convert_ref(self.as_ref()))
+    }
+}