Add BoxedRefMut::into_const()

Author: twistedfall

src/boxed_ref.rs

@@ -6,8 +6,10 @@ use crate::traits::{Boxed, OpenCVFromExtern, OpenCVIntoExternContainer, OpenCVTy
 
 /// Wrapper for the type implementing [Boxed] trait that allows to retain the lifetime of the referenced object.
 ///
-/// This wrapper implements all traits that the underlying type does, but explicitly doesn't implement `Deref` and `DerefMut` to
-/// avoid being able to `mem::swap` the reference out of the wrapper.
+/// This wrapper implements all traits that the underlying type does, but explicitly doesn't implement [Deref](core::ops::Deref) and
+/// [DerefMut](core::ops::DerefMut) to avoid being able to [swap](core::mem::swap) the reference out of the wrapper. It relies on
+/// functions accepting generic arguments (e.g. `impl MatTrait` or `impl MatTraitConst`) which are implemented by both main struct
+/// and its `BoxedRef` (e.g. [Mat](crate::core::Mat) and `BoxedRef<Mat>`).
 #[repr(transparent)]
 pub struct BoxedRef<'r, T: Boxed> {
 	pub(crate) reference: T,
@@ -32,7 +34,7 @@ impl<T: Boxed + fmt::Debug> fmt::Debug for BoxedRef<'_, T> {
 }
 
 impl<T: Boxed + Clone> BoxedRef<'_, T> {
-	/// Clones the pointee of this BoxedRef
+	/// Clones the pointee of this [BoxedRef]
 	#[inline]
 	pub fn clone_pointee(&self) -> T {
 		self.reference.clone()
@@ -104,13 +106,20 @@ impl<T: Boxed + fmt::Debug> fmt::Debug for BoxedRefMut<'_, T> {
 }
 
 impl<T: Boxed + Clone> BoxedRefMut<'_, T> {
-	/// Clones the pointee of this BoxedRef
+	/// Clones the pointee of this [BoxedRefMut]
 	#[inline]
 	pub fn clone_pointee(&self) -> T {
 		self.reference.clone()
 	}
 }
 
+impl<'r, T: Boxed> From<BoxedRefMut<'r, T>> for BoxedRef<'r, T> {
+	/// Irreversibly convert this [BoxedRefMut] into a non-mutable [BoxedRef]
+	fn from(value: BoxedRefMut<'r, T>) -> Self {
+		BoxedRef::from(value.reference)
+	}
+}
+
 impl<T: OpenCVIntoExternContainer + Boxed> OpenCVIntoExternContainer for BoxedRefMut<'_, T> {
 	type ExternContainer = T::ExternContainer;
 

tests/boxed_ref.rs

@@ -122,3 +122,16 @@ fn vector_boxed_ref() -> Result<()> {
 
 	Ok(())
 }
+
+#[test]
+fn boxed_ref_into() -> Result<()> {
+	let mut s = [1i32, 2, 3, 4];
+	let mut mut_m = Mat::from_slice_mut(&mut s)?;
+	*mut_m.at_mut::<i32>(1)? = 100;
+	let const_m = BoxedRef::<Mat>::from(mut_m);
+
+	assert_eq!(100, *const_m.at::<i32>(1)?);
+	assert_eq!(100, s[1]);
+
+	Ok(())
+}