add Filter extension to Result

Signed-off-by: Jason Volk <jason@zemos.net>

src/core/utils/result/filter.rs

@@ -0,0 +1,21 @@
+use super::Result;
+
+pub trait Filter<T, E> {
+	/// Similar to Option::filter
+	#[must_use]
+	fn filter<P, U>(self, predicate: P) -> Self
+	where
+		P: FnOnce(&T) -> Result<(), U>,
+		E: From<U>;
+}
+
+impl<T, E> Filter<T, E> for Result<T, E> {
+	#[inline]
+	fn filter<P, U>(self, predicate: P) -> Self
+	where
+		P: FnOnce(&T) -> Result<(), U>,
+		E: From<U>,
+	{
+		self.and_then(move |t| predicate(&t).map(move |()| t).map_err(Into::into))
+	}
+}