move core result into core utils

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

src/core/utils/result/map_expect.rs

@@ -0,0 +1,15 @@
+use std::fmt::Debug;
+
+use super::Result;
+
+pub trait MapExpect<T> {
+	/// Calls expect(msg) on the mapped Result value. This is similar to
+	/// map(Result::unwrap) but composes an expect call and message without
+	/// requiring a closure.
+	fn map_expect(self, msg: &str) -> Option<T>;
+}
+
+impl<T, E: Debug> MapExpect<T> for Option<Result<T, E>> {
+	#[inline]
+	fn map_expect(self, msg: &str) -> Option<T> { self.map(|result| result.expect(msg)) }
+}