Add Result and Error helper methods

Author: josephlr

src/result/error.rs

@@ -21,6 +21,11 @@ impl<Data: Debug> Error<Data> {
     pub fn data(&self) -> &Data {
         &self.data
     }
+
+    /// Split this error into its inner status and error data
+    pub fn split(self) -> (Status, Data) {
+        (self.status, self.data)
+    }
 }
 
 // Errors without payloads can be autogenerated from statuses

src/result/mod.rs

@@ -43,6 +43,9 @@ pub trait ResultExt<Output, ErrData: Debug> {
     /// Expect success without warnings, panic with provided message otherwise
     fn expect_success(self, msg: &str) -> Output;
 
+    /// Expect error, panic with provided message otherwise, discarding output
+    fn expect_error(self, msg: &str) -> Error<ErrData>;
+
     /// Transform the inner output, if any
     fn map_inner<Mapped>(self, f: impl FnOnce(Output) -> Mapped) -> Result<Mapped, ErrData>;
 
@@ -75,6 +78,10 @@ impl<Output, ErrData: Debug> ResultExt<Output, ErrData> for Result<Output, ErrDa
         self.expect(msg).expect(msg)
     }
 
+    fn expect_error(self, msg: &str) -> Error<ErrData> {
+        self.map(|completion| completion.status()).expect_err(msg)
+    }
+
     fn map_inner<Mapped>(self, f: impl FnOnce(Output) -> Mapped) -> Result<Mapped, ErrData> {
         self.map(|completion| completion.map(f))
     }