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@ -33,84 +33,84 @@ use std::{error::Error, fmt};
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/// statement.
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pub trait FatalError: Error {}
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/// Result<A, FE, E> represents a return value that might be a success, might be a fatal error, or
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/// Flow<A, FE, E> represents a return value that might be a success, might be a fatal error, or
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/// might be a normal handleable error.
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pub enum Result<A, E, FE> {
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pub enum Flow<A, FE, E> {
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/// The operation was successful
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Ok(A),
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/// Ordinary errors. These should be handled and the application should recover gracefully.
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Err(E),
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/// The operation encountered a fatal error. These should be bubbled up to a level that can
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/// safely shut the application down.
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Fatal(FE),
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/// Ordinary errors. These should be handled and the application should recover gracefully.
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Err(E),
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}
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impl<A, E, FE> Result<A, E, FE> {
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impl<A, FE, E> Flow<A, FE, E> {
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/// Apply an infallible function to a successful value.
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pub fn map<B, O>(self, mapper: O) -> Result<B, E, FE>
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pub fn map<B, O>(self, mapper: O) -> Flow<B, FE, E>
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where
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O: FnOnce(A) -> B,
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{
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match self {
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Result::Ok(val) => Result::Ok(mapper(val)),
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Result::Err(err) => Result::Err(err),
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Result::Fatal(err) => Result::Fatal(err),
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Flow::Ok(val) => Flow::Ok(mapper(val)),
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Flow::Fatal(err) => Flow::Fatal(err),
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Flow::Err(err) => Flow::Err(err),
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}
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}
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/// Apply a potentially fallible function to a successful value.
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///
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/// Like `Result.and_then`, the mapping function can itself fail.
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pub fn and_then<B, O>(self, handler: O) -> Result<B, E, FE>
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pub fn and_then<B, O>(self, handler: O) -> Flow<B, FE, E>
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where
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O: FnOnce(A) -> Result<B, E, FE>,
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O: FnOnce(A) -> Flow<B, FE, E>,
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{
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match self {
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Result::Ok(val) => handler(val),
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Result::Err(err) => Result::Err(err),
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Result::Fatal(err) => Result::Fatal(err),
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Flow::Ok(val) => handler(val),
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Flow::Fatal(err) => Flow::Fatal(err),
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Flow::Err(err) => Flow::Err(err),
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}
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}
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/// Map a normal error from one type to another. This is useful for converting an error from
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/// one type to another, especially in re-throwing an underlying error. `?` syntax does not
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/// work with `Result`, so you will likely need to use this a lot.
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pub fn map_err<F, O>(self, mapper: O) -> Result<A, F, FE>
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/// work with `Flow`, so you will likely need to use this a lot.
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pub fn map_err<F, O>(self, mapper: O) -> Flow<A, FE, F>
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where
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O: FnOnce(E) -> F,
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{
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match self {
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Result::Ok(val) => Result::Ok(val),
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Result::Err(err) => Result::Err(mapper(err)),
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Result::Fatal(err) => Result::Fatal(err),
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Flow::Ok(val) => Flow::Ok(val),
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Flow::Fatal(err) => Flow::Fatal(err),
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Flow::Err(err) => Flow::Err(mapper(err)),
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}
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}
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/// Provide a function to use to recover from (or simply re-throw) an error.
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pub fn or_else<O, F>(self, handler: O) -> Result<A, F, FE>
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pub fn or_else<O, F>(self, handler: O) -> Flow<A, FE, F>
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where
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O: FnOnce(E) -> Result<A, F, FE>,
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O: FnOnce(E) -> Flow<A, FE, F>,
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{
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match self {
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Result::Ok(val) => Result::Ok(val),
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Result::Err(err) => handler(err),
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Result::Fatal(err) => Result::Fatal(err),
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Flow::Ok(val) => Flow::Ok(val),
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Flow::Fatal(err) => Flow::Fatal(err),
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Flow::Err(err) => handler(err),
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}
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}
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}
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/// Convert from a normal `Result` type to a `Result` type. The error condition for a `Result` will
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/// be treated as `Result::Err`, never `Result::Fatal`.
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impl<A, E, FE> From<std::result::Result<A, E>> for Result<A, E, FE> {
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fn from(r: std::result::Result<A, E>) -> Self {
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/// Convert from a normal `Result` type to a `Flow` type. The error condition for a `Result` will
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/// be treated as `Flow::Err`, never `Flow::Fatal`.
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impl<A, FE, E> From<Result<A, E>> for Flow<A, FE, E> {
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fn from(r: Result<A, E>) -> Self {
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match r {
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Ok(val) => Result::Ok(val),
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Err(err) => Result::Err(err),
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Ok(val) => Flow::Ok(val),
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Err(err) => Flow::Err(err),
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}
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}
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}
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impl<A, E, FE> fmt::Debug for Result<A, E, FE>
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impl<A, FE, E> fmt::Debug for Flow<A, FE, E>
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where
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A: fmt::Debug,
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FE: fmt::Debug,
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@ -118,14 +118,14 @@ where
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{
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fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
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match self {
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Result::Ok(val) => f.write_fmt(format_args!("Result::Ok {:?}", val)),
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Result::Err(err) => f.write_fmt(format_args!("Result::Err {:?}", err)),
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Result::Fatal(err) => f.write_fmt(format_args!("Result::Fatal {:?}", err)),
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Flow::Ok(val) => f.write_fmt(format_args!("Flow::Ok {:?}", val)),
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Flow::Err(err) => f.write_fmt(format_args!("Flow::Err {:?}", err)),
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Flow::Fatal(err) => f.write_fmt(format_args!("Flow::Fatal {:?}", err)),
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}
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}
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}
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impl<A, E, FE> PartialEq for Result<A, E, FE>
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impl<A, FE, E> PartialEq for Flow<A, FE, E>
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where
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A: PartialEq,
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FE: PartialEq,
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@ -133,27 +133,27 @@ where
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{
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fn eq(&self, rhs: &Self) -> bool {
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match (self, rhs) {
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(Result::Ok(val), Result::Ok(rhs)) => val == rhs,
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(Result::Err(_), Result::Err(_)) => true,
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(Result::Fatal(_), Result::Fatal(_)) => true,
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(Flow::Ok(val), Flow::Ok(rhs)) => val == rhs,
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(Flow::Err(_), Flow::Err(_)) => true,
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(Flow::Fatal(_), Flow::Fatal(_)) => true,
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_ => false,
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}
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}
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}
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/// Convenience function to create an ok value.
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pub fn ok<A, E: Error, FE: FatalError>(val: A) -> Result<A, E, FE> {
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Result::Ok(val)
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pub fn ok<A, FE: FatalError, E: Error>(val: A) -> Flow<A, FE, E> {
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Flow::Ok(val)
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}
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/// Convenience function to create an error value.
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pub fn error<A, E: Error, FE: FatalError>(err: E) -> Result<A, E, FE> {
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Result::Err(err)
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pub fn error<A, FE: FatalError, E: Error>(err: E) -> Flow<A, FE, E> {
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Flow::Err(err)
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}
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/// Convenience function to create a fatal value.
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pub fn fatal<A, E: Error, FE: FatalError>(err: FE) -> Result<A, E, FE> {
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Result::Fatal(err)
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pub fn fatal<A, FE: FatalError, E: Error>(err: FE) -> Flow<A, FE, E> {
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Flow::Fatal(err)
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}
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/// Return early from the current function if the value is a fatal error.
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@ -161,9 +161,9 @@ pub fn fatal<A, E: Error, FE: FatalError>(err: FE) -> Result<A, E, FE> {
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macro_rules! return_fatal {
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($x:expr) => {
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match $x {
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Result::Fatal(err) => return Result::Fatal(err),
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Result::Err(err) => Err(err),
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Result::Ok(val) => Ok(val),
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Flow::Fatal(err) => return Flow::Fatal(err),
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Flow::Err(err) => Err(err),
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Flow::Ok(val) => Ok(val),
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}
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};
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}
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@ -173,9 +173,9 @@ macro_rules! return_fatal {
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macro_rules! return_error {
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($x:expr) => {
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match $x {
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Result::Ok(val) => val,
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Result::Err(err) => return Result::Err(err),
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Result::Fatal(err) => return Result::Fatal(err),
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Flow::Ok(val) => val,
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Flow::Err(err) => return Flow::Err(err),
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Flow::Fatal(err) => return Flow::Fatal(err),
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}
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};
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}
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@ -210,45 +210,45 @@ mod test {
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#[test]
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fn it_can_map_things() {
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let success: Result<i32, Error, FatalError> = ok(15);
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let success: Flow<i32, FatalError, Error> = ok(15);
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assert_eq!(ok(16), success.map(|v| v + 1));
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}
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#[test]
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fn it_can_chain_success() {
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let success: Result<i32, Error, FatalError> = ok(15);
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let success: Flow<i32, FatalError, Error> = ok(15);
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assert_eq!(ok(16), success.and_then(|v| ok(v + 1)));
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}
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#[test]
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fn it_can_handle_an_error() {
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let failure: Result<i32, Error, FatalError> = error(Error::Error);
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let failure: Flow<i32, FatalError, Error> = error(Error::Error);
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assert_eq!(
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ok::<i32, Error, FatalError>(16),
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ok::<i32, FatalError, Error>(16),
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failure.or_else(|_| ok(16))
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);
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}
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#[test]
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fn early_exit_on_fatal() {
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fn ok_func() -> Result<i32, Error, FatalError> {
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let value = return_fatal!(ok::<i32, Error, FatalError>(15));
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fn ok_func() -> Flow<i32, FatalError, Error> {
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let value = return_fatal!(ok::<i32, FatalError, Error>(15));
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match value {
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Ok(_) => ok(14),
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Err(err) => error(err),
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}
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}
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fn err_func() -> Result<i32, Error, FatalError> {
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let value = return_fatal!(error::<i32, Error, FatalError>(Error::Error));
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fn err_func() -> Flow<i32, FatalError, Error> {
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let value = return_fatal!(error::<i32, FatalError, Error>(Error::Error));
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match value {
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Ok(_) => panic!("shouldn't have gotten here"),
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Err(_) => ok(0),
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}
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}
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fn fatal_func() -> Result<i32, Error, FatalError> {
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let _ = return_fatal!(fatal::<i32, Error, FatalError>(FatalError::FatalError));
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fn fatal_func() -> Flow<i32, FatalError, Error> {
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return_fatal!(fatal::<i32, FatalError, Error>(FatalError::FatalError));
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panic!("failed to bail");
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}
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@ -259,19 +259,19 @@ mod test {
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#[test]
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fn it_can_early_exit_on_all_errors() {
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fn ok_func() -> Result<i32, Error, FatalError> {
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let value = return_error!(ok::<i32, Error, FatalError>(15));
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fn ok_func() -> Flow<i32, FatalError, Error> {
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let value = return_error!(ok::<i32, FatalError, Error>(15));
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assert_eq!(value, 15);
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ok(14)
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}
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fn err_func() -> Result<i32, Error, FatalError> {
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return_error!(error::<i32, Error, FatalError>(Error::Error));
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fn err_func() -> Flow<i32, FatalError, Error> {
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return_error!(error::<i32, FatalError, Error>(Error::Error));
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panic!("failed to bail");
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}
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fn fatal_func() -> Result<i32, Error, FatalError> {
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return_error!(fatal::<i32, Error, FatalError>(FatalError::FatalError));
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fn fatal_func() -> Flow<i32, FatalError, Error> {
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return_error!(fatal::<i32, FatalError, Error>(FatalError::FatalError));
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panic!("failed to bail");
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}
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