From 28c993afe1255057da5ac844f0cd68c8eed22561 Mon Sep 17 00:00:00 2001
From: Phan Huy Hoang <hoangph271@gmail.com>
Date: Mon, 9 Jan 2023 10:14:20 +0700
Subject: [PATCH] [Add] exercises/error_handling

---
 exercises/error_handling/errors2.rs |  2 +-
 exercises/error_handling/errors4.rs | 11 +++++++----
 exercises/error_handling/errors5.rs |  4 +---
 exercises/error_handling/errors6.rs | 11 ++++-------
 4 files changed, 13 insertions(+), 15 deletions(-)

diff --git a/exercises/error_handling/errors2.rs b/exercises/error_handling/errors2.rs
index f581de44..0bd0530a 100644
--- a/exercises/error_handling/errors2.rs
+++ b/exercises/error_handling/errors2.rs
@@ -24,7 +24,7 @@ pub fn total_cost(item_quantity: &str) -> Result<i32, ParseIntError> {
     let cost_per_item = 5;
     let qty = item_quantity.parse::<i32>()?;
 
-    Ok(qty * cost_per_item + processing_fee.ok)
+    Ok(qty * cost_per_item + processing_fee)
 }
 
 #[cfg(test)]
diff --git a/exercises/error_handling/errors4.rs b/exercises/error_handling/errors4.rs
index 0efe8ccd..e23b32c4 100644
--- a/exercises/error_handling/errors4.rs
+++ b/exercises/error_handling/errors4.rs
@@ -1,8 +1,6 @@
 // errors4.rs
 // Execute `rustlings hint errors4` or use the `hint` watch subcommand for a hint.
 
-// I AM NOT DONE
-
 #[derive(PartialEq, Debug)]
 struct PositiveNonzeroInteger(u64);
 
@@ -14,8 +12,13 @@ enum CreationError {
 
 impl PositiveNonzeroInteger {
     fn new(value: i64) -> Result<PositiveNonzeroInteger, CreationError> {
-        // Hmm...? Why is this only returning an Ok value?
-        Ok(PositiveNonzeroInteger(value as u64))
+        // // Hmm...? Why is this only returning an Ok value?
+        // Ok(PositiveNonzeroInteger(value as u64))
+        match value {
+            x if x < 0 => Err(CreationError::Negative),
+            0 => Err(CreationError::Zero),
+            _ => Ok(PositiveNonzeroInteger(value as u64))
+        }
     }
 }
 
diff --git a/exercises/error_handling/errors5.rs b/exercises/error_handling/errors5.rs
index 6da06ef3..f93f705c 100644
--- a/exercises/error_handling/errors5.rs
+++ b/exercises/error_handling/errors5.rs
@@ -16,14 +16,12 @@
 
 // Execute `rustlings hint errors5` or use the `hint` watch subcommand for a hint.
 
-// I AM NOT DONE
-
 use std::error;
 use std::fmt;
 use std::num::ParseIntError;
 
 // TODO: update the return type of `main()` to make this compile.
-fn main() -> Result<(), Box<dyn ???>> {
+fn main() -> Result<(), Box<dyn error::Error>> {
     let pretend_user_input = "42";
     let x: i64 = pretend_user_input.parse()?;
     println!("output={:?}", PositiveNonzeroInteger::new(x)?);
diff --git a/exercises/error_handling/errors6.rs b/exercises/error_handling/errors6.rs
index 8097b490..991af297 100644
--- a/exercises/error_handling/errors6.rs
+++ b/exercises/error_handling/errors6.rs
@@ -8,8 +8,6 @@
 
 // Execute `rustlings hint errors6` or use the `hint` watch subcommand for a hint.
 
-// I AM NOT DONE
-
 use std::num::ParseIntError;
 
 // This is a custom error type that we will be using in `parse_pos_nonzero()`.
@@ -23,14 +21,13 @@ impl ParsePosNonzeroError {
     fn from_creation(err: CreationError) -> ParsePosNonzeroError {
         ParsePosNonzeroError::Creation(err)
     }
-    // TODO: add another error conversion function here.
-    // fn from_parseint...
+    fn from_parseint (err: ParseIntError) -> ParsePosNonzeroError {
+        ParsePosNonzeroError::ParseInt(err)
+    }
 }
 
 fn parse_pos_nonzero(s: &str) -> Result<PositiveNonzeroInteger, ParsePosNonzeroError> {
-    // TODO: change this to return an appropriate error instead of panicking
-    // when `parse()` returns an error.
-    let x: i64 = s.parse().unwrap();
+    let x: i64 = s.parse().map_err(ParsePosNonzeroError::from_parseint)?;
     PositiveNonzeroInteger::new(x).map_err(ParsePosNonzeroError::from_creation)
 }