chore: release 5.2.1

docs: add memark as a contributor for content

.all-contributorsrc

@@ -1371,6 +1371,204 @@
       "contributions": [
         "content"
       ]
+    },
+    {
+      "login": "wojexe",
+      "name": "wojexe",
+      "avatar_url": "https://avatars.githubusercontent.com/u/21208490?v=4",
+      "profile": "https://wojexe.com",
+      "contributions": [
+        "content"
+      ]
+    },
+    {
+      "login": "Tostapunk",
+      "name": "Mattia Schiavon",
+      "avatar_url": "https://avatars.githubusercontent.com/u/25140297?v=4",
+      "profile": "https://github.com/Tostapunk",
+      "contributions": [
+        "content"
+      ]
+    },
+    {
+      "login": "PrettyWood",
+      "name": "Eric Jolibois",
+      "avatar_url": "https://avatars.githubusercontent.com/u/18406791?v=4",
+      "profile": "http://toucantoco.com",
+      "contributions": [
+        "content"
+      ]
+    },
+    {
+      "login": "EdwinChang24",
+      "name": "Edwin Chang",
+      "avatar_url": "https://avatars.githubusercontent.com/u/88263098?v=4",
+      "profile": "http://edwinchang.vercel.app",
+      "contributions": [
+        "content"
+      ]
+    },
+    {
+      "login": "saikatdas0790",
+      "name": "Saikat Das",
+      "avatar_url": "https://avatars.githubusercontent.com/u/7412443?v=4",
+      "profile": "https://saikat.dev/",
+      "contributions": [
+        "content"
+      ]
+    },
+    {
+      "login": "thatlittleboy",
+      "name": "Jeremy Goh",
+      "avatar_url": "https://avatars.githubusercontent.com/u/30731072?v=4",
+      "profile": "https://github.com/thatlittleboy",
+      "contributions": [
+        "content"
+      ]
+    },
+    {
+      "login": "Lioness100",
+      "name": "Lioness100",
+      "avatar_url": "https://avatars.githubusercontent.com/u/65814829?v=4",
+      "profile": "https://github.com/Lioness100",
+      "contributions": [
+        "content"
+      ]
+    },
+    {
+      "login": "tvkn",
+      "name": "Tristan Nicholls",
+      "avatar_url": "https://avatars.githubusercontent.com/u/79277926?v=4",
+      "profile": "https://github.com/tvkn",
+      "contributions": [
+        "content"
+      ]
+    },
+    {
+      "login": "clairew",
+      "name": "Claire",
+      "avatar_url": "https://avatars.githubusercontent.com/u/9344258?v=4",
+      "profile": "http://clairewang.net",
+      "contributions": [
+        "content"
+      ]
+    },
+    {
+      "login": "Mouwrice",
+      "name": "Maurice Van Wassenhove",
+      "avatar_url": "https://avatars.githubusercontent.com/u/56763273?v=4",
+      "profile": "https://github.com/Mouwrice",
+      "contributions": [
+        "content"
+      ]
+    },
+    {
+      "login": "johnmendel",
+      "name": "John Mendelewski",
+      "avatar_url": "https://avatars.githubusercontent.com/u/77524?v=4",
+      "profile": "http://jmthree.com",
+      "contributions": [
+        "code"
+      ]
+    },
+    {
+      "login": "brianfakhoury",
+      "name": "Brian Fakhoury",
+      "avatar_url": "https://avatars.githubusercontent.com/u/20828724?v=4",
+      "profile": "http://fakhoury.xyz",
+      "contributions": [
+        "content"
+      ]
+    },
+    {
+      "login": "markusboehme",
+      "name": "Markus Boehme",
+      "avatar_url": "https://avatars.githubusercontent.com/u/5074759?v=4",
+      "profile": "https://github.com/markusboehme",
+      "contributions": [
+        "code"
+      ]
+    },
+    {
+      "login": "nico-vromans",
+      "name": "Nico Vromans",
+      "avatar_url": "https://avatars.githubusercontent.com/u/48183857?v=4",
+      "profile": "https://github.com/nico-vromans",
+      "contributions": [
+        "content"
+      ]
+    },
+    {
+      "login": "vostok92",
+      "name": "vostok92",
+      "avatar_url": "https://avatars.githubusercontent.com/u/540339?v=4",
+      "profile": "https://github.com/vostok92",
+      "contributions": [
+        "content"
+      ]
+    },
+    {
+      "login": "magnusrodseth",
+      "name": "Magnus Rødseth",
+      "avatar_url": "https://avatars.githubusercontent.com/u/59113973?v=4",
+      "profile": "http://magnusrodseth.vercel.app",
+      "contributions": [
+        "content"
+      ]
+    },
+    {
+      "login": "rubiesonthesky",
+      "name": "rubiesonthesky",
+      "avatar_url": "https://avatars.githubusercontent.com/u/2591240?v=4",
+      "profile": "https://github.com/rubiesonthesky",
+      "contributions": [
+        "content"
+      ]
+    },
+    {
+      "login": "GabrielBianconi",
+      "name": "Gabriel Bianconi",
+      "avatar_url": "https://avatars.githubusercontent.com/u/1275491?v=4",
+      "profile": "http://www.gabrielbianconi.com/",
+      "contributions": [
+        "content"
+      ]
+    },
+    {
+      "login": "Kodylow",
+      "name": "Kody Low",
+      "avatar_url": "https://avatars.githubusercontent.com/u/74332828?v=4",
+      "profile": "https://github.com/Kodylow",
+      "contributions": [
+        "content"
+      ]
+    },
+    {
+      "login": "rzrymiak",
+      "name": "rzrymiak",
+      "avatar_url": "https://avatars.githubusercontent.com/u/106121613?v=4",
+      "profile": "https://github.com/rzrymiak",
+      "contributions": [
+        "content"
+      ]
+    },
+    {
+      "login": "miguelraz",
+      "name": "Miguel Raz Guzmán Macedo",
+      "avatar_url": "https://avatars.githubusercontent.com/u/13056181?v=4",
+      "profile": "https://github.com/miguelraz",
+      "contributions": [
+        "content"
+      ]
+    },
+    {
+      "login": "memark",
+      "name": "Magnus Markling",
+      "avatar_url": "https://avatars.githubusercontent.com/u/318504?v=4",
+      "profile": "https://github.com/memark",
+      "contributions": [
+        "content"
+      ]
     }
   ],
   "contributorsPerLine": 8,

.editorconfig

@@ -2,6 +2,6 @@ root = true
 
 [*.rs]
 end_of_line = lf
-insert_final_newfile = true
+insert_final_newline = true
 indent_style = space
 indent_size = 4

AUTHORS.md

@@ -195,6 +195,34 @@ authors.
     <td align="center"><a href="https://jamesabromley.wordpress.com/"><img src="https://avatars.githubusercontent.com/u/2474334?v=4?s=100" width="100px;" alt=""/><br /><sub><b>James Bromley</b></sub></a><br /><a href="#content-jayber" title="Content">🖋</a></td>
     <td align="center"><a href="https://github.com/swhiteCQC"><img src="https://avatars.githubusercontent.com/u/77438466?v=4?s=100" width="100px;" alt=""/><br /><sub><b>swhiteCQC</b></sub></a><br /><a href="#content-swhiteCQC" title="Content">🖋</a></td>
     <td align="center"><a href="https://github.com/neilpate"><img src="https://avatars.githubusercontent.com/u/7802334?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Neil Pate</b></sub></a><br /><a href="#content-neilpate" title="Content">🖋</a></td>
+    <td align="center"><a href="https://wojexe.com"><img src="https://avatars.githubusercontent.com/u/21208490?v=4?s=100" width="100px;" alt=""/><br /><sub><b>wojexe</b></sub></a><br /><a href="#content-wojexe" title="Content">🖋</a></td>
+    <td align="center"><a href="https://github.com/Tostapunk"><img src="https://avatars.githubusercontent.com/u/25140297?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Mattia Schiavon</b></sub></a><br /><a href="#content-Tostapunk" title="Content">🖋</a></td>
+    <td align="center"><a href="http://toucantoco.com"><img src="https://avatars.githubusercontent.com/u/18406791?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Eric Jolibois</b></sub></a><br /><a href="#content-PrettyWood" title="Content">🖋</a></td>
+  </tr>
+  <tr>
+    <td align="center"><a href="http://edwinchang.vercel.app"><img src="https://avatars.githubusercontent.com/u/88263098?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Edwin Chang</b></sub></a><br /><a href="#content-EdwinChang24" title="Content">🖋</a></td>
+    <td align="center"><a href="https://saikat.dev/"><img src="https://avatars.githubusercontent.com/u/7412443?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Saikat Das</b></sub></a><br /><a href="#content-saikatdas0790" title="Content">🖋</a></td>
+    <td align="center"><a href="https://github.com/thatlittleboy"><img src="https://avatars.githubusercontent.com/u/30731072?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Jeremy Goh</b></sub></a><br /><a href="#content-thatlittleboy" title="Content">🖋</a></td>
+    <td align="center"><a href="https://github.com/Lioness100"><img src="https://avatars.githubusercontent.com/u/65814829?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Lioness100</b></sub></a><br /><a href="#content-Lioness100" title="Content">🖋</a></td>
+    <td align="center"><a href="https://github.com/tvkn"><img src="https://avatars.githubusercontent.com/u/79277926?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Tristan Nicholls</b></sub></a><br /><a href="#content-tvkn" title="Content">🖋</a></td>
+    <td align="center"><a href="http://clairewang.net"><img src="https://avatars.githubusercontent.com/u/9344258?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Claire</b></sub></a><br /><a href="#content-clairew" title="Content">🖋</a></td>
+    <td align="center"><a href="https://github.com/Mouwrice"><img src="https://avatars.githubusercontent.com/u/56763273?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Maurice Van Wassenhove</b></sub></a><br /><a href="#content-Mouwrice" title="Content">🖋</a></td>
+    <td align="center"><a href="http://jmthree.com"><img src="https://avatars.githubusercontent.com/u/77524?v=4?s=100" width="100px;" alt=""/><br /><sub><b>John Mendelewski</b></sub></a><br /><a href="https://github.com/rust-lang/rustlings/commits?author=johnmendel" title="Code">💻</a></td>
+  </tr>
+  <tr>
+    <td align="center"><a href="http://fakhoury.xyz"><img src="https://avatars.githubusercontent.com/u/20828724?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Brian Fakhoury</b></sub></a><br /><a href="#content-brianfakhoury" title="Content">🖋</a></td>
+    <td align="center"><a href="https://github.com/markusboehme"><img src="https://avatars.githubusercontent.com/u/5074759?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Markus Boehme</b></sub></a><br /><a href="https://github.com/rust-lang/rustlings/commits?author=markusboehme" title="Code">💻</a></td>
+    <td align="center"><a href="https://github.com/nico-vromans"><img src="https://avatars.githubusercontent.com/u/48183857?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Nico Vromans</b></sub></a><br /><a href="#content-nico-vromans" title="Content">🖋</a></td>
+    <td align="center"><a href="https://github.com/vostok92"><img src="https://avatars.githubusercontent.com/u/540339?v=4?s=100" width="100px;" alt=""/><br /><sub><b>vostok92</b></sub></a><br /><a href="#content-vostok92" title="Content">🖋</a></td>
+    <td align="center"><a href="http://magnusrodseth.vercel.app"><img src="https://avatars.githubusercontent.com/u/59113973?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Magnus Rødseth</b></sub></a><br /><a href="#content-magnusrodseth" title="Content">🖋</a></td>
+    <td align="center"><a href="https://github.com/rubiesonthesky"><img src="https://avatars.githubusercontent.com/u/2591240?v=4?s=100" width="100px;" alt=""/><br /><sub><b>rubiesonthesky</b></sub></a><br /><a href="#content-rubiesonthesky" title="Content">🖋</a></td>
+    <td align="center"><a href="http://www.gabrielbianconi.com/"><img src="https://avatars.githubusercontent.com/u/1275491?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Gabriel Bianconi</b></sub></a><br /><a href="#content-GabrielBianconi" title="Content">🖋</a></td>
+    <td align="center"><a href="https://github.com/Kodylow"><img src="https://avatars.githubusercontent.com/u/74332828?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Kody Low</b></sub></a><br /><a href="#content-Kodylow" title="Content">🖋</a></td>
+  </tr>
+  <tr>
+    <td align="center"><a href="https://github.com/rzrymiak"><img src="https://avatars.githubusercontent.com/u/106121613?v=4?s=100" width="100px;" alt=""/><br /><sub><b>rzrymiak</b></sub></a><br /><a href="#content-rzrymiak" title="Content">🖋</a></td>
+    <td align="center"><a href="https://github.com/miguelraz"><img src="https://avatars.githubusercontent.com/u/13056181?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Miguel Raz Guzmán Macedo</b></sub></a><br /><a href="#content-miguelraz" title="Content">🖋</a></td>
+    <td align="center"><a href="https://github.com/memark"><img src="https://avatars.githubusercontent.com/u/318504?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Magnus Markling</b></sub></a><br /><a href="#content-memark" title="Content">🖋</a></td>
   </tr>
 </table>
 

CHANGELOG.md

@@ -1,3 +1,76 @@
+<a name="5.2.1"></a>
+## 5.2.1 (2022-09-06)
+
+#### Fixed
+
+- **quiz1**: Reworded the comment to actually reflect what's going on in the tests.
+  Also added another assert just to make sure.
+- **rc1**: Fixed a typo in the hint.
+- **lifetimes**: Add quotes to the `println!` output, for readability.
+
+#### Housekeeping
+
+- Fixed a typo in README.md
+
+<a name="5.2.0"></a>
+## 5.2.0 (2022-08-27)
+
+#### Added
+
+- Added a `reset` command
+
+#### Changed
+
+- **options2**: Convert the exercise to use tests
+
+#### Fixed
+
+- **threads3**: Fixed a typo
+- **quiz1**: Adjusted the explanations to be consistent with
+  the tests
+
+<a name="5.1.1"></a>
+## 5.1.1 (2022-08-17)
+
+#### Bug Fixes
+
+- Fixed an incorrect assertion in options1
+
+<a name="5.1.0"></a>
+## 5.1.0 (2022-08-16)
+
+#### Features
+
+- Added a new `rc1` exercise.
+- Added a new `cow1` exercise.
+
+#### Bug Fixes
+
+- **variables5**: Corrected reference to previous exercise
+- **functions4**: Fixed line number reference
+- **strings3**: Clarified comment wording
+- **traits4, traits5**: Fixed line number reference
+- **traits5**:
+  - Fixed typo in "parameter"
+  - Made exercise prefer a traits-based solution
+- **lifetimes2**: Improved hint
+- **threads3**: Fixed typo in hint
+- **box1**: Replaced `unimplemented!` with `todo!`
+- **errors5**: Provided an explanation for usage of `Box<dyn Error>`
+- **quiz2**: Fixed a typo
+- **macros**: Updated the macros book link
+- **options1**:
+  - Removed unused code
+  - Added more granular tests
+- Fixed some comment syntax shenanigans in info.toml
+
+#### Housekeeping
+
+- Fixed a typo in .editorconfig
+- Fixed a typo in integration_tests.rs
+- Clarified manual installation instructions using `cargo install --path .`
+- Added a link to our Zulip in the readme file
+
 <a name="5.0.0"></a>
 ## 5.0.0 (2022-07-16)
 

Cargo.lock

@@ -459,7 +459,7 @@ checksum = "f497285884f3fcff424ffc933e56d7cbca511def0c9831a7f9b5f6153e3cc89b"
 
 [[package]]
 name = "rustlings"
-version = "4.8.0"
+version = "5.2.1"
 dependencies = [
  "argh",
  "assert_cmd",

Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "rustlings"
-version = "5.0.0"
+version = "5.2.1"
 authors = ["Liv <mokou@fastmail.com>", "Carol (Nichols || Goulding) <carol.nichols@gmail.com>"]
 edition = "2021"
 

README.md

@@ -54,11 +54,11 @@ If you get a permission denied message, you might have to exclude the directory
 
 ## Manually
 
-Basically: Clone the repository at the latest tag, run `cargo install`.
+Basically: Clone the repository at the latest tag, run `cargo install --path .`.
 
 ```bash
-# find out the latest version at https://github.com/rust-lang/rustlings/releases/latest (on edit 5.0.0)
-git clone -b 5.0.0 --depth 1 https://github.com/rust-lang/rustlings
+# find out the latest version at https://github.com/rust-lang/rustlings/releases/latest (on edit 5.2.1)
+git clone -b 5.2.1 --depth 1 https://github.com/rust-lang/rustlings
 cd rustlings
 cargo install --force --path .
 ```
@@ -134,7 +134,7 @@ Once you've completed Rustlings, put your new knowledge to good use! Continue pr
 
 ## Uninstalling Rustlings
 
-If you want to remove Rustlings from your system, there's two steps. First, you'll need to remove the exercises folder that the install script created
+If you want to remove Rustlings from your system, there are two steps. First, you'll need to remove the exercises folder that the install script created
 for you:
 
 ```bash
@@ -154,6 +154,10 @@ Now you should be done!
 
 See [CONTRIBUTING.md](./CONTRIBUTING.md).
 
+Development-focused discussion about Rustlings happens in the [**rustlings** stream](https://rust-lang.zulipchat.com/#narrow/stream/334454-rustlings)
+on the [Rust Project Zulip](https://rust-lang.zulipchat.com). Feel free to start a new thread there
+if you have ideas or suggestions!
+
 ## Contributors ✨
 
 Thanks goes to the wonderful people listed in [AUTHORS.md](./AUTHORS.md) 🎉

exercises/error_handling/errors5.rs

@@ -4,6 +4,8 @@
 
 // This exercise uses some concepts that we won't get to until later in the course, like `Box` and the
 // `From` trait. It's not important to understand them in detail right now, but you can read ahead if you like.
+// For now, think of the `Box<dyn ...>` type as an "I want anything that does ???" type, which, given
+// Rust's usual standards for runtime safety, should strike you as somewhat lenient!
 
 // In short, this particular use case for boxes is for when you want to own a value and you care only that it is a 
 // type which implements a particular trait. To do so, The Box is declared as of type Box<dyn Trait> where Trait is the trait

exercises/lifetimes/lifetimes1.rs

@@ -22,5 +22,5 @@ fn main() {
     let string2 = "xyz";
 
     let result = longest(string1.as_str(), string2);
-    println!("The longest string is {}", result);
+    println!("The longest string is '{}'", result);
 }

exercises/lifetimes/lifetimes2.rs

@@ -23,5 +23,5 @@ fn main() {
         let string2 = String::from("xyz");
         result = longest(string1.as_str(), string2.as_str());
     }
-    println!("The longest string is {}", result);
+    println!("The longest string is '{}'", result);
 }

exercises/macros/README.md

@@ -7,4 +7,4 @@ macros. Instead, we'll show you how to use and create them.
 ## Further information
 
 - [Macros](https://doc.rust-lang.org/book/ch19-06-macros.html)
-- [The Little Book of Rust Macros](https://danielkeep.github.io/tlborm/book/index.html)
+- [The Little Book of Rust Macros](https://veykril.github.io/tlborm/)

exercises/options/options1.rs

@@ -3,17 +3,13 @@
 
 // I AM NOT DONE
 
-// you can modify anything EXCEPT for this function's signature
-fn print_number(maybe_number: Option<u16>) {
-    println!("printing: {}", maybe_number.unwrap());
-}
-
 // This function returns how much icecream there is left in the fridge.
 // If it's before 10PM, there's 5 pieces left. At 10PM, someone eats them
 // all, so there'll be no more left :(
 // TODO: Return an Option!
 fn maybe_icecream(time_of_day: u16) -> Option<u16> {
     // We use the 24-hour system here, so 10PM is a value of 22
+    // The Option output should gracefully handle cases where time_of_day > 24.
     ???
 }
 
@@ -23,9 +19,11 @@ mod tests {
 
     #[test]
     fn check_icecream() {
+        assert_eq!(maybe_icecream(9), Some(5));
         assert_eq!(maybe_icecream(10), Some(5));
-        assert_eq!(maybe_icecream(23), None);
-        assert_eq!(maybe_icecream(22), None);
+        assert_eq!(maybe_icecream(23), Some(0));
+        assert_eq!(maybe_icecream(22), Some(0));
+        assert_eq!(maybe_icecream(25), None);
     }
 
     #[test]

exercises/options/options2.rs

@@ -3,23 +3,34 @@
 
 // I AM NOT DONE
 
-fn main() {
-    let optional_word = Some(String::from("rustlings"));
-    // TODO: Make this an if let statement whose value is "Some" type
-    word = optional_word {
-        println!("The word is: {}", word);
-    } else {
-        println!("The optional word doesn't contain anything");
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn simple_option() {
+        let target = "rustlings";
+        let optional_target = Some(target);
+
+        // TODO: Make this an if let statement whose value is "Some" type
+        word = optional_target {
+            assert_eq!(word, target);
+        }
     }
 
-    let mut optional_integers_vec: Vec<Option<i8>> = Vec::new();
-    for x in 1..10 {
-        optional_integers_vec.push(Some(x));
-    }
+    #[test]
+    fn layered_option() {
+        let mut range = 10;
+        let mut optional_integers: Vec<Option<i8>> = Vec::new();
+        for i in 0..(range + 1) {
+            optional_integers.push(Some(i));
+        }
 
-    // TODO: make this a while let statement - remember that vector.pop also adds another layer of Option<T>
-    // You can stack `Option<T>`'s into while let and if let
-    integer = optional_integers_vec.pop() {
-        println!("current value: {}", integer);
+        // TODO: make this a while let statement - remember that vector.pop also adds another layer of Option<T>
+        // You can stack `Option<T>`'s into while let and if let
+        integer = optional_integers.pop() {
+            assert_eq!(integer, range);
+            range -= 1;
+        }
     }
 }

exercises/quiz1.rs

@@ -4,9 +4,11 @@
 // - Functions
 // - If
 
-// Mary is buying apples. One apple usually costs 2 Rustbucks, but if you buy
-// more than 40 at once, each apple only costs 1! Write a function that calculates
-// the price of an order of apples given the quantity bought. No hints this time!
+// Mary is buying apples. The price of an apple is calculated as follows:
+// - An apple costs 2 rustbucks.
+// - If Mary buys more than 40 apples, each apple only costs 1 rustbuck!
+// Write a function that calculates the price of an order of apples given
+// the quantity bought. No hints this time!
 
 // I AM NOT DONE
 
@@ -18,9 +20,11 @@
 fn verify_test() {
     let price1 = calculate_price_of_apples(35);
     let price2 = calculate_price_of_apples(40);
-    let price3 = calculate_price_of_apples(65);
+    let price3 = calculate_price_of_apples(41);
+    let price4 = calculate_price_of_apples(65);
 
     assert_eq!(70, price1);
     assert_eq!(80, price2);
-    assert_eq!(65, price3);
+    assert_eq!(41, price3);
+    assert_eq!(65, price4);
 }

exercises/quiz2.rs

@@ -42,7 +42,7 @@ mod my_module {
 
 #[cfg(test)]
 mod tests {
-    // TODO: What to we have to import to have `transformer` in scope?
+    // TODO: What do we have to import to have `transformer` in scope?
     use ???;
     use super::Command;
 

exercises/standard_library_types/box1.rs

@@ -10,7 +10,7 @@
 // elements: the value of the current item and the next item. The last item is a value called `Nil`.
 //
 // Step 1: use a `Box` in the enum definition to make the code compile
-// Step 2: create both empty and non-empty cons lists by replacing `unimplemented!()`
+// Step 2: create both empty and non-empty cons lists by replacing `todo!()`
 //
 // Note: the tests should not be changed
 //
@@ -33,11 +33,11 @@ fn main() {
 }
 
 pub fn create_empty_list() -> List {
-    unimplemented!()
+    todo!()
 }
 
 pub fn create_non_empty_list() -> List {
-    unimplemented!()
+    todo!()
 }
 
 #[cfg(test)]

exercises/standard_library_types/cow1.rs

@@ -0,0 +1,48 @@
+// cow1.rs
+
+// This exercise explores the Cow, or Clone-On-Write type.
+// Cow is a clone-on-write smart pointer.
+// It can enclose and provide immutable access to borrowed data, and clone the data lazily when mutation or ownership is required.
+// The type is designed to work with general borrowed data via the Borrow trait.
+
+// I AM NOT DONE
+
+use std::borrow::Cow;
+
+fn abs_all<'a, 'b>(input: &'a mut Cow<'b, [i32]>) -> &'a mut Cow<'b, [i32]> {
+    for i in 0..input.len() {
+        let v = input[i];
+        if v < 0 {
+            // Clones into a vector if not already owned.
+            input.to_mut()[i] = -v;
+        }
+    }
+    input
+}
+
+fn main() {
+    // No clone occurs because `input` doesn't need to be mutated.
+    let slice = [0, 1, 2];
+    let mut input = Cow::from(&slice[..]);
+    match abs_all(&mut input) {
+        Cow::Borrowed(_) => println!("I borrowed the slice!"),
+        _ => panic!("expected borrowed value"),
+    }
+
+    // Clone occurs because `input` needs to be mutated.
+    let slice = [-1, 0, 1];
+    let mut input = Cow::from(&slice[..]);
+    match abs_all(&mut input) {
+        Cow::Owned(_) => println!("I modified the slice and now own it!"),
+        _ => panic!("expected owned value"),
+    }
+
+    // No clone occurs because `input` is already owned.
+    let slice = vec![-1, 0, 1];
+    let mut input = Cow::from(slice);
+    match abs_all(&mut input) {
+        // TODO
+        Cow::Borrowed(_) => println!("I own this slice!"),
+        _ => panic!("expected borrowed value"),
+    }
+}

exercises/standard_library_types/rc1.rs

@@ -0,0 +1,98 @@
+// rc1.rs
+// In this exercise, we want to express the concept of multiple owners via the Rc<T> type.
+// This is a model of our solar system - there is a Sun type and multiple Planets.
+// The Planets take ownership of the sun, indicating that they revolve around the sun.
+
+// Make this code compile by using the proper Rc primitives to express that the sun has multiple owners.
+
+// I AM NOT DONE
+use std::rc::Rc;
+
+#[derive(Debug)]
+struct Sun {}
+
+#[derive(Debug)]
+enum Planet {
+    Mercury(Rc<Sun>),
+    Venus(Rc<Sun>),
+    Earth(Rc<Sun>),
+    Mars(Rc<Sun>),
+    Jupiter(Rc<Sun>),
+    Saturn(Rc<Sun>),
+    Uranus(Rc<Sun>),
+    Neptune(Rc<Sun>),
+}
+
+impl Planet {
+    fn details(&self) {
+        println!("Hi from {:?}!", self)
+    }
+}
+
+fn main() {
+    let sun = Rc::new(Sun {});
+    println!("reference count = {}", Rc::strong_count(&sun)); // 1 reference
+
+    let mercury = Planet::Mercury(Rc::clone(&sun));
+    println!("reference count = {}", Rc::strong_count(&sun)); // 2 references
+    mercury.details();
+
+    let venus = Planet::Venus(Rc::clone(&sun));
+    println!("reference count = {}", Rc::strong_count(&sun)); // 3 references
+    venus.details();
+
+    let earth = Planet::Earth(Rc::clone(&sun));
+    println!("reference count = {}", Rc::strong_count(&sun)); // 4 references
+    earth.details();
+
+    let mars = Planet::Mars(Rc::clone(&sun));
+    println!("reference count = {}", Rc::strong_count(&sun)); // 5 references
+    mars.details();
+
+    let jupiter = Planet::Jupiter(Rc::clone(&sun));
+    println!("reference count = {}", Rc::strong_count(&sun)); // 6 references
+    jupiter.details();
+
+    // TODO
+    let saturn = Planet::Saturn(Rc::new(Sun {}));
+    println!("reference count = {}", Rc::strong_count(&sun)); // 7 references
+    saturn.details();
+
+    // TODO
+    let uranus = Planet::Uranus(Rc::new(Sun {}));
+    println!("reference count = {}", Rc::strong_count(&sun)); // 8 references
+    uranus.details();
+
+    // TODO
+    let neptune = Planet::Neptune(Rc::new(Sun {}));
+    println!("reference count = {}", Rc::strong_count(&sun)); // 9 references
+    neptune.details();
+
+    assert_eq!(Rc::strong_count(&sun), 9);
+
+    drop(neptune);
+    println!("reference count = {}", Rc::strong_count(&sun)); // 8 references
+
+    drop(uranus);
+    println!("reference count = {}", Rc::strong_count(&sun)); // 7 references
+
+    drop(saturn);
+    println!("reference count = {}", Rc::strong_count(&sun)); // 6 references
+
+    drop(jupiter);
+    println!("reference count = {}", Rc::strong_count(&sun)); // 5 references
+
+    drop(mars);
+    println!("reference count = {}", Rc::strong_count(&sun)); // 4 references
+
+    // TODO
+    println!("reference count = {}", Rc::strong_count(&sun)); // 3 references
+
+    // TODO
+    println!("reference count = {}", Rc::strong_count(&sun)); // 2 references
+
+    // TODO
+    println!("reference count = {}", Rc::strong_count(&sun)); // 1 reference
+
+    assert_eq!(Rc::strong_count(&sun), 1);
+}

exercises/strings/strings3.rs

@@ -4,7 +4,7 @@
 // I AM NOT DONE
 
 fn trim_me(input: &str) -> String {
-    // TODO: Remove whitespace from the end of a string!
+    // TODO: Remove whitespace from both ends of a string!
     ???
 }
 

exercises/traits/traits4.rs

@@ -1,7 +1,7 @@
 // traits4.rs
 //
 // Your task is to replace the '??' sections so the code compiles.
-// Don't change any line other than 21.
+// Don't change any line other than the marked one.
 // Execute `rustlings hint traits4` or use the `hint` watch subcommand for a hint.
 
 // I AM NOT DONE
@@ -19,6 +19,7 @@ struct OtherSoftware {}
 impl Licensed for SomeSoftware {}
 impl Licensed for OtherSoftware {}
 
+// YOU MAY ONLY CHANGE THE NEXT LINE
 fn compare_license_types(software: ??, software_two: ??) -> bool {
     software.licensing_info() == software_two.licensing_info()
 }

exercises/traits/traits5.rs

@@ -1,7 +1,7 @@
 // traits5.rs
 //
 // Your task is to replace the '??' sections so the code compiles.
-// Don't change any line other than 27.
+// Don't change any line other than the marked one.
 // Execute `rustlings hint traits5` or use the `hint` watch subcommand for a hint.
 
 // I AM NOT DONE
@@ -18,15 +18,20 @@ pub trait OtherTrait {
     }
 }
 
-struct SomeStruct {
-    name: String,
-}
+struct SomeStruct {}
+struct OtherStruct {}
 
 impl SomeTrait for SomeStruct {}
 impl OtherTrait for SomeStruct {}
+impl SomeTrait for OtherStruct {}
+impl OtherTrait for OtherStruct {}
 
+// YOU MAY ONLY CHANGE THE NEXT LINE
 fn some_func(item: ??) -> bool {
     item.some_function() && item.other_function()
 }
 
-fn main() {}
+fn main() {
+    some_func(SomeStruct {});
+    some_func(OtherStruct {});
+}

info.toml

@@ -63,7 +63,7 @@ name = "variables5"
 path = "exercises/variables/variables5.rs"
 mode = "compile"
 hint = """
-In variables3 we already learned how to make an immutable variable mutable
+In variables4 we already learned how to make an immutable variable mutable
 using a special keyword. Unfortunately this doesn't help us much in this exercise
 because we want to assign a different typed value to an existing variable. Sometimes
 you may also like to reuse existing variable names because you are just converting
@@ -123,8 +123,8 @@ name = "functions4"
 path = "exercises/functions/functions4.rs"
 mode = "compile"
 hint = """
-The error message points to line 14 and says it expects a type after the
-`->`. This is where the function's return type should be-- take a look at
+The error message points to line 17 and says it expects a type after the
+`->`. This is where the function's return type should be -- take a look at
 the `is_even` function for an example!
 
 Also: Did you figure out that, technically, u32 would be the more fitting type
@@ -545,7 +545,7 @@ is the easiest, but how do you do it safely so that it doesn't panic in your fac
 [[exercises]]
 name = "options2"
 path = "exercises/options/options2.rs"
-mode = "compile"
+mode = "test"
 hint = """
 check out:
 https://doc.rust-lang.org/rust-by-example/flow_control/if_let.html
@@ -732,7 +732,7 @@ name = "traits5"
 path = "exercises/traits/traits5.rs"
 mode = "compile"
 hint = """
-To ensure a paramter implements multiple traits use the '+ syntax'. Try replacing the
+To ensure a parameter implements multiple traits use the '+ syntax'. Try replacing the
 '??' with 'impl <> + <>'.
 
 See the documentation at: https://doc.rust-lang.org/book/ch10-02-traits.html#specifying-multiple-trait-bounds-with-the--syntax
@@ -746,7 +746,7 @@ path = "exercises/quiz3.rs"
 mode = "test"
 hint = """
 To find the best solution to this challenge you're going to need to think back to your
-knowledge of traits, specifically Trait Bound Syntax -  you may also need this: "use std::fmt::Display;""""
+knowledge of traits, specifically Trait Bound Syntax -  you may also need this: `use std::fmt::Display;`."""
 
 # TESTS
 
@@ -795,7 +795,10 @@ name = "lifetimes2"
 path = "exercises/lifetimes/lifetimes2.rs"
 mode = "compile"
 hint = """
-What is the compiler checking? How could you change how long an owned variable lives?"""
+Remember that the generic lifetime 'a will get the concrete lifetime that is equal to the smaller of the lifetimes of x and y.
+You can take at least two paths to achieve the desired result while keeping the inner block:
+1. Move the string2 declaration to make it live as long as string1 (how is result declared?)
+2. Move println! into the inner block"""
 
 [[exercises]]
 name = "lifetimes3"
@@ -929,6 +932,31 @@ is too much of a struggle, consider reading through all of Chapter 16 in the boo
 https://doc.rust-lang.org/stable/book/ch16-00-concurrency.html
 """
 
+[[exercises]]
+name = "rc1"
+path = "exercises/standard_library_types/rc1.rs"
+mode = "compile"
+hint = """
+This is a straightforward exercise to use the Rc<T> type. Each Planet has
+ownership of the Sun, and uses Rc::clone() to increment the reference count of the Sun.
+After using drop() to move the Planets out of scope individually, the reference count goes down.
+In the end the sun only has one reference again, to itself. See more at:
+https://doc.rust-lang.org/book/ch15-04-rc.html
+
+* Unfortunately Pluto is no longer considered a planet :(
+"""
+
+[[exercises]]
+name = "cow1"
+path = "exercises/standard_library_types/cow1.rs"
+mode = "compile"
+hint = """
+Since the vector is already owned, the `Cow` type doesn't need to clone it.
+
+Checkout https://doc.rust-lang.org/std/borrow/enum.Cow.html for documentation
+on the `Cow` type.
+"""
+
 # THREADS
 
 [[exercises]]
@@ -984,8 +1012,8 @@ hint = """
 An alternate way to handle concurrency between threads is to use
 a mpsc (multiple producer, single consumer) channel to communicate.
 With both a sending end and a receiving end, it's possible to
-send values in one thread and receieve them in another.
-Multiple producers are possibile by using clone() to create a duplicate
+send values in one thread and receive them in another.
+Multiple producers are possible by using clone() to create a duplicate
 of the original sending end.
 See https://doc.rust-lang.org/book/ch16-02-message-passing.html for more info.
 """

src/main.rs

@@ -1,6 +1,6 @@
 use crate::exercise::{Exercise, ExerciseList};
 use crate::project::RustAnalyzerProject;
-use crate::run::run;
+use crate::run::{reset, run};
 use crate::verify::verify;
 use argh::FromArgs;
 use console::Emoji;
@@ -26,7 +26,7 @@ mod run;
 mod verify;
 
 // In sync with crate version
-const VERSION: &str = "5.0.0";
+const VERSION: &str = "5.2.1";
 
 #[derive(FromArgs, PartialEq, Debug)]
 /// Rustlings is a collection of small exercises to get you used to writing and reading Rust code
@@ -47,6 +47,7 @@ enum Subcommands {
     Verify(VerifyArgs),
     Watch(WatchArgs),
     Run(RunArgs),
+    Reset(ResetArgs),
     Hint(HintArgs),
     List(ListArgs),
     Lsp(LspArgs),
@@ -71,6 +72,15 @@ struct RunArgs {
     name: String,
 }
 
+#[derive(FromArgs, PartialEq, Debug)]
+#[argh(subcommand, name = "reset")]
+/// Resets a single exercise using "git stash -- <filename>"
+struct ResetArgs {
+    #[argh(positional)]
+    /// the name of the exercise
+    name: String,
+}
+
 #[derive(FromArgs, PartialEq, Debug)]
 #[argh(subcommand, name = "hint")]
 /// Returns a hint for the given exercise
@@ -85,7 +95,6 @@ struct HintArgs {
 /// Enable rust-analyzer for exercises
 struct LspArgs {}
 
-
 #[derive(FromArgs, PartialEq, Debug)]
 #[argh(subcommand, name = "list")]
 /// Lists the exercises available in Rustlings
@@ -164,7 +173,9 @@ fn main() {
                     "Pending"
                 };
                 let solve_cond = {
-                    (e.looks_done() && subargs.solved) || (!e.looks_done() && subargs.unsolved) || (!subargs.solved && !subargs.unsolved)
+                    (e.looks_done() && subargs.solved)
+                        || (!e.looks_done() && subargs.unsolved)
+                        || (!subargs.solved && !subargs.unsolved)
                 };
                 if solve_cond && (filter_cond || subargs.filter.is_none()) {
                     let line = if subargs.paths {
@@ -205,6 +216,12 @@ fn main() {
             run(exercise, verbose).unwrap_or_else(|_| std::process::exit(1));
         }
 
+        Subcommands::Reset(subargs) => {
+            let exercise = find_exercise(&subargs.name, &exercises);
+
+            reset(exercise).unwrap_or_else(|_| std::process::exit(1));
+        }
+
         Subcommands::Hint(subargs) => {
             let exercise = find_exercise(&subargs.name, &exercises);
 
@@ -212,7 +229,8 @@ fn main() {
         }
 
         Subcommands::Verify(_subargs) => {
-            verify(&exercises, (0, exercises.len()), verbose).unwrap_or_else(|_| std::process::exit(1));
+            verify(&exercises, (0, exercises.len()), verbose)
+                .unwrap_or_else(|_| std::process::exit(1));
         }
 
         Subcommands::Lsp(_subargs) => {
@@ -236,12 +254,18 @@ fn main() {
 
         Subcommands::Watch(_subargs) => match watch(&exercises, verbose) {
             Err(e) => {
-                println!("Error: Could not watch your progress. Error message was {:?}.", e);
+                println!(
+                    "Error: Could not watch your progress. Error message was {:?}.",
+                    e
+                );
                 println!("Most likely you've run out of disk space or your 'inotify limit' has been reached.");
                 std::process::exit(1);
             }
             Ok(WatchStatus::Finished) => {
-                println!("{emoji} All exercises completed! {emoji}", emoji = Emoji("🎉", "★"));
+                println!(
+                    "{emoji} All exercises completed! {emoji}",
+                    emoji = Emoji("🎉", "★")
+                );
                 println!("\n{}\n", FENISH_LINE);
             }
             Ok(WatchStatus::Unfinished) => {
@@ -252,8 +276,10 @@ fn main() {
     }
 }
 
-
-fn spawn_watch_shell(failed_exercise_hint: &Arc<Mutex<Option<String>>>, should_quit: Arc<AtomicBool>) {
+fn spawn_watch_shell(
+    failed_exercise_hint: &Arc<Mutex<Option<String>>>,
+    should_quit: Arc<AtomicBool>,
+) {
     let failed_exercise_hint = Arc::clone(failed_exercise_hint);
     println!("Welcome to watch mode! You can type 'help' to get an overview of the commands you can use here.");
     thread::spawn(move || loop {
@@ -290,16 +316,22 @@ fn spawn_watch_shell(failed_exercise_hint: &Arc<Mutex<Option<String>>>, should_q
 
 fn find_exercise<'a>(name: &str, exercises: &'a [Exercise]) -> &'a Exercise {
     if name.eq("next") {
-        exercises.iter().find(|e| !e.looks_done()).unwrap_or_else(|| {
-            println!("🎉 Congratulations! You have done all the exercises!");
-            println!("🔚 There are no more exercises to do next!");
-            std::process::exit(1)
-        })
+        exercises
+            .iter()
+            .find(|e| !e.looks_done())
+            .unwrap_or_else(|| {
+                println!("🎉 Congratulations! You have done all the exercises!");
+                println!("🔚 There are no more exercises to do next!");
+                std::process::exit(1)
+            })
     } else {
-        exercises.iter().find(|e| e.name == name).unwrap_or_else(|| {
-            println!("No exercise found for '{}'!", name);
-            std::process::exit(1)
-        })
+        exercises
+            .iter()
+            .find(|e| e.name == name)
+            .unwrap_or_else(|| {
+                println!("No exercise found for '{}'!", name);
+                std::process::exit(1)
+            })
     }
 }
 
@@ -337,8 +369,13 @@ fn watch(exercises: &[Exercise], verbose: bool) -> notify::Result<WatchStatus> {
                         let filepath = b.as_path().canonicalize().unwrap();
                         let pending_exercises = exercises
                             .iter()
-                            .find(|e| filepath.ends_with(&e.path)).into_iter()
-                            .chain(exercises.iter().filter(|e| !e.looks_done() && !filepath.ends_with(&e.path)));
+                            .find(|e| filepath.ends_with(&e.path))
+                            .into_iter()
+                            .chain(
+                                exercises
+                                    .iter()
+                                    .filter(|e| !e.looks_done() && !filepath.ends_with(&e.path)),
+                            );
                         let num_done = exercises.iter().filter(|e| e.looks_done()).count();
                         clear_screen();
                         match verify(pending_exercises, (num_done, exercises.len()), verbose) {

src/run.rs

@@ -1,3 +1,5 @@
+use std::process::Command;
+
 use crate::exercise::{Exercise, Mode};
 use crate::verify::test;
 use indicatif::ProgressBar;
@@ -15,6 +17,19 @@ pub fn run(exercise: &Exercise, verbose: bool) -> Result<(), ()> {
     Ok(())
 }
 
+// Resets the exercise by stashing the changes.
+pub fn reset(exercise: &Exercise) -> Result<(), ()> {
+    let command = Command::new("git")
+        .args(["stash", "--"])
+        .arg(&exercise.path)
+        .spawn();
+
+    match command {
+        Ok(_) => Ok(()),
+        Err(_) => Err(()),
+    }
+}
+
 // Invoke the rust compiler on the path of the given exercise
 // and run the ensuing binary.
 // This is strictly for non-test binaries, so output is displayed

tests/integration_tests.rs

@@ -110,6 +110,27 @@ fn run_single_test_no_exercise() {
         .code(1);
 }
 
+#[test]
+fn reset_single_exercise() {
+    Command::cargo_bin("rustlings")
+        .unwrap()
+        .args(&["reset", "intro1"])
+        .assert()
+        .code(0);
+}
+
+#[test]
+fn reset_no_exercise() {
+    Command::cargo_bin("rustlings")
+        .unwrap()
+        .arg("reset")
+        .assert()
+        .code(1)
+        .stderr(predicates::str::contains(
+            "positional arguments not provided",
+        ));
+}
+
 #[test]
 fn get_hint_for_single_test() {
     Command::cargo_bin("rustlings")
@@ -126,7 +147,7 @@ fn all_exercises_require_confirmation() {
     for exercise in glob("exercises/**/*.rs").unwrap() {
         let path = exercise.unwrap();
         if path.file_name().unwrap() == "mod.rs" {
-            continue
+            continue;
         }
         let source = {
             let mut file = File::open(&path).unwrap();
@@ -176,7 +197,7 @@ fn run_single_test_success_with_output() {
         .current_dir("tests/fixture/success/")
         .assert()
         .code(0)
-        .stdout(predicates::str::contains("THIS TEST TOO SHALL PAS"));
+        .stdout(predicates::str::contains("THIS TEST TOO SHALL PASS"));
 }
 
 #[test]
@@ -187,7 +208,7 @@ fn run_single_test_success_without_output() {
         .current_dir("tests/fixture/success/")
         .assert()
         .code(0)
-        .stdout(predicates::str::contains("THIS TEST TOO SHALL PAS").not());
+        .stdout(predicates::str::contains("THIS TEST TOO SHALL PASS").not());
 }
 
 #[test]