Merge pull request #1535 from robertefry/comment_cleanup

docs: cleanup the explanation paragraphs at the start of each exercise.

exercises/clippy/clippy1.rs

@@ -1,10 +1,13 @@
 // clippy1.rs
-// The Clippy tool is a collection of lints to analyze your code
-// so you can catch common mistakes and improve your Rust code.
 //
-// For these exercises the code will fail to compile when there are clippy warnings
-// check clippy's suggestions from the output to solve the exercise.
-// Execute `rustlings hint clippy1` or use the `hint` watch subcommand for a hint.
+// The Clippy tool is a collection of lints to analyze your code so you can
+// catch common mistakes and improve your Rust code.
+//
+// For these exercises the code will fail to compile when there are clippy
+// warnings check clippy's suggestions from the output to solve the exercise.
+//
+// Execute `rustlings hint clippy1` or use the `hint` watch subcommand for a
+// hint.
 
 // I AM NOT DONE
 

exercises/clippy/clippy2.rs

@@ -1,5 +1,7 @@
 // clippy2.rs
-// Execute `rustlings hint clippy2` or use the `hint` watch subcommand for a hint.
+// 
+// Execute `rustlings hint clippy2` or use the `hint` watch subcommand for a
+// hint.
 
 // I AM NOT DONE
 

exercises/clippy/clippy3.rs

@@ -1,5 +1,8 @@
 // clippy3.rs
+// 
 // Here's a couple more easy Clippy fixes, so you can see its utility.
+//
+// Execute `rustlings hint clippy3` or use the `hint` watch subcommand for a hint.
 
 // I AM NOT DONE
 

exercises/conversions/as_ref_mut.rs

@@ -1,7 +1,11 @@
-// AsRef and AsMut allow for cheap reference-to-reference conversions.
-// Read more about them at https://doc.rust-lang.org/std/convert/trait.AsRef.html
-// and https://doc.rust-lang.org/std/convert/trait.AsMut.html, respectively.
-// Execute `rustlings hint as_ref_mut` or use the `hint` watch subcommand for a hint.
+// as_ref_mut.rs
+//
+// AsRef and AsMut allow for cheap reference-to-reference conversions. Read more
+// about them at https://doc.rust-lang.org/std/convert/trait.AsRef.html and
+// https://doc.rust-lang.org/std/convert/trait.AsMut.html, respectively.
+//
+// Execute `rustlings hint as_ref_mut` or use the `hint` watch subcommand for a
+// hint.
 
 // I AM NOT DONE
 

exercises/conversions/from_into.rs

@@ -1,7 +1,11 @@
-// The From trait is used for value-to-value conversions.
-// If From is implemented correctly for a type, the Into trait should work conversely.
-// You can read more about it at https://doc.rust-lang.org/std/convert/trait.From.html
-// Execute `rustlings hint from_into` or use the `hint` watch subcommand for a hint.
+// from_into.rs
+//
+// The From trait is used for value-to-value conversions. If From is implemented
+// correctly for a type, the Into trait should work conversely. You can read
+// more about it at https://doc.rust-lang.org/std/convert/trait.From.html
+//
+// Execute `rustlings hint from_into` or use the `hint` watch subcommand for a
+// hint.
 
 #[derive(Debug)]
 struct Person {
@@ -20,20 +24,21 @@ impl Default for Person {
     }
 }
 
-// Your task is to complete this implementation
-// in order for the line `let p = Person::from("Mark,20")` to compile
-// Please note that you'll need to parse the age component into a `usize`
-// with something like `"4".parse::<usize>()`. The outcome of this needs to
-// be handled appropriately.
+// Your task is to complete this implementation in order for the line `let p =
+// Person::from("Mark,20")` to compile Please note that you'll need to parse the
+// age component into a `usize` with something like `"4".parse::<usize>()`. The
+// outcome of this needs to be handled appropriately.
 //
 // Steps:
-// 1. If the length of the provided string is 0, then return the default of Person
-// 2. Split the given string on the commas present in it
-// 3. Extract the first element from the split operation and use it as the name
-// 4. If the name is empty, then return the default of Person
-// 5. Extract the other element from the split operation and parse it into a `usize` as the age
-// If while parsing the age, something goes wrong, then return the default of Person
-// Otherwise, then return an instantiated Person object with the results
+// 1. If the length of the provided string is 0, then return the default of
+//    Person.
+// 2. Split the given string on the commas present in it.
+// 3. Extract the first element from the split operation and use it as the name.
+// 4. If the name is empty, then return the default of Person.
+// 5. Extract the other element from the split operation and parse it into a
+//    `usize` as the age.
+// If while parsing the age, something goes wrong, then return the default of
+// Person Otherwise, then return an instantiated Person object with the results
 
 // I AM NOT DONE
 
@@ -77,7 +82,8 @@ mod tests {
     }
     #[test]
     fn test_bad_age() {
-        // Test that "Mark,twenty" will return the default person due to an error in parsing age
+        // Test that "Mark,twenty" will return the default person due to an
+        // error in parsing age
         let p = Person::from("Mark,twenty");
         assert_eq!(p.name, "John");
         assert_eq!(p.age, 30);

exercises/conversions/from_str.rs

@@ -1,10 +1,13 @@
 // from_str.rs
-// This is similar to from_into.rs, but this time we'll implement `FromStr`
-// and return errors instead of falling back to a default value.
-// Additionally, upon implementing FromStr, you can use the `parse` method
-// on strings to generate an object of the implementor type.
-// You can read more about it at https://doc.rust-lang.org/std/str/trait.FromStr.html
-// Execute `rustlings hint from_str` or use the `hint` watch subcommand for a hint.
+//
+// This is similar to from_into.rs, but this time we'll implement `FromStr` and
+// return errors instead of falling back to a default value. Additionally, upon
+// implementing FromStr, you can use the `parse` method on strings to generate
+// an object of the implementor type. You can read more about it at
+// https://doc.rust-lang.org/std/str/trait.FromStr.html
+//
+// Execute `rustlings hint from_str` or use the `hint` watch subcommand for a
+// hint.
 
 use std::num::ParseIntError;
 use std::str::FromStr;
@@ -33,15 +36,18 @@ enum ParsePersonError {
 // Steps:
 // 1. If the length of the provided string is 0, an error should be returned
 // 2. Split the given string on the commas present in it
-// 3. Only 2 elements should be returned from the split, otherwise return an error
+// 3. Only 2 elements should be returned from the split, otherwise return an
+//    error
 // 4. Extract the first element from the split operation and use it as the name
-// 5. Extract the other element from the split operation and parse it into a `usize` as the age
-//    with something like `"4".parse::<usize>()`
-// 6. If while extracting the name and the age something goes wrong, an error should be returned
+// 5. Extract the other element from the split operation and parse it into a
+//    `usize` as the age with something like `"4".parse::<usize>()`
+// 6. If while extracting the name and the age something goes wrong, an error
+//    should be returned
 // If everything goes well, then return a Result of a Person object
 //
-// As an aside: `Box<dyn Error>` implements `From<&'_ str>`. This means that if you want to return a
-// string error message, you can do so via just using return `Err("my error message".into())`.
+// As an aside: `Box<dyn Error>` implements `From<&'_ str>`. This means that if
+// you want to return a string error message, you can do so via just using
+// return `Err("my error message".into())`.
 
 impl FromStr for Person {
     type Err = ParsePersonError;

exercises/conversions/try_from_into.rs

@@ -1,9 +1,13 @@
 // try_from_into.rs
-// TryFrom is a simple and safe type conversion that may fail in a controlled way under some circumstances.
-// Basically, this is the same as From. The main difference is that this should return a Result type
-// instead of the target type itself.
-// You can read more about it at https://doc.rust-lang.org/std/convert/trait.TryFrom.html
-// Execute `rustlings hint try_from_into` or use the `hint` watch subcommand for a hint.
+//
+// TryFrom is a simple and safe type conversion that may fail in a controlled
+// way under some circumstances. Basically, this is the same as From. The main
+// difference is that this should return a Result type instead of the target
+// type itself. You can read more about it at
+// https://doc.rust-lang.org/std/convert/trait.TryFrom.html
+//
+// Execute `rustlings hint try_from_into` or use the `hint` watch subcommand for
+// a hint.
 
 use std::convert::{TryFrom, TryInto};
 
@@ -25,14 +29,13 @@ enum IntoColorError {
 
 // I AM NOT DONE
 
-// Your task is to complete this implementation
-// and return an Ok result of inner type Color.
-// You need to create an implementation for a tuple of three integers,
-// an array of three integers, and a slice of integers.
+// Your task is to complete this implementation and return an Ok result of inner
+// type Color. You need to create an implementation for a tuple of three
+// integers, an array of three integers, and a slice of integers.
 //
-// Note that the implementation for tuple and array will be checked at compile time,
-// but the slice implementation needs to check the slice length!
-// Also note that correct RGB color values must be integers in the 0..=255 range.
+// Note that the implementation for tuple and array will be checked at compile
+// time, but the slice implementation needs to check the slice length! Also note
+// that correct RGB color values must be integers in the 0..=255 range.
 
 // Tuple implementation
 impl TryFrom<(i16, i16, i16)> for Color {

exercises/conversions/using_as.rs

@@ -1,10 +1,14 @@
-// Type casting in Rust is done via the usage of the `as` operator.
-// Please note that the `as` operator is not only used when type casting.
-// It also helps with renaming imports.
+// using_as.rs
 //
-// The goal is to make sure that the division does not fail to compile
-// and returns the proper type.
-// Execute `rustlings hint using_as` or use the `hint` watch subcommand for a hint.
+// Type casting in Rust is done via the usage of the `as` operator. Please note
+// that the `as` operator is not only used when type casting. It also helps with
+// renaming imports.
+//
+// The goal is to make sure that the division does not fail to compile and
+// returns the proper type.
+//
+// Execute `rustlings hint using_as` or use the `hint` watch subcommand for a
+// hint.
 
 // I AM NOT DONE
 

exercises/enums/enums1.rs

@@ -1,4 +1,5 @@
 // enums1.rs
+//
 // No hints this time! ;)
 
 // I AM NOT DONE

exercises/enums/enums2.rs

@@ -1,5 +1,7 @@
 // enums2.rs
-// Execute `rustlings hint enums2` or use the `hint` watch subcommand for a hint.
+//
+// Execute `rustlings hint enums2` or use the `hint` watch subcommand for a
+// hint.
 
 // I AM NOT DONE
 

exercises/enums/enums3.rs

@@ -1,6 +1,9 @@
 // enums3.rs
+//
 // Address all the TODOs to make the tests pass!
-// Execute `rustlings hint enums3` or use the `hint` watch subcommand for a hint.
+//
+// Execute `rustlings hint enums3` or use the `hint` watch subcommand for a
+// hint.
 
 // I AM NOT DONE
 
@@ -36,8 +39,10 @@ impl State {
     }
 
     fn process(&mut self, message: Message) {
-        // TODO: create a match expression to process the different message variants
-        // Remember: When passing a tuple as a function argument, you'll need extra parentheses: fn function((t, u, p, l, e))
+        // TODO: create a match expression to process the different message
+        // variants
+        // Remember: When passing a tuple as a function argument, you'll need
+        // extra parentheses: fn function((t, u, p, l, e))
     }
 }
 

exercises/error_handling/errors1.rs

@@ -1,9 +1,13 @@
 // errors1.rs
-// This function refuses to generate text to be printed on a nametag if
-// you pass it an empty string. It'd be nicer if it explained what the problem
-// was, instead of just sometimes returning `None`. Thankfully, Rust has a similar
-// construct to `Option` that can be used to express error conditions. Let's use it!
-// Execute `rustlings hint errors1` or use the `hint` watch subcommand for a hint.
+//
+// This function refuses to generate text to be printed on a nametag if you pass
+// it an empty string. It'd be nicer if it explained what the problem was,
+// instead of just sometimes returning `None`. Thankfully, Rust has a similar
+// construct to `Option` that can be used to express error conditions. Let's use
+// it!
+//
+// Execute `rustlings hint errors1` or use the `hint` watch subcommand for a
+// hint.
 
 // I AM NOT DONE
 

exercises/error_handling/errors2.rs

@@ -1,21 +1,23 @@
 // errors2.rs
+//
 // Say we're writing a game where you can buy items with tokens. All items cost
 // 5 tokens, and whenever you purchase items there is a processing fee of 1
-// token. A player of the game will type in how many items they want to buy,
-// and the `total_cost` function will calculate the total cost of the tokens.
-// Since the player typed in the quantity, though, we get it as a string-- and
-// they might have typed anything, not just numbers!
-
+// token. A player of the game will type in how many items they want to buy, and
+// the `total_cost` function will calculate the total cost of the tokens. Since
+// the player typed in the quantity, though, we get it as a string-- and they
+// might have typed anything, not just numbers!
+//
 // Right now, this function isn't handling the error case at all (and isn't
-// handling the success case properly either). What we want to do is:
-// if we call the `parse` function on a string that is not a number, that
-// function will return a `ParseIntError`, and in that case, we want to
-// immediately return that error from our function and not try to multiply
-// and add.
-
-// There are at least two ways to implement this that are both correct-- but
-// one is a lot shorter!
-// Execute `rustlings hint errors2` or use the `hint` watch subcommand for a hint.
+// handling the success case properly either). What we want to do is: if we call
+// the `parse` function on a string that is not a number, that function will
+// return a `ParseIntError`, and in that case, we want to immediately return
+// that error from our function and not try to multiply and add.
+//
+// There are at least two ways to implement this that are both correct-- but one
+// is a lot shorter!
+//
+// Execute `rustlings hint errors2` or use the `hint` watch subcommand for a
+// hint.
 
 // I AM NOT DONE
 

exercises/error_handling/errors3.rs

@@ -1,8 +1,11 @@
 // errors3.rs
+//
 // This is a program that is trying to use a completed version of the
 // `total_cost` function from the previous exercise. It's not working though!
 // Why not? What should we do to fix it?
-// Execute `rustlings hint errors3` or use the `hint` watch subcommand for a hint.
+//
+// Execute `rustlings hint errors3` or use the `hint` watch subcommand for a
+// hint.
 
 // I AM NOT DONE
 

exercises/error_handling/errors4.rs

@@ -1,5 +1,7 @@
 // errors4.rs
-// Execute `rustlings hint errors4` or use the `hint` watch subcommand for a hint.
+//
+// Execute `rustlings hint errors4` or use the `hint` watch subcommand for a
+// hint.
 
 // I AM NOT DONE
 

exercises/error_handling/errors5.rs

@@ -1,20 +1,26 @@
 // errors5.rs
-
+//
 // This program uses an altered version of the code from errors4.
-
-// 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
-// the compiler looks for on any value used in that context. For this exercise, that context is the potential errors
-// which can be returned in a Result.
-
-// What can we use to describe both errors? In other words, is there a trait which both errors implement?
-
-// Execute `rustlings hint errors5` or use the `hint` watch subcommand for a hint.
+//
+// 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 the compiler looks for on any value used in that context. For this
+// exercise, that context is the potential errors which can be returned in a
+// Result.
+//
+// What can we use to describe both errors? In other words, is there a trait
+// which both errors implement?
+//
+// Execute `rustlings hint errors5` or use the `hint` watch subcommand for a
+// hint.
 
 // I AM NOT DONE
 

exercises/error_handling/errors6.rs

@@ -1,12 +1,13 @@
 // errors6.rs
-
+//
 // Using catch-all error types like `Box<dyn error::Error>` isn't recommended
 // for library code, where callers might want to make decisions based on the
-// error content, instead of printing it out or propagating it further. Here,
-// we define a custom error type to make it possible for callers to decide
-// what to do next when our function returns an error.
-
-// Execute `rustlings hint errors6` or use the `hint` watch subcommand for a hint.
+// error content, instead of printing it out or propagating it further. Here, we
+// define a custom error type to make it possible for callers to decide what to
+// do next when our function returns an error.
+//
+// Execute `rustlings hint errors6` or use the `hint` watch subcommand for a
+// hint.
 
 // I AM NOT DONE
 

exercises/functions/functions1.rs

@@ -1,5 +1,7 @@
 // functions1.rs
-// Execute `rustlings hint functions1` or use the `hint` watch subcommand for a hint.
+//
+// Execute `rustlings hint functions1` or use the `hint` watch subcommand for a
+// hint.
 
 // I AM NOT DONE
 

exercises/functions/functions2.rs

@@ -1,5 +1,7 @@
 // functions2.rs
-// Execute `rustlings hint functions2` or use the `hint` watch subcommand for a hint.
+//
+// Execute `rustlings hint functions2` or use the `hint` watch subcommand for a
+// hint.
 
 // I AM NOT DONE
 

exercises/functions/functions3.rs

@@ -1,5 +1,7 @@
 // functions3.rs
-// Execute `rustlings hint functions3` or use the `hint` watch subcommand for a hint.
+//
+// Execute `rustlings hint functions3` or use the `hint` watch subcommand for a
+// hint.
 
 // I AM NOT DONE
 

exercises/functions/functions4.rs

@@ -1,11 +1,12 @@
 // functions4.rs
-// Execute `rustlings hint functions4` or use the `hint` watch subcommand for a hint.
-
-// This store is having a sale where if the price is an even number, you get
-// 10 Rustbucks off, but if it's an odd number, it's 3 Rustbucks off.
-// (Don't worry about the function bodies themselves, we're only interested
-// in the signatures for now. If anything, this is a good way to peek ahead
-// to future exercises!)
+//
+// This store is having a sale where if the price is an even number, you get 10
+// Rustbucks off, but if it's an odd number, it's 3 Rustbucks off. (Don't worry
+// about the function bodies themselves, we're only interested in the signatures
+// for now. If anything, this is a good way to peek ahead to future exercises!)
+//
+// Execute `rustlings hint functions4` or use the `hint` watch subcommand for a
+// hint.
 
 // I AM NOT DONE
 

exercises/functions/functions5.rs

@@ -1,5 +1,7 @@
 // functions5.rs
-// Execute `rustlings hint functions5` or use the `hint` watch subcommand for a hint.
+//
+// Execute `rustlings hint functions5` or use the `hint` watch subcommand for a
+// hint.
 
 // I AM NOT DONE
 

exercises/generics/generics1.rs

@@ -1,7 +1,10 @@
-// This shopping list program isn't compiling!
-// Use your knowledge of generics to fix it.
-
-// Execute `rustlings hint generics1` or use the `hint` watch subcommand for a hint.
+// generics1.rs
+//
+// This shopping list program isn't compiling! Use your knowledge of generics to
+// fix it.
+//
+// Execute `rustlings hint generics1` or use the `hint` watch subcommand for a
+// hint.
 
 // I AM NOT DONE
 

exercises/generics/generics2.rs

@@ -1,7 +1,10 @@
+// generics2.rs
+//
 // This powerful wrapper provides the ability to store a positive integer value.
 // Rewrite it using generics so that it supports wrapping ANY type.
-
-// Execute `rustlings hint generics2` or use the `hint` watch subcommand for a hint.
+//
+// Execute `rustlings hint generics2` or use the `hint` watch subcommand for a
+// hint.
 
 // I AM NOT DONE
 

exercises/hashmaps/hashmaps1.rs

@@ -1,14 +1,15 @@
 // hashmaps1.rs
-// A basket of fruits in the form of a hash map needs to be defined.
-// The key represents the name of the fruit and the value represents
-// how many of that particular fruit is in the basket. You have to put
-// at least three different types of fruits (e.g apple, banana, mango)
-// in the basket and the total count of all the fruits should be at
-// least five.
+//
+// A basket of fruits in the form of a hash map needs to be defined. The key
+// represents the name of the fruit and the value represents how many of that
+// particular fruit is in the basket. You have to put at least three different
+// types of fruits (e.g apple, banana, mango) in the basket and the total count
+// of all the fruits should be at least five.
 //
 // Make me compile and pass the tests!
 //
-// Execute `rustlings hint hashmaps1` or use the `hint` watch subcommand for a hint.
+// Execute `rustlings hint hashmaps1` or use the `hint` watch subcommand for a
+// hint.
 
 // I AM NOT DONE
 

exercises/hashmaps/hashmaps2.rs

@@ -1,17 +1,18 @@
 // hashmaps2.rs
-// We're collecting different fruits to bake a delicious fruit cake.
-// For this, we have a basket, which we'll represent in the form of a hash
-// map. The key represents the name of each fruit we collect and the value
-// represents how many of that particular fruit we have collected.
-// Three types of fruits - Apple (4), Mango (2) and Lychee (5) are already
-// in the basket hash map.
-// You must add fruit to the basket so that there is at least
-// one of each kind and more than 11 in total - we have a lot of mouths to feed.
-// You are not allowed to insert any more of these fruits!
+//
+// We're collecting different fruits to bake a delicious fruit cake. For this,
+// we have a basket, which we'll represent in the form of a hash map. The key
+// represents the name of each fruit we collect and the value represents how
+// many of that particular fruit we have collected. Three types of fruits -
+// Apple (4), Mango (2) and Lychee (5) are already in the basket hash map. You
+// must add fruit to the basket so that there is at least one of each kind and
+// more than 11 in total - we have a lot of mouths to feed. You are not allowed
+// to insert any more of these fruits!
 //
 // Make me pass the tests!
 //
-// Execute `rustlings hint hashmaps2` or use the `hint` watch subcommand for a hint.
+// Execute `rustlings hint hashmaps2` or use the `hint` watch subcommand for a
+// hint.
 
 // I AM NOT DONE
 
@@ -36,9 +37,9 @@ fn fruit_basket(basket: &mut HashMap<Fruit, u32>) {
     ];
 
     for fruit in fruit_kinds {
-        // TODO: Insert new fruits if they are not already present in the basket.
-        // Note that you are not allowed to put any type of fruit that's already
-        // present!
+        // TODO: Insert new fruits if they are not already present in the
+        // basket. Note that you are not allowed to put any type of fruit that's
+        // already present!
     }
 }
 

exercises/hashmaps/hashmaps3.rs

@@ -1,18 +1,18 @@
 // hashmaps3.rs
-
-// A list of scores (one per line) of a soccer match is given. Each line
-// is of the form :
-// <team_1_name>,<team_2_name>,<team_1_goals>,<team_2_goals>
+//
+// A list of scores (one per line) of a soccer match is given. Each line is of
+// the form : "<team_1_name>,<team_2_name>,<team_1_goals>,<team_2_goals>"
 // Example: England,France,4,2 (England scored 4 goals, France 2).
-
-// You have to build a scores table containing the name of the team, goals
-// the team scored, and goals the team conceded. One approach to build
-// the scores table is to use a Hashmap. The solution is partially
-// written to use a Hashmap, complete it to pass the test.
-
+//
+// You have to build a scores table containing the name of the team, goals the
+// team scored, and goals the team conceded. One approach to build the scores
+// table is to use a Hashmap. The solution is partially written to use a
+// Hashmap, complete it to pass the test.
+//
 // Make me pass the tests!
-
-// Execute `rustlings hint hashmaps3` or use the `hint` watch subcommand for a hint.
+//
+// Execute `rustlings hint hashmaps3` or use the `hint` watch subcommand for a
+// hint.
 
 // I AM NOT DONE
 

exercises/if/if1.rs

@@ -1,4 +1,5 @@
 // if1.rs
+//
 // Execute `rustlings hint if1` or use the `hint` watch subcommand for a hint.
 
 // I AM NOT DONE

exercises/if/if2.rs

@@ -1,7 +1,8 @@
 // if2.rs
-
+//
 // Step 1: Make me compile!
 // Step 2: Get the bar_for_fuzz and default_to_baz tests passing!
+//
 // Execute `rustlings hint if2` or use the `hint` watch subcommand for a hint.
 
 // I AM NOT DONE

exercises/intro/intro1.rs

@@ -1,13 +1,17 @@
 // intro1.rs
+//
 // About this `I AM NOT DONE` thing:
 // We sometimes encourage you to keep trying things on a given exercise, even
 // after you already figured it out. If you got everything working and feel
 // ready for the next exercise, remove the `I AM NOT DONE` comment below.
-// Execute `rustlings hint intro1` or use the `hint` watch subcommand for a hint.
 //
-// If you're running this using `rustlings watch`: The exercise file will be reloaded
-// when you change one of the lines below! Try adding a `println!` line, or try changing
-// what it outputs in your terminal. Try removing a semicolon and see what happens!
+// If you're running this using `rustlings watch`: The exercise file will be
+// reloaded when you change one of the lines below! Try adding a `println!`
+// line, or try changing what it outputs in your terminal. Try removing a
+// semicolon and see what happens!
+//
+// Execute `rustlings hint intro1` or use the `hint` watch subcommand for a
+// hint.
 
 // I AM NOT DONE
 

exercises/intro/intro2.rs

@@ -1,6 +1,9 @@
 // intro2.rs
+//
 // Make the code print a greeting to the world.
-// Execute `rustlings hint intro2` or use the `hint` watch subcommand for a hint.
+//
+// Execute `rustlings hint intro2` or use the `hint` watch subcommand for a
+// hint.
 
 // I AM NOT DONE
 

exercises/iterators/iterators1.rs

@@ -1,12 +1,13 @@
 // iterators1.rs
 //
-//  Make me compile by filling in the `???`s
+// When performing operations on elements within a collection, iterators are
+// essential. This module helps you get familiar with the structure of using an
+// iterator and how to go through elements within an iterable collection.
 //
-// When performing operations on elements within a collection, iterators are essential.
-// This module helps you get familiar with the structure of using an iterator and
-// how to go through elements within an iterable collection.
+// Make me compile by filling in the `???`s
 //
-// Execute `rustlings hint iterators1` or use the `hint` watch subcommand for a hint.
+// Execute `rustlings hint iterators1` or use the `hint` watch subcommand for a
+// hint.
 
 // I AM NOT DONE
 

exercises/iterators/iterators2.rs

@@ -1,7 +1,10 @@
 // iterators2.rs
+//
 // In this exercise, you'll learn some of the unique advantages that iterators
 // can offer. Follow the steps to complete the exercise.
-// Execute `rustlings hint iterators2` or use the `hint` watch subcommand for a hint.
+//
+// Execute `rustlings hint iterators2` or use the `hint` watch subcommand for a
+// hint.
 
 // I AM NOT DONE
 

exercises/iterators/iterators3.rs

@@ -1,10 +1,13 @@
 // iterators3.rs
-// This is a bigger exercise than most of the others! You can do it!
-// Here is your mission, should you choose to accept it:
+//
+// This is a bigger exercise than most of the others! You can do it! Here is
+// your mission, should you choose to accept it:
 // 1. Complete the divide function to get the first four tests to pass.
 // 2. Get the remaining tests to pass by completing the result_with_list and
 //    list_of_results functions.
-// Execute `rustlings hint iterators3` or use the `hint` watch subcommand for a hint.
+//
+// Execute `rustlings hint iterators3` or use the `hint` watch subcommand for a
+// hint.
 
 // I AM NOT DONE
 
@@ -26,14 +29,16 @@ pub fn divide(a: i32, b: i32) -> Result<i32, DivisionError> {
     todo!();
 }
 
-// Complete the function and return a value of the correct type so the test passes.
+// Complete the function and return a value of the correct type so the test
+// passes.
 // Desired output: Ok([1, 11, 1426, 3])
 fn result_with_list() -> () {
     let numbers = vec![27, 297, 38502, 81];
     let division_results = numbers.into_iter().map(|n| divide(n, 27));
 }
 
-// Complete the function and return a value of the correct type so the test passes.
+// Complete the function and return a value of the correct type so the test
+// passes.
 // Desired output: [Ok(1), Ok(11), Ok(1426), Ok(3)]
 fn list_of_results() -> () {
     let numbers = vec![27, 297, 38502, 81];

exercises/iterators/iterators4.rs

@@ -1,5 +1,7 @@
 // iterators4.rs
-// Execute `rustlings hint iterators4` or use the `hint` watch subcommand for a hint.
+//
+// Execute `rustlings hint iterators4` or use the `hint` watch subcommand for a
+// hint.
 
 // I AM NOT DONE
 

exercises/iterators/iterators5.rs

@@ -1,4 +1,5 @@
 // iterators5.rs
+//
 // Let's define a simple model to track Rustlings exercise progress. Progress
 // will be modelled using a hash map. The name of the exercise is the key and
 // the progress is the value. Two counting functions were created to count the
@@ -6,7 +7,9 @@
 // functionality using iterators. Try not to use imperative loops (for, while).
 // Only the two iterator methods (count_iterator and count_collection_iterator)
 // need to be modified.
-// Execute `rustlings hint iterators5` or use the `hint` watch subcommand for a hint.
+//
+// Execute `rustlings hint iterators5` or use the `hint` watch subcommand for a
+// hint.
 
 // I AM NOT DONE
 

exercises/lifetimes/lifetimes1.rs

@@ -1,11 +1,12 @@
 // lifetimes1.rs
 //
 // The Rust compiler needs to know how to check whether supplied references are
-// valid, so that it can let the programmer know if a reference is at risk
-// of going out of scope before it is used. Remember, references are borrows
-// and do not own their own data. What if their owner goes out of scope?
+// valid, so that it can let the programmer know if a reference is at risk of
+// going out of scope before it is used. Remember, references are borrows and do
+// not own their own data. What if their owner goes out of scope?
 //
-// Execute `rustlings hint lifetimes1` or use the `hint` watch subcommand for a hint.
+// Execute `rustlings hint lifetimes1` or use the `hint` watch subcommand for a
+// hint.
 
 // I AM NOT DONE
 

exercises/lifetimes/lifetimes2.rs

@@ -1,10 +1,10 @@
 // lifetimes2.rs
 //
-// So if the compiler is just validating the references passed
-// to the annotated parameters and the return type, what do
-// we need to change?
+// So if the compiler is just validating the references passed to the annotated
+// parameters and the return type, what do we need to change?
 //
-// Execute `rustlings hint lifetimes2` or use the `hint` watch subcommand for a hint.
+// Execute `rustlings hint lifetimes2` or use the `hint` watch subcommand for a
+// hint.
 
 // I AM NOT DONE
 

exercises/lifetimes/lifetimes3.rs

@@ -2,7 +2,8 @@
 //
 // Lifetimes are also needed when structs hold references.
 //
-// Execute `rustlings hint lifetimes3` or use the `hint` watch subcommand for a hint.
+// Execute `rustlings hint lifetimes3` or use the `hint` watch subcommand for a
+// hint.
 
 // I AM NOT DONE
 

exercises/macros/macros1.rs

@@ -1,5 +1,7 @@
 // macros1.rs
-// Execute `rustlings hint macros1` or use the `hint` watch subcommand for a hint.
+//
+// Execute `rustlings hint macros1` or use the `hint` watch subcommand for a
+// hint.
 
 // I AM NOT DONE
 

exercises/macros/macros2.rs

@@ -1,5 +1,7 @@
 // macros2.rs
-// Execute `rustlings hint macros2` or use the `hint` watch subcommand for a hint.
+//
+// Execute `rustlings hint macros2` or use the `hint` watch subcommand for a
+// hint.
 
 // I AM NOT DONE
 

exercises/macros/macros3.rs

@@ -1,6 +1,9 @@
 // macros3.rs
+//
 // Make me compile, without taking the macro out of the module!
-// Execute `rustlings hint macros3` or use the `hint` watch subcommand for a hint.
+//
+// Execute `rustlings hint macros3` or use the `hint` watch subcommand for a
+// hint.
 
 // I AM NOT DONE
 

exercises/macros/macros4.rs

@@ -1,5 +1,7 @@
 // macros4.rs
-// Execute `rustlings hint macros4` or use the `hint` watch subcommand for a hint.
+//
+// Execute `rustlings hint macros4` or use the `hint` watch subcommand for a
+// hint.
 
 // I AM NOT DONE
 

exercises/modules/modules1.rs

@@ -1,5 +1,7 @@
 // modules1.rs
-// Execute `rustlings hint modules1` or use the `hint` watch subcommand for a hint.
+//
+// Execute `rustlings hint modules1` or use the `hint` watch subcommand for a
+// hint.
 
 // I AM NOT DONE
 

exercises/modules/modules2.rs

@@ -1,7 +1,11 @@
 // modules2.rs
-// You can bring module paths into scopes and provide new names for them with the
-// 'use' and 'as' keywords. Fix these 'use' statements to make the code compile.
-// Execute `rustlings hint modules2` or use the `hint` watch subcommand for a hint.
+//
+// You can bring module paths into scopes and provide new names for them with
+// the 'use' and 'as' keywords. Fix these 'use' statements to make the code
+// compile.
+//
+// Execute `rustlings hint modules2` or use the `hint` watch subcommand for a
+// hint.
 
 // I AM NOT DONE
 

exercises/modules/modules3.rs

@@ -1,9 +1,12 @@
 // modules3.rs
-// You can use the 'use' keyword to bring module paths from modules from anywhere
-// and especially from the Rust standard library into your scope.
-// Bring SystemTime and UNIX_EPOCH
-// from the std::time module. Bonus style points if you can do it with one line!
-// Execute `rustlings hint modules3` or use the `hint` watch subcommand for a hint.
+//
+// You can use the 'use' keyword to bring module paths from modules from
+// anywhere and especially from the Rust standard library into your scope. Bring
+// SystemTime and UNIX_EPOCH from the std::time module. Bonus style points if
+// you can do it with one line!
+//
+// Execute `rustlings hint modules3` or use the `hint` watch subcommand for a
+// hint.
 
 // I AM NOT DONE
 

exercises/move_semantics/move_semantics1.rs

@@ -1,5 +1,7 @@
 // move_semantics1.rs
-// Execute `rustlings hint move_semantics1` or use the `hint` watch subcommand for a hint.
+//
+// Execute `rustlings hint move_semantics1` or use the `hint` watch subcommand
+// for a hint.
 
 // I AM NOT DONE
 

exercises/move_semantics/move_semantics2.rs

@@ -1,9 +1,11 @@
 // move_semantics2.rs
-// Execute `rustlings hint move_semantics2` or use the `hint` watch subcommand for a hint.
-
+//
 // Expected output:
 // vec0 has length 3, with contents `[22, 44, 66]`
 // vec1 has length 4, with contents `[22, 44, 66, 88]`
+//
+// Execute `rustlings hint move_semantics2` or use the `hint` watch subcommand
+// for a hint.
 
 // I AM NOT DONE
 

exercises/move_semantics/move_semantics3.rs

@@ -1,7 +1,10 @@
 // move_semantics3.rs
-// Make me compile without adding new lines-- just changing existing lines!
-// (no lines with multiple semicolons necessary!)
-// Execute `rustlings hint move_semantics3` or use the `hint` watch subcommand for a hint.
+//
+// Make me compile without adding new lines-- just changing existing lines! (no
+// lines with multiple semicolons necessary!)
+//
+// Execute `rustlings hint move_semantics3` or use the `hint` watch subcommand
+// for a hint.
 
 // I AM NOT DONE
 

exercises/move_semantics/move_semantics4.rs

@@ -1,8 +1,11 @@
 // move_semantics4.rs
-// Refactor this code so that instead of passing `vec0` into the `fill_vec` function,
-// the Vector gets created in the function itself and passed back to the main
-// function.
-// Execute `rustlings hint move_semantics4` or use the `hint` watch subcommand for a hint.
+//
+// Refactor this code so that instead of passing `vec0` into the `fill_vec`
+// function, the Vector gets created in the function itself and passed back to
+// the main function.
+//
+// Execute `rustlings hint move_semantics4` or use the `hint` watch subcommand
+// for a hint.
 
 // I AM NOT DONE
 

exercises/move_semantics/move_semantics5.rs

@@ -1,7 +1,10 @@
 // move_semantics5.rs
-// Make me compile only by reordering the lines in `main()`, but without
-// adding, changing or removing any of them.
-// Execute `rustlings hint move_semantics5` or use the `hint` watch subcommand for a hint.
+//
+// Make me compile only by reordering the lines in `main()`, but without adding,
+// changing or removing any of them.
+//
+// Execute `rustlings hint move_semantics5` or use the `hint` watch subcommand
+// for a hint.
 
 // I AM NOT DONE
 

exercises/move_semantics/move_semantics6.rs

@@ -1,6 +1,9 @@
 // move_semantics6.rs
-// Execute `rustlings hint move_semantics6` or use the `hint` watch subcommand for a hint.
+//
 // You can't change anything except adding or removing references.
+//
+// Execute `rustlings hint move_semantics6` or use the `hint` watch subcommand
+// for a hint.
 
 // I AM NOT DONE
 

exercises/options/options1.rs

@@ -1,5 +1,7 @@
 // options1.rs
-// Execute `rustlings hint options1` or use the `hint` watch subcommand for a hint.
+//
+// Execute `rustlings hint options1` or use the `hint` watch subcommand for a
+// hint.
 
 // I AM NOT DONE
 
@@ -7,8 +9,9 @@
 // If it's before 10PM, there's 5 pieces left. At 10PM, someone eats them
 // all, so there'll be no more left :(
 fn maybe_icecream(time_of_day: u16) -> Option<u16> {
-    // We use the 24-hour system here, so 10PM is a value of 22 and 12AM is a value of 0
-    // The Option output should gracefully handle cases where time_of_day > 23.
+    // We use the 24-hour system here, so 10PM is a value of 22 and 12AM is a
+    // value of 0 The Option output should gracefully handle cases where
+    // time_of_day > 23.
     // TODO: Complete the function body - remember to return an Option!
     ???
 }
@@ -28,7 +31,8 @@ mod tests {
 
     #[test]
     fn raw_value() {
-        // TODO: Fix this test. How do you get at the value contained in the Option?
+        // TODO: Fix this test. How do you get at the value contained in the
+        // Option?
         let icecreams = maybe_icecream(12);
         assert_eq!(icecreams, 5);
     }

exercises/options/options2.rs

@@ -1,5 +1,7 @@
 // options2.rs
-// Execute `rustlings hint options2` or use the `hint` watch subcommand for a hint.
+//
+// Execute `rustlings hint options2` or use the `hint` watch subcommand for a
+// hint.
 
 // I AM NOT DONE
 
@@ -27,8 +29,9 @@ mod tests {
 
         let mut cursor = range;
 
-        // 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
+        // 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, cursor);
             cursor -= 1;

exercises/options/options3.rs

@@ -1,5 +1,7 @@
 // options3.rs
-// Execute `rustlings hint options3` or use the `hint` watch subcommand for a hint.
+//
+// Execute `rustlings hint options3` or use the `hint` watch subcommand for a
+// hint.
 
 // I AM NOT DONE
 

exercises/primitive_types/primitive_types1.rs

@@ -1,6 +1,10 @@
 // primitive_types1.rs
-// Fill in the rest of the line that has code missing!
-// No hints, there's no tricks, just get used to typing these :)
+//
+// Fill in the rest of the line that has code missing! No hints, there's no
+// tricks, just get used to typing these :)
+//
+// Execute `rustlings hint primitive_types1` or use the `hint` watch subcommand
+// for a hint.
 
 // I AM NOT DONE
 

exercises/primitive_types/primitive_types2.rs

@@ -1,6 +1,10 @@
 // primitive_types2.rs
-// Fill in the rest of the line that has code missing!
-// No hints, there's no tricks, just get used to typing these :)
+//
+// Fill in the rest of the line that has code missing! No hints, there's no
+// tricks, just get used to typing these :)
+//
+// Execute `rustlings hint primitive_types2` or use the `hint` watch subcommand
+// for a hint.
 
 // I AM NOT DONE
 

exercises/primitive_types/primitive_types3.rs

@@ -1,6 +1,9 @@
 // primitive_types3.rs
+//
 // Create an array with at least 100 elements in it where the ??? is.
-// Execute `rustlings hint primitive_types3` or use the `hint` watch subcommand for a hint.
+//
+// Execute `rustlings hint primitive_types3` or use the `hint` watch subcommand
+// for a hint.
 
 // I AM NOT DONE
 

exercises/primitive_types/primitive_types4.rs

@@ -1,6 +1,9 @@
 // primitive_types4.rs
+//
 // Get a slice out of Array a where the ??? is so that the test passes.
-// Execute `rustlings hint primitive_types4` or use the `hint` watch subcommand for a hint.
+//
+// Execute `rustlings hint primitive_types4` or use the `hint` watch subcommand
+// for a hint.
 
 // I AM NOT DONE
 

exercises/primitive_types/primitive_types5.rs

@@ -1,6 +1,9 @@
 // primitive_types5.rs
+//
 // Destructure the `cat` tuple so that the println will work.
-// Execute `rustlings hint primitive_types5` or use the `hint` watch subcommand for a hint.
+//
+// Execute `rustlings hint primitive_types5` or use the `hint` watch subcommand
+// for a hint.
 
 // I AM NOT DONE
 

exercises/primitive_types/primitive_types6.rs

@@ -1,7 +1,10 @@
 // primitive_types6.rs
-// Use a tuple index to access the second element of `numbers`.
-// You can put the expression for the second element where ??? is so that the test passes.
-// Execute `rustlings hint primitive_types6` or use the `hint` watch subcommand for a hint.
+//
+// Use a tuple index to access the second element of `numbers`. You can put the
+// expression for the second element where ??? is so that the test passes.
+//
+// Execute `rustlings hint primitive_types6` or use the `hint` watch subcommand
+// for a hint.
 
 // I AM NOT DONE
 

exercises/quiz1.rs

@@ -1,14 +1,17 @@
 // quiz1.rs
+//
 // This is a quiz for the following sections:
 // - Variables
 // - Functions
 // - If
-
+//
 // 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!
+// Write a function that calculates the price of an order of apples given the
+// quantity bought. No hints this time!
+//
+// No hints this time ;)
 
 // I AM NOT DONE
 

exercises/quiz2.rs

@@ -1,14 +1,15 @@
 // quiz2.rs
+//
 // This is a quiz for the following sections:
 // - Strings
 // - Vecs
 // - Move semantics
 // - Modules
 // - Enums
-
-// Let's build a little machine in the form of a function.
-// As input, we're going to give a list of strings and commands. These commands
-// determine what action is going to be applied to the string. It can either be:
+//
+// Let's build a little machine in the form of a function. As input, we're going
+// to give a list of strings and commands. These commands determine what action
+// is going to be applied to the string. It can either be:
 // - Uppercase the string
 // - Trim the string
 // - Append "bar" to the string a specified amount of times
@@ -16,6 +17,7 @@
 // - The input is going to be a Vector of a 2-length tuple,
 //   the first element is the string, the second one is the command.
 // - The output element is going to be a Vector of strings.
+//
 // No hints this time!
 
 // I AM NOT DONE

exercises/quiz3.rs

@@ -1,17 +1,19 @@
 // quiz3.rs
+//
 // This quiz tests:
 // - Generics
 // - Traits
-// An imaginary magical school has a new report card generation system written in Rust!
-// Currently the system only supports creating report cards where the student's grade
-// is represented numerically (e.g. 1.0 -> 5.5).
-// However, the school also issues alphabetical grades (A+ -> F-) and needs
-// to be able to print both types of report card!
-
+//
+// An imaginary magical school has a new report card generation system written
+// in Rust! Currently the system only supports creating report cards where the
+// student's grade is represented numerically (e.g. 1.0 -> 5.5). However, the
+// school also issues alphabetical grades (A+ -> F-) and needs to be able to
+// print both types of report card!
+//
 // Make the necessary code changes in the struct ReportCard and the impl block
-// to support alphabetical report cards. Change the Grade in the second test to "A+"
-// to show that your changes allow alphabetical grades.
-
+// to support alphabetical report cards. Change the Grade in the second test to
+// "A+" to show that your changes allow alphabetical grades.
+//
 // Execute `rustlings hint quiz3` or use the `hint` watch subcommand for a hint.
 
 // I AM NOT DONE

exercises/smart_pointers/arc1.rs

@@ -1,21 +1,24 @@
 // arc1.rs
-// In this exercise, we are given a Vec of u32 called "numbers" with values ranging
-// from 0 to 99 -- [ 0, 1, 2, ..., 98, 99 ]
-// We would like to use this set of numbers within 8 different threads simultaneously.
-// Each thread is going to get the sum of every eighth value, with an offset.
+//
+// In this exercise, we are given a Vec of u32 called "numbers" with values
+// ranging from 0 to 99 -- [ 0, 1, 2, ..., 98, 99 ] We would like to use this
+// set of numbers within 8 different threads simultaneously. Each thread is
+// going to get the sum of every eighth value, with an offset.
+//
 // The first thread (offset 0), will sum 0, 8, 16, ...
 // The second thread (offset 1), will sum 1, 9, 17, ...
 // The third thread (offset 2), will sum 2, 10, 18, ...
 // ...
 // The eighth thread (offset 7), will sum 7, 15, 23, ...
-
+//
 // Because we are using threads, our values need to be thread-safe.  Therefore,
 // we are using Arc.  We need to make a change in each of the two TODOs.
-
-
+//
 // Make this code compile by filling in a value for `shared_numbers` where the
 // first TODO comment is, and create an initial binding for `child_numbers`
-// where the second TODO comment is. Try not to create any copies of the `numbers` Vec!
+// where the second TODO comment is. Try not to create any copies of the
+// `numbers` Vec!
+//
 // Execute `rustlings hint arc1` or use the `hint` watch subcommand for a hint.
 
 // I AM NOT DONE

exercises/smart_pointers/box1.rs

@@ -1,13 +1,15 @@
 // box1.rs
 //
-// At compile time, Rust needs to know how much space a type takes up. This becomes problematic
-// for recursive types, where a value can have as part of itself another value of the same type.
-// To get around the issue, we can use a `Box` - a smart pointer used to store data on the heap,
-// which also allows us to wrap a recursive type.
+// At compile time, Rust needs to know how much space a type takes up. This
+// becomes problematic for recursive types, where a value can have as part of
+// itself another value of the same type. To get around the issue, we can use a
+// `Box` - a smart pointer used to store data on the heap, which also allows us
+// to wrap a recursive type.
 //
-// The recursive type we're implementing in this exercise is the `cons list` - a data structure
-// frequently found in functional programming languages. Each item in a cons list contains two
-// elements: the value of the current item and the next item. The last item is a value called `Nil`.
+// The recursive type we're implementing in this exercise is the `cons list` - a
+// data structure frequently found in functional programming languages. Each
+// item in a cons list contains two 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 `todo!()`

exercises/smart_pointers/cow1.rs

@@ -1,12 +1,16 @@
 // 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.
+//
+// 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.
 //
 // This exercise is meant to show you what to expect when passing data to Cow.
-// Fix the unit tests by checking for Cow::Owned(_) and Cow::Borrowed(_) at the TODO markers.
+// Fix the unit tests by checking for Cow::Owned(_) and Cow::Borrowed(_) at the
+// TODO markers.
+//
+// Execute `rustlings hint cow1` or use the `hint` watch subcommand for a hint.
 
 // I AM NOT DONE
 
@@ -50,10 +54,9 @@ mod tests {
 
     #[test]
     fn owned_no_mutation() -> Result<(), &'static str> {
-        // We can also pass `slice` without `&` so Cow owns it directly.
-        // In this case no mutation occurs and thus also no clone,
-        // but the result is still owned because it was never borrowed
-        // or mutated.
+        // We can also pass `slice` without `&` so Cow owns it directly. In this
+        // case no mutation occurs and thus also no clone, but the result is
+        // still owned because it was never borrowed or mutated.
         let slice = vec![0, 1, 2];
         let mut input = Cow::from(slice);
         match abs_all(&mut input) {
@@ -63,9 +66,9 @@ mod tests {
 
     #[test]
     fn owned_mutation() -> Result<(), &'static str> {
-        // Of course this is also the case if a mutation does occur.
-        // In this case the call to `to_mut()` returns a reference to
-        // the same data as before.
+        // Of course this is also the case if a mutation does occur. In this
+        // case the call to `to_mut()` returns a reference to the same data as
+        // before.
         let slice = vec![-1, 0, 1];
         let mut input = Cow::from(slice);
         match abs_all(&mut input) {

exercises/smart_pointers/rc1.rs

@@ -1,9 +1,14 @@
 // 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.
+//
+// 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.
+//
+// Execute `rustlings hint rc1` or use the `hint` watch subcommand for a hint.
 
 // I AM NOT DONE
 

exercises/strings/strings1.rs

@@ -1,6 +1,9 @@
 // strings1.rs
+//
 // Make me compile without changing the function signature!
-// Execute `rustlings hint strings1` or use the `hint` watch subcommand for a hint.
+//
+// Execute `rustlings hint strings1` or use the `hint` watch subcommand for a
+// hint.
 
 // I AM NOT DONE
 

exercises/strings/strings2.rs

@@ -1,6 +1,9 @@
 // strings2.rs
+//
 // Make me compile without changing the function signature!
-// Execute `rustlings hint strings2` or use the `hint` watch subcommand for a hint.
+//
+// Execute `rustlings hint strings2` or use the `hint` watch subcommand for a
+// hint.
 
 // I AM NOT DONE
 

exercises/strings/strings3.rs

@@ -1,5 +1,7 @@
 // strings3.rs
-// Execute `rustlings hint strings3` or use the `hint` watch subcommand for a hint.
+//
+// Execute `rustlings hint strings3` or use the `hint` watch subcommand for a
+// hint.
 
 // I AM NOT DONE
 

exercises/strings/strings4.rs

@@ -1,9 +1,10 @@
 // strings4.rs
-
+//
 // Ok, here are a bunch of values-- some are `String`s, some are `&str`s. Your
 // task is to call one of these two functions on each value depending on what
 // you think each value is. That is, add either `string_slice` or `string`
 // before the parentheses on each line. If you're right, it will compile!
+//
 // No hints this time!
 
 // I AM NOT DONE

exercises/structs/structs1.rs

@@ -1,6 +1,9 @@
 // structs1.rs
+//
 // Address all the TODOs to make the tests pass!
-// Execute `rustlings hint structs1` or use the `hint` watch subcommand for a hint.
+//
+// Execute `rustlings hint structs1` or use the `hint` watch subcommand for a
+// hint.
 
 // I AM NOT DONE
 

exercises/structs/structs2.rs

@@ -1,6 +1,9 @@
 // structs2.rs
+//
 // Address all the TODOs to make the tests pass!
-// Execute `rustlings hint structs2` or use the `hint` watch subcommand for a hint.
+//
+// Execute `rustlings hint structs2` or use the `hint` watch subcommand for a
+// hint.
 
 // I AM NOT DONE
 

exercises/structs/structs3.rs

@@ -1,8 +1,11 @@
 // structs3.rs
+//
 // Structs contain data, but can also have logic. In this exercise we have
 // defined the Package struct and we want to test some logic attached to it.
 // Make the code compile and the tests pass!
-// Execute `rustlings hint structs3` or use the `hint` watch subcommand for a hint.
+//
+// Execute `rustlings hint structs3` or use the `hint` watch subcommand for a
+// hint.
 
 // I AM NOT DONE
 

exercises/tests/tests1.rs

@@ -1,11 +1,14 @@
 // tests1.rs
-// Tests are important to ensure that your code does what you think it should do.
-// Tests can be run on this file with the following command:
-// rustlings run tests1
-
-// This test has a problem with it -- make the test compile! Make the test
-// pass! Make the test fail!
-// Execute `rustlings hint tests1` or use the `hint` watch subcommand for a hint.
+//
+// Tests are important to ensure that your code does what you think it should
+// do. Tests can be run on this file with the following command: rustlings run
+// tests1
+//
+// This test has a problem with it -- make the test compile! Make the test pass!
+// Make the test fail!
+//
+// Execute `rustlings hint tests1` or use the `hint` watch subcommand for a
+// hint.
 
 // I AM NOT DONE
 

exercises/tests/tests2.rs

@@ -1,7 +1,10 @@
 // tests2.rs
-// This test has a problem with it -- make the test compile! Make the test
-// pass! Make the test fail!
-// Execute `rustlings hint tests2` or use the `hint` watch subcommand for a hint.
+//
+// This test has a problem with it -- make the test compile! Make the test pass!
+// Make the test fail!
+//
+// Execute `rustlings hint tests2` or use the `hint` watch subcommand for a
+// hint.
 
 // I AM NOT DONE
 

exercises/tests/tests3.rs

@@ -1,8 +1,11 @@
 // tests3.rs
+//
 // This test isn't testing our function -- make it do that in such a way that
-// the test passes. Then write a second test that tests whether we get the result
-// we expect to get when we call `is_even(5)`.
-// Execute `rustlings hint tests3` or use the `hint` watch subcommand for a hint.
+// the test passes. Then write a second test that tests whether we get the
+// result we expect to get when we call `is_even(5)`.
+//
+// Execute `rustlings hint tests3` or use the `hint` watch subcommand for a
+// hint.
 
 // I AM NOT DONE
 

exercises/tests/tests4.rs

@@ -1,6 +1,9 @@
 // tests4.rs
+//
 // Make sure that we're testing for the correct conditions!
-// Execute `rustlings hint tests4` or use the `hint` watch subcommand for a hint.
+//
+// Execute `rustlings hint tests4` or use the `hint` watch subcommand for a
+// hint.
 
 // I AM NOT DONE
 

exercises/threads/threads1.rs

@@ -1,10 +1,12 @@
 // threads1.rs
-// Execute `rustlings hint threads1` or use the `hint` watch subcommand for a hint.
-
-// This program spawns multiple threads that each run for at least 250ms,
-// and each thread returns how much time they took to complete.
-// The program should wait until all the spawned threads have finished and
-// should collect their return values into a vector.
+//
+// This program spawns multiple threads that each run for at least 250ms, and
+// each thread returns how much time they took to complete. The program should
+// wait until all the spawned threads have finished and should collect their
+// return values into a vector.
+//
+// Execute `rustlings hint threads1` or use the `hint` watch subcommand for a
+// hint.
 
 // I AM NOT DONE
 

exercises/threads/threads2.rs

@@ -1,7 +1,11 @@
 // threads2.rs
-// Execute `rustlings hint threads2` or use the `hint` watch subcommand for a hint.
-// Building on the last exercise, we want all of the threads to complete their work but this time
-// the spawned threads need to be in charge of updating a shared value: JobStatus.jobs_completed
+//
+// Building on the last exercise, we want all of the threads to complete their
+// work but this time the spawned threads need to be in charge of updating a
+// shared value: JobStatus.jobs_completed
+//
+// Execute `rustlings hint threads2` or use the `hint` watch subcommand for a
+// hint.
 
 // I AM NOT DONE
 
@@ -27,8 +31,9 @@ fn main() {
     }
     for handle in handles {
         handle.join().unwrap();
-        // TODO: Print the value of the JobStatus.jobs_completed. Did you notice anything
-        // interesting in the output? Do you have to 'join' on all the handles?
+        // TODO: Print the value of the JobStatus.jobs_completed. Did you notice
+        // anything interesting in the output? Do you have to 'join' on all the
+        // handles?
         println!("jobs completed {}", ???);
     }
 }

exercises/threads/threads3.rs

@@ -1,5 +1,7 @@
 // threads3.rs
-// Execute `rustlings hint threads3` or use the `hint` watch subcommand for a hint.
+//
+// Execute `rustlings hint threads3` or use the `hint` watch subcommand for a
+// hint.
 
 // I AM NOT DONE
 

exercises/traits/traits1.rs

@@ -1,13 +1,11 @@
 // traits1.rs
-// Time to implement some traits!
 //
-// Your task is to implement the trait
-// `AppendBar` for the type `String`.
+// Time to implement some traits! Your task is to implement the trait
+// `AppendBar` for the type `String`. The trait AppendBar has only one function,
+// which appends "Bar" to any object implementing this trait.
 //
-// The trait AppendBar has only one function,
-// which appends "Bar" to any object
-// implementing this trait.
-// Execute `rustlings hint traits1` or use the `hint` watch subcommand for a hint.
+// Execute `rustlings hint traits1` or use the `hint` watch subcommand for a
+// hint.
 
 // I AM NOT DONE
 

exercises/traits/traits2.rs

@@ -1,14 +1,11 @@
 // traits2.rs
 //
-// Your task is to implement the trait
-// `AppendBar` for a vector of strings.
-//
-// To implement this trait, consider for
-// a moment what it means to 'append "Bar"'
+// Your task is to implement the trait `AppendBar` for a vector of strings. To
+// implement this trait, consider for a moment what it means to 'append "Bar"'
 // to a vector of strings.
 //
-// No boiler plate code this time,
-// you can do this!
+// No boiler plate code this time, you can do this!
+//
 // Execute `rustlings hint traits2` or use the `hint` watch subcommand for a hint.
 
 // I AM NOT DONE

exercises/traits/traits3.rs

@@ -1,11 +1,12 @@
 // traits3.rs
 //
-// Your task is to implement the Licensed trait for
-// both structures and have them return the same
-// information without writing the same function twice.
+// Your task is to implement the Licensed trait for both structures and have
+// them return the same information without writing the same function twice.
 //
 // Consider what you can add to the Licensed trait.
-// Execute `rustlings hint traits3` or use the `hint` watch subcommand for a hint.
+//
+// Execute `rustlings hint traits3` or use the `hint` watch subcommand for a
+// hint.
 
 // I AM NOT DONE
 

exercises/traits/traits4.rs

@@ -1,8 +1,11 @@
 // traits4.rs
 //
 // Your task is to replace the '??' sections so the code compiles.
+//
 // Don't change any line other than the marked one.
-// Execute `rustlings hint traits4` or use the `hint` watch subcommand for a hint.
+//
+// Execute `rustlings hint traits4` or use the `hint` watch subcommand for a
+// hint.
 
 // I AM NOT DONE
 

exercises/traits/traits5.rs

@@ -1,8 +1,11 @@
 // traits5.rs
 //
 // Your task is to replace the '??' sections so the code compiles.
+//
 // Don't change any line other than the marked one.
-// Execute `rustlings hint traits5` or use the `hint` watch subcommand for a hint.
+//
+// Execute `rustlings hint traits5` or use the `hint` watch subcommand for a
+// hint.
 
 // I AM NOT DONE
 

exercises/variables/variables1.rs

@@ -1,6 +1,9 @@
 // variables1.rs
+//
 // Make me compile!
-// Execute `rustlings hint variables1` or use the `hint` watch subcommand for a hint.
+//
+// Execute `rustlings hint variables1` or use the `hint` watch subcommand for a
+// hint.
 
 // I AM NOT DONE
 

exercises/variables/variables2.rs

@@ -1,5 +1,7 @@
 // variables2.rs
-// Execute `rustlings hint variables2` or use the `hint` watch subcommand for a hint.
+//
+// Execute `rustlings hint variables2` or use the `hint` watch subcommand for a
+// hint.
 
 // I AM NOT DONE
 

exercises/variables/variables3.rs

@@ -1,5 +1,7 @@
 // variables3.rs
-// Execute `rustlings hint variables3` or use the `hint` watch subcommand for a hint.
+//
+// Execute `rustlings hint variables3` or use the `hint` watch subcommand for a
+// hint.
 
 // I AM NOT DONE
 

exercises/variables/variables4.rs

@@ -1,5 +1,7 @@
 // variables4.rs
-// Execute `rustlings hint variables4` or use the `hint` watch subcommand for a hint.
+//
+// Execute `rustlings hint variables4` or use the `hint` watch subcommand for a
+// hint.
 
 // I AM NOT DONE
 

exercises/variables/variables5.rs

@@ -1,5 +1,7 @@
 // variables5.rs
-// Execute `rustlings hint variables5` or use the `hint` watch subcommand for a hint.
+//
+// Execute `rustlings hint variables5` or use the `hint` watch subcommand for a
+// hint.
 
 // I AM NOT DONE
 

exercises/variables/variables6.rs

@@ -1,5 +1,7 @@
 // variables6.rs
-// Execute `rustlings hint variables6` or use the `hint` watch subcommand for a hint.
+//
+// Execute `rustlings hint variables6` or use the `hint` watch subcommand for a
+// hint.
 
 // I AM NOT DONE
 

exercises/vecs/vecs1.rs

@@ -1,7 +1,10 @@
 // vecs1.rs
-// Your task is to create a `Vec` which holds the exact same elements
-// as in the array `a`.
+//
+// Your task is to create a `Vec` which holds the exact same elements as in the
+// array `a`.
+//
 // Make me compile and pass the test!
+//
 // Execute `rustlings hint vecs1` or use the `hint` watch subcommand for a hint.
 
 // I AM NOT DONE

exercises/vecs/vecs2.rs

@@ -1,6 +1,7 @@
 // vecs2.rs
-// A Vec of even numbers is given. Your task is to complete the loop
-// so that each number in the Vec is multiplied by 2.
+//
+// A Vec of even numbers is given. Your task is to complete the loop so that
+// each number in the Vec is multiplied by 2.
 //
 // Make me pass the test!
 //