errors5 solution

Cargo.lock

@@ -113,9 +113,9 @@ checksum = "bef38d45163c2f1dde094a7dfd33ccf595c92905c8f8f4fdc18d06fb1037718a"
 
 [[package]]
 name = "bitflags"
-version = "2.5.0"
+version = "2.6.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "cf4b9d6a944f767f8e5e0db018570623c85f3d925ac718db4e06d0187adb21c1"
+checksum = "b048fb63fd8b5923fc5aa7b340d8e156aec7ec02f0c78fa8a6ddc2613f6f71de"
 
 [[package]]
 name = "bstr"
@@ -229,7 +229,7 @@ version = "0.27.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "f476fe445d41c9e991fd07515a6f463074b782242ccf4a5b7b1d1012e70824df"
 dependencies = [
- "bitflags 2.5.0",
+ "bitflags 2.6.0",
  "crossterm_winapi",
  "libc",
  "mio",
@@ -262,9 +262,9 @@ checksum = "fea41bba32d969b513997752735605054bc0dfa92b4c56bf1189f2e174be7a10"
 
 [[package]]
 name = "either"
-version = "1.12.0"
+version = "1.13.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "3dca9240753cf90908d7e4aac30f630662b02aebaa1b58a3cadabdb23385b58b"
+checksum = "60b1af1c220855b6ceac025d3f6ecdd2b7c4894bfe9cd9bda4fbb4bc7c0d4cf0"
 
 [[package]]
 name = "equivalent"
@@ -363,6 +363,15 @@ dependencies = [
  "either",
 ]
 
+[[package]]
+name = "itertools"
+version = "0.13.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "413ee7dfc52ee1a4949ceeb7dbc8a33f2d6c088194d9f922fb8318faf1f01186"
+dependencies = [
+ "either",
+]
+
 [[package]]
 name = "itoa"
 version = "1.0.11"
@@ -450,7 +459,7 @@ version = "6.1.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "6205bd8bb1e454ad2e27422015fb5e4f2bcc7e08fa8f27058670d208324a4d2d"
 dependencies = [
- "bitflags 2.5.0",
+ "bitflags 2.6.0",
  "crossbeam-channel",
  "filetime",
  "fsevent-sys",
@@ -559,9 +568,9 @@ dependencies = [
 
 [[package]]
 name = "proc-macro2"
-version = "1.0.85"
+version = "1.0.86"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "22244ce15aa966053a896d1accb3a6e68469b97c7f33f284b99f0d576879fc23"
+checksum = "5e719e8df665df0d1c8fbfd238015744736151d4445ec0836b8e628aae103b77"
 dependencies = [
  "unicode-ident",
 ]
@@ -577,19 +586,20 @@ dependencies = [
 
 [[package]]
 name = "ratatui"
-version = "0.26.3"
+version = "0.27.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "f44c9e68fd46eda15c646fbb85e1040b657a58cdc8c98db1d97a55930d991eef"
+checksum = "d16546c5b5962abf8ce6e2881e722b4e0ae3b6f1a08a26ae3573c55853ca68d3"
 dependencies = [
- "bitflags 2.5.0",
+ "bitflags 2.6.0",
  "cassowary",
  "compact_str",
  "crossterm",
- "itertools",
+ "itertools 0.13.0",
  "lru",
  "paste",
  "stability",
  "strum",
+ "strum_macros",
  "unicode-segmentation",
  "unicode-truncate",
  "unicode-width",
@@ -610,7 +620,7 @@ version = "0.5.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "c82cf8cff14456045f55ec4241383baeff27af886adb72ffb2162f99911de0fd"
 dependencies = [
- "bitflags 2.5.0",
+ "bitflags 2.6.0",
 ]
 
 [[package]]
@@ -719,9 +729,9 @@ dependencies = [
 
 [[package]]
 name = "serde_json"
-version = "1.0.117"
+version = "1.0.118"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "455182ea6142b14f93f4bc5320a2b31c1f266b66a4a5c858b013302a5d8cbfc3"
+checksum = "d947f6b3163d8857ea16c4fa0dd4840d52f3041039a85decd46867eb1abef2e4"
 dependencies = [
  "itoa",
  "ryu",
@@ -797,9 +807,9 @@ checksum = "7da8b5736845d9f2fcb837ea5d9e2628564b3b043a70948a3f0b778838c5fb4f"
 
 [[package]]
 name = "strum"
-version = "0.26.2"
+version = "0.26.3"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "5d8cec3501a5194c432b2b7976db6b7d10ec95c253208b45f83f7136aa985e29"
+checksum = "8fec0f0aef304996cf250b31b5a10dee7980c85da9d759361292b8bca5a18f06"
 dependencies = [
  "strum_macros",
 ]
@@ -819,9 +829,9 @@ dependencies = [
 
 [[package]]
 name = "syn"
-version = "2.0.66"
+version = "2.0.68"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "c42f3f41a2de00b01c0aaad383c5a45241efc8b2d1eda5661812fda5f3cdcff5"
+checksum = "901fa70d88b9d6c98022e23b4136f9f3e54e4662c3bc1bd1d84a42a9a0f0c1e9"
 dependencies = [
  "proc-macro2",
  "quote",
@@ -874,7 +884,7 @@ version = "1.0.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "5a5fbabedabe362c618c714dbefda9927b5afc8e2a8102f47f081089a9019226"
 dependencies = [
- "itertools",
+ "itertools 0.12.1",
  "unicode-width",
 ]
 

Cargo.toml

@@ -52,9 +52,9 @@ crossterm = "0.27.0"
 hashbrown = "0.14.5"
 notify-debouncer-mini = { version = "0.4.1", default-features = false }
 os_pipe = "1.2.0"
-ratatui = { version = "0.26.3", default-features = false, features = ["crossterm"] }
+ratatui = { version = "0.27.0", default-features = false, features = ["crossterm"] }
 rustlings-macros = { path = "rustlings-macros", version = "=6.0.0-beta.9" }
-serde_json = "1.0.117"
+serde_json = "1.0.118"
 serde.workspace = true
 toml_edit.workspace = true
 

exercises/12_options/options1.rs

@@ -1,12 +1,9 @@
 // This function returns how much icecream there is left in the fridge.
-// If it's before 10PM, there's 5 scoops left. At 10PM, someone eats it
-// 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.
-    // TODO: Complete the function body - remember to return an Option!
-    ???
+// If it's before 22:00 (24-hour system), then 5 scoops are left. At 22:00,
+// someone eats it all, so no icecream is left (value 0). Return `None` if
+// `hour_of_day` is higher than 23.
+fn maybe_icecream(hour_of_day: u16) -> Option<u16> {
+    // TODO: Complete the function body.
 }
 
 fn main() {
@@ -17,6 +14,14 @@ fn main() {
 mod tests {
     use super::*;
 
+    #[test]
+    fn raw_value() {
+        // TODO: Fix this test. How do you get the value contained in the
+        // Option?
+        let icecreams = maybe_icecream(12);
+        assert_eq!(icecreams, 5);
+    }
+
     #[test]
     fn check_icecream() {
         assert_eq!(maybe_icecream(0), Some(5));
@@ -24,14 +29,7 @@ mod tests {
         assert_eq!(maybe_icecream(18), Some(5));
         assert_eq!(maybe_icecream(22), Some(0));
         assert_eq!(maybe_icecream(23), Some(0));
+        assert_eq!(maybe_icecream(24), None);
         assert_eq!(maybe_icecream(25), None);
     }
-
-    #[test]
-    fn raw_value() {
-        // 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/12_options/options2.rs

@@ -9,7 +9,7 @@ mod tests {
         let target = "rustlings";
         let optional_target = Some(target);
 
-        // TODO: Make this an if let statement whose value is "Some" type
+        // TODO: Make this an if-let statement whose value is `Some`.
         word = optional_target {
             assert_eq!(word, target);
         }
@@ -20,15 +20,15 @@ mod tests {
         let range = 10;
         let mut optional_integers: Vec<Option<i8>> = vec![None];
 
-        for i in 1..(range + 1) {
+        for i in 1..=range {
             optional_integers.push(Some(i));
         }
 
         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 `Vec::pop()`
+        // adds another layer of `Option`. You can do nested pattern matching
+        // in if-let and while-let statements.
         integer = optional_integers.pop() {
             assert_eq!(integer, cursor);
             cursor -= 1;

exercises/12_options/options3.rs

@@ -1,14 +1,17 @@
+#[derive(Debug)]
 struct Point {
     x: i32,
     y: i32,
 }
 
 fn main() {
-    let y: Option<Point> = Some(Point { x: 100, y: 200 });
+    let optional_point = Some(Point { x: 100, y: 200 });
 
-    match y {
-        Some(p) => println!("Co-ordinates are {},{} ", p.x, p.y),
-        _ => panic!("no match!"),
+    // TODO: Fix the compiler error by adding something to this match statement.
+    match optional_point {
+        Some(p) => println!("Co-ordinates are {},{}", p.x, p.y),
+        _ => panic!("No match!"),
     }
-    y; // Fix without deleting this line.
+
+    println!("{optional_point:?}"); // Don't change this line.
 }

exercises/13_error_handling/errors1.rs

@@ -1,22 +1,22 @@
-// 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!
-
-fn main() {
-    // You can optionally experiment here.
-}
-
+// TODO: 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 returning `None`. Thankfully, Rust has a similar
+// construct to `Option` that can be used to express error conditions. Change
+// the function signature and body to return `Result<String, String>` instead
+// of `Option<String>`.
 fn generate_nametag_text(name: String) -> Option<String> {
     if name.is_empty() {
         // Empty names aren't allowed.
         None
     } else {
-        Some(format!("Hi! My name is {}", name))
+        Some(format!("Hi! My name is {name}"))
     }
 }
 
+fn main() {
+    // You can optionally experiment here.
+}
+
 #[cfg(test)]
 mod tests {
     use super::*;
@@ -24,17 +24,18 @@ mod tests {
     #[test]
     fn generates_nametag_text_for_a_nonempty_name() {
         assert_eq!(
-            generate_nametag_text("Beyoncé".into()),
-            Ok("Hi! My name is Beyoncé".into())
+            generate_nametag_text("Beyoncé".to_string()).as_deref(),
+            Ok("Hi! My name is Beyoncé"),
         );
     }
 
     #[test]
     fn explains_why_generating_nametag_text_fails() {
         assert_eq!(
-            generate_nametag_text("".into()),
-            // Don't change this line
-            Err("`name` was empty; it must be nonempty.".into())
+            generate_nametag_text(String::new())
+                .as_ref()
+                .map_err(|e| e.as_str()),
+            Err("Empty names aren't allowed"),
         );
     }
 }

exercises/13_error_handling/errors2.rs

@@ -2,16 +2,16 @@
 // 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 items. Since
-// the player typed in the quantity, though, we get it as a string-- and they
-// might have typed anything, not just numbers!
+// the player typed in the quantity, we get it as a string. 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
+// handling the success case properly either). What we want to do is: If we call
 // the `total_cost` 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.
+// will return a `ParseIntError`. 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
+// There are at least two ways to implement this that are both correct. But one
 // is a lot shorter!
 
 use std::num::ParseIntError;
@@ -19,6 +19,8 @@ use std::num::ParseIntError;
 fn total_cost(item_quantity: &str) -> Result<i32, ParseIntError> {
     let processing_fee = 1;
     let cost_per_item = 5;
+
+    // TODO: Handle the error case as described above.
     let qty = item_quantity.parse::<i32>();
 
     Ok(qty * cost_per_item + processing_fee)
@@ -31,6 +33,7 @@ fn main() {
 #[cfg(test)]
 mod tests {
     use super::*;
+    use std::num::IntErrorKind;
 
     #[test]
     fn item_quantity_is_a_valid_number() {
@@ -40,8 +43,8 @@ mod tests {
     #[test]
     fn item_quantity_is_an_invalid_number() {
         assert_eq!(
-            total_cost("beep boop").unwrap_err().to_string(),
-            "invalid digit found in string"
+            total_cost("beep boop").unwrap_err().kind(),
+            &IntErrorKind::InvalidDigit,
         );
     }
 }

exercises/13_error_handling/errors3.rs

@@ -4,6 +4,17 @@
 
 use std::num::ParseIntError;
 
+// Don't change this function.
+fn total_cost(item_quantity: &str) -> Result<i32, ParseIntError> {
+    let processing_fee = 1;
+    let cost_per_item = 5;
+    let qty = item_quantity.parse::<i32>()?;
+
+    Ok(qty * cost_per_item + processing_fee)
+}
+
+// TODO: Fix the compiler error by changing the signature and body of the
+// `main` function.
 fn main() {
     let mut tokens = 100;
     let pretend_user_input = "8";
@@ -14,14 +25,6 @@ fn main() {
         println!("You can't afford that many!");
     } else {
         tokens -= cost;
-        println!("You now have {} tokens.", tokens);
+        println!("You now have {tokens} tokens.");
     }
 }
-
-fn total_cost(item_quantity: &str) -> Result<i32, ParseIntError> {
-    let processing_fee = 1;
-    let cost_per_item = 5;
-    let qty = item_quantity.parse::<i32>()?;
-
-    Ok(qty * cost_per_item + processing_fee)
-}

exercises/13_error_handling/errors4.rs

@@ -1,16 +1,16 @@
-#[derive(PartialEq, Debug)]
-struct PositiveNonzeroInteger(u64);
-
 #[derive(PartialEq, Debug)]
 enum CreationError {
     Negative,
     Zero,
 }
 
+#[derive(PartialEq, Debug)]
+struct PositiveNonzeroInteger(u64);
+
 impl PositiveNonzeroInteger {
-    fn new(value: i64) -> Result<PositiveNonzeroInteger, CreationError> {
-        // Hmm... Why is this always returning an Ok value?
-        Ok(PositiveNonzeroInteger(value as u64))
+    fn new(value: i64) -> Result<Self, CreationError> {
+        // TODO: This function shouldn't always return an `Ok`.
+        Ok(Self(value as u64))
     }
 }
 
@@ -24,11 +24,14 @@ mod tests {
 
     #[test]
     fn test_creation() {
-        assert!(PositiveNonzeroInteger::new(10).is_ok());
         assert_eq!(
-            Err(CreationError::Negative),
-            PositiveNonzeroInteger::new(-10)
+            PositiveNonzeroInteger::new(10),
+            Ok(PositiveNonzeroInteger(10)),
         );
-        assert_eq!(Err(CreationError::Zero), PositiveNonzeroInteger::new(0));
+        assert_eq!(
+            PositiveNonzeroInteger::new(-10),
+            Err(CreationError::Negative),
+        );
+        assert_eq!(PositiveNonzeroInteger::new(0), Err(CreationError::Zero));
     }
 }

exercises/13_error_handling/errors5.rs

@@ -1,38 +1,18 @@
-// 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!
+// This exercise is an altered version of the `errors4` exercise. It 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.
 //
 // 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?
+// 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`.
 
-use std::error;
+use std::error::Error;
 use std::fmt;
-use std::num::ParseIntError;
-
-// TODO: update the return type of `main()` to make this compile.
-fn main() -> Result<(), Box<dyn ???>> {
-    let pretend_user_input = "42";
-    let x: i64 = pretend_user_input.parse()?;
-    println!("output={:?}", PositiveNonzeroInteger::new(x)?);
-    Ok(())
-}
-
-// Don't change anything below this line.
-
-#[derive(PartialEq, Debug)]
-struct PositiveNonzeroInteger(u64);
 
 #[derive(PartialEq, Debug)]
 enum CreationError {
@@ -40,17 +20,7 @@ enum CreationError {
     Zero,
 }
 
-impl PositiveNonzeroInteger {
-    fn new(value: i64) -> Result<PositiveNonzeroInteger, CreationError> {
-        match value {
-            x if x < 0 => Err(CreationError::Negative),
-            x if x == 0 => Err(CreationError::Zero),
-            x => Ok(PositiveNonzeroInteger(x as u64)),
-        }
-    }
-}
-
-// This is required so that `CreationError` can implement `error::Error`.
+// This is required so that `CreationError` can implement `Error`.
 impl fmt::Display for CreationError {
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
         let description = match *self {
@@ -61,4 +31,26 @@ impl fmt::Display for CreationError {
     }
 }
 
-impl error::Error for CreationError {}
+impl Error for CreationError {}
+
+#[derive(PartialEq, Debug)]
+struct PositiveNonzeroInteger(u64);
+
+impl PositiveNonzeroInteger {
+    fn new(value: i64) -> Result<PositiveNonzeroInteger, CreationError> {
+        match value {
+            0 => Err(CreationError::Zero),
+            x if x < 0 => Err(CreationError::Negative),
+            x => Ok(PositiveNonzeroInteger(x as u64)),
+        }
+    }
+}
+
+// TODO: Add the correct return type `Result<(), Box<dyn ???>>`. What can we
+// use to describe both errors? Is there a trait which both errors implement?
+fn main() {
+    let pretend_user_input = "42";
+    let x: i64 = pretend_user_input.parse()?;
+    println!("output={:?}", PositiveNonzeroInteger::new(x)?);
+    Ok(())
+}

rustlings-macros/info.toml

@@ -603,7 +603,7 @@ hint = """
 Options can have a `Some` value, with an inner value, or a `None` value,
 without an inner value.
 
-There's multiple ways to get at the inner value, you can use `unwrap`, or
+There are multiple ways to get at the inner value, you can use `unwrap`, or
 pattern match. Unwrapping is the easiest, but how do you do it safely so that
 it doesn't panic in your face later?"""
 
@@ -616,9 +616,9 @@ Check out:
 - https://doc.rust-lang.org/rust-by-example/flow_control/if_let.html
 - https://doc.rust-lang.org/rust-by-example/flow_control/while_let.html
 
-Remember that `Option`s can be stacked in `if let` and `while let`.
+Remember that `Option`s can be nested in if-let and while-let statements.
 
-For example: `Some(Some(variable)) = variable2`
+For example: `if let Some(Some(x)) = y`
 
 Also see `Option::flatten`
 """
@@ -631,7 +631,8 @@ hint = """
 The compiler says a partial move happened in the `match` statement. How can
 this be avoided? The compiler shows the correction needed.
 
-After making the correction as suggested by the compiler, do read:
+After making the correction as suggested by the compiler, read the related docs
+page:
 https://doc.rust-lang.org/std/keyword.ref.html"""
 
 # ERROR HANDLING
@@ -646,8 +647,8 @@ is that `generate_nametag_text` should return a `Result` instead of an `Option`.
 To make this change, you'll need to:
   - update the return type in the function signature to be a `Result<String,
     String>` that could be the variants `Ok(String)` and `Err(String)`
-  - change the body of the function to return `Ok(stuff)` where it currently
-    returns `Some(stuff)`
+  - change the body of the function to return `Ok(…)` where it currently
+    returns `Some(…)`
   - change the body of the function to return `Err(error message)` where it
     currently returns `None`"""
 
@@ -659,12 +660,11 @@ One way to handle this is using a `match` statement on
 `item_quantity.parse::<i32>()` where the cases are `Ok(something)` and
 `Err(something)`.
 
-This pattern is very common in Rust, though, so there's a `?` operator that
+This pattern is very common in Rust, though, so there's the `?` operator that
 does pretty much what you would make that match statement do for you!
 
-Take a look at this section of the 'Error Handling' chapter:
-https://doc.rust-lang.org/book/ch09-02-recoverable-errors-with-result.html#a-shortcut-for-propagating-errors-the--operator
-and give it a try!"""
+Take a look at this section of the "Error Handling" chapter:
+https://doc.rust-lang.org/book/ch09-02-recoverable-errors-with-result.html#a-shortcut-for-propagating-errors-the--operator"""
 
 [[exercises]]
 name = "errors3"
@@ -675,43 +675,40 @@ If other functions can return a `Result`, why shouldn't `main`? It's a fairly
 common convention to return something like `Result<(), ErrorType>` from your
 `main` function.
 
-The unit (`()`) type is there because nothing is really needed in terms of
-positive results."""
+The unit type `()` is there because nothing is really needed in terms of a
+positive result."""
 
 [[exercises]]
 name = "errors4"
 dir = "13_error_handling"
 hint = """
 `PositiveNonzeroInteger::new` is always creating a new instance and returning
-an `Ok` result.
-
-It should be doing some checking, returning an `Err` result if those checks
-fail, and only returning an `Ok` result if those checks determine that
-everything is... okay :)"""
+an `Ok` result. But it should be doing some checking, returning an `Err` if
+those checks fail, and only returning an `Ok` if those checks determine that
+everything is… okay :)"""
 
 [[exercises]]
 name = "errors5"
 dir = "13_error_handling"
 test = false
 hint = """
-There are two different possible `Result` types produced within `main()`, which
-are propagated using `?` operators. How do we declare a return type from
-`main()` that allows both?
+There are two different possible `Result` types produced within the `main`
+function, which are propagated using the `?` operators. How do we declare a
+return type for the `main` function that allows both?
 
 Under the hood, the `?` operator calls `From::from` on the error value to
-convert it to a boxed trait object, a `Box<dyn error::Error>`. This boxed trait
-object is polymorphic, and since all errors implement the `error::Error` trait,
-we can capture lots of different errors in one "Box" object.
+convert it to a boxed trait object, a `Box<dyn Error>`. This boxed trait object
+is polymorphic, and since all errors implement the `Error` trait, we can capture
+lots of different errors in one `Box` object.
 
-Check out this section of the book:
+Check out this section of The Book:
 https://doc.rust-lang.org/book/ch09-02-recoverable-errors-with-result.html#a-shortcut-for-propagating-errors-the--operator
 
 Read more about boxing errors:
 https://doc.rust-lang.org/stable/rust-by-example/error/multiple_error_types/boxing_errors.html
 
 Read more about using the `?` operator with boxed errors:
-https://doc.rust-lang.org/stable/rust-by-example/error/multiple_error_types/reenter_question_mark.html
-"""
+https://doc.rust-lang.org/stable/rust-by-example/error/multiple_error_types/reenter_question_mark.html"""
 
 [[exercises]]
 name = "errors6"

solutions/12_options/options1.rs

@@ -1 +1,38 @@
-// Solutions will be available before the stable release. Thank you for testing the beta version 🥰
+// This function returns how much icecream there is left in the fridge.
+// If it's before 22:00 (24-hour system), then 5 scoops are left. At 22:00,
+// someone eats it all, so no icecream is left (value 0). Return `None` if
+// `hour_of_day` is higher than 23.
+fn maybe_icecream(hour_of_day: u16) -> Option<u16> {
+    match hour_of_day {
+        0..22 => Some(5),
+        22..24 => Some(0),
+        _ => None,
+    }
+}
+
+fn main() {
+    // You can optionally experiment here.
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn raw_value() {
+        // Using `unwrap` is fine in a test.
+        let icecreams = maybe_icecream(12).unwrap();
+        assert_eq!(icecreams, 5);
+    }
+
+    #[test]
+    fn check_icecream() {
+        assert_eq!(maybe_icecream(0), Some(5));
+        assert_eq!(maybe_icecream(9), Some(5));
+        assert_eq!(maybe_icecream(18), Some(5));
+        assert_eq!(maybe_icecream(22), Some(0));
+        assert_eq!(maybe_icecream(23), Some(0));
+        assert_eq!(maybe_icecream(24), None);
+        assert_eq!(maybe_icecream(25), None);
+    }
+}

solutions/12_options/options2.rs

@@ -1 +1,37 @@
-// Solutions will be available before the stable release. Thank you for testing the beta version 🥰
+fn main() {
+    // You can optionally experiment here.
+}
+
+#[cfg(test)]
+mod tests {
+    #[test]
+    fn simple_option() {
+        let target = "rustlings";
+        let optional_target = Some(target);
+
+        // if-let
+        if let Some(word) = optional_target {
+            assert_eq!(word, target);
+        }
+    }
+
+    #[test]
+    fn layered_option() {
+        let range = 10;
+        let mut optional_integers: Vec<Option<i8>> = vec![None];
+
+        for i in 1..=range {
+            optional_integers.push(Some(i));
+        }
+
+        let mut cursor = range;
+
+        // while-let with nested pattern matching
+        while let Some(Some(integer)) = optional_integers.pop() {
+            assert_eq!(integer, cursor);
+            cursor -= 1;
+        }
+
+        assert_eq!(cursor, 0);
+    }
+}

solutions/12_options/options3.rs

@@ -1 +1,26 @@
-// Solutions will be available before the stable release. Thank you for testing the beta version 🥰
+#[derive(Debug)]
+struct Point {
+    x: i32,
+    y: i32,
+}
+
+fn main() {
+    let optional_point = Some(Point { x: 100, y: 200 });
+
+    // Solution 1: Matching over the `Option` (not `&Option`) but without moving
+    // out of the `Some` variant.
+    match optional_point {
+        Some(ref p) => println!("Co-ordinates are {},{}", p.x, p.y),
+        //   ^^^ added
+        _ => panic!("No match!"),
+    }
+
+    // Solution 2: Matching over a reference (`&Option`) by added `&` before
+    // `optional_point`.
+    match &optional_point {
+        Some(p) => println!("Co-ordinates are {},{}", p.x, p.y),
+        _ => panic!("No match!"),
+    }
+
+    println!("{optional_point:?}");
+}

solutions/13_error_handling/errors1.rs

@@ -1 +1,37 @@
-// Solutions will be available before the stable release. Thank you for testing the beta version 🥰
+fn generate_nametag_text(name: String) -> Result<String, String> {
+    //                                    ^^^^^^         ^^^^^^
+    if name.is_empty() {
+        // `Err(String)` instead of `None`.
+        Err("Empty names aren't allowed".to_string())
+    } else {
+        // `Ok` instead of `Some`.
+        Ok(format!("Hi! My name is {name}"))
+    }
+}
+
+fn main() {
+    // You can optionally experiment here.
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn generates_nametag_text_for_a_nonempty_name() {
+        assert_eq!(
+            generate_nametag_text("Beyoncé".to_string()).as_deref(),
+            Ok("Hi! My name is Beyoncé"),
+        );
+    }
+
+    #[test]
+    fn explains_why_generating_nametag_text_fails() {
+        assert_eq!(
+            generate_nametag_text(String::new())
+                .as_ref()
+                .map_err(|e| e.as_str()),
+            Err("Empty names aren't allowed"),
+        );
+    }
+}

solutions/13_error_handling/errors2.rs

@@ -1 +1,57 @@
-// Solutions will be available before the stable release. Thank you for testing the beta version 🥰
+// 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 items. Since
+// the player typed in the quantity, we get it as a string. 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 `total_cost` function on a string that is not a number, that function
+// will return a `ParseIntError`. 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!
+
+use std::num::ParseIntError;
+
+fn total_cost(item_quantity: &str) -> Result<i32, ParseIntError> {
+    let processing_fee = 1;
+    let cost_per_item = 5;
+
+    // Added `?` to propagate the error.
+    let qty = item_quantity.parse::<i32>()?;
+    //                                    ^ added
+
+    // Equivalent to this verbose version:
+    let qty = match item_quantity.parse::<i32>() {
+        Ok(v) => v,
+        Err(e) => return Err(e),
+    };
+
+    Ok(qty * cost_per_item + processing_fee)
+}
+
+fn main() {
+    // You can optionally experiment here.
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use std::num::IntErrorKind;
+
+    #[test]
+    fn item_quantity_is_a_valid_number() {
+        assert_eq!(total_cost("34"), Ok(171));
+    }
+
+    #[test]
+    fn item_quantity_is_an_invalid_number() {
+        assert_eq!(
+            total_cost("beep boop").unwrap_err().kind(),
+            &IntErrorKind::InvalidDigit,
+        );
+    }
+}

solutions/13_error_handling/errors3.rs

@@ -1 +1,32 @@
-// Solutions will be available before the stable release. Thank you for testing the beta version 🥰
+// 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?
+
+use std::num::ParseIntError;
+
+// Don't change this function.
+fn total_cost(item_quantity: &str) -> Result<i32, ParseIntError> {
+    let processing_fee = 1;
+    let cost_per_item = 5;
+    let qty = item_quantity.parse::<i32>()?;
+
+    Ok(qty * cost_per_item + processing_fee)
+}
+
+fn main() -> Result<(), ParseIntError> {
+    //    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^ added
+    let mut tokens = 100;
+    let pretend_user_input = "8";
+
+    let cost = total_cost(pretend_user_input)?;
+
+    if cost > tokens {
+        println!("You can't afford that many!");
+    } else {
+        tokens -= cost;
+        println!("You now have {tokens} tokens.");
+    }
+
+    // Added this line to return the `Ok` variant of the expected `Result`.
+    Ok(())
+}

solutions/13_error_handling/errors4.rs

@@ -1 +1,42 @@
-// Solutions will be available before the stable release. Thank you for testing the beta version 🥰
+#[derive(PartialEq, Debug)]
+enum CreationError {
+    Negative,
+    Zero,
+}
+
+#[derive(PartialEq, Debug)]
+struct PositiveNonzeroInteger(u64);
+
+impl PositiveNonzeroInteger {
+    fn new(value: i64) -> Result<Self, CreationError> {
+        if value == 0 {
+            Err(CreationError::Zero)
+        } else if value < 0 {
+            Err(CreationError::Negative)
+        } else {
+            Ok(Self(value as u64))
+        }
+    }
+}
+
+fn main() {
+    // You can optionally experiment here.
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_creation() {
+        assert_eq!(
+            PositiveNonzeroInteger::new(10),
+            Ok(PositiveNonzeroInteger(10)),
+        );
+        assert_eq!(
+            PositiveNonzeroInteger::new(-10),
+            Err(CreationError::Negative),
+        );
+        assert_eq!(PositiveNonzeroInteger::new(0), Err(CreationError::Zero));
+    }
+}

solutions/13_error_handling/errors5.rs

@@ -1 +1,54 @@
-// Solutions will be available before the stable release. Thank you for testing the beta version 🥰
+// This exercise is an altered version of the `errors4` exercise. It 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.
+//
+// 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`.
+
+use std::error::Error;
+use std::fmt;
+
+#[derive(PartialEq, Debug)]
+enum CreationError {
+    Negative,
+    Zero,
+}
+
+// This is required so that `CreationError` can implement `Error`.
+impl fmt::Display for CreationError {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        let description = match *self {
+            CreationError::Negative => "number is negative",
+            CreationError::Zero => "number is zero",
+        };
+        f.write_str(description)
+    }
+}
+
+impl Error for CreationError {}
+
+#[derive(PartialEq, Debug)]
+struct PositiveNonzeroInteger(u64);
+
+impl PositiveNonzeroInteger {
+    fn new(value: i64) -> Result<PositiveNonzeroInteger, CreationError> {
+        match value {
+            x if x < 0 => Err(CreationError::Negative),
+            0 => Err(CreationError::Zero),
+            x => Ok(PositiveNonzeroInteger(x as u64)),
+        }
+    }
+}
+
+fn main() -> Result<(), Box<dyn Error>> {
+    let pretend_user_input = "42";
+    let x: i64 = pretend_user_input.parse()?;
+    println!("output={:?}", PositiveNonzeroInteger::new(x)?);
+    Ok(())
+}